Patent Application
20210033106
This application claims benefit of priority to German Patent Application No. 10 2019 120 410.0, filed Jul. 29, 2019. The contents of this application are incorporated herein by reference.
The invention relates to a delivery device comprising a blower, which is embodied as a side channel blower or peripheral blower, for delivering a medium to be delivered. One preferred area of application is in motor vehicle manufacturing. The delivery device can for example be used as a secondary air pump for an exhaust gas system of a combustion engine and in particular for purging a filter or other storage medium for volatile fuel components.
In fuel supply systems of spark-ignition engines, vaporised fuel components are collected by means of filters and supplied to the combustion engine via the latter's suction region. Typically used filters include activated carbon filters (ACFs) which store volatile fuel components and thus clean the gases which escape when a tank is vented. In order for the filter effect to be maintained, the filter has to be purged and thus regenerated from time to time. This is achieved by reverse-flow purging. The purge gas is supplied to the combustion process of the combustion engine. Due to rising demands on environmental compatibility, the operating times during which reverse-flow purging of the filter loaded with volatile fuel components is expedient are becoming ever shorter. The combustion engine which serves as the drive motor of a vehicle is for example switched off when the vehicle is at a stop. It thus becomes all the more important that the operating states of the combustion engine which are suitable for supplying the volatile fuel components into the combustion process be used intensively for regenerating the filter, but disrupt fuel-mixing by the combustion engine as little as possible.
Radial blowers are currently used sporadically in purge gas systems to deliver the volatile fuel components, contained in the filter purge gas flow, into the suction region of the combustion engine. Radial blowers operate at very high working rotational speeds of up to 60,000 rpm, in order to achieve the pressures required for purging the filter. The high working rotational speed makes huge demands on an electric drive of the blower, the balancing quality of the impeller and the tolerances of the component parts. One disadvantage is the unfavourable acoustic properties of radial blowers, in particular their structure-borne noise problems due to imbalance which can only be controlled at great effort and/or expense. The structure-borne noise induced by imbalance increases by the second power of the rotational speed and is huge at the rotational speeds of 50,000 to 60,000 rpm which are required for radial blowers. The design effort and/or expense which has to be invested in acoustic decoupling when attaching the radial blower to a vehicle body is correspondingly large.
Side channel blowers and peripheral blowers are significantly more favourable in terms of their required working rotational speed for use in motor vehicles. They get by on rotational speeds of 20,000 rpm, so around a third of the rotational speed level required for radial blowers, in order to generate sufficiently high pressures for purging the filters. This substantially defuses the structure-borne noise problems due to imbalance. A purge gas pump based on the side channel principle can be attached in a relatively simple way at the point of installation in the vehicle, for example on the bodywork. Acoustic abnormalities in the interior space of the vehicle can be avoided using relatively simple acoustic decoupling measures.
One advantage and also disadvantage is the very steep “delivery pressure over delivery flow” delivery characteristic curve which is typical of side channel blowers and peripheral blowers. On the one hand, this enables high delivery pressures even at low working rotational speeds. In the overload range, however, i.e. to the left of the nominal point in the diagram of the delivery characteristic curve, the delivery pressure and power consumption of the blower rise to undesirably high values as throttling on the pressure side increases and by association the delivery flow decreases. This can also lead to an undesirably high build-up of pressure in the tank venting system. The dissipation in the blower which rises as the power consumption increases also causes the temperature of the purge gas to rise to an undesirably significant degree, which can become problematic given the highly inflammable fuel components (hydrocarbon mixtures) to be delivered.
The use of side channel blowers and peripheral blowers in purge gas systems is known in principle, for example from DE 197 09 903 A1 and DE 197 40 582 A1, each of which are incorporated by reference herein.
DE 10 2011 108 763 B4, incorporated by reference herein, discloses the use of a side channel blower as a secondary air pump for an exhaust gas system and proposes embodying the side channel blower as a dual-flux blower in order to reduce the power consumption. The reduced circumferential extent of the respective delivery channel which is associated with the dual-flux design establishes a delivery-pressure-over-delivery-flow characteristic curve which is flatter but still rises linearly up to zero delivery.
U.S. Pat. No. 3,280,752 B incorporated by reference herein, discloses a side channel pump comprising a side channel into which fins, acting as flow channelling elements, protrude. A flattening of the delivery-pressure-over-delivery-flow characteristic curve towards zero delivery is described for this blower. DE 21 21 280 A, incorporated by reference herein, proposes arranging one or more grooves in the side channel in order to achieve a similar effect.
US 2007/0160456 A1 incorporated by reference herein, takes a different tack. In a first example embodiment, side channel blowers known from this document comprise a rotor wheel comprising paddles which comprise local constrictions on their axial end-facing sides. A peripheral blower of a second example embodiment comprises a groove in the interrupter channel which separates the inlet from the outlet of the blower. In both example embodiments, a leakage via the interrupter channel and thus a flattening of the delivery-pressure-over-delivery-flow characteristic curve towards zero delivery is specifically established.
The known measures for achieving a flattened delivery-pressure-over-delivery-flow characteristic curve towards zero delivery are associated with a considerable design effort and/or expense. This applies in particular to arranging flow channelling fins, and to a lesser extent also in principle grooves, in the side channel or interrupter channel. Grooves in the interrupter channel, as also the constrictions on the end-facing sides of the paddles, have the additional disadvantage that a concentrated, high-energy fluid jet in the inlet region of the delivery channel forms at the groove exit or in the region of the constriction on the paddles, and this tangential fluid jet penetrates far into the delivery channel. The concentrated fluid jet disrupts the flow in the inlet region and delays the fanning of the rotational component of the fluid flow, required for energy transmission, in the delivery channel. It should be noted in this regard that energy transmission from the impeller to the fluid in the delivery channel only begins at a circumferential angular range of 60° to 80° downstream of the inlet and is shifted even further into the delivery channel by the fluid jet which escapes into the delivery channel from the interrupter channel.
An aspect of the invention is a delivery device comprising a blower for delivering a medium to be delivered, wherein the delivery device is suitable for operations varying between a minimum delivery requirement, in most cases a zero requirement, and a temporarily high delivery requirement.
A different or additional aspect is that of providing a delivery device which is suitable with regard to its production of structure-borne noise for use in motor vehicles, for example as a secondary air delivery device or in particular a purge gas delivery device.
Another different or additional object is that of providing a delivery device in which the delivery-pressure-over-delivery-flow characteristic curve is flattened and by association the power consumption is reduced using means which are simple in design.
An aspect of the invention accordingly relates to a delivery device for a medium to be delivered, in order for example to deliver secondary air for an exhaust gas system or in particular to purge a filter for volatile fuel components in the fuel supply system of a motor vehicle. The delivery device comprises a blower, which is embodied as a side channel blower or peripheral blower, for delivering the medium to be delivered. The blower comprises a housing and an impeller which can rotate in the housing about a rotational axis. The housing comprises an inlet and an outlet for the medium to be delivered, a delivery channel which extends in the circumferential direction and comprises a side channel, and an interrupter channel which extends in the circumferential direction for separating the inlet and the outlet. The inlet and the outlet emerge into the delivery channel. The impeller comprises paddles which, when the impeller is rotated, periodically pass through the delivery channel and the interrupter channel in order to deliver the medium to be delivered, which flows through the inlet into the delivery channel, by impulse transmission in the delivery channel, as is known in principle from side channel blowers and peripheral blowers, and expel it through the outlet at an increased pressure.
In accordance with an aspect of than invention, the delivery device is configured such that the delivery-pressure-over-delivery-flow characteristic curve of the blower flattens or as applicable even drops towards minimum delivery flow, i.e. a theoretical zero delivery, such as would occur if the outlet were completely closed.
At a constant rotational speed of the impeller, the delivery-pressure-over-delivery-flow characteristic curve is ascertained by varying a throttling of the blower on the pressure side. To this end, a flow resistance which is expediently a valve downstream of the delivery channel, expediently at or near the outlet of the blower, is altered from a minimum resistance up to a maximum resistance which can in particular correspond to a complete closure. The characteristic curve can be sub-divided into three ranges: an overload range, a nominal range and a full-load range. The nominal range extends around the nominal working point, or “nominal point” for short, of the blower. If, proceeding from the nominal range, the throttling on the pressure side is reduced, the blower operates in its full-load range. If, proceeding from the nominal range, the throttling on the pressure side is increased, the blower operates in its overload range. If, in a diagram of the characteristic curve, the delivery flow is plotted along the X-axis and the difference in delivery pressure between the blower outlet and the blower inlet is plotted along the Y-axis, the overload range extends from the left up to the nominal range, and the full-load range extends from the right up to the nominal range. If the throttling on the pressure side is increased, the blower passes from the full-load range through the nominal range, in particular the nominal point, as the throttling increases, and enters the overload range, wherein the delivery flow drops, while the difference between the inlet pressure and the outlet pressure rises.
In a preferred embodiment, the delivery device is configured, for example by configuring the design of the blower, such that the delivery-pressure-over-delivery-flow characteristic curve rises continuously up to and into the nominal range as the delivery flow decreases, and the pitch in the overload range, advantageously in the nominal range, decreases. Advantageously, the delivery-pressure-over-delivery-flow characteristic curve rises continuously up to at least the nominal point as the delivery flow decreases, and its pitch only decreases at the nominal point or only after it has passed through the nominal point as the throttling continues to increase and the delivery flow accordingly continues to decrease. The pitch of the characteristic curve can still be greater than zero throughout this flattened region of the characteristic curve or in one or more portions thereof. It is preferably smaller than 0.2 or smaller than 0.1 throughout the overload range, i.e. to the left of the nominal range or nominal point. The pitch can also turn negative as the throttling increases, such that the characteristic curve drops towards minimum delivery flow as the throttling increases.
While the use of side channel blowers and peripheral blowers as purge gas delivery devices is known in principle, such as for example from DE 197 09 903 A1 and DE 197 40 582 A1 mentioned at the beginning, the delivery device in accordance with an aspect of the invention is however particularly suitable for purging and by association regenerating filters for volatile fuel components, due to the flattening of its characteristic curve and by association its reduced power consumption at small delivery requirements, which includes a zero delivery requirement, since the blower can be operated at a reduced power consumption in operating phases of the engine in which no purge gas or only a very small proportion of purge gas is allowed to be mixed in with the fuel mixture. Side channel blowers and peripheral blowers exhibit significantly greater dynamics than radial blowers, since they typically operate at only around a third of the rotational speed of radial blowers. Due to its flattened characteristic curve, the blower of the delivery device in accordance with an aspect of the invention can be operated at higher rotational speeds than conventional side channel blowers and peripheral blowers in the lower rotational speed range in which it operates most of the time when used as a purge gas blower, such that it can be accelerated within a short space of time in the relatively short periods in which purge gas can be mixed in and a temporarily high delivery requirement accordingly exists. The blower of the delivery device in accordance with an aspect of the invention can thus be operated at a higher rotational speed than conventional side channel blowers and peripheral blowers when the requirement is low or zero and at a lower rotational speed than radial blowers when the delivery requirement is high. As viewed over its entire operating range, the spread of rotational speeds and consequently the response time in the event of a change in delivery requirement can be reduced.
In the lower rotational speed range (overload range), at zero delivery or only a small delivery, the impeller is operated at rotational speeds of less than 5,000 rpm or less than 3,000 rpm, for example at a rotational speed in the range of 1,000 to 2,000 rpm, in advantageous embodiments. In the upper rotational speed range (full-load range), at a large delivery requirement, it is operated at a rotational speed of advantageously at least 15,000 rpm and at most 25,000 rpm, preferably at a rotational speed of 20,000±2,000 rpm.
In order to flatten the delivery-pressure-over-delivery-flow characteristic curve, an aspect of the invention proposes several measures which can each be realised individually as alternatives to each other, or also together in different combinations.
In first embodiments, the blower exhibits a uniformly increased sealing gap between the channel walls of the interrupter channel and the paddle of the impeller which respectively passes through, over the circumferential length of the interrupter channel. The paddles and the interrupter channel form an axial sealing gap along the axially outer edge of the paddle on one or both end-facing sides of the respective paddle, and a radial sealing gap along the radially outer edge of the respective paddle, over the circumferential length and/or angular extent of the interrupter channel. The sealing gap, which is formed around a paddle which passes through the interrupter channel, extends from a base point of the respective paddle, along one axial edge of the paddle, then along the radially outer edge of the paddle and then along the other axial edge of the paddle up to the base point of the paddle on said other axial edge of the paddle.
The axial sealing gaps each exhibit an axial gap width, and the radial sealing gap exhibits a radial gap width. The axial gap width of one or also both of the axial sealing gaps can vary. If the axial gap width varies, it varies only monotonically over the length of the respective axial sealing gap in the radial direction, i.e. the respective axial sealing gap widens axially either from the radially inner side to the radially outer side or from the radially outer side to the radially inner side, but does not comprise any local projection, constriction or other type of recess. Preferably, each of the two axial sealing gaps exhibits a constant axial gap width over its entire length. The axial gap width of the two axial sealing gaps can be unequal or preferably equal. The overall sealing gap is preferably symmetrical in relation to the two axial sealing gaps. It also holds for the radial sealing gap that the latter's gap width, i.e. the radial gap width, is constant in preferred embodiments, but at any rate does not comprise any fin-shaped projections or groove-shaped recesses. The uniform increase in the sealing gap establishes a specific leakage via the interrupter channel towards the inlet region, wherein said leakage ensures that the delivery-pressure-over-delivery-flow characteristic curve flattens and as applicable instably drops towards minimum delivery flow and/or a theoretical zero delivery.
As discussed above, the sealing gap between the paddles and the channel walls of the interrupter channel is larger than would be required to ensure free movement of the impeller. The axial gap width on the left-hand end-facing side and/or right-hand end-facing side of the respective paddle and/or the radial gap width at the free radial end of the paddle can in particular correspond to at least a clearance fit between the paddle and the interrupter channel. Preferably, one or two of the gap widths and particularly preferably all three of the gap widths mentioned is/are each larger than would correspond to a clearance fit.
In relation to a maximum breadth of the paddles, the axial gap width of one or both of the axial sealing gaps and/or the radial gap width of the radial sealing gap can in particular measure at least 3% or at least 4% or at least 5% of the maximum paddle breadth, wherein the paddle breadth is measured parallel to the rotational axis of the impeller. In conventional side channel blowers and peripheral blowers from the automotive sector, the gap widths measure at most one or two tenths of a millimetre. In advantageous embodiments of the invention, the axial gap width of one or both of the axial sealing gaps and/or the radial gap width of the radial sealing gap measure(s) at least 3 (three) tenths of a millimetre or at least 4 (four) tenths of a millimetre or at least 5 (five) tenths of a millimetre. If the gap width varies over the length of the respective sealing gap, then the smallest gap width in the respective sealing gap advantageously measures at least 3 tenths of a millimetre or at least 4 tenths of a millimetre in such embodiments.
The uniform increase in the sealing gap can also be accurately characterised by the ratio between the area of the sealing gap and the effective area of the paddle. The area of the sealing gap is understood to be the area of the overall sealing gap projected into a longitudinal sectional plane of the rotor wheel in the rotational direction of the rotor wheel, wherein the rotational axis of the impeller extends in this longitudinal sectional plane. If the paddles are simply straight and extend exactly radially, the projection plane and the plane of the paddle coincide. If, however, the paddles point or invert obliquely with respect to the radial or are inclined roundly, this is not the case. Such paddles are as it were projected onto a planar paddle which points exactly radially. The effective area of the paddle is the area of the paddle over which the respective paddle acts on the medium to be delivered when the impeller is rotated in the rotational direction and thus generates an impulse in the rotational direction. The sealing gap extends over the entire outer edge of the paddle, providing the edge of the paddle surrounds the effective area of the paddle. If, for example, the respective paddle is inserted into a slot on the outer circumference of the impeller, the area of the paddle situated in the slot does not count as the effective area of the paddle. Similarly, the base point of the paddle is only understood to be a point on the area of the paddle directly on the outer circumference of the impeller. In advantageous embodiments, this ratio between the area of the sealing gap and the effective area of the paddle measures at least 0.06 or at least 0.07. For a good degree of effectiveness despite the specific leakage, the ratio between the area of the sealing gap and the effective area of the paddle advantageously measures at most 0.25 or at most 0.20.
As an alternative to or in addition to the ratios described above, the uniform increase in the sealing gap can be characterised by the ratio between the area of the sealing gap and the cross-sectional area of the interrupter channel which the paddles pass through when the impeller is rotated. In the longitudinal sectional plane mentioned above, the interrupter channel exhibits a free cross-sectional area which is limited laterally and on the radially outer side by the channel walls of the interrupter channel and on the radially inner side by a straight line which extends through the base point of the paddle on one axially outer edge of the paddle and through the base point of the paddle on the other axially outer edge of the paddle. The ratio between the area of the sealing gap and the cross-sectional area of the channel preferably measures at least 0.05 or at least 0.06. The ratio between the area of the sealing gap and the cross-sectional area of the channel can measure up to 0.20 or up to 0.15 and preferably up to at most 0.13.
Due to the uniform increase in the sealing gap in accordance with an aspect of the invention, the leakage flow flows in a uniform distribution along the edge of the paddle, advantageously in a uniform distribution over the entire free outer edge of the paddle, from the interrupter channel into the delivery channel. The leakage flow can for example be distributed around the paddles substantially in a U shape or a hemi-annular shape. A disruption to the flow in the upstream delivery portion of the delivery channel, near the inlet, is at least largely avoided. The formation of the rotational flow is even assisted, meaning that energy transmission begins significantly earlier. The delivery rate and the degree of effectiveness of the blower are significantly increased relative to a blower comprising a groove as the leakage path.
The “delivery pressure over delivery flow” delivery characteristic curve can also be flattened by means of a bypass which connects the high-pressure side of the blower to the low-pressure side of the blower by bypassing the interrupter channel, such that a leakage flow from the high-pressure side to the low-pressure side is established. The high-pressure side of the blower comprises a downstream portion of the delivery channel, whence it extends in the delivery direction via the outlet up to a closing and/or dosing member which succeeds the blower downstream or up to a consumer to which the medium to be delivered is supplied by means of the blower. The closing and/or dosing member can in particular be a dosing valve. The low-pressure side extends via the inlet up to and into the delivery channel and comprises an upstream portion of the delivery channel which adjoins the inlet in the delivery direction.
The bypass can be embodied as a passive bypass or as an active bypass or as applicable also as a hybrid form consisting of a passive and active bypass. If it is embodied as a passive bypass, the flow resistance of the bypass is established solely by the geometric configuration of the bypass, such that a leakage flow which is predetermined by means of the flow resistance ensures that the pressure characteristic curve flattens and preferably inverts. If it is embodied as an active bypass, a bypass valve is arranged in the bypass. When a threshold pressure predetermined by the bypass valve is exceeded, the bypass valve transitions abruptly, or continuously as the pressure continues to rise, from a state of minimum throughput to a state of maximum throughput.
The bypass can be realised in addition to or instead of the increased sealing gap.
In addition to or as an alternative to the increased sealing gap and/or the bypass, the “delivery pressure over delivery flow” delivery characteristic curve can be flattened by limiting the input power (shaft power). In this way, the delivery pressure can be limited in a desired operating range of the blower, preferably the overload range. It is for example possible to establish a delivery characteristic curve which assumes a maximum value at the nominal point and decreases steadily in the overload range. If the blower is driven by an electric motor, it is possible to limit the electric input power of the electric motor. In particular, the input current of the motor can be limited to a certain value, at a constant voltage. The hardware and/or software for limiting the electric input power can be installed and/or implemented within the delivery device or can be part of a controller placed elsewhere.
Another of the measures is to choose the paddle geometry. Several of the paddles and preferably all of the paddles can then comprise a convex rounded profile or an oblique chamfer, which extends in the circumferential direction, on at least one axially outer edge of the paddle and/or on the radially outer edge of the paddle. Alternatively or additionally, several of the paddles and preferably all of the paddles can comprise a radially outer edge of the paddle which in a plan view onto a front side of the respective paddle is convexly or concavely, for example roundly, arched radially inwards or radially outwards or is polygonal, for example trapezium-shaped, or rises monotonically from one end-facing side to the other. Alternatively or additionally, several of the paddles and preferably all of the paddles can comprise at least one paddle portion which points towards a rotational axis of the impeller in an axial view of the impeller at an inclination to a radial which extends through the respective paddle.
The “delivery pressure over delivery flow” characteristic curve can be flattened solely by the paddle geometry. In preferred embodiments, however, one or more of the measures relating to the paddle geometry is/are realised in combination with the measure of the increased sealing gap and/or the bypass and/or limiting the input power (shaft power).
Another measure is to embody the blower as a multi-flux, for example dual-flux blower. A multi-flux blower comprises a first delivery flux and a second delivery flux. The blower also comprises an outlet which is common to the two delivery fluxes or a first outlet for the first delivery flux and a second outlet for the second delivery flux, wherein the first outlet and the second outlet are connected to each other downstream of the respective delivery flux. The first and second delivery flux can differ from each other in their delivery-pressure-over-delivery-flow characteristic curve and thus in their delivery rate. The delivery fluxes are short-circuited via the outlet or the connected outlets. If they differ in their delivery rate, a backflow from the delivery flux having a greater delivery rate (the main flux or first flux) into the delivery flux having a lower delivery rate (the regulating flux or second flux) via the common outlet or the connected outlets occurs at least in certain operating states, preferably in the overload range. They preferably also comprise a common inlet or a first inlet for the first delivery flux and a second inlet for the second delivery flux, wherein the first inlet and the second inlet are connected to each other upstream of the respective delivery flux. In such embodiments, the delivery fluxes are connected in parallel. The fluxes can in particular be short-circuited or connected in parallel in or on the housing of the blower.
In a first variant of the multi-flux blower, a multi-flux impeller is used, preferably a dual-flux impeller comprising a left-hand delivery flux (the first flux) on one end-facing side of the impeller and a right-hand delivery flux (the second flux) on the other end-facing side of the impeller. The two delivery fluxes are separated from each other. They can be fluidically separated by a separating stay of the impeller which encircles the outer circumference of the impeller or by a separating stay of the housing which encircles the inner circumference of the housing. The separating stay extends axially between the left-hand delivery flux and the right-hand delivery flux. The delivery fluxes can comprise a common inlet which expediently emerges on the inner circumference of the housing which surrounds the impeller. Instead, however, they can also each comprise an assigned inlet, i.e. a left-hand inlet on a left-hand channel end-facing wall of the housing which faces the left-hand delivery flux and a right-hand inlet on a right-hand channel end-facing wall of the housing which faces the right-hand delivery flux. The left-hand inlet and the right-hand inlet can be connected to each other upstream of the delivery channel, i.e. a common supply can bifurcate to form the left-hand inlet and the right-hand inlet. The delivery fluxes can comprise a common outlet which expediently emerges on the inner circumference of the housing which surrounds the impeller. Instead, however, they can also each comprise an assigned outlet, i.e. a left-hand outlet on a left-hand channel end-facing wall of the housing which faces the left-hand delivery flux and a right-hand outlet on a right-hand channel end-facing wall of the housing which faces the right-hand delivery flux. The left-hand outlet and the right-hand outlet can be connected to each other downstream of the delivery channel, i.e. can converge to form a common drainage.
The left-hand delivery flux and the right-hand delivery flux can be embodied differently, by differentiating the paddle geometry and/or the channel geometry, i.e. the geometry of the delivery channel and/or the interrupter channel, on the left and on the right. In such variants, the left-hand delivery flux and the right-hand delivery flux differ in their delivery rate. In particular, one flux can generate a greater build-up of pressure than the other flux. The paddles of one flux can then for example be larger than the paddles of the other flux. One of the fluxes can comprise more paddles than the other. The delivery channel of one flux can be shaped differently in the longitudinal section of the blower and/or can be larger than the delivery channel of the other flux. The interrupter channel of one flux can be shaped differently in the longitudinal section of the blower and/or can be larger than the interrupter channel of the other flux. Other measures, for example disruptive geometries, for reducing the delivery rate can be implemented in one of the two delivery channels. The aim is to internally achieve a change in delivery in one of the two delivery fluxes with increasing throttling on the pressure side beyond a defined working state of the blower. In the region of the characteristic curve exhibiting an effective difference in pressure between the two fluxes, the delivery flux having a higher delivery rate flows through the delivery flux having a lower delivery rate, counter to the rotational direction of the impeller. A backflow from the delivery flux having a higher delivery rate into the delivery flux having a lower delivery rate occurs via the common outlet or the connected outlets. This causes the build-up of pressure to drop and the “delivery pressure over delivery flow” delivery characteristic curve to flatten, and preferably invert, in a defined way.
In a second variant of the multi-flux blower, the blower comprises a main flux (the first delivery flux) and additionally a regulating flux (the second delivery flux). The main flux and the regulating flux are formed in the housing of the blower. The impeller is part of the main flux. The regulating flux is embodied to be smaller than the main flux.
The impeller can comprise an additional paddle ring with which it forms the regulating flux. Alternatively, the regulating flux can comprise an additional impeller comprising paddles, wherein the additional impeller can be arranged alongside the impeller of the main flux on the same shaft. If the additional paddle ring is arranged on the impeller of the main flux, said impeller can comprise the paddle ring of the regulating flux, axially level and radially within the paddle ring of the main flux or axially offset with respect to the paddle ring of the main flux, on an outer circumference, for example an outer circumference having a smaller diameter.
As described further above with respect to the first variant, the main flux and the regulating flux can comprise a common inlet. Instead, however, they can also each comprise an assigned inlet, i.e. one inlet for the main flux and another inlet for the regulating flux. The inlet of the main flux and the inlet of the regulating flux can be connected to each other upstream of the delivery channel, i.e. a common supply can bifurcate to form the inlet of the main flux and the inlet of the regulating flux. The main flux and the regulating flux can comprise a common outlet. Instead, however, they can also each comprise an assigned outlet, i.e. one outlet for the main flux and one outlet for the regulating flux, wherein the outlet of the main flux and the outlet of the regulating flux can be connected to each other downstream of the respective delivery channel, i.e. can converge to form a common drainage.
The regulating flux is characterised by a flatter profile of its “delivery pressure over delivery flow” characteristic curve than the main flux. In a region of the characteristic curve around the nominal point, a change in delivery occurs and the regulating flux is circulated counter to the rotational direction. Beyond a certain delivery pressure corresponding to said change, the regulating flux acts as a bypass and causes the “delivery pressure over delivery flow” characteristic curve of the main flux to be flattened, and preferably inverted, in a defined way.
In a third variant of the multi-flux blower, a first delivery channel (the first flux) and a second delivery channel (the second delivery flux) are arranged one behind the other in the circumferential direction in the housing of the blower, and the impeller passes through them one after the other. A first delivery flux is obtained via the angular extent of the first delivery channel, and a second delivery flux is obtained via the angular extent of the second delivery channel. The delivery fluxes differ in terms of their delivery rate. For this purpose, the delivery channels can in particular be different. One of the delivery channels can thus extend around the rotational axis over a greater angle than the other, and/or one of the delivery channels can have a larger cross-section than the other, and/or one or more measures for reducing the delivery rate can be implemented in one of the delivery channels.
The delivery channels arranged one behind the other are short-circuited in relation to the outlet. They are preferably connected in parallel. The delivery channels arranged one behind the other either comprise a common outlet or instead each comprise an assigned outlet, i.e. a first outlet for the first delivery channel and a second outlet for the second delivery channel. If they comprise the first outlet and the second outlet, the latter are connected to each other downstream of the respective delivery channel, i.e. they converge to form a common drainage. In the variant comprising delivery channels arranged one behind the other and, correspondingly, delivery fluxes arranged one behind the other, a backflow into the delivery channel having the lower delivery rate again occurs via the outlet, and consequently the “delivery pressure over delivery flow” characteristic curve is flattened, and preferably inverted, in a defined way. If connected in parallel, the delivery channels arranged one behind the other either comprise a common inlet or each comprise an assigned inlet, i.e. a first inlet for the first delivery channel and a second inlet for the second delivery channel. If they comprise the first inlet and the second inlet, the latter are connected to each other upstream of the delivery channels, i.e. a common supply bifurcates to form the first inlet and the second inlet.
In an advantageous embodiment, the delivery device comprises a dosing valve and a controller or regulator which is configured to control and/or regulate the blower, in particular the impeller, in terms of its rotational speed and the dosing valve in terms of its valve state, i.e. in terms of its throughput. The dosing valve can be switched between a state of minimum throughput, which is preferably a closed state, and a state of maximum throughput. In a first variant, the valve can be switched between discrete switched states, i.e. it is a switching valve. In a second variant, it is embodied as a proportional valve and allows a steady, continuous alteration of the valve opening which governs the throughput. The dosing valve can in particular be an electromagnetic switching valve or proportional valve, for example a pulse-width-modulated valve. The pulse-width-modulated dosing valve can for example be operated at a clock frequency of at least 5 Hz or at least 10 Hz. Clock frequencies in the range of 8 to 12 Hz, for example 10 Hz, are preferred.
The controller or regulator can be configured to set the dosing valve to a state of large throughput, expediently a state of maximum throughput, when the requirement for medium to be delivered is high and to control and/or regulate the delivery flow by varying the rotational speed of the blower in the upper rotational speed range of for example 15,000 to 25,000 rpm and to operate the blower in the lower rotational speed range of for example at most 5,000 or at most 3,000 rpm when the requirement is low, preferably at an at least substantially constant rotational speed in the lower rotational speed range, and to set the delivery rate by varying the valve state. For rapid acceleration when demand rises, the blower is advantageously not brought to a stop in its low-requirement operating state but rather operated at a rotational speed of at least 300 rpm or at least 500 rpm. If the delivery rate is set by means of the dosing valve, the difference in pressure as measured across the dosing valve in a closed valve state is advantageously small. In advantageous embodiments, the blower is operated in this operating state at a rotational speed which ensures that said difference in pressure on the dosing valve measures at most 0.5 bars or at most 0.3 bars or at most 0.2 bars.
The principle of changing between “fulfilling the delivery requirement by varying the rotational speed of the blower in the upper rotational speed range according to requirement, with the dosing valve open” when the delivery requirement is large and “fulfilling the delivery requirement by varying the valve state and operating the blower in the lower rotational speed range” when the delivery requirement is low can be combined with any of the other measures disclosed herein. The principle is however also advantageous in its own right, without flattening the “delivery pressure over delivery flow” characteristic curve as claimed herein. The Applicant therefore reserves the right to direct an independent application to this, even without Feature 1.3 of claim 1.
Features of the invention are also described in the aspects formulated below. The aspects are worded in the manner of claims and can substitute for them. Features disclosed in the aspects can also supplement and/or qualify the claims as well as the measures described above, indicate alternatives with respect to individual features and/or broaden claim features. Bracketed reference signs refer to example embodiments of the invention which are illustrated below in figures. They do not restrict the features described in the aspects to their literal sense as such, but do conversely indicate preferred ways of realising the respective feature.
Example embodiments of the invention are described below on the basis of figures. Features disclosed by the example embodiments, each individually and in any combination of features, advantageously develop the subject-matter of the claims and aspects as well as the embodiments described above. There is shown:
The blower B is connected to the tank 100 via a venting conduit 101 and to the filter 103 via a regenerating conduit 102 which branches off from the venting conduit 101. The filter 103 can in particular be an activated carbon filter. A shut-off safety valve 105 is arranged in the venting conduit 101, downstream of the junction to the filter 103 and upstream of the blower B in relation to the delivery direction towards the combustion engine 110. When an emergency is detected, for example in the event of a vehicular crash, the shut-off safety valve 105 closes the venting conduit 101 and therefore separates the tank 100 and the filter 103 from the blower B and in particular from the suction region 107 of the combustion engine 110.
The filter 103 is connected to the outer environment via a shut-off valve 104. In purge operations, i.e. when the purge gas is delivered towards the combustion engine 110 and when the combustion engine 110 is switched off, the shut-off valve 104 is open in order to enable pressure equalisation with the atmosphere. The shut-off valve 104 is closed when a leakage test is being performed on the tank 100.
The venting conduit 101 leads from the blower B into the suction region 107. The venting conduit 101 can in particular emerge into the suction region 107, which is typically a suction pipe, upstream of a throttle member 108, which is typically a throttle valve. An air filter 109 for the fresh air suctioned by the combustion engine 110 can be arranged in the suction region 107, upstream of the convergence point for the purge gas. A supercharger 111 can be arranged between the convergence point for the purge gas and the throttle member 108.
A dosing valve 106 is arranged in the venting conduit 101, downstream of the blower B and at or upstream of the convergence point into the suction region 107 in the flow direction towards the combustion engine 110. The dosing valve 106 can in particular be formed as an electric dosing valve and preferably as a pulse-width-modulated dosing valve. The dosing valve 106 can be a switching valve, which can be switched between discrete switched states, or a proportional valve.
The blower B is driven by an electric motor. The delivery device comprises a controller or regulator 113 for controlling or regulating the drive motor of the blower B and dosing valve 106. The controller or regulator 113 can optionally also control the shut-off valve 104 and/or the shut-off safety valve 105. The controller or regulator 113 is configured to control or regulate the electric motor of the blower B in terms of its rotational speed and optionally in terms of its rotational direction. The controller or regulator 113 is also configured to control or regulate the dosing valve 106. It controls or regulates in accordance with the operating state of the combustion engine 110 and/or the loaded state of the filter 103. In advantageous embodiments, the blower B is controlled or regulated at least in terms of its rotational speed in accordance with a control signal which is representative of the respective operating state of the combustion engine 110.
The controller or regulator 113 can be arranged in or on a housing of the blower B. It can however instead also be arranged separately from the blower B and connected to the electric motor by a wire connection or also, as applicable, wirelessly. If the combustion engine 110 is the internal combustion engine of a motor vehicle, the controller or regulator 113 can be connected to a superordinate engine controller or can be an integrated part of said engine controller.
The controller or regulator 113 can be configured to keep the rotational speed of the blower B low, for example in the range of 1,000 to 3,000 rpm, when there is no purge requirement or only a low purge requirement in terms of the loaded state of the filter 103 and/or when the combustion engine 110 is currently in an operating state which is unfavourable for supplying purge gas. The controller or regulator 113 can alternatively or preferably additionally be configured to increase the rotational speed of the blower B and operate the blower B in the upper rotational speed range of for example 15,000 to 25,000 rpm or 15,000 to 20,000 rpm when there is a large purge requirement due to a highly loaded state of the filter 103 and/or when the combustion engine 110 is in an operating state which is suitable for supplying purge gas.
The controller or regulator 113 is advantageously configured to control and/or regulate the supply of purge gas by altering the rotational speed of the blower B, preferably in the upper rotational speed range, when the purge requirement is high and/or in an operating state of the combustion engine 110 which is favourable for supplying purge gas. In order to set the purge gas flow when the purge requirement is low and/or in operating states of the combustion engine 110 which are unfavourable, the controller or regulator 113 can be configured to control or regulate the supply of purge gas up to and including zero delivery by means of the dosing valve 106 while the blower B is operated in the lower rotational speed range, for example in a rotational speed range of 1,000 to 3,000 rpm. The controller or regulator 113 can then be configured to drive the blower B at a constant, low rotational speed of less than 5,000 rpm or less than 3,000 rpm and to control or regulate the supply of purge gas solely by means of the dosing valve 106 when the purge requirement is low and/or in an operating state of the combustion engine 110 which is unfavourable for purging. Additionally or instead, the dosing valve 106 can be fully opened, and the purge gas can be supplied solely by controlling or regulating the rotational speed of the blower B, when the purge requirement is high and/or in an operating state of the combustion engine 110 which is favourable for purging.
Where the rotational speed of the blower B is mentioned, this is understood to mean the rotational speed of an impeller of the blower B. If the blower B comprises several impellers, the above statements regarding the controlling and/or regulating principle apply to the rotational speed of each of the impellers.
The delivery device can comprise a sensor 112 which can in particular be arranged in the venting conduit 101 between the blower B and the suction region 107, preferably between the blower B and the dosing valve 106, in order to measure the mass flow or volume flow or pressure or temperature of the purge gas at said point and to supply said measurement value to the controller or regulator 113. The controller or regulator 113 is embodied as a regulator in such embodiments. It can be connected to a superordinate controller, for example an engine controller, or can be part of said superordinate controller. The controller or regulator 113 can receive a guiding variable as a nominal value and the output signal of the sensor 112 as an actual value from the superordinate controller, in accordance with the operating state and/or load state of the combustion engine 110. When developed into a regulator, the controller or regulator 113 can be configured to regulate the blower B and/or the dosing valve 106 in accordance with the nominal value and the actual value. To this end, it performs a nominal/actual comparison, for example by finding the difference between the nominal value and the actual value, and regulates the blower B and/or the valve 106 using an actuating variable for the blower B, formed as a function of the nominal/actual comparison, and/or an actuating variable for the dosing valve 106, formed as a function of the nominal/actual comparison, in accordance with the previously described dividing regime between the blower B and the dosing valve 106.
The dosing valve 106 can be arranged separately from the blower B, away from the blower B or on a housing of the blower B, for example directly at the outlet, or in the housing of the blower B. The shut-off safety valve 105 can be arranged separately from the blower B, away from the blower B or on the housing of the blower B, for example directly at the inlet, or in the housing of the blower B. The sensor 112 can be arranged separately from the blower B, away from the blower B or on the housing of the blower B, for example directly at the outlet, or in the housing of the blower B.
As mentioned, the blower B is a side channel blower or peripheral blower. Blowers B of this type are broadly comparable to radial blowers, such as are typically used in purge gas delivery devices, in terms of their effectiveness, but have the crucial advantage that their working rotational speed range is far lower than the working rotational speed range of radial blowers, typically around a third of that of radial blowers. They are accordingly superior to radial blowers in their acoustic characteristics, since their imbalance-induced structure-borne noise is significantly lower than that of radial blowers. Due to their lower rotational speed, the kinetic energies stored in the rotating masses of the blower are smaller than in radial blowers. This results in advantageous dynamic characteristics. The power consumption, typically the current consumption, is lower because smaller masses have to be accelerated and decelerated when the rotational speed is changed. The side channel blower or peripheral blower can therefore be accelerated and decelerated more rapidly. This is crucially advantageous for use in motor vehicle manufacturing. Conversely, the “delivery pressure over delivery flow” characteristic curve rises significantly as the delivery flow decreases, and the delivery pressure reaches its highest value at zero delivery, i.e. when the blower outlet is closed. Correspondingly, the power consumption of an electric motor for driving the blower also rises, likewise linearly and in a good approximation, towards zero delivery.
The blower B comprises a housing part 1 and a housing part 2 which together form the housing 1, 2 of the blower B. The housing part 2 serves as a cover for the housing part 1. The blower B comprises an inlet 3 and an outlet 4 for the medium to be delivered by the blower B—in the example embodiment, purge gas. In the housing 1, 2, an impeller 10 which in
The electric motor 25 is arranged coaxially with the impeller 10. The shaft of the electric motor 25 can in particular directly form the drive shaft for the impeller 10. The housing part 1 can be elongated in the shape of a socket, and its elongated region can surround the electric motor 25. Alternatively, the electric motor 25 can be arranged in a motor housing of its own, and said motor housing can be fitted on the housing 1, 2 of the blower B.
The electric motor 25 receives its control signals from the controller or regulator 113 (
A delivery channel 5 and an interrupter channel 8 are formed in the housing 1, 2, one behind the other in the circumferential direction around the rotational axis R, and the paddles periodically pass, one after the other, through the delivery channel 5 and the interrupter channel 8 when the impeller 10 is rotary-driven. The inlet 3 and the outlet 4 (
The delivery channel 5 comprises at least one side channel, such as is known from side channel blowers and peripheral blowers. In the example embodiment, the delivery channel 5 comprises a first side channel 6, which extends in the circumferential direction from the inlet 3 up to the outlet 4 along one end-facing side of the paddles 13, and a second side channel 7 which likewise extends from the inlet 3 up to the outlet 4, along the other end-facing side of the paddles 13. In the example embodiment, the two side channels 6 and 7 are also connected via a radial channel which extends from the inlet 3 up to the outlet 4 along the radially outer circumference of the paddles 13.
When the impeller 10 is rotary-driven, the medium to be delivered which is suctioned via the inlet 3 (
The effective area for impulse transmission, i.e. the effective area AP of the paddle, is marked in
Radially inwards from the paddles 13, the impeller 10 comprises a constriction 12 on each of its two end-facing sides. The respective constriction 12 completely encircles the rotational axis R. The housing parts 1 and 2 each engage the assigned constriction 12 via a projection 1a and 2a which correspondingly encircles the rotational axis R. This engagement improves the seal on the delivery channel 5 and interrupter channel 8 towards the radially inner side, in that the engagement forms a sinuous sealing gap 10a, i.e. a labyrinth seal, on each of the two end-facing sides of the impeller 10. The engagement can also serve to radially and/or axially guide the impeller 10.
The paddles 13 each comprise a free outer edge which extends from a left-hand base point 14 of the paddle located on the radially outer circumference of the impeller 10, along a first end-facing side, then along a radially outer circumference and then along the other end-facing side of the paddle 13 up to a right-hand base point 15 of the paddle located on said other end-facing side on the radially outer circumference of the impeller 10. This free outer edge of the paddle which extends from the base point 14, which is the left-hand base point of the paddle in
The increased sealing gap 20 extends radially up to the level of each of the base points 14 and 15 of the paddle and exhibits the area ASG in the longitudinal sectional plane of the effective area AP of the paddle. If the directly adjoining interrupter channel 9 is also then widened radially inwards from the paddles 13 in an overlap with the impeller 10, this wider region does not count towards the sealing gap 20. For the purposes of comparison, only the sealing gap which extends around the paddles 13 from the base point 14 to the base point 15 is adduced as the increased sealing gap 20. Similarly, for the purposes of comparison, only the cross-section of the channel in the longitudinal sectional plane of the effective area AP of the paddle which the paddles 13 pass through is understood to be the free cross-section AIC of the interrupter channel 9.
In the example embodiment, the increased sealing gap 20 is widened along the entire outer edge of the paddle, i.e. continuously from the base point 14 up to the base point 15, axially on the two end-facing sides and radially on the radially outer circumference, as compared to the conventional sealing gap 24. The axial sealing gaps 21 and 23 each exhibit an axial gap width Wa measured in the axial direction. The radial sealing gap 22 exhibits a radial gap width Wr measured in the radial direction. The two axial sealing gaps 21 and 23 can be equal, but can in principle also be unequal. In the example embodiment shown, the radial gap width Wr is larger than the axial gap width Wa. Alternatively, however, the gap widths Wa and Wr can also be equal, or the axial gap width Wa of the axial sealing gap 21 and/or the axial gap width Wa of the other axial sealing gap 23 can be larger than the radial gap width Wr.
The axial gap width Wa of the first sealing gap 21 and/or the axial gap width Wa of the second sealing gap 23 can (each) be invariable, i.e. constant, over the entire radial length of the respective sealing gap 21 and 23. Instead or expediently in addition, the radial gap width Wr can be constant over the entire axial length of the radial sealing gap 22. Although constant gap widths Wa and Wr are preferred, not least because they are simple to produce, one or both of the axial gap widths Wa can vary over the radial length of the respective sealing gap 21 and 23. Instead or additionally, the radial gap width Wr can vary. If one or more of the gap widths Wa and Wr varies/vary along the respective sealing gap 21 to 23, the respective axial gap width Wa increases only monotonically in the radial direction and preferably over at least the majority of the radial length, in order to obtain a sealing gap 21 and/or 23 which is uniformly broadened as viewed over its length, despite said variation, and in particular to avoid local constrictions. If the radial gap width Wr varies in the axial direction, this variation occurs uniformly over the entire axial length of the sealing gap 22, wherein the sealing gap 22 can simply extend convexly in a uniform arc, i.e. can bulge outwards, or can simply extend concavely in a uniform arc, i.e. can bulge inwards.
In expedient embodiments, such as the example embodiment, a widened interrupter channel 9 is provided in order to realise the increased sealing gap 20. At their axially outer base points 14 and 15, the paddles 13 each exhibit the axial width of the annular region of the impeller 10 which borders the paddles 13 radially inwards. The opposing inner walls of the interrupter channel 9 which face each other axially across the respective paddle 13 recede axially via a collar formed at the level of each of the base points 14 and 15 of the paddle, in order to obtain the respective axial gap width Wa. In alternative embodiments, the paddles 13 can be embodied to be narrower along one end-facing side and/or the other end-facing side, such that the inner wall of the interrupter channel 9 which faces the axially recessed axial edge of the paddle can smoothly proceed radially outwards past the respective base point 14 or 15 of the paddle. Providing the uniformly increased sealing gap 20 by axially widening the interrupter channel 9 is however preferred.
The axial sealing gap 21 and/or the axial sealing gap 23 exhibits or each exhibit an axial gap width Wa throughout the respective sealing gap 21 and 23 which is larger than, and in advantageous embodiments at least twice as large as, the axial gap width of the axial sealing gap 10a, adjoining on the radially inner side, between the impeller 10 and the axially facing inner wall region of the interrupter channel 9. The radial gap width Wr can be larger, throughout its axial length, than the axial gap width of the radial sealing gap 10a and preferably at least twice as large as the axial gap width of the sealing gap 10a. The sealing gap 10a expediently exhibits the same gap width throughout its entire profile. The gap width is also preferably invariable in the region of the engagement between the constriction 12 and the projections 1a and 2a, aside from any deviations in the corner regions and edge regions.
The leakage which is specifically set via the interrupter channel 9 by means of increasing the sealing gap 20 can in particular be characterised by the ratio ASG/AP between the area of the sealing gap and the effective area of the paddle. In advantageous embodiments, it holds that ASG/AP≥0.06 or ASG/AP≥0.07. In relation to favourable degrees of effectiveness in the full-load range, i.e. at delivery flows equal to or greater than the delivery flow at the nominal delivery point or nominal point, it is advantageous if ASG/AP≤0.25 or ASG/AP≤0.20. Alternatively or additionally, it holds for the ratio between the area ASG of the sealing gap and the cross-section AIC of the channel that ASG/AIC≥0.05 or preferably ASG/AIC≥0.06. With regard to the degree of effectiveness, it is favourable if ASG/AIC≤0.20 or ASG/AIC≤0.15 or ASG/AIC≤0.13.
In order to flatten the delivery-pressure-over-delivery-flow characteristic curve, a bypass is provided in the second example embodiment, through which the medium to be delivered can flow back from a region of high pressure into a region of low pressure by bypassing the interrupter channel, for example a conventional interrupter channel 8 (
The bypass can be provided solely within the housing 1, 2 of the blower B or can extend successively through the blower housing 1, 2 and the motor housing 26, as indicated in
The bypass 30 comprises the upstream bypass portion 32 which branches off from the delivery channel 5 at a divergence opening 31 which emerges in the high-pressure region of the delivery channel 5. Of the delivery channel 5, the side channel 6 formed in the housing part 1 can be seen in the plan view of
The bypass portions 32 and 34 are cost-effectively, in terms of production, embodied as continuously straight channel portions which are axially open towards the impeller 10. The bypass portions 32 and 34 lead through the projection 1a which, aside from the bypass portions 32 and 34, serves to improve the seal on the delivery channel 5 towards the radially inner side along the profile of the projection 1 a.
As already mentioned, a second bypass branch which leads through the motor housing 26 is provided in the second example embodiment. The second bypass branch comprises an upstream bypass portion 36 and a downstream bypass portion 38 which each emerge in the central bypass portion 33, whence they lead through the housing part 1 and establish a connection to the interior space of the motor housing 26. The points at which the bypass passages 36 and 38 emerge can be seen in
The bypass 30 (
In advantageous embodiments, the upstream delivery portion 5a has an angular extent α of at most 60° or at most 45°. The angular extent γ of the downstream delivery portion 5c preferably measures at most 120° or at most 90° or at most 70°. The intermediate delivery portion 5b, in which neither a divergence opening nor a convergence opening for bypassing the interrupter channel 8 emerges, extends over an angle β of advantageously at least 45° or at least 90°. In preferred embodiments, the angular extent β measures at least 120° or at least 180°. The angular extents α, β and γ can in particular be chosen such that α<45°, β>180° and γ<70°. While this is a preferred combination for the angular extents α, β and γ, the relationships previously mentioned can however in principle also be realised in any other combination as desired. With regard to a good degree of effectiveness, however, it is advantageous if it at least holds that β>180°.
In advantageous embodiments, the sum α+β+γ of the angular extents, which corresponds to the angular extent of the delivery channel 5 as a whole, is greater than 270° and preferably greater than 300°.
It is favourable for establishing the spiral flow if the medium to be delivered which is guided back through the bypass 30 is not introduced in the form of a concentrated tangential jet but rather radially or at an angle of at least 45° to the tangential direction. In the second example embodiment, the medium to be delivered which is guided back is channelled back into the delivery channel 5 radially or almost radially through the convergence opening 35, as can be seen in
The two measures for specifically setting a leakage, i.e. by means of an increased sealing gap on the one hand and by means of a bypass on the other, can be realised separately from each other or also in combination. When realised in combination, the sealing gap can be broadened to a lesser extent and/or the bypass can be realised with a larger overall flow resistance and/or the angular distance between the divergence opening and the convergence opening can be reduced, such that the two measures in combination generate the desired flattening of the delivery-pressure-over-delivery-flow characteristic curve. In simple and not least for this reason preferred embodiments, however, only one of the two measures is realised.
The bypass 40a comprises an upstream bypass portion 42, a downstream bypass portion 44 and the bypass valve 43 which connects the bypass portions 42 and 44 to each other when the bypass valve 43 assumes an opened valve state. In expedient embodiments, the bypass valve 43 can assume a closed state in which it separates the bypass portions 42 and 44 from each other and thus blocks the bypass 40a. The bypass valve 43 can in principle be adjusted between a state of minimum throughput and a state of maximum throughput continuously or discontinuously in one or more increments, preferably in this case abruptly between minimum and maximum throughput. The state of minimum throughput can in particular be a closed state, but can in principle also be a state in which the bypass valve 43 permits a small throughput, i.e. a small leakage flow.
The bypass 40a can connect the outlet 4 to the inlet 3, in that the divergence opening 41 emerges in the outlet 4, the bypass 40a accordingly branches off from the outlet 4, and the convergence opening 45 emerges in the inlet 3. In the example embodiment, the divergence opening 41 emerges in an outlet support which protrudes from the housing of the blower B, i.e. the bypass 40a branches off in the region of the outlet support, and the convergence opening 45 emerges in a convergence support which protrudes from the housing of the blower B. The convergence support and the outlet support form part of the housing of the blower B. The bypass 40a is advantageously formed while still within or on the housing of the blower B, such that the bypass 40a does not have to be fitted at the point of installation in addition to the blower B, but can rather be fitted together with the blower B as a unit.
The bypass valve 43 comprises a valve element 46, for example a valve piston, and a valve spring 47 which acts on the valve element 46 towards the position of minimum throughput. A control conduit 48 branches off on the high-pressure side of the blower B, via which medium to be delivered is guided from the high-pressure side of the blower B to the valve element 46, in order to apply a pressure of the high-pressure side of the blower B to the valve element 46, counter to the spring force of the valve spring 47. The control conduit 48 can for example branch off in the high-pressure region of the delivery channel 5 or in a portion of the outlet 4 which directly adjoins the delivery channel 5. The control conduit 48 can instead also branch off from the outlet support at the outlet 4 or, as in the example embodiment, branch off from the upstream bypass portion 42. The high-pressure side of the blower B extends via the outlet 4 from a downstream portion of the delivery channel 5 up to a consumer to which the medium to be delivered is supplied by means of the blower, for example up to the suction region 107 of the arrangement in
Similar to the third example embodiment, the specific leakage is established in the fourth example embodiment by a bypass 40b which is exposed in a partial section of the housing part 1. Unlike the bypass 40a of the third example embodiment, the bypass 40b branches off from the outlet 4 at a divergence opening 41 in a portion of the outlet 4 which extends between the delivery channel 5 and an outlet support which protrudes from the housing part 1. In the example embodiment, the divergence opening 41 radially lies directly above the interrupter channel 8.
The bypass 40b emerges at a convergence opening 45 in an upstream delivery portion of the delivery channel 5 which borders the interrupter channel 8. The statements made with respect to the convergence opening 35 of the second example embodiment (FIGS. 9 to 11) advantageously apply in relation to the arrangement of the convergence opening 45. The divergence opening 41 could also in principle even emerge in a downstream delivery portion of the delivery channel 5, wherein the statements made with respect to the downstream delivery portion 5c of the second example embodiment apply with regard to the downstream delivery portion in such a modification.
The bypass 40b extends from the divergence opening 41 up to the convergence opening 45, radially above the interrupter channel 8 or axially alongside the interrupter channel 8, and can in particular extend at a narrow radial distance along the outer circumference of the interrupter channel 8, as in the example embodiment. The bypass 40b can be closed by the other housing part 2 (
Like the bypass 40a of the third example embodiment, the bypass 40b comprises an upstream bypass portion 42, which branches off from the outlet 4 at its divergence opening 41, and a downstream bypass portion which emerges at its convergence opening 45 in the delivery channel 5. A bypass valve 43 is arranged between the divergence opening 41 and the convergence opening 45.
The bypass valve 43 comprises a valve element 46 which can be moved back and forth between a position of minimum throughput and a position of maximum throughput. In the position of minimum throughput, the bypass valve 43 can permit a certain small leakage flow or advantageously separate the divergence opening 41 from the convergence opening 45 and thus interrupt the bypass 40b. The bypass valve 43 also comprises a valve spring 47 which applies a spring force to the valve element 46 towards the position of minimum throughput. A differential pressure which prevails between the divergence opening 41 and the convergence opening 45 acts counter to the valve spring 47.
The bypass valve 43 of the fourth example embodiment comprises a spring space 49 in which the valve spring 47 is arranged. The spring space 49 is connected to the convergence opening 45 via the downstream bypass portion and is thus relieved of pressure.
The bypass valve 43 is embodied as a reflux valve in the fourth example embodiment, but can in principle also be formed as a valve comprising for example a valve slider. The valve spring 47 pushes the valve element 46 into a valve seating 46a. Each of the spring force and the opposing pressure force of the medium to be delivered points through the valve seating 46a. If the valve element 46 moves towards the position of maximum throughput, a leakage flow of the medium to be delivered flows into the bypass portion 42 via the divergence opening 41, through the valve seating 46a and past the valve element 46, into the downstream bypass portion and finally through the latter's convergence opening 45 into the delivery channel 5.
In the third example embodiment and fourth example embodiment, the leakage flow can be set very exactly by means of the bypass valve 43. The respective bypass valve 43 is configured such that the valve element 46 moves from the position of minimum throughput towards the position of maximum throughput only and always when a differential pressure between the pressure at the divergence opening 41 and the pressure at the convergence opening 45, which is predetermined by means of the valve spring 47, is exceeded. The respective bypass valve 43 can in particular be configured such that this threshold pressure corresponds to at least 80% or at least 90% of the nominal delivery pressure of the blower B. The nominal delivery pressure is the delivery pressure at the nominal delivery point NP of the blower B. If the configuration is such that the threshold pressure is greater than the nominal delivery pressure of the blower B, then the threshold pressure measures at most 120% or at most 110% of the nominal delivery pressure in advantageous embodiments. Configuring the bypass valve 43 such that the threshold pressure corresponds to the nominal delivery pressure of the blower B is particularly expedient.
The paddles can thus comprise the rounded profile 16 over their entire outer edge or only in one or more portions of their edge or can instead comprise the chamfer 17 over their entire outer edge or only in one or more portions of their edge. In modifications, the paddles 13 can comprise the rounded profile 16 in one or more portions of their edge and the chamfer 17 in one or more other portions of their edge, as viewed over their entire outer edge.
The paddles 13 can comprise a rounded profile 16 and/or a chamfer 17 on their front sides only. Alternatively, the paddles 13 can also be convexly rounded or chamfered on their outer edge. A convex chamfer 17 can in particular be trapezium-shaped or conically tapered as viewed in the radial plan view of
Due to the rounded profile 16 and the chamfer 17 of the outer edge of the paddle, the area of the sealing gap of the paddles 13 which is provided in the circumferential direction in the interrupter channel is reduced. This measure also reduces the energy transmission in the overload range, i.e. when there is significant throttling on the pressure side, and thus flattens the delivery-pressure-over-delivery-flow characteristic curve.
This measure also establishes a specific leakage in the interrupter channel via the circumferential extent of the interrupter channel.
In modifications, the paddles 13 can also be inclined in the forward direction, i.e. in the rotational direction, over their entire radial extent. In another modification, they can invert more than once as viewed over their radial height or can be roundly inclined continuously or only in a radially outer region of the paddle. Alternatively, the paddles 13 can be inclined counter to the rotational direction over their entire radial extent or only in portions. It is however preferred that they be inclined in the forward direction. If, as is preferred, the rotational direction of the blower can be reversed, then the rotational direction is understood to be the rotational direction in which the impeller is predominantly driven and/or for which the blower is primarily configured.
In the example embodiments described above, the “delivery pressure over delivery flow” characteristic curve is flattened by geometrically altering the blower and/or by means of a bypass valve. Alternatively or additionally, it can also be flattened by limiting the power consumption, in particular the current consumption, of the electric motor 25 (
The measures in accordance with an aspect of the invention can each be realised individually in a blower B. It is however also possible to employ two or more of the measures, which have been individually disclosed merely by way of example, in combination in the same blower, in order to obtain the flattened and preferably inverting delivery-pressure-over-delivery-flow characteristic curve. Within the meaning of an aspect of the invention, the description of a “flattened characteristic curve” also encompasses a falling, i.e. instable characteristic curve. The one or more measures in combination can be advantageously embodied such that the delivery pressure, i.e. the differential pressure between the inlet 3 and the outlet 4, for example the differential pressure directly across the interrupter channel 8 or 9, is at most 20% or at most 10% above the nominal delivery pressure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019120410.0 | Jul 2019 | DE | national |
