JP4542473B2 - Valve plate and hydraulic device including the same - Google Patents

Description

  The present invention relates to a hydraulic device that can be suitably implemented, for example, as a piston pump and a piston motor, and more particularly to a valve plate provided in the hydraulic device.

  FIG. 7 is a front view showing a valve plate 2 of a conventional piston pump. FIG. 8 is a cross-sectional view showing a part of the piston pump as viewed from the section line S8-S8 in FIG. FIG. 8 shows a developed arc-shaped cross section extending in the circumferential direction. The piston pump includes a cylinder block 5 provided to be rotatable in the rotation direction A1 around the axis L1. A plurality of piston chambers 6 are formed in the cylinder block 5, and cylinder ports 7 communicating with the respective piston chambers 6 are respectively formed. A piston 8 is fitted in each piston chamber 6. A shoe is provided at one end of each piston, and each shoe is pressed toward a swash plate inclined with respect to a virtual plane perpendicular to the axis L1. Accordingly, each piston 8 is reciprocally displaced in synchronization with the rotation of the cylinder block 5 with an extension stroke and a contraction stroke.

  The valve plate 2 is slidably provided on the cylinder block 4. The valve plate 2 is formed with a suction port 3 communicating with the oil source and a discharge port 4 communicating with the actuator. The suction port 3 is formed so as to be connected via a cylinder port 7 to a piston chamber 6 into which a piston 8 in an extension stroke is fitted. The discharge port 4 is formed so as to be connected via a cylinder port 7 to a piston chamber 6 into which a piston 8 in a contracting stroke is fitted. When the cylinder block 5 is rotationally driven by a drive source, each piston 8 is reciprocally displaced, and the piston pump sucks and discharges hydraulic oil from the oil source, and supplies the hydraulic oil to the actuator for driving. it can.

  When the connection destination of the cylinder port 7 is switched from the discharge port 4 to the suction port 3, when the cylinder port 7 is connected to both the suction port 3 and the discharge port 4, a backflow of hydraulic oil occurs. In this state, when the opening area of the suction port 3 is large, the flow rate of the reverse flow from the discharge port 4 to the suction port 3 is large, so that the pump efficiency is lowered, and the pressure fluctuation speed of the piston chamber 6 is large, so that vibration occurs. Increase. In addition, when the opening area of the suction port 3 is small, the flow speed of the working oil flowing backward increases when the pressure difference between the cylinder port 7 and the suction port 3 is large with respect to the small opening area, and a large noise is generated as a jet flow. In addition, the valve plate 2 and the cylinder port 7 may be eroded. When the suction port 3 and the discharge port 4 are not connected by the cylinder port 7, the hydraulic oil in the piston chamber 6 is compressed by the piston 8 after the discharge port 4 and the cylinder port 7 are shut off, and the pressure of the hydraulic oil Since it is connected to the suction port 3 in a state where the air pressure becomes high, a larger noise is generated and the valve plate 2 and the cylinder port 7 are significantly eroded.

  In order to reduce this noise and erosion, the valve plate 2 is formed with a notch 10 extending from the suction port 3 to the upstream side in the rotational direction A1 of the cylinder block 5. By forming this notch 10, when the cylinder port 7 is connected to the suction port 3, the initial connection is configured to be connected with a small opening area, and hydraulic oil from the piston chamber 6 to the suction port 3 is configured. Can be suppressed.

  In another conventional technique, instead of the notch 10, a pressure-removing hole 11 that is drain-connected so as to be discharged into the casing of the hydraulic pump with an interval upstream of the suction port 3 in the rotation direction A1 is provided. Is formed. The decompression hole 11 discharges the hydraulic oil in the piston chamber 6 to the space in the casing in which the cylinder block 5 is housed instead of the suction port 3, so that the cylinder port 7 is connected to the suction port 3. The pressure of the hydraulic oil in the piston chamber 6 is reduced. As a result, the jet of hydraulic oil from the piston chamber 6 to the suction port 3 can be suppressed.

  Furthermore, the structure which forms both the notch 10 and the pressure-removal hole 11 is known. For example, Patent Documents 1 and 2 show a valve plate 2 having a notch 10 and a pressure release hole 11.

Japanese Examined Patent Publication No. 61-45073 Japanese Utility Model Publication No. 58-6970

  FIG. 9 is a graph showing the dynamic characteristics of a conventional piston pump over one stroke, focusing on one piston 8. FIG. 10 is a graph showing the dynamic characteristics of a conventional piston pump in a state where the piston is in the vicinity of the position where the piston is most retracted, focusing on one piston 8. 9 and 10 show dynamic characteristics of a configuration in which the notch 10 and the pressure release hole 11 connected to the drain on the upstream side of the notch 10 are formed. In FIG. 9, the horizontal axis indicates the cylinder port position, and the vertical axis indicates the flow rate of hydraulic oil and the piston chamber pressure. In FIG. 10, the horizontal axis indicates the cylinder port position, and the vertical axis indicates the piston chamber pressure and the opening area. The cylinder port position is an angular position, the angular position where the piston 8 is at the most extended position is 0 degree, and the angular position where the piston 8 is at the most contracted position is 180 degrees. The flow rate discharged from the piston chamber 6 is positive. The piston chamber pressure is the pressure of the hydraulic oil in the piston chamber 6. The opening area is the opening area of the cylinder port 7.

  In FIG. 9, the broken line 12 indicates the piston chamber pressure, the alternate long and short dash line 13 indicates the flow rate of the hydraulic oil flowing down the discharge port 4, the double dotted line 14 indicates the flow rate of the hydraulic oil flowing down the suction port 3, and a solid line. 15 shows the flow rate of the hydraulic oil flowing down the pressure release hole 11. In FIG. 10, the dotted line 16 indicates the piston chamber pressure, the solid line 17 indicates the opening area with respect to the discharge port 4, and the broken line 18 indicates the opening area with respect to the suction port 3 and the decompression hole 11.

  In a configuration in which only one vent hole 11 is formed, the opening area is constant even when the cylinder port is displaced. Therefore, even when trying to employ a variable displacement pump, an optimum pressure drop rate can be obtained. It is difficult to form a pressure hole. More specifically, when the capacity is large, the pressure drop amount of the piston chamber 6 due to the extension of the piston 8 is large, and when the capacity is small, the pressure drop amount of the piston chamber 6 due to the extension of the piston 8 is small. Therefore, the pressure release hole 11 suitable for operation with a large capacity is a hole with a small inner diameter, and when the piston chamber 6 is connected to the suction port 3 when operating with a small capacity, The pressure of the hydraulic oil cannot be sufficiently reduced, and the jet flow to the suction port 3 cannot be prevented. On the contrary, the pressure release hole 11 suitable for operation with a small capacity becomes a hole with a large inner diameter, and when operating with a large capacity, the pressure fluctuation speed of the piston chamber 6 becomes large, so that vibration is increased. Such jets and vibrations lead to noise and erosion of the valve plate 2 and the cylinder port 7, and in particular, jets to the suction port 3 may lead to adverse effects such as an increase in noise.

  In the configuration in which only the notch 10 is formed, it is possible to change the opening area by the displacement of the cylinder port 7, which is optimal in a wide capacity range as compared with the case where only one pressure release hole 11 is formed. It is easy to form so as to obtain a pressure drop speed, and since the hydraulic oil returns to the suction port 3, the drain flow rate can be reduced, but the jet flow to the suction port 3 through the notch 10 can be prevented. I can't.

  Further, even if the notch 10 and the pressure release hole 11 are combined, the mutual defects cannot be compensated for, and a jet is generated as indicated by the reference numeral 14a in the two-dot chain line 14 in FIG. Resulting in.

  An object of the present invention is to provide a valve plate that is highly efficient and that can suppress noise, and a hydraulic device including the valve plate.

The present invention relates to a rotating shaft, a cylinder block integrally connected to the rotating shaft and formed with a plurality of piston chambers at intervals in the circumferential direction, and an extension stroke and a retract stroke in each piston chamber as the cylinder block rotates. And a plurality of pistons that are reciprocally displaced, a discharge port connected to a piston chamber in which a piston in a contracting stroke is fitted, and a suction port connected to a piston chamber in which a piston in an extending stroke is fitted A hydraulic pressure plate comprising: a valve plate formed with an area change slowing means for smoothening a change in the opening area in order to slow down a rapid pressure fluctuation in the piston chamber when the piston chamber is connected to at least the suction port; A valve plate provided in the apparatus,
When shifting from the contraction stroke to the extension stroke with the movement of the piston chamber, there is no notch in the portion that starts the opening of the suction port , and there are two or more decompression holes at intervals, and the piston The pressure release hole on the upstream side in the movement direction of the chamber communicates with the drain discharge location, and the pressure release hole on the downstream side in the movement direction of the piston chamber has a bent portion in the middle of the flow path and communicates with the suction port It is a valve plate.

  According to the present invention, in the hydraulic device, the piston is reciprocally displaced with the rotation of the cylinder block, the working liquid is sucked from the suction port, and discharged from the discharge port. This hydraulic device can be used as a hydraulic pump by rotating the cylinder block with a separately provided motor so that the working liquid is sucked from the suction port and discharged from the discharge port. Also, a hydraulic motor is constructed by supplying high-pressure working fluid from a hydraulic pressure source provided separately on the discharge port side with the suction port as the discharge port and the discharge port as the suction port, and taking out the rotation of the cylinder block. Can be used as

  The valve plate has two or more pressure-removing holes spaced from each other at the portion where the opening of the suction port starts when shifting from the contraction stroke to the extension stroke as the piston chamber moves. As a result, before the piston chamber is directly connected to the suction port, the working liquid in the piston chamber can be sufficiently discharged through the respective pressure release holes. In addition, by forming two or more pressure-removing holes, the piston chamber is connected to the suction port after preventing a jet flow from occurring in the pressure-removing hole, regardless of whether it is a constant capacity type or a variable capacity type. Before, the pressure of the working fluid in the piston chamber can be reduced to a pressure at which no jet flow occurs when the piston chamber is connected to the suction port. Therefore, the valve plate can prevent the working liquid in the piston chamber from being discharged as a jet, prevent noise, and prevent erosion of the valve plate.

Furthermore, the pressure release hole on the upstream side in the movement direction of the piston chamber, which is more likely to generate a jet flow than the pressure release hole on the downstream side in the movement direction of the piston chamber, communicates with the discharge place, and even if a jet flow should occur, Can be prevented from flowing into the suction port. As a result, noise and vibration can be prevented. The pressure release hole on the downstream side in the moving direction of the piston chamber has a bent portion in the middle of the flow path and communicates with the suction port, so that the drain flow rate can be reduced. This can increase the efficiency.

  In addition, the present invention provides a pressure relief hole on the downstream side in the movement direction of the piston chamber rather than a pressure relief hole on the upstream side in the movement direction of the piston chamber so that no jet flow is generated when the piston chamber is directly connected to the suction port. It has a large opening area.

  According to the present invention, the opening area of the pressure release hole on the upstream side in the moving direction of the piston chamber is reduced, the jet flow of the pressure release hole on the upstream side is surely prevented, and the working fluid in the piston chamber is discharged to reduce the pressure. Can be reduced. In such a state that the pressure of the working fluid in the piston chamber is reduced by the upstream side pressure release hole, the piston chamber is connected to the suction port by the pressure release hole on the downstream side in the movement direction of the piston chamber. By increasing the amount of the working liquid discharged from the chamber, the pressure of the working liquid in the piston chamber can be greatly reduced. Therefore, it is possible to reliably prevent the jet flow of each pressure release hole and the jet flow to the suction port. In addition, the drain flow rate can be kept small, and the pump efficiency can be increased.

Moreover, this invention is a hydraulic apparatus characterized by including the said valve plate.
According to the present invention, a suitable hydraulic device with low noise can be obtained.

According to the present invention, there is no notch, two or more pressure release holes are formed, and the working fluid in the piston chamber is discharged as a jet regardless of whether it is a constant capacity type or a variable capacity type. Can be prevented, noise can be prevented, and erosion of the valve plate can be prevented. Further, the upstream pressure release hole where the jet flow is likely to occur is connected to the discharge place, and even if a jet flow is generated, the jet flow can be prevented from flowing into the suction port and pulsation can be prevented. Further, the downstream pressure release hole has a bent portion in the middle of the flow path and is connected to the suction port, so that the drain flow rate can be reduced and the efficiency can be increased.

Further, according to the present invention, it is possible to reliably prevent the jet flow of each decompression hole and the jet flow to the suction port. In addition, the drain flow rate can be kept small, and the pump efficiency can be increased.
Moreover, according to this invention, the suitable hydraulic apparatus with low noise can be obtained.

  FIG. 1 is a front view showing a valve plate 21 of a piston pump 20 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the piston pump 20. FIG. 1 shows the valve plate 21 when viewed from the cylinder block 22 side on the left side of FIG. The piston pump 20 which is a hydraulic device is a variable displacement swash plate hydraulic pump provided in, for example, an industrial machine and a construction machine. The piston pump 20 is driven by a driving force from a prime mover and supplies hydraulic oil as a working liquid to the industrial machine. And used to drive an actuator provided to a construction machine. The piston pump 20 basically includes a valve plate 21, a cylinder block 22, a plurality of pistons 23, a plurality of shoes 24, and a swash plate 25, which are further provided in the casing of the piston pump 20. 26. The casing 26 includes a casing body 26a, a front cover 26b, and a valve casing 26c.

  The piston pump 20 further includes a rotating shaft 27. The rotating shaft 27 is connected to the front cover 26b via the first bearing 29 in a state where the axial end portion 27a partially protrudes from the front cover 26b. It is rotatably supported around a rotation axis L20 that coincides with the axis. In addition, the other end 27b in the axial direction of the rotating shaft 27 is supported by the valve casing 26c via the second bearing 30 so as to be rotatable around the rotating axis L20. The rotating shaft 27 is rotatable in the rotation direction A20.

  The valve plate 21 is generally disc-shaped, and is arranged coaxially with the rotary shaft 27 in a state where the rotary shaft 27 is inserted, and is fixed to the valve casing 26c. The valve plate 21 is formed with a suction port 31, a discharge port 32, and a pressure release port 33. The suction port 31 and the discharge port 32 are formed in an arc shape extending in the circumferential direction at a position shifted about 180 degrees around the rotation axis L20.

  The decompression port 33 is formed near the suction port 31 and at a position spaced from the suction port 31 on the upstream side in the rotational direction A20 of the rotation shaft 27. The decompression port 33 has a plurality of, in the present embodiment, two decompression holes 34 and 35, and the respective decompression holes 34 and 35 are formed at intervals in the rotation direction A <b> 20 of the rotary shaft 27. ing. The valve plate 21 is formed with a notch 36 extending from the discharge port 32 to the upstream side in the rotational direction A20 of the rotary shaft 27. In FIG. 2, the position of the suction port 31 is shifted in the circumferential direction for easy understanding.

  The cylinder block 22 is provided on the rotating shaft 27 in a state where the rotating shaft 27 is coaxially inserted and, for example, splined to prevent mutual rotation, and can be rotated around the rotating axis L20. In the cylinder block 22, a plurality of piston chambers 37 are formed at equal intervals in the circumferential direction, and cylinder ports 38 individually connected to the piston chambers 37 are formed at equal intervals in the circumferential direction. . Each piston chamber 37 has an axis substantially parallel to the rotation axis L <b> 20 and opens at one end in the axial direction of the cylinder block 22. Each cylinder port 38 opens at the other end in the axial direction of the cylinder block 22. The cylinder block 22 is provided in a state in which the other end in the axial direction is in contact with the valve plate 21 so as to achieve a seal between each other and to be slidable, and each cylinder port 38 according to the angular position of the cylinder block 22. Are connected to the suction port 31, the discharge port 32 and the pressure release port 33.

  Each piston 23 is generally cylindrical, and is partially fitted and accommodated in each piston chamber 37 of the cylinder block 22 in a state where a mutual seal is achieved, thereby forming a hydraulic chamber 41. Each piston 23 is provided so as to be capable of reciprocating displacement with respect to the cylinder block 22 along the axis. The reciprocating displacement of each piston 23 includes an extension stroke that is displaced in the extension direction and a contraction stroke that is displaced in the reduction direction. Due to the displacement of each piston 23, the volume of each hydraulic chamber 41 changes. The outer end surface 43 of each piston 23 on the side protruding from the piston chamber 37 has a spherical outer surface.

  Each shoe 24 has a flange portion 45 in which a contact surface 44 perpendicular to the axis is formed at one end in the axial direction, and a fitting portion 46 opened at the other end in the axial direction. The inner surface of the fitting portion 46 of each shoe 24 is formed in a spherical shape, and the one end portion 33 in the axial direction of the piston 23 is fitted into this fitting portion 46, and each shoe 24 is connected to the fitting portion 46 and the above-described one. With the center of the one end portion 43 as the center of rotation, the piston 23 is connected to the piston 23 so as to be rotatable around three orthogonal axes independently and in combination.

  The swash plate 25 is provided on one end side in the axial direction of the cylinder block 22 and has a flat support surface 47 that receives and supports the contact surface 44 of each shoe 24. The swash plate 25 is provided so as to be tiltable about a tilt axis extending in a direction different from the rotation axis L20, in this embodiment, about a tilt axis L25 orthogonal to the rotation axis L20. Then, it is tilted around the tilt axis L25, and the angle formed with respect to the rotation axis L20 of the support surface 47 is changed. The servo mechanism 48 is provided on the upper portion of the casing 26, for example.

  The piston pump 20 further includes a pressing member 51. A spherical bush 50 having a spherical outer surface is formed on the rotary shaft 27 at a portion closer to the one end portion 27 a in the axial direction than the cylinder block 22. The center of the sphere formed by the outer surface of the spherical bush 50 coincides with one point on the rotation axis L20, in the present embodiment, the intersection of the rotation axis L20 and the tilt axis L25, and the outer surface of the spherical bush 50 is the pressing member. It becomes a guide surface for guiding 51.

  The pressing member 51 is supported by the guide surface of the spherical bush 50, and is independently and assembled around three orthogonal axes with the center of the sphere formed by the guide surface, and thus the intersection of the rotation axis L20 and the tilt axis L25 as the rotation center. It is provided so that it can rotate together. The pressing member 51 engages the flange portion 45 of each shoe 24 and presses each shoe 24 toward the support surface 47 of the swash plate 25. In this state, each shoe 24 is allowed to be slightly displaced with respect to the pressing member 51 in the direction along the support surface 47 of the swash plate 25.

  The piston pump 20 is configured such that each piston 23 reciprocates once for one rotation of the cylinder block 22. The reciprocating motion of each piston 23 has the most extended position and the most retracted position that are most retracted at angular positions of 180 degrees in the circumferential direction around the rotation axis L20. Specifically, the most extended position and the most retracted position exist at an angular position where the imaginary plane including the rotation axis L20 and perpendicular to the tilting axis L22 matches the axis of the piston 23. In the reciprocating displacement of the piston 23, the stroke from the most extended position to the most retracted position is the contraction stroke, and the stroke from the most retracted position to the most extended position is the extension stroke. Hereinafter, the most extended position and the most degenerated position may be referred to as dead points.

  The suction port 31 of the valve plate 21 is formed so that a piston chamber 37 into which the piston 23 located in a position excluding the vicinity of each dead point is fitted is connected via a cylinder port 38. The discharge port 32 of the valve plate 21 is formed so that a piston chamber 37 into which the piston 23 located in a position other than the vicinity of each dead point is fitted is connected via a cylinder port 38 in the contraction stroke. The pressure relief port 33 of the valve plate 21 is connected via a cylinder port 38 to the piston chamber 37 into which the piston 23 near the dead point (maximum extension position) is fitted when switching from the contraction stroke to the extension stroke. Is formed.

  A suction passage (not shown) communicating with the suction port 31 of the valve plate 21 is formed in the valve casing 26c, and a discharge passage (not shown) communicating with the discharge port 32 of the valve plate 21 is formed. A tank for storing hydraulic oil is connected to the suction passage, and an actuator as a supply destination is connected to the discharge passage. In the piston pump 20, when power is transmitted from the prime mover and the cylinder block 22 is rotationally driven together with the rotary shaft 27, the pistons 23 are reciprocally displaced along with the rotation of the cylinder block 22. And can be discharged through the discharge port 32. As a result, hydraulic oil can be supplied to the actuator to drive the actuator.

  In the piston pump 20, when the tilt angle of the swash plate 35 is changed by the servo mechanism 48, the distance between the most extended position and the most retracted position of the piston 23 changes, and the operation is performed by one reciprocation of the piston 23. The oil discharge rate changes. Therefore, the capacity of the piston pump 20 can be changed by changing the tilt angle of the swash plate 35.

  FIG. 3 is a cross-sectional view showing a part of the piston pump 20 as viewed from the section line S3-S3 in FIG. FIG. 3 shows a developed arc-shaped cross section extending in the circumferential direction. When the connection destination of the cylinder port 38 is switched from the discharge port 32 to the suction port 31, if the cylinder port 38 is simultaneously connected to both the suction port 31 and the discharge port 32, the suction port 31 and the discharge port 32 are connected. Are connected via the cylinder port 38, and the hydraulic oil flows backward. In order to avoid this problem, the discharge port 4 and the cylinder port 7 are formed so as to be blocked from each other before the piston 8 reaches the most retracted position. Specifically, the circumferential dimension W1 of the cylinder port 38 is formed smaller than the circumferential distance W2 between the suction port 31 and the discharge port 32. The circumferential distance W2 between the suction port 31 and the discharge port 32 is the distance between the end of the discharge port 32 on the downstream side in the rotational direction A20 and the end of the suction port 31 on the upstream side in the rotational direction A20. The rotation direction A20 is a moving direction of the piston chamber 37 and the cylinder port 38.

  In such a configuration, if the pressure release port 33 is not provided, after the cylinder port 38 is blocked from the discharge port 32, the hydraulic oil in the piston chamber 37 is compressed by the piston 23, and the pressure of the hydraulic oil is reduced. In the raised state, the cylinder port 38 is suddenly connected to the suction port 3 with a large opening area. Therefore, the hydraulic oil in the piston chamber 37 becomes a jet and flows into the suction port 31, generating a large noise and causing erosion of the valve plate 21. In order to prevent the jet flow that causes noise and erosion, the valve plate 21 is formed with a pressure release port 33 having two pressure release holes 34 and 35 at a portion where the suction port 31 starts to open.

  Of the two pressure release holes 34, the first pressure release hole 34 disposed on the upstream side in the rotational direction A20 is formed at a distance W3 from the discharge port 32 in the circumferential direction. The circumferential distance W3 between the first pressure relief hole 34 and the discharge port 32 is formed slightly smaller than the circumferential dimension W1 of the cylinder port 38. The first pressure release hole 34 and the second pressure release hole 35 disposed on the downstream side in the rotation direction A20 of the two pressure release holes 34 are formed with an interval W4 in the circumferential direction. The space W4 between the pressure release holes 34 and 35 is formed smaller than the circumferential dimension W1 of the cylinder port 38.

  Each of the pressure release holes 34 and 35 is divided into a group on the upstream side in the rotational direction A20 and a group on the downstream side in the rotational direction A20. In the present embodiment, the first decompression hole 34 belongs to the upstream group in the rotational direction A20, and the second decompression hole 35 belongs to the downstream group in the rotational direction A20. The first pressure release holes 34 belonging to the group on the upstream side in the rotational direction A20 are communicated with an internal space in which the cylinder block 22 and the like in the casing 26 serving as a drain discharge place are accommodated. The second decompression hole 35 belonging to the group on the upstream side in the rotational direction A20 is communicated with the suction port 31 through the inside of the valve plate 21. Each of the pressure release holes 34 and 35 is a cylindrical fine hole, and the inner diameter of the first pressure release hole 34 is smaller than the inner diameter of the second pressure release hole 35.

  Regardless of the capacity, each of the pressure release holes 34 and 35 is formed such that when connected to the cylinder port 38, the flow rate at which the hydraulic oil in the piston chamber 37 is discharged is a flow rate that does not become a jet flow. ing. An example of the flow velocity that becomes a jet flow is over 20 m / sec when, for example, the inner diameter of the pressure release holes 34 and 35 is 2 mm and the pressure difference between the high pressure (discharge port) side and the low pressure (suction port) side is 2 MPa. A jet is generated from the degree. This value is a value that varies depending on various conditions, and the value is merely an example. Each of the pressure release holes 34 and 35 is connected to the piston chamber 37 through the pressure release holes 34 and 35 from when the cylinder port 38 is blocked from the discharge port 32 to when it is connected to the suction port 31. The total discharge amount of the dischargeable working liquid is formed to be equal to or larger than a preset discharge amount. This set discharge amount reduces the pressure of the hydraulic oil in the piston chamber 37 to a pressure at which the hydraulic oil in the piston chamber 37 is not discharged as a jet when the cylinder port 38 is connected to the suction port 31. Therefore, the discharge amount is determined based on the capacity of the piston pump 20.

  The flow rate of the hydraulic oil flowing down the pressure release holes 34 and 35 and the total discharge amount discharged through the pressure release holes 34 and 35 are determined by selecting the inner diameter of the pressure release holes 34 and 35. Adjusted. In the configuration in which only one pressure release hole is formed as in the prior art, the flow rate of the pressure release hole is equal to or less than the set flow rate in all the capacities of the variable range, and the discharge amount discharged through the pressure release hole is Although it cannot be configured so as to be equal to or greater than the set discharge amount, if a configuration in which a plurality of pressure-removing holes 34 and 35 are formed as in the present embodiment, the pressure-reducing pressure is obtained in all capacities in the variable range. It can be configured such that the flow rate of the hole is equal to or lower than the set flow rate, and the discharge amount discharged through the pressure release hole is equal to or higher than the set discharge amount.

  FIG. 4 is a graph showing the dynamic characteristics of the piston pump 20 over a stroke of one rotation, focusing on one piston 23. FIG. 5 is a graph showing the dynamic characteristics of the piston pump 20 in a state where the piston 23 is in the vicinity of the most retracted position with attention paid to one piston 23. FIG. 6 is a graph comparing the dynamic characteristics of the piston pump 20 of the present invention with the dynamic characteristics of a conventional piston pump in which the notch 10 and the pressure release hole 11 are formed. In FIG. 4, the horizontal axis indicates the cylinder port position, and the vertical axis indicates the flow rate of hydraulic oil and the piston chamber pressure. In FIG. 5, the horizontal axis indicates the cylinder port position, and the vertical axis indicates the piston chamber pressure and the opening area. 6 (1) to 6 (3), the horizontal axis indicates the cylinder port position, in FIG. 6 (1), the vertical axis indicates the piston chamber pressure, and in FIG. 6 (2), the vertical axis indicates The opening area is shown, and in FIG. 6 (3), the vertical axis shows the flow rate. The cylinder port position is an angular position, the angular position where the piston 23 is in the most extended position is 0 degrees, and the angular position where the piston 23 is in the most retracted position is 180 degrees. The flow rate discharged from the piston chamber 37 is positive. The piston chamber pressure is the pressure of the hydraulic oil in the piston chamber 37. The opening area is the opening area of the cylinder port 38.

  In FIG. 4, the broken line 60 indicates the piston chamber pressure, the alternate long and short dash line 61 indicates the flow rate of the hydraulic oil flowing down the discharge port 32, and the alternate long and two short dashes line 62 indicates the flow rate of the hydraulic oil flowing down the suction port 31. 63 shows the flow rate of the hydraulic oil flowing down the first pressure relief hole 34. Of the flow rate indicated by the two-dot chain line 62, the flow rate when the cylinder port position indicated by reference numeral 64 is around 180 degrees is the flow rate of the hydraulic oil flowing into the suction port 31 through the second pressure release hole 35. In FIG. 5, the piston chamber pressure is indicated by a one-dot chain line 65, the opening area for the discharge port 32 is indicated by a solid line 66, the opening area for the suction port 31 is indicated by a broken line 67, and the first pressure release hole 34 is indicated by a two-dot chain line 68. The opening area with respect to is shown. Of the opening area with respect to the suction port 31, the opening area indicated by the reference numeral 69 in the angle range θ of the cylinder port position of about 186.5 degrees to about 195.5 degrees is the opening area with respect to the second decompression hole 35. . In FIG. 6, dynamic characteristics of the piston pump 20 of the present invention are indicated by solid lines 70 to 72, and dynamic characteristics of the conventional piston pump are indicated by broken lines 73 to 75.

  As in the present embodiment, the pressure relief holes 34 and 35 are formed in the valve plate 21 so that the hydraulic oil pressure in the piston chamber 37 is reduced before the cylinder port 38 is directly connected to the suction port 31. The opening area connected to the pressure release port 33 for discharging the hydraulic oil to decrease is shown by a two-dot chain line 68 and a broken line 67 portion 69 in FIG. 5 and small as shown in FIG. 6 (2). Can do. Further, the opening area is configured to increase in a multistage manner. As a result, as shown in FIG. 6 (1), the rate of decrease in the pressure of the hydraulic oil in the piston chamber 37 can be kept small as compared with the configuration in which the notch 10 of the prior art is formed. As a result, as indicated by the solid line 63 and the portion 64 of the two-dot chain line 62 in FIG. 4, the flow rate can be kept small so that the hydraulic oil flowing down the pressure release holes 34 and 35 does not become a jet. Furthermore, before the cylinder port 38 is connected to the suction port 31, the pressure of the hydraulic oil in the piston chamber 37 can be reduced to a pressure that does not cause a jet when the cylinder port 38 is connected to the suction port 31, As shown by the solid line 72 in FIG. 6 (3), it is possible to prevent the generation of a jet when connected to a suction port such as a portion 78 indicated by a broken line 75 in FIG. 6 (3).

  According to the present embodiment, the valve plate 21 is formed with the pressure release port 33 on the upstream side in the rotational direction A20 with respect to the suction port 31. As the piston chamber 37 moves, the decompression port 33 opens the cylinder port 38 communicating with the piston chamber 37 in multiple stages, and before the piston chamber 37 is connected to the suction port 31, the operation of the piston chamber 37 is performed. Thoroughly discharge the oil. Moreover, it has two or more decompression holes 34, 35, and prevents any jet flow from occurring in the decompression holes 34, 35 regardless of whether it is a constant displacement type or a variable displacement type, and then the piston chamber 37. Is connected to the suction port 31, the pressure of the hydraulic oil in the piston chamber 37 can be reduced to a pressure at which no jet flows when the piston chamber 37 is connected to the suction port 31. Therefore, the valve plate 21 can prevent the hydraulic fluid in the piston chamber 37 from being discharged as a jet, prevent noise, and prevent erosion of the valve plate 21.

  Furthermore, the pressure release hole 33 on the upstream side in the movement direction of the piston chamber 37, which is more likely to generate a jet flow than the pressure release hole 34 on the downstream side in the movement direction of the piston chamber 37, is drain-connected so as to communicate with the discharge location. Even if a jet is generated, the jet can be prevented from flowing into the suction port 31. This can prevent pulsation. The pressure release hole 34 on the downstream side in the moving direction of the piston chamber 37 is communicated with the suction port 31 and the drain flow rate can be reduced. This can increase the efficiency.

  Furthermore, the opening area of the pressure release hole 33 on the upstream side in the movement direction of the piston chamber 37 is reduced to reliably prevent the jet flow of the pressure release hole 33 on the upstream side and discharge the hydraulic oil in the piston chamber 37 to increase the pressure. Can be reduced. With the pressure of the hydraulic oil in the piston chamber 37 being reduced by the upstream pressure release hole 33 in this way, the piston chamber 37 is connected to the suction port 31 by the pressure release hole 34 on the downstream side in the movement direction of the piston chamber 37. Before the operation, the amount of hydraulic oil discharged from the piston chamber 37 can be increased, and the pressure of the hydraulic oil in the piston chamber 37 can be greatly reduced. Therefore, it is possible to reliably prevent the jet flow of each of the pressure release holes 33 and 34 and the jet flow to the suction port 31. In addition, the drain flow rate can be kept small, and the pump efficiency can be increased.

In this way, a suitable piston pump 20 can be realized.
Each above-mentioned embodiment is only illustration of this invention, and can change a structure within the scope of the present invention. For example, each of the above-described embodiments has been described by taking a variable displacement swash plate type piston pump as an example, but may be implemented in a fixed displacement pump. Further, the present invention is not limited to the swash plate type, and may be implemented in an axial type piston pump. Moreover, you may implement not only in a pump but in a motor. Furthermore, although the above-described embodiment has been described as a configuration in which the cylinder block 22 rotates only in one direction, a configuration capable of rotating in both forward and reverse directions may be used. In this case, a decompression port may be provided on the upstream side of a port that may be a suction port. Further, the hydraulic device may be configured to operate with a fluid other than hydraulic oil, for example, hydraulic water. Moreover, the structure used for machines other than an industrial machine and a construction machine, a vehicle, etc. may be sufficient.

It is a front view which shows the valve plate 21 of the piston pump 20 of one Embodiment of this invention. 2 is a cross-sectional view showing a piston pump 20. FIG. It is sectional drawing which shows a part of piston pump 20 seeing from cut surface line S3-S3 of FIG. It is a graph which shows the dynamic characteristic of the piston pump 20 over the stroke of 1 rotation paying attention to one piston 23. FIG. It is a graph which shows the dynamic characteristic of the piston pump 20 about the state which pays attention to one piston 23 and the piston 23 exists in the most retracted position vicinity. It is a graph which compares and shows the dynamic characteristic of the piston pump 20 of this invention, and the dynamic characteristic of the piston pump of the prior art in which the notch 10 is formed. It is a front view which shows the valve plate 2 of the piston pump of a prior art. It is sectional drawing which shows a part of piston pump seeing from cut surface line S8-S8 of FIG. It is a graph which shows the dynamic characteristic of the piston pump of a prior art over the stroke | round of 1 rotation paying attention to one piston. It is a graph which shows the dynamic characteristic of the piston pump of a prior art about the state which exists in the position in the position where a piston degenerates the most, paying attention to one piston.

Explanation of symbols

20 Piston pump 21 Valve plate 22 Cylinder block 23 Piston 24 Shoe 25 Swash plate 26 Casing 27 Rotating shaft 31 Suction port 32 Discharge port 33 Depressurization port 34 First depressurization hole 35 Second depressurization hole 37 Piston chamber 38 Cylinder port A20 Rotation direction L20 Rotation axis L25 Tilt axis

Claims (3)

A rotating shaft, a cylinder block integrally connected to the rotating shaft and formed with a plurality of piston chambers at intervals in the circumferential direction, and each piston chamber has an extension stroke and a contraction stroke as the cylinder block rotates. A plurality of reciprocating pistons, a discharge port connected to a piston chamber in which a piston in a contracting stroke is fitted, and a suction port connected to a piston chamber in which a piston in an extending stroke is fitted are formed, and the piston chamber is Provided in a hydraulic device comprising at least a valve plate formed with an area change slowing means for smoothening a change in the opening area in order to slow down a rapid pressure fluctuation in the piston chamber when connected to the suction port. A valve plate,
When shifting from the contraction stroke to the extension stroke with the movement of the piston chamber, there is no notch in the portion that starts the opening of the suction port , and there are two or more decompression holes at intervals, and the piston The pressure release hole on the upstream side in the movement direction of the chamber communicates with the drain discharge location, and the pressure release hole on the downstream side in the movement direction of the piston chamber has a bent portion in the middle of the flow path and communicates with the suction port. And valve plate.   The pressure release hole on the downstream side in the movement direction of the piston chamber has an opening area larger than the pressure release hole on the upstream side in the movement direction of the piston chamber so that no jet flow is generated when the piston chamber is directly connected to the suction port. The valve plate according to claim 1.   A hydraulic device comprising the valve plate according to claim 1.

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