Electric control hydraulic auxiliary braking system for load-bearing wheel of reach forklift and control method of electric control hydraulic auxiliary braking system

Abstract

The electric control hydraulic auxiliary braking system comprises a main pump and an execution hydraulic cylinder, the two ends of a main valve are connected with a prefill valve group, and the prefill valve group is connected with a braking main pump, a braking slave pump and an energy accumulator; the system further comprises a controller, the controller is connected with a main pump, a prefill valve set, a pressure sensor I and a pressure sensor II, and the pressure sensor II is arranged at the oil inlet end of the energy accumulator. The main valve, the prefill valve set, the brake main pump and the controller are used in cooperation to complete the auxiliary brake action, and when a vehicle is parked and lifts or moves front and back, bearing wheel braking can be automatically achieved, vehicle shaking is reduced, and vehicle stability is enhanced; the auxiliary brake of the bearing wheel only plays a role when the forklift portal frame ascends and descends or moves back and forth, so that the brake cylinder of the drum brake is prevented from being overheated; a brake pedal does not need to be stepped manually during auxiliary braking, and manpower burden is relieved; and meanwhile, when the vehicle travels, the traveling and emergency braking effects of the braking main pump are not affected.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering machinery, and in particular to an electronically controlled hydraulic auxiliary braking system for load-bearing wheels of a reach forklift and a control method thereof. Background Art

[0002] A gantry-type reach forklift has one drive wheel and two load-bearing wheels. Currently, the mainstream braking system for the drive wheel often uses an electromagnetic brake, which brakes when power is applied and releases when power is applied, serving as both the vehicle's service and parking brakes. Due to size and cost constraints, the load-bearing wheels often use drum brakes. Pressing the brake pedal presses brake fluid from the master cylinder into the drum brake's slave cylinder, driving the brake shoes to clamp against the friction pads and applying the brake. These brakes are often used as a supplement to emergency and service braking. When the forklift is parked, the braking force is solely on the drive wheels, with no braking force acting on the load-bearing wheels.

[0003] When the vehicle is stationary and the mast is being lifted, lowered, or moved forward or backward under a heavy load, the shift in the mast's center of gravity generates inertia. At this point, the vehicle is only braked by the drive wheels, not the load-bearing wheels. This results in insufficient vehicle stability and a tendency to wobble. If you apply the brake pedal at this point, you need to use one foot to press the enabling switch and the other to apply the brake pedal, which is both physically demanding and inconvenient.

[0004] A common solution is to replace the load-bearing wheels with electromagnetic brakes, but both the initial investment and subsequent maintenance costs are high. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a reach forklift load-bearing wheel electronically controlled hydraulic auxiliary braking system and a control method thereof with a simple structure and good effect.

[0006] The present invention is implemented by the following technical solution: an electronically controlled hydraulic auxiliary brake system for load-bearing wheels of a reach forklift, comprising a main pump, the main pump being connected to an actuator hydraulic cylinder via a main valve, both ends of the main valve being connected to a charging valve group, the charging valve group being connected to a brake slave pump via a brake master pump, and the charging valve group being further connected to an accumulator; Main valve, including lifting solenoid valve, lowering solenoid valve and forward and backward movement solenoid valve; The charging valve group includes a switch valve I, a switch valve II and a proportional reversing valve. The switch valve I is connected to the pressure oil end of the main valve, the switch valve II is connected to the actuator end of the main valve, and the accumulator is arranged at the oil inlet end of the proportional reversing valve; It also includes a controller, which is connected to a lifting solenoid valve, a lowering solenoid valve and a forward and backward moving solenoid valve, a switch valve I, a switch valve II, a proportional reversing valve, a pressure sensor I and a pressure sensor II, and the pressure sensor II is arranged at the oil inlet end of the accumulator.

[0007] It is further provided that: the main pump is connected to a motor.

[0008] The lifting solenoid valve and the lowering solenoid valve are connected to a lifting oil cylinder.

[0009] The switch valve I and the switch valve II are two-position two-way electromagnetic reversing valves, and the proportional reversing valve is a two-position four-way electromagnetic reversing valve. The proportional reversing valve has an emergency manual assembly.

[0010] The oil outlet ends of the switch valve I and the switch valve II are connected in parallel and then connected to the oil inlet end of the proportional reversing valve. The oil inlet end side of the proportional reversing valve is connected to a one-way valve and a pressure reducing valve.

[0011] The brake master pump includes a brake oil pot, a brake chamber, a push rod, a pressure switch, a hydraulic chamber and a foot pedal. The push rod divides the brake master pump into a brake chamber and a hydraulic chamber. The pressure switch is arranged on the hydraulic chamber. The brake oil pot is arranged on the brake chamber. The foot pedal is connected to the push rod on one side of the hydraulic chamber through a connecting rod.

[0012] The pressure switch is connected with the controller.

[0013] A control method for an electronically controlled hydraulic auxiliary brake system for a load-bearing wheel of a reach forklift includes the following auxiliary brake working process: When the controller determines that the vehicle is in the parking state and the person operates the vehicle to lift, lower, or move forward or backward, the controller supplies power to the coil of the main valve and the coil of the proportional reversing valve. The high-pressure oil in the accumulator enters the hydraulic chamber of the brake master pump, and the brake master pump drives the brake slave pump to brake the load-bearing wheels. When the controller detects the vehicle moving signal, the controller controls the proportional reversing valve to quickly cut off the power, and the hydraulic oil in the hydraulic chamber of the brake master pump is connected to the hydraulic oil tank. Under the action of the brake fluid in the brake chamber and the spring, the push rod returns to its position and the braking state of the load-bearing wheel is cancelled.

[0014] Accumulator charging process: When the controller detects that the pressure value of pressure sensor II is lower than the set value a, if it is in a heavy-load lowering condition, the switch valve I opens, and the medium-pressure oil in the lifting cylinder charges the accumulator through the charging valve group; otherwise, the switch valve II opens, and the main pump charges the accumulator. When the pressure in the accumulator reaches the set value b, the charging stops.

[0015] Fault detection: When the controller detects that the pressure switch of the hydraulic chamber is always working, but the proportional reversing valve is not powered, it means that the valve core of the proportional reversing valve is stuck. Use the emergency manual component of the proportional reversing valve to depressurize the hydraulic chamber and release the load-bearing wheel brake.

[0016] The present invention has the following advantages: the electronically controlled hydraulic auxiliary braking system for the load-bearing wheels of the forward-moving forklift of the present invention and the control method thereof, through the coordinated use of the main valve, the filling valve group, the brake master pump and the controller, complete the auxiliary braking action. When the vehicle is parked and lifted or moved forward and backward, the load-bearing wheels can be automatically braked, the vehicle shaking is reduced, and the vehicle stability is enhanced; and the load-bearing wheel auxiliary braking only takes effect when the forklift mast is raised and lowered or moved forward and backward, avoiding overheating of the drum brake brake cylinder; no manual labor is required to step on the brake pedal during auxiliary braking, reducing the manpower burden; at the same time, when the vehicle is moving, it does not affect the movement of the brake master pump and the emergency braking effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, as part of this disclosure, are intended to provide a further understanding of the disclosure. The exemplary embodiments of the disclosure and their descriptions are intended to explain the disclosure and do not constitute undue limitations thereon. Obviously, the drawings described below are merely examples, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0018] In the attached figure: Figure 1 It is a hydraulic principle diagram of the present invention.

[0019] In the figure: 1. Lifting cylinder, 2. Pressure sensor I, 3. Main valve, 31. Lifting solenoid valve, 32. Lowering solenoid valve, 33. Forward and backward movement solenoid valve, 4. Motor, 5. Main pump, 6. Charging valve group, 61. Proportional reversing valve, 62. Check valve, 63. Pressure reducing valve, 64. Switch valve I, 65. Switch valve II, 7. Pressure sensor II, 8. Accumulator, 9. Brake slave pump, 10. Brake master pump, 101. Brake oil tank, 102. Brake chamber, 103. Push rod, 104. Pressure switch, 105. Hydraulic chamber, 106. Foot pedal.

[0020] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0023] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; and direct or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0024] like Figure 1The electronically controlled hydraulic auxiliary brake system for the load-bearing wheels of a reach-type forklift shown in the figure includes a main pump 5, which is connected to a motor 4, and is connected to an actuator hydraulic cylinder through a main valve 3. Both ends of the main valve 3 are connected to a charging valve group 6, which is connected to a brake slave pump 9 through a brake master pump 10. The charging valve group 6 is also connected to an accumulator 8; the main valve 3 includes a lifting solenoid valve 31, a lowering solenoid valve 32, and a forward and backward movement solenoid valve 33; the charging valve group 6 includes a switch valve I 64, a switch valve II 65 and a proportional reversing valve 61, the switch valve I 64 is connected to the pressure oil end of the main valve 3, the switch valve II 65 is connected to the execution end of the main valve 3, and the accumulator 8 is arranged at the oil inlet end of the proportional reversing valve 61; it also includes a controller, the controller is connected to the lifting solenoid valve 31, the lowering solenoid valve 32 and the forward and backward movement solenoid valve 33, the switch valve I 64, the switch valve II 65, the proportional reversing valve 61, the pressure sensor I and the pressure sensor II7, and the pressure sensor II7 is arranged at the oil inlet end of the accumulator 8. The hydraulic assisted braking system of the load-bearing wheel of the forward-moving forklift of the present invention comprises a main pump, a filling valve group, a brake master pump, a brake slave pump and a controller. The main pump mainly comprises a lifting solenoid valve, a lowering solenoid valve and a forward and backward solenoid valve. The main valve is connected with the lifting oil cylinder and the forward oil cylinder to control the lifting and lowering of the lifting oil cylinder and the forward and backward movement of the forward oil cylinder respectively; the filling valve group comprises a switch valve I, a switch valve II and a proportional reversing valve. The oil inlet ends of the switch valve I and the switch valve II are respectively connected to the two ends of the main pump, and the oil outlet ends of the switch valve I and the switch valve II are connected in parallel with the proportional reversing valve. The proportional reversing valve is also connected to an accumulator, wherein the switch valve controls whether the pressure oil can enter the filling valve group to fill the accumulator. The proportional reversing valve is a proportional control valve and has an emergency manual component. When power is off, it connects the hydraulic chamber and the hydraulic oil tank. After power is on, it controls the hydraulic oil to enter the brake master pump. The accumulator stores hydraulic oil as the load-bearing The power of wheel braking; the proportional reversing valve is connected to the brake master pump to provide hydraulic oil for the brake master pump, and the brake master pump drives the brake slave pump to brake the forklift's load-bearing wheels; it also includes a controller, which is connected to the lifting solenoid valve, the lowering solenoid valve and the forward and backward movement solenoid valve, the switch valve I, the switch valve II, the proportional reversing valve, the pressure sensor I and the pressure sensor II. The pressure sensor II is arranged at the oil inlet end of the accumulator and is used to detect the pressure in the accumulator in the system. The controller determines whether to open the switch valve for filling the fluid at this moment according to the detection information of the pressure sensor II; at the same time, the controller collects the coil signals of each solenoid valve in the main valve. When it is detected that the forklift is parked and lifted or moved forward and backward, the controller controls the proportional reversing valve to operate. The accumulator supplies oil to the brake master pump through the proportional reversing valve, thereby driving the brake slave pump to operate, thereby achieving auxiliary braking of the load-bearing wheels when parking and enhancing vehicle stability.

[0025] like Figure 1The electronically controlled hydraulic auxiliary brake system for the load-bearing wheels of a reach forklift is shown. The lifting solenoid valve 31 and the lowering solenoid valve 32 are connected to the lifting cylinder 1. The rodless chamber of the lifting cylinder is connected to a pressure sensor I, which is used to detect the pressure in the lifting cylinder and determine whether the cylinder is under heavy load.

[0026] like Figure 1 The electronically controlled hydraulic auxiliary brake system for the load-bearing wheels of a reach-forklift shown in the figure, the switch valve I 64 and the switch valve II 65 are two-position two-way electromagnetic reversing valves, the proportional reversing valve 61 is a two-position four-way electromagnetic reversing valve, and the proportional reversing valve 61 has an emergency manual component. The oil outlet ends of the switch valve I 64 and the switch valve II 65 are connected in parallel to the oil inlet pipe of the proportional reversing valve 61, and the oil inlet side of the proportional reversing valve 61 is connected to a one-way valve 62 and a pressure reducing valve 63. The filling valve group of the present invention includes a switch valve I, a switch valve II, a pressure reducing valve, a one-way valve and a proportional reversing valve, wherein the oil inlets of the switch valve I and the switch valve II are respectively connected to the two ends of the main valve, as shown in FIG. Figure 1 As shown, the P port of the main valve is connected to the P2 port of the charging valve group, and the H port of the main valve is connected to the P1 port of the charging valve group. The switch valve is used to control whether the pressure oil can enter the charging valve group to charge the accumulator; the oil outlets of the switch valve I and the switch valve II are connected in parallel and then connected to the pressure reducing valve. The pressure reducing valve prevents the hydraulic oil pressure from being too high and causing damage to the brake master pump; a one-way valve is set at the oil outlet end of the pressure reducing valve, and the accumulator and the proportional reversing valve are connected behind the one-way valve. The one-way valve can prevent oil backflow; the proportional reversing valve is a proportional control valve and has an emergency manual component. When power is off, it connects the hydraulic chamber of the brake master pump and the hydraulic oil tank. When power is on, it controls the hydraulic oil of the accumulator to enter the brake master pump to achieve auxiliary braking during parking.

[0027] like Figure 1 The illustrated electronically controlled hydraulic auxiliary brake system for the load-bearing wheels of a reach forklift truck features a brake master pump 10 comprising a brake oil reservoir 101, a brake chamber 102, a push rod 103, a pressure switch 104, a hydraulic chamber 105, and a foot pedal 106. The push rod 103 divides the brake master pump 10 into the brake chamber 102 and the hydraulic chamber 105. The pressure switch 104 is located in the hydraulic chamber 105, and the brake oil reservoir 101 is located in the brake chamber 102. The foot pedal 106 is connected to the push rod 103 on one side of the hydraulic chamber 105 via a connecting rod. The pressure switch 104 is connected to a controller. The brake master pump of the present invention is a dual-fluid brake pump, comprising a brake oil reservoir, a brake chamber, a hydraulic chamber, a push rod, a pressure switch, and a foot pedal. The brake oil reservoir stores brake fluid, the hydraulic chamber acts as a hydraulic oil chamber, and the brake chamber acts as a brake fluid chamber. Hydraulic oil entering the hydraulic chamber pushes the push rod to compress the brake chamber. The compressed brake fluid in the brake chamber enters the brake slave pump, driving the brake shoe to achieve braking. The pressure switch on the brake master pump is used to detect the pressure in the hydraulic chamber and control the opening and closing of the proportional reversing valve.

[0028] A control method for an electronically controlled hydraulic auxiliary brake system for a load-bearing wheel of a reach forklift includes the following auxiliary brake working process: When the controller determines that the vehicle is in the parking state and the person operates the vehicle to lift, lower, or move forward or backward, the controller supplies power to the coil of the main valve 3 and the coil of the proportional reversing valve 61. Specifically, the electromagnetic coil m1, m2, m3, m4 or m7 is energized, and the high-pressure oil in the accumulator 8 enters the hydraulic chamber 105 of the brake master pump 10, pushing the push rod to compress the brake chamber volume. The brake fluid is squeezed into the brake slave pump, thereby driving the brake shoe to brake the load-bearing wheel. At this time, the vehicle stability is improved and the forward and backward shaking amplitude is reduced. When the controller detects the vehicle moving signal, the controller controls the proportional reversing valve 61 to quickly cut off the power, that is, the electromagnetic coil m7 is quickly cut off, and the hydraulic oil in the hydraulic chamber 105 of the brake master pump 10 is connected to the hydraulic oil tank. Under the action of the brake fluid in the brake chamber 102 and the spring, the push rod 103 returns to its position, and the braking state of the load-bearing wheel is cancelled.

[0029] Accumulator charging process: When the controller detects that the pressure value of pressure sensor II 7 is lower than the set value a, if the vehicle is in the heavy-load lowering condition, switch valve I 65 opens, energizing solenoid m5. The medium-pressure oil in lift cylinder 1 charges accumulator 8 through charging valve group 6. Otherwise, switch valve II opens, energizing solenoid m6, and main pump 5 charges accumulator 8. When the pressure in accumulator 8 reaches the set value b, charging stops. Switch valves I and II cannot be opened simultaneously. The set pressure of the pressure reducing valve is equal to the pressure sensor set value b and greater than the set value a.

[0030] Fault detection: When the controller detects that the pressure switch 104 of the hydraulic chamber 105 is always working, but the proportional reversing valve 61 is not powered, it means that the valve core of the proportional reversing valve 61 is stuck. The emergency manual component of the proportional reversing valve 61 is used to depressurize the hydraulic chamber 105 and release the load-bearing wheel brake.

[0031] The present invention provides an electronically controlled hydraulic auxiliary braking system and control method for the load-bearing wheels of a reach forklift. The auxiliary braking system can automatically brake the load-bearing wheels when the vehicle is lifting, lowering, or moving forward and backward, so as to enhance the stability of the vehicle. When the electronically controlled hydraulic auxiliary braking system is not working, the brake master pump can still achieve foot-operated manual braking without destroying the walking and emergency braking functions. The system of the present application not only has a structural order and reduces costs, but also reduces the manpower burden and enhances the stability of the vehicle's operating conditions.

[0032] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0033] Furthermore, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are also intended to fall within the scope of protection of the present invention and form different embodiments. For example, in the above embodiments, those skilled in the art will be able to use them in combination based on the known technical solutions and the technical problems to be solved by this application.

[0034] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with this patent can make slight changes or modifications to equivalent embodiments using the above-mentioned technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. An electronically controlled hydraulic auxiliary braking system for load-bearing wheels of a reach forklift, characterized by: The invention comprises a main pump (5), wherein the main pump (5) is connected to an actuator hydraulic cylinder via a main valve (3), both ends of the main valve (3) are connected to a charging valve group (6), the charging valve group (6) is connected to a brake slave pump (9) via a brake master pump (10), and the charging valve group (6) is also connected to an accumulator (8); A main valve (3), comprising a lifting solenoid valve (31), a lowering solenoid valve (32), and a forward and backward movement solenoid valve (33); A charging valve group (6) includes a switch valve I (64), a switch valve II (65) and a proportional reversing valve (61), wherein the switch valve I (64) is connected to the pressure oil end of the main valve (3), the switch valve II (65) is connected to the execution end of the main valve (3), and the accumulator (8) is arranged at the oil inlet end of the proportional reversing valve (61); The invention also includes a controller, wherein the controller is connected to a lifting solenoid valve (31), a lowering solenoid valve (32), a forward and backward moving solenoid valve (33), a switch valve I (64), a switch valve II (65), a proportional reversing valve (61), a pressure sensor I (2) and a pressure sensor II (7), wherein the pressure sensor II (7) is arranged at the oil inlet end of the accumulator (8).

2. The electronically controlled hydraulic auxiliary brake system for load-bearing wheels of a reach forklift according to claim 1, characterized in that: The main pump (5) is connected to a motor (4).

3. The electronically controlled hydraulic auxiliary brake system for load-bearing wheels of a reach forklift according to claim 1, characterized in that: The lifting solenoid valve (31) and the lowering solenoid valve (32) are connected to the lifting oil cylinder (1).

4. The electronically controlled hydraulic auxiliary braking system for load-bearing wheels of a reach forklift according to claim 1, characterized in that: The switch valve I (64) and the switch valve II (65) are two-position two-way electromagnetic directional valves, and the proportional directional valve (61) is a two-position four-way electromagnetic directional valve. The proportional directional valve (61) has an emergency manual assembly.

5. The electronically controlled hydraulic auxiliary brake system for load-bearing wheels of a reach forklift according to claim 1, characterized in that: The oil outlet ends of the switch valve I (64) and the switch valve II (65) are connected in parallel and then connected to the oil inlet end of the proportional reversing valve (61). The oil inlet end side of the proportional reversing valve (61) is connected to a one-way valve (62) and a pressure reducing valve (63).

6. The electronically controlled hydraulic auxiliary braking system for load-bearing wheels of a reach forklift according to claim 1, characterized in that: The brake master pump (10) comprises a brake oil pot (101), a brake chamber (102), a push rod (103), a pressure switch (104), a hydraulic chamber (105) and a foot pedal (106). The push rod (103) divides the brake master pump (100) into a brake chamber (102) and a hydraulic chamber (105). The pressure switch (104) is arranged on the hydraulic chamber (105). The brake oil pot (101) is arranged on the brake chamber (102). The foot pedal (106) is connected to the push rod (103) on one side of the hydraulic chamber (105) through a connecting rod.

7. The electronically controlled hydraulic auxiliary braking system for load-bearing wheels of a reach forklift according to claim 6, characterized in that: The pressure switch (104) is connected to the controller.

8. A control method for the electronically controlled hydraulic auxiliary brake system for load-bearing wheels of a reach forklift according to claim 1, characterized in that: Including auxiliary braking working process, as follows: When the controller determines that the vehicle is in a parking state and a person operates the vehicle to lift, lower, or move forward or backward, the controller supplies power to the coil of the main valve (3) and the coil of the proportional reversing valve (61), and the high-pressure oil in the accumulator (8) enters the hydraulic chamber (105) of the brake master pump (10), and the brake master pump (10) drives the brake slave pump (9) to operate to achieve load-bearing wheel braking; When the controller detects a vehicle moving signal, the controller controls the proportional reversing valve (61) to quickly cut off the power, and the hydraulic oil in the hydraulic chamber (105) of the brake master pump (10) is connected to the hydraulic oil tank. Under the action of the brake fluid in the brake chamber (102) and the spring, the push rod (103) returns to its position, and the load-bearing wheel braking state is cancelled.

9. The control method of the electronically controlled hydraulic auxiliary brake system for the load-bearing wheels of a reach forklift according to claim 8, characterized in that: Accumulator filling process: When the controller detects that the pressure value of pressure sensor II (7) is lower than the set value a, if it is in the heavy load lowering condition, the switch valve I (65) is opened, and the medium pressure oil of the lifting cylinder (1) is charged to the accumulator (8) through the charging valve group (6); otherwise, the switch valve II is opened, and the main pump (5) is used to charge the accumulator (8). When the pressure in the accumulator (8) reaches the set value b, the charging is stopped.

10. The control method of the electronically controlled hydraulic auxiliary braking system of the load-bearing wheel of a reach forklift according to claim 8, characterized in that: Fault detection: When the controller detects that the pressure switch (104) of the hydraulic chamber (105) is always working, but the proportional reversing valve (61) is not powered, it means that the valve core of the proportional reversing valve (61) is stuck. The emergency manual component of the proportional reversing valve (61) is used to release the pressure of the hydraulic chamber (105) and release the load-bearing wheel brake.

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