A wheeled hydraulic excavator walking auxiliary braking system

Abstract

The present invention discloses a walking auxiliary braking system for a wheeled hydraulic excavator, which includes a motor, an oil inlet and outlet circuit, and a control oil circuit. A throttle valve is installed on the oil outlet circuit of the motor, and when braking is required, the flow rate of the oil outlet of the motor is restricted through the throttle valve. By applying this control system, the potential energy of the vehicle from the top to the bottom of the slope during downhill can be converted into heat energy by the walking motor, and the heat is carried to the radiator through the hydraulic oil. After the potential energy of the vehicle is converted into heat energy and taken away by the hydraulic oil, it is avoided that the temperature of the brake drum is too high due to long-term operation of the service brake, and the problem of brake failure caused by serious heating of the brake drum due to long-term action is solved.

Description

Technical Field

[0001] The present invention relates to a control system for a hydraulic motor. Background Art

[0002] The prominent problem of the brake overheating and failing when a wheeled hydraulic excavator goes down a long slope: When going down a long slope, the hydraulic system cannot participate in braking (equivalent to driving a car in neutral when going downhill), and the only way to control the vehicle speed is to rely on the drum brake, air resistance, and rolling resistance. When the slope is relatively large (such as 10%) and the slope length is long (such as 2 km or longer), in order to control the vehicle speed within a controllable range, it is inevitable to operate the running brake for a long time to reduce the vehicle speed. Due to the friction between the shoe block and the brake drum under the braking force, the temperature of the brake drum continues to rise. As the temperature of the brake drum rises (up to more than 800 °C at most), the braking efficiency gradually decreases, and in severe cases, it fails, affecting personal and property safety. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: Aiming at the problem of overheating and failure of the drum brake when a wheeled hydraulic excavator goes down a long slope, a walking auxiliary braking system for a wheeled hydraulic excavator is designed.

[0004] The technical solution of the present invention is:

[0005] A walking auxiliary braking system for a wheeled hydraulic excavator, comprising a motor, an oil inlet and outlet circuit, and a control oil circuit, characterized in that: a throttle valve is installed on the oil outlet circuit of the motor, and when braking is required, the flow rate of the oil outlet of the motor is restricted through the throttle valve.

[0006] There are two oil circuits in parallel, namely a main oil circuit and an overflow oil circuit, in the valve body of the throttle valve. A main throttle valve is installed in the main oil circuit, and an overflow valve is installed in the overflow oil circuit. When braking, the flow rate of the main oil circuit is restricted through the main throttle valve. When the inlet oil pressure reaches a certain threshold value, the overflow valve opens the overflow oil circuit under the action of the oil pressure.

[0007] The movement of the main throttle valve is controlled by a throttle check valve. The throttle check valve is connected to the control oil circuit of the motor, and after the control oil pressure is input from the throttle check valve, it pushes the spool of the main throttle valve.

[0008] The control oil circuit starts from a pilot pump, and then is respectively connected to a reversing valve and a control valve through different outlets of a walking pilot / brake valve. The reversing valve is connected to a main control valve, the main control valve is installed between the motor and the main pump, and the control valve is connected to the throttle check valve.

[0009] The other end of the spool of the main throttle valve is installed through a return spring. When there is no oil pressure input from the throttle check valve, the return spring pushes the spool of the main throttle valve back.

[0010] A shuttle valve is arranged between the control valve and the throttle check valve. One outlet of the travel pilot / brake valve and the outlet of the control valve are respectively connected to one inlet of the shuttle valve, and the outlet of the shuttle valve is connected to the throttle check valve.

[0011] During powered driving, the control oil pressure of the pilot pump enters the reversing valve and the main control valve through the travel pilot / brake valve. The main pump supplies oil to the motor, the main throttle valve of the throttle valve opens, and the motor returns oil normally.

[0012] During non-powered driving, the control oil pressure of the pilot pump enters the control valve through the travel pilot / brake valve, and then enters the throttle valve through the shuttle valve and the throttle check valve to push the main throttle valve spool, restricting the oil return of the motor return oil circuit.

[0013] During active braking, the control oil pressure of the travel pilot / brake valve enters the throttle valve through the shuttle valve and the throttle check valve to push the main throttle valve spool, restricting the oil return of the motor return oil circuit.

[0014] The main oil circuit consists of an inlet section, an outlet section, and a throttle section. A supplementary oil circuit connecting the outlet and inlet sections of the main oil circuit is provided, and a check valve is installed to allow the oil to flow only from the outlet section to the inlet section of the main oil circuit.

[0015] The spool of the main throttle valve is installed in the throttle section. The throttle section consists of an inflow chamber, a throttle chamber, and an outflow chamber. The inflow chamber is connected to the inlet section, the outflow chamber is connected to the outlet section, the throttle chamber communicates with the inflow chamber and the outflow chamber, and the throttle chamber is closed when the spool of the main throttle valve is closed; the overflow oil circuit is connected to the outflow chamber and the inlet section, and the supplementary oil circuit is connected to the inflow chamber and the outlet section.

[0016] The spool of the main throttle valve is in the shape of a stepped shaft. Two rods connect the middle sealing plug and the sealing pistons at both ends. The sealing pistons at both ends are installed in the mounting holes of the valve body and sealed with end covers. A return spring is installed inside one end cover, and a throttle check valve is installed on the other end cover; the return spring is sleeved on the limit screw, and the maximum stroke of the spool of the main throttle valve is adjusted through the limit screw. A throttle groove is provided on the sealing plug in the middle of the spool.

[0017] Throttle braking principle: When the motor is in the pump working condition, the potential energy of the vehicle from the top of the slope to the bottom of the slope is converted into the kinetic energy of the vehicle, and the kinetic energy provides driving power for the motor. Due to the throttling effect at the motor outlet, the oil is in a certain pressure state (the higher the vehicle speed, the greater the pressure), providing a reverse braking torque to force the vehicle to decelerate (it can be understood as reversing uphill). Since the oil generates heat through friction when the vehicle is continuously going downhill or overflowing and sliding, the potential energy of the vehicle from the top of the slope to the bottom of the slope is consumed, keeping the vehicle speed always in a controllable state, and significantly reducing the braking drum load of the service brake, ensuring the safety of the passengers and the vehicle to the greatest extent.

[0018] Advantages of the present invention:

[0019] In this control system, when the vehicle goes downhill, the potential energy from the top to the bottom of the slope is converted into heat energy by the traveling motor, and the heat is carried to the radiator through the hydraulic oil. After the potential energy of the vehicle is converted into heat energy and taken away by the hydraulic oil, it avoids the overheating of the brake drum caused by the long-term operation of the service brake, and solves the problem of brake failure caused by serious overheating of the brake drum due to long-term action. Description of the Drawings

[0020] Figure 1 It is the schematic diagram of the hydraulic braking control system.

[0021] Figure 2 It is the schematic diagram of the throttle valve in the traveling state.

[0022] Figure 3 It is the schematic diagram of the throttle valve in the braking state.

[0023] Figure 4 It is the schematic diagram of the throttle valve structure. Detailed Implementation Manner

[0024] Example 1:

[0025] In this example, a throttle valve is added to the original hydraulic motor control system. The throttle valve is installed on the oil return circuit of the motor. When traveling normally, the throttle valve is open and does not affect the oil return of the motor to the fuel tank. When deceleration is required, the throttle valve is controlled to close to limit the oil flow in the oil return circuit of the motor. At this time, the pressure at the oil outlet end of the motor rises rapidly, providing a reverse braking torque to the motor, forcing the vehicle to decelerate.

[0026] Furthermore, the throttle valve in this example includes two parallel oil circuits, namely the main oil circuit and the overflow oil circuit. The inlets and outlets of the main oil circuit and the overflow oil circuit are the same. A main throttle valve is installed in the main oil circuit, and an overflow valve is installed in the overflow oil circuit. The flow rate of the main oil circuit is controlled by moving the spool of the main throttle valve. After the throttling starts, the oil pressure at the inlet rises rapidly. When the oil pressure at the inlet reaches a certain threshold value, the overflow valve opens the overflow oil circuit under the action of the oil pressure, controlling the oil pressure difference between the inlet and outlet within a certain range.

[0027] Furthermore, the left end of the spool of the main throttle valve is connected to a return spring, and the right end is installed in the control oil cavity. In the normal state, the spool is pushed open by the return spring and does not affect the flow of the main oil circuit. When the control oil pressure passes through the throttle check valve and enters the control oil cavity, it pushes the spool of the main throttle valve to restrict the cross-section of the main flow path and control the flow rate. After losing the control oil pressure, the spool returns under the action of the return spring.

[0028] Example 2: As Figure 1This is the schematic diagram of the hydraulic braking control system in this embodiment. The dotted lines in the figure represent the control oil circuits, and the solid lines represent the motor power oil circuits. The main working parts of the throttle braking consist of Valve 1 (throttle valve), Valve 2 (control valve), Valve 6 (shuttle valve) and pipelines, but it cannot exist independently and also requires the participation of the main pump, pilot pump, Valve 2 (main control valve), Valve 3 (directional control valve, used when reversing), motor, Valve 4 (travel pilot / brake valve), fuel tank, etc. to complete its application functions. Based on the original hydraulic system of the original wheeled hydraulic excavator, only Valve 1 (throttle valve), Valve 2 (control valve), Valve 6 (shuttle valve) and the corresponding pipelines are added, and the increased cost is not much. The driving / braking operation has no change compared with the original hydraulic system, and the operability is strong. After the use of the wheeled hydraulic excavator travel auxiliary braking system, the driving safety and braking reliability of the whole machine are greatly improved.

[0029] Valve 1 (throttle valve) includes two parallel oil circuits, namely the main oil circuit and the overflow oil circuit. The inlets and outlets of the main oil circuit and the overflow oil circuit are the same. A main throttle valve is installed in the main oil circuit, and an overflow valve is installed in the overflow oil circuit. The flow rate of the main oil circuit is controlled by moving the spool of the main throttle valve. After the throttling starts, the oil pressure at the inlet rises rapidly. When the inlet oil pressure reaches a certain threshold value, the overflow valve opens the overflow oil circuit under the action of the oil pressure, and controls the oil pressure difference between the inlet and outlet within a certain range.

[0030] The left end of the spool of the main throttle valve is connected to a return spring, and the right end is installed in the control oil cavity. Under normal conditions, the spool is pushed open by the return spring and does not affect the flow of the main oil circuit. When the control oil pressure passes through the throttle check valve and enters the control oil cavity, it pushes the spool of the main throttle valve to the closed valve state to restrict the cross-section of the main flow path and control the flow rate. After losing the control oil pressure, the spool returns under the action of the return spring. In the closed valve state, the main flow path is not immediately completely closed. There is a throttle groove on the spool. After the throttle groove and the inner wall surface of the throttle cavity of the main flow path are matched, a throttle channel is formed. As the control oil pressure increases, the spool moves more to the left, and the cross-sectional area of the throttle channel becomes smaller. The throttle valve is installed on the oil return circuit of the motor, and the throttle check valve is connected to the control oil circuit.

[0031] A supplementary oil circuit connecting the inlet and outlet sections of the main oil circuit is set, and a check valve is installed to make the oil fluid flow only from the outlet section of the main oil circuit to the inlet section. If the supplementary oil circuit and the check valve are not set, when reversing, if the foot suddenly releases the pedal and the spool is in the closed valve state, the vehicle dragging the motor to rotate will cause serious cavitation.

[0032] Such as Figure 2, when the wheeled hydraulic excavator is running normally, step on the travel pilot pedal. The control pressure oil pumped out by the pilot pump, as shown by the thick dashed line, first enters the p port of valve four, passes through the travel pilot valve → the directional control valve → and pushes the spool of the main control valve to move left. At this time, the high-pressure hydraulic oil pumped out by the main pump, as shown by the thick solid line, flows from the main pump → the AL1 port of valve two (main control valve) → enters the motor inlet through the pipeline, and then enters valve one (throttle valve) through the motor outlet through the pipeline. The main throttle valve spool of valve one (throttle valve) is in a fully open state, does not throttle the oil outlet of the motor, and does not affect the normal driving function.

[0033] As Figure 3 , when deceleration braking is required, after releasing the travel pedal, valve two (main control valve) returns to the neutral position under the action of the spool spring force, and the motor inlet and return oil cavities are connected to the fuel tank at the same time. At this time, the pressure oil pumped out by the pilot pump, as shown by the thick dashed line, does not pass through valve four, but directly flows out through the p2 port of valve five (control valve) → the S port of valve six (shuttle valve) → and flows to the k port of valve one (throttle valve) through the pipeline. The throttle hole of the throttle check valve in valve one (throttle valve) is flowed through to push the main throttle valve spool to move left, and the oil outlet of the motor is in a throttled state. Since the motor becomes a pump under the drive of the gravity or inertia force of the whole vehicle at this time, the pressure at the oil outlet of the motor will rise rapidly (as shown by the thick solid line in the figure) to the pressure set by the relief valve, and the relief valve opens for overflow. The vehicle speed rapidly decreases under the action of the overflow pressure, the pressure drops, and the relief valve closes. The vehicle slides at a certain speed and continues to slow down slowly until the vehicle speed drops to the expected range when the driver steps on the travel pedal.

[0034] When the driver steps on the brake pedal, at this time, the pressure oil pumped out by the pilot pump enters the p port of valve four → the travel brake valve → the S2 port of valve six (shuttle valve) → and flows to the k port of valve one (throttle valve) through the pipeline. The throttle hole of the throttle check valve in valve one (throttle valve) is flowed through to push the main throttle valve spool to move left, and the oil outlet of the motor is in a throttled state, and the auxiliary braking system brakes.

[0035] Embodiment 3: The control system of this embodiment has the same structure as that of Embodiment 2, except that the structure of valve one (throttle valve) is further improved. The specific structure of valve one is as Figure 4

[0036] As Figure 4 , a check valve 10, a relief valve 7, a main throttle valve 8, and a throttle check valve 12 are installed in the valve body 9 of this throttle valve. There are 4 oil circuits: the main oil circuit, the overflow oil circuit, the makeup oil circuit, and the control oil circuit. The main oil circuit consists of an inlet section, an outlet section, and a throttling section. The throttling section consists of an inflow chamber, a throttling chamber, and an outflow chamber. The inflow chamber is connected to the inlet section, the outflow chamber is connected to the outlet section, the throttling chamber communicates with the inflow chamber and the outflow chamber, and the throttling chamber is closed when the spool of the main throttle valve 8 is closed; the overflow oil circuit is connected to the outflow chamber and the inlet section, and a relief valve 7 is installed. The makeup oil circuit is connected to the inflow chamber and the outlet section, and a check valve 10 is installed.

[0037] The spool of the main throttle valve 8 is in the shape of a stepped shaft. Two rods connect the middle sealing plug and the sealing pistons at both ends. The sealing pistons at both ends are installed in the mounting holes of the valve body 9 and sealed with an end cover 6 and a second end cover 11. A return spring 5, a spring seat 4 and a limit screw 3 are installed inside the end cover 6, and a throttle check valve 12 is installed on the second end cover 11. The position of the limit screw 3 can be adjusted by turning the lock nut 2 to affect the position of the main throttle valve 8, and the position of the main throttle valve 8 affects the flow rate when closing the valve.

[0038] Install the throttle valve on the oil return circuit of the motor and connect the throttle check valve 12 with the pilot control pressure oil. When driving normally, there is no input of pilot control pressure oil. The main throttle valve 8 is in the open valve state under the action of the return spring 5, and the oil discharged from the motor directly flows out from the main oil circuit. When the wheeled hydraulic excavator needs to decelerate from the normal driving state, first slowly release the travel speed control pedal. The pilot control pressure oil in the accumulator is connected to the throttle check valve 12 and enters the control oil circuit, and pushes the spool of the main throttle valve 8 to move leftward to reach Figure 4 the state shown. A throttle groove is provided on the sealing plug in the middle of the spool. After the throttle groove enters the throttle chamber, it cooperates with the inner wall surface to form a throttle passage. As the spool moves leftward, the throttle passage becomes smaller and smaller. In the throttling state, the oil pressure at the inlet section rises rapidly, and the pressure oil at the motor outlet provides a reverse braking torque to the motor, forcing the vehicle to decelerate. When the oil pressure rises to the preset threshold value of the relief valve 7, the relief valve 7 opens, and the pressure oil enters the outlet section from the overflow oil circuit.

[0039] When reversing, if the foot suddenly releases the pedal, at this time the spool of the main throttle valve 8 is in the closed valve state, the vehicle drags the motor to rotate, the oil pressure at the inlet section decreases, and the check valve 10 opens to supply oil to the motor through the make-up oil circuit.

Claims

1. A wheeled hydraulic excavator traveling auxiliary braking system, comprising a motor, an oil inlet and outlet circuit, and a control oil circuit, Characterized in that: A throttle valve is installed on the oil outlet circuit of the motor, and the flow rate of the oil outlet of the motor is restricted by the throttle valve when braking is required; there are two oil circuits in parallel, namely the main oil circuit and the overflow oil circuit, in the valve body of the throttle valve. A main throttle valve is installed in the main oil circuit, and an overflow valve is installed in the overflow oil circuit. When braking, the flow rate of the main oil circuit is restricted by the main throttle valve. When the inlet oil pressure reaches a certain threshold value, the overflow valve opens the overflow oil circuit under the action of the oil pressure.

2. The wheeled hydraulic excavator traveling auxiliary braking system according to claim 1, Characterized in that: The movement of the main throttle valve is controlled by a throttle check valve. The throttle check valve is connected to the control oil circuit of the motor, and the control oil pressure is input from the throttle check valve and then pushes the valve core of the main throttle valve.

3. The wheeled hydraulic excavator traveling auxiliary braking system according to claim 2, Characterized in that: The control oil circuit starts from the pilot pump, and then is respectively connected to a directional control valve and a control valve through different outlets of the traveling pilot / brake valve. The directional control valve is connected to the main control valve. The main control valve is installed between the motor and the main pump, and the control valve is connected to the throttle check valve.

4. The wheeled hydraulic excavator traveling auxiliary braking system according to claim 2, Characterized in that: The other end of the valve core of the main throttle valve is installed through a return spring. When there is no oil pressure input to the throttle check valve, the return spring pushes the valve core of the main throttle valve back.

5. The wheeled hydraulic excavator traveling auxiliary braking system according to claim 2, Characterized in that: A shuttle valve is arranged between the control valve and the throttle check valve. One outlet of the traveling pilot / brake valve and the outlet of the control valve are respectively connected to one inlet of the shuttle valve, and the outlet of the shuttle valve is connected to the throttle check valve.

6. The wheeled hydraulic excavator traveling auxiliary braking system according to claim 5, Characterized in that: During powered travel, the control oil pressure of the pilot pump enters the directional control valve and the main control valve through the traveling pilot / brake valve. The main pump supplies oil to the motor. The main throttle valve of the throttle valve opens, and the motor returns oil normally; During non-powered travel, the control oil pressure of the pilot pump enters the control valve through the traveling pilot / brake valve, and then enters the throttle valve through the shuttle valve and the throttle check valve to push the valve core of the main throttle valve, restricting the oil return of the motor oil return circuit; During active braking, the control oil pressure of the traveling pilot / brake valve enters the throttle valve through the shuttle valve and the throttle check valve to push the valve core of the main throttle valve, restricting the oil return of the motor oil return circuit.

7. The wheeled hydraulic excavator traveling auxiliary braking system according to any one of claims 1-6, Characterized in that: The main oil circuit is composed of an inlet section, an outlet section and a throttling section. A supplementary oil circuit connecting the outlet and inlet sections of the main oil circuit is provided, and a check valve is installed to allow the oil to flow only from the outlet section of the main oil circuit to the inlet section.

8. The wheeled hydraulic excavator traveling auxiliary braking system according to claim 7, Characterized in that: The valve core of the main throttle valve is installed in the throttling section. The throttling section is composed of an inflow chamber, a throttling chamber and an outflow chamber. The inflow chamber is connected to the inlet section, the outflow chamber is connected to the outlet section, the throttling chamber communicates with the inflow chamber and the outflow chamber, and the valve core of the main throttle valve closes to seal the throttling chamber; the overflow oil circuit is connected to the outflow chamber and the inlet section, and the supplementary oil circuit is connected to the inflow chamber and the outlet section.

9. The wheeled hydraulic excavator traveling auxiliary braking system according to claim 8, characterized in that: The spool of the main throttle valve is in the shape of a stepped shaft. Two rods connect the middle sealing plug and the sealing pistons at both ends. The sealing pistons at both ends are installed in the mounting holes of the valve body and sealed with end covers. A return spring is installed inside one end cover, and a throttle check valve is installed on the other end cover; the return spring is sleeved on the limit screw, and the maximum stroke of the spool of the main throttle valve is adjusted through the limit screw. A throttle groove is provided on the sealing plug in the middle of the spool.

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