FR3010754A1 - HYDRAULIC CONTROL SYSTEM OF NORMALLY CLOSED CLUTCH - Google Patents

Abstract

Hydraulic implementation system (1) for controlling a clutch (2) normally closed; the hydraulic implementation system (1) has: a hydraulic actuator (4) mechanically connected to disks of the clutch (2); a reservoir (5) containing a hydraulic fluid (6) at atmospheric pressure; a reversible pump (7) which connects the reservoir (5) to the hydraulic actuator (4); an electric motor (8) which drives the reversible pump (7); a unidirectional check valve (9), which valve is interposed between the reservoir (5) and the hydraulic actuator (4) and only allows a hydraulic fluid flow (6) to the hydraulic actuator (4); and a valve (10) of maximum unidirectional pressure, which valve is interposed between the reservoir (5) and the hydraulic actuator (4), it is connected in parallel with the non-return valve (9), it allows only a flow of hydraulic fluid (6) towards the reservoir (5) and has an opening pressure threshold greater than the nominal pressure of the hydraulic fluid (6) inside the hydraulic actuator (4).

Description

TECHNICAL FIELD The present invention relates to a hydraulic implementation system for controlling a normally closed clutch. a clutch generates a closing thrust to maintain one or more compressed friction discs and thereby allows transmission of torque through the clutch (closed clutch); furthermore, the system for implementing a clutch generates an opening thrust to separate the friction discs and therefore cancel the torque transmission through the clutch (open clutch) .The clutch implementation system can be of normally closed type, that is, in the absence of external actions (for example when the vehicle is stopped and parked) the clutch is closed, in which case the operating system generates the driving force. It is closed by one or more closing springs (whose elastic force never fails) and generates the opening thrust by means of a single acting actuator acting against the closing springs. The implementation system of the clutch is then active in the opening direction (in which the actuator acts) and passive in the closing direction (in which the closing springs act).

The known hydraulic systems used for the control of a normally closed clutch have the disadvantage of being relatively bulky and expensive and therefore their installation is particularly problematic in vehicles of small dimensions in which the space available to them in the engine compartment is reduced. SUMMARY OF THE INVENTION The object of the present invention is to provide a hydraulic implementation system for the control of a normally closed clutch, which hydraulic system of implementation is free from the drawbacks described above and it is in particular of easy and economic realization. According to the present invention, a hydraulic operating system for controlling a normally closed clutch is provided as claimed in the appended claims. SUMMARY DESCRIPTION OF THE DRAWINGS The present invention will now be described with reference to the appended drawing which illustrates an example of implementation that is in no way limiting; in particular, the appended figure is a schematic view of a hydraulic implementation system for controlling a normally closed clutch made in accordance with the present invention. PREFERRED EMBODIMENTS OF THE INVENTION In FIG. 1, indicated by 1 is indicated in its complex, a hydraulic operating system for controlling a clutch 2 normally closed. The clutch 2 (of known type) comprises a set of discs composed of a plurality of driving discs and a plurality of driven discs interposed with the driving discs. The implementation system 1 comprises at least one closing spring 3 which generates constantly (that is to say without any interruption) a closing thrust which tends to compress between them the driving disks and the disks conducted to determine the torque transmission through the clutch 2 (clutch closed). The implementation system 1 further comprises a hydraulic actuator 4 (in particular a hydraulic cylinder with a single effect) which can be controlled to generate, when necessary, an opening thrust which tends to separate the driving discs from each other. the disks conducted to interrupt torque transmission through clutch 2 (clutch open). The clutch 2 is normally closed, that is to say in the absence of the intervention of the hydraulic actuator 4 the closing spring 3 keeps the clutch 2 in its closed condition. Consequently, the system 1 for implementing the clutch 2 is active in the opening direction (in which the hydraulic actuator 4, which must be actively controlled, is active) and passive in the closing direction ( in which acts the closing spring 3 which does not require any activation). The hydraulic implementation system 1 comprises a reservoir 5 containing a hydraulic fluid 6 (normally mineral oil) at atmospheric pressure, a reversible pump 7 (that is to say capable of pumping the hydraulic fluid 6 in both directions according to its direction of rotation) which connects the reservoir 5 to the hydraulic actuator 4 to transfer the hydraulic fluid 6 from the tank 5 to the hydraulic actuator 4 and vice versa, and an electric motor 8 which drives the reversible pump 7 in both ways. A unidirectional check valve 9 which only allows a flow of hydraulic fluid 6 from the tank 5 to the hydraulic actuator 4 is interposed between the tank 5 and the hydraulic actuator 4; in other words, the non-return valve 9 is a unidirectional valve 10 through which the hydraulic fluid 6 can flow in only one direction and therefore the non-return valve 9 completely blocks the flow of hydraulic fluid to the reservoir 5. In addition, a valve 10 of maximum unidirectional pressure is interposed between the tank 5 and the hydraulic actuator 4, which valve is connected in parallel with the non-return valve 8, it only allows a hydraulic fluid flow 6 of the actuator 4 to the tank 5 and has an opening pressure threshold greater than the nominal pressure of the hydraulic fluid 6 inside the hydraulic actuator 4. In other words, the maximum pressure valve 10 is a pressure-controlled unidirectional valve (that is, it opens only when the pressure upstream of the valve 10 of maximum pressure exceeds the threshold of opening pressure ) through which the hydraulic fluid 6 can flow only in a single direction and therefore the maximum pressure valve 10 completely blocks the flow of hydraulic fluid 6 to the hydraulic actuator 4. Consequently, through the maximum pressure valve 10 the hydraulic fluid 6 can flow only to the reservoir 5 and only when the pressure upstream of the maximum pressure valve 10 is greater than the opening pressure threshold (which as has been said previously, is larger than the nominal pressure of the hydraulic fluid 6 inside the hydraulic actuator 4). According to a preferred implementation embodiment illustrated in the appended FIGURE, the non-return valve 9 and the maximum pressure valve 10 are interposed between the reservoir 5 and the reversible pump 7, that is to say they are arranged upstream of the reversible pump 7. According to a different mode of implementation not illustrated, the check valve 9 and the valve 10 of maximum pressure are interposed between the reversible pump 7 and the hydraulic actuator 4, that is to say they are arranged in downstream of the reversible pump 7. According to a preferred mode, but not binding, implementation, interposed between the reversible pump 7 and the hydraulic actuator 4 is provided a volume 11 damping. In other words, the damping volume 11 is constituted by a chamber of 20 dimensions (that is to say of internal volume) calibrated which must be previously filled by the hydraulic fluid 8 before the hydraulic fluid 8 can fill under pressure the hydraulic actuator 4. The function of the damping volume 11 (optionally mountable) is to reduce the volume / pressure peaks generated by the reversible pump 7 and thereby improve the controllability of the hydraulic system of implementation. Generally, the damping volume 11 is sized to project according to the volume of the hydraulic actuator 4, depending on the section and the length of the connecting channels, and depending on the compressibility of the hydraulic fluid 6. According to a preferred mode, but not binding, of implementation, there is provided a discharge element 12, which element is interposed between the tank 5 and the reversible pump 7 and is provided with a passage opening which is always open and has a dimension calibrated and very small. Preferably and as illustrated in the appended FIGURE, the evacuation element 12 is independent of the non-return valve 9 of the maximum pressure valve 10 and is connected in parallel with the non-return valve 9 and the maximum pressure valve 10 . Alternatively, the discharge element 12 is integrated in the check valve 9 or in the valve 10 maximum pressure. According to a preferred embodiment, the evacuation element 12 consists of a calibrated nozzle. Finally, a control unit 13 is provided, which unit directly drives the electric motor 8 to control the position of the clutch 2; of course, the control unit 13 is connected to a plurality of sensors (in themselves known and not illustrated) which measure the parameters of the system 1 implementation. In use, to open the clutch 2, the control unit 13 controls the electric motor 8 in a first direction so as to supply the hydraulic fluid 6 under pressure from the reservoir 5 to the hydraulic actuator 4 through the valve 9 non-return and to close the clutch it controls the electric motor 8 in a second direction opposite the first direction so as to return hydraulic fluid 6 pressure from the hydraulic actuator 4 to the tank 5 through the valve 10 pressure Max. When the electric motor 8 (and thus the reversible pump 7 which is mechanically connected to the electric motor 8) rotates in the first direction, the reversible pump 7 draws the hydraulic fluid 6 from the reservoir 5 through the non-return valve 9 and feeds it. by this hydraulic fluid 6 io pressure to the hydraulic actuator 4 (passing through the volume 11 damping); therefore, the hydraulic actuator 4 extends and it therefore determines the gradual opening of the clutch 2. When the electric motor 8 (and therefore the reversible pump 7 which is mechanically connected to the electric motor 8) turns in the In the second direction, the reversible pump 7 sucks the hydraulic fluid 6 from the hydraulic actuator 4 (passing through the damping volume 11) and consequently it returns the hydraulic fluid 6 into the tank 5 through the valve 10 maximum pressure; consequently, the hydraulic actuator 4 is empty and thereby determines the progressive closure of the clutch 2 by the effect of the action of the closing spring 3. In this situation, the reversible pump 7 increases the pressure of the hydraulic fluid 6 to exceed the opening pressure threshold of the maximum pressure valve 10, thereby determining the opening of the maximum pressure valve 10 itself.

When the electric motor 8 (and consequently the reversible pump 7 which is mechanically connected to the electric motor) is stopped, the hydraulic fluid contained in the hydraulic actuator 4 is physically prevented from returning to the reservoir 5 either by the check valve 9 (because the non-return valve 9 never allows the hydraulic fluid 6 to flow to the tank 5), or by the valve 10 of maximum pressure (because the valve 10 pressure maximum opens only if the pressure exceeds the opening pressure threshold which is greater than the nominal pressure of the hydraulic actuator 4). In other words, with the electric motor 8 stopped (ie at the pump 7 reversible when stopped) the position of the hydraulic actuator 4 (and consequently the position of the clutch 2) is irreversible (that is that is, it is "frozen"). A function carried out by the non-return valve 9 is to drastically reduce (ie substantially cancel) hydraulic fluid leaks within the reversible pump 7 when the reversible pump 7 is stopped. and the hydraulic actuator 4 contains hydraulic fluid 6 under pressure; such hydraulic fluid leaks within the reversible pump 7 would otherwise be unavoidable due to the high pressure gradient existing between the hydraulic actuator 4 and the reservoir 5 and are substantially eliminated by the presence of the anti-backflow valve 9. return which blocks the return of the hydraulic fluid 6 of the hydraulic actuator 4 to the tank 5. An additional function carried by the non-return valve 9 is to force the passage of the hydraulic fluid 6 through the valve 10 of maximum pressure when the reversible pump 7 is actuated to empty the hydraulic actuator 4. The function rerouted by the valve 10 of maximum pressure is to render irreversible the hydraulic system 1 implementation in the absence of actuation of the reversible pump 7; in other words, thanks to the presence of the maximum pressure valve 10, with the electric motor 8 stopped (that is to say pump 7 reversible at rest) the position of the hydraulic actuator 8 (and by therefore the position of the clutch 2) is irreversible (that is, it is "frozen"). Indeed, when the reversible pump 7 is stopped and the hydraulic actuator 4 contains hydraulic fluid 6 under pressure, the pressure required to close the clutch 2 is internally balanced with the valve 10 of maximum pressure by the spring force valve 10 of maximum pressure itself; in this way, the fluid 6 hydraulic pressure, in the absence of control of the electric motor 8, can not flow through the valve 10 maximum pressure ensuring the maintenance of the current position of the clutch 2. The function of the evacuation element 12 is to guarantee the slow depressurization of the hydraulic actuator 4 in the event of malfunction (for example by electrical failure) of the electric motor 8 and thus to guarantee the (slow) return of the clutch 2 in its closed position. Moreover, because of the presence of the evacuation element 12, the (slow) depressurization of the hydraulic implementation system 1 is always guaranteed so that in the case of a workshop assistance intervention always exists. the guarantee that in the hydraulic system 1 implementation of pressures potentially dangerous for an operator are not present. The hydraulic system 1 implementation described above 5 has many advantages. In the first place, the hydraulic implementation system 1 described above is particularly compact and economical, since it does not include any hydraulic fluid accumulator 6 under pressure and does not include any solenoid valve; indeed, the entire system 1 of hydraulic implementation is controlled only by controlling the electric motor 8 of the reversible pump 7. In addition, the hydraulic implementation system 1 described above consumes energy only during the displacement of the clutch 2 (that is to say when the clutch 2 changes its position), since the maintenance of the current position of the clutch 2 (that is to say, keep the clutch stopped) always occurs with pump 7 reversible at rest and therefore without any energy expenditure. Finally, the hydraulic implementation system 1 described above is particularly reliable over time, since it is almost exclusively composed of passive components which are essentially of high reliability.

Claims (8)

CLAIMS1) Hydraulic implementation system (1) for the control of a clutch (2) normally closed, the hydraulic implementation system (1) comprises: a hydraulic actuator (4) mechanically connected to the clutch disks (2); a reservoir (5) containing a hydraulic fluid (6) at atmospheric pressure; a reversible pump (7) which connects the reservoir (5) to the hydraulic actuator (4) to transfer hydraulic fluid (6) from the reservoir (5) to the hydraulic actuator (4) and vice versa; and an electric motor (8) which actuates the reversible pump (7) in both directions; the system (1) for hydraulic implementation is characterized in that it comprises: a unidirectional check valve (9), which valve is interposed between the reservoir (5) and the hydraulic actuator (4) and allows only a fluid flow (6) hydraulic from the tank (5) to the hydraulic actuator (4), and a valve (10) unidirectional maximum pressure, which valve is interposed between the reservoir (5) and the actuator ( 4) is connected in parallel with the non-return valve (9), allows only a fluid flow (6) hydraulic from the hydraulic actuator (4) to the reservoir (5) and has an opening pressure threshold greater than the nominal pressure of the hydraulic fluid (6) inside the hydraulic actuator (4). 2) System (1) of hydraulic implementation according to claim 1, wherein the check valve (9) and the check valve (10) of maximum pressure are interposed between the reservoir (5) and the pump (7) reversible , that is to say they are arranged upstream of the pump (7) reversible. 3) System (1) for hydraulic implementation according to claim 1 or 2 and comprising a member (12) for evacuation, which element is interposed between the reservoir (5) and the pump (7) io reversible and is provided a passage opening which is always open and which has a calibrated dimension. 4) System (1) for hydraulic implementation according to claim 3, wherein the element (12) of discharge is integrated with the valve (9) anti-return valve or the valve (10) of maximum pressure. 15 5) System (1) for hydraulic implementation according to claim 3, wherein the element (12) of discharge is independent of the check valve (9) and the non-return valve (10) maximum pressure and is connected in parallel with the non-return valve (9) and the maximum pressure valve (10). 20 6) System (1) for hydraulic implementation according to claim 3, 4 o 5, wherein the element (12) of evacuation consists of a calibrated nozzle. 7) System (1) of hydraulic implementation according to one of claims 1 to 6 and comprising a volume (11) damping 25 interposed between the pump (7) reversible and the actuator (4) hydraulic. 8) System (1) of hydraulic implementation according to one of claims 1 to 7 and comprising a unit (13) control, which unit for opening the clutch (2) drives the motor (8) electric in a first direction so as to feed the hydraulic fluid (6) under pressure from the reservoir (5) to the hydraulic actuator (4) through the nonreturn valve (9) and to close the clutch (2) it controls the engine (8) electrical in a second direction opposite to the first direction so as to rotate hydraulic fluid (6) pressure of the hydraulic actuator (4) to the reservoir (5) through the valve (10) maximum pressure lo.