Method for controlling the switching on and off of a hydrodynamic retarder and retarder with clutch

Abstract

A method for controlling the switching on and off of a hydrodynamic retarder in a motor vehicle powertrain is proposed, wherein the hydrodynamic retarder comprises a rotor arranged on a retarder shaft and a coupling device with an actuating device by means of which a coupling element can be switched from an open position to a closed position, wherein a control is provided by means of which the position of the coupling element can be controlled. According to the invention, it is proposed that, when the motor vehicle is stationary, the control system generates in a first step an intermediate signal, 0 or 1, based on switch-on criteria and a switching signal, 0 or 1, based on switch-off criteria, wherein in a second step a decision signal, 0 or 1, is generated based on the intermediate signal and the switching signal, by means of which the actuator is controlled and thus switched either to the open position or the closed position.

Description

[0001] The invention relates to a method for controlling the switching on and off of a hydrodynamic retarder in the drivetrain of a motor vehicle by means of a clutch. The invention further relates to a retarder with a clutch device that can be controlled by means of an actuator.

[0002] As is known from the StdT, the clutch is arranged between the drive train and the rotor of the retarder, so that when the retarder is switched off or decoupled, i.e. in non-braking operation, idling losses are avoided.

[0003] Commercial vehicles with a retarder integrated into the drivetrain that cannot be decoupled from it generally no longer meet the new emissions standards. The continuous drive of the rotor causes drag losses when not braking, which are undesirable in modern vehicles. Therefore, decoupleable retarders, in which the rotor can be selectively coupled to the drivetrain, have been increasingly used for some time. This minimizes drag losses and wear on the retarder when not braking.

[0004] Disengagement devices for retarders are designed so that the retarder can be engaged and disengaged while driving, under certain conditions. The necessary synchronization device is expensive, heavy, and subject to wear.

[0005] For example, EP 2 948 348 A1 discloses a coupling device composed of a multi-disc clutch and a jaw clutch. The multi-disc clutch, in particular, is subjected to high loads during shifting. Actuation is generally manual or pneumatic, as is known from DE 10 2013 224 095 A1.

[0006] Furthermore, electromagnetic couplings are fundamentally known from the prior art. For example, DE 10 2014 207 804 B3 discloses an electromagnetically actuated coupling arrangement in which coupling elements can be moved from a normally coupled position to a decoupled position by an electromagnetic actuator.

[0007] When operating a motor vehicle, up to 50% of all journeys are "empty runs" or journeys with a minimal load. These journeys do not necessarily require a retarder to be operational during the journey.

[0008] The object of the invention is to provide a method for controlling the switching on and off of a retarder, in which the construction of the clutch device can be simplified.

[0009] Another object of the invention is to propose an advantageous coupling device.

[0010] The problem is solved according to the invention by a method according to independent claim 1 and a device according to claim 6. Further advantageous embodiments of the present invention are found in the dependent claims.

[0011] A method for controlling the switching on and off of a hydrodynamic retarder in a motor vehicle powertrain is proposed, wherein the hydrodynamic retarder comprises a rotor arranged on a retarder shaft and a coupling device with an actuating device by means of which a coupling element can be switched from an open position to a closed position, wherein a control is provided by means of which the position of the coupling element can be controlled.

[0012] According to the invention, it is proposed that, when the motor vehicle is stationary, the control system generates in a first step an intermediate signal, 0 or 1, based on switch-on criteria and a switching signal, 0 or 1, based on switch-off criteria, wherein in a second step a decision signal, 0 or 1, is generated based on the intermediate signal and the switching signal, by means of which the actuator is controlled and thus switched either to the open position or the closed position.

[0013] The proposed switching method is based on the fact that the drivetrain is only coupled to or decoupled from the retarder when the vehicle is stationary. When stationary, the system must be designed so that the drive shaft and the retarder shaft are either stationary or have a differential rotational speed of less than 1 rpm.

[0014] The intermediate signals are stored as 0 or 1 signals in an auxiliary decision memory, where 1 means that the coupling should take the closed position and 0 means that the coupling should take the open position.

[0015] The activation criteria are stored as a 0 or 1 signal in a decision memory, where 1 means that the coupling should be in the closed position and 0 means that the coupling should be in the open position.

[0016] Only in a second step are these two signals, the intermediate signal and the switching signal, used to generate a decision signal of 0 or 1. The controller can be configured to define how the signals from the memory interact with each other and which result is output as the decision signal.

[0017] Furthermore, in a third step, the control system can determine a driver decision, 0 or 1, whereby the decision signal is adapted to the driver decision if it differs from the decision signal.

[0018] The intermediate signal can be switched from 0 to 1 if one of the following activation criteria is met: - the measured vehicle weight exceeds a definable limit - Along a determined route, a downhill section is identified whose gradient exceeds a definable limit.

[0019] The switching signal can be switched from 1 to 0 if one of the following switch-off criteria applies: - the measured vehicle weight is below a definable limit - Along a determined route, no downhill section is identified whose gradient exceeds a definable limit.

[0020] GPS data and various sensors can be used to determine the route.

[0021] The driver's decision can be detected by means of a switch or sensor. It should be noted again that the driver can initiate a switch-on request at any time by pressing a switch or activating a sensor, but the implementation of the decision signal only occurs when the vehicle is stationary or at the next time the vehicle is stationary.

[0022] The proposed method for controlling the switching on and off of the retarder eliminates the need to engage the clutch under load and synchronize different shaft speeds of the drive shaft and retarder shaft.

[0023] Furthermore, the decision can be made based on a stored algorithm, which uses additional data for the switching decision, such as the injection quantity, acceleration values, etc.

[0024] Furthermore, a retarder with a coupling device for implementing the method of controlling the engagement and disengagement of a hydrodynamic retarder in a motor vehicle powertrain is proposed. The retarder comprises a coupling element with a sliding toothed gear which, in an open position, engages with a toothed gear on a retarder shaft and, in a closed position, couples the retarder shaft to a drive shaft via a jaw gear. A proposed coupling device can comprise two coils, wherein an armature can be moved from a first end position to a second end position by means of the coils, and compensating springs are provided between the armature and the sliding toothed gear.

[0025] Furthermore, the coupling element can be fixed in the open and closed positions relative to the retarder shaft by means of detent elements, whereby the fixing force and the spring force of the compensating springs are defined via the axial anchor position.

[0026] The compensating springs can be designed such that, before reaching one of the end positions, the spring force of the active compensating spring is greater than the acting fixing force via the indexing elements in the axial direction and the frictional forces between the coupling element and the drive shaft and / or retarder shaft in the axial direction.

[0027] The invention will now be described in more detail using the following examples. Fig. 1. Explained using an example. Fig. Figure 1 shows a clutch device 1 in the closed position, whereby only the retarder shaft 20 of the actual retarder is shown. The rest of the retarder is sufficiently known from the standard technical data.

[0028] The coupling element 13 is axially displaceable on the retarder shaft 20. A detent bore 22 and pressure elements 17a, b are provided for axially fixing the coupling element 13 relative to the retarder shaft 20. Depending on the position of the coupling element 13, open or closed, one of the pressure elements 17a, b is pressed into the detent bore by means of the associated compression springs 18a, b. The sliding toothing 14 of the coupling element 13 engages with the toothing 16 on the retarder shaft 20 and, in the closed position, also engages with the jaw teeth 15 of the drive shaft 19.

[0029] A driver 12 is provided on the coupling element 13, which engages in the anchor 7 and is supported against the anchor 7 by compensating springs 11a, b, so that axial forces can be transmitted from the anchor 7 to the coupling element 13. The springs 11a, b and 18a, b are designed such that the fixing via the pressure elements 17a, b and compression springs 18a, b, and the spring force of one of the compensating springs 11a, b, which is defined by the axial anchor position, are designed such that, before one of the end positions is reached, the spring force of the active compensating spring 11a, b is greater than the forces due to the fixing.

[0030] The illustrated position of the coupling device is the closed position, in which the coupling element 13 couples the two shafts 16 and 19. The illustrated actuating device 3 operated using magnetic forces, although a pneumatic or mechanical actuating device is also conceivable. Crucially, the decoupling of the armature 7 and the coupling element 13 is achieved by the springs 11a, 11b. The springs 11a, 11b allow the armature 7 to be displaced axially without directly moving the coupling element 13.

[0031] The magnetic actuating device comprises 2 coils 6a, b, which are arranged in a yoke 4, wherein the coils 6a, b can be controlled separately.

[0032] The yoke 4 is designed such that the field lines 8a, b run differently through the yoke 4 depending on which coil 6a, b is activated. Starting from the closed position shown, coil 6b must be activated to move the armature 7 to the right position, thus reducing the gap 9. The stop 5a prevents the armature 7 from striking the yoke 2. As the gap 9 decreases, the magnetic forces acting on the armature 7 increase, and consequently, the spring forces of spring 11a also increase. The field line 8b around the left coil 6a is relatively small when coil 6a is not activated, so it does not impede the movement of the armature 7. Once the spring forces of spring 11a are sufficiently large, the holding force is overcome by the pressure element 17a, and the mechanism switches to the open position.In addition to the locking force, coupling forces also act when there is a differential rotational speed between shafts 16 and 19, so it is necessary that the differential rotational speed be equal to 0 or nearly equal to 0. Furthermore, engagement forces can occur when switching from the open to the closed position if the teeth of the sliding gear 14 and the jaw gear 15 are not optimally aligned axially with each other or are twisted relative to each other before switching. Reference symbol list 1 coupling device 2 cases 3 Actuating device 4 yoke 5a, b stop 6a, b coil 7 anchors 8 a, b field lines 9 columns 10 columns 11a, b Compensating spring 12 drivers 13 Coupling element 14 Sliding gear teeth 15 Claw teeth 16 gear teeth 17 a, b Printing element 18a, b Compression spring 19 Drive shaft 20 Retarder shaft 21 Rotor 22 grid holes QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 2 948 348 A1

[0005] DE 10 2013 224 095 A1

[0005] DE 10 2014 207 804 B3

[0006]

Claims

[1] Method for controlling the switching on and off of a hydrodynamic retarder in a motor vehicle drive train, wherein the hydrodynamic retarder comprises a rotor (21) arranged on a retarder shaft (20) and a coupling device (1) with an actuating device (3) by means of which a coupling element (13) can be switched from an open position to a closed position, wherein a control is provided by means of which the position of the coupling element can be controlled, characterized by that when the motor vehicle is stationary, in a first step the control generates an intermediate signal, 0 or 1, on the basis of switch-on criteria and a switching signal, 0 or 1, on the basis of switch-off criteria, wherein in a second step a decision signal, 0 or 1, is generated on the basis of the intermediate signal and the switching signal, by means of which the actuating device is controlled and thus switched either into the open position or the closed position. [2] Method according to claim 1, characterized by that in a third step the control determines a driver decision, 0 or 1, whereby the decision signal is adapted to the driver decision if these differ. [3] Method according to claim 1, characterized by that the intermediate signal is switched from 0 to 1 if one of the following switching criteria applies: - the measured vehicle weight is above a definable limit - along a determined route, a downhill section is determined whose gradient exceeds a definable limit value. [4] Method according to claim 1, characterized by that the switching signal is switched from 1 to 0 if one of the following switch-off criteria applies: - the measured vehicle weight is below a definable limit - along a determined route, no downhill section is determined whose gradient exceeds a definable limit value [5] Method according to claim 2, characterized by that the driver's decision is recorded by means of a switch or sensor. [6] Retarder with coupling device (1) for carrying out the method for controlling the switching on and off of a hydrodynamic retarder in a motor vehicle drive train, comprising a coupling element (13) with a sliding toothing (14) which, in an open position, engages with a toothing (16) on a retarder shaft (20) and, in a closed position, couples the retarder shaft (20) to a drive shaft (19) via a claw toothing (15), characterized bythat the coupling device (1) comprises two coils (6a, b), wherein by means of the coils (6a, b) an armature (7) is movable from a first end position to a second end position and compensating springs (11a, b) are provided between the armature (7) and the sliding toothing (14). [7] Retarder according to claim 6, characterized by that the coupling element (13) can be fixed in the open position and the closed position relative to the retarder shaft by means of locking elements (17a, b, 18a, b), wherein the fixing force and the spring force of the compensating springs (11a, b) are defined via the axial anchor position. [8] Retarder according to claim 6, characterized by that the compensating springs (11a, b) are designed such that before reaching one of the end positions, the spring force of the active compensating spring (11a, b) is greater than the fixing force via the locking elements and the frictional forces between the coupling element (13) and the drive shaft (19) and / or retarder shaft (20).

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