Vehicle with starter aid

Abstract

A vehicle starter aid system is provided for a vehicle having at least one driven axle and at least one non-driven axle. An electrically controllable brake system generates brake application signals as a function of input signals for the wheel brake actuators on the at least one driven axle. The inputs signals are received from a rotational speed sensor of the at least one non-driven axle and at least one signal-generator which generates signals which represent intended driving away of the vehicle from the stationary state and are different from the wheel rotational speed signals. An electronic brake control unit controls application of the wheel brake actuators of the at least one driven axle if the rotational speed signals of the rotational speed sensor correspond to zero wheel rotational speed and at the same time the signals of the signal-generator indicate the intended driving away of the vehicle.

Claims

1. A vehicle, comprising: at least one driven axle; at least one nondriven axle; wheel brake actuators provided on the at least one driven axle and on the at least one nondriven axle; an electrically controllable brake system which includes at least one electronic brake control unit configured to feed brake application signals to the wheel brake actuators; a wheel rotational speed sensor on at least one wheel of the at least one nondriven axle, the wheel rotational speed sensor being configured to generate wheel rotational speed signals; and a signal generator configured to generate signals which differ from the wheel rotational speed signals and which represent an intended driving away of the vehicle from the stationary state, wherein at least one of the wheel rotational speed signals and the signal generator signals are input signals to the electronic brake control unit, and the at least one electronic brake control unit is configured to generate brake application signals for at least partial application of the wheel brake actuators on the at least one driven axle in dependence on the input signals, feed the brake application signals into the wheel brake actuators of the at least one driven axle if the rotational speed signals of the rotational speed sensor correspond to a rotational speed of zero and at the same time the signals of the signal-generator correspond to an intended driving away of the vehicle from the stationary state, and not feed brake application signals into the wheel brake actuators of the at least one driven axle if the rotational speed signals of the at least one rotational speed sensor correspond to a rotational speed that is not zero.

2. The vehicle as claimed in claim 1, wherein the signals of the signal-generator are dependent on a rotational speed of a transmission output shaft of a transmission of the vehicle.

3. The vehicle as claimed in claim 2, wherein the signal-generator includes at least one active rotational speed sensor configured to measure the rotational speed of the transmission output shaft of the transmission and feed the transmission shaft rotational speed to the electronic brake control unit.

4. The vehicle as claimed in claim 1, wherein the signal-generator signals are generated by an actuation of at least one of a hand-actuable actuating member and a foot-actuable actuating member operable by a driver of the vehicle.

5. The vehicle as claimed in claim 4, wherein the signals of the signal-generator are dependent on at least one of an engaged or disengaged state of a clutch of the vehicle, a selected transmission gear stage, a selected transmission mode of the transmission, an actuation or nonactuation of a brake pedal, an actuation or nonactuation of a gas pedal, and an actuation or nonactuation of an actuating member of the parking brake.

6. The vehicle as claimed in claim 5, wherein the signal-generator includes an additional actuating member configured to be actuated separately by the driver, and the additional actuating member is configured to generate, independently of an actuation of the clutch, the transmission, the brake pedal, the gas pedal, and the parking brake of the vehicle, the signals which differ from wheel rotational speed signals generated by a wheel rotational speed sensor which represent an intended driving away of the vehicle from the stationary state.

7. The vehicle as claimed in claim 1, wherein the brake application signals provided to the wheel brake actuators of the at least one driven axle cause the wheel brake actuators of the at least one driven axle to apply at least a temporarily acting brake torque on the wheels of the at least one driven axle.

8. The vehicle as claimed in claim 7, wherein the at least temporarily acting brake torque on the wheels of the at least one driven axle increases in ramp form from zero up to a predetermined value, immediately increases to the predetermined value, or acts over one or more predetermined time intervals.

9. The vehicle as claimed in claim 1, wherein the electrically controllable brake system is at least one of a service brake system and a parking brake system.

10. The vehicle as claimed in claim 1, wherein the electronic brake control unit is configured to control a function of one or more of a brake slip control (ABS), an electronic parking brake (EPB), a traction slip control (ASR), and an electronic stability program (ESP).

11. The vehicle as claimed in claim 1, wherein the electrically controllable brake system is an electronically controlled electropneumatic brake system.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The FIGURE shows a schematic illustration of parts of a vehicle having an electropneumatic brake system according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWING

(2) An embodiment shown in the FIGURE of a vehicle 1, in particular a heavy commercial vehicle, has, for example, an electropneumatic, electronically controlled brake system EBS in which the brake forces are electronically controlled. The electronically controlled brake system EBS preferably has ABS, ASR and ESP functionalities and is therefore capable of separately braking, via its brake control unit 2, only wheel brakes 4 on a driven rear axle 6 without at the same time applying wheel brakes 8 on a nondriven front axle 10. However, in normal braking operation, the brake control unit 2 can apply in parallel the wheel brakes 4, 8 also on both axles 6, 10. Here, the wheel brakes 4, 8 include, for example, pneumatic brake cylinders which act on brake actuators such as disk brakes.

(3) There is therefore present in the vehicle 1 the nondriven front axle 10 with two front wheels 12, the driven rear axle 6 with preferably two driven rear wheels 14, an engine 16, a transmission 18, a clutch 20 arranged between engine 16 and transmission 18, and a transmission output shaft 22 which here, for example, drives the wheels 14 of the rear axle 6 via a cardan shaft and a rear axle differential.

(4) Also provided in the vehicle 1 are pneumatic lines 24, 26, 28, 30, 32, 34 of the electropneumatic, electronically controlled brake system EBS for conducting control pressures or braking pressures, and also data lines 36, 38, 40, 42, 44, 46, 48, 50 which are indicated by dashes and via which information and control commands are transmitted.

(5) The pneumatic lines 28 and 34 and the data line 50 are connected to a brake value transmitter 54 with brake pedal 56 for the service brake of the electropneumatic, electronically controlled brake system EBS, wherein this brake value transmitter 54 here has two pneumatic channels, a pneumatic channel 58 for the control pressures of the front axle 10 and a pneumatic channel 60 for control pressures of the rear axle 6 and an electrical channel 62. The two pneumatic channels 58 and 60 are each supplied with compressed air by a dedicated compressed-air supply (not shown here) for the relevant axle.

(6) Therefore, on the one hand, upon actuating the brake pedal 56 of the brake value transmitter 54, an electrical braking request signal is fed into the electronic brake control unit 2 via the data line 50. From there, a pressure-regulating module 64 for the wheel brakes 8 of the front axle 10 and a pressure-regulating module 66 for the rear brakes 4 of the rear axle 6 are electrically activated via the data lines 38, 42. In parallel to this, on the other hand, a corresponding control pressure passes into the pressure-regulating modules 64, 66 via the pneumatic lines 28 and 34 upon the actuation of the brake pedal 56, which control pressure, however, can become active there only when the electrical control via the electrical channel 62, the data lines 50, 38 and 42 and the electronic brake control unit 2 fails. The pressure-regulating modules 64, 66 each contain in a known manner an inlet-outlet solenoid valve combination which controls an integrated relay valve, a backup solenoid valve for retaining the pneumatic control pressure in the pressure lines 28 and 34 and a pressure sensor for each channel and are each connected to the relevant compressed-air supply for the front axle 10 or for the rear axle 6. Furthermore, the pressure-regulating modules 64 and 66 are here preferably each designed as 2-channel pressure-regulating modules, wherein in each case one channel regulates the braking pressure in a wheel brake 4, 8 on one vehicle side to the respectively desired setpoint braking pressure.

(7) Therefore, the EBS here preferably has an electropneumatic front axle brake circuit and an electropneumatic rear axle brake circuit.

(8) In dependence on the electrical braking request signals in the electrical channel 62 or in dependence on the pneumatic control pressures in the pneumatic channels 58, 60 of the brake value transmitter 54, the pressure-regulating modules 64, 66 then feed corresponding braking pressures into the wheel brakes 8 of the front axle via the pneumatic lines 24, 26 and into the wheel brakes 4 of the rear axle 6 via the pneumatic lines 30, 32.

(9) The electronically controlled brake system EBS is preferably equipped with a brake slip control ABS. For this purpose and for further functions, such as, for example, ASR and ESP, the front wheels 12 and rear wheels 14 are each assigned wheel rotational speed sensors 68, 70. Therefore, upon braking, the actual wheel rotational speeds are communicated to the electronic brake control unit 2 by the data lines 36, 48 or 40, 44 and an actual brake slip is calculated there for each wheel. If this actual brake slip exceeds a predetermined setpoint brake slip, the brake control unit 2 preferably regulates the braking pressure channelwise via the pressure-regulating modules 64, 66 such that the setpoint brake slip on the relevant wheel 12, 14 is no longer exceeded.

(10) The wheel rotational speed sensors 70 on the rear axle are preferably configured as passive wheel rotational speed sensors. On the one hand, they do not detect the direction of rotation of the wheels 14 on the rear axle 6. Nor is a speed detection at very low speeds possible. However, for the brake slip control (ABS) from average and high speeds, this is not necessary. In this respect, they are relatively cost-effective.

(11) Passive or active wheel rotational speed sensors 68 can likewise be arranged on the wheels 12 of the nondriven front axle 10. These wheel rotational speed sensors 68 feed wheel rotational speed signals into the brake control unit 2 via the data lines 36, 48. If active wheel rotational speed sensors 68 are used, they allow, by contrast to the passive rotational speed sensors, a reliable detection even of very low rotational speeds and speeds and the direction of rotation of the wheels 12 of the nondriven front axle 10, which can have an advantageous effect on the detection of starting. In particular, they can determine the difference between the rotational speed zero and a very low rotational speed of the wheels 12 on the front axle 10, which results in an improvement in the starting detection. However, the principle also functions with passive sensors.

(12) Furthermore, an active rotational speed sensor 72, which is connected to a transmission control unit 74 via the data line 46, can also be provided on the transmission output shaft 22 of the transmission 18. The transmission output shaft 22 is rotationally coupled to the rear wheels 14 in a manner not shown here, with the result that a rotation of the rear wheels 14 and the direction of rotation thereof can be detected by the active rotational speed sensor 72 and the signals are fed into the transmission control unit 74 as input signals.

(13) As shown, the data lines 36 to 44 and 48 to 50 can be directly connected to the brake control unit 2 or else be connected to the brake control unit 2 by a data bus, for instance a CAN bus.

(14) The rotational speed sensors 68 and 72 can be designed in such a way that they sense teeth of gearwheels (not shown here) on the transmission output shaft 22 or on drive shafts of the front axle 10. Alternatively, the transmission output shaft 22 and the drive shafts can also have provided thereon additional pole rings with toothing which are then sensed by the rotational speed sensors 68 and 72.

(15) The transmission 18 is preferably an automated transmission with the transmission control unit 74. The clutch 20 is here electrically actuated, for example, by the transmission control unit 74. The transmission control unit 74 and brake control unit 2 are both connected to a CAN bus 76. Consequently, the data of the active rotational speed sensor 72 which measures the rotational speed of the transmission output shaft 22 are here distributed via the transmission control unit 74 and the CAN bus 76 and are thus also available to the brake control unit 2. Furthermore, a signal which delivers information on the position of a selector lever (not shown here) of the automated transmissionNeutral, Drive, Reverse or Parkis also available to the brake control unit 2 via the data bus 76.

(16) According to an embodiment not shown here, the transmission 18 could also be a nonautomated manual shift transmission. In this case, the brake control unit 2 receives a signal which delivers information on the position of a gear lever of the transmissionNeutral, Gear stage, Reverse gearvia a corresponding sensor and by means of a data line.

(17) Furthermore, an engine control unit 78 which controls the engine 16 is also connected to the data bus 76. An electric gas pedal 80 which has at least one sensor for measuring the gas pedal position and/or the actuation speed of the gas pedal 80 feeds a drive request signal corresponding to the degree of actuation of the gas pedal 80 into the engine control unit 78. Since the engine control unit 78 is also connected to the data bus 76, a signal which delivers information on an actuation or nonactuation of the gas pedal 80 and in particular also on its degree of actuation is also available to the brake control unit 2 via the data bus 76.

(18) The electric clutch 20 is controlled by an electrical signal of the transmission control unit 74 which, by being fed via the data bus 76 also into the brake control unit 2, then provides the latter with information on the state of the clutch 20engaged or disengaged. Furthermore, a sensor is also present on the gas pedal 56 through the electrical channel 62 of the brake value transmitter 54, which sensor feeds the actuating state of the gas pedal 56unactuated, generally actuated or degree of actuationinto the brake control unit 2 via the data line 50. Last but not least, a nonactuated parking brake which the vehicle here also preferably has can also represent a signal for an intended driving away of the vehicle from the stationary state. The actuation or nonactuation of an operating member of the parking brake can be determined by a corresponding electrical signal, especially if the parking brake is electrically controlled.

(19) An intended driving away of the vehicle 1 from the stationary state can then be signaled to the brake control unit 2 via signals from at least one of the sensors 22, 62 and 80 present here. If, for example, it is determined by the electronic brake control unit 2 that the instantaneous rotational speed of the transmission output shaft 22 of the transmission 18 which is measured by the active rotational speed sensor 72 is greater than a rotational speed which corresponds to the idle speed or to an idle rotational speed band of the engine 16 which contains a tolerance, this indicates an intended driving away of the vehicle 1 from the stationary state.

(20) Furthermore, for example, an actuated gas pedal 80, a selector lever in the driving position (Drive or Reverse) of the here preferably automated transmission 18, an unactuated brake pedal 56 and a clutch 20 in the engaged state indicate an intended driving away of the vehicle 1 from the stationary state.

(21) Therefore, a detection of an intended driving away of the vehicle 1 from the stationary state preferably occurs here automatically by means of at least one of the stated sensors 62, 72 and 80. The sensor signals of this at least one sensor 62, 72 and 80 are then compared with reference values in the brake control unit 2 in order to be able to identify an intended driving away.

(22) Alternatively or in addition, an additional actuating member 82 which can be actuated separately by the driver and which is likewise connected to the brake control unit 2 via a data line 84 can also be present.

(23) The additional actuating member 82 which can be actuated separately by the driver is provided and designed in such a way that, independently of the further actuating members which can be actuated by the driver, such as brake pedal 56 or gas pedal 80, it can generate signals which represent an intended driving away of the vehicle 1 from the stationary state and are fed as input signals into the electronic brake control unit 2. The additional actuating member 82 which can be actuated separately by the driver can here include, for example, a changeover switch which is integrated into a current circuit and is actuated by a lever, wherein the driver can pivot the lever into an on position and into an off position. In the on position, a signal representing an intended driving away of the vehicle 1 from the stationary state is then fed into the brake control unit 2, and in the off position, the generation of this signal is prevented.

(24) The driver can, for example, move the lever of the actuating member 82 from the off position into the on position if he or she has determined that a driving away from the stationary state on slippery ground is not possible without excessive traction slip, that is to say if the wheels 14 of the driven rear axle 6 spin upon starting.

(25) The above-described components and subassemblies designed in a preferred manner make it possible to realize a starter aid for the vehicle 1 if the wheels 14 of the driven rear axle 6 spin on slippery ground and an excessive traction slip is to be avoided.

(26) The electronic brake control unit 2 is then designed in such a way that it at least temporarily feeds brake application signals into the pressure-regulating module 66 of the driven rear axle 6 if the rotational speed signals of the rotational speed sensors 68 on the front axle 10 correspond to a rotational speed equal to zero and at the same time the signals of at least one sensor from the group consisting of the active rotational speed sensor 72 on the transmission output shaft 22 and/or of the electrical channel 62 of the brake value transmitter 54 and/or of the sensor of the gas pedal 80 indicate an intended driving away of the vehicle 1 from the stationary state. The intended driving away of the vehicle 1 from the stationary state is then automatically detected. Here, however, the signals of the wheel rotational speed sensors 70 on the wheels 14 of the rear axle 6 are preferably not taken into consideration because their speed resolution at low speeds is too low.

(27) Alternatively or in addition, the signal which is generated by the driver when placing the additional actuating member 82 into the on position and is fed into the brake control unit 2 can also represent the intended driving away of the vehicle 1 from the stationary state.

(28) If therefore the rotational speed sensors 68 on the front axle 10 detect a rotational speed equal to zero, this indicates that the vehicle is still at a standstill although the signals of the further sensors 22, 62 and 80 already signal an intended driving away of the vehicle 1 from the stationary state, for example through an actuated gas pedal 80 and/or through an unactuated brake pedal 56 and/or through a rotational speed of the rotating transmission output shaft 22 that is higher than the idle rotational speed. It is therefore to be assumed in this case that the wheels 14 of the rear axle 6 spin on the ground and an excessive traction slip is present.

(29) The brake control unit 2 then therefore generates brake application signals exclusively for the pressure-regulating module 66 of the driven rear axle 6 in order to generate a brake torque on the rear axle 6 that acts against the drive torque which is too high because it leads to the spinning of the wheels 14.

(30) In addition, the driver also recognizes the need for the starter aid by virtue of the fact that, in spite of the selector lever of the transmission 18 in the Drive position, unactuated brake pedal 56 and actuated gas pedal 80, the vehicle 1 does not move and the wheels 14 on the rear axle 6 spin. The driver can then optionally actuate the actuating member 82 into the on position, with the result that an input signal is fed into the electronic brake control unit 2, whereupon the latter generates a braking force on the wheel brakes 4 of the rear axle 6.

(31) The starter aid thus consists in a generation of braking force/brake torque on the driven rear axle 6 in order to counteract the spinning of the wheels 14. In general, an automatic activation of the starter aid by means of the above-described sensor system 22, 56, 68 and 80 on the one hand and an activation of the starter aid by the driver by means of the actuating member 82 are possible alternatively or in a mutually complementary manner.

(32) Here, the ASR, ABS and ESP functionalities implemented in the electronic brake control unit 2 allow a slow increase of the braking forces, here in electropneumatic brakes of the braking pressure in the wheel brakes 4, for example pneumatic wheel brake cylinders of the driven rear axle 6, first to the application pressure (for example 0.3 bar), and then a slow, ramplike increase (for example 0.2 bar/s) up to a predetermined value. Also conceivable, however, is an abrupt increase from zero to a parameterized value of the braking pressure.

(33) The invention is not limited to electropneumatic brake systems, but it can also be realized in all electrically controllable braking systems, such as, for example, purely electrically operating brake systems or else in electrohydraulic brake systems.

(34) Alternatively or in addition to the braking engagement, the drive torque of the engine 16 can also be reduced if the need for the starter aid is automatically recognized and then activated and/or the starter aid is triggered via the actuator member 82. The brake control unit 2 then (also) controls the engine control unit 78 in order to reduce the drive torque when spinning of the wheels 14 of the driven rear axle 6 is detected automatically or by the driver.

(35) If then after some time the rotational speed signals of the rotational speed sensors 68 on the front axle 10 communicate a rotational speed which is unequal to zero to the brake control unit 2, which signals that traction is then present and the vehicle moves in the desired direction, the brake control unit 2 then no longer feeds brake application signals into the pressure-regulating module 66 of the driven rear axle 6, with the result that the wheel brakes 4 release there. Alternatively or in addition to this, the driver, after having recognized the presence of traction on the rear axle 6, can also move the actuating member 82 from the on position into the off position again, with the result that the starter aid is also deactivated by the brake control unit 2.

(36) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

LIST OF REFERENCE SIGNS

(37) 1 vehicle

(38) 2 brake control unit

(39) 4 rear-axle wheel brakes

(40) 6 rear axle

(41) 8 front-axle wheel brakes

(42) 10 front axle

(43) 12 front wheels

(44) 14 rear wheels

(45) 16 engine

(46) 18 transmission

(47) 20 clutch

(48) 22 transmission output shaft

(49) 24 pneumatic line

(50) 26 pneumatic line

(51) 28 pneumatic line

(52) 30 pneumatic line

(53) 32 pneumatic line

(54) 34 pneumatic line

(55) 36 data line

(56) 40 data line

(57) 42 data line

(58) 44 data line

(59) 46 data line

(60) 48 data line

(61) 50 data line

(62) 54 brake value transmitter

(63) 46 brake pedal

(64) 58 front-axle pneumatic channel

(65) 60 rear-axle pneumatic channel

(66) 62 electrical channel

(67) 64 front-axle pressure-regulating module

(68) 66 rear-axle pressure-regulating module

(69) 68 front-axle wheel rotational speed sensors

(70) 70 rear-axle wheel rotational speed sensors

(71) 72 rotational speed sensor

(72) 74 transmission control unit

(73) 76 CAN data bus

(74) 78 engine control unit

(75) 80 gas pedal

(76) 82 actuating member

(77) 84 data line