Recuperation during trailer operation

Abstract

Control unit (120) for a vehicle (100), wherein the vehicle (100) comprises a motor / generator (109) configured to drive a recuperating axle (104) of the vehicle (100) in motor mode and to decelerate the recuperating axle (104) of the vehicle (100) in generator mode, wherein the control unit (120) is configured - to determine whether the vehicle (100) is towing a trailer; - to determine whether the motor / generator (109) causes a first deceleration component on the recuperating axle (104); - to cause a second deceleration component to be effected on a non-recuperating axle (106) of the vehicle (100) when it has been determined that the vehicle (100) is towing a trailer and that a first deceleration component is effected on the recuperating axle (104) by the motor / generator (109), characterized in that - to recognize that the vehicle (100) is in overrun mode; - to distribute a total deceleration corresponding to the thrust operation between the first and second deceleration components, where the first and second deceleration components are not equal to zero.

Description

[0001] The invention relates to vehicles comprising an electric motor. In particular, the invention relates to electric-drive vehicles that can be operated with a trailer.

[0002] In electric vehicles, especially hybrid vehicles, one or more electric motors are typically used as generators during deceleration to convert the vehicle's existing kinetic energy into electrical energy. This process is called recuperation.

[0003] Regenerative braking, using one or more electric motors, usually occurs only on one axle of the vehicle. This can lead to unstable handling during deceleration. For this reason, hybrid-powered vehicles usually have hybrid stability management systems designed to ensure stable deceleration.

[0004] Vehicles, especially dual-track vehicles or automobiles, are often used to tow a trailer (e.g., a caravan, horsebox, or cargo trailer). The additional load of the trailer and / or the movable coupling of the trailer to the vehicle significantly alter the vehicle's handling. Hybrid drive systems, especially in conjunction with hybrid stability management systems, are typically not designed for this type of trailer operation, which means that many hybrid-powered vehicles are not approved for trailer operation.

[0005] For further information on the state of the art, please refer to DE 10 2010 042 907 A1.

[0006] This document addresses the aforementioned technical problems. In particular, this document describes a device (and a corresponding method) for stabilizing a vehicle towing a trailer. The described device is designed specifically for electric and / or hybrid vehicles and enables stable deceleration while simultaneously recovering the vehicle's kinetic energy.

[0007] According to one aspect, a control unit for a vehicle is described. The control unit can be configured to increase the stability of a vehicle during deceleration. The control unit can, for example, be part of a hybrid stability management system. The vehicle can, in particular, be a two-track vehicle, such as a passenger car or an automobile. The vehicle comprises a motor / generator configured to drive a recuperating axle of the vehicle during engine operation (e.g., using electrical energy). Furthermore, the motor / generator is configured to decelerate the recuperating axle of the vehicle during generator operation (e.g., to generate electrical energy). Furthermore, the vehicle can comprise an internal combustion engine, which, together with the motor / generator, forms a hybrid drive for the vehicle.Both the combustion engine and the motor / generator can be designed to act on the same axle of the vehicle (i.e., the vehicle's recuperating axle). Alternatively, the vehicle can be a purely electric vehicle.

[0008] The control unit may be configured to determine whether the vehicle is towing a trailer. In particular, the control unit may be configured to receive a signal and / or determine a load of the vehicle to determine whether the vehicle is towing a trailer.

[0009] Furthermore, the control unit can be configured to determine whether the motor / generator causes a first deceleration component to the recuperating axle. In other words, the control unit can be configured to detect that the motor / generator causes a first deceleration component to the recuperating axle. In still other words, the control unit can be configured to determine whether the motor / generator causes a first deceleration component to the recuperating axle whose absolute value is greater than or equal to a predefined threshold value. The predefined threshold value can be, for example, 0.1, 0.5, or 1 m / s. 2In particular, the motor / generator can cause a deceleration of the rotational movement of the recuperating axle, which—assuming no slippage occurs—leads to a corresponding deceleration of the vehicle. The initial deceleration component caused by the motor / generator can, for example, be a deceleration of the vehicle corresponding to a coasting operation of the vehicle.

[0010] The presence of deceleration on the regenerative axle when towing a trailer can lead to unstable vehicle handling. For this reason, the control unit can be configured to initiate a second deceleration component on (or at) a non-regenerative axle of the vehicle if it has been determined that the vehicle is towing a trailer and that the motor / generator is applying a first deceleration component on (or at) the regenerative axle. The second deceleration component on the non-regenerative axle can ensure stable vehicle handling even when towing a trailer and in regenerative mode.

[0011] The control unit can be configured to reduce the first deceleration component, so that the interaction of the first and second deceleration components results in a predefined total deceleration. In particular, the control unit can be configured to initiate first and second deceleration components, so that a predefined total deceleration of the vehicle remains unchanged.

[0012] The control unit is configured to detect that the vehicle is in overrun mode. Overrun mode can occur, for example, when the driver initiates neither acceleration (by pressing the accelerator pedal) nor deceleration (by pressing the brake pedal). When the combustion engine is used, overrun mode can occur, for example, when the vehicle is decelerated exclusively by the so-called engine brake. Similarly, in a vehicle with an electric or hybrid drive, overrun mode can occur if the vehicle is decelerated exclusively by the deceleration effect of the motor / generator in generator mode (and possibly by the engine brake of the combustion engine). The control unit is configured to distribute a total deceleration of the vehicle corresponding to the overrun mode between the first and second deceleration components, wherein the first and second deceleration components are not equal to zero.

[0013] Depending on the vehicle stability with a trailer, particularly when cornering, the first deceleration component can be reduced if necessary. In order to maintain the overall deceleration, the control unit can be configured so that the second deceleration component is increased in line with the reduction in the first deceleration component. This maintains the overall deceleration of the vehicle. This can, however, lead to a reduction in recuperation power. On the other hand, the second deceleration component on the non-recuperating axle ensures the stability of the vehicle when towing a trailer. The second deceleration component is typically deceleration caused by the vehicle's wheel brakes. The control unit can thus be configured to cause a wheel brake of the vehicle to effect the second deceleration component.

[0014] The control unit can be configured to cause a distribution of the first and second deceleration components to correspond to an installed braking force distribution between the regenerating axle and the non-regenerating axle of the vehicle. In other words, the distribution of the first and second deceleration components can be designed such that the distribution deviates from the installed braking force distribution by the same amount as or less than a predefined distribution threshold value (e.g., 5% or 10%). Typically, the wheel brakes of the vehicle are designed such that, when the brake pedal is actuated, a so-called installed braking force distribution (also known as hydraulic braking force distribution) results between the braking component on the rear axle and the braking component on the front axle. The installed braking force distribution can result from the dimensioning (e.g., diameter of the brake discs and / or piston diameter of the brake calipers) of the wheel brakes.Example distributions of the braking force are approximately 70% of the total deceleration on the front axle and approximately 30% of the total deceleration on the rear axle. Typically, 50% or more of the braking force is applied to the front axle. The control unit can be configured to cause a second deceleration component to be applied to a non-regenerating axle of the vehicle, which is large enough that the distribution of the first (regenerating) deceleration component and the second (non-regenerating) deceleration component corresponds to the installed braking force distribution. To achieve a predetermined total deceleration of the vehicle, the first deceleration component can be reduced if necessary.

[0015] The vehicle may be rear-wheel drive. In particular, the motor / generator and, if applicable, the combustion engine can act (exclusively) on a rear axle of the vehicle. With rear-wheel drive, the regenerative axle corresponds to the rear axle of the vehicle. The non-regenerative axle corresponds to a front axle of the vehicle. The device described in this document for stabilizing the vehicle when towing a trailer is particularly advantageous for rear-wheel drive vehicles.

[0016] The vehicle may have all-wheel drive. The control unit may be configured to open a center coupling between the regenerative axle and the non-regenerative axle when it is determined that the vehicle is towing a trailer and that the motor / generator is causing an initial deceleration on the regenerative axle. Even in all-wheel drive, the regenerative axle may be the rear axle of the vehicle.

[0017] According to a further aspect, a method for stabilizing a vehicle during trailer operation is described. The vehicle comprises a motor / generator configured to drive a regenerative axle of the vehicle during motor operation and to decelerate the regenerative axle of the vehicle during generator operation. The method comprises determining whether the vehicle is towing a trailer. The method further comprises determining whether the motor / generator causes a first deceleration component on the regenerative axle. Furthermore, the method comprises causing a second deceleration component to be applied on a non-regenerative axle of the vehicle if it has been determined that the vehicle is towing a trailer and if it has been determined that the motor / generator causes a first deceleration component on the regenerative axle.

[0018] According to another aspect, a software (SW) program is described. The SW program can be configured to be executed on a processor and thereby to carry out the method described in this document.

[0019] According to a further aspect, a storage medium is described. The storage medium can comprise a software program configured to be executed on a processor and thereby to carry out the method described in this document.

[0020] It should be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspects of the methods, devices, and systems described in this document can be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways.

[0021] The invention will be described in more detail below using exemplary embodiments. Fig. 1a an exemplary vehicle with hybrid drive; Fig. 1b shows an exemplary device for stabilizing an electric vehicle; and Fig. 2 a flowchart of an exemplary method for stabilizing an electric vehicle.

[0022] Fig. Figure 1a shows an exemplary vehicle 100 with a hybrid drive. The vehicle 100 includes wheels 102 on a rear axle 104 and a front axle 106. The wheels 102 can be braked via the rear wheel brakes 103 and the front wheel brakes 105, respectively. The brakes 103, 105 are typically hydraulic brakes that convert the vehicle's kinetic energy into heat through friction.

[0023] The vehicle 100 includes an internal combustion engine 108, which, in the example shown, drives the rear axle 104 via a transmission 107. Consequently, the vehicle 100 shown is a rear-wheel drive vehicle.

[0024] Furthermore, the vehicle 100 includes an electric motor 109, which is also coupled to the rear axle 104 and can drive the rear axle 104. The electric motor 109 is supplied with electrical energy by a battery 110.

[0025] The electric motor 109 can be operated as a generator during deceleration, so that the kinetic energy of the vehicle 100 can be at least partially converted (recovered) into electrical energy by the electric motor 109 operating as a generator. Due to its dual function, the electric motor 109 is also referred to as a motor / generator 109. The recovered electrical energy can be stored in the battery 110 and used to drive the electric motor 109 and the vehicle 100 as needed.

[0026] The vehicle 100 comprises a trailer coupling 101 to which a trailer (e.g. a caravan) can be coupled.

[0027] As already explained above, the motor / generator 109 is driven by the drive axle 104 during deceleration phases in order to recover the kinetic energy of the vehicle 100. If this occurs only via one axle 104, this can lead to unstable handling, especially on road surfaces with a low coefficient of friction. For this reason, the so-called hybrid stability management system intervenes during such deceleration phases and ensures the stabilization of the vehicle 100.

[0028] When towing a trailer, however, the intervention of the hybrid stability management system may come too late, causing the mass of the trailer to impact the vehicle 100 to such an extent that the vehicle 100 becomes uncontrollable. This is particularly the case with rear-wheel drive or rear-wheel drive vehicles 100, where the deceleration effect on the rear axle 104 due to the initiated recuperation may lead to overbraking of the rear axle 104. As a result, when towing a trailer, the high thrust energy of the trailer may lead to a loss of lateral guidance.

[0029] As in Fig. As shown in Figure 1b, the vehicle 100 may include a control unit 120 configured to control or regulate the deceleration of the vehicle 100 caused by the motor / generator 109 and the wheel brakes 103, 105. In particular, the control unit 120 may be configured to divide a desired total deceleration of the vehicle 100 into decelerations caused by the motor / generator 109, by the rear wheel brakes 103, and / or by the front wheel brakes 105.

[0030] In this case, the control unit 120 can be configured to determine whether the vehicle 100 is in trailer operation. This can be signaled, for example, by an explicit signal on a data bus of the vehicle 100. Alternatively or additionally, the control unit 120 can be configured to detect trailer operation based on the additional mass of the trailer.

[0031] The control unit 120 can be configured to always initiate a deceleration component on the non-regenerating axle 106 during a deceleration phase. In other words, if it is detected that the vehicle 100 is towing a trailer, the control unit 120 causes, in addition to the deceleration by the motor / generator 109, a deceleration component on the non-regenerating axle 106 to be caused by the corresponding wheel brakes 105. In particular, the control unit 120 can cause hydraulic pressure to be built up in the wheel brakes 105 of the non-regenerating vehicle axle 106.

[0032] The generation of an additional deceleration component on the non-recuperating axle 106 may result in the deceleration component generated by the motor / generator 109 on the regenerating axle 104 having to be reduced in order to maintain a desired overall deceleration of the vehicle 100. The control unit 120 can be configured to reduce the deceleration component acting on the regenerating axle 104 such that, together with the additional deceleration component on the non-recuperating axle 106, the desired overall deceleration of the vehicle 100 results.

[0033] By redistributing the deceleration from the recuperating axle 104 to the non-recuperating axle 106, a braking force distribution analogous to the installed distribution can be ensured. All four wheels 102 can be braked according to the design so that the rear axle 104 is not over-braked by the recuperation power. The installed braking force distribution typically provides for synchronous hydraulic pressure in the brakes of both axles 104, 106. Depending on the wheel brake dimensioning on the axles, a specific braking force distribution results on both axles 104, 106. If deceleration is carried out regeneratively on one axle (i.e. by a motor / generator 109), the corresponding braking pressure can be built up on the other axle by conversion in exactly the same ratio as with hydraulic deceleration, so that deceleration forces are generated on both axles that are identical to the installed braking force distribution.If the current deceleration component is maintained through recuperation and the corresponding pressure is applied on the other axle, the vehicle's deceleration increases. If the vehicle's deceleration is to remain constant, the deceleration component is reduced by recuperation in proportion to the increase in the deceleration component on the other axle. The goal is to adjust the ratio of the deceleration components on both axles to match the brake force distribution in purely hydraulic driver braking.

[0034] In all-wheel drive vehicles, the deceleration components can also be redistributed during trailer operation from the regenerative axle 104 to the non-regenerative axle 106. For this purpose, a center coupling (not included in Fig. 1a) between the rear axle 104 and the front axle 106. The control unit 120 can be configured to initiate the opening of the center coupling during deceleration phases when towing a trailer. After the center coupling is opened, the deceleration component of the recuperating axle 104 caused by the motor / generator 109 can be at least partially redistributed to the non-recuperating axle 106.

[0035] It should be noted that in some all-wheel drive concepts, recuperation occurs via the front axle 106 and the rear axle 104. In this case, too, the control unit 120 can be configured to initiate the opening of the center coupling during trailer operation and to supplement the deceleration component on the recuperating axle 104 with a deceleration component on the non-recuperating axle 106. This ensures stable deceleration during trailer operation even with all-wheel drive.

[0036] The control unit 120 can be configured to effect the described redistribution of the deceleration components during coasting of the vehicle 100. This means that the redistribution can also occur when the brake pedal is not depressed. In particular, the control unit 120 can be configured to cause a deceleration component by the wheel brakes 105 of the non-recuperating axle 106, in addition to the deceleration component caused by the motor / generator 109 on the regenerative axle 104.

[0037] The control unit 120 can be configured to ensure that, in trailer operation, approximately 50% of the deceleration of the vehicle 100 permissible in conjunction with recuperation occurs via the recuperating axle 104 and approximately 50% of the deceleration of the vehicle occurs via the non-recuperating axle 106.

[0038] Fig. 2 shows a flowchart of an exemplary method 200 for stabilizing a vehicle 100 in trailer operation. As in connection with Fig.1a, the vehicle 100 comprises a motor / generator 109, which is configured, in motor mode, to drive a recuperating axle 104 of the vehicle 100, and, in generator mode, to decelerate the recuperating axle 104 of the vehicle 100. The recuperating axle 104 is preferably a rear axle of the vehicle 100. The method 200 comprises determining 201 whether the vehicle 100 is towing a trailer. This can be done, for example, based on suitable bus signals. Furthermore, the method 200 comprises determining 202 whether the motor / generator 109 causes a first deceleration on the recuperating axle 104. The motor / generator 109 is configured to convert at least portions of the first deceleration portion of the vehicle 100 into electrical energy, wherein the electrical energy can be stored in the battery 110 of the vehicle 100.

[0039] The method 200 further includes causing 203 a second deceleration component to be caused on the non-regenerating axle 106 of the vehicle 100. The non-regenerating axle 106 is preferably the front axle of the vehicle. The second deceleration component is not equal to zero. The second deceleration component can be generated, for example, by the wheel brakes 105 of the non-regenerating axle 106. The second deceleration is caused in particular when it has been determined that the vehicle 100 is towing a trailer and that the motor / generator 109 causes a first deceleration component (not equal to zero) on the regenerating axle 104.

[0040] By dividing the total deceleration of the vehicle 100 into a deceleration component at the recuperating axle 104 and a deceleration component at the non-recuperating axle 106, the recuperation power is typically lower than if deceleration were achieved entirely by recuperation, if the total deceleration is to remain the same. On the other hand, this ensures that the vehicle always remains within a stable deceleration range, even when towing a trailer, because no axle is overbraked. In particular, this division of the total deceleration enables trailer towing in hybrid vehicles or electric vehicles.

[0041] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and figures are intended only to illustrate the principle of the proposed methods, devices, and systems.

Claims

[1] Control unit (120) for a vehicle (100), wherein the vehicle (100) comprises a motor / generator (109) which is configured to drive a recuperating axle (104) of the vehicle (100) in motor mode and to decelerate the recuperating axle (104) of the vehicle (100) in generator mode, wherein the control unit (120) is configured - to determine whether the vehicle (100) is towing a trailer; - to determine whether the motor / generator (109) causes a first deceleration component on the recuperating axle (104); - to cause a second deceleration component to be effected on a non-recuperating axle (106) of the vehicle (100) if it has been determined that the vehicle (100) is pulling a trailer and that a first deceleration component is effected on the recuperating axle (104) by the motor / generator (109), characterized by , that - to detect that the vehicle (100) is in overrun mode; - to distribute a total deceleration corresponding to the overrun operation between the first and second deceleration components, whereby the first and second deceleration components are not equal to zero. [2] Control unit (120) according to claim 1, wherein the control unit (120) is configured to reduce the first delay component so that the interaction of the first and second delay components results in a predefined total delay. [3] Control unit (120) according to any preceding claim, wherein the control unit (120) is arranged to cause a wheel brake (105) of the vehicle (100) to effect the second deceleration component. [4] Control unit (120) according to any preceding claim, wherein the control unit (120) is configured to cause a distribution of the first and second deceleration components to correspond to an installed braking force distribution between the regenerative axle (104) and the non-regenerative axle (106) of the vehicle (100). [5] Control unit (120) according to any preceding claim, wherein - the vehicle (100) comprises a rear-wheel drive; - the recuperating axle (104) is a rear axle of the vehicle (100); and - the non-recuperating axle (106) is a front axle of the vehicle. [6] Control unit (120) according to any preceding claim, wherein - the vehicle (100) comprises an all-wheel drive; and - the control unit is configured to open a center coupling between the recuperating axle (104) and the non-recuperating axle (106) when it has been determined that the vehicle (100) is pulling a trailer and that a first deceleration component is effected on the recuperating axle (104) by the motor / generator (109). [7] Control unit (120) according to any preceding claim, wherein the control unit (120) is arranged - to receive a signal; and / or - to determine a load of the vehicle (100) in order to determine whether the vehicle (100) is towing a trailer. [8] Control unit (120) according to any preceding claim, wherein the vehicle (100) comprises an internal combustion engine (108) forming a hybrid drive with the motor / generator (109). [9] Method (200) for stabilizing a vehicle (100) in trailer operation; wherein the vehicle (100) comprises a motor / generator (109) which is configured to drive a recuperating axle (104) of the vehicle (100) in motor operation and to decelerate the recuperating axle (104) of the vehicle (100) in generator operation, the method (200) comprising - determining (201) whether the vehicle (100) is towing a trailer; - determining (202) whether the motor / generator (109) causes a first deceleration component on the recuperating axle (104), - Causing (203) a second deceleration component to be effected on a non-recuperating axle (106) of the vehicle (100) if it has been determined that the vehicle (100) is pulling a trailer and that a first deceleration component is effected on the recuperating axle (104) by the motor / generator (109) characterized by , that - detecting that the vehicle (100) is in overrun mode; - Distributing a total deceleration corresponding to the overrun operation between the first and second deceleration components, wherein the first and second deceleration components are not equal to zero.

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