US-20260125254-A1 - HYDRAULIC BRAKE SYSTEM FOR INDUSTRIAL VEHICLE

US20260125254A1US 20260125254 A1US20260125254 A1US 20260125254A1US-20260125254-A1

Abstract

A hydraulic brake system for an industrial vehicle includes a master cylinder having a brake pedal, a brake device, and a master cylinder fluid passage. the hydraulic brake system includes a control valve disposed in the master cylinder fluid passage, an actuator, an actuator fluid passage, a first solenoid valve provided in the control valve, a second solenoid valve provided in the control valve, a controller configured to control the first solenoid valve, and the second solenoid valve. When braking is performed during manual operation, 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 during automated operation, the controller controls the second solenoid valve to open the actuator fluid passage, and the first solenoid valve to close the master cylinder fluid passage.

Inventors

Hideo Masuda

Assignees

KABUSHIKI KAISHA TOYOTA JIDOSHOKKI

Dates

Publication Date: 20260507
Application Date: 20251024
Priority Date: 20241105

Claims (10)

1 . A hydraulic brake system for an industrial vehicle, the hydraulic brake system comprising: a brake device configured to brake a wheel using hydraulic pressure; a master cylinder 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 and the brake device, wherein the hydraulic brake system includes: a control valve disposed in the master cylinder fluid passage; an actuator that outputs the hydraulic pressure; an actuator fluid passage extending from the actuator to the master cylinder fluid passage through the control valve; 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; and a controller configured to control the first solenoid valve and the second solenoid valve, when braking is performed during manual operation, 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, and when braking is performed during automated operation, the controller controls the second solenoid valve to open the actuator fluid passage, and the first solenoid valve to close the master cylinder fluid passage.
2 . The hydraulic brake system for the industrial vehicle according to claim 1 , the hydraulic brake system further comprising: a hydraulic fluid tank in which the hydraulic fluid is stored; a fluid return passage allowing the hydraulic fluid to return from the brake device to the hydraulic fluid tank via the control valve without passing through the master cylinder and the actuator; and a third solenoid valve disposed in the control valve, and configured to be controlled by the controller to open and close the fluid return passage.
3 . The hydraulic brake system for the industrial vehicle according to claim 2 , wherein the hydraulic fluid tank is connected to the master cylinder fluid passage and the actuator fluid passage.
4 . The hydraulic brake system for the industrial vehicle according to claim 1 , wherein the control valve has: a master cylinder port in the master cylinder fluid passage; and an actuator port in the actuator fluid passage, and the master cylinder port and the actuator port are formed in an upper portion of the control valve.
5 . The hydraulic brake system for the industrial vehicle according to claim 1 , the hydraulic brake system further comprising: a first fluid pressure sensor disposed between the master cylinder and the control valve in the master cylinder fluid passage, and configured to detect the hydraulic pressure in the master cylinder fluid passage; and a second fluid pressure sensor disposed between the actuator and the control valve in the actuator fluid passage, and configured to detect the hydraulic pressure in the actuator fluid passage, wherein the first fluid pressure sensor and the second fluid pressure sensor are connected to the controller.
6 . The hydraulic brake system for the industrial vehicle according to claim 1 , wherein the control valve has: a master cylinder port connected to the master cylinder; an actuator port connected to the actuator; a brake port connected to the brake device; a first passage in which the first solenoid valve is disposed, the first passage forming a part of the master cylinder fluid passage, and providing fluid communication between the master cylinder port and the brake port; a second passage in which the second solenoid valve is disposed, the second passage forming a part of the actuator fluid passage and providing fluid communication between the actuator port and the first passage; a first bypass passage bypassing the first passage; a second bypass passage bypassing the second passage; a first check valve disposed in the first bypass passage and allowing the hydraulic fluid to be supplied from the master cylinder to the brake device; and a second check valve disposed in the second bypass passage and allowing the hydraulic fluid to be supplied from the actuator to the brake device, and a valve opening pressure of each of the first check valve and the second check valve is lower than a valve opening pressure of each of the first solenoid valve and the second solenoid valve.
7 . The hydraulic brake system for the industrial vehicle according to claim 6 , wherein the valve opening pressure of each of the first check valve and the second check valve is 0.05 to 10.0% of the valve opening pressure of each of the first solenoid valve and the second solenoid valve.
8 . The hydraulic brake system for the industrial vehicle according to claim 6 , wherein the first check valve and the second check valve are arranged in the control valve so that an opening direction of each of the first check valve and the second check valve corresponds to a vertical direction.
9 . The hydraulic brake system for the industrial vehicle according to claim 1 , wherein the first solenoid valve is a normally open solenoid valve that is normally open when not energized.
10 . The hydraulic brake system for the industrial vehicle according to claim 1 , wherein a diameter of the valve hole of the first solenoid valve is set to a hole diameter generating a pressure drop that prevents the hydraulic pressure from the actuator from escaping to the master cylinder until the first solenoid valve closes, and a diameter of the valve hole of the second solenoid valve is set to a hole diameter generating a pressure drop that prevents the hydraulic pressure from the master cylinder from escaping to the actuator until the second solenoid valve closes.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2024-193806 filed on Nov. 5, 2024, the entire disclosure of which is incorporated herein by reference. BACKGROUND ART The present disclosure 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, 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 the brake pedal operation and by automated control of an actuator. In this case, for example, it is considered that the actuator, which is 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 disclosure, which has been made in view of the above problems, is directed to providing a hydraulic brake system for an industrial vehicle in which a brake device can be appropriately operated regardless of whether operation of the industrial vehicle is switched to the manual operation or the automated operation. SUMMARY In accordance with an aspect of the present disclosure, there is provided a hydraulic brake system for an industrial vehicle. The hydraulic brake system includes a master cylinder 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; a brake device configured to brake a wheel using hydraulic pressure; a master cylinder fluid passage connecting the master cylinder and the brake device. The hydraulic brake system includes: a control valve disposed in the master cylinder fluid passage; an actuator that outputs the hydraulic pressure; an actuator fluid passage that extends from the actuator to the master cylinder fluid passage through the control valve; 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 controller configured to control the first solenoid valve, and the second solenoid valve, when braking is performed during manual operation, 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, and when braking is performed during automated operation, the controller controls the second solenoid valve to open the actuator fluid passage, and the first solenoid valve to close the master cylinder fluid passage. Other aspects and advantages of the disclosure will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS The disclosure, 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 a first embodiment of the present disclosure; 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 schematic view of a first check valve, and FIG. 3B is a schematic view of a second check valve; FIG. 4 is a schematic configuration view of the hydraulic brake system, illustrating a state in which a braking force is generated by a master cylinder; FIG. 5 is a graph showing relationships between an amount of fluid supplied from the actuator and time, an opening degree of the second check valve and time, an opening degree of the second solenoid valve and time, and