Loader and constant and variable hydraulic control system thereof

Abstract

The utility model relates to a loader, in particular to a loader and a constant and variable hydraulic control system thereof, which comprises a steering hydraulic system, a working hydraulic system, a control unit and an electromagnetic valve. The steering hydraulic system comprises a flow amplifying valve, a variable pump connected with the flow amplifying valve and a switching valve used for controlling the variable pump to be switched between a quantitative mode and a variable mode. The working hydraulic system comprises a distribution valve, a metering pump connected with the distribution valve and a pilot control device used for controlling the distribution valve. The electromagnetic valve is connected between the hydraulic control end of the switching valve and the pressure oil source; and the control unit is electrically connected with the electromagnetic valve and is configured to control the electromagnetic valve to enable the switching valve to be in a variable mode when the rotating speed of the engine is lower than a preset value. In the utility model, the control unit and the electromagnetic valve are arranged, the variable pump works in a variable mode when the engine is in low-speed operation, the power absorbed and consumed by the hydraulic system is reduced, and the engine is prevented from flameout.

Description

Technical Field

[0001] The utility model relates to a loader, and more particularly to a loader and a constant variable hydraulic control system thereof. Background Art

[0002] The hydraulic system of the loader includes a steering hydraulic system and a working hydraulic system. In the steering hydraulic system, the steering priority oil supply is usually set. When the working device is in motion, the excess flow of the steering hydraulic system is merged into the working hydraulic system.

[0003] The hydraulic system of a loader can be divided into a fully variable hydraulic system, a fixed variable hydraulic system, and a fixed displacement hydraulic system according to the properties of the hydraulic pump. A fixed variable hydraulic system is one in which the hydraulic pump in the steering hydraulic system is a variable displacement pump and the hydraulic pump in the working hydraulic system is a fixed displacement pump.

[0004] In the loader's fixed-variable hydraulic system, the EF port of the priority valve in the flow amplification valve is connected to the oil inlet of the distribution valve in the working hydraulic system, merging with the fixed displacement pump in the working hydraulic system. A control valve is provided to control the displacement of the variable displacement pump in the steering hydraulic system. This control valve is associated with the working hydraulic system. When the working hydraulic system is not in operation, the displacement of the variable displacement pump is automatically adjusted based on the load pressure signal transmitted by the flow amplification valve. When the working hydraulic system is in operation, the control valve switches to operate the variable displacement pump in a constant pressure pump state. The variable displacement pump operates at full displacement, consuming the most power in this state. If the machine is operating in high altitude areas and the engine speed is low, the hydraulic system power may account for too much of the engine power, causing the engine to stall. Utility Model Content

[0005] The technical problem to be solved by the utility model is that the fixed-displacement hydraulic system of a loader may cause engine flameout when operating at full displacement at high altitude and low speed, and provides a loader and a quantitative hydraulic control system thereof.

[0006] The technical solution for achieving the purpose of the utility model is as follows: a fixed variable hydraulic control system for a loader, comprising a steering hydraulic system and a working hydraulic system; the steering hydraulic system comprises a flow amplification valve, a variable displacement pump connected to the flow amplification valve, and a switching valve for controlling the variable displacement pump to switch between a fixed displacement mode and a variable displacement mode; the working hydraulic system comprises a distribution valve, a fixed displacement pump connected to the distribution valve, and a pilot control device for operating the distribution valve; the fixed variable hydraulic control system also comprises a control unit and a solenoid valve;

[0007] The solenoid valve is connected between the hydraulic control end of the switching valve and the pressure oil source;

[0008] The control unit is electrically connected to the solenoid valve and the engine speed detection device, and controls the solenoid valve to put the switching valve in a variable mode when the engine speed is lower than a predetermined value.

[0009] In the utility model, a solenoid valve is controlled by a control unit to control the switching valve. When the engine is running at a low speed (lower than the set speed), the variable pump is operated in a variable mode. In this mode, the flow is output only according to the steering load, thereby avoiding the variable pump of the steering hydraulic system and the working pump of the working hydraulic system from running at full displacement when the hydraulic system operates the working device under the low-speed running state of the engine, thereby avoiding the engine stalling due to excessive power consumption by the hydraulic system.

[0010] In the fixed variable hydraulic control system of the loader of the present invention, it can be that: the pressure oil source includes a shuttle valve group composed of three shuttle valves, and the four oil inlet ends of the shuttle valve group are connected to the four-way pilot control oil circuit of the pilot control device; the solenoid valve is a two-way valve, the oil inlet of which is connected to the oil outlet end of the shuttle valve group, the oil outlet is connected to the hydraulic control end of the switching valve, the oil return port is connected to the hydraulic oil tank, and the oil outlet selects one of the oil inlet and the oil return port to be connected.

[0011] In the fixed variable hydraulic control system of the loader of the present invention, it can also be that: the pressure oil source includes a pilot oil source; the solenoid valve is a two-position three-way valve, the oil inlet of which is connected to the pilot oil source, the oil outlet is connected to the hydraulic control end of the switching valve, the return oil port is connected to the hydraulic oil tank, and the oil outlet is connected to either the oil inlet or the return oil port; the pilot control device is an electronic control device; the control unit is electrically connected to the pilot control device and controls the solenoid valve to put the switching valve in a quantitative mode when the engine speed is higher than a predetermined value and the pilot control device has an operating action.

[0012] In the fixed variable hydraulic control system of the loader of the present invention, the switching valve is a two-position four-way hydraulic control valve, its P2 port is connected to the load signal output port of the flow amplification valve, the P3 port is connected to the pump port of the variable pump, the P4 port is connected to the load signal input port of the variable pump, and the P5 port is connected to the priority valve control port of the flow amplification valve. In the variable mode, the P2 port is connected to the P4 port, and the P3 port and the P5 port are both cut off; in the quantitative mode, the P3 port is connected to the P4 port, and the P2 port is connected to the P5 port.

[0013] In the fixed variable hydraulic control system of the loader of the utility model, each main valve in the distribution valve is set to an open middle position.

[0014] In the fixed variable hydraulic control system of the loader of the utility model, the fixed quantity pump is a gear pump.

[0015] The technical solution for achieving the purpose of the utility model is: a loader having the aforementioned loader quantitative hydraulic control system.

[0016] Compared with the prior art, the present invention provides a control unit and a solenoid valve, and enables the variable pump to operate in a variable mode when the engine is running at a low speed, thereby reducing the power absorbed and consumed by the hydraulic system and preventing the engine from stalling. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a principle diagram of a fixed variable hydraulic control system for a loader of the present utility model.

[0018] Parts names and serial numbers in the figure:

[0019] Hydraulic oil tank 1, metering pump 2, distribution valve 3, boom cylinder 4, bucket cylinder 5, hand pilot valve 6, pilot oil source valve 7, variable pump 8, flow amplification valve 9, steering gear 10, steering cylinder 11, switching valve 12, solenoid valve 13, shuttle valve group 14. DETAILED DESCRIPTION

[0020] The specific implementation scheme is described below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the loader's constant variable hydraulic control system includes a steering hydraulic system and a working hydraulic system.

[0022] The steering hydraulic system includes a flow amplification valve 9, a variable displacement pump 8 connected to the flow amplification valve 9, and a switching valve 12 for controlling the variable displacement pump 8 between fixed and variable displacement modes. The working hydraulic system includes a distribution valve 3, a fixed displacement pump 2 connected to the distribution valve 3, and a pilot control device for controlling the distribution valve 3.

[0023] In the steering hydraulic system, the pump port of variable displacement pump 8 is connected to the oil inlet (port P) of flow amplification valve 9, supplying steering pressure oil to flow amplification valve 9. Steering gear 10 is connected to flow amplification valve 9, controlling the flow amplification valve 9 to deliver steering hydraulic oil to steering cylinder 11. Port EF of the priority valve in flow amplification valve 9 is connected to the oil inlet of distribution valve 3 in the working hydraulic system. This port joins with fixed displacement pump 2 to supply the distribution valve 3 with the pressure oil required to operate the working mechanism.

[0024] In the working hydraulic system, the pump port of the metering pump 2 is connected to the oil inlet of the distribution valve 3. The distribution valve 3 has multiple main valves, such as a boom-connected main valve and a bucket-connected main valve. Each main valve is used to control the corresponding hydraulic actuator in the working device, such as the boom cylinder 4 and the bucket cylinder 5.

[0025] Switching valve 12 is a two-position, four-way hydraulically controlled valve. Its port P2 is connected to the load signal output port (LS) of flow amplifier valve 9, port P3 is connected to the pump port of variable pump 8, port P4 is connected to the load signal input port (X1) of variable pump 8, and port P5 is connected to the priority valve control port (LS1) of flow amplifier valve 9. In variable mode, ports P2 and P4 are connected, while ports P3 and P5 are blocked. In fixed-flow mode, ports P3 and P4 are connected, while ports P2 and P5 are connected. In fixed-flow mode, pilot pressure oil is applied to the hydraulic control port of switching valve 12. Switching valve 12 is in the right position under the influence of the hydraulic pressure oil. The pump port of variable pump 8 is directly connected through ports P3 and P4 of switching valve 12, causing variable pump 8 to operate in constant pressure pump mode, at which point its displacement reaches maximum. In the variable mode, no pressure oil is charged into the hydraulic control end of the switching valve 12, the switching valve 12 is in the left position, the P2 port and the P4 port are connected, and the P3 port and the P5 port are both cut off. At this time, the load signal of the flow amplification valve 9 is transmitted to the load signal input port of the variable pump 8 through the P2 port and the P4 port of the switching valve 12, and the variable pump 8 provides the required flow according to the steering load.

[0026] The loader's fixed-variable hydraulic control system also includes a control unit and a solenoid valve 13. The solenoid valve 13 is connected between the hydraulic control end of the switching valve 12 and the pressure oil source. A control unit (not shown) is electrically connected to the solenoid valve 13 and an engine speed detection device. It is configured to control the solenoid valve 13 to put the switching valve 12 into a variable speed mode when the engine speed falls below a predetermined value. The engine speed detection device can be an engine speed sensor or an engine control unit (ECU), which can detect or obtain engine speed parameter data.

[0027] In this embodiment, a solenoid valve 13 controlled by a control unit is provided to control the switching valve 12. When the engine is running at low speed (below a set speed), the variable pump 8 operates in variable mode, in which the output flow rate is determined solely by the steering load. At this time, if the working device is being operated simultaneously, such as the boom cylinder 4 extending and retracting and / or the bucket 5 extending and retracting, the switching valve 12 remains in the left position, and the variable pump 8 operates in variable pump mode. This solution prevents the variable pump 8 of the steering hydraulic system and the working pump 2 of the working hydraulic system from operating at full displacement when the working device is being operated at low engine speed, thereby preventing the hydraulic system from absorbing and consuming excessive power, which could cause the engine to stall.

[0028] The control unit is associated with the engine speed, which may be a whole machine controller, which obtains the engine speed through a speed sensor or an engine control unit, and outputs a control current to the solenoid valve 13 depending on whether the engine speed is greater than a predetermined value.

[0029] Alternatively, as Figure 1As shown, the pressure oil source includes a shuttle valve group 14 consisting of three shuttle valves. The four oil inlet ends of the shuttle valve group 14 are connected to the four-way pilot control oil circuit of the pilot control device. The solenoid valve 13 is a two-way three-way valve, whose oil inlet is connected to the oil outlet end of the shuttle valve group 14, the oil outlet is connected to the hydraulic control end of the switching valve 12, and the oil return port is connected to the hydraulic oil tank 1; one of the oil outlets is connected to the oil inlet or the oil return port.

[0030] The pilot control device can be a manual pilot valve 6. Its four pilot control oil circuits are connected to the hydraulically controlled ports of the boom and bucket main valves in the distribution valve 3, respectively, to control the extension and retraction of the boom and bucket cylinders 4 and 5. The four oil inlets of the shuttle valve assembly 14 are connected to the four pilot control oil circuits of the manual pilot valve 6. When the boom and bucket cylinders 4 and 5 are extended or retracted, the manual pilot valve 6 outputs pilot pressure oil to one or two of its four pilot control oil circuits. This pilot pressure oil is then compared by the shuttle valves in the shuttle valve assembly 14 and output from the oil outlet of the shuttle valve assembly 14. At this time, if the engine speed is higher than a predetermined value, the control unit controls solenoid valve 13 to be energized, and solenoid valve 13 is in a state of conduction between the oil inlet and oil outlet. The working device actuation signal output by shuttle valve group 14 is transmitted to the hydraulic control end of switching valve 12, causing switching valve 12 to operate in fixed-displacement mode. The variable pump 8 and fixed-displacement pump 2 combine to supply oil to the hydraulic actuator of the working device. If the engine speed is lower than a predetermined value when the working device is operating, the control unit controls solenoid valve 13 to be de-energized, and the oil outlet of solenoid valve 13 is connected to the oil return port. No pressurized oil is supplied to the hydraulic control end of switching valve 12, and switching valve 12 operates in the left position, in variable displacement mode. The displacement of the variable pump 8 is only related to the steering load signal transmitted by flow amplifier valve 9. The displacement of variable pump 8 is small and is not in full displacement mode, thereby reducing the power consumed by the hydraulic system at this time and preventing engine stall.

[0031] If the pilot control device has no operation action, the manual pilot valve 6 will not output the pilot pressure oil, and the hydraulic control end of the switching valve has no pressure oil input, so the switching valve 12 works in the left position and the variable pump 8 works in the variable mode.

[0032] In this embodiment, the pressure oil source may also include a pilot oil source. The solenoid valve 13 is a two-position, three-way valve, with its oil inlet connected to the pilot oil source, its oil outlet connected to the hydraulic control end of the switching valve 12, and its oil return port connected to the hydraulic oil tank. The control unit is configured to control the solenoid valve 13 to place the switching valve 12 in a fixed-flow mode when the engine speed exceeds a predetermined value and the pilot control device is operating. In this embodiment, the pilot control device is an electronically controlled device comprising a controller and an electronic control handle electrically connected to the controller. Each main valve in the distribution valve 3 is an electronically controlled valve, and each main valve has an electric proportional valve electrically connected to the controller at its control end, or each main valve has its valve stem connected to an electromagnet at both ends. The controller controls the electric proportional valve or the electromagnet at the end of the valve stem based on the electrical signal output by the electronic control handle, thereby controlling the corresponding main valve in the distribution valve 3. The control unit can determine whether the pilot control device is operating based on the electrical signal output by the electronic control handle to the controller. If the pilot control device is operated and the engine speed is higher than a predetermined value, the control unit controls the solenoid valve 13 to be energized to connect the oil inlet and oil outlet, the switching valve 12 is in the right position, and the variable pump 8 operates in the fixed displacement pump mode. If the pilot control device is not operated, the control unit controls the solenoid valve 13 to be de-energized to connect the oil outlet and oil return port, the switching valve 12 is in the left position, and the variable pump 8 operates in the variable displacement pump mode.

[0033] The pilot oil source can be a pilot oil supply valve 7, such as Figure 1 As shown, its oil inlet is connected to the pump port of the variable displacement pump 8. The high-pressure working oil output by the variable displacement pump 8 is reduced in pressure and then output from its oil outlet to provide control pressure oil to the manual pilot valve 6 or the control oil circuit. The pilot oil source can also be a pilot pump that provides control pressure oil to the hydraulic system control oil circuit.

[0034] In this embodiment, the main valves of each link in the distribution valve 3 are set to the open center position, and the metering pump 2 is a gear pump. The main valves of each link in the distribution valve 3 are set to the open center position. That is, when the main valves of each link are in the center position, the working oil inlet of the main valve is connected to the oil return port. When all the main valves of each link are in the center position, the oil inlet of the multi-way valve is connected to the oil inlet, and the multi-way valve can unload the working metering pump.

[0035] This embodiment also provides a loader having the aforementioned loader quantitative hydraulic control system.

[0036] In the present invention, a control unit and a solenoid valve 13 are provided to enable the variable displacement pump to operate in a variable displacement mode when the engine is running at a low speed, thereby reducing the power absorbed and consumed by the hydraulic system and preventing the engine from stalling.

Claims

1. A fixed-variable hydraulic control system for a loader, comprising a steering hydraulic system and a working hydraulic system; the steering hydraulic system comprising a flow amplification valve, a variable displacement pump connected to the flow amplification valve, and a switching valve for controlling the variable displacement pump to switch between a fixed displacement mode and a variable displacement mode; the working hydraulic system comprising a distribution valve, a fixed displacement pump connected to the distribution valve, and a pilot control device for operating the distribution valve; characterized in that: It also includes a control unit and a solenoid valve; The solenoid valve is connected between the hydraulic control end of the switching valve and the pressure oil source; The control unit is electrically connected to the solenoid valve and the engine speed detection device and controls the solenoid valve to put the switching valve into a variable mode when the engine speed is lower than a predetermined value.

2. The loader constant variable hydraulic control system according to claim 1, characterized in that: The pressure oil source includes a shuttle valve group consisting of three shuttle valves, and the four oil inlet ends of the shuttle valve group are connected to the four-way pilot control oil circuits of the pilot control device; The solenoid valve is a two-way three-way valve, whose oil inlet is connected to the oil outlet end of the shuttle valve group, the oil outlet is connected to the hydraulic control end of the switching valve, the oil return port is connected to the hydraulic oil tank, and one of the oil outlets is connected to the oil inlet or the oil return port.

3. The loader constant variable hydraulic control system according to claim 1, characterized in that: The pressure oil source includes a pilot oil source; The solenoid valve is a two-position three-way valve, the oil inlet of which is connected to the pilot oil source, the oil outlet is connected to the hydraulic control end of the switching valve, the oil return port is connected to the hydraulic oil tank, and the oil outlet is selectively connected to the oil inlet or the oil return port; The pilot control device is an electronic control device; the control unit is electrically connected to the pilot control device and controls the solenoid valve to put the switching valve in a quantitative mode when the engine speed is higher than a predetermined value and the pilot control device has an operating action.

4. The loader constant variable hydraulic control system according to any one of claims 1 to 3, characterized in that: The switching valve is a two-position four-way hydraulically controlled valve, whose P2 port is connected to the load signal output port of the flow amplification valve, the P3 port is connected to the pump port of the variable pump, the P4 port is connected to the load signal input port of the variable pump, and the P5 port is connected to the priority valve control port of the flow amplification valve. In the variable mode, the P2 port and the P4 port are connected, and the P3 port and the P5 port are both cut off; in the quantitative mode, the P3 port and the P4 port are connected, and the P2 port and the P5 port are connected.

5. The loader constant variable hydraulic control system according to any one of claims 1 to 3, characterized in that: Each main valve in the distribution valve is set to an open center position.

6. The loader constant variable hydraulic control system according to any one of claims 1 to 3, characterized in that: The metering pump is a gear pump.

7. A loader, characterized in that: A loader fixed variable hydraulic control system according to any one of claims 1 to 6.

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