METHOD AND BRAKE SYSTEM FOR ACTUATING A BRAKE ACTUATOR IN ORDER TO REDUCE TENSIONING OF A VEHICLE

Abstract

In a method for actuating a brake actuator in a braked, stationary vehicle, a state variable defining a state of loading of the vehicle is monitored and a stress in the vehicle produced by a level change is detected. The state variable is compared with a predefined value range and the brake actuator is released in response to the detection of a stress. For the case wherein the state variable can be assigned to the predefined value range, a first target braking level is actuated and/or, for the case in which the state variable cannot be assigned to the predefined value range, a second target braking level is actuated.

Claims

1. A method for actuating a brake actuator in a braked, stationary vehicle, the method comprising the steps: a) monitoring a state variable (Z.sub.1, Z.sub.2, Z.sub.3) defining a state of loading of the vehicle; b) detecting stress in the vehicle produced by a level change; c) comparing the state variable (Z.sub.1, Z.sub.2, Z.sub.3) with a predefined value range; and, d) releasing the brake actuator in response to the detection of the stress, wherein: for the case wherein the state variable (Z.sub.1, Z.sub.2, Z.sub.3) is assignable to the predefined value range, actuating a first target braking level; and, for the case wherein the state variable (Z.sub.1, Z.sub.2, Z.sub.3) cannot be assigned to the predefined value range, actuating a second target braking level.

2. The method of claim 1, wherein the first target braking level is defined as a function of the state variable (Z.sub.1, Z.sub.2, Z.sub.3) and the second target braking level is a discrete value.

3. The method of claim 1, wherein: the state variable is a first state variable (Z.sub.1), which defines a first state of loading and which, in step c), is compared with a first predefined value range; and, at least one second state variable (Z.sub.2) is monitored, which defines a second state of loading of the vehicle and which, in step c), is compared with a second predefined value range.

4. The method of claim 3, wherein: in step d), the first target braking level is actuated for the case wherein the first state variable (Z.sub.1) is assignable to the first predefined value range and the second target braking level (Z.sub.2) is assignable to the second predefined value range; and, in step d), a third target braking level is actuated for the case wherein the second state variable (Z.sub.2) cannot be assigned to the second predefined value range.

5. The method of claim 1, wherein a state of loading is a positional state and a state variable (Z.sub.1) is an angle of inclination () of the vehicle relative to the horizontal.

6. The method of claim 5, wherein the angle of inclination () is monitored by sensing an acceleration of the vehicle via a sensor unit.

7. The method of claim 5, wherein the predefined value range includes angles of inclination () lying in at least one of the following ranges: i) 0<|90|; ii) 0<|12|; iii) 0<|7|; and, iv) |7|<|10%.

8. The method of claim 5, wherein the first target braking level is defined as a ratio of the braking force f.sub.b()=m.Math.g.Math.sin and the weight f.sub.g(g)=m.Math.g in percent, and the second target braking level assumes a value <1%.

9. The method of claim 1, wherein a state of loading is a state of loading and a state variable (Z.sub.2) is a pressure of a suspension.

10. The method of claim 9, wherein the state of loading is monitored by sensing an air suspension bellows pressure of a pneumatic suspension or a hydraulic pressure of a hydraulic suspension via a sensor unit.

11. The method of claim 9, wherein: the predefined value range comprises pressures in a range of 0.1 bar<p<200 bar; the suspension is a pneumatic suspension and the predefined value range comprises pressures in a range of 0.1 bar<p<10 bar; or, the suspension is a hydraulic suspension and the predefined value range comprises pressures in a range of 2.5 bar<p<200 bar; and, wherein the second target braking level corresponds to the maximum target braking level in a fully loaded vehicle.

12. The method of claim 1, wherein a state of loading is a state of loading and a state variable (Z.sub.3) is a spring compression travel of a mechanical suspension.

13. The method of claim 1, wherein in step b), stressing of the vehicle is detected for the case in which the following conditions are satisfied: i) the vehicle is at a standstill; and, ii) the vehicle is braked; and, iii) a level change falls above or below a limiting value.

14. The method of claim 1, wherein the vehicle has at least one axle and wherein the axle is respectively assigned two brake actuators which, in step d), are actuated simultaneously.

15. A brake system including an electronically controllable pneumatic brake system for a vehicle for actuating a brake actuator in a braked, stationary vehicle, the brake system comprising: a sensor unit for monitoring a state variable (Z.sub.1, Z.sub.2, Z.sub.3) defining a state of loading of the vehicle; a displacement sensor for detecting a stress in the vehicle produced by a level change; and, a control device having a signal connection to said sensor unit and to said displacement sensor; said control device being configured to release the brake actuator in a response to the detection of a stress and wherein at least one of the following applies: i) for the case wherein the state variable (Z.sub.1, Z.sub.2, Z.sub.3) can be assigned to the predefined value range to actuate a first target braking level; and, ii) for the case wherein the state variable (Z.sub.1, Z.sub.2, Z.sub.3) cannot be assigned to the predefined value range to actuate a second target braking level.

16. The brake system of claim 15, wherein: a state of loading is a positional state and a state variable (Z.sub.1) is an angle of inclination () of the vehicle relative to the horizontal; and, the sensor unit has an acceleration sensor for monitoring the angle of inclination ().

17. The brake system of claim 15, wherein: a state of loading is a state of loading and a state variable (Z.sub.2) is a pressure of a suspension; and, said sensor unit has an acceleration sensor for monitoring the pressure.

18. The brake system of claim 15, wherein: a state of loading is a state of loading and a state variable (Z.sub.3) is a spring compression travel of a mechanical suspension; and, said sensor unit has a displacement sensor for monitoring the spring compression travel.

19. A vehicle including a commercial vehicle, the vehicle comprising: an axle suspended on trailing arms or semi-trailing arms; and, a brake system for actuating a brake actuator in a braked, stationary vehicle; said brake system including: a sensor unit for monitoring a state variable (Z.sub.1, Z.sub.2, Z.sub.3) defining a state of loading of the vehicle; a displacement sensor for detecting a stress in the vehicle produced by a level change; and, a control device having a signal connection to said sensor unit and to said displacement sensor; said control device being configured to release the brake actuator in a response to the detection of a stress and wherein at least one of the following applies: i) for the case wherein the state variable (Z.sub.1, Z.sub.2, Z.sub.3) can be assigned to the predefined value range to actuate a first target braking level; and, ii) for the case wherein the state variable (Z.sub.1, Z.sub.2, Z.sub.3) cannot be assigned to the predefined value range to actuate a second target braking level.

20. The vehicle of claim 19, wherein the vehicle is a semi-trailer truck including an air-sprung semi-trailer truck having: a tractor with an axle suspended on trailing arms or semi-trailing arms; a trailer that can be connected to the tractor; and, said trailer having an axle suspended on trailing arms or semi-trailing arms.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0069] The invention will now be described with reference to the drawings wherein:

[0070] FIG. 1 shows a semi-trailer truck with tractor and trailer, wherein the trailer has been lowered once, schematically in a side view;

[0071] FIG. 2 shows a semi-trailer truck with tractor and trailer, wherein the trailer has been raised once, schematically in a side view;

[0072] FIG. 3 shows a semi-trailer truck with tractor and trailer, wherein the semi-trailer truck is standing on ground with a slope, schematically in a side view;

[0073] FIG. 4 shows the semi-trailer truck according to FIGS. 1 to 3, schematically in a top view; and,

[0074] FIG. 5 shows a second embodiment of a semi-trailer truck, schematically in a top view.

DETAILED DESCRIPTION

[0075] FIGS. 1 to 3 show a vehicle 100. The vehicle 100 in the present case is a semi-trailer, which here includes a tractor 11 with fifth-wheel plate 12 and a trailer 13 with king pin 14.

[0076] The tractor 11 has a front axle 15 and a rear axle 16 respectively. The trailer 13 has an axle 17, which is mounted on an axle swinging arm 18. The axle swinging arm 18 is pivotable about a bearing point 19 and forms a trailing arm for the axle 17.

[0077] The axle 17 is adjustable in height via an air suspension bellows 20 which acts on the axle swinging arm 18 opposite the bearing point 19. In FIG. 1, the air suspension bellows 20 is minimally filled, while FIG. 2 and FIG. 3 show a maximally filled air suspension bellows 20. In a corresponding way, the level of the trailer 13 is considerably lower in FIG. 1 than in FIG. 2 or FIG. 3. Here, the distance of the axle 17 from the vehicle body 21 of the trailer 13 is designated as the level.

[0078] The semi-trailer 100 has an electro-pneumatic brake system 10 and a suspension 3. In the embodiment shown, the suspension 3 is an electronically regulated pneumatic suspension. This permits automatic level regulation during the loading and specific adaptation of the height of the vehicle body 21 to a loading ramp.

[0079] Stressing occurs, for example, between the states illustrated in FIG. 1 and FIG. 2 and FIG. 3. In FIG. 1, the level of the trailer 13 has been lowered for travel. The wheelbase, or, here, the distance between the axle 17 and the king pin 14, is illustrated by a double arrow a. In FIG. 2 and FIG. 3, the level of the trailer 13 has been raised. Accordingly, the axle swinging arm 18 has pivoted downward. As a result, there is a new, shorter distance according to the double arrow b between the axle 17 and the king pin 14 (cf. FIG. 2). When the wheels 23, 24 of the rear axle 16 and the axle 17 are braked, the result is high stress in the trailer 13, which can be so pronounced that, starting from FIG. 1, the state according to FIG. 2 and FIG. 3 cannot be reached. In the meantime, it is necessary to dissipate the stress by at least slightly releasing the parking brake 25 (cf. FIGS. 4 and 5) by actuating the respective brake actuator 8 of the electro-pneumatic brake system 10 via the brake system 1.

[0080] FIG. 4 shows the vehicle floor 22 of the semi-trailer 100 according to FIGS. 1 to 3 in detail.

[0081] The electro-pneumatic brake system 10 shown in detail in FIG. 4 has an electronically controllable pneumatic brake system 1 in conjunction with a number of electronically regulated pneumatic brake actuators 8 and a compressed air supply (not shown) for the brake actuators 8, wherein at least two brake actuators 8 are assigned to the rear axle 17.

[0082] The brake system 1 is configured to detect stressing of the semi-trailer 100 and to release the brake actuator 8 of the electro-pneumatic brake system 10 to dissipate the stress by actuating a target braking level.

[0083] The brake system 1 includes, in particular, an in particular single-circuit electro-pneumatic system component with the control device 6, an axle modulator 25 assigned to the axles 17, a braking value transmitter (not shown) and two ABS valves (not shown) assigned to the axles 17. The axle modulator 25 thus has a signal connection to the control device 6. Such a control device 6 is also designated as a central module. The brake actuators 8 preferably each include a brake cylinder (not shown).

[0084] The control device 6 is configured to actuate the axle modulator 25 as a function of the signal from the braking value transmitter, so that the axle modulator 25 in particular regulates the brake cylinder pressure on both sides of the rear axle 17.

[0085] The brake system 1 also includes a sensor unit 5 and wheel rotational speed sensors 7, which are connected to the control device 6.

[0086] The pneumatic suspension 3 is electronically regulated and includes a displacement sensor 4, with which a current level of the axle 17 and changes in the level can be detected. The displacement sensor 4 preferably has a signal connection to the brake system 1, preferably the control device 6. The control device 6 preferably continuously evaluates the signals from the displacement sensor 4, likewise the signals from the wheel rotational speed sensors 7.

[0087] The control device 6 additionally receives information about the activation of a brake function, preferably a parking brake function or a service brake function. The control device 6 preferably stores the current level (measured level) of the axle 17 at regular intervals or under specific conditions, specifically as long or as soon as the wheels 24 of the axle 17 are not braked. This stored measured level is designated the neutral position.

[0088] Starting from the neutral position, the brake system 1, preferably the control device 6, is configured to detect stress via the signals from the displacement sensor 4.

[0089] In the present case, the brake system 1 of the trailer 13 is equipped to dissipate the stress by using an additional function which is substantially located in the function and the software of the control device 6. This detects stressing of the trailer 13 in the manner described above. Furthermore, the brake system 1 monitors at least one state variable Z.sub.1, Z.sub.2 via the sensor unit 5, wherein the brake system 1 with the control device 6 is configured to release the brake actuators 8 as a function of the monitored state variable Z.sub.1, Z.sub.2 for the case in which stress is detected. To dissipate the stress detected by releasing the brake actuators 8, the brake system 1 and, in particular, the control device 6 carries out an actuation of a first target braking level or second target braking level via the brake actuator 8, in particular via appropriate actuation of the respective brake cylinder (not shown) or possible brake valves (not shown). As a result of this additional function of the brake system 1, it is possible to actuate the brake actuator 8 of the semi-trailer 100 as necessary in the various load states shown in FIGS. 2 and 3.

[0090] The state variable Z.sub.1 monitored by the sensor unit 5 is in particular an angle of inclination , and the state of loading characterized by the angle of inclination is a positional state of the semi-trailer 100. The sensor unit 5 includes an acceleration sensor 5.1 for monitoring the angle of inclination .

[0091] In FIG. 2, the semi-trailer 100 is on a level with an angle of inclination =0. In FIG. 3, on the other hand, the semi-trailer 100 is on a slope with an angle of inclination =10. These two positional states of the semi-trailer 100 characterized by the angle each require a coordinated minimum braking level in order to prevent the semi-trailer 100 unintendedly rolling away when the brake actuators 8 are released.

[0092] The control device 6 is additionally connected via a standardized data connection, in the present case a CAN bus system 9, to an electronic system, not shown in more detail, of the tractor 11. The function, constituent parts and interaction of the aforementioned systems are in principle known. Only the constituent parts that are significant for the understanding of the disclosure are shown in the figures.

[0093] Releasing the brake actuator 8 is only briefly envisaged. After the stress has been dissipated, the brake pressure is increased again to the originally applied value. The time interval during which the reduction in the braking exists includes approximately 0.2 to 2 seconds. The time interval can also be longer, depending on the vehicle geometry and the properties of the systems involved.

[0094] The method according to the disclosure is described below by way of example by using the load states shown in FIGS. 1 to 3, as is the performance of the method in a brake system 1 for a vehicle 100 according to the embodiment shown in FIG. 4.

[0095] In the state shown in FIG. 2, the brake system 1 (cf. FIG. 4) monitors the angle of inclination , in particular continuously, via the acceleration sensor 5.1. This angle of inclination is either compared continuously with a predefined value range of 0<+/90, in particular with a predefined value range of 0<+/12, via the control device 6, or only for the case in which a stress is detected by the displacement sensor 4. As a reaction to a detected stress, the brake actuators 8 are released by actuating a second target braking level via the control device 6, since the angle of inclination is =0 and thus lies outside the predefined value range.

[0096] In the embodiment shown in FIG. 3, the semi-trailer 100 is on a slope which is inclined by the angle =10. The brake system 1 (cf. FIG. 4) and in particular the control device 6 in this case, as a reaction to a detected stress, will release the brake actuators 8 by actuating a first target braking level by the control device 6, since the angle of inclination is =10 and thus lies within the predefined value range. The first target braking level can in particular be defined as a function of the state variable Z.sub.1, that is, the angle of inclination . The first target braking level is determined as the ratio of the necessary braking force f.sub.b()=m.Math.g.Math.sin and the weight f.sub.g(g)=m.Math.g. This results in a first target braking level of 17.4% with an angle of inclination =10. Thus, the brake actuator 8 can be released exactly by the electric brake system 1 with the control device 6 as a function of the detected state variable Z.sub.1, in the present case the angle of inclination.

[0097] Furthermore, in addition to the acceleration sensor 5.1, the sensor unit 5 can include a further sensor, in particular a pressure sensor 5.2. In this case, two load states, namely a positional state and a state of loading, are taken into account when actuating the brake actuators 8. The brake system 1 is configured to monitor a first state variable Z.sub.1, in the present case an angle of inclination , by the acceleration sensor 5.1 of the sensor unit 5 and, in addition, a second state variable Z.sub.2, for example an air suspension bellows pressure of the air suspension bellows 20 (cf. FIGS. 1 to 3), via the pressure sensor 5.2 of the sensor unit 5.

[0098] In this case, the brake system 1 is further configured to release the brake actuators 8 as a function of the first monitored state variable Z.sub.1 and of the second monitored state variable Z.sub.2 by actuating a first target braking level for the case in which the first state variable Z.sub.1, that is, the angle of inclination , can be assigned to the first predefined value range of 0<+/90, in particular of 0<+/12, and the second target braking level, that is, the air suspension bellows pressure, can be assigned to the second predefined value range of 0.1 bar<p<10 bar, actuating a second target braking level for the case in which the first state variable Z.sub.1 cannot be assigned to the second predefined value range, and actuating a third target braking level for the case in which the second state variable Z.sub.2 cannot be assigned to the second predefined value range.

[0099] The second target braking level can in particular be 2% and >0%, in particular 1% and >0%. In this case, the semi-trailer 100 is on a level.

[0100] The air suspension bellows pressure cannot be determined unambiguously in particular when loading an empty semi-trailer 100 with the trailer 13 lowered, and thus cannot be assigned to the second predefined value range. In this case, the third target braking level is actuated which, in particular, is a value corresponding to the so-called loading characteristic curve. This is a braking level which is to be applied in the case of a fully loaded semi-trailer 100.

[0101] FIG. 5 shows a further embodiment of the vehicle 100, which is a semi-trailer in the present case. It shows the vehicle floor 22 of the semi-trailer 100 with the electro-pneumatic brake system 10 in detail. The vehicle 100 shown in FIG. 5 differs from the embodiment shown in FIGS. 1 to 4 firstly by the suspension 3, which is configured as a mechanical suspension.

[0102] In a known manner the electro-pneumatic brake system 10 has an electronically controllable pneumatic brake system 1 in conjunction with a number of electronically regulated pneumatic brake actuators 8 and a compressed air supply (not shown) for the brake actuators 8, wherein at least two brake actuators 8 are assigned to the rear axle 17. The electronically controllable pneumatic brake system 1 has the control device 6, wherein the axle modulator 25 is integrated into the control device 6 in this embodiment.

[0103] The state of loading monitored in this embodiment is a state of loading, and the state variable Z.sub.3 is a spring compression travel of the mechanical suspension 3. In the mechanical suspension 3 of the vehicle 100 and the vehicle body 21, compression of the suspension of the vehicle 100 and of the vehicle body occurs in the event of a change in the weight or the distribution of the load of the vehicle 100 or the vehicle body, so that the state of loading is characterized by the spring compression travel Z.sub.3.

[0104] The brake system 1 includes a brake system 1 for dissipating stresses in the braked, stationary vehicle 100 in a known manner, which has a control device 6 with integrated axle modulator, to which, amongst other things, wheel rotational speed sensors 7 are connected for detecting a stress in the vehicle 100 produced by a level change. The brake actuator 8 can be actuated via the brake system 1. Furthermore, the brake system 1 includes a sensor unit 5 with at least one height sensor 5.3 for monitoring the spring compression travel Z.sub.3, wherein the brake actuator 8 actuates a target braking level as a function of the spring compression travel Z.sub.3.

[0105] In the sense of the disclosure, the sensor unit 5 can also have a combination of the sensors shown in FIGS. 4 and 5 and an acceleration sensor 5.1 for monitoring the first state variable Z.sub.1, a pressure sensor 5.2 for monitoring the second state variable Z.sub.2 and a height sensor 5.3 for monitoring the third state variable Z.sub.3, wherein the brake system 1 can be configured to release the brake actuator as a function of the first state variable Z.sub.1, the state variable Z.sub.2 and the third state variable Z.sub.3.

[0106] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF DESIGNATIONS (PART OF THE DESCRIPTION)

[0107] 1 Brake system [0108] 3 Suspension [0109] 4 Displacement sensor [0110] 5 Sensor unit [0111] 5.1 Acceleration sensor [0112] 5.2 Pressure sensor [0113] 5.3 Height sensor [0114] 6 Control device [0115] 7 Wheel rotational speed sensor [0116] 8 Brake actuator [0117] 9 CAN bus system [0118] 10 Electro-pneumatic brake system [0119] 11 Tractor [0120] 12 Fifth-wheel plate [0121] 13 Trailer [0122] 14 King pin [0123] 15 Front axle [0124] 16 Rear axle [0125] 17 Axle [0126] 18 Axle swinging arm [0127] 19 Bearing point [0128] 20 Air suspension bellows [0129] 21 Vehicle body [0130] 22 Vehicle floor [0131] 23 Wheels [0132] 24 Wheels [0133] 25 Axle modulator [0134] 100 Vehicle [0135] a Wheelbase [0136] b Wheelbase [0137] Angle of inclination [0138] Z.sub.1 First state variable [0139] Z.sub.2 Second state variable [0140] Z.sub.3 Third state variable