HYDRAULIC DRIVE CIRCUIT AND HYDRAULIC VALVE DEVICE

Abstract

To prevent a situation of insufficient oil supply to the hydraulic cylinder and a deterioration in fuel efficiency, a hydraulic drive circuit includes a hydraulic cylinder 2, configured for operation with oil supplied by a hydraulic pump 1, a reversing valve 10 located in an oil channel 50A, 50B between the hydraulic pump 1 and the hydraulic cylinder 2, a load check valve 20 located in the oil channel between the reversing valve 10 and the hydraulic cylinder 2 in the oil channel 50B and configured to allow oil passage in only one direction from the reversing valve 10 to the hydraulic cylinder 2, and a shut-off valve 30 configured to block the oil flow from the hydraulic cylinder 2.The shut-off valve 30 is connected to the hydraulic cylinder 2 via a branch oil channel 50C, which branches off from the oil channel 50B between the hydraulic cylinder 2 and the load check valve 20.

Description

TECHNICAL AREA

[0001] The present invention relates to a hydraulic drive circuit and a hydraulic valve device for driving a hydraulic cylinder. STATE OF THE ART

[0002] In some hydraulic drive circuits for driving a hydraulic cylinder, a reversing valve and a check valve are provided in the oil channel between the hydraulic pump and the hydraulic cylinder. The check valve is intended to prevent oil from escaping the hydraulic cylinder when the reversing valve is in a neutral position and to prevent the hydraulic cylinder from being operated unintentionally (see, for example, patent document 1). LIST OF COUNTERPOINTS Patent Literature

[0003] Patent Document 1: JP 7-279905 A BRIEF DESCRIPTION OF THE INVENTION Technical Problem

[0004] Although the shut-off valve described above opens when oil is supplied from the hydraulic pump to the hydraulic cylinder, there is a risk of pressure loss occurring, which could lead to an insufficient oil supply to the hydraulic cylinder or a deterioration in fuel efficiency.

[0005] One object of the present invention is to provide a hydraulic drive circuit and a hydraulic valve device that can prevent a situation of insufficient oil supply to the hydraulic cylinder or a deterioration of fuel efficiency. Solution to the problem

[0006] To solve the aforementioned problem, a hydraulic drive circuit according to the present invention includes a hydraulic cylinder configured to operate with oil supplied by a hydraulic pump, a reversing valve arranged in an oil channel between the hydraulic pump and the hydraulic cylinder, a load check valve arranged in the oil channel between the reversing valve and the hydraulic cylinder and configured to allow oil passage only from the reversing valve to the hydraulic cylinder, and a shut-off valve configured to block oil flow from the hydraulic cylinder. The shut-off valve is connected to the hydraulic cylinder via a branch oil channel that branches off from the oil channel between the hydraulic cylinder and the load check valve. Advantageous effects of the invention

[0007] The present invention prevents oil from escaping through the oil channel by means of the load check valve and prevents oil from escaping through the branch oil channel by means of the shut-off valve when the direction changeover valve is in a neutral position. Furthermore, when oil is supplied to the hydraulic cylinder, no pressure loss occurs at the shut-off valve, thus preventing insufficient oil supply and a deterioration in fuel efficiency. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 illustrates a hydraulic drive circuit to which a hydraulic valve device according to an embodiment of the present invention is applied, in which a slide valve is in a neutral position. Fig. 2 is a sectional view showing the structure of the Fig. 1 illustrated hydraulic valve device illustrated. Fig. Figure 3 is a diagram of a hydraulic drive circuit in a state where the valve is moved from the neutral position into Fig. 1 moved to the left. Fig. 4 is a diagram of a hydraulic drive circuit in a state where the valve is moved from the neutral position into Fig. 1 is moved to the right. Fig. 5A is a schematic view of an external appearance of the in Fig. 1 illustrated hydraulic valve device, from the direction of arrow A in Fig. 2 seen. Fig. 5B is one of the arrows B in Fig. 5A as seen from the viewpoint. DESCRIPTION OF EXECUTION FORMS

[0008] In the following, a hydraulic drive circuit and a hydraulic valve device according to a preferred embodiment of the present invention are described in detail with reference to the accompanying drawings.

[0009] Fig. Figure 1 illustrates a hydraulic drive circuit to which a hydraulic valve device according to an embodiment of the present invention is applied. The hydraulic drive circuit illustrated here serves to drive a hydraulic cylinder 2 by means of oil supplied by a hydraulic pump 1. The hydraulic pump 1 is a variable displacement pump in which the displacement volume is changed by altering the tilt angle of the swashplate or the swash shaft. In the hydraulic cylinder 2, an actuating rod 2b is moved to a cylinder body 2a by supplying oil to the pressure chamber. For the sake of simplicity, the example illustrated in the drawing shows a hydraulic drive circuit for controlling the oil supply to a bottom chamber 2c provided in the cylinder body 2a.

[0010] A hydraulic valve assembly 3 is provided between the hydraulic pump 1 and the hydraulic cylinder 2. The hydraulic valve assembly 3 is arranged between the bottom chamber 2c of a hydraulic cylinder 2 and the hydraulic pump 1. A valve body 3A includes a reversing valve 10, a load check valve 20, a shut-off valve 30, and a suction safety valve (suction valve and safety valve) 40.

[0011] The valve body 3A is a single block and includes a pump port 3a, a cylinder port 3b, and three tank ports 3c, 3d, and 3e. The pump port 3a is connected to the hydraulic pump 1 via a supply oil channel 4. The cylinder port 3b is connected to the bottom chamber 2c of the hydraulic cylinder 2 via a bottom oil channel 5. The three tank ports 3c, 3d, and 3e are connected to a tank T via the drain oil channels 6c, 6d, and 6e, respectively. In the following description, these tank ports 3c, 3d, and 3e are referred to as the first tank port 3c, the second tank port 3d, and the third tank port 3e, respectively.

[0012] The reversing valve 10 is configured such that a slide 11 is provided as the first valve element in the valve body 3A. As shown in Fig. As illustrated in Figure 2, the slide 11 has a cylindrical shape with a plurality of web sections and is arranged in a slide hole 12 of the valve body 3A such that it is movable along the axis (first axis) C1. In the slide hole 12, a pump oil supply port 12a, an inlet port 12b, an outlet port 12c, and a drain port 12d are arranged in that order from the Fig. 2. The bottom end is provided. When the slide 11 is moved along an axis C1, the connection states of the pump oil supply port 12a and the drain port 12d are switched with respect to the inlet port 12b and the outlet port 12c.

[0013] More precisely, when the slide 11 is in the neutral position, both the inlet port 12b and the outlet port 12c are each in a blocked state. When the slide 11 moves from the neutral position to the left... Fig. 1 is moved, as in Fig. As illustrated in Figure 3, the inlet port 12b and the pump oil supply port 12a are connected, while the outlet port 12c remains blocked. When the slide 11 moves to the right from the neutral position into Fig. 1 moves as in Fig. As illustrated in Figure 4, the inlet port 12b remains blocked, while the outlet port 12c and the drain port 12d are connected (drain position).

[0014] The pump oil supply port 12a is connected to the pump port 3a via the first oil channel section (oil channel) 50A. The inlet port 12b is connected to the cylinder port 3b via the second oil channel section (oil channel) 50B. The outlet port 12c is connected to the third oil channel section (branch oil channel) 50C, which branches off from the second oil channel section 50B. The drain port 12d is connected to the first tank port 3c via a fourth oil channel section 50D.

[0015] As from Fig. As can be seen in Figure 2, a centering spring 13 is provided at one end of the slide 11, and pressure chambers 14 are provided at both ends. The centering spring 13 serves to hold the slide 11 in a neutral position and is housed in a spring box 15, which is provided on a side surface of the valve body 3A. The pressure chambers 14 contain the ends of the slide 11 and are each filled with oil. Although not illustrated in the drawing, pilot oil channels for applying pilot pressure outputs from the control valves are individually connected to the pressure chambers 14. When the pilot pressure output by the control valve is applied to a pressure chamber 14 via the pilot oil channel, the slide 11 can be moved along axis C1 against the spring force of the centering spring 13. When the pilot pressure exerted on the pressure chamber 14 is removed, the slide 11 returns to the neutral position by the spring force of the centering spring 13.

[0016] As in Fig. As illustrated in Figure 1, the load check valve 20 is configured such that a second valve element 21 is provided at an intermediate section of the second oil channel section 50B in the valve body 3A, specifically between a branch point 50E in the second oil channel section 50B, which branches to a third oil channel section 50C, and the inlet port 12b of the slide 11. The load check valve 20, which includes a check valve functional section 20a and a piston section 20b, is used in the present embodiment. The check valve functional section 20a serves to allow oil flow from the inlet port 12b to the cylinder port 3b and to prevent oil flow from the cylinder port 3b to the inlet port 12b.The piston section 20b serves to provide a pressure equalization function to the check valve functional section 20a, based on the pressure at cylinder port 3b and the load pressure input from an external LS channel 22. More precisely, the pressure at cylinder port 3b is compared with the load pressure input from the external LS channel 22, and if the pressure at cylinder port 3b is higher, the check valve functional section 20a is actuated to increase its opening. As, for example, in... Fig. As illustrated in Figure 2, the second valve element 21 has a cylindrical shape with a conical surface at its tip section and is housed in a second valve hole 23 of the valve body 3A. The second valve hole 23 is arranged such that the second valve element 21 can move along the axis (second axis) C2. As shown in Fig. 5A and Fig. As illustrated in Figure 5B, the second valve hole 23 is provided such that its axis C2 runs in a direction perpendicular to the axis C1 of the slide 11.

[0017] As in Fig. As illustrated in Figure 1, the shut-off valve 30 is configured by providing a third valve element 31 in the valve body 3A at an intermediate section of the third oil channel section 50C. Under normal conditions, the shut-off valve 30 is configured to block oil flow from the branch point 50E, which branches off from the second oil channel section 50B, to the drain port 12c. However, when a pilot pressure is applied by an operating valve (not illustrated) to an integrated switching valve 32, the shut-off valve 30 is configured to allow oil flow from the branch point 50E, which branches off from the second oil channel section 50B, to the drain port 12c.This means that when pilot pressure is applied to the switching valve 32, the back pressure exerted on the third valve element 31 is diverted via the second tank port 3d and a drain oil line 6d into tank T, so that the third valve element 31 is connected and oil flows from the cylinder port 3b to the drain port 12c. When the pilot pressure to the switching valve 32 is removed, the third valve element 31 returns to the blocked state and the oil flow from branch point 50E, which branches off from the second oil channel section 50B, to the drain port 12c is blocked. As shown, for example, in... Fig. As illustrated in Figure 2, the third valve element 31 has a cylindrical shape with a conical surface at its tip and is housed in a third valve hole 33 of the valve body 3A. The third valve hole 33 is arranged such that the third valve element 31 can move along the axis (third axis) C3. As shown in Figure 2, the third valve element 31 is located in a third valve body 3A. Fig. 5A and Fig. As illustrated in Figure 5B, the third valve hole 33 is provided such that its axis C3 is perpendicular to the axis C1 of the slide 11 and is located on a virtual plane P that includes the axis C1 of the slide 11 and the axis C2 of the second valve element 21.

[0018] As in Fig. As illustrated in Figure 1, a suction safety valve 40 is configured such that a fourth valve element 41 is provided at an intermediate section of a fifth oil channel section (second branch oil channel) 50F, which is provided in the valve body 3A. A fifth oil channel section 50F is provided between the branch point 50E in the second oil channel section 50B, which branches to the third oil channel section 50C, and the third tank port 3e. The suction safety valve 40 includes a safety valve section 40a, which allows oil to flow from the branch point 50E to the third tank port 3e only when the pressure of the cylinder port 3b exceeds a specified value, and a suction valve section 40b, which allows oil to flow from the third tank port 3e to the branch point 50E when the pressure of the cylinder port 3b becomes negative. For example, in Fig. As illustrated in Figure 2, the fourth valve element 41 has a cylindrical shape with a conical surface at a tip section and is housed in a casing 42 in a state in which it is movable along an axis (fourth axis) C4 and is attached via the casing 42 to a fourth valve hole 43 of the valve body 3A. The fourth valve hole 43 is arranged such that the fourth valve element 41 is movable along an axis with respect to the casing 42. As shown in Fig. 5A and Fig. As illustrated in Figure 5B, the fourth valve hole 43 is provided such that an axis C4 of it is perpendicular to the axis C1 of the slide 11 and is located on the virtual plane P which includes the axis C1 of the slide 11 and the axis C2 of the second valve element 21.

[0019] When the valve 11 in the hydraulic drive circuit configured as described above is in a neutral position, both the inlet port 12b and the outlet port 12c are blocked. Therefore, no oil flows into the bottom chamber 2c of the hydraulic cylinder 2, and the hydraulic cylinder 2 stops. At this point, according to the hydraulic drive circuit described above, there is no risk of oil escaping from the bottom chamber 2c of the hydraulic cylinder 2 through the hydraulic valve assembly 3. That is, in the hydraulic valve assembly 3 described above, three oil channel sections 50B, 50C, and 50F are connected to the bottom chamber 2c of the hydraulic cylinder 2. The second oil channel section 50B includes the load check valve 20 with the check valve functional section 20a, the third oil channel section 50C includes the shut-off valve 30, and the fifth oil channel section 50F includes the suction safety valve 40.

[0020] Therefore, there is no risk of oil escaping from the bottom chamber 2c of the hydraulic cylinder 2, and there is no concern that the actuating rod 2b will fall naturally. If the pressure in the bottom chamber 2c exceeds the specified value from the above condition, the safety valve section 40a of the suction safety valve 40 is released, and the oil in the bottom chamber 2c is drained into the tank T via the bottom oil channel 5, the cylinder port 3b, the second oil channel section 50B to the branch point 50E, the fifth oil channel section 50F, the safety valve section 40a of the suction safety valve 40, the third tank port 3e, and a drain oil channel 6e. Thus, there is no possibility of a pressure exceeding the specified value being exerted on the bottom chamber 2c, and damage to the hydraulic cylinder 2 can be prevented.

[0021] When the slide 11 is moved from this state by actuating the control valve into Fig. When 1 is moved to the left, the pump oil supply port 12a and the inlet port 12b of the slide 11 are connected, as shown in Fig. Figure 3 illustrates this. Thus, the oil for the hydraulic pump 1 is supplied via the supply oil channel 4, the pump port 3a, the first oil channel section 50A, the pump oil supply port 12a and the inlet port 12b of the valve 11, a second oil channel section 50B, the load check valve 20, the cylinder port 3b and the bottom oil channel 5 of the bottom chamber 2c of the hydraulic cylinder 2, thereby advancing the actuating rod 2b of the hydraulic cylinder 2 towards the cylinder body 2a. At this point, when a vacuum is created in the bottom chamber 2c, the oil in the tank T is supplied to the bottom chamber 2c through the suction valve section 40b of the suction safety valve 40, so that there is no possibility of the advance movement of the actuating rod 2b being prevented.

[0022] If, on the other hand, the slide 11 is moved by actuating the control valve in Fig. When 1 is moved to the right, the outlet port 12c and the drain port 12d of the slide valve 11 are connected and the shut-off valve 30 is opened, as shown in Fig. Figure 4 illustrates this. Thus, the oil from the bottom chamber 2c of the hydraulic cylinder 2 is drained via the bottom oil channel 5, the cylinder port 3b, the second oil channel section 50B to the branch point 50E, the third oil channel section 50C, the shut-off valve 30, the drain port 12c and the drain port 12d of the slide valve 11, the fourth oil channel section 50D, the first tank port 3c and a drain oil channel 6c into the tank T, thereby retracting the actuating rod 2b of the hydraulic cylinder 2 relative to the cylinder body 2a.

[0023] Thus, the hydraulic drive circuit described above can supply the oil from the hydraulic pump 1 to the bottom chamber 2c of the hydraulic cylinder 2 without it having to flow through the shut-off valve 30. This allows the hydraulic cylinder 2 to operate in a state with reduced pressure loss, thereby improving fuel efficiency when the oil supply is insufficient or when the hydraulic pump 1 is driven.

[0024] Furthermore, the second valve element 21 of the load check valve 20, the third valve element 31 of the shut-off valve 30, and the fourth valve element 41 of the suction safety valve 40 are arranged in the valve body 3A such that the axes C2, C3, and C4 are orthogonal to the axis C1 of the slide 11 and are each located on the same plane P, which encloses the axis C1 of the slide 11. This allows the second valve element 21, the third valve element 31, and the fourth valve element 41 to be arranged efficiently, thereby reducing the external dimensions of the valve body 3A.

[0025] Although the embodiments described above illustrate the hydraulic valve device 3 for controlling the supply of oil to the bottom chamber 2c of the hydraulic cylinder 2, the present invention is not limited thereto and can be applied similarly to control the supply of oil to the rod chamber. Furthermore, although the hydraulic valve device 3 is illustrated with the suction safety valve 40, the present invention is not necessarily limited thereto. For example, the fifth oil channel section 50F can be provided with only one safety valve (corresponding to safety valve section 40a) for limiting the load pressure of the hydraulic cylinder, or it can be provided with only one suction valve (corresponding to suction valve section 40b) for supplying oil from the tank to the hydraulic cylinder when a vacuum occurs in the hydraulic cylinder. Reference symbol list 1 hydraulic pump 2 hydraulic cylinders 2c bottom chamber 3 Hydraulic valve device 3A Valve body 3a Pump connection 3b Cylinder connection 3c, 3d, 3e Tank connection 10 Directional changeover valve 11 sliders 20 Load check valve 20a Check valve functional section 20b Piston section 21 Second valve element 22 LS channel 30 shut-off valve 31 Third valve element 40 Suction safety valve 40a Safety valve section 40b Suction valve section 41 Fourth valve element 50A First oil channel section 50B Second Oil Channel Section 50C Third Oil Channel Section 50F Fifth Oil Channel Section C1 First Axis C2 Second Axis C3 Third Axis C4 Fourth Axis P Virtual plane T Tank QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 7-279905 A

[0003]

Claims

Hydraulic drive circuit comprising: a hydraulic cylinder configured to operate with oil supplied by a hydraulic pump; a reversing valve located in an oil channel between the hydraulic pump and the hydraulic cylinder; a load check valve located in the oil channel between the reversing valve and the hydraulic cylinder and configured to allow the passage of oil only from the reversing valve to the hydraulic cylinder; and a shut-off valve configured to block the flow of oil out of the hydraulic cylinder, the shut-off valve being connected to the hydraulic cylinder via a branch oil channel branching off from the oil channel between the hydraulic cylinder and the load check valve. Hydraulic drive circuit according to claim 1, wherein the load check valve has a pressure equalization function configured to control an oil supply flow rate to the hydraulic cylinder according to a load pressure of the hydraulic cylinder. Hydraulic drive circuit according to claim 1, wherein the branch oil channel is arranged between the oil channel and the direction changeover valve and the shut-off valve is connected when the direction changeover valve is switched to a discharge position. Hydraulic drive circuit according to claim 1, wherein at least one safety valve configured to limit a load pressure of the hydraulic cylinder and a suction valve configured to supply oil from a tank to the hydraulic cylinder when the hydraulic cylinder assumes a vacuum, is connected to the hydraulic cylinder via a second branch oil channel branching off from the oil channel between the hydraulic cylinder and the load check valve. Hydraulic valve device comprising a valve body, wherein the valve body comprises a pump port connected to a hydraulic pump, a cylinder port connected to a hydraulic cylinder, and a tank port connected to a tank, wherein the valve body comprises: a directional changeover valve configured to switch a connection state between the pump port and the cylinder port by moving a first valve element along a first axis between the pump port and the cylinder port; a load check valve configured to allow the passage of oil only from the first valve element to the cylinder port by moving a second valve element along a second axis between the first valve element and the cylinder port;and a check valve configured to allow or block the oil flow from the cylinder port to the tank port by moving a third valve element along a third axis between the cylinder port and the tank port, the second axis and the third axis being orthogonal to the first axis, the third axis being on a virtual plane defined by the first axis and the second axis, the load check valve having a pressure equalization function configured to control an oil supply flow rate from the first valve element to the cylinder port according to a pressure of the cylinder port, and the check valve being connected to the cylinder port via a branch oil channel branching off from an oil channel between the cylinder port and the first valve element. Hydraulic valve device according to claim 5, wherein the valve body comprises a suction safety valve configured to establish a pressure ceiling at the cylinder port by moving a fourth valve element along a fourth axis between the cylinder port and the tank port, and to allow the passage of oil from the tank port to the cylinder port when the cylinder port assumes a vacuum, wherein the fourth axis is orthogonal to the first axis and is arranged in the virtual plane, and the suction safety valve is connected to the cylinder port via a second branch oil channel branching off from the oil channel between the cylinder port and the first valve element.

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