JP7474908B1 - Hydraulic device and operating method - Google Patents

Abstract

[Problem] In a configuration using a single hydraulic oil cooling path and accumulator, the collision surge pressure suppression configuration and the hydraulic oil cooling configuration are separate, which leads to a relatively large size, and the hydraulic oil temperature rise cannot be suppressed during a series of cylinder strokes, so that no effect can be expected in a hydraulic device when a large force is continuously applied stably. [Solution] The hydraulic device of the present invention has at least two flow paths connected to an accumulator on the hydraulic oil discharge side of the cylinder, and further has a bypass connected to the accumulator at a midpoint of one of these flow paths, and each flow path is provided with a valve controlled by a control device. [Effect] Since it is no longer necessary to use separate circuits for shock avoidance and high temperature suppression, the device can be made smaller, and it is possible to adjust the cylinder speed until it reaches the top dead center and bottom dead center of the cylinder stroke, and to cool the hydraulic oil by circulating it. [Selected Figure] Figure 1

Description

The present invention relates to a hydraulic device and its operating method that enables stable operation over a long period of time and extends the life of the entire hydraulic device.

Hydraulic equipment, consisting of hydraulic circuits, accumulators, cylinders, control devices, etc., can generate a stable, large force, but has the following problems. It raises the temperature of the hydraulic oil, accelerating the oxidation and deterioration of the hydraulic oil and shortening the life of the hydraulic equipment and seals. Also, an increase in the gas temperature in the accumulator increases the enclosed gas pressure and worsens the accuracy of the molding force. When molding in accordance with the movement of the press slider, for example when used in forging equipment, the collision surge pressure at the start of forging and the collision load at the time of removal shorten the system life. By solving these issues, stable operation over a long period of time is possible and the life of the entire equipment can be extended.

Various approaches have been taken to address this known issue in the past. For example, Patent Document 1 (JP 2014-9805 A) proposes the following configuration to address the problem of high hydraulic oil temperatures and shock suppression. In detail, even if an accumulator is provided to suppress shock, if high-temperature hydraulic oil accumulates in the accumulator, it will deteriorate the material of the accumulator and shorten its durability life. In addition, using an expensive heat-resistant accumulator will increase costs.

That is, Patent Document 1 discloses a hydraulic circuit for a work machine that includes a hydraulic actuator and an accumulator that accumulates hydraulic energy discharged from the hydraulic actuator while supplying the accumulated hydraulic energy to the hydraulic actuator, in which a cooling pipe having a volume equivalent to the pressure accumulation volume of the accumulator is disposed in the inlet oil path for hydraulic oil to the accumulator, and the hydraulic oil cooled by the cooling pipe is accumulated in the accumulator.

Hydraulic devices have a wide range of applications, but when used to configure a forging press, for example, it is necessary to apply a strong and stable force to the die. In this case, the hydraulic oil needs to flow under high pressure and high airtight conditions, which generates an extremely large surge pressure and also generates a lot of heat.

Therefore, Patent Document 1 is specialized in hydraulic devices for driving cylinder devices in hydraulic excavators and the like, in other words, it is used to drive the cylinder stroke in and out, and the problem of high hydraulic oil temperature and the problem of impact are solved by separate configurations. In addition, a single tube is zigzag, spirally or divided into multiple sections, and cooling means is added to the configuration. As a result, the device configuration becomes larger and the hydraulic device does not produce the expected effect when a large force is continuously applied stably.

JP 2014-9805 A

The problem to be solved is that in conventional configurations, including Patent Document 1, which uses a conventional single-path hydraulic oil cooling path and accumulator, the configuration for suppressing collision surge pressure and the configuration for cooling the hydraulic oil are separate, resulting in a relatively large size; it is also not possible to suppress the temperature rise of the hydraulic oil during a series of cylinder strokes, and therefore no effect can be expected in a hydraulic device when a large and stable force is continuously applied.

In order to solve the above problems, the present invention provides a hydraulic device that operates by a hydraulic circuit including an accumulator, a cylinder, and a valve controlled by a control device, in which at least two flow paths are provided connecting the cylinder and the accumulator, and a bypass connected to the accumulator is provided midway through one of the flow paths, and a valve controlled by the control device is provided in each of the flow paths.

With the above-mentioned configuration, the present invention provides at least two flow paths and a bypass, eliminating the need for separate circuits for impact avoidance and high temperature suppression, thereby making the device more compact. In addition, in the cylinder stroke cycle, it becomes possible to adjust the cylinder speed up to the top dead center and bottom dead center of the cylinder stroke, and it becomes possible to circulate the hydraulic oil to cool it. This suppresses collision surge pressure and prevents damage and breakdowns of the device due to high temperatures of the hydraulic oil, enabling stable operation over a long period of time and extending the life of the entire hydraulic device.

FIG. 2 is a diagram showing a hydraulic circuit configuration in the hydraulic device of the present invention. FIG. 4 is a diagram showing the flow of hydraulic oil when the press is on standby in the hydraulic device of the present invention. FIG. 4 is a diagram showing the flow of hydraulic oil up to the bottom dead center in the hydraulic device of the present invention. FIG. 4 is a diagram showing the flow of hydraulic oil when the ram rises in the hydraulic device of the present invention. FIG. 4 is a diagram showing the flow of hydraulic oil up to the top dead center in the hydraulic device of the present invention. 4 is a graph showing the relationship between stroke length, cam rotation angle, and stroke speed in the hydraulic device of the present invention.

The present invention improves upon the drawbacks caused by a configuration in which a hydraulic oil cooling path and an accumulator are used separately by providing at least two flow paths connecting the cylinder and the accumulator , and further providing a bypass connected to the accumulator at a midpoint in one of these flow paths, and providing a valve controlled by the control device in each of the flow paths.

The hydraulic device having the above configuration operates according to the operating method of the present invention, i.e., the procedure of connecting the flow path to the accumulator by the valve just before the bottom dead center of the cylinder stroke, and connecting the accumulator and the cylinder via the bypass by the valve halfway to the top dead center of the cylinder stroke.

In the present invention, at least two flow paths are provided connecting the cylinder and the accumulator , and a bypass connected to the accumulator at a midpoint of one of these flow paths forms a circulation path passing through the forward and return chambers of the rod within the cylinder.

This circulation path is not only used to cool the hydraulic oil by exposing it to the outside, but also to switch between a situation where a specified cylinder stroke is performed and a situation where reduced pressure hydraulic oil is sent to decelerate the cylinder stroke, using a valve controlled by the control device.

In other words, the hydraulic device of the present invention can cool the hydraulic oil in the reduced pressure flow path by using the drain path properly as described above, and by using the reduced pressure and cooled hydraulic oil before the bottom dead center of the cylinder stroke is reached, it is possible to suppress the collision surge pressure and also to suppress the temperature rise of the hydraulic oil due to high pressure. The relief valve of the cooling circuit is set higher than the set pressure of the pressure reducing valve so that the hydraulic pump does not discharge wastefully during cooling.

Specific embodiments of the present invention will be described below with reference to Figures 1 to 6. In this example, the hydraulic device of the present invention is used in a closed forging press having upper and lower rams P1, P2 that protrude (rise) and retract (descend) into upper and lower cylinders S1, S2, and a cam (not shown) that raises or lowers the upper and lower rams P1, P2 by injecting hydraulic oil into the upper and lower cylinders S1, S2, and a sensor that detects the rotation angle of this cam.

The components used in the hydraulic circuit of this embodiment are as follows. In the figure, 1 is a hydraulic pump, 2 is an accumulator, 3 is an amplifier, 4 is a proportional valve, 5 is a pressure reducing valve, 6a and 6b are relief valves, 7 is a cooling pump, 8a and 8b are solenoid valves, 9 is a check valve, 10a, 10b, 10c and 10d are logic valves, 11 is an orifice, 12 is a cooler, 13 is a tank, and 14a and 14b are throttle valves. Furthermore, the hydraulic circuit of this embodiment is equipped with a control device (not shown) that controls the overall operation of the valves and pumps, including the logic valves 10a, 10b, 10c and 10d.

The hydraulic device of this embodiment has the following circuit configuration using the above elements. The upper and lower cylinders S1 and S2 are formed with circulation paths of one path L1a, L2a and the other path L1b, L2b that are folded back at the upper and lower cylinders S1 and S2, respectively.

The sides of one of the paths L1a, L2a and the other of the paths L1b, L2b opposite the upper and lower cylinders S1, S2 are cooling circuits, and relief valves 6a, 6b are provided midway through one of the paths L1a, L2a, respectively. Also, check valves Ca, Cb, Cc, Cd are provided in one of the paths L1a, L2a and the other of the paths L1b, L2b, respectively.

Furthermore, in the cooling circuit, solenoid valves 8a are provided in one path L1a, L2a via check valves Ca, Cb, Cc, Cd, and solenoid valves 8b are provided in the other path L1b, L2b, respectively.

As described below, these solenoid valves 8a, 8b return hydraulic oil to the tank 13 via the cooler 12 and orifice 11 during press standby, and form a hydraulic oil cooling circuit in one circulation path L1a, L2a and the other circulation path L1b, L2b via a flow path that sends hydraulic oil from the tank 13 by the cooling pump 7 via a check valve 9.

As described below, the solenoid valves 8a, 8b block the flow to the upper and lower cylinders S1, S2 from the start of the ram descent to the end of the ascent, forming a circuit connecting a flow path that sends hydraulic oil by the cooling pump 7 via the tank 13 and the check valve 9, and a flow path that returns hydraulic oil to the tank 13 via the orifice 11. At this time, the circulation paths of one path L1a, L2a and the circulation paths of the other path L1b, L2b form a cylinder operating circuit for the upper and lower cylinders S1, S2.

The cylinder operating circuit has operating paths M1a, M1b connected to the accumulator 2 at the midpoints of one path L1a and the other path L1b of the upper cylinder S1, and operating paths M2a, M2b connected to the accumulator 2 at the midpoints of one path L2a and the other path L2b of the lower cylinder S2.

Logic valves 10a, 10b, 10c, and 10d are provided in the middle of each of the operating paths M1a, M1b, M2a, and M2b, respectively, and each of the operating paths M1a, M1b, M2a, and M2b merges with one path L1a and the other path L1b, and one path L2a and the other path L2b, on the opposite side to the connection end via these logic valves 10a, 10b, 10c, and 10d, and is connected to the accumulator 2.

In this example, in the upper cylinder S1, there are two paths, one path L1a and operating path M1a, and the other path L1b and operating path M1b, and in the lower cylinder S2, there are two paths, one path L2a and operating path M2a, and the other path L2b and M2b, which each correspond to the "at least two flow paths connecting the cylinder and the accumulator " referred to in the present invention.

In addition, pressure reduction paths G1 and G2 are connected to the operating paths M1a and M2a at their intermediate positions leading to the logic valves 10a and 10c, respectively, and check valves Gc1 and Gc2 are connected to the intermediate positions of the pressure reduction paths G1 and G2, respectively.

The pressure reduction paths G1, G2 merge on the opposite side of the connection side of the operating paths M1a, M2a in the pressure reduction paths G1, G2 via check valves Gc1, Gc2, and are connected to a junction path that is connected to accumulators 2 of the operating paths M1a, M1b, M2a, M2b via pressure reduction valve 5.

In this example, the pressure reduction paths G1 and G2 correspond to a "bypass connected to the accumulator at a midpoint of one of these paths." In this example, "one of these paths" means that the pressure reduction path G1 is connected to one of the paths L1a and the operating path M1a of the two "paths" in the cylinder S1, and the pressure reduction path G2 is connected to one of the paths L2a and the operating path M2a of the two "paths" in the cylinder S2.

Furthermore, an oil supply passage I is connected to the junction passage connected to the accumulator 2 of the operating passages M1a, M1b, M2a, and M2b, which sends hydraulic oil from the tank 13 at a predetermined pressure using a hydraulic pump 1 provided via an amplifier 3 and a proportional valve 4.

The hydraulic device having the above configuration operates as follows.
1 (press standby)
As shown in Fig. 2, the cylinder circuit is cooled when the molding pressure is maintained. Hydraulic oil is accumulated in an accumulator 2 by a hydraulic pump 1. The pressure at which the oil is accumulated in the accumulator 2 is preset by a proportional valve 4 and an amplifier 3.

In this embodiment, a low pressure set in advance by the pressure reducing valve 5 and the relief valves 6a and 6b is supplied to the upper cylinder S1 and the lower cylinder S2 of the upper and lower rams P1 and P2, creating a low-pressure preload state. The set pressure of the pressure reducing valve 5 is set lower than the set pressure of the relief valves 6a and 6b, so that the hydraulic oil sent to the accumulator 2 by the hydraulic pump 1 is not wasted.

Meanwhile, the cooling circuit cools the entire system through a circulation path formed by the cooling pump 7 passing the hydraulic oil in the tank 13 through solenoid valves 8a, 8b, and the upper cylinder S1 and the lower cylinder S2 and the solenoid valves 8a, 8b, respectively, through other paths L1b, L2b from the tank 13 to the upper and lower cylinders S1, S2 via the cooling pump 7, and one path L1a, L2a going to the tank 13 via the cooler 12.

That is, when solenoid valves 8a, 8b are turned ON, a flow path from cooling pump 7 is formed in other paths L1b, L2b, and a flow path returning to the tank via cooler 12 is formed in one paths L1a, L2. A portion of the hydraulic oil is regulated by orifice 11 just before check valve 9 near the suction of cooling pump 7 and returned to tank 13, while the majority is returned to the suction of cooling pump 7. In this way, the stirring flow rate in tank 13 can be reduced, making it possible to reduce the capacity of tank 13.

2 (Initial forming: up to bottom dead point)
As shown in Figure 3, the upper and lower rams P1, P2 sink (hereinafter referred to as descending) within the upper and lower cylinders S1, S2 until they reach the bottom dead center in their stroke length, and the hydraulic oil in the upper and lower cylinders S1, S2 is discharged in accordance with the descent of the upper and lower rams P1, P2.

Just before reaching bottom dead center, logic valves 10a, 10b (upper cylinder S1) and logic valves 10c, 10d (lower cylinder S2) switch the hydraulic oil discharged from the upper and lower cylinders S1, S2 from one path L1a, L2a and the other path L2a, L2b to a path in which hydraulic oil is injected into accumulator 2 via operating paths M1a, M1b, M2a, M2b, ensuring molding pressure and slowing down the descent speed of rams P1, P2, which becomes zero at bottom dead center as shown in Figure 6. This suppresses the collision surge pressure that occurs at bottom dead center.

Meanwhile, in the cooling circuit, solenoid valves 8a and 8b are turned OFF to cut off the flow paths leading to one path L1a, L2a and the other path L2a, L2b, and the flow path from the cooling pump 7 is folded back at the solenoid valves 8a and 8b to form a flow path returning to the tank 13 via the cooler 12.

3 (molding in progress: ram rising)
As shown in Figure 4, the upper and lower rams P1, P2 reach bottom dead center in their stroke length, and then protrude (hereinafter referred to as rising) from within the upper and lower cylinders S1, S2 for molding. In conjunction with this rising of the upper and lower rams P1, P2, the logic valves 10a to 10d inject the hydraulic oil stored in the accumulator 2 via the operating paths M1a, M1b, M2a, M2b and from one path L1a, L2a and the other path L2a, L2b into the upper and lower cylinders S1, S2, respectively, thereby raising the upper and lower rams P1, P2.

Meanwhile, in the cooling circuit, as in the state up to the ram bottom dead center described above, solenoid valves 8a and 8b are turned OFF, the flow paths leading to one path L1a, L2a and the other path L2a, L2b are cut off, and the flow path from the cooling pump 7 is folded back at the solenoid valves 8a and 8b to form a flow path returning to the tank 13 via the cooler 12.

4 (After molding: up to top dead center)
As shown in FIG. 5, when a sensor attached to a cam (not shown) detects that the upper and lower rams P1, P2 have risen past the bottom dead center to a preset position just before reaching the top dead center of the stroke length of the upper and lower rams P1, P2, an output signal to that effect is received from the sensor, and the logic valves 10a to 10d stop injecting the hydraulic oil stored in the accumulator 2 into the upper and lower cylinders S1, S2, and the hydraulic oil that has been reduced in pressure by the pressure reducing valve 5 is injected from one of the paths L1a, L2a via the pressure reducing paths G1, G2.

At the above timing, the hydraulic oil is pressure-reduced by the pressure reducing valve 5 through the logic valves 10a to 10d, and then injected through one of the paths L1a and L2a via the pressure reducing paths G1 and G2. As the upper and lower cylinders S1 and S2 reach their return ends, their speeds are slowed down as shown in Figure 6, thereby suppressing the collision surge pressure that leads to the top dead center.

Meanwhile, in the cooling circuit, as in the state up to the ram bottom dead center described above, solenoid valves 8a and 8b are turned OFF, the flow paths leading to one path L1a, L2a and the other path L2a, L2b are cut off, and the flow path from the cooling pump 7 is folded back at the solenoid valves 8a and 8b to form a flow path returning to the tank 13 via the cooler 12.

Figure 6 shows the above operations 1 to 4 in terms of the stroke length of the upper and lower rams P1 and P2, for example the upper ram P1, the rotation angle of the cam, and the stroke speed. As shown in Figure 6, in the present invention, at a predetermined point leading to the bottom dead center of the ram, the speed is reduced, i.e. the pressure is reduced, as described above, so that at the bottom dead center, the slide speed is 0.00 m/sec.

To repeat the above using Figure 3, in this example of implementing the present invention, at a predetermined point just before bottom dead center, the logic valves 10a to 10d are opened to allow the hydraulic oil discharged from the upper and lower cylinders S1, S2 to pass in a free flow manner from one path L1a, L2a and the other path L1b, L2b via the operating paths M1a, M1b, M2a, M2b, and is absorbed in the accumulator 2, thereby slowing down and reducing the pressure.

When the top dead center is reached, the logic valves 10a to 10d are closed at a predetermined timing, and the upper and lower rams P1 and P2 are returned with oil that has been reduced in pressure by the pressure reducing valve 5 during standby. Figure 6 shows that the slide speed is 0.00 m/sec at the top dead center of the slide stroke.

In this way, the configuration of the present invention allows the hydraulic oil required for hydraulic drive during molding to be circulated within the flow path in a selective manner, making it possible to cool the oil temperature and suppress collision surge pressure, thereby extending the life of the mold.

Furthermore, in the present invention, a cooling circuit is provided in the circulation path, so that the hydraulic oil necessary for hydraulic drive can be cooled in the atmosphere, while the hydraulic oil not currently required for hydraulic drive can be actively cooled by the cooler 12. The hydraulic oil circulates in the tank 13. In this way, the hydraulic oil that is currently required and the hydraulic oil that is not required are separated so that they can be cooled in the atmosphere or actively cooled, so there is no need to cool all the hydraulic oil in the cooling circuit, which allows the tank to be made smaller, and ultimately makes it possible to make the entire configuration more compact.

REFERENCE SIGNS LIST 1 Hydraulic pump 2 Accumulator 5 Pressure reducing valve 8a, 8b Solenoid valve 10a, 10b, 10c, 10d Logic valve S1 Upper cylinder S2 Lower cylinder L1a, L2a One path L1b, L2b Other path M1a, M1b, M2a, M2b Operating path G1, G2 Pressure reducing path

Claims (2)

A hydraulic device that operates by a hydraulic circuit having an accumulator, a cylinder, and a valve controlled by a control device, wherein at least two flow paths are provided connecting the cylinder and the accumulator, and a bypass connected to the accumulator is provided at a midpoint of one of the flow paths, and a valve controlled by the control device is provided in each of the flow paths. A method for operating a hydraulic device that operates by a hydraulic circuit including an accumulator, a cylinder, and a valve controlled by a control device, wherein at least two flow paths are provided connecting between the cylinder and the accumulator, and a bypass connected to the accumulator is provided at a midpoint of one of the flow paths, and each of the flow paths is provided with a valve controlled by the control device, wherein the valve connects the flow path to the accumulator just before the bottom dead center of the cylinder stroke, and the valve connects the accumulator and the cylinder via the bypass midway up the cylinder stroke to the top dead center.

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