EP3080478A1 - Device for regulating the rotation of a shaft, in particular in the automobile field - Google Patents

Abstract

The invention concerns a device (10) for regulating the rotation of a shaft subjected to N torque fluctuations per revolution, said device comprising: - a cam (12) provided with an axis of rotation (14), intended to be rigidly connected to the shaft such that the axis of rotation of same coincides with that of the shaft, said cam (12) having N lobes (13), - a control tappet (16) carried by a pin (18) actuated with time phase difference of T/2N relative to a tappet 15 intended for the operation of a member of the engine. This tappet (16), which is mobile in translation along the pin (18) of same, is held pressed against the cam (12) by a bearing system configured to exert a regulated force on said tappet (16) during the rotation of the cam (12).

Description

 DEVICE FOR REGULATING THE ROTATION OF A TREE, IN PARTICULAR IN THE AUTOMOBILE DOMAIN

The invention relates to a device for regulating the rotation of a shaft, particularly in the automotive field.

 In mechanics, the rotation of some trees can be acyclic. This is the case in particular for camshafts subjected to dynamic torques of variable amplitude, the variations of which can be significant.

 Thus, in the field of the automobile, a camshaft is for example used to actuate the fuel injection pump of a heat engine. Such an injection pump may in particular comprise a fuel compression chamber directly actuated by the combined action of a cam coming to lift a piston to open the chamber and a return spring that lowers the piston to close the chamber when the raising of the cam becomes minimal again. Such a system is relatively simple but generates rotational irregularities of the camshaft. These irregularities of rotation remain moderate as long as the injection pressure of the fuel is moderate. When this injection pressure becomes high, for example in the case of a diesel engine, the mechanism of the pump exerts a torque of greater amplitude on the camshaft, which results in an irregularity in rotation or acyclism of the tree. When this acyclism is important, a degradation of the reliability of the drive system of the shaft, by chain or by belt, can be observed. Reliability can then be restored by increasing the tension of the chain or belt, resulting in noises and vibrations that are not well received by vehicle users.

Another solution is to reduce acyclism by compensation systems. Some existing compensation systems include a cam, sometimes referred to as a cam follower, whose function is to counterbalance the irregular forces experienced by the camshaft. In existing compensation systems, a cam of this type is subjected to a constant force exerted by a resilient means of spring type, as described for example in the document FR 2,688,563 A1. Such a compensation system however has the disadvantage of generating permanent friction on the shaft to cams due to the constant force applied by the resilient means against the shaft. This causes an increase in fuel consumption under all operating conditions of the engine, including when the acyclism is low, for example in phases where the injection pump acting on the camshaft does not generate significant torque fluctuations. Other compensation systems comprise a mass connected to the camshaft by an elastic element such as rubber. This type of passive system, however, is difficult to adjust and ages poorly, which can lead to an increase in acyclism.

 There is therefore a need to reduce the acyclism of a shaft, especially a camshaft, without exerting permanent friction on the shaft, and reliably throughout the life of the tree.

 For this purpose, the subject of the invention relates to a device for regulating the rotation of a shaft subjected to N torque fluctuations per revolution of rotation carried out in a rotation time T, said device comprising:

 a cam provided with an axis of rotation and intended to be secured to the shaft so that its axis of rotation coincides with the axis of the shaft, said cam having N lobes,

 a first pusher for operating a motor member and carried by an axis having a radial or longitudinal orientation with respect to the axis of the cam,

 characterized in that it comprises:

 a second regulation push-button carried by an axis actuated in phase shift by a time T / 2N relative to the first pusher per revolution of rotation, said regulation pusher being movable in translation in the direction of this axis, said regulation pusher being maintained in abutment against the cam by a support system exerting a force on said thrust control towards the cam, said support system being shaped to regulate this force during the rotation of the cam.

 The regulating device of the invention thus makes it possible to regulate the force exerted by the elastic means during the rotation of the cam, in other words during the rotation of the shaft.

It is thus possible to make an adjustment of the force during rotation as a function of the amplitude of the torque fluctuation N undergone by a tree during its rotation. This fluctuation of torque N is generated by an event undergone by the shaft during its rotation and likely to generate acyclism via the support of the first pusher. Such an event may be the actuation of a system by one or more cams carried by the shaft. However, the regulating device according to the invention is not limited to a regulation of the rotation of the camshafts and can be used for a regulation of the acyclism of any rotating shaft subjected to irregular forces, for example a camshaft of a fuel injection system of a heat engine or a camshaft of a gas intake system of a heat engine. The invention is not limited to a particular number N of events. However, according to the manufacturing limitations of the cam, this number N can be from 1 to 6, for example from 1 to 4.

 The regulating pusher of the device according to the invention is actuated in phase shift of a time of T / 2N relative to the first pusher. This phase shift in T / 2N time may result from the relative positions of the axes of the pushers or the actuation of the two pushers. The phase shift in time can for example be obtained by an angular phase shift of π / Ν between the axis of the regulating pusher and the axis of the first pusher when these two axes are in the same radial or longitudinal plane with respect to the axis. rotation of the cam. This phase shift can also be obtained by means of appropriate actuation of the regulating pusher when the axes of the first and second pushers are not in the same plane, for example when one of the axes extends longitudinally with respect to the axis of rotation of the cam and the other axis extends radially relative to this axis. This means of actuation can thus be arranged to actuate the regulation pushbutton with a phase shift in time of T / 2N with respect to the actuation of the first pushbutton.

 Advantageously, the support system may comprise a resilient means shaped to exert a bearing force on said regulating pusher in the direction of the cam and means for regulating the force exerted by the elastic means on the cam. The regulating means may in particular comprise a stop element having a variable stiffness.

Advantageously, the regulation device according to the invention can make it possible to apply a force of variable amplitude, in particular of continuously, during the rotation of the shaft to compensate for torque fluctuations of variable amplitude and to adjust the amplitude of this effort to the amplitude of the fluctuation undergone.

 For this purpose, the control means may comprise a control means capable of modifying the force exerted by the support system, for example able to modify the stiffness of the stop element, as a function of a fluctuation of torque. N expected and / or observed. This can make it possible to improve the regularization of the rotation of the tree by evaluating the amplitude of the force to be applied according to the expected and / or observed torque fluctuation.

 This control means may for example comprise:

 processing means arranged to generate a control signal SN of the regulation means as a function of CN data characteristic of a torque fluctuation N experienced by a shaft equipped with a regulating device according to the invention,

means for transmitting the control signal SN to the regulating means of the regulating device, for example a stepping motor or a solenoid valve of the regulating means.

 This control means may for example include or be integrated in one or more processors, for example a microcontroller, a microprocessor, a DSP (the "Digital Signal Processor"), or other. It can in particular be part of a vehicle management system or not.

 For example, the processing means may comprise or be integrated in a processor, for example a microcontroller, a microprocessor, a DSP (of the English 'Digital Signal Processor'), or other.

 The transmission means may be an output port, an output pin or the like.

 The control means may optionally comprise means for receiving CN data characteristic of a torque fluctuation N experienced by a shaft, for example an input port, an input pin or the like.

The invention is not limited by the form and nature of the control signal. The latter may be a signal whose value will apply a voltage and / or a current. For example, in the case of a shaft carrying cams actuating a fuel injection device of a heat engine, data characteristic of a torque fluctuation N may comprise:

 the speed and / or the load of the heat engine or any other suitable parameter, such as for example any piloting parameter of the fuel injection device, or

 the output pressure of the fuel injected by the injection device.

 By way of example, the control means may allow the application of a force generating a torque of amplitude equal to or less than the amplitude of a fluctuation of torque N, this force being applied with a phase shift such as relative to the fluctuation N, that the torques applied on the shaft, namely the torque generating the fluctuation N and the torque exerted by the regulating device, compensate themselves at least in part, thus reducing the acyclism of the shaft.

 Advantageously and in a nonlimiting manner, the regulation means of the regulating device can comprise:

 a piston with controlled displacement bearing against said elastic means and movable in a direction parallel to the axis of the regulating pusher,

 displacement means of the displacement piston,

 means for controlling the displacement means during rotation of the cam.

 This arrangement has the advantage of allowing a simple regulation of the force exerted by the regulating pusher on the cam. The amplitude of the force applied will thus depend on the position of the displacement piston and the stiffness of the elastic means.

Advantageously and in a nonlimiting manner, the regulating device may comprise a body inside which the piston with controlled displacement and the elastic means are movably mounted in translation along the axis of the regulating pusher, the regulation pusher being located at outside said body, the elastic means comprising a side in contact and / or integral with the axis of the regulating pusher and an opposite side in contact and / or integral with the controlled displacement piston. In other words, the elastic means is located between the regulating pusher and the displacement piston. It then suffices to move the displacement piston in the direction of the pusher to increase the force exerted by the regulating pusher on the cam or to move the displacement piston to the control pusher to reduce this effort.

 In a particular embodiment, the body may comprise the displacement piston and another piston movable in translation integral with one end of the axis of the regulating pusher, the elastic means being situated between these two pistons and being in contact with each other. and / or solidarity with each of them.

 The amplitude range of the force that can be exerted by the regulating pusher on the cam will therefore depend on the displacement amplitude of the displacement piston and the stiffness or the compressive strength of the elastic means.

 In all embodiments, the elastic means may be a simple spring, for example helical, in particular metal, of stiffness determined according to the range of amplitude of effort desired. The invention is however not limited to this embodiment and other elastic means are conceivable.

 According to a particular embodiment, the displacement means of the displacement piston can be mechanical, for example a mechanical jack. The control means may then comprise an electric motor, for example a stepping motor.

 According to another particular embodiment simple to implement, the displacement means of the displacement piston can be hydraulic.

 The control means may then optionally comprise a solenoid valve or a circuit in fluid communication with a fluid whose pressure varies as a function of a torque fluctuation N.

The hydraulic displacement means may comprise a variable volume chamber filled with a fluid, this chamber comprising a movable wall connected to or formed by the controlled displacement piston. This variable volume chamber may in particular be integrated in the body receiving the displacement displacement piston, the latter forming one of the walls of the chamber. The hydraulic displacement means then operates in a manner similar to a hydraulic cylinder. This arrangement has the advantage to be compact and simple. By acting on the amount of fluid present in the chamber, it is thus possible to move the controlled displacement piston and increase or reduce the force exerted by the regulating pusher on the cam.

 Alternatively, the hydraulic displacement means may be a hydraulic cylinder.

 Another object of the invention relates to a shaft carrying at least one cam intended for the actuation of a member, in particular of fuel injection members of a motor vehicle engine, characterized in that it comprises at least one regulating device according to the invention.

 The member actuated by the cam may be a valve closing a fuel injection chamber of a fuel injection device, in particular a fuel injection pump.

 Another subject of the invention relates to a fuel injection device for a motor vehicle engine, comprising a shaft carrying at least one actuating cam of a fuel injection pump, said shaft being equipped with a regulating device according to the invention.

 Advantageously, when the regulating means of the regulating device comprises:

 a piston with controlled displacement bearing against said elastic means and movable in a direction parallel to the axis of the regulating pusher,

 a means for hydraulic displacement of the controlled displacement piston supplied with fluid,

 means for controlling the hydraulic displacement means during the rotation of the shaft,

 the hydraulic displacement means, for example a variable volume chamber thereof, may be supplied with fluid:

 by a fluid circuit independent of the injection device, for example an oil circuit, or

 by a fuel circuit in fluid communication with a fuel injection chamber of the injection device.

In the first case, the amplitude of the torque applied by the regulating device on the shaft can be regulated by means of a solenoid valve controlling the quantity of fluid supplying the medium. hydraulic, this solenoid valve may itself be driven by the aforementioned control means.

 In the second case, the amplitude of the torque applied by the regulating device on the shaft is then directly a function of the pressure of an injection chamber of the injection device because of the fluid communication between the device of the injection device. injection and the chamber of the regulating device. Regulation of the compensation can thus be obtained in a simple manner, possibly without control means and without regulation solenoid valve. Piloting means and solenoid valves may however be used to connect the variable volume chamber successively to different fuel injection chambers.

 The invention also relates to a motor vehicle comprising a camshaft according to the invention or an injection device according to the invention.

 The invention is now described with reference to the appended non-limiting drawings, in which:

 FIG. 1 is a schematic representation of a regulating device according to one embodiment of the invention,

 - Figure 2 shows an operating diagram of a control means of a control device according to the invention.

 Figure 1 shows schematically a control device 10 according to one embodiment of the invention.

 The regulating device 10 comprises in particular a cam 12 of axis of rotation 14. The cam 12 is intended to be secured to a tree whose acyclism is desired to reduce. The cam 12 is secured to this shaft so that its axis of rotation 14 coincides with the axis of the shaft. In the figure, the tree is not represented for more map. The cam 12 comprises N lobes 13, with N = 4, namely as many lobes N as events generating a fluctuation of the torque experienced by the shaft during rotation, this fluctuation resulting in acyclism. Thus, in the example, the cam comprises 4 lobes to compensate for 4 torque fluctuations per rotation of a shaft.

The regulating device 10 comprises a first pusher 15 intended for the operation of an engine member, here a pump 1 and carried by an axis 15a having a radial orientation in the example shown. The regulating device 10 also comprises a second regulating pusher 16 carried by an axis 18 radial to the axis of rotation of the cam, in other words perpendicular to the axis of rotation 14 of the cam 12 in the example shown. The axis 18 of the regulation pusher 16 is out of phase by an angle π / Ν with respect to the axis 15a of the first pusher 15, which results in an actuation of the regulation pusher 16 in phase shift of a time of T / 2N relative to the first pusher 15 per revolution of the cam, T being the duration of a rotation of the shaft.

 This regulating pusher 16 is movable in translation in the direction of its axis 18. The regulating pusher 16 is further held in abutment against the cam 12 by an elastic means 20 exerting a force on the regulating pusher 16 in the direction of the In the example, the elastic means 20 is a simple metal coil spring working in compression.

 The regulation device 10 also comprises a means 22 for regulating the force exerted by the elastic means on the cam 12, shaped to regulate this force during the rotation of the cam.

 The regulating means 22 of the illustrated embodiment comprises:

 a piston with controlled displacement 24 bearing against the elastic means 20 and displaceable in a direction parallel to the axis of the regulating pusher,

 displacement means 26 of the controlled displacement piston 24,

 a control means 28 of the displacement means 26 during the rotation of the cam.

 The displacement means 26 shown is hydraulic and comprises a variable volume chamber 27 filled with a fluid. The displacement piston 24 forms a movable wall of this chamber 27.

The control means 28 comprises a conduit 30 for supplying the chamber 27 with fluid, this supply circuit 30 further comprising an electro valve 29 for regulating the quantity of fluid supplying the chamber 27. The control means 28 comprises Also, a fluid reservoir 31. Alternatively, the supply conduit 30 may be connected to a fluid circuit (not shown). The control means 28 may also include a pump for the circulation of the fluid if necessary (not shown). The fluid used may be oil or any other suitable fluid.

 In the example shown, the regulating device 10 comprises a body 32 inside which the controlled displacement piston 24 and the elastic means 20 are movably mounted in translation along the axis 18 of the regulating pusher 16. The chamber 27 is thus delimited by the body 32 and the controlled displacement piston 24. The fluid supply circuit 30 described above opens into the chamber 27, for example on a wall of the chamber opposite to the controlled displacement piston 24. The pusher The elastic means 20 comprises a side 20a in contact with and / or integral with the axis 18 of the pusher 16 and an opposite side 20b in contact with and / or integral with the pusher 16. displacement piston 24. In the example, one end of the axis 18 of the pusher 16 is integral with a piston 34, distinct from the controlled displacement piston 24. This second piston 34 is also mounted mobile in transla in the body 32 and is in contact and / or integral with the elastic means 20. The latter is thus located between the two pistons 24 and 34.

 In the example shown, the regulating device 10 finally comprises a control means 36 of the regulating means 22 as a function of an expected and / or observed torque fluctuation N. This control means 36 is thus connected to the electro valve 29 of the regulating device 10 in order to control it as a function of the torque fluctuation N.

 FIG. 2 diagrammatically represents an operating diagram of a control means 36.

 This control means 36 comprises:

 means 38 for receiving characteristic data CN of a fluctuation N experienced by a shaft equipped with a regulation device 10,

processing means 40 arranged to generate a control signal SN of the regulating means 22 as a function of CN data characteristic of a fluctuation N undergone by a tree, transmission means 42 of the control signal SN to the regulation means 22 of the regulation device.

 In the example shown, the generated SN control signal is transmitted to the electro valve 29 of the regulating means 22.

The control means 36 described above could also be used to control a regulating means comprising a mechanical displacement means of the controlled displacement piston, the control signal S _N then being for example transmitted to a stepping motor which feeds the mechanical means, for example an electric jack.

 Whatever the embodiment of the displacement means 26 of the controlled displacement piston 24 (mechanical or hydraulic), the control means 36 may be part of a vehicle management system. For example, when the regulating device 10 is used to regulate the rotation of a shaft carrying at least one cam intended for the actuation of an element, in particular of a fuel injection member of a combustion engine of motor vehicle, this control means 36 can be connected to the vehicle management system or receive data from this management system.

 In another embodiment, not shown, in which the regulating device 10 is mounted on a camshaft of a fuel injection system of a motor vehicle, the regulating device 10 does not comprise any control means. 36 or electro valve 29: the supply duct 30 is directly in fluid communication with the fuel present in an injection chamber of the injection device. Thus, the fuel pressure inside the chamber of the regulating means is identical to the fuel pressure inside the injection chamber, so that the torque applied by the regulating device 10 to the shaft will be of the same magnitude as the torque applied to the control cam of the opening of the injection chamber.

 The regulation device according to the invention thus aims to produce a torque of the same amplitude, or similar amplitude, but in phase opposition as the dynamic torque generated by members connected to a shaft equipped with the regulating device.

In the case of a camshaft carrying 4 cams each actuating a fuel injection pump piston, the regulation 10 according to the invention comprises a cam with 4 lobes to compensate for the 4 torque fluctuations generated by the pump during a rotation of the shaft. This compensation can be obtained as follows:

 a position of the regulation push-button against a lobe 13 of the cam when a small torque is applied to the shaft because of the operation of the injection pump,

 a position of the regulation push-button 16 bearing against the cam 12 between two lobes 13 when a high torque is applied to the shaft because of the operation of the injection pump.

 In all cases, the amplitude of the torque applied by the regulating device 10 on the shaft depends on the amplitude of the torque undergone. Thus, at low engine speed, while the acyclism is low, the amplitude of the torque applied by the control device 10 on the shaft may be low or zero. On the contrary, for a high engine speed, while the acyclism is strong, the amplitude of the torque applied by the regulating device 10 on the shaft will also be high.

Claims

1. Device for regulating (10) the rotation of a shaft subjected to N torque fluctuations per revolution of rotation carried out in a rotation time T, said device comprising:  a cam (12) provided with an axis of rotation (14) and intended to be secured to the shaft so that its axis of rotation (14) coincides with the axis of the shaft, said cam (12) having N lobes (13), a first pusher (15) for operating an engine member and carried by an axis having a radial or longitudinal orientation with respect to the axis of the cam,  characterized in that it comprises:  a second regulating pusher (16) carried by an axis (18) actuated in phase shift of a time of T / 2N with respect to the first pusher (15) per revolution of rotation, said regulating pusher (16) being movable in translation in the direction of this axis (18), said regulating pusher (16) being held in abutment against the cam (12) by a support system exerting a force on said regulating pusher (16) in the direction of the cam ( 12), said support system being shaped to regulate this force during rotation of the cam (12).  2. Control device (10) according to claim 1, characterized in that the support system comprises an elastic means (20) shaped to exert a bearing force on said control push-button (16) in the direction of the cam (12) and means (22) for regulating the force exerted by the resilient means (20) on the cam (12).  3. Control device (10) according to claim 2, characterized in that the control means (22) comprises a stop element having a variable stiffness.  4. Control device (10) according to one of claims 2 or 3, characterized in that the control means comprises a control means (36) adapted to change the force exerted by the support system, for example adapted to modify the stiffness of the stop element, as a function of an expected and / or observed torque fluctuation N. 5. Control device (10) according to any one of claims 2 to 4, characterized in that the regulating means (22) comprises: a displacement piston (24) bearing against said elastic means (20) and movable in a direction parallel to the axis (18) of the regulating pusher (16),  displacement means (26) of the controlled displacement piston (24),  control means (28) of said moving means (26) during rotation of the cam (12).  6. Control device (10) according to claim 5, characterized in that it comprises a body (32) inside which the displacement piston (24) and the elastic means (20) are mounted movable in translation along the axis (18) of the regulating pusher (16), the regulating pusher (16) being located outside said body (32), the elastic means (20) comprising a side (20a) in contact and / or integral with the axis (18) of the regulating pusher (16) and an opposite side (20b) in contact and / or integral with the controlled displacement piston (24).  7. Control device (10) according to one of claims 4 or 5, characterized in that the displacement means (26) of the controlled displacement piston (24) is mechanical or hydraulic.  8. Control device (10) according to claim 7, characterized in that the hydraulic displacement means (26) comprises a chamber (27) with variable volume filled with a fluid, this chamber (27) comprising a connected mobile wall to the controlled displacement piston (24) or formed by this controlled displacement piston (24).  9. Shaft carrying at least one cam intended for the actuation of a member, in particular of a fuel injection member of a motor vehicle engine, characterized in that it comprises at least one regulating device (10) according to one of claims 1 to 8. 10. Fuel injection device for a motor vehicle engine, comprising a shaft carrying at least one actuating cam of a fuel injection pump, said shaft being equipped with a regulating device (10). ) according to one of claims 1 to 8. A fuel injection device according to claim 10, wherein the regulating means (22) of the regulating device (10) comprises:  a displacement piston (24) bearing against the elastic means (20) and displaceable in a direction parallel to the axis (18) of the regulating pusher (16),  means for displacing (26) hydraulically said controlled displacement piston (24) supplied with fluid,  control means (28) for the hydraulic displacement means (26) during rotation of the shaft,  and wherein the hydraulic displacement means (26) is supplied with fluid:  by a fluid circuit (30) independent of the injection device, for example an oil circuit, or  - By a fuel circuit in fluid communication with a fuel injection chamber of the injection device.  12. Motor vehicle comprising a camshaft according to claim 9 or an injection device (10) according to one of claims 10 or 1 1.