Patent Application
20180283371
The invention relates to managing excess pressures in hydraulic circuits, and more particularly to devices of the “pressure limiter” or “pressure-relief valve” type.
The invention applies in particular to hydraulic assistance circuits for a vehicle.
The invention thus belongs to the field of vehicle hydraulic assistance and in particular the engagement and the disengagement of this assistance.
Temporary hydraulic assistance is carried out using hydraulic machines which may supply torque to wheels not mechanically motorized. These machines transform the hydraulic energy of pressurized oil into mechanical energy, or the reverse.
Two phases of use are defined: the assistance phase which allows an increase in power/torque, and a freewheel phase. Between these two phases are two transient phases allowing engaging or disengaging hydraulic assistance.
To activate such assistance, the hydraulic circuits are pressurized thanks to a booster pump. This pressure serves in particular for engaging the motors.
In a vehicle Ve, a first hydraulic machine M1 is mounted on a first axle, for example the front axle and a second hydraulic machine M2 is mounted on a second axle, for example the rear axle. What is meant by machines is that they may function as motors or as pumps.
The configuration shown corresponds to a “bicycle chain” (document FR 2 996 176), meaning that during the main use, the first machine M1 acts as a pump for the second machine M2, which acts as a motor.
The vehicle generally comprises a heat engine M which drives the first hydraulic machine M1.
To this end, the discharge of the first machine M1 is connected to the intake of the second machine M2 by a line 11 called a high pressure line and the discharge of the second machine M2 is connected to the intake of the first machine M1 by a line 12 called a low pressure line.
The terms high and low pressure correspond to use when driving forward with torque addition (“main use”).
Consequently, as pressure may be reversed, the terms first line 11 and second line 12 are preferred.
An electric pump unit P, including a booster pump P1 in particular, and an electric motor P2, is provided for boosting lines 11, 12.
By way of an example, the booster pump P1 may also be driven by other elements, such as an axle or a heat engine M.
A pressure limiter 20 is located so that it by-passes the pump P1 for protecting it from possible excess pressure.
The booster pump P1 feeds, through a booster line 10, the first and second lines 11, 12 via two check valves B11, B12 which prevent the oil from being discharged toward the pump P1 when the boost pressure is less than the operating pressures.
The oil comes from a drainage line 13 which is connected to one or more reservoirs R.
The first and the second line 11, 12 operate in a closed circuit and may be subject to excess pressures which may damage the machines M1, M2 or the seals present in the circuit.
By way of an example, the pressures are on the order of 400 bars in one line and a few tens of bars in the other line, at the very least at a boost pressure.
In a classical way, two pressure limiters A11, A12 protect the first and second lines 11, 12 from excess pressure by discharging oil into the booster line 10.
The hydraulic circuit also has a vacuum valve V situated on a vacuum line L.
The vacuum line connects the first or the second line 11, 12 (a selector valve may if necessary be placed between the lines 11 and 12) to the drainage line 13 which leads to the reservoir R.
The valve V is a 2/2 way valve, comprising an inlet and an outlet. The inlet is connected to the line 12 and the outlet to the drainage line 13. The valve V has a passing state and a blocking state.
The change toward a blocking state occurs using a solenoid spool V1, which is controlled electronically. This change of state causes a first transient phase by allowing the effective activation of the hydraulic assistance because the high and low pressure lines 11, 12 are then no longer connected to the reservoir R and may increase in pressure. This pressure increase allows the couplers E1 and E2, which link the components of the hydraulic machines M1 and M2 to the output shafts of said machines, to be activated, so as to make them active in the vehicle, in other words to engage the system. These couplers may be of the disk or claw clutch type, for example of the same type as in the prior art gearbox. They may also constitute the coupling of radial piston motors which disengage from their cam by retraction of the pistons.
Conversely, a spring V2 holds in the rest position the valve V, in a passing state. As soon as the spool V1 is no longer controlled, the valve V resumes a passing position and causes a second transient phase, wherein the pressure in the low pressure line drops, thus disengaging the hydraulic assistance.
Also known is a simplified alternative of the embodiment shown in
Thus, according to the prior art, for the two aforementioned transient steps, it is necessary to intervene electronically on several elements, and in particular the valves V and the booster pump, which imposes structural and electrical network constraints.
As indicated previously, pressure limiting means A11, A12 are provided, designed to protect the first and second lines 11, 12 from excess pressures because the lines 11, 12 operate in a closed circuit and may otherwise be subject to excess pressure likely to damage the machines M1, M2 or the seals present in the circuit.
Each limiter 21, 22 may be set to the desired value.
This solution uses two protection members (the pressure limiters 21, 22).
This solution also uses two protection members (the pressure limiters 23, 24). Also found again in
This solution also uses two protection members. Also found again in
To optimize the available space and reduce the costs of manufacture, simpler members carrying out the same functions are sought.
An attempted solution is proposed in document US 2005/0097887 as illustrated in the appended
This solution consists of grouping all the functions forming the selector valve and pressure limiter into a common cartridge.
More precisely, in the appended
The applicant has identified in particular that, in the device of the type described in document US 2005/0097887 and illustrated in the appended
The device described in document US 2005/0097887 has not undergone significant industrial development. This seems to be due to its complexity of design, of assembly and of operation.
In the aforementioned context, the first objective of the present invention is to propose means which improve the state of the art, particularly by proposing simple design means which improve performance.
The objective is attained according to the invention thanks to a distributor and pressure relief device suitable to be installed in a system comprising a first feed line and a second feed line which may comprise pressurized oil and comprising a discharge and/or booster line, characterized in that the device comprises means forming a pressure selector valve suitable for connecting the lower pressure feed line to the discharge and/or booster line and means forming two valves associated respectively with one of the two feed lines and suitable for opening in the event of excess pressure above a predetermined threshold in the associated feed line so as to discharge the corresponding excess pressure toward the discharge and/or booster line or the other feed line, the two valves comprising a common plug which cooperates with a single seat.
Henceforth, pressure limitation occurs according to the invention by means of a single device, which improves the compactness of the system as well as its cost of manufacture.
According to another advantageous feature of the invention, the plug has at least two surfaces situated on either side of the associated seat and subjected respectively to the pressures coming from the two feed lines.
According to another advantageous feature of the invention, the device comprises confinement means suitable for applying pressure coming from a feed line to a limited localized zone of the plug.
According to another advantageous feature of the invention, the device comprises two translation guides for the plug, separated along the direction of translation thereof, by a distance equal to at least one times the diameter of the plug resting on the associated seat, preferably by a distance equal to at least two times this diameter and very advantageously equal to at least five times this diameter.
According to another advantageous feature of the invention, the device comprises a first translation guide for the plug formed by the cooperation defined between the plug and its associated seat and at least a second guide formed by an end of a plug stem guided on the body, for example a widened surface subjected to the pressure of a feed line.
According to another advantageous feature of the invention, the two pressure relief valves comprise a common support stem which works in tension or in compression under the biasing of at least one spring defining a setting which corresponds to said predetermined threshold.
The invention also relates to assistance systems and to vehicles equipped with a pressure relief device conforming to the invention.
Other features, aims and advantages of the invention will be revealed from the description that follows, which is purely illustrative and not limiting, and which must be read with reference to the appended drawings, wherein:
The preferred embodiments of the invention will now be described.
The appended
The distributor and pressure relief device 70 shown in
The circuit illustrated in
These machines M1, M2 are linked together by a first line 11 and a second line 12 which feed the machines with oil.
Depending on the operating modes, the direction of circulation of the oil and the pressure in these lines 11, 12 may change.
For example, when the equipped vehicle is driven forward and in “torque addition” mode, the first machine M1 acts as a pump and the second machine M2 acts as a motor. Considering that the first line 11 connects the discharge of the first machine M1 to the intake of the second machine M2 and that the second line 12 connects the discharge of the second machine M2 to the intake of the first machine M1, in this case there will be high pressure in the first line 11 and low pressure in the second line 12 and a direction of circulation of the oil from the first machine M1 toward the second M2 in line 11.
What is meant by high pressure is pressures which may be greater than a few hundred bars, for example 400 bars, and low pressures are pressures of a few tens of bars, for example 3 or 30 bars. The low pressure is differentiated from the pressure of the unpressurized oil reservoirs, represented for example by the casings of the machines M1 and M2, and the unpressurized reservoir R, substantially connected to atmospheric pressure. The pressure at low pressure differing from atmospheric pressure is, in known fashion, necessary for proper operation of a closed-circuit transmission.
In operation, a closed loop transmission has a HP line and a LP line. If no torque is produced by the machines, the two lines are at LP pressure, which is a minimal pressure for the closed circuit during operation.
Driving in reverse, the direction of circulation of the oil is reversed and the high pressure is then found in the second line 12 and the low pressure in the first line 11.
Similarly, when the vehicle is under “restraint,” while going downhill for example, the pressure may also change in lines 11, 12.
These machines M1, M2 are clutched, i.e. engaged, thanks to couplers E1, E2 fed hydraulically by the first and second lines 11, 12. The couplers E1, E2 shown connect the engine blocks of the hydraulic machines to the shafts which pass through them, and make the machines active.
A booster circuit is provided for feeding the lines 11, 12 with oil so as to allow the engagement of the machine M1, M2, and also to compensate for oil leaks. This circuit allows the lines to which it is connected to be held at the low pressure minimal pressure, called the boost pressure. The lines 11 and 12 are therefore always at the boost pressure when the system is activated.
For this purpose, a booster pump 30, which will be called the “pump 30,” is provided. It is connected to a reservoir R by a drainage line 13 and may feed the first and second lines 11, 12 via a booster line 10 in particular.
The booster pump 30 may deliver oil under a pressure of a few tens of bars, substantially equivalent to the low pressure.
The pressurization of the HP and LP lines of the closed loop by the booster circuit allows the activation of the hydraulic machines M1 and M2 via the actuation of the couplers E1 and E2. Conversely, the removal of oil from the closed loop induces a drop of pressure in the lines, which releases the couplers E1 and E2 and frees the machines M1 and M2, which makes them inactive.
According to a preferred feature of the invention, the pump 30 is configured to be able to aspirate oil from the booster line 10 and in particular to discharge it toward the reservoir R via the drainage line 13.
The vacuum is thus accomplished by reversing the direction of operation of the pump 31 and there is no longer a need for a vacuum valve nor a specific vacuum line.
For this purpose, the first and second lines 11, 12 no longer each comprise an autonomous check valve B11, B12 as before. In fact, aspiration in the booster line 10 would lead to the locking of these check valves, which would prevent the oil from returning to the booster line 10.
When hydraulic assistance is required, the device operates conventionally, with activation of the pump 30 to inject oil into the booster line 10, which will then pressurize the first and second lines 11, 12 and if necessary the couplers E1, E2 to engage the machines M1, M2.
On the other hand, when hydraulic assistance is no longer required, the pump 30 reverses its direction of operation, i.e. instead of collecting oil in the reservoir R to inject it into the booster line 10, it collects oil in the first and/or second lines 11, 12 via the booster line 10 and sends it to the reservoir R. Thus, the first and second lines 11, 12 are decompressed and the disengagement of the machines M1, M2 is accomplished thanks to aspiration by the pump 30 of the necessary volume of oil.
The disengagement is accomplished rapidly thanks to the aspiration of the pump 30 which is considered to be more effective than a mere vacuum through opening a vacuum valve.
Depending on the architectures, only the line corresponding to that at low pressure when driving forward and with torque addition, among the two lines 11, 12, is connected to the booster line 10.
More precisely, the vacuum produces cavitations in the cylinders of the hydraulic machines M1, M2. The decompression of the lower pressure line creates dead volumes under the pistons and, due to the rotation of the machines M1, M2, the dead spaces are filled by the high pressure line, which allows the vacuum of the of the higher pressure line as well. When the machines M1, M2 turn, one of them will collect oil in the higher pressure line, toward the low pressure line, where it will be aspirated through the valve. Furthermore, the low pressure line being emptied, the pressure will therefore decrease in both lines 11 and 12 at the same time. Thus the aforementioned dispositions allow, on this particular circuit, reducing the pressure in both lines, even if only one of them is connected directly to the pump. The expression “directly connected” must be understood to signify “without passing through another hydraulic machine” or “connected by an open valve to the line going in the direction of the booster pump.”
This is a voluntary cavitation method, caused in particular by the aspiration of the pump 30, which accelerates the vacuum.
Thus this is a transition from a passive vacuum (stoppage of control of the pump and of the vacuum valve) to an active vacuum, while eliminating a valve (the vacuum valve) and materially eliminating a line (the vacuum line present in the prior art).
Preferably, the pump 30 is fed by an electric unit 31, forming an electric pump unit EPU. A pressure limiter 20 is disposed in parallel with the pump 30, in a conventional manner.
The reversal of the direction of rotation of the electric motor 31 causes the pump 30 to operate in reverse direction. The speed and the duration of activation are functions of the volume of oil to be aspirated and of the features of the device, such as the cylinder displacement.
It is thus necessary to have an EPU 30, 31 available which may operate in both directions of rotation.
According to the invention the booster line 10 is connected to the first and second lines 11, 12, by a low pressure selector valve 72 (an “inverse shuttle valve”). This allows the lower pressure line 11 or 12 to always be boosted (when the vehicle is in reverse or under restraint, the pressures in lines 11, 12 may be reversed).
The selector valve 72 leaves the lower pressure line constantly open and therefore connects this lower pressure line with the booster line 10.
The pressure limiters, grouped in the form of a common assembly designated 71 in
The low pressure selector valve 72 is typically constituted from two check valves back to back, each comprising a sealing element, a ball for example, or a valve with a form suitable for the flow rates and pressures of the system. The sealing element, for example and without limitation a ball or an equivalent means, is housed on a respective seat to block the passage of oil.
The balls or the aforementioned equivalent means are held at a minimum distance from one another by a rigid means, for example a stem, so that one of the two valves is constantly open. The balls or the aforementioned equivalent means, may also be secured to the rigid means.
As soon as pressure is higher on one side, the aforementioned sealing element, a ball for example, or the aforementioned equivalent means, is pressed against the associated seat and blocks communication between the feed line 11, 12 and the booster line 10, thus freeing the opening on the other side between the other feed line 12, 11 and the booster line 10.
In addition, thanks to the rigid means interposed between the two sealing means, plugs or balls, which holds one of the two valves open, there is no risk of blocking the selector valve 72 when the pump 30 is aspirating in the booster line 10 and creates a pressure drop.
Excess pressure in one of the two lines 11, 12, will be discharged by spilling oil into the other line 12, 11.
The valve 70 comprises a cartridge 701 in which are found a pin 711 and a tappet 721. These latter two may slide in relative translation along a longitudinal axis X-X′. More precisely, the tappet 721 is preferably fixed in the body of the cartridge 701, while the pin is movable in translation in the body of the cartridge 701.
The tappet 721 delimits the volume of the cartridge 701 into a first volume V1 fed by the first line 11 and into a second volume V2 fed by the second line 12. The two volumes V1, V2 are not completely independent and may communicate fluidically with one another through an internal channel 722 which is included in the tappet 721.
In addition, the tappet 721 defines, with the cartridge 701, an annular volume Va between said tappet 721 and the cartridge 701. This annular volume Va is always in communication with the booster line 10 and is alternatively in communication with the first or the second volume V1, V2. Thus, even during when the booster pump 10 is aspirating, there is no risk of blockage.
The pin 711 comprises a first end 711a which is suitable for blocking the inner channel 722 in a rest position and for opening it into an operating position. These two positions are obtained by translation of the pin 711 along X-X′. A second end 711b of said pin 711 is in contact with a spring 712 which holds the pin 711 in the rest position. In this rest position, the tapered end 711a of the pin 711 rests against the end of the inner channel 722 of the cylinder 721 which forms a seat 155.
When the inner channel 722 is blocked, the position of the tappet 721 depends on the pressures exerted in the first and second volumes V1, V2:
The pin 711 further comprises a first surface S1 leading into the first volume V1 on which a force is exerted originating from the pressure of the first volume V1. In practice, this first surface S1 corresponding to the surface blocking the inner channel 722. The pin similarly comprises a second surface S2 leading into the second volume V2 and on which a force is exerted originating from the pressure of the second volume V2. In practice, this surface S2 is situated between the volume V2 and a housing 713 of the spring 712.
The first surface S1 is preferably a frusto-conical surface formed on the first end of the pin 71 and engaged in the inner channel 722 of the tappet 721. The second surface S2 is preferably formed from an annular collar protruding from the periphery of the pin 711 in the vicinity of the second end 711b thereof.
Both forces due to the pressure of the fluid present in the lines 11 and 12, are exerted in the same direction and tend to place the pin 711 in the operating position, i.e. to compress the spring 712 and to open the inner channel 722, by moving the pin 711 away from the tappet 722.
Thus, when the force exerted on the pin 711 by the pressure of the fluid is greater than the force of the spring 712, the inner channel 722 opens and the two volumes V1, V2 communicate with one another to allow the excess pressure to be discharged from a line 11, 12 to the other 12, 11. The pin 711 and the spring 712 form the pressure limiter 71 which combines two pressure limiters.
It is therefore understood that the device illustrated in
It is possible to obtain different pressure settings between the pressure threshold existing in the first volume V1 which causes the opening of the relief valve, and the pressure threshold existing in the second volume V2, which causes the opening of the relief valve, by selecting suitable surfaces S1, S2. In practice, given the pressures involved, (for example 400 bars in one line against 30 bars in the other), only one of the two volumes V1, V2 exerts significant force against the spring 713.
This valve 70 which integrates a limiter 71 which acts with a single spring 713 and which integrates a low pressure selector valve 72 allows better compactness of the device than the known devices of the prior art.
According to the embodiment illustrated in
Thus, when the pressure in the line 11 is less than the pressure in the line 12, the washer 732 is pressed against the cylinder 721, while the washer 730 is separated from the cylinder 721. The washer 732 closes the passage communicating with the line 12 as may be seen in
Conversely, when the pressure in the line 11 is greater than the pressure in the line 12, the washer 730 is pressed against the cylinder 721 while the washer 732 is separated from the cylinder 721. The washer 730 closes the passage communicating with the line 11 while the washer 732 being separated from the cylinder 721 allows a connection between the line 12 and the booster line 10.
As may be seen upon examining the appended
Moreover, the device comprises confinement means suitable for applying the pressure coming from the feed line 12 to a limited localized zone of the plug 711, at the second end thereof forming the second biasing surface S2. More precisely here, as may be seen in
The device illustrated in
Still more precisely, as illustrated in
The presence of such dual guide allows the reliability of the device to be improved with respect to the dispositions proposed in the prior document US 2005/0097887. In fact, the presence of the two guides separated by a distance at least equal to the diameter of the seat 155 and preferably greater than five times this diameter, allows avoiding having the plug placing itself in an oblique position with respect to the desired translation direction X-X′.
Moreover, the fact of forming the two plugs of pressure relief valve associated respectively with the two lines 11 and 12 on a common means 711, by disposing the two biasing surfaces respectively on either side of the seat 155, allows a considerable guide distance (typically greater than 5 times the diameter of the seat 155) to be retained, without however imposing a prohibitive longitudinal space requirement. It is understood in fact that, if the device integrates two separate plugs respectively for each pressure relief valve, the cumulative longitudinal space requirement of the two plugs would at least be equal to 10 times the diameter of the seat 155, if it is desired to ensure guidance of each plug with two guide means separated by 5 times the diameter of the seat 155.
According to the appended
Moreover, the passage 702 may serve as a damper for the movement of the plug valve if its cross-section is calibrated to slow the transfer of oil.
It is understood that the stem which forms the pin 711 operates in compression under the biasing of the spring 712.
A second variant embodiment of a distributor and pressure relief device conforming to the present invention will now be described with reference to
The device 70 comprises a body 110 which has three ports 122, 124, 126: two ports 122, 124 which communicate respectively with the lines 11 and 12, and one port 126 which communicates with the booster line 10.
The booster line 10 may be fed with oil by the booster pump 30 until it attains the boost pressure, which makes the machines M1, M2 operational, or the booster line 10 may be aspirated by the booster pump, which makes the machines M1, M2 non-operational. The machines M1 and M2 are of a type which becomes non-operational, or unclutchable, below a pressure threshold in the lines 11 and 12. The selector connects automatically the lower pressure line to the boost, which allows activation or deactivation of the transmission which is smooth and orderly.
The pressure relief device 100 shown in
The device 100 is centred on a longitudinal axis of symmetry O-O. The device 100 is axially symmetrical overall around the axis O-O.
The body 110 is formed from a cartridge suitable for being integrated in any support structure, for example on the casing of a hydraulic motor.
The body 110 is preferably formed by assembling a casing 120 and a cap 112. The cap 112 may be attached to one axial end of the casing 120 by any appropriate means, for example by crimping or preferably by screwing at complementary threads 114. The cap 112 may be equipped with a non-axially-symmetrical shape 113 allowing it to be clamped, as well as a recess 115 suitable for receiving a seal 116 in contact with the support structure. The axial end of the casing 120 may be equipped on its outer surface with a thread 121 allowing assembly of the device 100 on this support structure.
The casing 120 comprises at least three through passages 122, 124, 126 which correspond to the three aforementioned ports.
One of the through passages 126 is formed in the middle portion of the length of the casing 120. More precisely, several openings 126 equally distributed around the axis O-O are preferably provided.
The passages 122 and 124 are formed respectively on either side of the middle passage 126. More precisely, the passage 122 is preferably formed of several openings 122 equally distributed around the axis O-O.
The passage 124 may also be formed from several openings equally distributed around the axis O-O. However, according to the preferred embodiment, for reasons of manufacture and assembly, the passage 124 is formed from an opening which leads axially on the casing 120 to the opposite end of the cap 112.
The casing 120 preferably comprises on its outer surface two annular recesses 127, 128 disposed between the passages 122, 126 and 124, designed to receive respective seals 103, 105 in contact with the support structure and allowing the hydraulic connections provided toward the passages 122, 126 and 124 to be isolated from one another.
The casing 120 comprises, on its inner surface and at the middle passage 126, a narrowed portion 130 which extends axially on either side of the passage 126. The narrowed portion 130 defines respectively on its two axial ends two seats 132, 134 associated with the selector valve 150.
The narrowed portion 130 which forms the two seats 132, 134 may be integrally formed on the inner surface of the casing 120 or be formed from a separate part applied to the surface of the casing 120 and attached by any appropriate means, for example by screwing, crimping or welding.
The two seats 132, 134 are oriented respectively toward the opposite axial ends of the casing 120.
The selector valve 150 has the general shape of a dual-wheel formed from a central cylinder 152 with a constant rotationally symmetrical cross-section, provided on its two axial ends with respective excrescences 154, 156 protruding on its outer surface.
The protrusions 154, 156 form respectively two annular plugs, directed respectively toward the middle portion of the dual-wheel 150, suitable for cooperating with the seats 132, 134 formed on the casing 120.
The outer diameter of the central cylinder 152 is less than the inner diameter of the narrowed portion 130. The outer diameter of the plugs 154, 156, on the other hand, is greater than the diameter of the seats 132, 134.
Thus, when one of the plugs 154, 156 rests on the associated seat 132, 134, the corresponding valve of the selector valve 150 is closed. Conversely, when a plug 154, 156 is separated from the associated seat 132, 134, the corresponding valve of the selector valve 150 is open.
The use of a selector valve 150 comprising a cage 152 on the ends whereof are formed the respective plugs 154, 156 of two selection valves, makes it possible to guarantee a constant distance between the two plugs 154, 156 and consequently allows guaranteeing that when one of the selection valves is closed, the other selection valve is automatically opened.
The cylinder 152 defines an axial through passage designed to receive a plug 162 slidingly and an associated support stem 164 forming a dual relief valve 160. The cylinder 152 also comprises a plurality of radial through openings 158.
The openings 158 allow free filing of the inner volume of the selector valve 152 and the discharge of the fluid during opening of a relief valve, as will be seen later.
The cylinder 152 and the two excrescences 154, 156 may be formed integrally from a single part. As illustrated in
As may be seen in
The plug 162 is formed from an excrescence on one end of the stem 164. The plug 162 is placed facing the seat 155, in the volume of the inner chamber of the cylinder 152.
To allow the assembly of the widened plug 162 on the seat 155, the cylinder 152 preferably comprises an end cap 159 screwed to the end of the cylinder 152 after installation of the plug 162.
The stem 164 emerges axially on the end of the selector valve 150 opposite to the plug 162. The stem 164 and its associated plug 162 are biased toward one axial end of the casing 120 by a spring 170.
Thus, the plug 162 is urged to press against the seat 155.
The spring 170 is interposed on the stem 164, between the excrescence 154 and a stop 172 in the form of a ring carried by the stem 164.
Preferably, the stop 172, 192 is adjustable in position over the length of the stem 164 to define the force exerted by the spring 170 and consequently the setting of the opening pressure of the relief valve.
The stop 172 may be attached in position on the stem 164 by any appropriate means, for example by screwing or crimping or welding.
As indicated previously the excrescences 154, 156 and the cylinder 152 are advantageously formed of at least two parts, preferably of three parts, initially separated and assembled by any appropriate means, for example by screwing or crimping or welding, as may be seen in
Even more precisely, the body of the selector valve 152 comprises radial through passages 157 formed on its axial end outside the seat 155, between the seat 155 and a sealing segment 166 carried by the plug 162.
Moreover, the axial end of the plug 162 directed toward the seat 155 is preferably in the form of a cone frustum 165. More precisely, the frusto-conical surface 165 preferably comprises two axially juxtaposed portions 163 and 164 having different taper ratios.
The portion 163 of this frusto-conical surface 165 rests on the seat 155.
The portion 163 of this frusto-conical surface 165 which is accessible on the inside of the inner chamber of the selector valve 150 is subjected to the pressure coming from the passage 122. It is this portion 163 of the frusto-conical surface 165 which defines the force resulting from the pressure of the passage 122 allowing the force of the spring 170 to be overcome and therefore opening the relief valve in the event of excess pressure in the passage 122.
On the other hand, the portion 164 of the frusto-conical surface 165 which is disposed on the outside of the seat 155 is subjected to the pressure coming from the passage 124 via the aforementioned through passages 157. It is this portion 164 of the frusto-conical surface 165 which defines the force resulting from the pressure of the passage 124 allowing the force of the spring 170 to be overcome, and therefore opening the relief valve in the event of excess pressure in the passage 124.
As may be seen in
Moreover, the widened portion of the plug 162 is guided in translation along the axis O-O of the device in a complementary portion of the body and has here a seal or annular seal segment 166.
The sealing is provided by cooperation between the surface 163 and the seat 155, on the one hand, and between the segment 166 and the complementary cylindrical surface which surrounds it on the other hand. Thus by analogy with
As may be seen on examining
Moreover, the device comprises confinement means suitable for applying the pressure of the port 124 to a localized limited zone of the plug 162. More precisely, these confinement means are formed by the seal or annular seal segment 166 and by the channels 157. Thus the pressure that prevails in the feed line associated with port 124 applies only to the face of the plug 162 situated outside the seat 155, more precisely at the surface delimited between the seat 155 and the segment 166.
To allow free displacement of the plug 162 in the housing formed by the cap 159 applied to the end of the cylinder 152, longitudinal channels 151 are preferably provided which form a purge channel and connect this internal housing of the selector valve to the port 126.
The purge channel 151 has a function equivalent to that of the channel 702 in
To assemble the pressure relief device previously described, the procedure is essentially as follows.
First of all, the plug 162 and its stem 164 equipped with the spring 170 and the stop 172, are assembled to the cylinder 152 of the selector valve without the excrescence 154, the plug 162 being place facing the seat 155. The stop 172 is adjusted in position for the desired setting. The closure cap 159 is attached to the body of the selector valve 152.
The subassembly of the relief valve and selector valve thus formed is introduced into the casing 120 through the end thereof opposite to the cap 112. The excrescence 154 is attached to the cylinder 152 of the selector valve.
To this end, the outer surface of the cylinder 152 of the selector valve may be provided with gripping shapes accessible by the passages 126 to facilitate assembly.
Then the cap 112 is attached to the end of the casing 120. The seals are placed in their respective recesses.
The device illustrated in
Even more precisely, as illustrated in
As may be seen in
As indicated previously for the first embodiment of
It is understood that the stem 164 associated with the plug 162 works in traction under the biasing of the spring 170.
The operation of the relief device is essentially the following:
At rest, in the absence of pressure on the port 126 and therefore in the booster line 10, and consequently on the ports 122, 124 and therefore in the feed lines 11, 12, the selector valve 150 is capable of free movement in the casing 120 facing the seats 132, 134. The plug 162 biased by the spring 170 rests on the seat 155 and the relief valve is consequently closed.
In operation, during the activation of the booster pump 30 and of a selection of the direction of rotation of the machine M1, one of the ports 122, 124 is subjected to a high pressure while the other portion 124, 122 is subjected to a low return pressure.
The selector valve 150 is thus impinged upon by the high pressure.
If, as illustrated in
As may be seen in
The operation of the selector valve is identical during the commissioning or the deactivation of the hydraulic machines, by the use of the booster pump in the sense of causing oil to enter the closed loop or to have oil leave the closed loop.
When the pressure in a line 11, 12, exceeds the set threshold of the relief valves defined by the spring 170, this excess pressure applied to the plug 162 ensures the opening of the relief valve, as illustrated in
In
A person skilled in the art will understand that the implementation conforming to the invention allows all the functions to be integrated into a component in the form of a cartridge while allowing simple and reliable, as well as independent adjustment of the setting of each relief valve.
The invention may thus be integrated or juxtaposed with one of the machines M1, M2.
Regardless of the embodiment, a device is obtained in which the engagement and disengagement of the machines M1, M2 is controlled only by the booster pump 30 and the reversal of its direction of operation. It is no longer necessary to have recourse to electrically controlled valves.
Regardless of the aspect of the invention, the disengagement of the hydraulic machines M1, M2 is accomplished thanks to circulation, in reverse of boosting operation, of the flow through the pump, typically thanks to the aspiration of the booster pump 30. This circulation may be passive or active. Several types of pumps may be used.
Recall that the preceding figures show a pump 30 driven by an electric motor 31 capable of turning in both directions, but this is in no way limiting.
As a variant, the booster pump may be a variable displacement pump. It is then no longer necessary to have a pressure limiter in parallel with the booster pump. This known type of pump accomplishes a slaving of the displacement of the pump with respect to a set pressure, via a feedback line and a set spring. This type of pump is equivalent to the juxtaposition of a fixed displacement pump and of a pressure limiter.
The booster pump may also be a reverse displacement pump. Such a pump always turns in the same direction, but a change of displacement toward a negative displacement causes aspiration.
The aforementioned reverse displacement pump may be driven by an axle of the vehicle (with a reducer and a coupler, of the disk clutch type, if necessary).
The hydraulic machines M1, M2 are preferably radial piston machines as shown schematically for example in
These machines convert hydraulic energy into mechanical energy due to the variation in displacement of the pistons when they follow the lobed cam.
Such machines M1, M2 have relatively low rotation speeds but have high torque.
Such machines M1 and M2 are preferably placed in a vehicle so as to turn at the speed of the wheels that they must drive, without overdrive or reduction of speed. If there is one machine per axle, this means the average speed of the two wheels of the axle, via a differential or equivalent system.
A casing (not shown) protects the assembly. The casing may serve as a reservoir R. The reservoir R is substantially at atmospheric pressure. It may be connected via breathers, filters or valves, which may create a very slight pressure difference with respect to the outside.
Naturally the present invention is not limited to the embodiments which have just been described, but extends to all variants conforming to its spirit.
According to other advantageous features of the invention:
Thanks to the activation of the pump in aspiration in the booster circuit, the second transient phase is improved by accelerating the vacuum of the first and second lines. The circulation, in the reverse direction of booster operation, of flow through the pump, may be passive (extinction of the pump and decompression of the lines) or active (control of the pump).
Moreover, the device conforming to the present invention in the form of an autonomous cartridge suitable for being attached, for example by screwing, in a complementary housing formed in a support body, was described previously.
As a variant, as illustrated in
The closure of the housing which receives the selector valve 72, 150 and the pressure relief valve 71, 160 with a removable cap 112 allows simple adjustment of the threshold pressure for opening the relief valves. It is in fact sufficient to withdraw the cap 112 to gain access to the adjustment elements of the spring(s) 70, adjust them, then replace the cap 112.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1500495 | Mar 2015 | FR | national |
| 1555295 | Jun 2015 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/076491 | 11/12/2015 | WO | 00 |
