Hydraulic pump and hydraulic motor

Abstract

To provide a hydraulic pump and a hydraulic motor, which can continuously reciprocate a piston without damaging the piston and a cylinder even if a valve fails.SOLUTION: A hydraulic pump includes: a piston; a cylinder which is configured to guide the piston in a reciprocable manner and forms a working chamber together with the piston; a pair of low pressure oil line and high pressure oil line which communicate with the working chamber; a low pressure valve which is provided in the low pressure oil line and opens / closes the low pressure oil line, the low pressure valve closing in a contraction stroke and opening in an expansion stroke; a high pressure valve which is provided in the high pressure oil line and opens / closes the high pressure oil line, the high pressure valve closing in the expansion stroke and opening in the contraction stroke; and discharge means which has a communication section allowing the working chamber to communicate with the outside of the working chamber and is configured to discharge pressure oil in the working chamber to the outside of the working chamber through the communication section when the piston is in the vicinity of a bottom dead center.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present disclosure relates to a hydraulic pump and a hydraulic motor. More specifically, the present disclosure relates to a hydraulic pump and a hydraulic motor that utilize the periodic volume change of a working chamber formed by a cylinder and a piston to convert the fluid energy of a working fluid and the rotational energy of a rotating shaft by controlling the opening and closing of a valve.

Background Art

[0002] Hydraulic machines such as hydraulic motors and hydraulic pumps that utilize the periodic volume change of a working chamber formed by a cylinder and a piston to convert the fluid energy of a working fluid and the rotational energy of a rotating shaft by controlling the opening and closing of a valve are known (see Patent Document 1). In this type of hydraulic machine, if the valve malfunctions due to biting foreign matter, the pressure in the cylinder may be maintained at a high level. When the piston reciprocates in such a state, abnormal friction may occur between the piston and the inner wall of the cylinder, and there is a risk of damage to the piston and the cylinder due to seizure.

[0003] In this regard, Patent Document 1 discloses a technique for detecting the pressure in a working chamber formed by a piston and a cylinder, and determining that an abnormality has occurred in the hydraulic machine if the detection result is different from the pressure fluctuation when the hydraulic machine is operating normally.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not disclose any technology for reciprocating the piston without causing damage such as seizure in a state where the valve is malfunctioning.

[0006] At least some embodiments of the present invention have been made in view of the above problems, and an object thereof is to provide a hydraulic pump and a hydraulic motor capable of continuously reciprocating a piston without damaging the piston or the cylinder even if the valve malfunctions.

Means for Solving the Problems

[0007] (1) The hydraulic pump according to at least one embodiment of the present invention includes a piston, a cylinder configured to guide the piston to reciprocate, and a cylinder that forms a working chamber together with the piston, a set of low-pressure oil lines and high-pressure oil lines communicating with the working chamber, and a low-pressure valve provided in the low-pressure oil line and opening and closing the low-pressure oil line. The low-pressure valve closes when in a contraction stroke in which the volume of the working chamber contracts while the piston reciprocates, and opens when in an expansion stroke in which the volume of the working chamber expands while the piston reciprocates. A high-pressure valve provided in the high-pressure oil line and opening and closing the high-pressure oil line, the high-pressure valve closing when in the expansion stroke and opening when in the contraction stroke, and a communication portion communicating the working chamber with the outside of the working chamber. When the piston is near the bottom dead center, discharge means configured to discharge the pressure oil in the working chamber to the outside of the working chamber through the communication portion.

[0008] The pressure in the working chamber changes due to the reciprocating motion of the piston, the opening and closing of the low-pressure valve, and the opening and closing of the high-pressure valve. Therefore, for example, if a failure of the low-pressure valve occurs, such as the low-pressure valve being unable to open, or a failure of the high-pressure valve occurs, such as the high-pressure valve being unable to close, even at the timing when the low-pressure valve is to be opened and the high-pressure valve is to be closed (for example, immediately before the start of the expansion stroke), the state where the low-pressure valve is closed or the state where the high-pressure valve is open may continue, and the pressure in the working chamber may be maintained at a high level. And in such a state, if the piston continuously reciprocates, the temperature of the pressure oil in the working chamber rises due to frictional heat generation between the piston and the cylinder, and there is a risk of damage to the piston and the cylinder due to seizure. According to the configuration of (1) above, the communication portion communicates the working chamber with the outside of the working chamber. And when the piston is near the bottom dead center, it is configured to discharge the pressure oil in the working chamber to the outside of the working chamber through this communication portion. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, when the piston is near the bottom dead center, the pressure oil in the working chamber is discharged to the outside of the working chamber through the communication portion, so that it is possible to prevent the pressure in the working chamber from being maintained at a high level. Thus, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, the piston can be continuously reciprocated without damaging the piston and the cylinder.

[0009] (2) In some embodiments, in one configuration described in (1) above, the communication portion is located on the bottom dead center side between the top dead center and the bottom dead center, and includes a through hole that penetrates the cylinder to communicate the working chamber with the outside of the working chamber, and the discharging means further has a first line that connects the through hole and the low-pressure oil line on the side of the low-pressure oil line that is opposite to the working chamber side from the low-pressure valve.

[0010] According to the configuration of (2) above, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, when the piston is on the bottom dead center side of the through hole during the reciprocating motion of the piston, the working chamber and the outside of the working chamber are communicated with each other through the through hole, and the pressure oil in the working chamber can be discharged to one side low-pressure oil line through the through hole and the first line. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, it is possible to prevent the pressure in the working chamber from being maintained at a high level.

[0011] (3) In some embodiments, in one configuration described in (1) above, the communication portion is formed on the inner peripheral surface of the cylinder and includes an oil groove that communicates the working chamber and the outside of the working chamber when the piston is at the bottom dead center.

[0012] According to the configuration of (3) above, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, when the piston is at the bottom dead center, the working chamber and the outside of the working chamber are communicated with each other through the oil groove, and the pressure oil in the working chamber can be discharged to the outside of the cylinder through this oil groove. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, it is possible to prevent the pressure in the working chamber from being maintained at a high level.

[0013] (4) In some embodiments, in one configuration described in (1) above, the communication portion is located on the top dead center side of the bottom dead center and includes a through hole that penetrates the cylinder and communicates the working chamber and the outside of the working chamber, and the discharging means further includes a first line that connects the through hole and the low-pressure oil line on the side opposite to the working chamber side of the low-pressure valve in the low-pressure oil line, a solenoid valve provided on the first line and opening and closing the first line, and a controller that controls the opening and closing of the solenoid valve.

[0014] According to the configuration of (4) above, when a failure of the low-pressure valve or a failure of the high-pressure valve occurs, the controller performs opening and closing control to open the solenoid valve, so that the working chamber communicates with the outside of the working chamber through the through hole, and the pressure oil in the working chamber is discharged to the low-pressure oil line (one-side low-pressure oil line) on the side opposite to the working chamber side from the low-pressure valve among the low-pressure oil lines through the through hole and the first line. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, it is possible to prevent the pressure in the working chamber from being maintained at a high level.

[0015] (5) In some embodiments, in one configuration described in (4) above, the controller performs opening and closing control of the solenoid valve to open the solenoid valve when the piston is near the bottom dead center in the expansion stroke.

[0016] According to the configuration of (5) above, immediately before the piston reaches the bottom dead center in the expansion stroke, the pressure oil in the working chamber can be discharged to the one-side low-pressure oil line described above. Therefore, it is possible to prevent the pressure in the working chamber from rising from immediately before the piston reaches the bottom dead center.

[0017] (6) In some embodiments, in one configuration described in (4) or (5) above, the controller performs opening and closing control of the solenoid valve to open the solenoid valve when the high-pressure valve is open or the low-pressure valve is closed in the expansion stroke.

[0018] In the expansion stroke, if the low-pressure valve is closed (failure of the low-pressure valve) or the high-pressure valve is open (failure of the high-pressure valve), the pressure in the working chamber may rise rapidly. According to the configuration of (6) above, when a failure of the low-pressure valve or a failure of the high-pressure valve occurs, the controller opens the solenoid valve to discharge the pressure oil in the working chamber to the one-side low-pressure oil line described above. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs in the expansion stroke, it is possible to prevent the pressure in the working chamber from rising rapidly.

[0019] (7) The hydraulic motor according to at least one embodiment of the present invention includes a piston, a cylinder configured to reciprocally guide the piston and form a working chamber together with the piston, a set of low-pressure oil lines and high-pressure oil lines communicating with the working chamber, a low-pressure valve provided in the low-pressure oil line and configured to open and close the low-pressure oil line, the low-pressure valve being configured to open when in a contraction stroke in which the volume of the working chamber contracts while the piston reciprocates and to close when in an expansion stroke in which the volume of the working chamber expands while the piston reciprocates, a high-pressure valve provided in the high-pressure oil line and configured to open and close the high-pressure oil line, the high-pressure valve being configured to open when in the expansion stroke and to close when in the contraction stroke, and discharge means having a communication portion communicating the working chamber with the outside of the working chamber and configured to discharge the pressure oil in the working chamber to the outside of the working chamber through the communication portion when the piston is near the bottom dead center.

[0020] The pressure in the working chamber changes due to the reciprocating motion of the piston, the opening and closing of the low-pressure valve, and the opening and closing of the high-pressure valve. Therefore, for example, if a failure of the low-pressure valve occurs, such as the low-pressure valve being unable to open, or a failure of the high-pressure valve occurs, such as the high-pressure valve being unable to close, a state where the low-pressure valve is closed or the high-pressure valve is open may continue regardless of the timing of opening the low-pressure valve and closing the high-pressure valve (for example, immediately before the start of the contraction stroke), and the pressure in the working chamber may be maintained at a high level. And in such a state, if the piston continuously reciprocates, the temperature of the pressure oil in the working chamber may rise due to frictional heat generation between the piston and the cylinder, and there is a risk of damage to the piston and the cylinder due to seizure. According to the configuration of (7) above, the communication part communicates the working chamber with the outside of the working chamber. And when the piston is near the bottom dead center, the pressure oil in the working chamber is configured to be discharged to the outside of the working chamber through this communication part. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, when the piston is near the bottom dead center, the pressure oil in the working chamber can be discharged to the outside of the working chamber through the communication part, so that it can be prevented that the pressure in the working chamber is maintained at a high level. Thus, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, the piston can be continuously reciprocated without damaging the piston or the cylinder.

[0021] (8) In some embodiments, in one configuration described in (7) above, the communication part is located on the bottom dead center side between the top dead center and the bottom dead center, and includes a through hole that penetrates the cylinder to communicate the working chamber with the outside of the working chamber. The discharging means further has a first line that connects the through hole and the low-pressure oil line on the side of the low-pressure oil line opposite to the working chamber side from the low-pressure valve.

[0022] According to the configuration of (8) above, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, when the piston is on the bottom dead center side of the through hole during the reciprocating motion of the piston, the working chamber is communicated with the outside of the working chamber by the through hole, and the pressure oil in the working chamber can be discharged to one-side low-pressure oil line through the through hole and the first line. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, it can be prevented that the pressure in the working chamber is maintained at a high level.

[0023] (9) In some embodiments, in one configuration described in (7) above, the communication part is formed on the inner peripheral surface of the cylinder and includes an oil groove that communicates the working chamber with the outside of the working chamber when the piston is at the bottom dead center.

[0024] According to the configuration of (9) above, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, when the piston is at the bottom dead center, the working chamber communicates with the outside of the working chamber through the oil groove, and through this oil groove, the pressure oil in the working chamber can be discharged to the outside of the cylinder. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, it is possible to prevent the pressure in the working chamber from being maintained at a high level.

[0025] (10) In some embodiments, in one configuration described in (7) above, the communication portion is located on the top dead center side with respect to the bottom dead center, and includes a through hole that penetrates the cylinder to communicate the working chamber with the outside of the working chamber. The discharging means further includes a first line that connects the through hole and the low-pressure oil line on the side opposite to the working chamber side from the low-pressure valve in the low-pressure oil line, a solenoid valve provided in the first line and configured to open and close the first line, and a controller configured to perform opening / closing control of the solenoid valve.

[0026] According to the configuration of (10) above, when a failure of the low-pressure valve or a failure of the high-pressure valve occurs, the controller performs opening / closing control to open the solenoid valve, so that the working chamber communicates with the outside of the working chamber through the through hole, and through the through hole and the first line, the pressure oil in the working chamber can be discharged to the low-pressure oil line on the side opposite to the working chamber side from the low-pressure valve in the low-pressure oil line (one-side low-pressure oil line). Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs, it is possible to prevent the pressure in the working chamber from being maintained at a high level.

[0027] (11) In some embodiments, in one configuration described in (10) above, the controller performs opening / closing control of the solenoid valve to open the solenoid valve when the piston is near the bottom dead center in the expansion stroke.

[0028] According to the configuration of (11) above, immediately before the piston reaches the bottom dead center in the expansion stroke, the pressure oil in the working chamber can be discharged to the one-side low-pressure oil line described above. Therefore, it is possible to prevent the pressure in the working chamber from rising immediately before the piston reaches the bottom dead center.

[0029] (12) In some embodiments, in one configuration described in any of the above (10) or (11), when the high-pressure valve is open or the low-pressure valve is closed during the compression stroke, the controller controls the opening and closing of the solenoid valve to open the solenoid valve.

[0030] During the compression stroke, if the low-pressure valve is closed (failure of the low-pressure valve) or the high-pressure valve is open (failure of the high-pressure valve), the pressure in the working chamber may rise rapidly. According to the configuration of the above (12), when a failure of the low-pressure valve or a failure of the high-pressure valve occurs, the controller opens the solenoid valve to discharge the pressure oil in the working chamber to the above-mentioned one-side low-pressure oil line. Therefore, even if a failure of the low-pressure valve or a failure of the high-pressure valve occurs during the compression stroke, it is possible to prevent the pressure in the working chamber from rising rapidly.

Advantages of the Invention

[0031] According to at least one embodiment of the present invention, it is possible to provide a hydraulic machine capable of continuously reciprocating the piston without damaging the piston or the cylinder even if the low-pressure valve or the high-pressure valve fails.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Modes for Carrying Out the Invention

[0033] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent a state in which there are tolerances or relative displacements with angles and distances that can obtain the same function. Also, for example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. On the other hand, the expressions "comprising", "having", "including", or "possessing" a component do not exclude the existence of other components.

[0034] FIG. 1 is a hydraulic circuit diagram of a hydraulic pump according to an embodiment of the present invention.

[0035] As shown in FIG. 1, a hydraulic pump 100 according to an embodiment of the present invention includes a piston 2, a cylinder 3, a pair of low-pressure oil lines 4 and high-pressure oil lines 5, a low-pressure valve 6, and a high-pressure valve 7.

[0036] The cylinder 3 is configured to reciprocally guide the piston 2 and forms an operating chamber 8 together with the piston 2. Each of a set of low-pressure oil lines 4 and high-pressure oil lines 5 communicates with the operating chamber 8. The low-pressure valve 6 is provided in the low-pressure oil line 4 and is a valve for opening and closing the low-pressure oil line 4. And this low-pressure valve 6 closes when in the contraction stroke in which the volume of the operating chamber 8 contracts while the piston 2 reciprocates. Also, this low-pressure valve 6 opens when in the expansion stroke in which the volume of the operating chamber 8 expands while the piston 2 reciprocates. The high-pressure valve 7 is provided in the high-pressure oil line 5 and is a valve for opening and closing the high-pressure oil line 5. And this high-pressure valve 7 closes when in the expansion stroke. Also, this high-pressure valve 7 opens when in the contraction stroke.

[0037] In the embodiment shown in FIG. 1, the hydraulic pump 100 further includes a shaft 10 and a cam 12 (eccentric cam) attached to the shaft 10 and abutting against the piston 2.

[0038] During the operation of such a hydraulic pump 100, when the shaft 10 rotates by a driving source (not shown), the cam 12 also rotates. And corresponding to the rotation of the cam 12, the opening and closing of the low-pressure valve 6 and the opening and closing of the high-pressure valve 7 are performed. And the piston 2 reciprocates periodically, for example, up and down, and a discharge process (corresponding to the contraction stroke described above) in which the piston 2 moves from the bottom dead center to the top dead center and an intake process (corresponding to the expansion stroke described above) in which the piston 2 moves from the top dead center to the bottom dead center are repeated. For this reason, the volume of the operating chamber 8 formed by the piston 2 and the cylinder 3 changes periodically.

[0039] The low-pressure oil line 4 is a passage for sending, for example, the hydraulic oil stored in the tank 14 into the working chamber 8. Such a low-pressure oil line 4 includes, as shown in FIG. 1, a one-side low-pressure oil line 4A and an other-side low-pressure oil line 4B. The one-side low-pressure oil line 4A is a passage on the side of the low-pressure oil line 4 opposite to the working chamber 8 side with respect to the low-pressure valve 6. The other-side low-pressure oil line 4B is a passage on the working chamber 8 side of the low-pressure oil line 4 with respect to the low-pressure valve 6. In the embodiment shown in FIG. 1, the cylinder 3 and the tank 14 are connected by the low-pressure oil line 4. In such a hydraulic pump 100, in the expansion process, by opening the low-pressure valve 6 and closing the high-pressure valve 7, the hydraulic oil stored in the tank 14 is sent into the working chamber 8 of the cylinder 3 through the low-pressure oil line 4.

[0040] The high-pressure oil line 5 is a passage for sending the pressurized oil in the working chamber 8 to, for example, a hydraulic motor (not shown). Such a high-pressure oil line 5 includes, as shown in FIG. 1, a one-side high-pressure oil line 5A and an other-side high-pressure oil line 5B. The one-side high-pressure oil line 5A is a passage on the side of the high-pressure oil line 5 opposite to the working chamber 8 side with respect to the high-pressure valve 7. The other-side high-pressure oil line 5B is a passage on the working chamber 8 side of the high-pressure oil line 5 with respect to the high-pressure valve 7. In such a hydraulic pump 100, in the contraction process, by closing the low-pressure valve 6 and opening the high-pressure valve 7, the pressurized oil in the working chamber 8 is sent to the hydraulic motor through the high-pressure oil line 5.

[0041] In the embodiment shown in FIG. 1, the hydraulic pump 100 further includes a relief line 16 which is a passage for connecting to the relief tank 14A (14) after a plurality (two) of one-side high-pressure oil lines 5A merge. And a relief valve 19 is provided in this relief line 16. Thereby, if the pressure in the relief line 16 on the downstream side of the relief valve 19 is greater than the pressure set in the relief valve 19, the pressurized oil in the working chamber 8 is sent to the relief tank 14A. Note that the relief tank 14A may be the above-described tank 14.

[0042] The low-pressure valve 6 is a valve (check valve) that opens and closes according to the difference in pressure between, for example, the pressure in the one-side low-pressure oil line 4A and the pressure in the other-side low-pressure oil line 4B. Alternatively, it is a valve (solenoid valve) that opens and closes according to an instruction from the controller 32 described later. The high-pressure valve 7 is a valve (check valve) that opens and closes according to the difference in pressure between, for example, the pressure in the one-side high-pressure oil line 5A and the pressure in the other-side high-pressure oil line 5B. Alternatively, it is a valve (solenoid valve) that opens and closes according to an instruction from the controller 32 described later.

[0043] Figures 2A to 2C are schematic diagrams for explaining the discharge means of the hydraulic pump according to an embodiment of the present invention. In each of Figures 2A to 2C, the state of the discharge means in the expansion stroke is illustrated. Also, the difference between the pressure in the working chamber 8 in the expansion stroke and the pressure in the working chamber 8 in the contraction stroke is represented by the difference in shading, and the pressure in the working chamber 8 in the expansion stroke is greater than the pressure in the working chamber 8 in the expansion stroke.

[0044] As shown in Figures 2A to 2C, the hydraulic pump 100 has a communication portion 20 that communicates the working chamber 8 with the outside of the working chamber 8. And when the piston 2 is near the bottom dead center, the pressure oil in the working chamber 8 is configured to be discharged to the outside of the working chamber 8 through the communication portion 20.

[0045] In the embodiment shown in Figures 2A to 2C, the cylinder 3 is a bottomed cylindrical member with one end open and the other end closed, and includes a cylindrical cylinder body 24 and a closing portion 25 that closes the other end of the cylinder body 24. The low-pressure oil line 4 is connected to the working chamber 8 through the closing portion 25. And when the low-pressure valve 6 is opened, the hydraulic oil stored in a tank 14 (not shown) is configured to be sent into the working chamber 8. The high-pressure oil line 5 is connected to the working chamber 8 through the closing portion 25. And when the high-pressure valve 7 is opened, the pressure oil is configured to be sent out from the working chamber 8.

[0046] In the embodiment shown in FIGS. 2A to 2C, the piston 2 includes a piston head 23 that slides on the inner peripheral surface 24a of the cylinder body 24, and a piston rod 22 attached to the piston head 23. In addition, as described above, in order to convert the rotational motion of the cam 12 into the reciprocating motion of the piston 2, the piston rod 22 may be in contact with the cam 12.

[0047] The pressure in the working chamber 8 changes due to the opening and closing of the low-pressure valve 6, the opening and closing of the high-pressure valve 7, and the reciprocating motion of the piston 2. Therefore, for example, as shown in FIGS. 2A to 2C, when a failure of the low-pressure valve 6 such as the low-pressure valve 6 cannot be opened, and a failure of the high-pressure valve 7 such as the high-pressure valve 7 cannot be closed occur, even at the timing of closing the high-pressure valve 7 and opening the low-pressure valve 6 (for example, immediately before the start of the expansion stroke), the state where the high-pressure valve 7 is open and the state where the low-pressure valve 6 is closed continue. For this reason, compared with the case where the low-pressure valve 6 and the high-pressure valve 7 open and close normally, the pressure in the working chamber 8 may be maintained at a high level. And in such a state, when the piston 2 continuously reciprocates, the temperature of the pressure oil in the working chamber 8 rises due to the frictional heat generation between the piston 2 and the cylinder 3, and there is a risk of damage to the piston 2 and the cylinder 3 due to seizure. In addition, in the embodiment shown in FIGS. 2A to 2C, the case where a failure of the low-pressure valve 6 where the low-pressure valve 6 does not open and a failure of the high-pressure valve 7 where the high-pressure valve 7 does not close occur is described as an example. However, even when either a failure of the low-pressure valve 6 or a failure of the high-pressure valve 7 occurs, the temperature of the pressure oil in the working chamber 8 rises due to the frictional heat generation between the piston 2 and the cylinder 3, and there is a risk of damage to the piston 2 and the cylinder 3 due to seizure. Therefore, the hydraulic pump 100 in the present disclosure has the same effect. Further, the failure of the low-pressure valve 6 is not limited to the low-pressure valve 6 not opening, and the failure of the high-pressure valve 7 is not limited to the high-pressure valve 7 not closing.

[0048] According to such a hydraulic pump 100 according to an embodiment of the present invention, the communication portion 20 communicates the working chamber 8 with the outside of the working chamber 8. When the piston 2 is near the bottom dead center, the pressure oil in the working chamber 8 is configured to be discharged to the outside of the working chamber 8 through the communication portion 20. Therefore, even if the low-pressure valve 6 or the high-pressure valve 7 fails, when the piston 2 is near the bottom dead center, the pressure oil in the working chamber 8 is discharged to the outside of the working chamber 8 through the communication portion 20, so that it is possible to prevent the pressure in the working chamber 8 from being maintained at a high level. Thus, even if the low-pressure valve 6 or the high-pressure valve 7 fails, the piston 2 can be continuously reciprocated without damaging the piston 2 or the cylinder 3.

[0049] In some embodiments, as shown in FIG. 2A, the communication portion 20 includes a through hole 20A1 (20) that penetrates the cylinder 3 to communicate the working chamber 8 with the outside of the working chamber 8. The through hole 20A1 is located on the bottom dead center side between the top dead center and the bottom dead center. As shown in FIG. 2A, the hydraulic pump 100 further has a first line 21 that is a passage connecting the through hole 20A1 and the one-side low-pressure oil line 4A.

[0050] In the embodiment shown in FIG. 2A, the through hole 20A1 is a hole that penetrates the cylinder body 24 to communicate the working chamber 8 with the outside of the working chamber 8. When the distance from the bottom dead center to the top dead center is h, the center of the through hole 20A1 is formed at a position where the distance from the bottom dead center is h / 2 or less (on the bottom dead center side between the top dead center and the bottom dead center). Therefore, in the reciprocating motion of the piston 2, the timing when the working chamber 8 and the outside of the working chamber 8 are not communicated by the piston head 23 and the timing when the working chamber 8 and the outside of the working chamber 8 are communicated are included. In particular, the through hole 20A1 is formed at a position where the center thereof is at a distance of h / 5 or less from the bottom dead center. Therefore, for example, between immediately before the end of the expansion stroke and immediately after the start of the contraction stroke, the working chamber 8 and the outside of the working chamber 8 are communicated, and the pressure oil in the working chamber 8 is discharged to the one-side low-pressure oil line 4A. Furthermore, the pressure oil discharged to the one-side low-pressure oil line 4A through the first line 21 may be sent back toward the working chamber 8 again, or may be returned to a tank 14 (not shown).

[0051] According to such a configuration, even if a failure of the low-pressure valve 6 or a failure of the high-pressure valve 7 occurs, when the piston head 23 of the piston 2 is on the bottom dead center side from the through hole 20A1 in the reciprocating motion of the piston 2, the through hole 20A1 communicates the working chamber 8 with the outside of the working chamber 8, and the pressure oil in the working chamber 8 can be discharged to the one-side low-pressure oil line 4A through the through hole 20A1 and the first line 21. Therefore, even if a failure of the low-pressure valve 6 or a failure of the high-pressure valve 7 occurs, it is possible to prevent the pressure in the working chamber 8 from being maintained at a high level.

[0052] In some embodiments, as shown in FIG. 2B, the communication portion 20 includes an oil groove 20B (20) formed on the inner peripheral surface of the cylinder 3. And this oil groove 20B communicates the working chamber 8 with the outside of the working chamber 8 when the piston 2 is at the bottom dead center.

[0053] In the embodiment shown in FIG. 2B, the oil groove 20B is a groove formed on the inner peripheral surface 24a of the cylinder body 24. Such an oil groove 20B, when the piston 2 is at the bottom dead center, one end 20B1 of the oil groove 20B located on the working chamber 8 side is located on the working chamber 8 side from the piston head 23. And the other end 20B2 of the oil groove 20B located on the side opposite to the working chamber 8 side is located on the side opposite to the working chamber 8 side from the piston head 23. Therefore, the oil groove 20B communicates the working chamber 8 with the outside of the working chamber 8 when the piston 2 is at the bottom dead center. Furthermore, in the embodiment shown in FIG. 2B, the hydraulic pump 100 further has a discharge line 27 which is a passage connecting the oil groove 20B and the tank 14.

[0054] Further, the oil groove 20B is formed on the inner peripheral surface 24a of the cylinder body 24 such that the position of one end 20B1 of the oil groove 20B is h / 2 or less from the bottom dead center. In particular, the oil groove 20B is formed on the inner peripheral surface 24a of the cylinder body 24 such that the position of one end 20B1 of the oil groove 20B is h / 5 or less from the bottom dead center.

[0055] According to such a configuration, even if the low-pressure valve 6 or the high-pressure valve 7 fails, when the piston 2 is at the bottom dead center, the oil groove 20B allows the working chamber 8 to communicate with the outside of the working chamber 8, and through this oil groove 20B, the pressure oil in the working chamber 8 can be discharged to the outside of the cylinder 3. Therefore, even if the low-pressure valve 6 or the high-pressure valve 7 fails, it is possible to prevent the pressure in the working chamber 8 from being maintained at a high level.

[0056] In some embodiments, as shown in FIG. 2C, the communication portion 20 includes a through hole 20A2 (20) that penetrates the cylinder 3 to communicate the working chamber 8 with the outside of the working chamber 8. And this through hole 20A2 is located on the upper dead center side from the bottom dead center. And as shown in FIG. 2C, the hydraulic pump 100 further includes the above-described first line 21, a solenoid valve 30 provided in this first line 21 and opening and closing this first line 21, and a controller 32 that controls the opening and closing of the solenoid valve 30.

[0057] In the embodiment shown in FIG. 2C, the through hole 20A2 is a hole that penetrates the cylinder body 24 to communicate the working chamber 8 with the outside of the working chamber 8. If such a through hole 20A2 is formed on the upper dead center side from the bottom dead center, the working chamber 8 communicates with the outside of the working chamber 8 regardless of the position of the piston 2. And when the solenoid valve 30 is opened, the pressure oil in the working chamber 8 is discharged to the one-side low-pressure oil line 4A. In addition, the pressure oil discharged to the one-side low-pressure oil line 4A through the first line 21 may be sent back into the working chamber 8 again, or may be returned to a tank 14 (not shown). Also, although not shown, the communication portion 20 may include a through hole that penetrates the closing portion 25 to communicate the working chamber 8 with the outside of the working chamber 8.

[0058] The solenoid valve 30 is a valve that opens and closes the first line 21 in response to an instruction from the controller 32.

[0059] The controller 32 is a device composed of, for example, a central processing unit including a processor, a random access memory, a read-only memory, and an I / O interface. Such a controller 32 issues an instruction to open or close the solenoid valve 30 based on the result of executing a program (for example, a program that compares the pressure in the working chamber 8 with the set pressure set by the controller 32) stored in the read-only memory by the central processing unit.

[0060] According to such a configuration, when a failure occurs in the low-pressure valve 6 or the high-pressure valve 7, the controller 32 controls the opening and closing of the solenoid valve 30 so as to open the solenoid valve 30, whereby the working chamber 8 and the outside of the working chamber 8 are communicated with each other through the through hole 20A2, and the pressure oil in the working chamber 8 can be discharged to the one-side low-pressure oil line 4A through the through hole 20A2 and the first line 21. Therefore, even when a failure occurs in the low-pressure valve 6 or the high-pressure valve 7, it is possible to prevent the pressure in the working chamber 8 from being maintained at a high level.

[0061] In some embodiments, the controller 32 controls the opening and closing of the solenoid valve 30 so as to open the solenoid valve 30 when the piston 2 is near the bottom dead center in the expansion stroke.

[0062] In the embodiment shown in FIG. 2C, a piston position measuring device 34 is attached to the piston rod 22. This piston position measuring device 34 is a device for measuring the position of the piston 2 while the piston 2 reciprocates. Then, the position of the piston 2 measured by the piston position measuring device 34 is converted into, for example, an electrical signal and transmitted to the controller 32. Such a controller 32 controls the opening and closing of the solenoid valve 30 so as to open the solenoid valve 30 when the position of the piston head 23 measured by the piston position measuring device 34 is, for example, at h / 5 or less from the bottom dead center in the expansion stroke.

[0063] According to such a configuration, just before the piston 2 reaches the bottom dead center in the expansion stroke, the pressure oil in the working chamber 8 can be discharged to the above-described one-side low-pressure oil line 4A. Therefore, it is possible to prevent the pressure in the working chamber 8 from rising just before the piston 2 reaches the bottom dead center.

[0064] In some embodiments, when the high-pressure valve 7 is open or the low-pressure valve 6 is closed in the expansion stroke, the controller 32 controls the opening and closing of the solenoid valve 30 so as to open the solenoid valve 30.

[0065] In the embodiment shown in FIG. 2C, the hydraulic pump 100 further includes a low-pressure valve failure detection device 36 and a high-pressure valve failure detection device 37. The low-pressure valve failure detection device 36 is a device that detects whether a failure has occurred in the low-pressure valve 6, for example, by detecting the opening degree of the low-pressure valve 6. When it is detected by the low-pressure valve failure detection device 36 that a failure has occurred in the low-pressure valve 6 (the low-pressure valve 6 is closed) in the expansion stroke, for example, an electrical signal is transmitted to the controller 32. Then, when the controller 32 receives the electrical signal from the low-pressure valve failure detection device 36, the controller 32 controls the opening and closing of the solenoid valve 30 so as to open the solenoid valve 30.

[0066] The high-pressure valve failure detection device 37 is a device that detects whether a failure has occurred in the high-pressure valve 7, for example, by detecting the opening degree of the high-pressure valve 7. When it is detected by the high-pressure valve failure detection device 37 that a failure has occurred in the high-pressure valve 7 (the high-pressure valve 7 is open) in the expansion stroke, for example, an electrical signal is transmitted to the controller 32. Then, when the controller 32 receives the electrical signal from the high-pressure valve failure detection device 37, the controller 32 controls the opening and closing of the solenoid valve 30 so as to open the solenoid valve 30.

[0067] During the expansion stroke, if the low-pressure valve 6 is closed (failure of the low-pressure valve 6) or the high-pressure valve 7 is open (failure of the high-pressure valve 7), there is a risk that the pressure in the working chamber 8 will rise rapidly. According to such a configuration, when a failure of the low-pressure valve 6 or a failure of the high-pressure valve 7 occurs, the controller 32 can open the solenoid valve 30 to discharge the pressure oil in the working chamber 8 to the above-mentioned one-side low-pressure oil line 4A. Therefore, even if a failure of the low-pressure valve 6 or a failure of the high-pressure valve 7 occurs during the expansion stroke, it is possible to prevent the pressure in the working chamber 8 from rising rapidly.

[0068] Also, in some embodiments, although not shown, the hydraulic pump 100 may further include a pressure sensor that detects the pressure in the working chamber 8. According to such a configuration, when the detected value detected by the pressure sensor is greater than, for example, a set value (for example, a value at which seizure occurs) preset in the controller 32, it is presumed that a failure of the low-pressure valve 6 or a failure of the high-pressure valve 7 has occurred. And in such a case, by controlling the opening and closing of the solenoid valve 30 so that the controller 32 opens the solenoid valve 30, the pressure in the working chamber 8 can be reduced.

[0069] Next, in the hydraulic motor 200 according to an embodiment of the present invention, for the same configuration as the hydraulic pump 100, the same reference numerals are given and the description thereof is omitted, and the differences from the hydraulic pump 100 will be described.

[0070] As shown in FIG. 3, the hydraulic motor 200 according to an embodiment of the present invention includes a low-pressure valve 56 that is provided in the low-pressure oil line 4 and opens and closes the low-pressure oil line 4, and opens when in the contraction stroke and closes when in the expansion stroke, and a high-pressure valve 57 that is provided in the high-pressure oil line 5 and opens and closes the high-pressure oil line 5, and opens when in the expansion stroke and closes when in the contraction stroke.

[0071] In the embodiment shown in FIG. 3, the low-pressure oil line 4 is a passage for sending the pressure oil in the working chamber 8 to, for example, a tank 14 (not shown). The high-pressure oil line 5 is a passage for sending the pressure oil sent from, for example, a hydraulic pump 100 into the working chamber 8.

[0072] In some embodiments, the controller 32 of the hydraulic motor 200 controls the opening and closing of the solenoid valve 30 so as to open the solenoid valve 30 when the high-pressure valve 57 is open or the low-pressure valve 56 is closed during the contraction stroke.

[0073] According to the hydraulic motor 200 according to an embodiment of the present invention, even if a failure of the low-pressure valve 56 or a failure of the high-pressure valve 57 occurs, the pressure oil in the working chamber 8 is discharged to the outside of the working chamber 8 through the communication portion 20, so that it is possible to prevent the pressure in the working chamber 8 from being maintained at a high level. Therefore, even if a failure of the low-pressure valve 56 or a failure of the high-pressure valve 57 occurs, the piston 2 can be continuously reciprocated without damaging the piston 2 or the cylinder 3.

[0074] As described above, the hydraulic pump and the hydraulic motor according to an embodiment of the present invention have been described. However, the present invention is not limited to the above-described form, and various modifications can be made without departing from the object of the present invention.

Explanation of Reference Numerals

[0075] 2 Piston 3 Cylinder 4 Low-pressure oil line 4A One-side low-pressure oil line 4B The other-side low-pressure oil line 5 High-pressure oil line 5A One-side high-pressure oil line 5B The other-side high-pressure oil line 6 Low-pressure valve 7 High-pressure valve 8 Working chamber 10 Shaft 12 Cam 14 Tank 14A Relief tank 16 Relief line 19 Relief valve 20 Communication part 20A1 Through-hole 20A2 Through-hole 20B Oil groove 21 First line 22 Piston rod 23 Piston head 24 Cylinder body 24a Inner peripheral surface of the cylinder body 25 Closing part 27 Discharge line 30 Solenoid valve 32 Controller 34 Piston position measuring device 36 Low-pressure valve failure detection device 37 High-pressure valve failure detection device 100 Hydraulic pump 200 Hydraulic motor

Claims

1. A piston, a cylinder configured to reciprocally guide the piston and forming a working chamber together with the piston, a set of low-pressure oil lines and high-pressure oil lines communicating with the working chamber, a low-pressure valve provided in the low-pressure oil line and opening and closing the low-pressure oil line, a low-pressure valve that closes when in a contraction stroke in which the volume of the working chamber contracts while the piston reciprocates, and opens when in an expansion stroke in which the volume of the working chamber expands while the piston reciprocates, a high-pressure valve provided in the high-pressure oil line and opening and closing the high-pressure oil line, a high-pressure valve that closes when in the expansion stroke and opens when in the contraction stroke, a hydraulic pump comprising discharge means having a communication portion communicating the working chamber with the outside of the working chamber, and configured to discharge the pressure oil in the working chamber to the outside of the working chamber through the communication portion when the piston is near the bottom dead center.

2. The communication portion is located on the bottom dead center side between the top dead center and the bottom dead center, and includes a through hole penetrating the cylinder to communicate the working chamber with the outside of the working chamber, The hydraulic pump according to claim 1, wherein the discharge means further has a first line connecting the through hole and the low-pressure oil line on the side opposite to the working chamber side from the low-pressure valve in the low-pressure oil line.

3. The hydraulic pump according to claim 1, wherein the communication portion is formed on the inner peripheral surface of the cylinder and includes an oil groove that communicates the working chamber with the outside of the working chamber when the piston is at the bottom dead center.

4. The communication portion is located on the top dead center side from the bottom dead center, and includes a through hole penetrating the cylinder to communicate the working chamber with the outside of the working chamber, The discharge means includes a first line connecting the through hole and the low-pressure oil line on the side opposite to the working chamber side from the low-pressure valve in the low-pressure oil line, a solenoid valve provided in the first line and opening and closing the first line, The hydraulic pump according to claim 1, further comprising a controller for opening and closing control of the solenoid valve.

5. The hydraulic pump according to claim 4, wherein the controller opens and closes the solenoid valve so as to open the solenoid valve when the piston is near the bottom dead center in the expansion stroke.

6. The hydraulic pump according to claim 4 or 5, wherein the controller controls the opening and closing of the solenoid valve so as to open the solenoid valve when the high-pressure valve is open or the low-pressure valve is closed during the expansion stroke.

7. A piston, a cylinder configured to guide the piston to reciprocate and forming a working chamber together with the piston, a set of low-pressure oil lines and high-pressure oil lines communicating with the working chamber, a low-pressure valve provided in the low-pressure oil line and opening and closing the low-pressure oil line, a low-pressure valve that opens when the piston is in a contraction stroke in which the volume of the working chamber contracts while the piston reciprocates, and closes when the piston is in an expansion stroke in which the volume of the working chamber expands while the piston reciprocates, a high-pressure valve provided in the high-pressure oil line and opening and closing the high-pressure oil line, a high-pressure valve that opens during the expansion stroke and closes during the contraction stroke, a hydraulic motor comprising discharge means having a communication portion communicating the working chamber with the outside of the working chamber, and configured to discharge the pressure oil in the working chamber to the outside of the working chamber through the communication portion when the piston is near the bottom dead center.

8. The communication portion is located on the bottom dead center side between the top dead center and the bottom dead center, and includes a through hole that penetrates the cylinder and communicates the working chamber with the outside of the working chamber, The hydraulic motor according to claim 7, wherein the discharge means further has a first line connecting the through hole and the low-pressure oil line on the side of the low-pressure oil line opposite to the working chamber side with respect to the low-pressure valve.

9. The hydraulic motor according to claim 7, wherein the communication portion is formed on the inner peripheral surface of the cylinder and includes an oil groove that communicates the working chamber with the outside of the working chamber when the piston is at the bottom dead center.

10. The communication portion is located on the top dead center side with respect to the bottom dead center, and includes a through hole that penetrates the cylinder and communicates the working chamber with the outside of the working chamber, The hydraulic motor according to claim 7, wherein the discharge means includes a first line connecting the through hole and the low-pressure oil line on the side of the low-pressure oil line opposite to the working chamber side with respect to the low-pressure valve, a solenoid valve provided in the first line and opening and closing the first line, and a controller that controls the opening and closing of the solenoid valve.

11. The hydraulic motor according to claim 10, wherein the controller controls opening and closing of the solenoid valve so as to open the solenoid valve when the piston is near the bottom dead center in the expansion stroke.

12. The hydraulic motor according to claim 10 or 11, wherein the controller controls opening and closing of the solenoid valve so as to open the solenoid valve when the high-pressure valve is open or the low-pressure valve is closed in the contraction stroke.

Images