CN115489497A

CN115489497A - Brake system for agricultural vehicle

Info

Publication number: CN115489497A
Application number: CN202210679663.5A
Authority: CN
Inventors: 威杰亚库马尔·戈文丹
Original assignee: ZF CV Systems Global GmbH
Current assignee: ZF CV Systems Global GmbH
Priority date: 2021-06-18
Filing date: 2022-06-16
Publication date: 2022-12-20

Abstract

The invention relates to a braking system (4) for an agricultural vehicle (1), the braking system (4) comprising: a driver actuated control system; an automatic control system (5); a brake circuit (10) having brake lines (33 a, 33 b) for actuating wheel brakes (35 a, 35 b), and a control device (18 a, 18 b) comprising an output piston to regulate brake pressure in at least one of the brake lines (33 a, 33 b), wherein the output piston is controlled by two control systems, and wherein the brake lines (33 a, 33 b) are supplied by the control device (18 a, 18 b) with the maximum of the brake force provided by the automatic control system (5) and the brake force provided by the driver-actuated control system.

Description

Brake system for agricultural vehicle

Technical Field

The present invention relates to a braking system for an agricultural vehicle, in particular a tractor.

Background

Agricultural vehicles such as tractors typically have a hydraulic brake system, in particular with a brake pedal, a master cylinder for multiplying and transmitting the driver's force and a slave cylinder for applying a braking force to the wheel brakes. The split braking system includes brake pedals for left and right wheel braking independently. Thus, the left and right wheels of the rear axle of the agricultural tractor can be braked independently.

Furthermore, automatic braking systems and driver assistance systems for automatic or autonomous braking are known, in particular with an ECU for electronically controlling each brake line. The hydraulic pressure of the automated system may be provided by an air over head fluid (AoH) converter that converts air pressure into a proportional amount of hydraulic pressure.

In vehicles with automatic braking, driver-actuated braking and automatic braking must be combined. Those combinations may be achieved by valve devices including a two-way shuttle valve and/or a 3/2 valve. Therefore, known hydraulic braking systems for agricultural vehicles typically include complex designs for independently controlling and actuating the wheel brakes through driver action and autonomous braking. However, complex valve arrangements increase cost and may result in delays in signal transmission.

Disclosure of Invention

It is an object of the present invention to provide a brake system for an agricultural vehicle and an agricultural vehicle comprising such a brake system, which enable autonomous braking functions and brake driver actions in a compact system.

This object is achieved by a braking system according to claim 1. Furthermore, an agricultural vehicle comprising such a braking system is provided. The dependent claims describe preferred embodiments.

The inventive brake system thus comprises a driver-actuated control system and an automatic control system, both control systems being provided for controlling the hydraulic and/or pneumatic brake circuit, wherein the higher braking intention of both control systems actuates the hydraulic or pneumatic brake circuit. This selection of the maximum braking intention is achieved by the control means comprising a common output piston to be controlled or actuated by both control systems, i.e. the driver actuated control system and the automatic control system. Thus, in particular both control systems exert a force or pressure on the common output piston, and the higher force or pressure defines the braking force.

The provision of control devices, in particular control cylinders, with a common output piston makes possible a reliable and relatively simple combination or combination of driver-actuated and automatic control systems. The combination of the two control systems can be achieved without the need for a two-way shuttle valve or other complex valving apparatus, which typically results in higher cost and may result in delays in signal transmission.

According to a preferred embodiment, a hydraulic split brake system for independently controlling a left wheel brake and a right wheel brake is provided.

The braking system of the present invention provides a compact, space-saving and reliable construction for each brake circuit.

Preferably, two brake pedals are provided to enable individual braking of either of the wheel brakes, e.g. the left and right rear wheels.

According to an advantageous embodiment, the automatic control system is realized as a hydraulic control system, wherein the control device comprises a hydraulic input chamber for receiving a hydraulic signal from the hydraulic control system. Thus, the output piston receives hydraulic pressure from the automatic control system and preferably mechanical force from the driver actuated control system. This combination enables a reliable integration or combination of driver-actuated control systems and automatic control systems, wherein the driver-actuated control system outputs a mechanical force, in particular from the brake pedal, to the output piston via further mechanical measures, and the automatic hydraulic control system applies a hydraulic pressure to the output piston. These two control inputs do not interact, thus facilitating the merging of the two control systems.

According to another embodiment, the automatic control system is only realized as a pneumatic control system if the air pressure is sufficient to meet the pressure of the output piston, wherein the control device comprises a pneumatic input chamber to receive a pneumatic signal from the pneumatic control system. Thus, the output piston receives a pneumatic pressure from an automatic control system and preferably a mechanical force from a driver actuated control system. This combination enables a reliable merging or combination of a driver-actuated control system and an automatic control system, wherein the driver-actuated control system outputs a mechanical force, in particular from a brake pedal, via further mechanical measures to an output piston, and the automatic pneumatic control system applies a pneumatic pressure onto the output piston. These two control inputs do not interact, thus facilitating the merging of the two control systems.

According to the invention, the driver is always able to brake the tractor by brake pedal actuation if there is any lack or failure of automatic braking or if there is insufficient automatic braking action. Such driver braking may also be performed during an automatic braking phase; thus, automatic braking may be overruled by the driver.

The output piston in turn acts on a hydraulic or pneumatic output chamber which is part of a hydraulic or pneumatic brake circuit. Thus, the automatic hydraulic or pneumatic control system for applying a control pressure to the common output piston and the hydraulic or pneumatic brake circuit for actuating the wheel brakes are preferably separated by the output piston and do not interfere.

According to a preferred embodiment, the automatic hydraulic control system is realized as an autonomous (automatic) pneumatic hydraulic control system, preferably with a pneumatic hydraulic converter for each brake line. Thus, a common air reservoir for all brake lines may be provided and connected to the pneumatic fluid converter of each brake line via an electropneumatic control valve, in particular a PWM valve. The PWM valves of the individual brake lines are preferably controlled by a common Electronic Control Unit (ECU). The provision of a pneumatic-hydraulic converter facilitates automatic control, since the brake pressure can first be regulated by the electropneumatic valve, in particular by the electrical signal output by the ECU, and the simulated pneumatic pressure can then be converted into a simulated hydraulic brake pressure, i.e. a hydraulic brake signal, which is input into the hydraulic input chamber of the control device.

Thus, the configuration of the present invention enables reliable and safe control of the hydraulic brake pressure at relatively low cost and with a compact design.

Furthermore, according to the invention, the hydraulic oil will be returned to its source line after the brake is applied. During brake actuation, the volumes of the hydraulic input chamber and the hydraulic output chamber change, thereby enabling oil return or pressure compensation of each hydraulic circuit.

According to another embodiment, the automated pneumatic control system is implemented as an autonomous (automatic) pneumatic control system. Thus, a common air reservoir for all brake lines may be provided and connected to each brake line via an electropneumatic control valve, in particular a PWM valve. The PWM valves of the individual brake lines are preferably controlled by a common Electronic Control Unit (ECU). Thus, the brake pressure may be regulated by an electro-pneumatic valve, in particular by an electrical signal output by the ECU.

The control device is preferably configured as a control cylinder accommodating the common output piston. The brake pedal may be connected or linked to an input piston slidably disposed in a control cylinder. Thus, both the input piston and the output piston are guided in the control cylinder.

According to a preferred embodiment, the input piston is attached to or comprises a plunger, which extends through the hydraulic or pneumatic input chamber. This configuration enables the provision of a hydraulic or pneumatic input chamber and mechanical control by the input piston actuated via the driver.

The plunger preferably traverses a hydraulic or pneumatic input chamber from the input piston to the output piston. Thus, the plunger may abut against the inner face of the output piston; further, the plunger may be received in a recess provided in an inner face of the output piston. During an automatic braking action based on hydraulic or pneumatic pressure, the plunger can be disengaged from the input face of the output piston, preferably guided in a recess of the output piston. These features contribute to a compact and reliable design at low cost.

A further advantage of the system of the present invention is the benefit of the tactile driver feel. During automatic brake application, the pedal position may be controlled by the driver within its application range or actuation range. If the automatic control system initiates an automatic (autonomous) braking action by increasing the oil or air pressure in the hydraulic or pneumatic input chamber, the output piston is pushed or displaced within the control cylinder. During automatic braking, the driver may feel this displacement of the output piston via the brake pedal and the mechanical linkage or connection to the output piston. Thus, the driver receives a braking feel or tactile feedback of all braking actions, i.e. driver braking action and automatic braking action. The driver can always initiate driver braking by applying a higher braking force via his brake pedal and input piston in order to push the output piston with a higher braking force.

Drawings

The invention is described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 illustrates an agricultural tractor having a braking system according to an embodiment of the present invention;

FIG. 2a depicts the relevant components of the hydraulic brake system in more detail;

FIG. 2b depicts in more detail only the relevant components of the pneumatic brake system;

FIG. 3 shows the relevant components of FIG. 2a in more detail; and

fig. 4 shows a control device with a driver actuated control member.

Detailed Description

Fig. 1 shows an agricultural tractor 1, the agricultural tractor 1 comprising: a steered front axle 2 having left and right

front wheels

2a, 2b; a rear axle 3 having left and right

rear wheels

3a, 3b; and a hydraulic brake system 4. The hydraulic brake system 4 includes: an automatic pneumatic hydraulic control system 5h with an Electronic Control Unit (ECU) 6; a driver actuated control system 8; and a hydraulic brake circuit 10. The automatic pneumatic-hydraulic control system 5h may be controlled by the ECU 6 based on, for example, a driver assist system and/or an EBS (electronic brake system), and by a steering control system based on a global positioning system.

The brake system 4 is divided to facilitate independent braking actions of the left rear brake 35a for braking the left rear wheel 3a and the right rear brake 35b for braking the right rear wheel 3b. Thus, in the figures, the left and right braking measures are identified by corresponding reference numerals with the letters a, b for the left and right braking systems. Fig. 2a to 4 depict embodiments of the same relevant components in both brake lines, without the additional reference letters a and b.

Thus, the automatic control system 5h includes: a reservoir 12 containing pressurized air; the left electropneumatic control valve 13a; and a right electro-pneumatic control valve 13b. The two

electropneumatic control valves

13a, 13b are preferably PWM valves (pulse width modulation valves) controlled by a left electronically controlled PWM signal S1 and a right electronically controlled PWM signal S2, both S1 and S2 being output by the ECU 6. The

control valves

13a, 13b transmit left and right pneumatic control signals P1 and P2 to left and right AoH (gas cap liquid)

converters

15a and 15b, respectively. The

AoH converters

15a, 15b convert the pneumatic control signals P1, P2 into left and right hydraulic control signals H1, H2; then, the hydraulic control signals H1, H2 are supplied to the left control device 18a and the right control device 18b, respectively.

The

control devices

18a, 18b are realized as control cylinders or master cylinders, as explained with respect to fig. 2 and 4; the control means 18a, 18b are provided for combining or merging the automatic control by the hydraulic signals H1, H2 (hydraulic signal H in fig. 2 to 4) and the driver actuated control via the

brake pedals

20a, 20 b.

Fig. 2a to 4 depict the left-hand or right-hand components of the brake system 4 in more detail with respect to a general view, wherein the reference numerals 13 to 22 correspond to the

elements

13a, 13b to 22a, 22b of fig. 1.

The driver actuates the

brake pedal

20a, 20b, which

brake pedal

20a, 20b corresponds to the brake pedal 20 in fig. 2a, 2b and 4. In fig. 2a and 2b, the brake pedal 20 actuates the input piston 22; the mechanical linkage from the brake pedal 20 to the input piston 22 can be realized by a rigid or coupling joint.

In fig. 2a and 3, the PWM valve 13 is connected with its input port 113 to the air reservoir 12 and outputs analog (non-digital) pneumatic signals P1, P2 to the pneumatic input 115 of the AoH converter 15, the AoH converter 15 converts the pneumatic signals P1, P2 into similar hydraulic signals H1, H2, which are then transmitted via hydraulic connecting lines to the hydraulic input port 25 of the hydraulic input chamber 26H in the

control device

18a, 18b. The hydraulic input chamber 26h applies hydraulic pressure to the input surface 118 of the output piston 28.

In fig. 2b, the PWM valve 13 is connected at its input port 113 to the air reservoir 12 and outputs analog (non-digital) pneumatic signals P1, P2 directly to the pneumatic input port 25 of the pneumatic input chamber 26P in the

control device

18a, 18b. The pneumatic input chamber 26p applies pneumatic pressure to the input surface 118 of the output piston 28.

Furthermore, the input piston 22 has attached to it or comprises a plunger 27, which plunger 27 extends through a hydraulic 26h or pneumatic 26p input chamber. The plunger 27 preferably traverses the

input chambers

26h, 26p from the input piston 22 to the input surface 118 of the output piston 28. Thus, the hydraulic pressure 26h or pneumatic pressure 26p input chamber and plunger 27 both act independently on the output piston 28. This configuration facilitates the combination of hydraulic or pneumatic signals to the chamber via hydraulic 26h or pneumatic 26p and the mechanical signals of the driver actuated input piston 22.

Thus, the plunger 27 abuts against the input face 118 of the output piston 28; preferably, the plunger 27 is received in a recess provided in the input face 118 of the output piston 28. If the driver actuates the left or

right brake pedal

20a, 20b, the respective input piston 22a, 22b is pushed, thereby pushing the output piston 28 through its plunger 27.

In fig. 1, if the ECU 6 decides to actuate the left wheel rear brake 35a, the ECU 6 outputs a left electric PWM signal S1 to the left PWM valve 13a, the left PWM valve 13a transmits pressurized air from the air tank 12 as a pseudo left pneumatic signal P1 to the AoH converter 15a via the pneumatic connection line, the AoH converter 15a outputs a corresponding pseudo hydraulic pressure control signal P1, and thereby oil (hydraulic fluid) is supplied to the hydraulic pressure input chamber 26 h. The hydraulic input chamber 26h acts on the input surface 118 of the left control device 18 a.

Thus, during an automatic braking action based on the hydraulic pressure, the plunger 27 can be separated from the output piston 28, preferably guided in a recess. However, the driver receives a braking sensation from the autobrake action because the driver can actuate the brake pedal 20 until the plunger 27 contacts the output piston 28, which contact can be perceived by the driver as a resistance. Furthermore, the driver can always overrule the automatic braking by a stronger braking action. This override may be achieved without switching any valve configuration, which includes different valve positions for automatic braking and driver braking and therefore requires a switching operation.

The output piston 28 acts on a hydraulic output chamber 32, the hydraulic output chamber 32 having an

output port

19, 19a, 19b, the

output port

19, 19a, 19b being connected to a hydraulic brake line 33 for actuating a

brake

35a or 35b. Thus, in fig. 1, the control cylinder 18a is used to actuate the left wheel brake 35a via the left hydraulic output chamber 32a and the left hydraulic brake line 33a, and correspondingly, the control cylinder 18b is used to actuate the right wheel brake 35b via the right hydraulic output chamber 32b and the right hydraulic brake line 33 b. The hydraulic output chambers 32a, 32b include supply ports 21a, 21b, respectively, which supply ports 21a, 21b may be fed by a common oil reservoir 38.

Thus, the

control devices

18a, 18b function to select a higher logic unit to output the maximum value of the hydraulic output pressure of the automatic pneumatic-hydraulic control system 5h and the driver-actuated mechanical braking force.

Thus, the hydraulic actuation circuit 10, including the hydraulic output chambers 32a, 32b, the

hydraulic brake lines

33a, 33b, the common reservoir 38, the brake system 4, is separate from the hydraulic control system acting on the input pistons 22a, 22b.

Furthermore, the hydraulic actuation circuit 10 enables pressure compensation between the left and right hydraulic output chambers 32a, 32b. The left and right

rear wheel brakes

35a, 35b are actuated by receiving hydraulic pressure via the

brake lines

33a, 33 b; when the

wheel brakes

35a, 35b are released, they supply oil back to their respective hydraulic output chambers 32a, 32b via the

brake lines

33a, 33b (hydraulic return).

List of reference numerals

1. Farm tractor

2. Front axle

2a left front wheel

2b front right wheel

3. Rear axle

3a left rear wheel

3b right rear wheel

4. Brake system

5. Automatic control system

5h automatic pneumatic hydraulic control system

5p automatic pneumatic control system

6. Electronic control unit, ECU

8. Driver actuated control system

10. Hydraulic actuating circuit

12. Gas storage tank

13. Electro-hydraulic control valve and PWM valve

13a left electrohydraulic control valve, left PWM valve

13b Right electro-hydraulic control valve, right PWM valve

15a left gas-cap liquid converter

15b right gas-cap liquid converter

16a left oil storage tank (Hydraulic storage tank)

16b Right oil storage tank (Hydraulic storage tank)

18a, 18b control device

19. 19a, 19b hydraulic output port

20. 20a, 20b brake pedal

21. Supply port

22. Input piston

25. Hydraulic input port

26. Input chamber

26h hydraulic input chamber

26p pneumatic input chamber

27. Plunger piston

28. Output piston

32. Hydraulic output chamber

33. 33a, 33b hydraulic brake line

35a, 35b rear wheel brake

38. Public oil storage tank

113 Input port of PWM valve 13

115. Pneumatic input

213 Output port of PWM valve 13

S electric control signal

51. Left electric control signal

52. Right electric control signal

P pneumatic control signal

P1 left pneumatic control signal

P2 Right pneumatic control Signal

H hydraulic control signal

H1 Left hydraulic control signal

H2 A right hydraulic control signal.

Claims

1. A braking system (4) for an agricultural vehicle (1), the braking system (4) comprising:

a driver actuated control system (8),

an automatic control system (5),

a fluid brake circuit (10), the fluid brake circuit (10) having a brake line (33, 33a, 33 b) for actuating a wheel brake (35 a, 35 b), and

a control device (18 a, 18 b), the control device (18 a, 18 b) comprising an output piston (28) to regulate a brake pressure in at least one of the brake lines (33, 33a, 33 b),

wherein both the driver actuated control system (8) and the automatic control system (5) control the output piston (28), and

wherein the control device (18 a, 18 b) supplies the brake line (33) with the maximum of the braking force provided by the automatic control system (5) and the braking force provided by the driver-actuated control system (8).

2. Braking system (4) according to claim 1, wherein the braking system (4) is a split braking system comprising

-a left brake pedal (20 a), a left control device (18 a), a left brake line (33 a) and a left wheel brake (35 a), and

-a right brake pedal (20 b), a right control device (18 b), a right brake line (33 b) and a right wheel brake (35 b),

wherein the left brake line (33 a) and the right brake line (33 b) are independently controlled by the driver-actuated control system (8) and the automatic control system (5), respectively, and

wherein the automatic control system (5) comprises a fluid input chamber (26 h, 26 p).

3. The braking system (4) according to claim 2,

the automatic control system (5) is realized as a hydraulic control system (5 h),

the fluid input chamber is a hydraulic input chamber (26H) for receiving a hydraulic signal (H, H1, H2) from the hydraulic control system (5H), and the output piston (28) is charged with a hydraulic pressure of the hydraulic input chamber (26H).

4. The braking system (4) according to claim 3,

wherein the output piston (28) applies a brake pressure to a hydraulic output chamber (32) in the control device (18 a, 18 b),

wherein the hydraulic output chamber (32) of each brake line is connected to a common oil reservoir (38), thereby providing a return flow of brake oil in the brake lines (33, 33a, 33 b).

5. The braking system (4) according to claim 4,

wherein the hydraulic output chamber (32) of each brake line is connected to a common reservoir (38), thereby providing a return flow of brake oil in the brake lines (33, 33a, 33 b).

6. Braking system (4) according to one of claims 3 to 5,

the automatic control system (5) is a pneumatic hydraulic control system (5 h), the pneumatic hydraulic control system (5 h) comprises a pneumatic-hydraulic converter (15) having a pneumatic input (115), the pneumatic input (115) is controlled by an electropneumatic control valve (13),

the electropneumatic control valve (13) transmits pneumatic signals (P, P1, P2) according to electrical control signals (S, S1, S2), and the gas-over-liquid converter (15) converts the pneumatic signals (P, P1, P2) into corresponding hydraulic control signals (H, H1, H2).

7. The braking system (4) of claim 6,

the electric control signals (S, S1, S2) are PWM signals,

wherein an ECU (6) is provided for outputting the electrical control signals (S, S1, S2) to the electropneumatic control valves (13, 13a, 13 b) of each brake line (33 a, 33 b), respectively.

8. The braking system (4) according to claim 7,

the electric control signals (S, S1, S2) are PWM signals,

9. The braking system (4) according to claim 2,

the automatic control system (5) is realized as a pneumatic control system (5 p),

the fluid input chamber is a pneumatic input chamber (26P) for receiving a pneumatic signal ((P, P1, P2) from the pneumatic control system (5P), and

the output piston (28) is charged with the pneumatic pressure of the pneumatic input chamber (26 p).

10. Braking system (4) according to one of claims 2 to 9, wherein the braking is performed by

-a mechanical force provided by a driver actuated braking device (20), and

-fluid pressure of the fluid input chamber (26 h, 26 p)

To control the output piston (28).

11. The braking system (4) of claim 10,

the control device (18 a, 18 b) comprising a control cylinder housing the output piston (28) and an input piston (22), and the input piston (22) being mechanically connected to the driver actuated brake device (20),

wherein the input piston (22) is provided for pushing the output piston (28).

12. The braking system (4) of claim 11,

the input piston (22) being connected to a plunger (27), the plunger (27) having a smaller cross-section than the input piston (22),

the plunger (27) extending through the fluid input chamber (26 h, 26 p) and pushing the output piston (28),

wherein the plunger (27) is separable from the output piston (28) in the case of automatic braking control via the fluid pressure in the fluid input chamber (26 p).

13. An agricultural vehicle, in particular a tractor (1), comprising:

the brake system (4) according to one of claims 2 to 12,

a steering front axle (2), and

a rear axle (3), the rear axle (3) having a left rear wheel (3 a) and a right rear wheel (3 b),

the wheel brakes (35 a, 35 b) are provided at the left rear wheel (3 a) and the right rear wheel (3 b),

the left rear wheel brake (35 a) is hydraulically controlled by a left brake line (33 a) of the brake system (4), and

the right rear wheel brake (35 b) is hydraulically controlled by a right brake line (33 b) of the brake system (4).