Load-sensitive variable pump starting anti-impact loop

Abstract

The invention discloses a load-sensitive variable pump starting anti-impact loop which comprises a first hydraulic control reversing valve and a hydraulic control adjusting unit, an inlet of the first hydraulic control reversing valve is connected with output of a load-sensitive variable pump, and the hydraulic control adjusting unit is arranged at the inlet of the first hydraulic control reversing valve. The inlet pressure of the first hydraulic control reversing valve is led to a control port of the first hydraulic control reversing valve through the hydraulic control adjusting unit, a valve port of the first hydraulic control reversing valve is driven to tend to be closed, the pressure building speed of the control port of the first hydraulic control reversing valve is controlled through the hydraulic control adjusting unit, and then the closing speed of the valve port of the first hydraulic control reversing valve is controlled. The bypass is arranged at the outlet of the load-sensitive variable pump, large flow output after the pump is started returns oil through the bypass, the valve port of the bypass is controlled in a hydraulic control mode to gradually close the bypass, and therefore pressure impact can be reduced to a certain degree. Meanwhile, the closing speed of the bypass is controlled in a hydraulic control mode, and compared with electric control, the hydraulic control mode is simple in structure, low in cost and easy to achieve.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic devices, and in particular to a control circuit capable of eliminating the starting impact of a load-sensitive variable displacement pump. Background Art

[0002] One of the advantages of a load-sensitive variable displacement pump is that it can achieve low-pressure, low-flow standby. At this time, the pump outlet is closed and the load feedback port is connected back to the oil tank. After the pump starts from a standstill, it first outputs the flow at the maximum displacement. When the outlet pressure rises to the set pressure of the pump load-sensitive valve, the pump displacement decreases and enters a low-pressure, low-flow standby state. In this process, since the pipeline cavity of the closed outlet is generally small, a large flow flows into a limited closed space, which will cause a rapid rise in pressure. Before the pump displacement is reduced, a high pressure shock is formed, which will damage components and pipelines and reduce system reliability.

[0003] Therefore, how to eliminate the pressure shock generated when the load-sensitive variable displacement pump is started is a problem to be solved in the art. Summary of the invention

[0004] In view of the technical problem that the existing load-sensitive variable pump has a large impact pressure when starting, which affects the reliability of the system, the purpose of the present invention is to provide a load-sensitive variable pump starting anti-shock circuit, which has a simple structure, low cost and is easy to implement. It can eliminate the pressure shock at the moment of starting the load-sensitive variable pump and improve the reliability of the system.

[0005] In order to achieve the above-mentioned object, the present invention provides a load-sensitive variable pump start-up anti-shock circuit, including a first hydraulically controlled reversing valve and a hydraulically controlled regulating unit, wherein the inlet of the first hydraulically controlled reversing valve is connected to the output of the load-sensitive variable pump, and the flow output at the maximum displacement after the pump is started first flows back to the oil tank through the first hydraulically controlled reversing valve, the inlet of the first hydraulically controlled reversing valve is connected to the output of the load-sensitive variable pump, and the inlet of the first hydraulically controlled reversing valve is provided with a hydraulically controlled regulating unit, and the inlet pressure of the first hydraulically controlled reversing valve is led to the control port of the first hydraulically controlled reversing valve through the hydraulically controlled regulating unit, driving the first hydraulically controlled reversing valve to close. The hydraulically controlled regulating unit is used to control the pressure building speed of the control port of the first hydraulically controlled reversing valve, thereby controlling the closing speed of the valve port of the first hydraulically controlled reversing valve.

[0006] Furthermore, the hydraulically controlled regulating unit comprises a fixed throttle port and a second hydraulically controlled reversing valve, and the fixed throttle port and the second hydraulically controlled reversing valve are connected in series to form a B-type half-bridge.

[0007] Furthermore, the inlet of the B-type half-bridge is connected to the oil inlet of the first hydraulically controlled reversing valve, and the pressure dividing point is connected to the control port of the first hydraulically controlled reversing valve and the control port of the second hydraulically controlled reversing valve.

[0008] Furthermore, due to the effect of the B-type half-bridge pressure division, the pressure at the control port of the first hydraulically controlled reversing valve is lower than its inlet pressure.

[0009] Furthermore, the pressure at the pressure dividing point increases as the opening of the second hydraulically controlled reversing valve port decreases, that is, the difference between the control port pressure of the first hydraulically controlled reversing valve and the inlet pressure decreases, and then the valve port of the first hydraulically controlled reversing valve is gradually closed.

[0010] Furthermore, the preload force of the return springs of the first hydraulically controlled reversing valve and the second hydraulically controlled reversing valve can adjust or change the return spring stiffness to adapt to the pressure loss caused by different variable pump flows passing through the hydraulically controlled reversing valve.

[0011] The load-sensitive variable pump starting anti-shock circuit provided by the present invention sets a bypass at the outlet of the load-sensitive variable pump. After the pump is started, the large flow output first returns oil through the bypass, and then the bypass is gradually closed, thereby reducing pressure shock to a certain extent.

[0012] In addition, this solution uses a hydraulically controlled reversing valve as a variable throttle, which is connected in series with a fixed throttle to form a hydraulic control method of a B-type half-bridge to control the speed of the bypass closing. Compared with electronic control, it has a simple structure and low cost and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0014] Figure 1 This is a schematic diagram of the structure of the load-sensitive variable pump starting anti-shock circuit.

[0015] The following is a description of the components in the accompanying drawings:

[0016] 1. Load sensitive variable pump 2. First hydraulic control reversing valve 3. Fixed throttle 4. Second hydraulic control reversing valve DETAILED DESCRIPTION

[0017] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below with reference to specific diagrams.

[0018] There will be a high pressure shock when the existing load-sensitive variable pump is started. To address this technical problem, the present invention provides a load-sensitive variable pump starting control circuit, which sets a bypass at the outlet of the load-sensitive variable pump. After the pump is started, the large flow output is first returned to the oil through the bypass, and then the bypass is gradually closed. In this way, the pressure shock can be reduced to a certain extent.

[0019] In addition, the present invention adopts a hydraulic control method for gradually closing the bypass, which has a simple structure, low cost and is easy to implement compared to electric control.

[0020] The load-sensitive variable pump start-up control circuit provided by the present invention is shown in FIG. Figure 1 It includes a bypass unit and a hydraulic control regulating unit. When the load-sensitive variable pump 1 is started, the large flow output is first returned through the bypass unit, and then the bypass unit is controlled by the hydraulic control regulating unit to be gradually closed to avoid the pressure shock at the moment of starting the load-sensitive pump 1.

[0021] The bypass unit is the first hydraulically controlled reversing valve 2, which is a large-diameter reversing valve. The pressure at the control port of the first hydraulically controlled reversing valve 2 overcomes the force of the return spring, pushes the valve core to move, and the valve port tends to close. By adjusting the pressure at the control port of the first hydraulically controlled reversing valve 2, the size of the valve port opening can be controlled, that is, the greater the pressure at the control port, the smaller the valve port opening.

[0022] The inlet of the first hydraulically controlled reversing valve 2 is connected to the output of the load-sensing variable pump 1. The flow outputted by the load-sensing variable pump 1 at the maximum displacement first flows back to the oil tank through the first hydraulically controlled reversing valve 2. Due to the pressure loss of the first hydraulically controlled reversing valve 2, a certain pressure will be established at its oil inlet.

[0023] A branch is provided at the inlet of the first hydraulically controlled reversing valve 2 to connect the control port of the first hydraulically controlled reversing valve 2, and the inlet pressure of the first hydraulically controlled reversing valve 2 is led to the control port. The pressure at the control port of the first hydraulically controlled reversing valve 2 overcomes the force of the reset spring, pushes the valve core to move, and the valve port tends to close. As the valve port is reduced, the pressure loss increases, the inlet pressure increases, and the control port pressure also increases, further reducing the valve port until the valve port is closed. This process may be completed quickly, but it will still cause pressure shock. The pressure shock can be reduced or avoided by slowing down the rising speed of the control port pressure, thereby slowing down the closing speed of the valve port.

[0024] Therefore, in addition to the bypass unit, this solution is also equipped with a hydraulic control regulating unit, which can slow down the speed of closing the valve port by slowing down the rising speed of the control port pressure, thereby reducing or avoiding pressure shock.

[0025] The hydraulic control regulating unit includes a fixed throttle port 3 and a second hydraulic control reversing valve 4. The second hydraulic control reversing valve 4 is a reversing valve with a small diameter. The fixed throttle port 3 and the second hydraulic control reversing valve 4 form a B-type half-bridge. The inlet of the B-type half-bridge (point A in the figure) is connected to the oil inlet of the first hydraulic control reversing valve 2, and the pressure dividing point (point B in the figure) is connected to the control port of the first hydraulic control reversing valve 2 and the control port of the second hydraulic control reversing valve 4.

[0026] Due to the pressure-dividing effect of the B-type half-bridge, the pressure at the control port of the first hydraulically controlled reversing valve 2 is lower than the pressure at the inlet. The pressure at the pressure-dividing point B pushes the valve port openings of the first hydraulically controlled reversing valve 2 and the second hydraulically controlled reversing valve 4 to decrease.

[0027] As the second hydraulically controlled reversing valve 4 gradually closes, the half-bridge pressure-dividing effect gradually decreases, and the pressure at the pressure-dividing point B gradually increases. At this time, the pressure difference between the control port of the first hydraulically controlled reversing valve 2 and the inlet pressure gradually decreases, and then the opening of the first hydraulically controlled reversing valve 2 gradually decreases.

[0028] By adjusting the return spring, the valve port of the hydraulically controlled reversing valve 4 is closed earlier than the valve port of the hydraulically controlled reversing valve 2. When the opening of the second hydraulically controlled reversing valve 4 is completely closed, the pressure dividing effect stops, and the pressure at the control port of the first reversing valve 2 is equal to the inlet pressure. This process slows down the closing speed of the first hydraulically controlled reversing valve 2 to avoid pressure shock.

[0029] Finally, the preload force and stiffness of the return springs of the hydraulically controlled reversing valve 2 and the reversing valve 4 can be adjusted to adapt to the pressure loss caused by different variable pump flows passing through the hydraulically controlled reversing valve.

[0030] Based on the load-sensitive variable pump start control loop formed by the above scheme, the following example illustrates its working principle in specific applications. The specific working principle is as follows:

[0031] After the load-sensitive variable pump 1 is started, the flow output at the maximum displacement first flows back to the oil tank through the first hydraulically controlled reversing valve 2, and the pressure-dividing effect of the B-type half-bridge composed of the fixed throttle 3 and the second hydraulically controlled reversing valve 4 slows down the pressure rise speed of the control port of the first hydraulically controlled reversing valve 2, and gradually closes the first hydraulically controlled reversing valve 2 until it is completely closed, avoiding pressure shock.

[0032] Specifically, when the load-sensitive variable pump 1 is started, a certain pressure will be established at the oil inlet of the first hydraulically controlled reversing valve 2 due to the pressure loss of the output flow of the load-sensitive variable pump 1 through the first hydraulically controlled reversing valve 2. The pressure is led to the pressure dividing point B of the B-type half-bridge through the inlet point A of the B-type half-bridge. The pressure dividing point B connects the control port of the first hydraulically controlled reversing valve 2 and the control port of the second hydraulically controlled reversing valve 4. The pressure of the control port overcomes the hydraulically controlled reversing valve return spring force, pushes the valve core to move, and the valve ports of the hydraulically controlled reversing valve 2 and the hydraulically controlled reversing valve 4 tend to close.

[0033] At this time, the pressure at the control port of the first hydraulically controlled reversing valve 2 is lower than its inlet pressure. When the valve port of the second hydraulically controlled reversing valve 4 is gradually closed, the half-bridge pressure-dividing effect is gradually reduced, that is, the difference between the control port pressure and the inlet pressure is reduced, and the valve port of the first hydraulically controlled reversing valve 2 is gradually closed.

[0034] By adjusting the return spring, the valve port of hydraulically controlled reversing valve 4 is closed earlier than the valve port of hydraulically controlled reversing valve 2. When the second hydraulically controlled reversing valve 4 is completely closed, the pressure dividing effect stops, the control port pressure of the first hydraulically controlled reversing valve 2 is equal to the inlet pressure, and the first hydraulically controlled reversing valve 2 is completely closed.

[0035] The load-sensitive variable pump starting anti-shock circuit formed by the above scheme can reduce pressure shock to a certain extent.

[0036] In this scheme, the pressure of the control port of the hydraulically controlled reversing valve is drawn from the oil inlet. The hydraulically controlled reversing valve is used as a variable throttle port, which is connected in series with the fixed throttle port to form a B-type half-bridge. By gradually closing the variable throttle port, the pressure-dividing effect of the B-type half-bridge gradually weakens, slowing down the pressure rise speed of the bypass valve control port, thereby slowing down the speed of bypass closing. Compared with electronic control, this scheme has a simple structure, low cost, and is easy to implement.

[0037] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A load-sensitive variable pump starting anti-shock circuit, characterized in that: It includes a first hydraulically controlled reversing valve and a hydraulically controlled regulating unit. The inlet of the first hydraulically controlled reversing valve is connected to the output of a load-sensitive variable pump. After the pump is started, the flow output at the maximum displacement first flows back to the oil tank through the first hydraulically controlled reversing valve. The inlet of the first hydraulically controlled reversing valve is connected to the output of the load-sensitive variable pump. The inlet of the first hydraulically controlled reversing valve is provided with a hydraulically controlled regulating unit. The inlet pressure of the first hydraulically controlled reversing valve is led to the control port of the first hydraulically controlled reversing valve through the hydraulically controlled regulating unit, driving the first hydraulically controlled reversing valve to close. The pressure building speed of the control port of the first hydraulically controlled reversing valve is controlled by the hydraulically controlled regulating unit, thereby controlling the closing speed of the valve port of the first hydraulically controlled reversing valve.

2. A load-sensing variable pump starting anti-shock circuit according to claim 1, characterized in that: The hydraulic control regulating unit comprises a fixed throttle port and a second hydraulic control reversing valve, wherein the fixed throttle port and the second hydraulic control reversing valve are connected in series to form a B-type half bridge.

3. A load-sensing variable pump starting anti-shock circuit according to claim 2, characterized in that: The inlet of the B-type half-bridge is connected to the oil inlet of the first hydraulically controlled reversing valve, and the pressure dividing point is connected to the control port of the first hydraulically controlled reversing valve and the control port of the second hydraulically controlled reversing valve.

4. A load-sensing variable pump starting anti-shock circuit according to claim 3, characterized in that: The B-type half-bridge pressure divider makes the pressure at the control port of the first hydraulically controlled reversing valve lower than its inlet pressure.

5. A load-sensing variable pump startup anti-shock circuit according to claim 4, characterized in that: The pressure at the pressure dividing point increases as the opening of the second hydraulically controlled reversing valve port decreases, that is, the difference between the control port pressure of the first hydraulically controlled reversing valve and the inlet pressure decreases, and then the valve port of the first hydraulically controlled reversing valve gradually closes.

6. A load-sensing variable pump startup anti-shock circuit according to claim 5, characterized in that: The preload force of the return springs of the first hydraulically controlled reversing valve and the second hydraulically controlled reversing valve can be adjusted or the return spring stiffness can be changed to adapt to the pressure loss caused by different variable pump flows passing through the hydraulically controlled reversing valve.

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