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EP-4737232-A1 - HYDRAULIC BRAKE SYSTEM FOR INDUSTRIAL VEHICLE

EP4737232A1EP 4737232 A1EP4737232 A1EP 4737232A1EP-4737232-A1

Abstract

A hydraulic brake system (10) for an industrial vehicle includes a master cylinder (12) having a brake pedal, a brake device (13), and a master cylinder fluid passage. The hydraulic brake system (10) includes a hydraulic fluid tank (12), a control valve (14, 141), an actuator (15), an actuator fluid passage, a fluid return passage, a first solenoid valve (34), a second solenoid, a third solenoid valve (75), and a controller (28). When braking is performed by the master cylinder (12), the controller controls the first solenoid valve (34) to open the master cylinder fluid passage, and the second solenoid valve (36) to close the actuator fluid passage. When braking is performed by the actuator (15), the controller (28) controls the second solenoid valve (36) to open the master cylinder fluid passage, and the second solenoid valve (36) to close the actuator fluid passage, and when the hydraulic pressure of the brake device (13) is released, the controller (28) controls the third solenoid valve (75) to open the fluid return passage.

Inventors

  • MASUDA, HIDEO

Assignees

  • KABUSHIKI KAISHA TOYOTA JIDOSHOKKI

Dates

Publication Date
20260506
Application Date
20251001

Claims (5)

  1. A hydraulic brake system (10) for an industrial vehicle, the hydraulic brake system (10) comprising: a brake device (13) configured to brake a wheel using hydraulic pressure; a master cylinder (12) having a brake pedal, and configured to discharge hydraulic fluid in accordance with a depressed amount of the brake pedal to output the hydraulic pressure; and a master cylinder fluid passage connecting the master cylinder (12) and the brake device (13), characterized in that the hydraulic brake system (10) further includes: a hydraulic fluid tank (12) in which the hydraulic fluid is stored; a control valve (14, 141) disposed in the master cylinder fluid passage; an actuator (15) that outputs the hydraulic pressure; an actuator fluid passage that extends from the actuator (15) to the master cylinder fluid passage through the control valve (14, 141); a fluid return passage allowing the hydraulic fluid to return from the brake device (13) to the hydraulic fluid tank (12); a first solenoid valve (34) provided in the control valve (14, 141), and configured to open and close the master cylinder fluid passage; a second solenoid valve (36) provided in the control valve (14, 141), and configured to open and close the actuator fluid passage; a third solenoid valve (75) configured to open and close the fluid return passage; and a controller (28) configured to control the first solenoid valve (34), the second solenoid valve (36), and the third solenoid valve (75), the hydraulic fluid tank (12) is connected to the master cylinder fluid passage and the actuator fluid passage, when braking is performed by the master cylinder (12), the controller (28) controls the first solenoid valve (34) to open the master cylinder fluid passage, and the second solenoid valve (36) to close the actuator fluid passage, when braking is performed by the actuator (15), the controller (28) controls the second solenoid valve (36) to open the actuator fluid passage, and the first solenoid valve (34) to close the master cylinder fluid passage, and when the hydraulic pressure of the brake device (13) is to be released, the controller (28) controls the third solenoid valve (75) to open the fluid return passage.
  2. The hydraulic brake system (10) for the industrial vehicle according to claim 1, further comprising: a bypass passage (97) provided in the control valve (14, 141), and bypassing the first solenoid valve (34) in the master cylinder fluid passage; and a fourth solenoid valve (76) disposed in the control valve (14, 141), and configured to be controlled by the controller (28) to open and close the bypass passage (97), characterized in that the controller (28) controls the fourth solenoid valve (76) to close the bypass passage (97) when braking is performed by the actuator (15).
  3. The hydraulic brake system (10) for the industrial vehicle according to claim 2, characterized in that the fourth solenoid valve (76) is a normally open solenoid valve.
  4. The hydraulic brake system (10) for the industrial vehicle according to claim 1 or 2, characterized in that the first solenoid valve (34) has a first valve hole (44), and a first valve element (52) that opens and closes the first valve hole (44), the second solenoid valve (36) has a second valve hole (64), and a second valve element (72) that opens and closes the second valve hole (64), the third solenoid valve (75) has a third valve hole (88), and a third valve element (95) that opens and closes the third valve hole (88); a diameter of each of the first valve hole (44) and the second valve hole (64) is larger than a diameter of the third valve hole (88).
  5. The hydraulic brake system (10) for the industrial vehicle according to claim 4, characterized in that the diameter of each of the first valve hole (44) and the second valve hole (64) is 1.5 to 90 times the diameter of the third valve hole (88).

Description

BACKGROUND ART The present invention relates to a hydraulic brake system for an industrial vehicle. As a conventional technique relating to a hydraulic brake system for an industrial vehicle, for example, a brake fluid pressure control device disclosed in Japanese Patent Application Publication No. 2000-085560 has been known. The brake fluid pressure control device disclosed in the Publication includes a control piston that receives fluid pressure generated by a master cylinder, and a control valve that controls fluid pressure of a fluid pressure source with respect to the fluid pressure acting on the control piston, and a brake device that operates with the fluid pressure controlled by the control valve. The hydraulic brake system as disclosed in the Publication is known. In order to enable automated operation without an operator in an industrial vehicle configured to be capable of manual operation, it is necessary to provide a means for automatedly generating braking force in a brake device that is configured to generate braking force through brake pedal operation. That is, in an industrial vehicle configured to switch between the manual operation and the automated operation, it is necessary to implement a hydraulic brake system that can apply braking force to the brake device both by operating the brake pedal operation and by automatedly controlling an actuator. In this case, for example, it is considered that the actuator, which is an automatedly controlled, is configured to press the brake pedal during automated operation, but the actuator would interfere with brake pedal operation during the manual operation. In addition, it is difficult to adjust the braking force of the brake device when the actuator operates the brake pedal. The present invention, which has been made in view of the above problems, is directed to providing a hydraulic brake system for an industrial vehicle that can properly operate a brake device even if operation of the industrial vehicle is switched between manual operation and automated operation. The present invention is also directed to providing the hydraulic brake system for the industrial vehicle that achieves both improvement in responsiveness of the brake device and downsizing of a control valve. SUMMARY In accordance with an aspect of the present invention, there is provided a hydraulic brake system for an industrial vehicle. The hydraulic brake system include a master cylinder having a brake pedal, and configured to discharge hydraulic fluid in accordance with a depressed amount of the brake pedal; a brake device configured to brake a wheel using hydraulic pressure; and a master cylinder fluid passage connecting the master cylinder and the brake device. The hydraulic brake system includes: a hydraulic fluid tank in which the hydraulic fluid is stored; a control valve disposed in the master cylinder fluid passage; an actuator that outputs hydraulic pressure; an actuator fluid passage that extends from the actuator to the master cylinder fluid passage through the control valve; a fluid return passage allowing the hydraulic fluid to return from the brake device to the hydraulic fluid tank; a first solenoid valve provided in the control valve and configured to open and close the master cylinder fluid passage; a second solenoid valve provided in the control valve, and configured to open and close the actuator fluid passage; a third solenoid valve configured to open and close the fluid return passage; and a controller configured to control the first solenoid valve, the second solenoid valve, and the third solenoid valve. The hydraulic fluid tank is connected to the master cylinder fluid passage and the actuator fluid passage. When braking is performed by the master cylinder, the controller controls the first solenoid valve to open the master cylinder fluid passage, and the second solenoid valve to close the actuator fluid passage. When braking is performed by the actuator, the controller controls the second solenoid valve to open the master cylinder fluid passage, and the second solenoid valve to close the actuator fluid passage. When the hydraulic pressure of the brake device is released, the controller controls the third solenoid valve to open the fluid return passage. Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the embodiments together with the accompanying drawings in which: FIG. 1 is a schematic configuration view of a hydraulic brake system for a forklift truck according to an embodiment of the present invention;FIG. 2A is a schematic view of a first solenoid valve, and FIG. 2B is a schematic view of a second solenoid valve;FIG. 3A is a schem