Improved activation or disengagement method for an electro-hydraulic transmission - Patents.com

Abstract

A process for actuation of a propulsion system for a displacement component of a vehicle, the propulsion system comprising a hydraulic pump (30), a hydraulic motor (40) fed by the hydraulic pump (30) via a closed-loop hydraulic circuit, and an electric motor (10); Given a configuration in which the propulsion system is stopped (the electric motor, the hydraulic pump and the feed pump (35) are stopped and the hydraulic motor is disengaged), A process for the start-up comprising the following steps: starting the supply pump, starting the electric motor, setting the rotation of the hydraulic pump, adjusting the displacement of the hydraulic pump and / or the rotation speed of the electric motor to supply a flow rate corresponding to a set point of the hydraulic motor, and starting the hydraulic motor.

Description

[Technical field]

[0001] The present invention relates to an improved activation and disengagement process for electro-hydraulic transmissions, and more particularly for temporary assist devices. [Background technology]

[0002] Various solutions are known which propose to incorporate electrohydraulic propulsion devices for vehicles or engines having a primary heat motor or a primary electric motor.

[0003] Various transmission architectures have been proposed to achieve propulsion of vehicles, particularly those that combine hydraulic drive elements with thermal or electrical elements, and in particular for hydraulic assistance, e.g. electrohydraulic temporary assistance.

[0004] However, the various proposed architectures pose problems in terms of optimization and execution due to the characteristics of the various elements with certain limitations, which results in the inability to adapt commonly used architectures and processes.

[0005] The present invention aims to at least partially address these problems.

[0006] The present invention relates to a process for activating a secondary propulsion system for a vehicle displacement component, the vehicle comprising a primary propulsion system, the propulsion system comprising: a hydraulic pump having a discharge port and a suction port; A hydraulic motor having an outlet and an inlet, adapted to rotatably drive the displacement component and capable of being selectively engaged and disengaged from the displacement component, the hydraulic motor being fed from the hydraulic pump via a closed loop hydraulic circuit including a feed pump, the hydraulic circuit comprising: an engagement valve adapted to selectively connect or disconnect the hydraulic motor to the hydraulic pump or to disconnect the hydraulic motor to the hydraulic pump (30) and to connect the outlet of the hydraulic pump to its inlet and to connect the outlet of the hydraulic motor to its inlet; a hydraulic motor; an electric motor adapted to drive said hydraulic pump; a power source adapted to power the electric motor; Equipped with Assuming the propulsion system is in a stopped state, the electric motor, the hydraulic pump, and the feed pump are in a stopped state, and the hydraulic motor is disengaged, the process for starting up may include the following steps: starting the supply pump; energizing the electric motor to rotatably drive the hydraulic pump; adjusting the displacement of the hydraulic pump and / or the rotational speed of the electric motor to provide a flow rate corresponding to a set point applied to the hydraulic motor; controlling the engagement valve to effect activation of the hydraulic motor; Including, relating to a process.

[0007] According to one example, the engagement valve has three ports connected to the hydraulic motor and is adapted to connect the inlet and outlet of the hydraulic motor to a crankcase of the hydraulic motor and to a supply circuit of the hydraulic circuit, the hydraulic motor being of a type that is disengaged by retracting a piston into a cylinder block.

[0008] According to one example, the hydraulic motor is fitted with a return spring which tends to position the piston in a retracted position within the cylinder block.

[0009] According to one example, the set point applied during the regulation of the displacement corresponds to a forward speed of the vehicle at which the hydraulic motor provides no torque.

[0010] According to one example, following control of the engagement valve, a set point is applied to the system such that the hydraulic motor provides a non-zero tractive torque.

[0011] According to one example, the feed pump is driven in rotation by the electric motor, and activation of the electric motor is performed so as to operate the feed pump.

[0012] According to one example, the supply pump is an electric pump group independent of the electric motor.

[0013] According to one example, the displacement of the hydraulic pump and the rotational speed of the electric motor are controlled to generate a set point and maintain the rotational speed of the electric motor above a lower threshold.

[0014] According to one example, the displacement of the hydraulic pump and the rotational speed of the electric motor are controlled to produce the set point by maximizing the combined output of the hydraulic pump and the electric motor while maintaining the rotational speed of the electric motor above the lower threshold.

[0015] According to one example, given an engaged configuration of the propulsion system in which the electric motor rotates, the hydraulic pump and the supply pump provide flow, and the hydraulic motor engages and rotationally drives the displacement component, the process includes the following steps for disengaging the propulsion system: controlling the displacement of the hydraulic pump and / or the rotational speed of the electric motor to reduce the pressure in the hydraulic circuit to a static pressure; controlling the engagement valve to decouple the hydraulic motor from the hydraulic pump; reducing the displacement of the hydraulic pump to zero and stopping the electric motor; stopping the supply pump; Includes.

[0016] The present invention also provides a process for disengaging a secondary propulsion system for a vehicle displacement component, the vehicle comprising a primary propulsion system, the propulsion system comprising: a hydraulic pump having a discharge port and a suction port; A hydraulic motor having an outlet and an inlet, adapted to rotatably drive the displacement component and capable of being selectively engaged and disengaged from the displacement component, the hydraulic motor being fed from the hydraulic pump via a closed loop hydraulic circuit including a feed pump, the hydraulic circuit comprising: an engagement valve (80) adapted to selectively connect the hydraulic motor (40) to the hydraulic pump (30) or to disconnect the hydraulic motor (40) from the hydraulic pump (30) and to connect the outlet of the hydraulic pump (30) to the inlet thereof and to connect the outlet of the hydraulic motor (40) to the inlet thereof; a hydraulic motor; an electric motor adapted to drive said hydraulic pump; a power source adapted to power the electric motor; Equipped with Given an engaged configuration of the propulsion system, where the electric motor rotates, the hydraulic pump and the supply pump provide flow, and the hydraulic motor is engaged to rotationally drive the displacement component, the disengagement process comprises the following steps: controlling the displacement of the hydraulic pump and / or the rotational speed of the electric motor to reduce the pressure in the hydraulic circuit until a resting pressure is reached; controlling the engagement valve to decouple the hydraulic motor from the hydraulic pump; setting the displacement of the hydraulic pump to zero and stopping the electric motor; stopping the supply pump; Including, relating to a process.

[0017] The disengagement may be performed, for example, after an active phase of the secondary propulsion system, following the process for starting up described above.

[0018] According to one example, the displacement of the hydraulic pump and the rotational speed of the electric motor are controlled such that the rotational speed of the electric motor remains above a lower threshold until the step of stopping the electric motor.

[0019] According to one example, the static pressure is determined such that the hydraulic motor (40) applies zero torque.

[0020] The invention applies to any machine or engine having a traction chain or electric drive, in particular agricultural machines, such as tractors and self-propelled sprayers, as well as construction machines, such as compactors, forklifts, cherry pickers, mechanical shovels, bulldozers, vehicles, in particular trucks, lorries and powered trailers.

[0021] The invention and its advantages will be better understood on reading the following detailed description of different embodiments of the invention, given by way of non-limiting example. [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic diagram of a vehicle or engine with an electrohydraulic axle propulsion system; [Diagram 2] FIG. 2 is a diagram illustrating a control according to an embodiment of the present invention. [Diagram 3] FIG. 2 shows an overview of the steps of a control process according to one aspect of the present invention. [Figure 4] FIG. 1 illustrates an example of a system according to an embodiment of the present invention.

[0023] In all of the above drawings, common elements are identified by the same reference numbers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] FIG. 1 shows a schematic representation of a vehicle or engine equipped with an electro-hydraulic axle propulsion system.

[0025] In this figure, an electric motor 10 is shown, powered by a battery 12 and controlled by a controller 20. The electric motor 10 is, for example, of the synchronous type with permanent magnets. The electric motor 10 may, for example, include an internal control card and a chopper or converter, not shown. From set values ​​received from the outside, the current intensity and frequency are cut by a chopper to drive the electric motor 10 at the required torque and speed. The electric motor 10 is coupled to a hydraulic pump 30. The hydraulic pump 30 is connected to a simplified hydraulic circuit, via which it drives one or more hydraulic motors adapted to drive in rotation the propulsion components of the vehicle. Displacement components mean, for example, the axles and the wheels. In the example shown, the hydraulic pump 30 supplies two hydraulic motors 40A and 40B mounted in series, which drive, respectively, the wheels of the vehicle. It should be understood that this embodiment is not limiting and any type of hydraulic circuit can be fitted to said hydraulic pump 30, which includes one or more hydraulic motors 40 and which rotates the displacement components of the vehicle, in particular the axles or wheels.

[0026] The pump 30 is a variable displacement hydraulic pump, typically a hydraulic pump equipped with an axial piston and a tilting plate, and the displacement of the pump is controlled by controlling the tilt of the plate.

[0027] The hydraulic motor or motors supplied by the hydraulic pump 30 are typically fixed displacement hydraulic motors, for example hydraulic motors having radial pistons and multi-lobe cams.

[0028] The system as proposed may be employed, for example, to perform main transmission of a vehicle, and may also provide for hydraulic assistance of a secondary axle, as opposed to a primary axle driven by the vehicle's primary motor. When implementing hydraulic assistance, the system may be engaged permanently, periodically, or under predefined conditions, for example when the vehicle speed is below a predefined speed. The operation described below remains the same whatever the application.

[0029] Operation of a propulsion system as shown presents the problem of control of the electric motor 10.

[0030] The controller 20 as proposed is configured to perform control of the electric motor 20 and the hydraulic pump 30, and is configured to ensure component safety and to achieve operation that optimizes the power output.

[0031] Said controller 20 is typically connected to control components and is therefore typically adapted to receive set points which effect action by a user, for example controlling the activation of hydraulic assistance.

[0032] The set point is typically a flow set point defining a target flow rate to be delivered by the hydraulic pump 30, or a rotational speed set point defining a target rotation rate of a displacement component driven by the system, for example a machine speed set point, a wheel or axle rotational set point, or the rotational speed of a motor driving a displacement component such as a wheel. Such set points are understood to be equivalent.

[0033] The controller 20 as proposed controls the displacement of the hydraulic pump 30 and the rotational speed of the electric motor 10 to achieve a set point and ensure a minimum rotational speed of the electric motor 10 .

[0034] Indeed, the electric motor is prone to heat up and risk degradation when operating at low rotational speeds and delivering high torques, and the power output of the electric motor 10 is degraded if it is asked to deliver too much torque for a given rotational speed.

[0035] The proposed controller 20 aims to ensure that the electric motor 10 operates at a rotational speed above a lower speed threshold, thereby preventing the risk of overheating and thus deterioration of the electric motor 10.

[0036] The lower speed threshold is typically determined by a computer in response to data stored in memory unit 22 .

[0037] Said lower speed threshold may be a fixed value, for example between 800 and 1500 rpm, or between 900 and 1200 rpm, or for example equal to 1000 rpm, or may be a variable value depending on temperature.

[0038] The system may include a temperature sensor 24 adapted to measure a temperature characteristic of the operation of the electric motor 10. The temperature sensor 24 may, for example, be located near or opposite the electric motor 10 to measure the temperature of the electric motor or may measure the ambient temperature.

[0039] The controller 20 can thus determine a lower speed threshold Vmin depending on the measured temperature. The lower threshold Vmin is typically variable depending on the measured temperature. The lower threshold Vmin is typically determined to ensure the thermal stability of the system, in particular the electric motor 10, so as to ensure that the electric motor 10 rotates at a sufficiently high speed to dissipate heat and prevent overheating of the electric motor 10.

[0040] In this manner, the controller 20 is configured to prioritize the rotational speed of the electric motor 10 above the lower speed threshold, thus protecting the electric motor 10 from overheating. The controller 20 adapts the displacement of the hydraulic pump 30 to produce a set point.

[0041] The controller 20 is then typically configured to maximize the output of the hydraulic pump.

[0042] Thus, the controller 20 is typically configured to achieve the setpoint by controlling the displacement of the hydraulic pump and the rotational speed of the electric motor to maximise the combined output of the hydraulic pump and the electric motor while maintaining the rotational speed of the electric motor above a lower threshold.

[0043] The memory unit 22 is typically preloaded with data of the operating characteristics of the hydraulic pump 30 and the electric motor 10, typically output characteristics or characteristics showing the correspondence between input or set values ​​and output parameters of the elements, for example in the form of a chart or table, and determines the displacement of the hydraulic pump and the rotation speed of the electric motor 10 so as to maximize the total power as a function of the set value and the rotation speed of the electric motor 10, this value being equal to or greater than the lower threshold value. This data constitutes for example a mapping of losses / power or operation / torque of the hydraulic pump 30 and the electric motor 10, or a mapping of the displacement of the hydraulic pump as a function of the flow rate and delivery pressure requirements, and defines a number of operating points of the torque produced by the hydraulic pump 30 and the electric motor 10.

[0044] To achieve an optimized operating point, torque and power are determined depending on the rotational speed according to the currently loaded data, and the operating point of the hydraulic motor 10 is positioned at a point that provides the maximum available power.

[0045] The controller 20 is typically configured to provide variable, or non-linear, operation as a function of the drive speed of the axles or components driven by the electro-hydraulic traction system.

[0046] The controller may be configured to define several thresholds corresponding to several operational steps of the system.

[0047] The threshold value may, for example, correspond to the rotational speed of a component that is rotationally driven by the hydraulic system, for example the rotational speed of an axle.

[0048] The illustrated embodiment shows a speed sensor 26 adapted to measure the rotational speed of the wheels driven by hydraulic motor 40A and hydraulic motor 40B and provide relative information, it being understood that this example is not limiting and other sensors or components can be used to define the thresholds.

[0049] The thresholds usually correspond to a gradual start-up during which different operating modes can be defined.

[0050] As an example, a first operating mode may be defined for values ​​between 0 rpm and S1 rpm, where S1 is a first threshold value.

[0051] This first mode of operation represents starting up the vehicle and commencing operation.

[0052] It is understood that in such a mode the torque requirement is high and the speed to be reached and therefore the flow rate to be delivered are very low. However, in the case of the electric motor 10, delivering a high torque at a reduced rotational speed would entail a significant risk of overheating. Thus, in this first operating mode, the controller 20 controls the rotational speed of the electric motor 10 by preferentially ensuring that it is above or equal to a lower threshold value, or by keeping it constant and equal to the lower threshold value. The displacement of the hydraulic pump 30 is then determined in order to reach the setpoint.

[0053] Once the first threshold S1 is reached, the controller 20 can present a second operating mode, which typically controls the displacement of the hydraulic pump 30 at a constant value and increases the rotational speed of the electric motor 10 until it reaches a set value.

[0054] This second operating mode may be executed, for example, until the electric motor 10 reaches its maximum rotational speed, towards a second threshold value S2.

[0055] Once the second threshold S2 is reached, the rotational speed of the electric motor 10 remains constant and equal to its maximum value, and the controller 20 controls the displacement of the hydraulic pump 30 so as to reach a set value.

[0056] FIG. 2 is a graph that illustrates these different modes of operation.

[0057] The horizontal axis in this diagram represents the progression of the setpoint value, which may correspond for example to the rotational speed of an axle.

[0058] The vertical axis represents the change in rotation speed of the electric motor 10 , the flow rate of the hydraulic pump 30 , and the displacement of the hydraulic pump 30 .

[0059] The different curves show the variation of these different parameters depending on the setpoint: -Vm represents the rotational speed of the electric motor 10, -Cp represents the displacement of the hydraulic pump 30, −Qp represents the flow rate delivered by the hydraulic pump 30 .

[0060] As can be seen in this figure, when the system is operating, i.e. when the setpoint is greater than 0, the rotational speed Vm of the electric motor 10 rises rapidly to reach a lower threshold Vmin. The rotational speed Vm of the electric motor 10 is constant and equal to Vmin up to a threshold S1. In this first section, it is the displacement of the hydraulic pump 30 that is modified so as to obtain a desired flow rate Qp. In the illustrated example, the lower threshold Vmin is represented as being constant. However, as indicated above, the lower threshold can vary depending on the temperature. It is therefore understood here that this example is not limiting. According to an example, as long as the rotational speed Vm of the electric motor 10 is below Vmin, the displacement Cp of the hydraulic pump 30 remains zero.

[0061] When the setpoint is between S1 and S2, the displacement Cp of the hydraulic pump 30 is kept constant and equal to the value C1. It is the rotational speed Vm of the electric motor 10 that is modified to obtain the desired flow rate Qp.

[0062] The value S2 typically corresponds to the set point at which the electric motor 10 reaches its maximum rotational speed Vmax. When the set point is greater than S2, the rotational speed Vm of the electric motor 10 is constant and equal to Vmax, and it is the displacement of the hydraulic pump 30 that is modified to obtain the desired flow rate Qp. Cmax denotes the maximum value of the displacement of the hydraulic pump 30.

[0063] Alternatively, or additionally, when the setpoint is between S1 and S2, the controller 20 may be configured to maximize the power output of the hydraulic pump 30 and the electric motor 10 while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin. The controller 20 may, for example, vary the rotational speed Vm of the electric motor 10 and the displacement Cp of the hydraulic pump 30 to optimize the power output while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin regardless of the applied setpoint or over one or more predetermined ranges of setpoints.

[0064] Alternatively, or additionally, the controller 20 may be configured to maximize the torque provided by the electric motor 10 while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin. The controller 20 may, for example, vary the rotational speed Vm of the electric motor 10 and the displacement Cp of the hydraulic pump 30 to maximize the torque provided by the electric motor 10 while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin regardless of an applied set point or over one or more predetermined ranges of set points.

[0065] The controller 20 may be configured to alternate between different control modes depending on the conditions of use, giving priority to certain parameters.

[0066] The invention also relates to a process for controlling the propulsion system of a vehicle axle.One exemplary embodiment of such a control process is described below with reference to figure 3.

[0067] The propulsion system considered includes a variable displacement hydraulic pump and one or more hydraulic motors supplied from the hydraulic pump via a closed-loop hydraulic circuit and adapted to rotate one or more axles. The hydraulic motors are typically fixed displacement hydraulic motors. The propulsion system also includes an electric motor adapted to drive the hydraulic pump, a power source adapted to power the electric motors, and a control component such as a controller that may be coupled to sensors and / or a memory or information storage unit.

[0068] FIG. 3 shows a schematic process including a first step 100 for applying a set point, which typically results in an action by a user, for example controlling the activation of a hydraulic assist.

[0069] The set point is typically a thrust speed set point reflected by the flow rate set point provided by the hydraulic pump 30, or a rotational speed set point of a component driven by the system.

[0070] An operating mode is then determined, which in figure 3 is illustrated by two comparison steps 110 and 120, which determine successively whether the set point is greater than a first threshold value S1 and whether it is greater than a second threshold value S2.

[0071] Depending on the decision made, a control method is then applied, adapted as already explained, in particular with reference to figures 1 and 2 .

[0072] Thus, in the illustrated example, step 130 corresponds to a control method in which a set point is typically between 0 and S1 and which ensures as a priority that the rotational speed Vm of the electric motor 10 is equal to or greater than the lower threshold Vmin, or in which the rotational speed Vm of the electric motor 10 is kept constant and equal to the lower threshold Vmin, and the displacement Cp of the hydraulic pump 30 is then determined so as to achieve the set point.

[0073] Step 140 typically corresponds to a control method in which the set point is between S1 and S2 and the displacement Cp of the hydraulic pump 30 is kept constant and equal to the value C1. It is the rotational speed Vm of the electric motor 10 that is modified to obtain the desired flow rate Qp.

[0074] Step 140 typically corresponds to a control method in which the set point is greater than S2, the rotational speed Vm of the electric motor 10 remains constant and equal to Vmax, and it is the displacement of the hydraulic pump 30 that is modified to obtain the desired flow rate Qp.

[0075] The process then adapts the control strategy in response to changes in the set point via a loop of comparison steps 110 .

[0076] As indicated above, the control can be implemented to maximize the total power output of the hydraulic pump 30 and the electric motor 10 while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin. The rotational speed Vm of the electric motor 10 and the displacement Cp of the hydraulic pump 30 can be varied to optimize the total power output while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin, for example, regardless of the applied setpoint or over one or more given ranges of setpoints. For example, with reference to stored characteristics of the pump and electric motor components for a desired flow rate setpoint, the process determines the torque speed of the electric motor - the most beneficial pump displacement for a good power output, in a range of use where the rotational speed Vm of the electric motor 10 is always greater than the lower threshold Vmin. In this process, the load of the electric motor can be taken into account. For example, if the torque required from the electric motor is too high, the process can select a higher rotational speed Vm of the motor and a lower displacement Cp of the hydraulic pump 30 to achieve a more beneficial overall power output.

[0077] Alternatively or additionally, control may be performed to maximize the torque transmitted by the electric motor 10 while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin. The rotational speed Vm of the electric motor 10 and the displacement Cp of the hydraulic pump 30 may be varied, for example, to maximize the torque transmitted by the electric motor 10 while maintaining the rotational speed Vm of the electric motor 10 above a lower threshold Vmin, regardless of an applied set point or over one or more predetermined ranges of set point values.

[0078] The proposed system and associated control process controls the rotational speed of the electric motor and the displacement of the hydraulic pump non-linearly over their operating ranges.

[0079] The proposed system may also utilize different speed torques of the electric motor 10 and displacements of the hydraulic pump 30 in the ranges Vmin to Vmax and C1 to Cmax, for example to avoid noise modes or to utilize components with emphasis on economy or power. These control laws may be non-linear as a function of wheel speed.

[0080] The proposed invention defines a control to optimise operation of the electric motor and the hydraulic pump whilst protecting the electric motor from overheating.

[0081] FIG. 4 illustrates a particular embodiment of a system of electro-hydraulic transmissions which may be a main transmission or an auxiliary transmission of a vehicle or engine, and in particular an auxiliary transmission which may be selectively engaged or disengaged.

[0082] In the case of selectively engageable auxiliaries, the hydraulic motor 40 is usually of the type that can be disengaged from the wheels, particularly the radial multi-lobe cam type that can be disengaged by retracting the piston in a block when there is no pressure on the intake and discharge ports of the motor. Such motors may include a retaining spring to retract the piston. Crankcase pressure helps to return or maintain the piston in the retracted position. When the piston is retracted, it is released from the cam and the motor becomes inactive and can rotate without torque, thereby releasing the driven shaft. When the intake and discharge port pressures are reset, the piston moves out of the housing and engages the multi-lobe cam, connecting the motor to the driven shaft. In the disengaged position, these motors do not produce any noticeable drag torque. These motors can be engaged with low pressure, which engages the piston to the cam. They can also be engaged and rotated without torque, provided that the intake and discharge ports are at equal pressure, resulting in a freewheel mode of operation, but with some drag torque.

[0083] This figure shows the elements already described with reference to FIG. 1, as well as additional elements which are described below.

[0084] The hydraulic circuit connecting the hydraulic pump 30 to the hydraulic motors 40A and 40B includes a supply circuit 60 supplied by a supply pump 35 rotatably connected to the hydraulic pump 30. It will be understood that the supply pump 35 can also be driven in rotation independently of the hydraulic pump 30. The supply circuit 60 also makes it possible to obtain a control pressure for hydraulic control.

[0085] Said supply circuit 60 is of known construction and serves either to supply the hydraulic circuit or to bleed off excess fluid into a tank R.

[0086] The hydraulic circuit includes a control valve 80 interposed between the hydraulic pump 30 and the hydraulic motors 40A, 40B. As previously mentioned, it should be understood that this embodiment is not limiting and may be replaced by one or more hydraulic motors mounted in series or parallel, for example.

[0087] Engagement valve 80 is a 5 / 2 type valve having five ports and two positions.

[0088] The engagement valve 80 includes: A first port 81 connected to a first port of the hydraulic pump 30; A second port 82 connected to the second port of the hydraulic pump 30; a third port 83 connected to the first ports of the hydraulic motor 40A and the hydraulic motor 40B; a fourth port 84 connected to the second ports of the hydraulic motor 40A and the hydraulic motor 40B; and 5th port 85, has.

[0089] The fifth port 85 is connected to a tank R via a restriction 72, connected to the crankcases of the hydraulic motors 40A and 40B via a calibration valve 73, and connected to the tank R via the restriction 72 and restriction 74 arranged in series. The crankcases of the hydraulic motors 40A and 40B are connected to the supply circuit 60 via a calibration valve 75 having a calibration of usually about 0.3 bar, allowing the circulation of fluid to the supply circuit 60.

[0090] In a first configuration, the first port 81 is connected to the second port 82, while the third port 83, the fourth port 84 and the fifth port 85 are connected together. A return means 88, such as a spring, holds the engagement valve 80 in its first configuration by default.

[0091] In a second configuration, the first port 81 is connected to the third port 83, the second port 82 is connected to the fourth port 84, and the fifth port 85 is blocked.

[0092] Thus, in its first configuration, the engagement valve 80 connects the suction and discharge of the hydraulic pump 30 on the one hand, and the suction and discharge of the hydraulic motor 40A and the hydraulic motor 40B on the other hand, thus performing a bypass function best known as the "bypass" of the hydraulic pump 30 and the "bypass" of the hydraulic motor 40A and the hydraulic motor 40B.

[0093] In its second configuration, the engagement valve 80 connects the outlet of the hydraulic pump 30 to the inlets of the hydraulic motors 40A and 40B, and connects the outlets of the hydraulic motors 40A and 40B to the inlet of the hydraulic pump 30, in a given direction of rotation. When the direction of travel is reversed, reversing the flow direction, the inlet and outlet designations are reversed.

[0094] The engagement valve 80 is controlled by two opposing hydraulic controllers 86 and 87 .

[0095] The engagement valve 80 is actuated by a control valve 90 .

[0096] The control valve 90 is a 4 / 2 type valve having four ports and two configurations.

[0097] The control valve 90 includes: a first port 91 connected to the fifth port 85 of the engagement valve 80 via the throttle 72; a second port 92 connected to the supply pump 35 and the calibration valve 75; a third port 93 connected to the hydraulic control 86; a fourth port 94 connected to the hydraulic control 87; Includes.

[0098] The control valve 90 has a first configuration in which the first port 91 is connected to the third port 93 and the second port 92 is connected to the fourth port 94, and a second configuration in which the first port 91 is connected to the fourth port 94 and the second port 92 is connected to the third port 93.

[0099] The control valve 90 is controlled by an actuator 97, shown here as an electric actuator, and is opposed by a resilient return means 96, typically a spring.

[0100] The control valve 90 is in its first configuration by default and actuates the hydraulic controller 87 to position the engagement valve 80 in its first configuration (i.e., a configuration in which the hydraulic motors 40A and 40B are not powered by the hydraulic pump 30).

[0101] Activation of the controller 97 switches the engagement valve 80 to its second configuration. This activates the hydraulic controller 86, which positions the engagement valve 80 in its second configuration and connects the hydraulic motor 40A and the hydraulic motor 40B to the hydraulic pump 30.

[0102] The invention proposes an improved control for the engagement or disengagement of the propulsion of said displacement components by a system as described herein below.

[0103] An initial state is considered where the entire system is at rest: the electric motor 10 is at rest, the pressure in the hydraulic circuit is zero, and the control valve 90 and the engagement valve are each in a first configuration.

[0104] The electric motor 10 is started. As already mentioned above, the starting of the electric motor 10 is carried out so as to ensure a rotational speed above a lower threshold Vmin.

[0105] Activation of the electric motor 10 drives the hydraulic pump 30 in rotation, the displacement of which is zero in relation to a variable displacement hydraulic pump, and actuates the supply pump 35, setting the supply pressure in the hydraulic circuit. A time delay is typically implemented to allow activation of the supply pump 35 to establish the supply pressure in the hydraulic circuit.

[0106] It will be appreciated that if the feed pump 35 is driven by a separate element or is driven independently of the hydraulic pump 30, the feed pump 35 is engaged prior to the engagement or displacement of the hydraulic pump 30. For example, the feed pump 35 can be operated by a separate electric motor constituting an independent electric pump group. In this way, if the feed pump 35 is driven by a separate element, the latter is usually activated first, before the electric motor 10 is activated. In this way, the activation of the electric motor 10, the activation of the hydraulic pump 30 on the one hand and the activation of the feed pump 35 on the other hand can be performed simultaneously or sequentially, depending on the configuration of the system.

[0107] Activating the supply pump 35 means setting pressure in the hydraulic loop on the side of the hydraulic pump 30 via supply check valves on the two hydraulic lines, creating a control pressure, e.g. for the displacement control of the hydraulic pump 30 and for the control of the engagement valve 80 via the control valve 90.

[0108] The displacement of the hydraulic pump 30 and / or the rotational speed of the electric motor 10 are then adjusted to provide a flow rate corresponding to a set point applied to the hydraulic motor 40. This set point value typically corresponds to the flow rate required for the system to reproduce the speed of the vehicle driven by the transmission, thus avoiding motor torque being applied to the wheels.

[0109] Since the hydraulic pump 30 and the hydraulic motors 40A and 40B are in a bypass state, the pressure in the circuit is equal to or substantially equal to the supply pressure, which is usually 5 to 20 bar.

[0110] The controller 97 is actuated to switch the control valve 90 to a second configuration, which switches the engagement valve 80 to a second configuration, which causes the hydraulic motor 40 to be supplied with hydraulic pressure from the hydraulic pump 30, and in the process activates the hydraulic motor 40, and in the case of a hydraulic motor, may, if necessary, withdraw the piston of the hydraulic motor 40 from its housing, retracting the piston into its respective housing to achieve a freewheel configuration, as opposed to an engaged configuration in which the piston is in contact with a multi-lobe cam or plate. Excess pressure in the crankcases of the hydraulic motors 40A and 40B is purged via a restrictor 74 and / or a calibrated valve 75, the latter of which reinjects pressure from the crankcases into the supply circuit 60. With the hydraulic motors 40A and 40B engaged and the flow rate supplied substantially equal to the displacement speed of the vehicle, the hydraulic circuit does not provide any torque or noticeable traction. The pressure is normally set at 80 bar, which means that the assistance is active but on standby. When the vehicle is decelerating or braking, the set point value can be set to a lower pressure, for example 40 bar. This control can be improved by adjusting it using data from a pressure sensor. Then, when the assistance is used, a set point value slightly greater than the forward speed of the vehicle, or pressure control to a higher pressure, provides noticeable traction and the assistance is in effective traction mode. Pressure typically rises to 400 bar. Depending on the applied set point value, the displacement of the hydraulic pump 30 is controlled, and for example the rotational speed of the electric motor 10 is controlled and adapted to the operation of the vehicle, as described above, in particular with reference to Figures 2 and 3.

[0111] It will be understood that if the supply pump 35 is driven by a separate element or is driven independently of the hydraulic pump 30, the supply pump 35 will be engaged prior to engagement or displacement of the hydraulic pump 30.

[0112] In the case of hydraulic assistance at a secondary axle of a vehicle having a primary axle driven in rotation by a primary propulsion system, the setpoint value applied to the system is usually aimed at synchronizing the rotational speed of the secondary axle with that of the primary axle. The rotational speed of the electric motor 10 and the displacement of the hydraulic pump 30 are usually controlled to achieve this setpoint value, while the rotational speed of the electric motor 10 is kept above a lower threshold Vmin as mentioned above.

[0113] Next, the sequence for disabling the system will be described.

[0114] An initial situation is considered in which the system is engaged and the displacement components are driven by the hydraulic motors 40A and 40B, in which case the speed may be zero.

[0115] First, the pressure in the hydraulic circuit is reduced to reach a rest pressure by controlling the displacement of the hydraulic pump and / or the rotational speed of the electric motor. This rest or standby position corresponds to a driving mode in which the hydraulic motor is working but not providing torque. The pressure in the circuit is very low, typically 80 bar.

[0116] The control 97 of the control valve 90 is then released. The control valve 90 returns to the first configuration, which causes the engagement valve 80 to also return to the first configuration.

[0117] In the first configuration, the engagement valve 80 separates the hydraulic motor 40 from the hydraulic pump 30. This causes a drop in the pressure in the circuit, which settles to the level of the supply pressure and, if necessary, causes the piston to retract into the housing. Indeed, when the engagement valve 80 switches to the first configuration, the hydraulic motor 40 is driven in rotation by a displacement component, usually a wheel or an axle, but is no longer supplied with pressure. This causes the pressure at the outlet of the hydraulic motor 40 to rise. The fluid thus discharged passes through the engagement valve 80 and emerges again through the fifth port 85 before being discharged through the throttle 72 into the tank R. Due to the presence of the throttle 72, part of the flow passes through a calibration valve 73, which has a calibrated value, typically of the order of 0.3 bar. Since the calibration valve 73 is attached to the crankcase of the hydraulic motor 40, the flow passing through this calibration valve 73 causes an increase in the pressure in the crankcase of the hydraulic motor 40, which results in the effect of the piston of the hydraulic motor 40 being retracted into the housing.

[0118] The hydraulic motors 40A and 40B are fitted with return elements, such as springs, which tend to position the pistons in a retracted configuration. In this way, when no pressure is being applied to move the pistons out of the housing, the pistons are retracted and the displacement of the hydraulic motors is zero.

[0119] Here, for example, a time delay can be implemented to ensure retraction of the piston.

[0120] Since the hydraulic pump 30 is a variable displacement hydraulic pump, the displacement of the hydraulic pump 30 is controlled to be zero displacement. The electric motor 10 is maintained at a rotation speed higher than a lower threshold value Vmin.

[0121] The electric motor is then stopped, which stops the hydraulic pump 30 and then, if necessary, the supply system is stopped when the supply pump 35 is driven by another motor element.

[0122] The system and process as illustrated provides operation without the need to drive the pump when the system is disengaged, and in the case of an auxiliary transmission, protection of the various components and synchronization of rotational speeds are ensured.

[0123] Although the present invention has been described with reference to specific exemplary embodiments, it is clear that modifications and variations can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the different embodiments as shown and / or mentioned can be combined in further embodiments. The above description and drawings should therefore be regarded in an illustrative rather than a restrictive sense.

[0124] It will also be apparent that all features described with reference to a process may be transferred, either alone or in any combination, to a device, and vice versa.

Claims

1. 1. A process for activating a secondary propulsion system for a vehicle displacement component, the vehicle including a primary propulsion system, the propulsion system comprising: a hydraulic pump (30) having a discharge port and a suction port; a hydraulic motor (40) having an outlet and an inlet, adapted to rotationally drive the displacement component and capable of being selectively engaged and disengaged from the displacement component, the hydraulic motor (40) being supplied from the hydraulic pump (30) via a closed-loop hydraulic circuit including a supply pump, the hydraulic circuit comprising: an engagement valve (80) adapted to selectively connect or disconnect the hydraulic motor (40) to the hydraulic pump (30), connect the outlet of the hydraulic pump (30) to its inlet, and connect the outlet of the hydraulic motor (40) to its inlet; a hydraulic motor (40), an electric motor (10) adapted to drive said hydraulic pump; a power source (12) adapted to power said electric motor (10); Equipped with Assuming that the propulsion system is in a stopped state, the electric motor (10), the hydraulic pump (30) and the supply pump (30) are in a stopped state, and the hydraulic motor (40) is disengaged, the start-up process comprises the following steps: activating the supply pump (35); activating the electric motor to rotatably drive the hydraulic pump; adjusting the displacement of the hydraulic pump (30) and / or the rotational speed of the electric motor (10) to provide a flow rate corresponding to a set point applied to the hydraulic motor (40); controlling the engagement valve (80) to activate the hydraulic motor (40); The process includes:

2. 2. The process according to claim 1, characterized in that the engagement valve (80) has three ports connected to the hydraulic motor (40) and is adapted to connect the inlet and the outlet of the hydraulic motor (40) to the crankcase of the hydraulic motor (40) and to the supply circuit (60) of the hydraulic circuit, the hydraulic motor (40) being of the type that is disengaged by retraction of a piston in a cylinder block.

3. 3. The process of claim 2, wherein the hydraulic motor (40) is fitted with a return spring tending to position the piston in a retracted position within the cylinder block.

4. 4. The process of claim 1, wherein the set point applied during adjustment of the displacement corresponds to a forward speed of the vehicle at which the hydraulic motor (40) provides no torque.

5. 2. The process of claim 1, wherein a set point is applied to the system such that, following control of the engagement valve, the hydraulic motor (40) provides a non-zero tractive torque.

6. The process of claim 1 , wherein the feed pump is rotationally driven by the electric motor, and wherein activation of the electric motor is performed to operate the feed pump.

7. 2. The process of claim 1, wherein the supply pump (35) is an electric pump group independent of the electric motor (10).

8. 2. The process of claim 1, wherein the displacement of the hydraulic pump (30) and the rotational speed of the electric motor (10) are controlled to generate a set point and maintain the rotational speed of the electric motor (10) above a lower threshold (Vmin).

9. 9. The process of claim 8, wherein the displacement of the hydraulic pump (30) and the rotational speed of the electric motor (10) are controlled to produce the set point by maximizing the combined power output of the hydraulic pump (30) and the electric motor (10) while maintaining the rotational speed of the electric motor (10) above the lower threshold (Vmin).

10. Given an engagement configuration of the propulsion system in which the electric motor (10) rotates, the hydraulic pump (30) and the supply pump (35) provide flow, and the hydraulic motor (40) is engaged to rotationally drive the displacement component, disengaging the propulsion system by the following steps: controlling the displacement of the hydraulic pump (30) and / or the rotational speed of the electric motor (10) to reduce the pressure in the hydraulic circuit until it reaches a resting pressure; controlling the engagement valve (80) to decouple the hydraulic motor (40) from the hydraulic pump (30); a step of setting the displacement of the hydraulic pump (30) to zero and stopping the electric motor (10); stopping the supply pump (35); 2. The process for activating of claim 1, comprising:

11. 11. The process of claim 10, wherein the displacement of the hydraulic pump (30) and the rotational speed of the electric motor (10) are controlled so that the rotational speed of the electric motor (10) remains higher than a lower threshold (Vmin) until the step of stopping the electric motor (10).

12. The process of claim 10, wherein the static pressure is determined such that the hydraulic motor (40) applies zero torque.

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