Automatic parking hydraulic system of skid loader

Abstract

The invention discloses an automatic parking hydraulic system of a skid loader. The automatic parking hydraulic system comprises a walking / working handle, a control valve group, a walking pump / motor, a brake, an engine and the like. A first shuttle valve, a hydraulic control reversing valve and three electromagnetic switch valves are arranged in the control valve group, a pressure signal of the walking operation handle is transmitted to the hydraulic control reversing valve through the first shuttle valve, and on-off of an oil way of the brake is controlled in a linkage mode; an oil supplementing pump and a DA valve are arranged in the walking pump, and a variable control piston is arranged. The system realizes automatic locking of a brake and synchronous unlocking of a push handle without walking operation, and thoroughly solves the hidden danger of slope sliding caused by easy forgetting of traditional manual parking and system leakage; functions of walking and getting-on operation are isolated through an electromagnetic switch valve, and the operation intensity is reduced; the oil recharging pump recharges leakage and controls temperature, the DA valve dynamically regulates pressure, the variable control piston accurately regulates flow, a unified oil return loop is matched, stability and smooth operation of the system are guaranteed, complex working conditions are adapted, and safety, reliability and practical value of equipment are improved.

Description

Technical Field

[0001] This invention relates to an automatic parking hydraulic system for a skid steer loader, belonging to the field of engineering machinery technology. Background Technology

[0002] Skid steer loaders, as core equipment in confined spaces and complex operating conditions, rely on hydraulic brakes to lock the output shaft of the travel motor for parking safety—the mainstream parking control solution in the industry. In existing technology, the hydraulic brake's on / off state is entirely controlled by the driver manually operating a control switch. By switching the hydraulic circuit's on / off state, the brake is locked and unlocked. This control logic is simple and low-cost, meeting basic parking requirements in flat terrain. However, in practical applications, skid steer loaders often need to perform material handling or operations in sloping environments such as construction pits and hillsides, where the limitations of traditional manual control become increasingly apparent.

[0003] In slope operation scenarios, after the driver stops moving, they must manually press the parking control switch to activate slope parking, increasing the number of steps and workload for the driver. Because drivers of skid steer loaders need to simultaneously monitor the movement of attachments and the safety of the surrounding environment, they are prone to forgetting to perform the manual parking operation due to distraction. Furthermore, in some operating conditions, drivers need to frequently switch between moving and operating states; repeated manual parking operations not only affect work efficiency but also pose a risk of accidental brake unlocking due to operator fatigue. In addition, existing manual control switches lack a linkage mechanism with moving movements, meaning that even after the driver completes the parking operation, the safety hazard of accidental brake unlocking due to accidental switch activation cannot be avoided.

[0004] More importantly, during long-term use, hydraulic systems inevitably experience internal oil leakage due to factors such as seal wear and pipeline aging. When a skid steer loader is parked on a slope, if manual parking is not performed in time, or if the parking operation fails, the internal leakage will cause the back pressure of the hydraulic brake to gradually decrease. When the component of the machine's weight on the slope exceeds the adhesion traction force generated by the internal leakage back pressure, the entire machine will slowly roll away. Due to the large mass and strong inertia of skid steer loaders, once rollaway occurs, it will not only cause collision damage to the equipment but may also endanger the lives of nearby workers, especially in narrow slopes or near pits or cliffs, where the severity of such safety hazards is even greater. Existing technology has failed to solve the dual risks of reliance on manual operation and system leakage, urgently requiring a reliable parking control solution adapted to slope conditions. Summary of the Invention

[0005] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides an automatic parking hydraulic system for skid steer loaders that solves the problems mentioned in the background section.

[0006] Technical solution: An automatic parking hydraulic system for a skid steer loader, comprising a travel control handle, a working handle, a control valve group, at least two travel motors, brakes corresponding to each travel motor, an engine, and a travel pump and oil tank driven by the engine. The walking operation handle has four built-in shuttle valves and a walking control rocker arm. The four shuttle valves are connected to the control valve group and the walking pump through four signal ports C, D, E, and F, respectively. Ports C and E are connected to ports a2 and a1 of the control valve group, respectively. The oil circuit of the control rocker arm is connected to port C of the control valve group through port P on the walking operation handle. The control valve group is equipped with a first shuttle valve, a hydraulic directional valve, a first solenoid valve, a second solenoid valve, and a third solenoid valve, with their two ends connected to ports a1 and a2, respectively. The first shuttle valve is connected to the external control port of the hydraulic directional valve. When the first solenoid valve is energized, it connects to ports P1 and C of the control valve group. When the second solenoid valve is energized, it connects to ports P2 and D of the control valve group. Port D of the control valve group is connected to the oil chamber of the brake. When the third solenoid valve is energized, it connects to ports P2 and E of the control valve group. Port E of the control valve group is connected to port P of the working handle.

[0007] This invention addresses the safety hazard of skid steer loaders slipping on slopes due to internal leaks in the travel pump and travel motor. It also solves the problem of unclear separation between travel and overhead operation functions, which can easily lead to accidents due to misoperation. By constructing a linked control system of "travel operating handle - control valve group - travel pump - travel motor - brake," the invention utilizes a first shuttle valve to detect the handle pressure signal and a hydraulic control directional valve to control the brake oil circuit, achieving automatic parking on slopes with "automatic brake locking when no handle is operated," completely eliminating the risk of slippage. Simultaneously, three electromagnetic switch valves control the oil circuit access permissions for travel and overhead operation respectively, enabling independent unlocking / locking of the two functions, avoiding equipment collisions or unexpected actions caused by misoperation, and balancing parking safety with standardized operation.

[0008] The hydraulic control directional valve is a spring-reset two-position directional valve. Under normal conditions, it is kept in the right position by the action of the spring and is used to automatically switch to the oil return and pressure relief position when there is no pressure signal.

[0009] This invention addresses the issue where, during operation without a handle, the hydraulic directional valve fails to automatically reset to the return oil position, leading to insufficient brake control fluid depressurization and parking lock failure. By reconfiguring the hydraulic directional valve as a spring-reset two-position valve, the spring's constant force maintains the right-hand position. This ensures that in the absence of a pressure signal (no handle operation), the brake fluid circuit automatically switches to the return oil depressurization state, achieving brake lock-up without additional control commands. This guarantees the reliability and timeliness of hill-start assist parking and further enhances the safety redundancy of the automatic parking function.

[0010] The traveling pump has a built-in oil replenishment pump and a DA valve. The oil replenishment pump's suction port is connected to the oil tank, and its outlet port is connected to the DA valve's inlet port.

[0011] This invention addresses the issue of insufficient system pressure and excessively high oil temperature caused by oil leakage in the travel motor and component housings of skid steer loaders' closed-loop travel systems, which negatively impacts system stability and lifespan. By integrating a replenishing pump and a DA valve into the travel pump, the replenishing pump draws oil from the oil tank and replenishes the system, promptly compensating for leaks and maintaining oil balance in the closed-loop system. Simultaneously, the replenishing pump outputs oil to provide a stable supply to the DA valve, preventing regulation failure due to insufficient oil, effectively controlling system oil temperature, ensuring the normal operation of core components such as the travel pump and travel motor, and extending the overall system lifespan.

[0012] The oil outlet of the DA valve is connected to the P1 oil port of the control valve group, and is used to output a pressure signal of corresponding magnitude to the P1 oil port according to the engine speed; the G oil port of the travel pump is connected to the P2 oil port of the control valve group, and provides pressurized oil to the second solenoid switch valve and the third solenoid switch valve.

[0013] This invention addresses the issues of mismatch between the P1 port pressure signal and engine speed, which leads to the travel pump's output flow not meeting power demands, as well as the lack of stable pressure oil supply to the second and third solenoid valves and the failure of access control. The DA valve dynamically outputs a corresponding pressure signal to the P1 port based on engine speed, achieving a precise match between "engine speed - P1 port pressure - travel pump flow." This ensures that the travel pump outputs a large flow at high speeds to meet rapid travel needs, and a small flow at low speeds to support smooth movement. Simultaneously, it provides stable pressure oil to the second and third solenoid valves through the travel pump's G port, ensuring reliable oil circuit continuity when the travel and on-board operation functions are unlocked, preventing operational malfunctions due to insufficient oil supply, and improving system control accuracy and stability.

[0014] The travel pump is equipped with two variable control pistons. The pilot control ports X1, X2, X3, and X4 of the travel pump are connected to the two variable control pistons respectively. They are used to receive the pressure signal transmitted by the travel operation handle. By adjusting the stroke of the variable control pistons, the direction and magnitude of the travel pump output flow are controlled, thereby driving the two travel motors to move.

[0015] This invention addresses the problem of uncontrolled loader travel speed and inflexible steering caused by the inability to precisely adjust the direction and magnitude of the travel pump's output flow according to operational needs. By connecting the four pilot control ports of the travel pump to two variable displacement control pistons, the pressure signal from the travel control handle directly drives the variable displacement control pistons to adjust their stroke. This allows for precise control of the direction (forward / reverse) and magnitude (speed) of the travel pump's output flow, achieving stepless adjustment of the loader's travel speed and flexible steering control. This adapts to different working conditions, improving operational smoothness and work efficiency.

[0016] The brake oil chamber corresponding to the travel motor is connected to the D port of the control valve group after being integrated through a three-way valve; the L port of the travel motor is connected to the oil tank to discharge the leaked oil generated during the operation of the motor.

[0017] This solution addresses the issues of inconsistent brake oil supply to multiple travel motors, leading to poor braking synchronization, and the inability to effectively drain leaking oil during motor operation, which can cause internal motor damage. By integrating the oil chambers of each brake with a three-way valve and connecting it to the D port of the control valve assembly, pressurized oil enters each brake synchronously, achieving complete synchronization of braking actions across multiple motors and preventing equipment deviation due to uneven braking. Simultaneously, the L port of each travel motor is connected to the oil tank to promptly drain leaking oil during motor operation, preventing oil accumulation that could cause internal component wear or abnormal pressure, and ensuring long-term stable operation of the travel motors.

[0018] The T-ports of the walking operation handle, the working handle, and the control valve group are all connected to the oil tank, forming a unified oil return circuit for the system and ensuring smooth oil return to each component.

[0019] This solution addresses the problems of scattered and poorly maintained oil return paths among system components, leading to oil pressure buildup, component overheating, or sluggish operation. By unifying the T-ports of the travel control handle, work handle, and control valve assembly with the oil tank, a unified system-level oil return circuit is constructed. This ensures that oil returns quickly and smoothly to the oil tank after each component's operation, preventing pressure buildup caused by excessive return resistance. Simultaneously, it reduces oil residence time in the circuit, lowers the risk of overheating, ensures the responsiveness and reliability of each hydraulic component, and improves the overall system operating efficiency.

[0020] Beneficial Effects: This invention solves the safety hazards of traditional skid steer loaders relying on manual operation for hill parking, which is prone to slippage due to forgetting to operate or system leaks. It achieves automatic hill parking with the brakes automatically locking when there is no driving operation and unlocking simultaneously when the handle is pushed, effectively eliminating the risk of slippage caused by internal leaks. Simultaneously, three electromagnetic valves independently control the oil circuit access permissions for driving and onboard operations, achieving safe isolation between the two functions, avoiding equipment collisions or unexpected actions due to misoperation, and reducing the driver's workload and intensity. Furthermore, the built-in replenishing pump in the driving pump can promptly replenish leaked oil in the closed system and maintain thermal balance. The DA valve dynamically matches the P1 port pressure according to engine speed, and the variable piston precisely adjusts the driving pump flow. The smooth return flow design of the unified return oil circuit further ensures system stability, smooth operation, and work efficiency, fully adapting to complex working conditions such as narrow spaces and hilltop operations for skid steer loaders, significantly improving the safety, reliability, and practical value of the equipment. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the hydraulic system of the present invention.

[0023] Figure 2 This is a hydraulic schematic diagram of the control valve assembly of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0027] like Figure 1 and 2 As shown, an automatic parking hydraulic system for a skid steer loader includes a travel control handle 1, a working handle 2, a control valve group 3, at least two travel motors 4, brakes 5 corresponding to each of the travel motors 4, an engine 6, a travel pump 7 driven by the engine 6, and an oil tank 8. The walking operation handle 1 has four built-in shuttle valves and a walking control rocker arm. The four shuttle valves are connected to the control valve group 3 and the walking pump 7 through four signal oil ports C, D, E, and F, respectively. Ports C and E are connected to oil ports a2 and a1 of the control valve group 3, respectively. The oil circuit of the control rocker arm is connected to port C of the control valve group 3 through port P on the walking operation handle 1. The control valve group 3 is equipped with a first shuttle valve 31, a hydraulic directional valve 32, a first solenoid switch valve 33, and a second solenoid switch valve 34, both ends of which are connected to oil ports a1 and a2, respectively. The system includes a magnetic switch valve 34 and a third electromagnetic switch valve 35; the first shuttle valve 31 is connected to the external control port of the hydraulic directional valve 32; the first electromagnetic switch valve 33 is energized and connected to the P1 port and C port of the control valve group 3; the second electromagnetic switch valve 34 is energized and connected to the P2 port and D port of the control valve group 3; the D port of the control valve group 3 is connected to the oil chamber of the brake 5; the third electromagnetic switch valve 35 is energized and connected to the P2 port and E port of the control valve group 3; the E port of the control valve group 3 is connected to the P port of the working handle 2.

[0028] This invention addresses the safety hazard of skid steer loaders slipping on slopes due to internal leakage in the travel pump 7 and travel motor 4 when parked. It also solves the problem of unclear separation between the travel function and the onboard operation function, which can easily lead to dangerous situations due to misoperation. By constructing a linked control system of "travel operating handle 1, control valve group 3, travel pump 7, travel motor 4, and brake 5," the invention utilizes the first shuttle valve 31 to detect the handle pressure signal and the hydraulic control directional valve 32 to control the oil circuit of brake 5, achieving an automatic parking function on slopes where "brake 5 automatically locks when no handle is operated," completely eliminating the risk of slippage. Simultaneously, three electromagnetic switch valves control the oil circuit access permissions for travel and onboard operation respectively, enabling independent unlocking / locking of the two functions, avoiding equipment collisions or unexpected actions caused by misoperation, and balancing parking safety and operational standardization.

[0029] The hydraulic control directional valve 32 is a spring-reset two-position directional valve. Under normal conditions, it is kept in the right position by the action of the spring and is used to automatically switch to the oil return and pressure relief position when there is no pressure signal.

[0030] To address the issue where the hydraulic directional valve 32 fails to automatically reset to the return oil position when operated without a handle, resulting in insufficient pressure relief of the brake 5 control oil and failure of the parking lock, the hydraulic directional valve 32 is configured as a spring-reset two-position directional valve. Utilizing the constant force of the spring to maintain the right position, it ensures that when there is no pressure signal or handle operation, the brake 5 oil circuit automatically switches to the return oil pressure relief state. This allows for brake 5 locking without additional control commands, ensuring the reliability and timeliness of hill-start assist and further enhancing the safety redundancy of the automatic parking function.

[0031] The walking pump 7 has a built-in oil replenishment pump 71 and a DA valve 72. The oil inlet of the oil replenishment pump 71 is connected to the oil tank 8, and the oil outlet is connected to the oil inlet of the DA valve 72.

[0032] This invention addresses the problem of insufficient system pressure and excessively high oil temperature caused by oil leakage from the travel motor 4 and component housings in the closed-loop travel system of skid steer loaders. By incorporating a replenishing pump 71 and a DA valve 72 into the travel pump 7, the replenishing pump 71 draws oil from the oil tank 8 and replenishes the system, promptly compensating for leaks and maintaining the oil balance of the closed-loop system. Simultaneously, the replenishing pump 71 outputs oil to provide a stable oil supply to the DA valve 72, preventing regulation failure due to insufficient oil, effectively controlling system oil temperature, ensuring the normal operation of core components such as the travel pump 7 and travel motor 4, and extending the overall service life of the system.

[0033] The oil outlet of the DA valve 72 is connected to the P1 oil port of the control valve group 3, and is used to output a pressure signal of corresponding magnitude to the P1 oil port according to the speed of the engine 6; the G oil port of the travel pump 7 is connected to the P2 oil port of the control valve group 3, and provides pressurized oil to the second solenoid switch valve 34 and the third solenoid switch valve 35.

[0034] This invention addresses the issues of mismatch between the P1 oil port pressure signal and the engine speed (6), which leads to the travel pump 7's output flow rate failing to meet power demands, and the second and third solenoid valves 35 experiencing unstable pressure oil supply and control malfunction. The DA valve dynamically outputs a corresponding pressure signal to the P1 oil port based on the engine speed (6), achieving precise matching between "engine speed (6), P1 oil port pressure, and travel pump 7 flow rate." This ensures that the travel pump 7 outputs a large flow rate at high speeds to meet rapid travel needs, and a small flow rate at low speeds to support smooth movement. Simultaneously, it provides stable pressure oil to the second and third solenoid valves 35 via the travel pump 7's G port, ensuring reliable oil circuit continuity when the travel and on-vehicle operation functions are unlocked, preventing operational malfunctions due to insufficient oil supply, and improving system control accuracy and stability.

[0035] The travel pump 7 is equipped with two variable control pistons 73. The pilot control ports X1, X2, X3, and X4 of the travel pump 7 are connected to the two variable control pistons 73 respectively. They are used to receive the pressure signal transmitted by the travel operation handle 1. By adjusting the stroke of the variable control pistons 73, the direction and magnitude of the output flow of the travel pump 7 are controlled, thereby driving the two travel motors 4 to move.

[0036] This invention addresses the problem of the inability to precisely adjust the direction and magnitude of the output flow of the travel pump 7 according to operational needs, which leads to uncontrolled loader travel speed and inflexible steering. By connecting the four pilot control ports of the travel pump 7 to two variable displacement control pistons 73, the pressure signal from the travel operation handle 1 can directly drive the variable displacement control pistons 73 to adjust their stroke. This allows for precise control of the direction, magnitude, and speed of the output flow of the travel pump 7, achieving stepless adjustment of the loader's travel speed and flexible steering control. This adapts to different working conditions, improving operational smoothness and work efficiency.

[0037] The oil chamber of the brake 5 corresponding to the travel motor 4 is connected to the D port of the control valve group 3 after being integrated through a three-way valve; the L port of the travel motor 4 is connected to the oil tank 8 to discharge the leaked oil generated during the operation of the motor.

[0038] This invention addresses the issues of inconsistent oil supply to the brakes 5 of multiple travel motors 4, leading to poor braking synchronization, and the inability to effectively drain leaking oil during the operation of the travel motors 4, which can easily cause internal damage to the motors. By integrating the oil chambers of each brake 5 with a three-way valve and connecting it to the D port of the control valve group 3, pressurized oil is ensured to enter each brake 5 synchronously, achieving complete synchronization of braking actions across multiple motors and preventing equipment deviation due to uneven braking. Simultaneously, the L port of the travel motor 4 is connected to the oil tank 8 to promptly drain leaking oil during motor operation, preventing oil accumulation that could cause wear on internal parts or abnormal pressure, and ensuring long-term stable operation of the travel motors 4.

[0039] The T-ports of the walking operation handle 1, the working handle 2, and the control valve group 3 are all connected to the oil tank 8, forming a unified oil return circuit for the system, ensuring smooth oil return to each component.

[0040] This solution addresses the problems of scattered and poorly controlled oil return paths among system components, leading to oil pressure buildup, component overheating, or sluggish operation. By connecting the T-ports of the travel control handle 1, work handle 2, and control valve group 3 to the oil tank 8, a unified system-level oil return circuit is constructed. This ensures that the oil returned to the oil tank 8 quickly and smoothly after each component's operation, preventing pressure buildup caused by excessive return resistance. Simultaneously, it reduces the oil's residence time in the circuit, lowers the risk of overheating, ensures the responsiveness and reliability of each hydraulic component, and improves the overall system operating efficiency.

[0041] Working principle: When parking on a slope, the driver stops the travel operation and does not manually unlock the travel function, leaving the machine stationary on the slope. The travel control handle has no pushing force, and its C and E ports have no pressure signal output, causing the a1 and a2 ports of the control valve group to be depressurized. Because there is no pressure difference between the a1 and a2 ports, the first shuttle valve has no pressure signal output to the external control port of the hydraulic directional valve. The hydraulic directional valve loses external control pressure and remains in the right position under the action of the spring return force. At this time: Cut off the connection between the P2 port and the D port of the control valve assembly (block the brake unlocking oil circuit). Connect the control valve group D port to the oil return circuit (T port) to provide a path for brake pressure relief.

[0042] The first electromagnetic switch valve loses power, cutting off the oil circuit between the oil port of valve block P1 and the oil supply port of the travel handle; The second electromagnetic switch valve loses power, cutting off the oil circuit between the valve block P2 oil port and the hydraulic control directional valve; The third electromagnetic switch valve loses power, cutting off the oil circuit between the valve block P2 oil port and the working handle.

[0043] Because there is no pressure signal input from the travel handle, the pilot control ports X1, X2, X3, and X4 of the travel pump are pressureless, the variable control piston does not move, and the travel pump has no flow output.

[0044] The brake and the travel motor: The Z port (control oil port) of the built-in brake of the travel motor is connected to the oil tank through the right position of the hydraulic control directional valve → T port, and the oil pressure is released; The brake automatically locks the output shaft of the travel motor under the action of spring force, restricting the motor rotation. The whole machine achieves parking on slopes through mechanical locking.

[0045] During unlocking, the driver needs to start the entire machine and manually press the travel unlock switch. The first solenoid valve is energized, switching to the upper position and connecting the P1 oil port of the valve block to the oil supply port (handle P port) of the travel operating handle, preparing for the handle to control the travel pump. The second solenoid valve is energized, switching to the upper position and connecting the P2 oil port of the valve block to the oil inlet of the hydraulic control directional valve, preparing for the brake unlock oil supply. The third solenoid valve is energized, connecting the P2 oil port of the valve block to the oil supply port (handle P port) of the working handle, preparing for onboard operation. If the travel operating handle is not pushed, the a1 and a2 oil ports are still pressureless, the first shuttle valve has no output, the hydraulic control directional valve remains in the right position, the brake remains locked, and the travel pump, replenishing pump, and DA valve remain in normal operation. The DA valve dynamically adjusts the P1 oil port pressure according to the current engine speed (idle / acceleration), the replenishing pump continuously replenishes leaks, and the system maintains standby pressure.

[0046] When restarting on the ramp, the driver has already manually unlocked the machine and pushes the travel control handle (forward / reverse direction) to start the machine from the ramp parking position. Travel control handle: Under the action of thrust, its C port (or E port, depending on the direction of push) outputs a pressure signal, which is transmitted via the three-way valve to: Control valve assembly a2 port (or a1 port); The pilot control ports of the travel pump are X1 / X2 (or X3 / X4, corresponding to the forward / reverse direction).

[0047] When the first shuttle valve detects the pressure signal at port a1 or a2, it immediately outputs pressure to the external control port of the hydraulic directional valve, overcoming the spring force to push the valve core to switch.

[0048] When the hydraulic directional valve switches to the left position, at this time: Oil circuits for the P2 port of the control valve block, the second solenoid switch valve, the hydraulic directional valve, and the D port of the control valve group; By disconnecting port D from the return oil circuit, pressurized oil can smoothly enter the brake.

[0049] When the brake is unlocked, the D port of the control valve group synchronously delivers pressurized oil to the Z port (brake control oil port) of the two travel motors through the three-way valve. The pressurized oil overcomes the internal spring force of the brake, pushes the brake piston to release, unlocks the output shaft of the travel motor, and allows the motor to rotate.

[0050] The pilot control ports X1 / X2 / X3 / X4 of the travel pump receive the pressure signal transmitted by the handle and drive the two variable control pistons to perform reciprocating stroke adjustment. The variable control piston changes the swashplate angle of the travel pump, causing the travel pump to output hydraulic oil in the corresponding direction (forward / backward) and amount, which is then delivered to the travel motor through the main oil circuit.

[0051] When the travel motor is running, high-pressure oil enters the travel motor, driving the motor rotor to rotate. This, in turn, drives the wheels of the entire machine to rotate through the transmission mechanism, enabling hill start. Leaking oil from the travel motor is discharged to the oil tank through port L to prevent internal accumulation.

[0052] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An automatic parking hydraulic system for a skid steer loader, characterized in that: Includes a travel operation handle (1), a working handle (2), a control valve group (3), at least two travel motors (4), brakes (5) corresponding to each travel motor (4), an engine (6), and a travel pump (7) and an oil tank (8) driven by the engine (6). The walking operation handle (1) has four shuttle valves and a walking control rocker. The four shuttle valves are connected to the control valve group (3) and the walking pump (7) through four signal oil ports C, D, E and F respectively. Ports C and E are connected to ports a2 and a1 of the control valve group (3) respectively. The oil circuit of the control rocker is connected to port C of the control valve group (3) through port P on the walking operation handle (1). The control valve group (3) is equipped with a first shuttle valve (31) with its two ends connected to ports a1 and a2 respectively, a hydraulic directional valve (32), a first solenoid switch valve (33) and a second solenoid switch valve. (34) and the third electromagnetic switch valve (35); the first shuttle valve (31) is connected to the external control port of the hydraulic directional valve (32), the first electromagnetic switch valve (33) is connected to the P1 oil port and C port of the control valve group (3) after being energized, the second electromagnetic switch valve (34) is connected to the P2 oil port and D port of the control valve group (3) after being energized, the D port of the control valve group (3) is connected to the oil chamber of the brake (5), the third electromagnetic switch valve (35) is connected to the P2 oil port and E port of the control valve group (3) after being energized, and the E port of the control valve group (3) is connected to the P port of the working handle (2).

2. The automatic parking hydraulic system for a skid steer loader according to claim 1, characterized in that: The hydraulic control directional valve (32) is a spring-reset two-position directional valve. Under normal conditions, it is kept in the right position by the action of the spring and is used to automatically switch to the oil return and pressure relief position when there is no pressure signal.

3. The automatic parking hydraulic system for a skid steer loader according to claim 1, characterized in that: The walking pump (7) has a built-in oil replenishment pump (71) and DA valve (72). The oil inlet of the oil replenishment pump (71) is connected to the oil tank (8), and the oil outlet is connected to the oil inlet of the DA valve (72).

4. The automatic parking hydraulic system for a skid steer loader according to claim 3, characterized in that: The oil outlet of the DA valve (72) is connected to the P1 oil port of the control valve group (3) and is used to output a pressure signal of the corresponding magnitude to the P1 oil port according to the speed of the engine (6); the G oil port of the travel pump (7) is connected to the P2 oil port of the control valve group (3) and provides pressure oil to the second electromagnetic switch valve (34) and the third electromagnetic switch valve (35).

5. The automatic parking hydraulic system for a skid steer loader according to claim 1, characterized in that: The walking pump (7) is equipped with two variable control pistons (73). The pilot control ports X1, X2, X3, and X4 of the walking pump (7) are connected to the two variable control pistons (73) respectively. They are used to receive the pressure signal transmitted by the walking operation handle (1). By adjusting the stroke of the variable control pistons (73), the direction and magnitude of the output flow of the walking pump (7) are controlled, thereby driving the two walking motors (4) to move.

6. The automatic parking hydraulic system for a skid steer loader according to claim 1, characterized in that: The oil chambers of the brakes (5) corresponding to each walking motor (4) are connected to the D port of the control valve group (3) after being integrated through a three-way valve; the L port of the walking motor (4) is connected to the oil tank (8) to discharge the leaked oil generated during the operation of the motor.

7. The automatic parking hydraulic system for a skid steer loader according to claim 1, characterized in that: The T port of the walking operation handle (1), the T port of the working handle (2) and the T port of the control valve group (3) are all connected to the oil tank (8) to form a unified oil return circuit for the system, ensuring smooth oil return for each component.

Images