Patent Application
20190024732
The invention relates generally to a device for actuating a clutch in an actuating direction against a restoring force acting in a restoring direction. In particular, the invention relates to such a device in a motor vehicle, as used on a large scale in the automobile industry.
Automated or automatic clutch installations with wet or dry friction clutches which, for transmission of torque, are kept in an engaged state or closed by spring force and can be transferred by means of a pneumatic, hydraulic or electrical actuator against the spring force to a disengaged or open state in order to interrupt transmission of torque have been known for a long time. Pneumatic actuators or setting cylinders with an associated pneumatic switching valve arrangement are predominantly used for clutch actuation in utility vehicles (trucks, buses) with automated clutch installations (‘CBW’=‘Clutch By Wire’) for easing driver workload, with automated manual transmissions (‘AMT’=‘Automated Manual Transmission’) for automation even of manual change actions or with double clutch transmissions (‘DCT’), since compressed air is already available in utility vehicles, insofar as both the operating medium and the drive energy for a pneumatic actuator are present and do not otherwise have to be supplied.
In the case of actuation of the clutch it is important to be able to execute sensitive setting movements by means of the actuator, particularly in the region of the clutch pressure point, so as to bring about or interrupt transmission of torque as smoothly as possible. Conventional motor vehicle clutches have a force/travel plot in which force over travel rises continuously, for example substantially linearly, up to a maximum value in the region of the clutch pressure point and thereafter no longer rises or slightly declines. It will be evident therefrom that the pressure built up in a pneumatic actuator for reaching the force maximum is too high, after exceeding this maximum, in order to maintain a position in the vicinity of the clutch pressure point. In order to nevertheless make possible a relatively sensitive positional setting in the vicinity of the clutch pressure point use is made in the prior art of relatively complicated algorithms for control of the actuator pressure, in which pneumatic switching valves connected with the actuator are cyclically activated, i.e. by pulse width modulation and/or pulse frequency modulation. In addition, in order to optimize the sensitivity of the setting, pneumatic switching valves with different throughflow cross-sections for pressure control in the actuator are connected in parallel with one another. Systems of that kind are available from, for example, the company Knorr-Bremse Systeme für Nutzfahrzeuge GmbH (‘Knorr’), Munich, Germany.
However, on the one hand cyclic operation of the pneumatic switching valves has the effect that in the course of use thereof these are activated very frequently; in practice, for example, the pneumatic switching valves are designed for several hundred million actuations, which obviously requires a correspondingly robust and expensive construction of the switching valves. On the other hand, cyclic operation of the pneumatic switching valves, i.e. constant alternation of application of air and venting of air, is accompanied by a comparatively high consumption of compressed air, which is unfavorable with respect to energy efficiency. Not least, integration of the pneumatic switching valves, i.e. the inlet and outlet magnetic valves, in the actuator as is the case with, for example, the systems of the company Knorr has the consequence that the actuator requires a relatively large amount of constructional space not only in radial direction, but also in axial direction. However, the available installation space is usually rather tightly dimensioned at or in the transmission housing.
Moreover, for improvement of sensitivity (accuracy and setting speed) in positional setting with a pneumatic setting cylinder it has already been proposed in the prior art—see, for example, documents DE 10 2011 078 820 A1 and DE 10 2010 022 747 A1—to mechanically connect a hydraulic cylinder in series with the pneumatic setting cylinder. In that case, the hydraulic cylinder on each occasion serves the purpose of braking or damping the movement of the piston of the pneumatic setting cylinder.
More precisely, according to the document DE 10 2011 078 820 A1 (FIG. 1) a setting drive pneumatically driven with travel sensing by means of a position sensor comprises a pneumatic piston, which can be loaded with pneumatic pressure on both sides, with a piston rod. A double-acting hydraulic cylinder having a hydraulic piston, which separates two hydraulic chambers in the hydraulic cylinder, with a piston rod on one side is seated on a common axle behind the pneumatic setting drive. The piston rod of the pneumatic piston and the piston rod of the hydraulic piston are coupled together for hydraulic damping of the setting movements produced by means of the pneumatic setting drive. In that case, the pneumatic piston can be braked in defined manner or fixed by appropriate activation, which is dependent on the travel signal of the position sensor, of a proportional valve present in a hydraulic line connecting the two hydraulic chambers of the hydraulic cylinder.
Moreover, in the case of this prior art a further, similarly displaceable piston is arranged in the hydraulic cylinder and separates in the hydraulic cylinder a further chamber from the hydraulic chamber, which is disposed on the side of the hydraulic piston remote from the pneumatic setting drive. Gas under elevated pressure is enclosed in this further chamber, which gas serves the purpose, in the case of movement of the hydraulic piston, of providing compensation for different volume changes in the two hydraulic chambers, which result from the two hydraulic effective areas of the hydraulic piston differing from side to side (entire piston cross-section on one side, piston cross-section minus piston rod cross-section on the other side), and for thermal expansion of the hydraulic fluid. The further piston and the further chamber in the hydraulic cylinder thus form a compensation unit with an effect corresponding with that of a single-tube damper.
Such a serial arrangement of pistons and spaces or chambers, however, requires a substantial amount of axial constructional space. Moreover, this prior art is capable of improvement with respect to adequate venting of the hydraulic chambers.
By contrast, in the prior art according to document DE 10 2010 022 747 A1 (FIG. 1) a pneumatically driven setting cylinder has a pneumatic piston which can be loaded on one side with compressed air by way of a compressed air chamber and is loaded on the other side by way of an opposing force of a vehicle clutch. The pneumatic piston is coupled by means of a piston rod with a hydraulic piston of a double-acting hydraulic cylinder which is flange-mounted on or screw-connected with a housing of the pneumatic setting cylinder and has two pressure chambers. The two pressure chambers of the hydraulic cylinder are connected together by way of a line with a throttle and a switching valve (2/2-way valve) connected in series therewith. When the switching valve is closed, the hydraulic cylinder is to block movement of the pneumatic piston. If, on the other hand, the switching valve is open then the pneumatic piston is to be able to move and, in particular, braked or damped as a function of the fixed throttle cross-section of the throttle.
However, the damping or braking behavior is not settable here. In addition, a compensation unit as in the above-described prior art is not provided, so that the hydraulic region of this arrangement would have to have substantial levels of ‘softness’ (such as conductor elasticities, air inclusions or the like) in order to even permit movement. Finally, the above comments with respect to the requirement for axial constructional space and venting particularly apply, in corresponding manner, to this prior art.
By comparison with the prior art outlined above the invention has the object of creating a device, which is of simplest and most compact construction possible, for actuation of a clutch in an actuating direction against a restoring force acting in a restoring direction, particularly in or for a motor vehicle, which avoids the above disadvantages and permits clutch actuation as sensitively as possible, particularly in a more energy-efficient manner.
This object is fulfilled by the features indicated in claim 1. Advantageous or expedient developments of the invention are the subject of claims 2 to 17.
According to the invention a device for actuating a clutch in an actuating direction against a restoring force acting in a restoring direction, particularly in a motor vehicle, comprises an actuator with a pneumatic chamber which is bounded by a pneumatic effective area and can be selectably loaded with a pneumatic pressure from a compressed air source so as to generate a force at the pneumatic effective area in the actuating direction, a first hydraulic chamber which is hydraulically connectible with a reservoir for hydraulic fluid by way of an electromagnetically actuable first 2/2-way proportional valve and which is bounded by a first hydraulic effective area having the same orientation with respect to the pneumatic effective area, a second hydraulic chamber which is hydraulically connectible with the reservoir by way of an electromagnetically actuable second 2/2-way proportional valve and which is bounded by a second hydraulic effective area opposite to the first hydraulic effective area and a setting element which is in actuation-effective connection with the clutch and which can be loaded with force by way of the aforesaid effective areas and is movable in defined manner, wherein a control is provided, by means of which the pressure loading of the pneumatic chamber and valve settings of the first and second 2/2-way proportional valves are controllable independently of one another, and wherein through closing of the first 2/2-way proportional valve a movement of the setting element in the restoring direction can be braked in controlled manner by way of the first hydraulic effective area and through closing of the second 2/2-way proportional valve movement of the setting element in the actuating direction can be braked in controlled manner by way of the second hydraulic effective area.
Due to the fact that, in accordance with the invention, the 2/2-way proportional valves are used for hydraulic movement control of the setting element then at the outset the multiplicity of robustly and expensively designed pneumatic inlet and outlet magnetic valves for actuator control as provided in the prior art is redundant. Also eliminated are cyclic valve operation and the associated high consumption of compressed air, as also the cost connected therewith in the prior art, to achieve through reduction of dead spaces a smaller tendency to oscillation. The device according to the invention is thus not only more advantageous with respect to energy efficiency thereof, but also significantly quieter with respect to background noise in operation than the previously known pneumatic solutions.
By comparison with the above-described hydraulically braked or damped systems the device according to the invention is particularly distinguished by the fact that venting as well as pressure and volume equalization in rest setting are significantly improved. In each actuation the pressure-free hydraulic branch is (part-)filled with hydraulic fluid from the reservoir by way of the open one of the 2/2-way proportional valves, whereas the hydraulic branch disposed under pressure is (part-)emptied towards the reservoir by way of the throttling other one of the 2/2-way proportional valves. The hydraulic chambers of the actuator are constrainedly vented by these processes, optionally with assistance by a continuously increasing arrangement of the connecting lines with respect to the reservoir. There is thus reliable avoidance of ‘softnesses’, which are caused by air inclusions, in the hydraulic system, which has a positive effect on setting accuracy and setting speed of the actuator. In addition, compensation for thermal expansions of the individual components and of the hydraulic fluid as well as deformations of the spring tongues of the clutch can be provided in very simple manner by 2/2-way proportional valves open in rest setting of the device.
As a consequence of the provided independence in the control of the pneumatic and hydraulic processes there is, not least, the possibility through suitable (preliminary) current supply to the individual valves to more rapidly and directly effect reversal of the setting element movement due to the elimination of rerouting times, which can also be conducive to a high degree of setting accuracy.
In a particularly simple embodiment of the device (only) one spring-biased electromagnetically actuable 3/2-way switching valve activatable by means of the control can be connected between the compressed air source and the pneumatic chamber of the actuator, wherein the 3/2-way switching valve in the state of activation by the control connects the compressed air source with the pneumatic chamber and in the state of non-activation by the control connects the pneumatic chamber with the environment. However, as an alternative thereto the design of the pneumatic actuator activation can be such that a spring-biased and electromagnetically actuable first 2/2-way switching valve which is activatable by means of the control and in the state of activation by the control connects the compressed air source with the pneumatic chamber is connected between the compressed air source and the pneumatic chamber of the actuator, in which case a spring-biased and electromagnetically actuable second 2/2-way switching valve which is similarly activatable by means of the control and in the state of activation by the control connects the pneumatic chamber with the environment is connected between the pneumatic chamber and the environment. The compressed air state at the actuator is thus maintained when the switching valves are not activated.
The hydraulic activation state of the actuator can similarly be maintained without current if the 2/2-way proportional valves in the state of non-activation by the control are spring-biased into a blocking/zero setting in order to separate the respective hydraulic chamber of the actuator from the reservoir for hydraulic fluid. However, alternatively thereto the 2/2-way proportional valves in the state of non-activation by the control can also be spring-biased into a pass/zero setting so as to connect the respective hydraulic chamber of the actuator with the reservoir for hydraulic fluid, which in most cases of use is more advantageous with respect to energy consumption.
In a preferred embodiment of the device a bypass line with a bypass with a bypass non-return valve which blocks in a direction from the actuator to the reservoir can be connected in parallel with the first and/or the second 2/2-way proportional valve. This advantageously makes possible preliminary current supply to the respectively unloaded 2/2-way proportional valve without as a result possible impairment of the supply of the unloaded hydraulic branch with hydraulic fluid.
In further pursuance of the concept of the invention a pump line with an electric-motor drivable hydraulic pump and a pump non-return valve, which is arranged at the pump outlet side and which blocks towards the hydraulic pump, can be connected with the second 2/2-way proportional valve, wherein the hydraulic pump is activatable by means of the control in order to selectably actively load the second hydraulic chamber of the actuator with a hydraulic pressure, which enables fine regulation of the actuator movements for, for example, generating ‘micro-slip’ at the clutch.
In addition, particularly for the purpose of increasing stiffness of the hydraulic system, the reservoir for hydraulic fluid can be constructed to be closed so that there remains above a liquid level of the hydraulic fluid in the reservoir an air chamber which is connected by way of a pressure-reducing valve with the compressed air source so as to load the hydraulic fluid in the reservoir with a preliminary pressure greater than atmospheric pressure.
The actuator itself preferably comprises a cylinder housing, which has a pneumatic pressure connection and at least one hydraulic pressure connection and in which a piston operatively connected with the setting element is received to be longitudinally displaceable, the piston together with the cylinder housing defining the pneumatic chamber, which can be loaded with pressure by way of the pneumatic pressure connection, and at least one of the hydraulic chambers, which can be connected with the hydraulic pressure connection, wherein the said chambers are separated from one another by means of a sealing arrangement and wherein the pneumatic effective area axially bounding the pneumatic chamber and the hydraulic effective area axially bounding the corresponding hydraulic chamber are formed at the piston. As a result of provision of the pneumatic and hydraulic effective areas at one and the same piston in one and the same cylinder housing there is at the outset the advantage of a smaller axial constructional length of the actuator by comparison with the prior art outlined in the introduction. Moreover, by comparison with a solution in which two (or more) housings arranged in a row one after the other are flange-mounted on one another there is reliable avoidance in accordance with the invention of static over-determination which in the prior art can lead to jamming of or increased friction at the moved part or parts if the housings are not very precisely centered. In addition, through omission of seals between different housings in accordance with the invention there is a smaller outlay on sealing.
In principle, the cylinder housing and the piston can define, in addition to the pneumatic chamber, only one hydraulic chamber, wherein the pneumatic effective area and the hydraulic effective area can be oriented in the same sense or oriented oppositely to one another. The further hydraulic effective area of the actuator would then be formed at a suitable place outside the cylinder housing in a separate housing with a hydraulic chamber. However, with respect to a small requirement for constructional space and low cost, a design is preferred in which the cylinder housing of the actuator has two hydraulic pressure connections and together with the piston defines, in addition to the pneumatic chamber, two hydraulic chambers which are each connected with a respective one of the hydraulic pressure connections and which are separated from one another and from the pneumatic chamber by means of two sealing arrangements, wherein apart from the pneumatic effective area two hydraulic effective areas each axially bounding a respective one of the hydraulic chambers are formed oppositely to one another at the piston.
A particularly short constructional length of the actuator can be achieved if the cylinder housing and the piston of the actuator, in order to form the at least one of the hydraulic chambers and the hydraulic effective area bounding this, are formed to be stepped at the circumference.
Moreover, for a space-saving as well as low-friction and low-wear arrangement very close to the transmission the actuator can be constructed in the form of a central release device, in which case the cylinder housing has a passage for a transmission shaft in the region of a center axis and the piston received in the cylinder housing to be longitudinally displaceable is an annular piston carrying a release bearing as setting element.
In that case, in principle, two hydraulic chambers can be formed in the cylinder housing one behind the other at the outer circumference or inner circumference of the annular piston and the pneumatic chamber can be formed at an end of the annular piston. However, with respect to a particularly short axial constructional length a configuration is preferred in which in the actuator one of the hydraulic chambers is formed at the outer circumference of the annular piston and another one of the hydraulic chambers is formed at the inner circumference of the annular piston, with the pneumatic chamber being disposed at the end with respect to the annular piston.
If the actuator is to be disposed in operative connection with the clutch by direction change or translation means by way of, for example, a clutch lever, then available as an alternative is a design in which the actuator is constructed in the form of a clutch slave cylinder with a central blind bore, in which the piston is received to be longitudinally displaceable, in the cylinder housing, the piston being connected, to be effective in terms of actuation, with a central piston rod as setting element. By comparison with a central release device, such an actuator is more flexible with respect to the location of the mounting, is less strongly thermally loaded, is more easily exchangeable and also is not exposed to abraded material from the clutch.
In a more advantageous and simpler embodiment the two hydraulic chambers can be formed axially one behind the other in such an actuator at the outer circumference of the piston, whereas the pneumatic chamber is disposed at the end with respect to the piston.
In an alternative, which is shorter with respect to constructional length, the piston of the actuator can have a central recess into which a central projection provided at the cylinder housing enters, where one of the hydraulic chambers is formed between the projection of the cylinder housing and the recess of the piston and another one of the hydraulic chambers is disposed at the outer circumference of the piston, with the pneumatic chamber being disposed at the end with respect to the piston.
Finally, in an advantageous development of the afore-described different actuators at least the sealing arrangement separating the pneumatic chamber from the respective hydraulic chamber can comprise two sealing elements, which are axially spaced from one another and which have therebetween an intermediate space connected with the environment by way of an equalization channel. Whereas in this embodiment it is also possible for a degree of lubrication of the pneumatic seal to be achieved by way of the hydraulic seal, the equalization channel particularly serves the purpose of preventing air from passing from the pneumatic side into the hydraulic system.
The invention is explained in more detail in the following by way of preferred embodiments with reference to the accompanying, partly schematic drawings, in which the same or corresponding parts have been provided with the same reference numerals—in a given case supplemented with elevated dashes (‘or”) for identification of the respective valve or actuator variants—and in which, for simplification of the illustration, elastomeric or elastic parts are illustrated in the undeformed state. In the drawings:
In the drawings and in the following description an illustration or explanation of the respective clutch and the mode and manner in which the respective setting element at the actuator—release bearing in the case of the first actuator variant; piston rod in the case of the second and third actuator variants—is disposed in operative connection with the clutch has been dispensed with, since features with respect thereto are familiar in structural and functional respects to the expert and further explanations with regard to those are not necessary for an understanding of the present invention. Equally, in the case of all actuator variants the respective piston is secured against turning in the cylinder housing, but this has not been individually illustrated since these measures are known per se.
In
The device 10 comprises, for generation of the setting movement, in the first instance an actuator 12 comprising a cylinder housing 14 and a piston 16 received therein to be longitudinally displaceable, which together define various pressure chambers and different effective areas in the actuator 12. Thus, the actuator 12 has a pneumatic chamber KP, which is bounded by a pneumatic effective area AP and which can be selectably loaded with a pneumatic pressure from a compressed air source QP so as to generate at the pneumatic effective area AP a force in the actuating direction B. In addition, the actuator 12 has a first hydraulic chamber KH1, which can be hydraulically connected with a reservoir QH for hydraulic fluid by way of an electromagnetically actuable, first 2/2-way proportional valve VH1 and which is bounded by a first hydraulic effective area AH1 having the same orientation with respect to the pneumatic effective area AP (see also
In addition, for the above circuit connection of the actuator 12 into the device 10 the cylinder housing 14 has a pneumatic pressure connection EP, by way of which the pneumatic chamber KP can be loaded with pressure, and two hydraulic pressure connections EH1, EH2, which are each connected with a respective one of the hydraulic chambers KH1, KH2. The latter, as will be explained in detail, are separated from one another and from the pneumatic chamber KP by means of two sealing arrangements 18, 20.
Moreover, the device 10 comprises an electronic control CPU, by means of which the pressure loading of the pneumatic chamber KP and valve settings of the first and second 2/2-way proportional valves VH1, VH2 can be controlled independently of one another, as will be described in detail in the following. In that regard, movement of the setting element G in the restoring direction R can be braked in controlled manner by way of the first hydraulic effective area AH1 by closing the first 2/2-way proportional valve VH1, whilst movement of the setting element G in the actuating direction B can be braked in controlled manner by way of the second hydraulic effective area AH2 by closing the second 2/2-way proportional valve VH2.
For pressure loading of the pneumatic chamber KP of the actuator 12 the pneumatic pressure connection EP at the cylinder housing 14 is connected by way of a pneumatic line LP with the compressed air source QP. In that case, provided between the compressed air source QP and the pneumatic chamber KP of the actuator 12 is a spring-biased, electromagnetically actuable 3/2-way switching valve VP arranged in the pneumatic line LP. The 3/2-way switching valve VP can be activated by means of the control CPU by way of an electrical control line SP. In that case, the 3/2-way switching valve VP in the state of activation by the control CPU connects the compressed air source QP with the pneumatic chamber KP of the actuator 12 and in the state of non-activation by the control CPU connects the pneumatic chamber KP of the actuator 12 with the environment (indicated in
As far as the hydraulic circuit connection of the actuator 12 into the device 10 is concerned, the pressure connections EH1, EH2 thereof are each connected with the reservoir QH by way of a respective hydraulic line LH1, LH2. The afore-mentioned 2/2-way proportional valves VH1, VH2 are in that case each seated in a respective one of the hydraulic lines LH1, LH2 and are each connected by way of a respective electrical control line SH1, SH2 with the control CPU. In a first valve alternative—respectively encircled in
In constructional terms, the 2/2-way proportional valves VH1, VH2 can, for example, be constructed as electromagnetically actuable 2/2 ball-seat valves spring-biased into a through/zero setting in the non-activated state, as known in principle from document DE 196 33 420 A1 of the present applicant. In these valves arranged between a pressure chamber and a drain chamber of a valve housing is a ball seat for a spherical valve body which is received in the drain chamber. A valve spring arranged in the pressure chamber urges the valve body away from the ball seat, whilst provided on the side remote from the pressure chamber is a magnetic drive by means of which the valve body can be urged in the direction of the valve seat. As a function of current supply to the magnetic drive a predominantly annular throttle gap of predetermined size arises between the valve body and the valve seat and depending on size provides a greater or lesser degree of resistance to throughflow of the hydraulic fluid from the pressure chamber to the drain chamber, this resistance increasing the pressure in the pressure chamber (backpressure principle). Whereas in the present case of use of such a valve the pressure chamber is connected with the corresponding pressure connection EH1 or EH2 of the actuator 12, the drain chamber of the valve is connected with the reservoir QH for hydraulic fluid.
However, in a second valve alternative—in
Finally, with respect to the schematic circuit diagram of the device 10 according to
Further details of the actuator 12, which in the embodiments according to
In the illustrated embodiment the cylinder housing 14 consists substantially of three parts arranged concentrically with respect to the center axis Z, namely an annular first housing section 24, which is preferably injection-molded from plastics material and which has a fixing shoulder 25, a sleeve-like second housing section 26, which is preferably formed from metal by reshaping and which has at the axial end a radially inwardly extending annular surface 27, and a sleeve-like stepped third housing section 28, which is preferably similarly formed from metal by reshaping and which has at the axial end a radially outwardly extending annular flange 29. Whereas the first housing section 24 is inserted by the fixing shoulder 25 thereof into the second housing section 26 and secured and sealed in this position in suitable manner (shown merely schematically in the figures), the second housing section 26 and the third housing section 28 are secured to one another in the region of the annular flanges 27, 29, for example by means of a weld connection. According to, in particular,
The annular piston 16, which also is preferably injection-molded from a plastics material, of the actuator 12 is provided on its end face on the left in
As a result, in the actuator 12—in an axially very compact mode of construction—one (KH2) of the hydraulic chambers is formed at the outer circumference of the annular piston 16 and the other one (KH1) of the hydraulic chambers at the inner circumference of the annular piston 16, whereas the pneumatic chamber KP is disposed at the end with respect to the annular piston 16. In detail, as can be best seen in
In that case the actuator 12 has a total of four sealing guide surfaces, namely a first sealing guide surface 42 at the outer circumference of the third housing section 28 of the cylinder housing 14 on the right of the step 30, a second sealing guide surface 44 at the inner circumference of the second housing section 26 of the cylinder housing 14, a third sealing guide surface 46 at the outer circumference of the third housing section 28 of the cylinder housing 14 on the left of the step 30 and a fourth sealing guide surface 48 at the outer circumference of the annular piston 16 on the left of the outer collar 38. Whereas the afore-mentioned first sealing arrangement 18 co-operates with the first sealing guide surface 42, the second sealing arrangement 20 already discussed further above co-operates with the second sealing guide surface 44. In analogous manner, a third sealing arrangement 50 at the annular piston 16 is associated with the third sealing guide surface 46 at the cylinder housing 14 and a fourth sealing arrangement 52 at the cylinder housing 14 is associated with the fourth sealing guide surface 48 at the annular piston 16.
The first sealing arrangement 18 seals between the first hydraulic chamber KH1 and the pneumatic chamber KP and for that purpose, as can be best seen in
As best inferred from
According to
In addition, the fourth sealing arrangement 52 seals between the second hydraulic chamber KH2 and the environment and according to
In addition, in
The operation of the device 10 is explained in more detail in the following in which the control CPU suitably activates and co-ordinates the 3/2-way switching valve VP as well as the first and second 2/2-way proportional valves VH1, VH2 inter alia in dependence on the position signals detected by means of the sensor arrangement (position sensor PS, signal element SE) at the actuator 12. In addition, the control CPU obtains default settings from a superordinate transmission electronic system (TCU; not shown in the figures) by way of a suitable bus system (CAN, LIN, FlexRay or the like) or, for example, default settings from a travel or angle sensor of a clutch pedal with a pedal force simulator (similarly not illustrated), depending on the respective use of the device 10.
In order to actuate the clutch, the control CPU initially activates the 3/2-way switching valve VP in order to connect the compressed air source QP with the pneumatic chamber KP in the actuator 12, whereby the compressed air is applied directly to the pneumatic effective area AP, which in the cylinder housing 14 actively initiates a movement of the annular piston 16 in the actuating direction B. As a consequence of this movement of the annular piston 16 the hydraulic fluid, which is present in the second hydraulic chamber KH2 of the actuator 12, is displaced in the direction of the reservoir QH. At the same time, the second 2/2-way proportional valve VH2 associated with the second hydraulic effective area AH2 is subjected by the control CPU to preliminary current supply at a value which fully closes it so that there is passive build-up in the second hydraulic chamber KH2 of the actuator 12 of a hydraulic pressure which acts on the second hydraulic effective area AH2 and in that case generates thereat a force in restoring direction R and thus brakes or seeks to stop the movement of the annular piston 16 in the actuating direction B. The first hydraulic chamber KH1 in the cylinder housing 14 increases in size in company with the movement of the annular piston 16 in the actuating direction B, whereby hydraulic fluid is sucked out or flows on out of the reservoir QH by way of the first 2/2-way proportional valve VH1, which is not supplied with current, i.e. here is open.
The movement travel of the annular piston 16 in the cylinder housing 14 is now regulated in a closed loop by the control CPU in accordance with the default settings from the superordinate transmission electronic system (TCU) as well as the actual positions, which are detected by way of the sensor arrangement at the actuator 12, of the annular piston 16 by reduction of the current at the second 2/2-way proportional valve VH2. In that case, the second 2/2-way proportional valve VH2 is opened in defined manner, as a result of which a hydraulic (back)pressure in the second hydraulic chamber KH2 arises as a function of the respectively open valve cross-section (throttle gap), which pressure—acting on the second hydraulic effective area AH2—brakes the pneumatically constrained movement of the annular piston 16 in the cylinder housing 14 to a greater or lesser extent.
In the equilibrium state (a=b+c), (a) the air pressure, which is provided by the compressed air source QP, multiplied by the pneumatic effective area AP at the annular piston 16 is equal to the sum of (b) the hydraulic pressure, which arises in the second hydraulic chamber KH2 of the actuator 12 as a consequence of the obstructing second 2/2-way proportional valve VH2, multiplied by the second hydraulic effective area AH2 at the annular piston 16 and (c) the spring force of the clutch. In practice, the ratio of the pneumatic pressure to the hydraulic pressure is, for example, approximately 1 to 6, with up to 8 bars air pressure and up to 50 bars of hydraulic pressure. Given these rules, the travel speed of the annular piston 16 in the actuator 12 can be selectively set from maximum possible speed towards standstill of the annular piston 16 in the cylinder housing 14 and also any intermediate positions of the annular piston 16 can be maintained. When a desired position of the annular piston 16 in the cylinder housing 14 is reached, the second 2/2-way proportional valve VH2 is fully supplied with current and thus closed, so that the movement of the annular piston 16 is stopped.
For the actual movement regulation (travel speed and position) the known characteristic of the clutch concerned and the pressures acting on the active effective areas of the actuator 12 can be used in addition to the position signal of the position sensor PS integrated in the actuator 12. These pressures can in that case be ascertained either directly by way of pressure sensors (not illustrated in the figures) or indirectly in the case of the compressed air by way of the bus system and in the case of the hydraulic pressure by way of the current of the respectively active regulating valve VH2 (or VH1).
If there should be over-travel of the predetermined position of the annular piston 16 in the cylinder housing 14 or if the annular piston 16 is to be moved back into its initial or rest setting the first 2/2-way proportional valve VH1 is subject to preliminary current supply to an appropriate value and the compressed air switched off, i.e. the supply of current to the 3/2-way switching valve VP is ended, as then also the supply of current to the second 2/2-way proportional valve VH2. As a consequence thereof the spring force of the clutch pushes, by way of the setting element G, the annular piston 16 in restoring direction R, in which case this rearward movement—analogously to the movement in actuating direction B—can be braked in defined manner or stopped by suitable supply of current to the first 2/2-way proportional valve VH1. There is then build-up in the first hydraulic chamber KH1 as a function of the open valve cross-section of the first 2/2-way proportional valve VH1 of a pressure which acts on the first hydraulic effective area AH1 and thus presents resistance to the rearward movement of the annular piston 16 in the cylinder housing 14. At the same time hydraulic fluid flows on by way of the open second 2/2-way proportional valve VH2 from the reservoir QH into the second hydraulic chamber KH2 of the actuator 12. When the desired position of the annular piston 16 is again reached this can be maintained by closing the two 2/2-way proportional valves VH1, VH2. A further rearward movement of the annular piston 16 into its initial setting can finally take place in controlled manner, with current-free 3/2-way switching valve VP and current-free second 2/2-way proportional valve VH2, by suitable supply of current to the first 2/2-way proportional valve VH1.
In the device 10 according to
The device 10 according to
In the case of the device 10 according to
The device 10 according to
In the actuator 12′ according to
The actuator 12″ illustrated in
If in correspondence with the respective actuation requirements an even greater pneumatic effective area AP should be needed at the actuator 12″ then it would be possible to provide a further sealing arrangement (not shown) radially within the projection 106″ of the cylinder housing 14″ between the projection 106″ and the inner protrusion, which is provided here and receives the bearing member 101″ for the piston rod G, of the piston 16″ so as to separate a central, second pneumatic chamber from the first hydraulic chamber KH1. The first hydraulic pressure connection EH1 would then merely have to be led through the projection 106″ to the first hydraulic chamber KH1 and a connection be created between the pneumatic chamber KP and the second pneumatic chamber.
A device for clutch actuation comprises an actuator with a pneumatic chamber bounded by a pneumatic effective area, two hydraulic chambers each bounded by a respective hydraulic effective area and a setting element, which is operatively connected with the clutch and which can be loaded with pressure by way of said effective areas and is movable. For generation of force in an actuating direction against a restoring force acting in the restoring direction the pneumatic effective area can be loaded with a pneumatic pressure from a compressed air source. The hydraulic chambers are each hydraulically connectible by way of a respective electromagnetically actuable 2/2-way proportional valve with a reservoir for hydraulic fluid. In addition, a control is provided by means of which the pressure loading of the pneumatic chamber and valve settings of the 2/2-way proportional valves are controllable independently of one another. Thus, through closing of one and/or the other 2/2-way proportional valve it is possible by way of the respectively associated hydraulic effective area to provide controlled braking of setting element movement in the actuating direction or in the restoring direction, which permits sensitive clutch actuation in a more energy-efficient manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 000 707.9 | Jan 2016 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/002191 | 12/30/2016 | WO | 00 |
