Hydraulic system

Abstract

To provide a hydraulic system capable of suppressing the occurrence of a surge pressure in a pressure reducing valve.SOLUTION: A hydraulic system includes a hydraulic pump 104, switching valves 140, 142, 144 for supplying hydraulic pressure to an actuator, a plurality of solenoid valves SOL1, SOL2 arranged in parallel between the hydraulic pump 104 and the switching valves, an accumulator 120 connected to a primary side pipeline 110, and pressure switches PS1, PS2 connected to a secondary side pipeline 130. The plurality of solenoid valves SOL1, SOL2 different in closing set pressure are stepwise closed as a pressure in the secondary side pipeline 130 rises toward a rating pressure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hydraulic system that supplies hydraulic oil discharged from a hydraulic pump to an actuator.

Background Art

[0002] Conventionally, a hydraulic system that supplies hydraulic oil discharged from a hydraulic pump to an actuator has been known. In particular, a hydraulic system that uses an accumulator and a pressure reducing valve to stabilize the hydraulic pressure even when the hydraulic cylinder of the actuator operates and suppress the capacity of the hydraulic pump has been known.

[0003] Patent Document 1 (Patent No. 5782483) discloses a hydraulic pump connected to a primary side pipeline, an accumulator connected to a primary circuit and storing the hydraulic oil discharged from the hydraulic pump, a primary side pipeline for introducing the hydraulic oil from the accumulator, and a secondary side pipeline for discharging the introduced hydraulic oil toward the actuator. The secondary side pipeline is connected to each of the pipelines, and a non-leak type pressure reducing valve for adjusting the pressure of the hydraulic oil in the secondary side pipeline to a pressure lower than that of the primary side pipeline is provided. The secondary side pipeline is connected to the primary side pipeline only through the non-leak type pressure reducing valve, and the hydraulic pump is connected to the actuator only through the secondary pipeline. A hydraulic unit is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in Patent Document 1, the hydraulic pump side of the non-leak type pressure reducing valve is used as the primary line, and the switching valve side (actuator side) is used as the secondary line, with the secondary line and the primary line connected only via the non-leak type pressure reducing valve. In this circuit, the non-leak type pressure reducing valve is closed in the initial state (before opening the switching valve). When the switching valve is activated, the pressure in the secondary line decreases, causing the non-leak type pressure reducing valve to open and the hydraulic fluid to flow.

[0006] When a cylinder or other actuator reaches the end of its stroke, the pressure in the secondary pipeline rises, and if it exceeds the rated pressure of the non-leak type pressure reducing valve, the valve closes. At this time, because the non-leak type pressure reducing valve has a response delay, high-pressure hydraulic fluid from the primary pipeline flows into the secondary pipeline, which may cause the pressure in the secondary pipeline to exceed the rated pressure. This is called surge pressure.

[0007] Non-leakage type pressure reducing valves lack a circuit to release surge pressure, causing it to accumulate in the secondary piping. This means that when the cylinder next operates, the pressure in the secondary piping will be higher than the rated pressure (intended pressure), potentially causing the cylinder to operate with excessive force, leading to workpiece deformation or reduced machining accuracy.

[0008] Therefore, the present invention aims to provide a hydraulic system that can suppress surge pressure generated by a pressure-reducing valve. [Means for solving the problem]

[0009] In view of the above issues, a typical configuration of the present invention comprises a hydraulic pump, a switching valve that supplies hydraulic pressure to an actuator, a plurality of solenoid valves arranged in parallel between the hydraulic pump and the switching valve, an accumulator connected to the primary pipeline on the hydraulic pump side of the plurality of solenoid valves, and a pressure sensing unit connected to the secondary pipeline on the switching valve side of the plurality of solenoid valves. The plurality of solenoid valves are controlled to open and close according to the pressure detected by the pressure sensing unit, and the plurality of solenoid valves have different closing set pressures, and close in stages as the pressure in the secondary pipeline rises toward the rated pressure.

[0010] It is preferable that the solenoid valves have different flow rates, and that the closing pressure is set lower for solenoid valves with higher flow rates.

[0011] Preferably, the secondary pipeline is equipped with a relief valve that releases oil to the tank when the pressure in the secondary pipeline reaches a predetermined pressure higher than the rated pressure. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a hydraulic system that can suppress surge pressure generated in a pressure-reducing valve. [Brief explanation of the drawing]

[0013] [Figure 1] This is a hydraulic circuit diagram illustrating the hydraulic system according to this embodiment. [Modes for carrying out the invention]

[0014] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in these embodiments are merely illustrative to facilitate understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to the present invention are omitted from the illustrations.

[0015] Figure 1 is a hydraulic circuit diagram illustrating the hydraulic system according to this embodiment. In the hydraulic system 100 shown in Figure 1, a hydraulic pump 104 operated by a motor 102 sends hydraulic fluid from the oil tank 106 to the primary pipeline 110. In this embodiment, the upstream side (hydraulic pump 104 side) of the solenoid valves SOL1 and SOL2, which will be described later, is referred to as the primary pipeline 110, and the downstream side (switching valves 140, 142, and 144 side) of the solenoid valves SOL1 and SOL2 is referred to as the secondary pipeline 130.

[0016] The primary pipeline 110 is equipped with a check valve 112 to prevent hydraulic fluid from flowing back into the hydraulic pump 104. A relief valve 116 is connected downstream of the check valve 112, and the excess pressure in the primary pipeline 110 is returned to the oil tank 106 via a return pipeline 118.

[0017] Furthermore, a filter 114 is connected to the primary pipeline 110, along with an accumulator 120 and a pressure switch PS0. The pressure switch PS0 monitors the pressure in the primary pipeline 110, and when the pressure falls below a predetermined value, it drives the motor 102 to send hydraulic fluid into the primary pipeline 110, accumulating the hydraulic fluid in the accumulator 120. The type of accumulator 120 is not limited.

[0018] Furthermore, multiple solenoid valves are arranged in parallel in the primary pipeline 110. In this embodiment, an example is shown in which two first solenoid valves SOL1 and a second solenoid valve SOL2 are arranged in parallel, but the present invention is not limited to this, and three or more solenoid valves may be arranged.

[0019] The first solenoid valve SOL1 is a check valve-type on / off valve (solenoid valve). The first solenoid valve SOL1 is normally open. A pressure switch PS1, which is a pressure sensing unit, is located in the secondary pipeline 130 downstream of solenoid valves SOL1 and SOL2. When the pressure in the secondary pipeline 130 reaches the set pressure of the first solenoid valve SOL1, the switch is controlled to open and close the first solenoid valve SOL1.

[0020] The second solenoid valve SOL2 is a throttle valve (solenoid valve) with a check valve function. The second solenoid valve SOL2 is normally open, but because it is a throttle valve, the flow rate is restricted to less than that of the first solenoid valve SOL1. A pressure switch PS2, which is a pressure sensing unit, is located in the secondary pipeline 130, and when the pressure in the secondary pipeline 130 reaches the set pressure of the second solenoid valve SOL2, it is controlled to open and close SOL2.

[0021] Here, the first solenoid valve SOL1 and the second solenoid valve SOL2 have different closing set pressures, and the set pressure of the first solenoid valve SOL1 is set lower than the set pressure of the second solenoid valve SOL2. Thus, as the pressure in the secondary pipeline 130 rises towards the rated pressure, the first solenoid valve SOL1 and the second solenoid valve SOL2 close step by step.

[0022] That is, the plurality of solenoid valves have different flow rates and closing set pressures, and the solenoid valve with a larger flow rate has a lower closing set pressure (closes at an earlier stage).

[0023] When the load on the actuator is low (when the actuator operates at high speed, that is, when the pressure in the secondary pipeline 130 drops significantly), both of the two solenoid valves SOL1 and SOL2 are turned ON to reduce the pressure loss, and it becomes possible to flow a large flow rate of hydraulic oil from the primary pipeline 110.

[0024] When the pressure in the secondary pipeline 130 approaches the rated pressure, the pressure switch PS1 detects this and turns OFF the first solenoid valve SOL1 with a large flow rate. Then, since the flow area is restricted when looking at the entire solenoid valves SOL1 and SOL2, pressure reduction is performed, and the pressure rise in the secondary pipeline 130 becomes gentle.

[0025] In order to reduce the pressure loss of the plurality of solenoid valves (solenoid valves SOL1 and SOL2), it is preferable that the total flow area of the plurality of solenoid valves is not less than the flow area of the primary pipeline 110. This is the same when there are three or more solenoid valves. Also, in order to perform stepwise pressure reduction, it is necessary that the total flow area of the remaining solenoid valves after closing the first solenoid valve is less than the flow area of the primary pipeline 110.

[0026] Furthermore, when the pressure further rises to the rated pressure, the pressure switch PS2 detects this and turns OFF the second solenoid valve SOL2 with a small flow rate. Of course, there is also a response delay in the second solenoid valve SOL2, so a surge pressure is generated, but since the second solenoid valve SOL2 has a small flow rate, it becomes possible to suppress the surge pressure generated in the secondary pipeline 130.

[0027] Furthermore, the pressure in the secondary pipeline 130 can be measured using the pressure sensor PS3 described later, and the second solenoid valve SOL2 can be switched on and off in small increments before reaching the rated pressure. This can further slow down the pressure rise near the rated pressure.

[0028] A manually operated gate valve 132 is connected to the secondary pipeline 130, allowing the hydraulic fluid to be drained to the oil tank 106 via the return pipeline 118.

[0029] Multiple P ports for supplying pressure are connected to the secondary pipeline 130, depending on the number of actuators (not shown) required. Switching valves 140, 142, and 144 are connected to each P port, and A ports (normally closed) and B ports (normally open) for the operating path are connected to actuators for each of the switching valves 140, 142, and 144. In Figure 1, switching valve 140 is shown as a 4-port 2-position solenoid valve (spring return), and switching valves 142 and 144 are shown as 4-port 3-position solenoid valves (spring center), but the type of switching valve can be selected as appropriate.

[0030] The secondary pipeline 130 is also equipped with an electromagnetic relief valve SOL3. The electromagnetic relief valve SOL3 is normally closed and opens when the pressure sensor PS3, which measures the pressure in the secondary pipeline 130, detects a predetermined pressure higher than the rated pressure. This allows hydraulic fluid to escape from the secondary pipeline 130 to the oil tank 106 in the event of a surge pressure in the secondary pipeline 130 due to external factors. The electromagnetic relief valve SOL3 is a throttle valve and has a low flow rate. This allows the pressure in the secondary pipeline 130 to decrease gradually and prevents excessive pressure release.

[0031] This eliminates the need for continuous drainage, as is the case with spool-type pressure reducing valves. While non-leak type pressure reducing valves offer high energy efficiency, they have the problem of trapping surge pressure and being unable to release it. However, with the configuration of the present invention, surge pressure can be efficiently released into the oil tank 106. Since the pressurized oil stored in the accumulator 120 can be used effectively, the operating time of the hydraulic pump 104 can be reduced, and the power consumption of the motor 102 can be lowered, thus contributing to energy savings.

[0032] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to such examples. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. [Industrial applicability]

[0033] This invention can be used as a hydraulic system that supplies hydraulic fluid discharged from a hydraulic pump to an actuator. [Explanation of Symbols]

[0034] PS0, PS1, PS2…Pressure switch, PS3…Pressure sensor, SOL1…First solenoid valve, SOL2…Second solenoid valve, SOL3…Solenoid relief valve, 102…Motor, 104…Hydraulic pump, 106…Oil tank, 110…Primary line, 112…Check valve, 114…Filter, 116…Relief valve, 118…Return line, 120…Accumulator, 130…Secondary line, 132…Gate valve, 140, 142, 144…Switching valve

Claims

1. Hydraulic pump and A switching valve that supplies hydraulic pressure to the actuator, A plurality of solenoid valves arranged in parallel between the hydraulic pump and the switching valve, An accumulator connected to the primary side pipeline which is the hydraulic pump side of the plurality of solenoid valves, The system includes a pressure detection unit connected to the secondary pipeline which is the switching valve side of the plurality of solenoid valves, The plurality of solenoid valves are controlled to open and close according to the pressure detected by the pressure detection unit. A hydraulic system characterized in that the plurality of solenoid valves have different set closing pressures, and as the pressure in the secondary pipeline rises toward the rated pressure, the plurality of solenoid valves close in stages as they reach their respective set pressures.

2. The aforementioned multiple solenoid valves have different flow rates. The hydraulic system according to claim 1, characterized in that the closing pressure of the solenoid valve is set lower for larger flow rates.

3. The hydraulic system according to claim 1, characterized in that the secondary pipeline is equipped with a relief valve that releases oil to a tank when the pressure in the secondary pipeline is at a predetermined pressure higher than the rated pressure.

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