阅读说明：本技术 操作用于使车辆的减速器联接及断开联接的分离离合器 (Operating a disconnect clutch for coupling and decoupling a retarder of a vehicle ) 是由 C·鲁查特 T·沃格特 于 2020-08-19 设计创作，主要内容包括：提出一种用于操作车辆的制动系统的方法,该制动系统具有至少一个液压的减速器(6)和分离离合器(7),该分离离合器用于使减速器(6)与车辆的动力传动系(1,2,3,4)的力流联接和断开联接。在减速器(6)的制动操作期间,该减速器(6)的工作流体被加热。因此,能够藉由冷却设备(9)来冷却该工作流体。在此,在工作流体的温度(T)足够高的情况下,延迟使分离离合器(7)断开,其中在延迟(dt)期间,尤其在回路中引导工作流体经过冷却设备(9)以用于冷却。(A method for operating a brake system of a vehicle is proposed, which has at least one hydraulic retarder (6) and a separating clutch (7) for coupling and decoupling the retarder (6) to and from a force flow of a drive train (1, 2, 3, 4) of the vehicle. During a braking operation of the retarder (6), the operating fluid of the retarder (6) is heated. Thus, the working fluid can be cooled by the cooling device (9). In this case, the delay causes the separating clutch (7) to open when the temperature (T) of the working fluid is sufficiently high, wherein during the delay (dt), the working fluid is conducted through a cooling device (9) for cooling, in particular in a circuit.)

1. A method for operating a brake system of a vehicle, characterized in that the brake system has at least one hydraulic retarder (6) and a disconnect clutch (7) for coupling and decoupling the retarder (6) to and from a force flow of a drive train (1, 2, 3, 4) of the vehicle,

wherein during a braking operation of the retarder (6), the operating fluid of the retarder (6) is heated and

wherein the working fluid can be cooled by means of a cooling device (9),

wherein in case the temperature (T) of the working fluid is sufficiently high, delaying the disengagement of the separator clutch (7),

wherein during said delay (dt), said working fluid is led through a cooling device (9) for cooling, in particular in a loop.

2. Method according to claim 1, wherein the retarder (6) has a drive shaft (6C), wherein the drive shaft (6C) can be coupled and decoupled by means of the disconnect clutch (7) from the force flow of the power train (1, 2, 3, 4) of the vehicle, wherein a pump (6D) is coupled with the drive shaft (6C) and driven by the drive shaft at least during the delay (dt), such that the working fluid is conducted by means of the pump (6D) through the cooling device (9) for cooling.

3. The method according to claim 2, wherein the pump (6D) has a delivery volume that can be set by mechanically adjusting the pump.

4. A method according to one of claims 1 to 3, wherein the disconnection of the separator clutch (7) and the leading of the working fluid through the cooling device (9) for cooling is delayed so long until the temperature (T) of the working fluid reaches a temperature threshold value (Temp 1).

5. Method according to one of claims 1 to 4, wherein the disengagement of the separator clutch (7) is delayed as long as a preset time span.

6. Method according to one of the preceding claims 1 to 5, wherein the emptying of the operating fluid of the retarder (6) is started before the disconnect clutch (7) is disconnected, or

Wherein the evacuation of the working fluid of the retarder (6) is started during the disengagement of the separator clutch (7), or

Wherein the evacuation of the working fluid of the retarder (6) is started after the disconnect clutch (7) is disconnected.

7. Method according to one of the preceding claims, wherein the separator clutch (7) is actuated as a function of a plurality of influencing variables, wherein one of the influencing variables is the temperature (T) of the operating fluid of the retarder, so that the opening of the separator clutch (7) is delayed at least so long in the presence of a sufficiently high temperature (T) until the temperature (T) reaches a temperature threshold (Temp 1).

8. The method according to claim 7, wherein a further influencing variable of the plurality of influencing variables is the presence of a request for opening the disconnect clutch (7).

9. A controller (8) for operating a retarder (6) and a disconnect clutch (7) of a brake system of a vehicle for coupling and decoupling the retarder (6) to and from a force flow of a powertrain (1, 2, 3, 4) of the vehicle, characterized in that the controller (8) is designed for performing the method according to any one of the preceding claims.

10. A computer program product having instructions which, when executed by a computing unit (8), cause the computing unit (8) to carry out the method according to one of the claims 1 to 8.

Technical Field

The invention relates to a method for operating a brake system of a vehicle. The brake system has at least one hydraulic retarder and a separating clutch for coupling and decoupling the retarder to and from a force flow of a drive train of the vehicle. During a braking operation of the retarder, the working fluid of the retarder is heated. Therefore, the working fluid can be cooled by the cooling device. The invention also relates to a controller and a computer program product for actuating the retarder and the separating clutch correspondingly.

Background

Vehicle brake systems with retarders are known and are often found in particular in heavy-duty vehicles. One of the advantages of the retarder is its almost wear-free operation compared to conventional service brakes, such as disc brakes or drum brakes. The retarder is therefore used primarily to relieve the service brake of wear during longer braking. The retarder generates waste heat in the braking operation, which must be dissipated. This is usually achieved in hydraulic retarders by means of a cooling device, through which the working fluid of the retarder is conducted.

It is also known to design the retarder to be selectively couplable and uncouplable with the force flow of the drive train of the vehicle by means of a separating clutch. Document SE 201050160 a1 is mentioned only as an example for this purpose. This has the advantage that the operating losses of the drive train are particularly low when the retarder is decoupled by means of the separating clutch. In this way, the drag losses of the retarder outside its braking operation are minimized.

A method for controlling a separating clutch in a drive train of a motor vehicle, which has a drive motor and a retarder, is known from DE 102017104600 a 1. The separating clutch is arranged between the drive motor and/or the drive train and the retarder. The rotor of the retarder can thus be switched into a driving connection with the drive motor and/or the drive train by means of the separating clutch, and the working chamber of the retarder can thus be filled with operating medium to generate braking power. In this way, a braking torque is applied by the retarder to the drive train and/or the drive motor. A control device is provided, by means of which the separating clutch can be switched to the closed position or to the open position. Switching the separating clutch into the closed position is effected as a function of at least one input signal to the control device. The switching of the separating clutch back into the disengaged position is effected in dependence on the fact that the working chamber of the reduction gear is substantially free of working medium and, in addition, at least one further operating parameter and/or environmental parameter is not above a predetermined limit value. In this case, it can be provided that the switching of the separating clutch into the disengaged position is effected in particular only if at least one of the following operating and/or environmental parameters is met and/or is not above a definable limit value: downhill slopes of the roadway, time or distance until reaching the downhill section, generation of a corresponding input signal by the driver, generation of a final retarder brake within a defined time interval, certain limit values of the service brake of the vehicle being higher due to the previous braking.

DE 102011120621 a1 discloses a method for controlling a hydraulic retarder in a motor vehicle, which retarder can be mechanically decoupled by means of a separating clutch. The reduction gear has a circumferential bladed rotor and a bladed stator, or the reduction gear has a circumferential bladed rotor and a bladed counter-rotor that surrounds in the opposite direction. Together they form a working chamber which is filled with a working medium during braking operation and which is emptied during non-braking operation. In a braking operation, the rotor is driven by the driveline with the disconnect clutch closed. During the transition from braking operation to non-braking operation, the working chamber is emptied and the separator clutch is disengaged. The transition from braking operation to non-braking operation is initiated by a retarder disconnection request by the drive assist system or by manipulation of an input device by the vehicle driver. In this case, the separating clutch is held closed for a predetermined time span after the presence of a retarder deactivation request is ascertained. The working chamber of the retarder is emptied of working medium by continuing to drive the rotor and by interrupting the supply of working medium into the working chamber. The predetermined time span varies depending on at least one of the following variables, while and/or after the retarder disconnect request is acknowledged: the rotational speed of the rotor; a discharge pressure, by means of which the working medium is evacuated from the working chamber; the degree of filling of the working chamber with working medium; the temperature of the working medium; the braking torque of the hydraulic retarder.

The object of the present invention is to improve the prior art.

Disclosure of Invention

This object is achieved by the measures given in the main claims. Preferred embodiments thereof may be derived from the dependent claims.

Accordingly, a method for operating a brake system of a vehicle, in particular of a motor vehicle, is proposed. The brake system has at least a hydraulic retarder and a separating clutch for selectively coupling and decoupling the retarder to and from a force flow of a drive train of the vehicle, wherein the force flow can also occur as a torque flow or a mechanical power flow in the drive train. During a braking operation of the retarder, a working fluid of the retarder is heated. Therefore, the working fluid can be cooled by the cooling apparatus. For this purpose, the working fluid is conveyed through the cooling device. Overheating of the working fluid can thus be avoided.

It is now proposed to delay the disengagement of the separating clutch in the event of a sufficiently high temperature of the working fluid. During the delay, directing the working fluid through the cooling apparatus for cooling a fluid. This is done in particular by means of a pump. Maintaining the retarder in a coupled state while conveying the working fluid through the cooling apparatus causes: before the separating clutch is (completely) disengaged, the working fluid is cooled in a targeted manner. This transport takes place in particular in a circuit. For cooling, the working fluid is therefore cooled not only in a single pass through the cooling device, but also, as many times as necessary, via the corresponding return line. This circuit of the working fluid preferably corresponds to a circuit for cooling the working fluid during (normal) braking operation of the retarder. The circuit therefore comprises, in particular, a retarder and a cooling device. The working fluid is thus conveyed from the retarder into the cooling device and then conveyed back again into the retarder.

The invention is based on the following recognition: during a braking operation, the working fluid of the retarder heats up, because it absorbs the braking power of the retarder as heat. This heat is in most cases discharged via the cooling device. In the case of very high braking powers, it is possible to temporarily introduce more heat into the working fluid than is directly discharged via the cooling device. The working fluid then acts as a heat buffer. In this case, the working fluid absorbs more heat than it can directly dissipate and thereby heats up considerably. In order to prevent overheating of the working fluid, the braking power of the retarder, which can be used, is then generally reduced from a predetermined temperature of the working fluid. The amount of heat introduced into the working fluid is thereby reduced and the temperature of the working fluid is therefore reduced to a conceivable level or at least not increased further.

The delay in disengaging the separating clutch while emptying the retarder described in the above-mentioned prior art (DE 102011120621 a1) results in: the working fluid from the working chamber of the retarder is drawn off and is no longer guided back again in the sense of a circuit. This is usually done in a reservoir. Where the working fluid is then no longer actively cooled. The working fluid is therefore cooled there only relatively slowly. Therefore, in a subsequent braking operation it may happen that: the working fluid still has a relatively high temperature due to the previous braking operation and can no longer be used efficiently as a thermal buffer. Therefore, when the subsequent braking operation has been started or shortly after the subsequent braking operation is started, the entire braking power of the retarder cannot be called up any more. During the delayed disengagement of the separating clutch, the retarder is therefore preferably operated in such a way that the working fluid is actively conveyed through the cooling device and is thereby cooled.

If the working fluid is sufficiently cooled in the proposed manner, the separating clutch can be (completely) disengaged and the retarder can thus be decoupled from the power flow of the drive train. In this way, it is ensured that the working fluid is sufficiently cold to enable the retarder to call up the full brake power when a subsequent braking operation of the retarder is started.

In addition to the method, a controller is also presented. The controller is used to operate the disconnect clutch for coupling and decoupling a retarder of a vehicle braking system to a force flow of a vehicle powertrain and for operating the retarder. As explained, the braking operation can only be effected if the separating clutch is closed and thus couples the retarder to the force flow.

The controller is designed for performing the proposed method. The control device therefore has, in particular, a data memory and a corresponding device for determining whether the temperature of the operating fluid of the retarder is sufficiently high as mentioned. If this is the case, the controller causes a delay to disengage the clutch, wherein the working fluid is directed through the cooling device.

The mentioned sufficiently high temperature may be a temperature threshold of the working fluid of the retarder. This temperature threshold may be preset. This temperature threshold value may be fixedly stored in a data memory of the controller. However, the temperature threshold can also be determined dynamically by means of the edge condition (in particular by the controller). It can be provided that the current temperature (actual temperature) of the working fluid is determined by measurement. It may be provided that this actual temperature is determined by means of a temperature model. It can be provided that this actual temperature is determined by estimation. It can then be provided that the measured actual temperature is compared with a temperature threshold value and, if the separating clutch is to be disengaged at the same time, the proposed measures for cooling the working fluid are initiated above the temperature threshold value. The execution of this measure and the subsequent opening of the separating clutch is controlled in particular by the proposed controller, for example by corresponding control or regulation.

The disengagement of the separating clutch is preferably delayed until the actual temperature of the working fluid reaches the temperature threshold mentioned, in particular until the actual temperature falls below the temperature threshold. Thus providing sufficient cooling of the working fluid. The time span of the delay is thus derived from the actual temperature of the working fluid. In this regard, the comparison of the actual temperature to the temperature threshold may then be performed during the delay. Once it is determined that the actual temperature has reached the temperature threshold, a sufficient delay is made. In particular, the separator clutch is then disengaged. In this process, it is therefore possible to disconnect the separating clutch in a temperature-regulated manner.

However, the disengagement of the disconnect clutch is delayed as long as a preset time span. This predetermined time span may be fixedly stored in the controller. It is therefore assumed after this fixed time span that the actual temperature of the working fluid has reliably reached the temperature threshold. However, it is also possible to determine this predetermined time span as a function of demand, in particular as a function of the actual temperature of the working fluid. This can be achieved by the controller and by means of a temperature model of the retarder stored in the controller. Thus, the delay required for the actual temperature of the working fluid to reach the temperature threshold may be predicted. After the predicted delay has elapsed, the disconnect clutch is disengaged. The disconnection of the separating clutch is thus effected in a time-controlled manner.

It can be provided that it is monitored whether a signal (in particular a corresponding request) for disengaging the separating clutch is present or whether the conditions required for disengaging the clutch are met. If this is the case, the disconnect clutch should be disengaged. It can then be provided that the signal or request for disengaging the separating clutch is subsequently implemented with a delay according to the recommendation. Instead, the final signal for disengaging the separating clutch can be generated (on the one hand) only when the delay required for disengaging the separating clutch has ended (i.e. only once the working fluid has cooled sufficiently), and (on the other hand) only when the remaining conditions required for disengaging the clutch are met.

The cooling device for the working fluid of the retarder is in particular a heat exchanger. The heat exchanger is in particular a liquid-liquid heat exchanger or a liquid-gas heat exchanger. The cooling device is in particular embodied such that the working fluid releases its heat to the liquid of the vehicle.

As already explained in the opening paragraph, a retarder is a brake device for braking a vehicle with little wear. Thus, the retarder is distinct from a service brake that is active due to member friction and therefore has friction. Such service brakes are usually implemented as disc brakes or drum brakes.

The retarder is designed here as a hydraulic retarder. The reducer thus has, in a manner known per se, a rotor provided with blades and a stator or counter-rotor acting with the rotor. The rotor or mating rotor likewise has blades. A working chamber of the reducer is formed between the rotor (on the one hand) and the stator or the mating rotor (on the other hand). The working chamber is filled with a working fluid at least during a braking operation of the retarder. In a braking operation, the rotor moves relative to the stator or mating rotor, thereby creating a fluid flow. This flow of working fluid produces a braking action on the rotor. The rotor may be coupled to the driveline by a disconnect clutch. The retarder can thus generate a braking action in the drive train when the clutch is closed. This is not possible in the case of a disconnect clutch disconnection. In addition to the braking operation, in particular in the case of a disengaged clutch being disengaged, the working fluid of the working chamber of the retarder is preferably drained. Before or after or during the closing of the separating clutch, the working chamber is at least partially filled with working fluid in order to prepare the retarder. The setting of the braking power of the retarder can then be effected in particular by setting the distance between the rotor and the stator (or between the rotor and the mating rotor) or by setting the amount of working fluid located in the working chamber. The mentioned circuit, through which the working fluid is conveyed for cooling, comprises in particular the working chamber of the reducer. The working fluid thus passes from the working chamber into the cooling device and then back into the working chamber.

The gear unit has in particular at least one drive shaft. The rotor of the reduction gear is preferably coupled to and driven by this drive shaft. The drive shaft can thus be a rotor shaft of the reduction gear, which has a rotor or a carrying rotor. The drive shaft can be selectively coupled and decoupled from a power flow of a drive train of the vehicle by means of a separating clutch. A pump for the working fluid is coupled with and driven by the drive shaft. Thus, the pump is mechanically driven by the drive shaft. In particular, the pump rotor shaft of the pump is coupled to and driven by a drive shaft. The pump is in particular fixedly coupled with the drive shaft. The working fluid can thus be guided through the cooling device for cooling by means of the pump. The pump is in particular a retarder pump. This retarder pump is part of the retarder and is for this purpose arranged in the retarder or on the housing of the retarder.

The pump preferably has a delivery volume that can be set by mechanically adjusting the pump. In this way, the delivery volume of the pump can be set within a certain range without the rotational speed of the pump having to be changed. Therefore, a zero delivery of the pump can also be achieved in the rotating drive shaft. The pump is therefore embodied in particular as a wobble slide valve pump or as a vane cell pump. Thus, during the delay to disengage the disconnect clutch, the pump is mechanically set such that an amount of working fluid sufficient to cool the working fluid is directed through the cooling device.

The retarder may be arranged at any, suitable position of the power train. The reduction gear can be arranged in particular on the input side or on the output side of a transmission (in particular a multi-stage transmission) of the drive train. However, the retarder can also be integrated into such a transmission, in particular by being arranged in the transmission housing or housing part (e.g. housing cover) to which it belongs. The control device of the retarder may be separate from the control device of the transmission, or the control device of the retarder may be integrated into the control device of the transmission. The mechanical branch from the drive train to the retarder may be arranged at a suitable location of the drive train. The branch is formed in particular by a spur gear or chain transmission, which is in particular each designed as a high drive stage. The separating clutch can be arranged in the region of the branch or (functionally) between the branch and the reduction gear or the rotor of the reduction gear. The separating clutch can also be arranged directly on the rotor of the reduction gear, for example on the drive shaft of the reduction gear. A particularly compact, uncoupleable retarder can thus be provided.

A separating clutch is to be understood as a mechanical device by means of which an input of the device can be selectively mechanically coupled and decoupled from an output of the device. In this case, in the coupled/closed state, a force or torque transmission can be achieved between the input and the output, which is almost impossible in the decoupled/open state. The separating clutch is preferably designed as a form-fitting or friction-fitting clutch, for example a claw clutch or a multiplate clutch. The disconnect clutch is implemented such that it can selectively couple the retarder to the power flow of the drivetrain (clutch closed) and can decouple the retarder from the power flow of the drivetrain (clutch open). The force flow in such a drive train is realized at least during a traction operation of the drive train between a drive motor for travel of the vehicle and a roadway surface. For this purpose, the drive motor drives the drive wheels or tracks of the vehicle, which in turn are drivingly in contact with the roadway surface. By coupling the retarder into the force flow, the vehicle can thus be braked by the retarder. By decoupling the retarder from the force flow, the vehicle may therefore not be braked by the retarder. The clutch release is actuated in particular by means of an associated actuator. This actuator is operated by the proposed controller.

Preferably, the operating fluid of the retarder is also evacuated within the scope of the proposed method. For this purpose, the working fluid in the working chamber of the retarder is removed in particular. In this way the retarder is reliably disabled. The working fluid is in particular emptied into the reservoir. However, a margin may be left in the decelerator. The evacuation of the working fluid may be initiated before the disconnect clutch is disengaged. Alternatively, the evacuation of the working fluid can be started during the disconnection of the disconnect clutch. Alternatively, the evacuation of the working fluid may be started after the disconnect clutch is disconnected. In this case, a sufficient amount of the working fluid is preferably conducted through the cooling device for cooling, and the temperature of the working fluid is thereby substantially reduced, before the separating clutch is completely disengaged.

It can be provided that the separating clutch is actuated (automatically), i.e. selectively opened and closed, as a function of a plurality of influencing variables. It is then provided that when the separating clutch is disengaged, one of these influencing variables is the actual temperature of the working fluid. If the actual temperature is sufficiently high, the disconnection is delayed in the proposed manner and the working fluid is cooled down by leading it through a cooling device until the temperature threshold mentioned is reached. A further of these influencing variables may be a request for disengaging the separating clutch. The request may in particular be generated by the operator of the vehicle, i.e. by manual intervention, or may be generated automatically by the driving assistance system or by a superordinate brake management device.

A computer program product is also presented. This computer program product has instructions which, when executed by a computing unit, cause the computing unit to carry out the proposed method. The calculation unit thus controls or regulates the operation of the brake system according to the proposed method. The computing unit may be, for example, a computer or a microcontroller, or may comprise such a computer or microcontroller. The calculation unit may for example be part of the proposed controller. The computer program product may be, for example, an electronic data storage device having instructions stored electronically thereon. The computer program product is especially embodied for use in the mentioned controller.

Drawings

The invention is explained in detail below with the aid of the drawings, from which further preferred embodiments of the invention can be derived. Respectively according to schematic diagrams:

figure 1 shows a vehicle powertrain with a couplable and uncouplable retarder,

fig. 2 shows a control device for actuating a separating clutch for an engageable and disengageable retarder,

fig. 3 shows the passage of the disconnection process of the disconnect clutch for the couplable and uncouplable reduction gear.

In these figures, identical or at least functionally identical components, elements and units are provided with the same reference numerals.

Detailed Description

Fig. 1 shows a drive train of a vehicle, in particular a motor vehicle, in particular a utility vehicle or a passenger car, in a plan view. The power train has a drive motor 1 for running the vehicle, and the power train has a transmission 2 for converting a torque of the drive motor 1. The transmission is in particular a multi-stage transmission. Thus, the transmission may be, for example, an automated gear shifting transmission or an automatic transmission. A drive axle 3 of the drive train is provided on the driven side of the transmission 2. The drive axle is coupled with the drive wheel 4. Thus, a drive force (and thus a corresponding drive torque and a corresponding drive power) can be mechanically transmitted from the drive motor 1 to the drive wheels 4 by means of the drive train. The drive wheel 4 is supported on the surface of the traffic lane. Therefore, in the towing operation of the vehicle, the vehicle can be driven by the drive motor 1.

In the region of the drive wheels 4, a service brake of the vehicle is arranged in the form of a disc or drum brake 5. The service brake 5 is used in particular for temporary braking. The service brake 5 is frictionally engaged due to the construction.

A hydraulic retarder 6 is also provided as a continuous brake in the vehicle. The retarder 6 and the service brake 5 may each be part of a common braking system. However, the retarder 6 may also be implemented as a separate brake system. The retarder 6 as a braking system may also be an integral part of the transmission 2.

The speed reducer 6 has: a rotor 6A on which blades are arranged; and a stator 6B fixed to the housing, on which the vanes are also arranged. Instead of the stator 6B being fixed to the housing, a mating rotor may also be provided, which always rotates in the opposite direction to the rotor 6A when the rotor 6A rotates. However, this does not bring any changes to the way in which the retarder 6 operates as explained below.

A working chamber of the reducer 6 is created between the rotor 6A and the stator 6B. The working chamber is fillable with a working fluid. When the working chamber is sufficiently filled with the working fluid and relative rotation occurs between the rotor 6A and the stator 6B, the speed reducer 6 generates a braking torque on a drive shaft 6C of the speed reducer 6 coupled with the rotor 6A. The braking torque may depend on the degree of filling of the working chamber with working fluid and may depend on the distance from the rotor 6A and the stator 6B. In the retarder 6, either or both of these may be designed to be settable.

The reduction gear 6 is arranged, for example, in the region of the output-side end of the transmission 2. Alternatively, the retarder can also be connected to the drive train at another suitable location. A disconnect clutch 7 is provided between the power train and the reduction gear 6. The clutch 7 can be opened and closed selectively and selectively in a targeted manner. Depending on the embodiment of the clutch 7, it may also be set in an intermediate position, i.e. allowing only partial opening and closing. Thus, the speed reducer 6 can be selectively mechanically coupled and decoupled from the power flow of the power train by the clutch 7. With the retarder 6 coupled (clutch 7 closed), the retarder 6 can exert a braking action on the vehicle. In the case of an uncoupled reduction gear 6 (disengaged clutch 7), the reduction gear 6 is mechanically decoupled from the power flow of the drive train. Thus, the retarder cannot exert a braking action on the vehicle.

It should be noted here that, in the braking sense, the retarder 6 still does not produce a braking action in the coupled state. This is only the case if the degree of filling of the retarder 6 is additionally set for the braking operation and/or the distance between the rotor 6A and the stator 6B is set for the braking operation. However, the retarder 6 always generates a certain traction loss in the coupled state. By disengaging the disconnect clutch 7, such traction losses can be almost minimized.

During the braking operation of the retarder 6, the working fluid absorbs the braking power in the form of heat generated by the retarder 6. The working fluid is thus correspondingly heated. The heat is removed by means of a cooling device 9. The cooling device is in particular a heat exchanger. In the heat exchanger 9, the working fluid releases its heat to, for example, a coolant of the vehicle. Thus, when the retarder 6 is in cooling operation, the working fluid is led through the cooling device 9. The retarder 6 is then at least partially filled with working fluid.

The cooling device 9 is part of the circuit of the working fluid shown in fig. 1 in order to cool the working fluid. The arrows here exemplarily indicate the flow direction of the working fluid in the circuit. The working fluid is conveyed in a circuit through the cooling device 9 by means of the retarder pump 6D. This retarder pump can be arranged in the retarder 6 or on the housing of the retarder. The retarder pump 6D is driven by the drive shaft 6C. For this purpose, the retarder pump can be coupled to the drive shaft 6C in a rotationally fixed manner. The working fluid is therefore conveyed by means of the pump 6D in a circuit-wise manner from the retarder 6 (in particular from the working chamber) toward the cooling device 9 and then conveyed back again via the return line to the retarder (in particular into the working chamber).

For actuating the clutch 7, a control device 8 is provided. In particular, the controller 8 is also used for operating the retarder 6 itself, i.e. for setting the braking effect of the retarder 6, in particular by setting the filling degree of the retarder 6 and/or the distance between the rotor 6A and the stator 6B. Furthermore, the controller 8 is used to set the delivery volume of the retarder pump 6D.

Information and instructions may be conveyed to the controller 8. For actuating the clutch 7, the controller 8 processes the information and commands received therein by means of a logic circuit and outputs corresponding commands to the clutch 7. The actuator assigned to the clutch 7 then executes the command for the clutch 7. The corresponding applies to the retarder 6. The command of the control unit 8 for the retarder 6 is implemented by means of an actuator assigned to the retarder 6.

When the separating clutch 7 is disengaged, the working fluid can no longer be actively cooled by means of the cooling device 9, since the retarder pump 6D is then also decoupled from the drive train. However, actively cooling the working fluid is desirable when the actual temperature of the working fluid is relatively high and thus above a temperature threshold.

It is now proposed to delay the disconnection of the separating clutch 7 until the working fluid has sufficiently cooled down, when there is a disconnection request or when certain conditions for disconnection are met. For this purpose, the working fluid continues to be guided in the circuit mentioned via the cooling device 9 during the delay and is thus actively cooled. Sufficient cooling of the working fluid is achieved when its actual temperature at least reaches a temperature threshold. Following this, the separating clutch 7 can then be disengaged. Furthermore, the working fluid of the retarder 6 can then be evacuated. In this way, it is ensured that a sufficiently cooled working fluid is always available for the subsequent braking operation of the retarder 6. Thus providing the full braking power of the retarder 6.

Fig. 2 shows the controller 8. The controller 8 serves to automatically actuate a separating clutch 7 for coupling and decoupling a retarder 6 of a brake system of the vehicle to and from the force flow of the vehicle drive train. The controller 8 is also used to operate the retarder 6 itself. The braking power of the retarder 6 can thus be set by means of the controller 8. Furthermore, the retarder 6 is thus operable in a cooling mode, in which the working fluid of the retarder 6 is guided in a circuit through a cooling device and is cooled thereby. The controller 8 shown in fig. 2 is in particular the controller from fig. 1.

The controller 8 is provided with information and instructions on the input side by a plurality of systems of the vehicle. To this end, a brake management device 10 is included. The brake management device 10 is in particular embodied for setting a vehicle deceleration desired by a vehicle user (in particular a driver) by means of a retarder and/or a service brake 5 of the vehicle. The brake management device 10 outputs a corresponding command (signal a) to the controller 8.

The controller 8 is implemented to output information (signal B) about the state of the disconnect clutch 7 to the brake management device 10. Therefore, the brake management device 10 can know, for example: the clutch 7 is closed and thus the braking operation can be set by means of the retarder 6.

Furthermore, the controller 8 is exemplarily provided with information of the camera system 11 (signal C) and information of the adaptive speed adjusting device 12 (signal D) and information of the navigation system 13 (signal E) and information of the vehicle-to-X communication system 14 (signal F) on the input side. Other sources of information for the controller 8 may be used instead of or in addition to this, as desired. The camera system 10 may be part of an environment sensing device disposed on a vehicle.

The control 8 may have means for determining the actual temperature of the operating fluid of the retarder. This information (signal G) is taken into account in the proposed manner when the separating clutch 7 is disengaged and optionally also when the separating clutch 7 is engaged.

The information and commands (signals a to G) are processed by means of the controller 8 as various influencing variables in the decision to close and open the clutch. The controller 8 outputs a corresponding command (signal H) to the separation clutch 7. This command is implemented by a clutch actuator assigned to the separating clutch 7 in such a way that the clutch 7 is actuated in the closing sense or in the opening sense, respectively. The clutch 7 is thus operated in a somewhat intelligent manner in this way. The braking operation of the retarder 6 can be set when the clutch 7 is closed, so that the requested braking effect is set in the vehicle.

However, the predetermined cause, i.e. the corresponding (negative) influencing variable, may oppose the operation of the separating clutch 7. For example, the actual temperature of the working fluid of the retarder 6 (signal G) may be too high, i.e. above a temperature threshold. This influencing variable may be given a higher priority. When the separating clutch 7 is disengaged, the controller 8 can determine in this case: the retarder 6 is not allowed to operate and the separator clutch 7 should therefore be kept open for safety reasons. With the separating clutch 7 closed, the controller 8 can determine in this case: for safety reasons, the separating clutch 7 should be kept closed for a delay time in order to guide the working fluid through the cooling device during this time and thus actively cool it. Subsequently, the disconnect clutch 7 can be disengaged.

Such a process is exemplarily shown in fig. 3. Fig. 3 shows in the lower region a time curve of the actual temperature T of the working fluid of the retarder 6 in fig. 1. In the upper region of fig. 3, the time profile of the two signals S1, S2 for actuating the associated separating clutch 7 is shown, which has elapsed at the same time. In the case of the exemplary value "1", the separating clutch 7 should be closed, and in the case of the exemplary value "0", the separating clutch 7 should be open. Accordingly, in the transition between "0" and "1", the separator clutch 7 should be actuated in the closed sense or in the open sense.

When the separating clutch 7 is closed, the pump 6D of the retarder 6 is driven by the vehicle's drive train, whereby the working fluid of the retarder 6 is led through the cooling device 9 and the fluid is thereby actively cooled in the circuit. With the disconnect clutch 7 disengaged, the pump 6D is decoupled from the driveline. The pump is therefore not driven, whereby the working fluid is therefore not led through the cooling device 9 for cooling.

At the beginning, the separating clutch 7 is closed. Thus, signals S1 and S2 have a value of "1". At time t1, the separator clutch 7 is to be disengaged. For this reason, the signal S1 may become a value "0" at the time point t 1. Since it is directly possible to initiate the braking of the retarder 6 in advance, the working fluid then has a relatively high actual temperature. This actual temperature is higher than the temperature threshold Temp1 for disengaging the separating clutch 7.

To achieve rapid cooling of the working fluid for subsequent use of the retarder 6, the disengagement of the separator clutch 7 is delayed. Thus, the pump 6D continues to be coupled with the powertrain and directs the working fluid actively through the cooling device 9 during this time. At time point t2, the actual temperature of the working fluid reaches temperature threshold Temp 1. Therefore, the working fluid has been sufficiently cooled. The separator clutch 7 can then be disengaged as a result. The signal S2 actually applied for actuating the separating clutch 7 changes from the value "1" to the value "0" at time t 2. From time t2 (which may be offset in time from the physical disconnection of the separator clutch 7), the pump 6D is decoupled from the vehicle's drive train, whereby this pump terminates the supply of working fluid through the cooling device 9. Thus, the working fluid is then no longer actively cooled. The cooling rate of the working fluid is correspondingly reduced, which can be seen in fig. 3 as the slope from the actual temperature from time t2 decreases. Accordingly, disengaging the disconnect clutch 7 is delayed by a delay dt, which is between time points t1 and t 2.

It can be provided that the at least partial evacuation of the operating fluid of the retarder 6 is already started before time t2, or at time t2, or after time t 2.

The delay dt can be generated by the controller 8 of the retarder 6 obtaining the signal S1 in the sense of a request to disengage the separator clutch 7 and applying this signal in the sense of the signal S2 with a delay dt. The delay dt can also be generated by the controller 8 recognizing at time t 1: all influencing variables for disengaging the clutch 7 are satisfied, except for the forbidden high actual temperature T; and in the sense of signal S2, the clutch 7 is only caused to disengage if this influencing variable is also fulfilled with the end of the delay dt.

List of reference numerals

1 drive motor

2 speed variator

3 drive axle

4 driving wheel

5 service brake

6 speed reducer

6A rotor

6B stator

6C drive shaft

6D pump

7 separating clutch

8 controller

9 Cooling apparatus, Heat exchanger

10 brake management system

11 camera system

12 speed regulating device

13 navigation system

14 vehicle-to-X communication system

A … H signal

T temperature

time t

time t1, time t2

dt delay

S1, S2 Signal