Brake control system for a vehicle

Abstract

Brake control system for a vehicle, wherein the brake control system (10) comprises steerable front wheels (17, 18), a left and a right rear wheel (13, 15), a left brake unit (12) for braking the left rear wheel (13), a right brake unit (14) for braking the right rear wheel (15), and a single hand-operated brake input device (16), wherein the brake control system (10) further comprises a master brake valve (20) with an inlet port (22), a return port (24), an outlet (26), and a control slide (28) for controlling the communication between the inlet port (22), the return port (24), and the outlet (26); a connection (30) that operatively connects the control slide (28) to the brake input device (16); a solenoid-controlled, open-position left-hand reversing valve (40) for controlling communication between the outlet (26) and the left brake unit (12);a solenoid-controlled, normally open right-turn valve (50) for controlling communication between the outlet (26) and the right brake unit (16); a solenoid-controlled, normally open compensating valve (60) for controlling communication between the left and right brake units (12, 14); and a pedal position sensor (70) for sensing the position of the brake input device (16), characterized in that the brake control system further comprises a rotary angle sensor (72); a vehicle speed sensor (80); and an electronic control unit (82) connected to the pedal position sensor (70), the rotary angle sensor (72), and the vehicle speed sensor (80), wherein the electronic control unit (82) controls the left- and right-turn valves (40, 50) and the compensating valve (60) as a function of signals from the pedal position sensor (70), rotary angle sensor (72), and vehicle speed sensor (80).

Description

[0001] The present invention relates to a brake control system for a vehicle comprising steerable front wheels, a left and a right rear wheel, a left brake unit for braking the left rear wheel, a right brake unit for braking the right rear wheel, and a single hand-operated brake input device. The brake control system further comprises a master brake valve with an inlet port, a return port, an outlet, and a control valve for controlling the communication between the inlet port, the return port, and the outlet. A connection is also provided that operationally links the control valve to the brake input device, as well as a solenoid-controlled, normally open, left-hand reversing valve for controlling the communication between the outlet and the left brake unit, and a solenoid-controlled, normally open, right-hand reversing valve for controlling the communication between the outlet and the right brake unit.A pedal position sensor is used to sense the position of the brake input device. In addition, the brake control system includes a rotary angle sensor, a vehicle speed sensor, and an electronic control unit connected to the pedal position sensor, rotary angle sensor, and vehicle speed sensor. The electronic control unit controls the left and right reversing valves based on signals from the pedal position sensor, rotary angle sensor, and vehicle speed sensor.

[0002] Such a brake control system, in the form of a braking system for reducing the turning radius of an automobile, is described in CN 101941427 A. In this system, wheel brake devices assigned to the driven rear wheels can be individually actuated via associated solenoid valves at the command of a control unit. This is achieved by applying a higher braking force to the inner wheel brake device compared to the outer wheel brake device when driving through a tight turn. Information from a speed sensor, a wheel steering angle sensor, and a brake pressure sensor is incorporated into this process.

[0003] Certain braking systems on agricultural tractors feature separate brake pedals for the left and right sides, allowing the brakes to assist in turning the tractor when operating off-road at low speeds. When such a tractor is operated at higher speeds on the road, the brake pedals must be manually locked together to ensure balanced braking pressure on the left and right sides. If an operator forgets to lock the pedals, they may lose control of the tractor and implement when braking at higher speeds on the road, as the tractor will pull to the side with the highest braking pressure. A single brake pedal can be used to achieve equal braking pressure on both sides.However, using a single brake pedal prevents differential braking during tight, low-speed turns on headlands. A single-pedal braking system is desirable for an agricultural tractor, providing differential braking at lower speeds in the field and disabling differential braking at transport speeds.

[0004] This and other objectives are achieved by the present invention, which provides a brake control system for a vehicle. The brake control system comprises steerable front wheels, a left and a right rear wheel, a left brake unit for braking the left rear wheel, a right brake unit for braking the right rear wheel, and a single, hand-operated brake input device. The brake control system further comprises a master brake valve with an inlet port, a return port, an outlet, and a control spool for controlling the communication between the inlet port, the return port, and the outlet; a connection that operatively links the control spool to the brake input device; and a solenoid-operated, normally open, reverse-turn valve for controlling the communication between the outlet and the left brake unit.a solenoid-controlled, normally open right-turn valve for controlling communication between the outlet and the right brake unit; a solenoid-controlled, normally open compensating valve for controlling communication between the left and right brake units; a pedal position sensor for sensing the position of the brake input device; a rotary angle sensor; a vehicle speed sensor; and an electronic control unit connected to the pedal position sensor, the rotary angle sensor, and the vehicle speed sensor, wherein the electronic control unit controls the left- and right-turn valves and the compensating valve as a function of signals from the pedal position sensor, the rotary angle sensor, and the vehicle speed sensor.

[0005] The single figure is a schematic representation of an embodiment of a vehicle braking system of the invention.

[0006] With reference to the single figure, a brake control system 10 for a vehicle, in particular an agricultural tractor (not shown), is shown, comprising a left rear brake unit 12 that brakes a left rear wheel 13, and a right rear brake unit 14 that brakes a right rear wheel 15. The vehicle also includes a steerable left and right front wheel 17 and 19, respectively. The brake control system 10 includes a single, hand-operated brake input device 16, such as a conventional brake pedal. The brake control system 10 also includes a master brake valve 20, which has a supply port 22 connected to a pressure source 23, a return port 24 connected to a reservoir 25, an outlet 26, and a control slide 28 for controlling the communication between the supply port 22, the return port 24, and the outlet 26.A conventional connection 30 operatively couples the control valve 28 to the brake input device 16. The master brake valve 20 also includes a pilot valve 32 and a spring 34, both of which operate in the opposite direction to the brake input device 16. The pilot valve 32 communicates with the outlet 26.

[0007] The brake control system 10 also includes a solenoid-controlled, normally open, left-hand reversing valve 40 for controlling communication between the outlet 26 and the left brake unit 12. Left-hand reversing valve 40 comprises an inlet 42 communicating with the outlet 26 and the pilot valve 32, and an outlet 44 connected to the left brake unit 12. A spring 46 pushes left-hand reversing valve 40 into its closed position, and solenoid 48 can be actuated to move left-hand reversing valve 40 into an open position. The brake control system 10 also includes a solenoid-controlled, normally open, right-hand reversing valve 50 for controlling communication between the outlet 26 and the right brake unit 14. Right-hand reversing valve 50 comprises an inlet 52 communicating with the outlet 26 and the pilot valve 32, and an outlet 54 connected to the right brake unit 14.A spring 56 pushes the right-hand reversing valve 50 into its closed position, and solenoid 58 can be actuated to move the right-hand reversing valve 50 into an open position.

[0008] The brake control system 10 also includes a solenoid-controlled, normally open compensating valve 60 for controlling communication between the left brake unit 12 and the right brake unit 14. The compensating valve 60 has an opening 62 for communication with the left brake unit 12 and an opening 64 for communication with the right brake unit 14. A spring 66 pushes the compensating valve 60 into its open position, and the solenoid 68 can be actuated to move the compensating valve 60 into a closed position.

[0009] The brake control system 10 also includes a pedal position sensor 70, which senses the position of the brake input device 16. The brake control system 10 also includes a rotation angle sensor 72, which senses the rotation angle of the left and right front wheels 17 and 19, respectively, which are mounted on the front axle 78. The rotation angle sensor 72 can generate a degree signal of 0 when the left and right front wheels 17 and 19, respectively, are pointing straight forward, a degree signal of + when the left and right front wheels 17 and 19, respectively, are turned to the left, and a degree signal of - when the left and right front wheels 17 and 19, respectively, are turned to the right. The brake control system 10 also includes a vehicle speed sensor 80, which senses the vehicle's speed.

[0010] An electronic control unit (ECU) 82 receives a brake pedal position signal from pedal position sensor 70, a rotation angle signal from rotation angle sensor 72, and a speed signal from vehicle speed sensor 80. The ECU 82 is connected to solenoids 32, 48, 58, and 68 of valves 20, 40, 50, and 60, respectively. The ECU 82 controls the left and right reversing valves 40 and 50, respectively, as well as the compensating valve 60, based on signals from brake position sensor 70, rotation angle sensor 72, and vehicle speed sensor 80.

[0011] The ECU 82 can energize solenoid 68 of the compensating valve 60 to close the compensating valve 60, and energize solenoid 48 of the right-turn valve 50 to close the right-turn valve 50 when the vehicle speed is below a threshold (such as 15 km / h), the signal from the yaw angle sensor 72 is below a right-turn threshold, and the pedal position sensor 70 indicates that the brake input device 16 is depressed. As a result, pressure is applied only to the right rear brake unit 14, which assists in executing a right turn.

[0012] The ECU 82 can energize solenoid 68 of the compensating valve 60 to close the compensating valve 60 and energize solenoid 58 of the left-turn valve 40 to close the left-turn valve 40 when the vehicle speed is below a threshold (such as 15 km / h), the signal from the yaw angle sensor 72 is above a left-turn threshold, and the pedal position sensor 70 indicates that the brake input device 16 is depressed. As a result, pressure is applied only to the left rear brake unit 12, thus assisting a left turn.

[0013] If none of the above conditions occur, then the ECU 82 de-energizes the solenoid 68 of the balancing valve 60 to open the balancing valve 60, de-energizes the solenoid 48 of the left-turn valve 40 to open the left-turn valve 40, and de-energizes the solenoid 58 of the right-turn valve 50 to open the left-turn valve 50. In other words, the ECU 82 opens the balancing valve 60 and opens the left- and right-turn valves 40 and 50, respectively, if the vehicle speed is not below a speed threshold, the vehicle is not making a turn, or the brake input device 16 is not actuated.

[0014] Thus, in this brake control system, a simple brake control valve normally provides a common hydraulic pressure for the right and left brake units on the rear axle. When the vehicle is traveling at headland speeds, typically less than 15 km / h, and the operator turns the front wheels to either full right or left steering lock (measured by the steering angle sensor), the normally open compensating valve and the associated right or left turning valve are energized and closed. In this configuration, the operator can apply brake pressure to only one side of the rear axle for easier headland turns. The compensating valve provides redundancy in the event that one of the right or left turning valves becomes stuck in the blocked position. The normally open compensating valve eliminates differential braking when braking on the road at higher speeds.

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