JP2024089186A - Hydraulic Pump - Google Patents

Abstract

[Problem] To provide a hydraulic rotating device capable of reducing pulsation over a wide range of frequency bands and suppressing enlargement. [Solution] A hydraulic pump includes a casing in which an intake passage and a discharge passage are formed, a valve plate in which an intake port and a discharge port are formed, a cylinder block in which a plurality of cylinder bores are formed, and a plurality of pistons inserted in each of the cylinder bores so as to be capable of reciprocating motion, and the casing further includes a first communication passage having a first throttle, a chamber, and a second communication passage having a second throttle and extending to the valve plate, which communicates the discharge passage with the chamber, the chamber stores hydraulic fluid introduced from the discharge passage via the first communication passage, the second communication passage opens at a bottom dead center side blocking surface between the intake port and the discharge port of the valve plate and is connected to the chamber, and the first throttle has a flow passage cross-sectional area larger than that of the second throttle. [Selected Figure] Figure 2

Description

This disclosure relates to a hydraulic pump that discharges hydraulic fluid into a discharge passage.

One example of a hydraulic pump is the variable displacement piston machine described in Patent Document 1. The variable displacement piston pump in Patent Document 1 has a chamber that connects the discharge passage and the cylinder bore near the bottom dead center. The variable displacement piston pump uses the chamber to reduce noise.

Japanese Patent Application Laid-Open No. 3-85381

The noise of the variable displacement piston pump of Patent Document 1 is caused by pulsation of the hydraulic fluid flowing through the discharge passage. The pulsation of the hydraulic fluid vibrates at a frequency that corresponds to the rotational speed of the cylinder block. It is desirable for a hydraulic pump to be used over a wide range of rotational speeds of the cylinder block. Therefore, it is desirable to suppress pulsation over a wide frequency band. In this regard, the variable displacement piston pump of Patent Document 1 can reduce pulsation in the low frequency band, but is less effective at reducing pulsation in the high frequency band.

Therefore, the present disclosure aims to provide a hydraulic rotating device that can reduce pulsation over a wide range of frequency bands.

The first hydraulic pump of the present disclosure comprises a casing in which an intake passage through which hydraulic fluid is introduced and a discharge passage through which hydraulic fluid is discharged are formed, a valve plate provided in the casing and in which an intake port connected to the intake passage and a discharge port connected to the discharge passage are respectively formed, a cylinder block including a plurality of cylinder bores and sliding on the valve plate, and a plurality of pistons inserted into each of the cylinder bores and reciprocating through the cylinder bores. The casing further comprises a first communication passage having a first throttle, a chamber, and a second communication passage extending to the valve plate, the first communication passage communicating with the discharge passage and the chamber, the chamber storing the hydraulic fluid introduced from the discharge passage via the first communication passage, the second communication passage having a second throttle, opening at a bottom dead center side blocking surface between the intake port and the discharge port of the valve plate and connected to the chamber, and the first throttle having a flow passage cross-sectional area larger than that of the second throttle.

According to the first hydraulic pump of the present disclosure, the chamber is connected to the discharge passage through the first communication passage. Therefore, the chamber and the first communication passage constitute a resonator. The vibration absorption function of the resonator can suppress the pulsation of the working fluid flowing through the discharge passage. The chamber is also connected to a second communication passage having a second throttle and opening at the bottom dead center side blocking surface. Therefore, the chamber 25 is connected to the cylinder bore located between the suction port and the discharge port on the bottom dead center side through the second communication passage. Therefore, the chamber and the second communication passage constitute a backflow suppression mechanism. The backflow suppression mechanism can increase the internal pressure of the cylinder bore until the connection destination of the cylinder bore switches from the suction port to the discharge port. This makes it possible to suppress the working fluid from flowing back from the discharge passage to the cylinder bore when the connection destination of the cylinder bore switches to the discharge port (i.e., to achieve the backflow suppression function). Therefore, it is possible to reduce the pulsation caused by the backflow of the working fluid to the cylinder bore. Furthermore, the first throttle has a flow path cross-sectional area larger than that of the second throttle. Therefore, the backflow suppression mechanism mainly reduces pulsation in the low frequency band. On the other hand, the resonator mainly reduces pulsation in the higher frequency band than the backflow suppression mechanism. Therefore, a single chamber can reduce pulsation in a wide frequency band. Also, a single chamber can be used to configure both the resonator and the backflow suppression mechanism.

The second hydraulic pump of the present disclosure includes a casing in which an intake passage through which hydraulic fluid is introduced and a discharge passage through which hydraulic fluid is discharged are formed, a valve plate provided in the casing in which an intake port connected to the intake passage and a discharge port connected to the discharge passage are respectively formed, a cylinder block including a plurality of cylinder bores and sliding on the valve plate, a plurality of pistons inserted into each of the cylinder bores and reciprocating within the cylinder bores, the casing including a first communication passage having a first restriction, a chamber, and a second communication passage extending to the valve plate, the first communication passage communicating the discharge passage with the chamber, the chamber , storing the working fluid guided from the discharge passage through the first communication passage, the second communication passage having a second throttle, opening at a bottom dead center side blocking surface between the intake port and the discharge port of the valve plate, and connected to the chamber, the chamber forming a resonator that reduces the pulsation of the working fluid flowing through the discharge passage together with the first communication passage, and forming a backflow suppression mechanism that reduces the pulsation of the working fluid flowing through the discharge passage by suppressing backflow to the cylinder bore together with the second communication passage and the second throttle, the backflow suppression mechanism reducing pulsation in the low frequency band, and the resonator reducing pulsation in the high frequency band.

According to the second hydraulic pump of the present disclosure, the chamber, together with the first communication passage, constitutes a resonator, and the second communication passage and the second throttle constitute a backflow suppression mechanism. The resonator reduces pulsation more than the backflow suppression mechanism in the high frequency band. The backflow suppression mechanism reduces pulsation more than the resonator in the low frequency band. Therefore, pulsation can be reduced over a wide frequency band. In addition, the resonator and the backflow suppression mechanism can be formed by a single chamber.

This disclosure makes it possible to reduce pulsation over a wide range of frequency bands.

FIG. 1 is a cross-sectional view illustrating a hydraulic pump according to an embodiment of the present disclosure. 2 is a cross-sectional view of the hydraulic pump of FIG. 1 taken along line II-II. FIG. 2 is a front view showing a valve plate provided in the pump of FIG. 1 . 2 is a circuit diagram showing an outline of the flow of hydraulic fluid on the discharge side of the hydraulic pump of FIG. 1 . FIG. 2 is a perspective view showing a passage on a discharge side of the hydraulic pump of FIG. 1 . FIG. 2 is a cross-sectional view showing a chamber block in the hydraulic pump of FIG. 1 . FIG. 2 is a bottom view showing a passage on the discharge side of the hydraulic pump of FIG. 1 . 4 is a graph showing the relationship between the frequency of pulsation suppressed by the pulsation suppression mechanism of the hydraulic pump of FIG. 1 and the pulsation reduction effect.

The hydraulic pump 1 according to an embodiment of the present disclosure will be described below with reference to the drawings mentioned above. Note that the concept of direction used in the following description is used for convenience in the description and does not limit the orientation of the configuration of the invention to that direction. Furthermore, the hydraulic pump 1 described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the embodiment, and additions, deletions, and modifications are possible within the scope of the spirit of the invention.

<Hydraulic pump>
The hydraulic pump 1 shown in Fig. 1 is provided in various machines, such as construction machines such as excavators and cranes, industrial machines such as forklifts, agricultural machines such as tractors, and hydraulic machines such as presses. The hydraulic pump 1 is, for example, a variable displacement swash plate pump. However, the hydraulic pump 1 may also be a fixed displacement swash plate pump or a bent axis pump. The hydraulic pump 1 is driven by a drive source (e.g. an electric motor, an engine, or both, in this embodiment, an electric motor) not shown in the figure to discharge a working fluid (liquid such as oil and water).

The hydraulic pump 1 includes a casing 11, a cylinder block 12, a number of pistons 13, a swash plate 14, a regulator 15, and a valve plate 16.

<Casing>
The casing 11 accommodates a cylinder block 12, a plurality of pistons 13, a swash plate 14, a regulator 15, a valve plate 16, etc. More specifically, an accommodation space 21 is formed in the casing 11. In the casing 11, the accommodation space 21 accommodates the cylinder block 12, a plurality of pistons 13, a swash plate 14, a regulator 15, a valve plate 16, etc. The accommodation space 21 has an opening 21a at one end face of the casing 11 on one axial side (i.e., one axial end face). The axial direction is the direction in which a predetermined axis L1 extends.

As shown in FIG. 2, the casing 11 is formed with an intake passage 22 and a discharge passage 23. The working fluid is introduced into the intake passage 22. On the other hand, the working fluid is discharged into the discharge passage 23. The intake passage 22 and the discharge passage 23 are formed, for example, on the other axial side of the accommodation space 21 in the casing 11. The intake passage 22 and the discharge passage 23 open at the end face on the other axial side of the accommodation space 21.

As will be described in detail later, the casing 11 further includes a first communication passage 24, a chamber 25, and a second communication passage 26. The casing 11 also includes a casing body 11a, a chamber block 11b, and a volume adjustment mechanism 11c (see FIG. 6, which will be described in detail later).

<Cylinder block>
The cylinder block 12 includes a plurality of cylinder bores 12a. The cylinder block 12 is rotatably accommodated in the casing 11, i.e., in the accommodation space 21. More specifically, the cylinder block 12 is formed in a cylindrical shape. The cylinder block 12 is accommodated in the accommodation space 21 such that the end face on the other axial side (i.e., the other axial end face) faces the other axial end face of the accommodation space 21. A rotating shaft 17 is inserted through the cylinder block 12 along its axis L1. The rotating shaft 17 is prevented from rotating relatively by a spline connection or the like. The rotating shaft 17 is supported by the casing 11 so as to be rotatable around a predetermined axis L1. One end of the rotating shaft 17 protrudes from the opening 21a and is connected to a drive source (not shown). The driving source rotates the rotating shaft 17, so that the cylinder block 12 rotates around the axis L1.

The cylinder bores 12a are formed in one axial end face of the cylinder block 12 (i.e., one axial end face). The cylinder bores 12a are arranged at intervals around the rotation shaft 17 (i.e., around the axis L1). Each cylinder bore 12a is formed with a cylinder port 12b. The cylinder bore 12a opens through the cylinder port 12b at the end face on the other axial side (i.e., the other axial end). In this embodiment, nine cylinder bores 12a are formed in the cylinder block 12. However, the number of cylinder bores 12a described above is merely an example, and may be eight or less, or may be ten or more.

<Piston>
The pistons 13 are inserted into the cylinder bores 12a of the cylinder block 12. Each of the pistons 13 reciprocates in the corresponding cylinder bore 12a. A shoe 18 is attached to the tip of each of the pistons 13 so as to be slidable and rotatable.

<Swash plate>
The swash plate 14 is disposed on one axial side of the cylinder block 12 with a gap therebetween. The swash plate 14 has a shoe plate 19. The swash plate 14 does not necessarily have to have the shoe plate 19. The shoe plate 19 is inclined toward the cylinder block 12. The swash plate 14 supports a plurality of shoes 18 from one axial side via the shoe plate 19. The plurality of shoes 18 are pressed against the shoe plate 19 by a pressing plate 20, and slide and rotate on the shoe plate 19 around the axis L1. Therefore, when the cylinder block 12 rotates, the pistons 13 reciprocate in the cylinder bores 12a. The swash plate 14 can also be inclined around the axis L2 perpendicular to the axis L1. That is, the swash plate 14 can change the tilt angle. Therefore, the stroke amount of the pistons 13 can be changed. This allows the amount of hydraulic fluid discharged from each cylinder bore 12a, i.e., the discharge amount, to be changed.

<Regulator>
The regulator 15 changes the tilt angle of the swash plate 14 by rotating the swash plate 14 about the axis L2. More specifically, the regulator 15 has a servo piston (not shown) connected to the swash plate 14 via a connecting member 15a. The regulator 15 moves the servo piston in response to an input signal (e.g., pilot pressure). This adjusts the tilt angle of the swash plate 14.

<Valve plate>
The valve plate 16 is provided in the casing 11. More specifically, the valve plate 16 is interposed between the other axial end face of the accommodation space 21 and the cylinder block 12. The valve plate 16 is fixed to the other axial end face of the accommodation space 21. The other axial end face of the cylinder block 12 is pressed against the valve plate 16. The cylinder block 12 rotates around the axis L1 so as to slide on the valve plate 16.

The valve plate 16 is formed with an intake port 16a and an exhaust port 16b. The intake port 16a is connected to an intake passage 22. The exhaust port 16b is connected to an exhaust passage 23. The intake port 16a and the exhaust port 16b are connected to the cylinder bores 12a via the cylinder ports 12b. The cylinder bores 12a are alternately connected to the intake port 16a and the exhaust port 16b as the cylinder block 12 rotates. The intake port 16a guides the hydraulic fluid in the intake passage 22 to the cylinder bores 12a via the connected cylinder ports 12b. The exhaust port 16b exhausts the hydraulic fluid from the cylinder bores 12a to the exhaust passage 23 via the connected cylinder ports 12b.

In more detail, the valve plate 16 is formed in a disk shape as shown in FIG. 3. The valve plate 16 is attached to the other axial end surface of the accommodation space 21 so that its axis coincides with the axis L1 (see FIG. 2). The intake port 16a and the discharge port 16b are formed in a concentric arc shape centered on the axis L1 as shown in FIG. 3. The intake port 16a and the discharge port 16b are also arranged at intervals from each other in the circumferential direction. As a result, a top dead center side blocking surface 16c and a bottom dead center side blocking surface 16d are formed between the intake port 16a and the discharge port 16b, respectively. The top dead center side blocking surface 16c blocks the cylinder bore 12a near the top dead center, and the bottom dead center side blocking surface 16d blocks the cylinder bore 12a near the bottom dead center. Note that "near the top dead center" means the top dead center and a position nearby, and "near the bottom dead center" means the bottom dead center and a position nearby, for example, between the intake port 16a and the discharge port 16b. Additionally, the top dead center is the position where the piston 13 is closest to the valve plate 16. The bottom dead center is the position where the piston 13 is farthest from the valve plate 16.

<Pulsation suppression mechanism>
2, the casing 11 is formed with a first communication passage 24, a chamber 25, and a second communication passage 26. The first communication passage 24, the chamber 25, and the second communication passage 26 constitute a pulsation suppression mechanism 28. The pulsation suppression mechanism 28 communicates the cylinder bore 12a located between the suction port 16a and the discharge port 16b of the valve plate 16 on the bottom dead center side (i.e., near the bottom dead center) with the discharge passage 23. The pulsation suppression mechanism 28 reduces pulsation of the working fluid flowing through the discharge passage 23 by a vibration absorption function and a backflow suppression function.

The configuration of the pulsation suppression mechanism 28, i.e., the first communication passage 24, the chamber 25, and the second communication passage 26, will be described in more detail below. As also shown in FIG. 4, the first communication passage 24 connects the discharge passage 23 and the chamber 25. The first communication passage 24 also has a first throttle 24a. The first throttle 24a is formed with a smaller flow path cross-sectional area than its upstream and downstream portions. Furthermore, the first throttle 24a has a larger flow path cross-sectional area than the second throttle 26a, which will be described in detail later (see FIG. 5).

The chamber 25 stores the working fluid guided from the discharge passage 23 via the first communication passage 24. The chamber 25 has a volume larger than each cylinder bore 12a. More specifically, the chamber 25 has a volume larger than the maximum volume that can be sucked into the cylinder bore 12a. The chamber 25 and the first communication passage 24 form a resonator 31. The resonator 31 formed by the chamber 25 and the first communication passage 24 functions in the same way as, for example, a Helmholtz resonator. In other words, the resonator 31 has a vibration-absorbing function. This makes it possible to reduce the pulsation of the working fluid flowing through the discharge passage 23. In this embodiment, the second communication passage 26 also forms part of the resonator 31.

The second communication passage 26 is connected to the chamber 25. The second communication passage 26 extends to the bottom dead center side blocking surface 16d of the valve plate 16. The second communication passage 26 opens at the bottom dead center side blocking surface 16d of the valve plate 16. Therefore, the second communication passage 26 is connected to the cylinder bore 12a located near the bottom dead center. The second communication passage 26 also has a second throttle 26a. The second throttle 26a is formed, for example, in the valve plate 16. More specifically, the second throttle 26a is formed in the bottom dead center side blocking portion 16e of the valve plate 16. Here, the bottom dead center side blocking portion 16e is the portion between the intake port 16a and the discharge port 16b. The second throttle 26a is connected to the cylinder bore 12a located near the bottom dead center.

The second communication passage 26 and the chamber 25 constitute a backflow prevention mechanism 32. In this embodiment, the first communication passage 24 also constitutes the backflow prevention mechanism 32 together with the second communication passage 26 and the chamber 25 to store the working fluid from the discharge passage 23 in the chamber 25. The backflow prevention mechanism 32 supplies the working fluid stored in the chamber 25 to the cylinder bore 12e near the bottom dead center. This prevents the working fluid from flowing back from the discharge passage 23 to the cylinder bore 12a when the connection destination of the cylinder bore 12a is switched from the intake port 16a to the discharge port 16b. This reduces the pulsation of the working fluid flowing through the discharge passage 23. In addition, the flow path cross-sectional area of the second throttle 26a is smaller than the flow path cross-sectional area of the first throttle 24a. In this embodiment, the second throttle 26a is, for example, like a choke and extends in the axial direction.

<Specific configuration of the casing>
As described above, the casing 11 includes the casing body 11a, the chamber block 11b, and the volume adjustment mechanism 11c. The casing body 11a defines an accommodation space 21. The accommodation space 21 of the casing body 11a accommodates the cylinder block 12, the plurality of pistons 13, the swash plate 14, the regulator 15, and the valve plate 16. The casing body 11a also defines at least an intake passage 22 and a discharge passage 23. The casing body 11a, together with the cylinder block 12, the plurality of pistons 13, the swash plate 14, the regulator 15, and the valve plate 16, constitutes a hydraulic pump body 29.

At least a chamber 25 is formed in the chamber block 11b as shown in FIG. 6. In this embodiment, a first communication passage 24 is further formed in the chamber block 11b. In addition, in this embodiment, a second communication passage 26 is formed from the chamber block 11b to the casing body 11a. The chamber block 11b is formed, for example, in a rectangular parallelepiped shape that is long in the first direction. And, the chamber block 11b is attached, for example, to one side of the casing body 11a in the second direction. Here, the first direction is a direction perpendicular to the axial direction. The first direction is, for example, a direction perpendicular to the axis L1 and the axis L2. Also, the second direction is a direction in which the axis L2 extends, and is a direction perpendicular to the axial direction and the first direction. In this embodiment, the axial direction is the front-rear direction, the first direction is the up-down direction, and the second direction is the left-right direction.

In this embodiment, the casing body 11a and the chamber block 11b have the following passages. That is, the suction passage 22 and the discharge passage 23 are arranged at intervals on one side and the other side of the second direction, respectively, as shown in FIG. 2. The suction passage 22 is bent from the accommodation space 21 to the other side of the second direction. The suction passage 22 opens at the side surface of the casing body 11a on the other side of the second direction. The discharge passage 23 is bent from the accommodation space 21 to one side of the second direction. The discharge passage 23 extends to the side surface of the casing body 11a on the one side of the second direction. The chamber block 11b is attached to the side surface of the casing body 11a on the one side of the second direction at a position corresponding to the discharge passage 23. The discharge passage 23 extends from the casing body 11a to the chamber block 11b, penetrating the chamber block 11b in the one side of the second direction.

As shown in FIG. 6, the chamber 25 is formed, for example, in the chamber block 11b as follows. That is, the chamber 25 is formed to have a circular cross section extending in the first direction. The chamber 25 is disposed adjacent to the discharge passage 23 in the axial direction.

As shown in FIG. 5, the first communication passage 24 is formed in an L-shape when viewed from the other side in the second direction. One end of the first communication passage 24 is connected to the discharge passage 23. The other end of the first communication passage 24 is connected to the end side on the circumferential surface of the chamber 25 on the other side in the first direction, that is, the other end side in the first direction. More specifically, the first communication passage 24 has a passage portion 24b, a throttle accommodating portion 24c, and a throttle member 24d. The passage portion 24b and the throttle accommodating portion 24c are formed in the chamber block 11b so as to intersect with each other. More specifically, the passage portion 24b extends from the discharge passage 23 in the other direction in the first direction. The throttle accommodating portion 24c intersects (orthogonally in this embodiment) with the passage portion 24b and extends in one axial direction (corresponding to one predetermined direction). The throttle accommodating portion 24c is formed, for example, in a circular cross section. The middle part of the diaphragm housing part 24c is adapted to house the diaphragm member 24d, which will be described later. In this embodiment, a female thread is formed in the middle part of the diaphragm housing part 24c to screw in the diaphragm member 24d. In addition, the chamber block 11b is formed with a housing opening 24e on the extension line of the diaphragm housing part 24c (more specifically, on the extension line of the other side of the axial direction of the diaphragm housing part 24c). The diaphragm member 24d is a member that forms the first diaphragm 24a. The diaphragm member 24d is formed in a cylindrical shape, and the inner hole forms the first diaphragm 24a. The diaphragm member 24d is inserted from the housing opening 24e. The diaphragm member 24d is housed in the diaphragm housing part 24c. In this embodiment, the diaphragm member 24d is screwed in the middle part of the diaphragm housing part 24c. This allows the first diaphragm 24a to be interposed in the middle part of the diaphragm housing part 24c. The housing opening 24e is closed by a plug 24f.

As shown in Figures 5 and 7, the second communication passage 26 extends from the casing 11 to the bottom dead center side blocking surface 16d of the valve plate 16 as described above. The second communication passage 26 opens at the bottom dead center side blocking surface 16d. The second communication passage 26 connects the cylinder bore 12a near the bottom dead center to the chamber 25. Note that, like the first communication passage 24, the second communication passage 26 is on the other end side of the circumferential surface of the chamber 25 in the first direction, and is connected to one side of the first communication passage 24 in the second direction. Note that in Figure 7, the discharge passage 23, each passage 24, 26, and the chamber 25 are hatched for ease of explanation.

The second communication passage 26 has a block side portion 26b, a body side portion 26c, and a second throttle 26a. The block side portion 26b is a portion formed in the chamber block 11b and is formed in an L-shape. The block side portion 26b is not limited to an L-shape, and may be formed in a curved shape, for example. That is, the block side portion 26b is connected to the chamber 25 and extends in the axial direction so as to be parallel to the throttle-accommodating portion 24c of the first communication passage 24. The block side portion 26b is bent to the other side in the axial direction and extends in the second direction. The body side portion 26c is a portion formed in the casing body 11a, and the body side portion 26c is also formed in an L-shape. The body side portion 26c is not limited to an L-shape, and may be formed in a curved shape, for example. One end of the body side portion 26c is connected to the block side portion 26b. The body side portion 26c also extends in the second direction. As shown in FIG. 2, the main body portion 26c is bent at a position overlapping the rotary shaft 17 in a plan view and extends in one axial direction. The other end of the main body portion 26c is connected to the second throttle 26a. As described above, the second throttle 26a is formed in the bottom dead center side blocking portion 16e of the valve plate 16. The second throttle 26a opens at the bottom dead center side blocking surface 16d. As a result, the second communication passage 26 is connected to the cylinder bore 12a located near the bottom dead center via the second throttle 26a.

The volume adjustment mechanism 11c changes the volume of the chamber 25. In this embodiment, the volume adjustment mechanism 11c has a piston 30 and an adjustment screw 31. The piston 30 is inserted into the chamber 25 so that it can move back and forth in a first direction. The adjustment screw 31 moves the piston 30 back and forth in the first direction when turned. The volume adjustment mechanism 11c can change the volume of the chamber 25 by moving the piston 30 back and forth using the adjustment screw 31.

<Operation of hydraulic pump>
The hydraulic pump 1 (more specifically, the hydraulic pump body 29) operates as follows. That is, the drive source (not shown) drives the rotary shaft 17, causing the cylinder block 12 to rotate about the axis L1. Then, the connection destination of the cylinder port 12b is switched between the suction port 16a and the discharge port 16b. Also, as the cylinder block 12 rotates, the multiple pistons 13 rotate about the axis L1 and reciprocate in the cylinder bores 12a. As a result, the hydraulic fluid is sucked into the cylinder bores 12a through the suction port 16a, and then the hydraulic fluid is discharged from the cylinder bores 12a to the discharge port 16b. In this manner, the hydraulic pump 1 discharges the hydraulic fluid. In addition, in the hydraulic pump 1, the tilt angle of the swash plate 14 is adjusted by the regulator 15. Then, the stroke amount of the pistons 13 is adjusted. This allows the discharge amount of the hydraulic pump 1 to be adjusted.

In addition, in the hydraulic pump 1, the pulsation suppression mechanism 28 achieves the following vibration absorption function and backflow suppression function. That is, in the pulsation suppression mechanism 28 of this embodiment, the resonator 31 is mainly composed of the first communication passage 24 and the chamber 25. The resonator 31 functions in the same manner as, for example, a Helmholtz resonator. That is, the resonator 31 reduces the pulsation of the working fluid flowing through the discharge passage 23 by the vibration absorption function. In addition, in the pulsation suppression mechanism 28 of this embodiment, the backflow suppression mechanism 32 is mainly composed of the chamber 25 and the second communication passage 26. The backflow suppression mechanism 32 supplies the working fluid (more specifically, the pressurized fluid) stored in the chamber 25 to the cylinder bore 12a located near the bottom dead center via the second communication passage 26. Therefore, the internal pressure of the cylinder bore 12a located near the bottom dead center can be increased. This prevents the hydraulic fluid in the discharge passage 23 from flowing back into the cylinder bore 12a when the cylinder bore 12a is connected to the discharge port 16b. Therefore, the backflow prevention mechanism 32 reduces the pulsation of the hydraulic fluid flowing through the discharge passage 23 by its backflow prevention function.

In addition, in the pulsation suppression mechanism 28, the second communication passage 26 has the second throttle 26a. Therefore, the backflow suppression mechanism 32 can reduce the pulsation of the working fluid flowing through the discharge passage 23 when the cylinder block 12 shown in FIG. 8 rotates at a low speed (for example, in the range of 1000 rpm to 3000 rpm). In more detail, the backflow suppression mechanism 32 can reduce the pulsation of the working fluid in the low speed rotation range (i.e., low frequency band) more than the pulsation suppression mechanism 28. On the other hand, in the pulsation suppression mechanism 28, the first throttle 24a constituting the resonator 31 has a flow path cross-sectional area larger than the second throttle 26a. Therefore, in the resonator 31, the pulsation of the working fluid flowing through the discharge passage 23 when the cylinder block 12 in FIG. 8 rotates at a high speed (for example, 3000 rpm or more) can be reduced. That is, the resonator 31 can reduce the pulsation of the working fluid in the high-speed rotation range (i.e., high-frequency band) more effectively than the backflow suppression mechanism 32.

In addition, in the pulsation suppression mechanism 28, the magnitude of the pulsation to be reduced in the resonator 31 can be adjusted by changing the volume of the chamber 25 by the volume adjustment mechanism 11c. In addition, by increasing the volume of the chamber 25, the speed range in which the pulsation can be reduced in the resonator 31 shifts to a smaller one (i.e., a lower frequency band of the pulsation). Conversely, by decreasing the volume of the chamber 25, the speed range in which the pulsation can be reduced in the resonator 31 shifts to a larger one (i.e., a higher frequency band of the pulsation). In addition, in the pulsation suppression mechanism 28, the flow path cross-sectional area (e.g., the throttling diameter) of the first throttling 24a is adjusted. In this embodiment, the flow path cross-sectional area (e.g., the throttling diameter) of the first throttling 24a is adjusted by inserting the throttling member 24d having a different flow path cross-sectional area of the inner hole into the throttling accommodating portion 24c. As a result, in the pulsation suppression mechanism 28, the frequency band of the pulsation to be reduced (more specifically, the peak of the frequency band) can be adjusted. Therefore, the degree of pulsation reduction can be adjusted by changing the volume of the chamber 25, and the frequency band of pulsation to be reduced can be adjusted by changing the flow path cross-sectional area of the first throttle 24a. In this way, the pulsation suppression mechanism 28 forms a resonator 31 and a backflow suppression mechanism 32 using one chamber 25. Therefore, it is possible to prevent the hydraulic pump 1 from becoming large.

In the hydraulic pump 1 of this embodiment, the chamber 25 is connected to the discharge passage 23 via the first communication passage 24. Therefore, the chamber 25 and the first communication passage 24 form a resonator 31. The vibration absorption function of the resonator 31 can suppress the pulsation of the working fluid flowing through the discharge passage 23. The chamber 25 is also connected to the second communication passage 26, which has a second throttle 26a and opens at the bottom dead center side blocking surface 16d. Therefore, the chamber 25 is connected to the cylinder bore 12a located near the bottom dead center via the second communication passage 26. Therefore, the chamber 25 and the second communication passage 26 form a backflow suppression mechanism 32. The backflow suppression mechanism 32 can increase the internal pressure of the cylinder bore 12a until the connection destination of the cylinder bore 12a switches from the suction port 16a to the discharge port 16b. This makes it possible to prevent the hydraulic fluid from flowing back from the discharge passage 23 to the cylinder bore 12a when the connection destination of the cylinder bore 12a is switched to the discharge port 16b (i.e., to achieve a backflow prevention function). Therefore, it is possible to reduce pulsation caused by the backflow of the hydraulic fluid to the cylinder bore 12a. Furthermore, the first throttle 24a has a larger flow path cross-sectional area than the second throttle 26a. Therefore, the backflow prevention mechanism 32 mainly reduces pulsation in the low frequency band. On the other hand, the resonator 31 reduces pulsation in the higher frequency band than the backflow prevention mechanism 32. Therefore, it is possible to reduce pulsation in a wide frequency band by using one chamber 25.

In addition, in the hydraulic pump 1 of this embodiment, the chamber block 11b is separate from the casing body 11a. The chamber 25 is formed in the chamber block 11b. Therefore, when it is necessary to reduce pulsation in the high frequency band, the chamber block 11b can be attached to the casing body 11a, and when it is not necessary, the chamber block 11b can be removed from the casing body 11a.

Furthermore, in the hydraulic pump 1 of this embodiment, the throttle member 24d is inserted through the accommodation opening 24e and accommodated in the throttle accommodation portion 24c. Therefore, the throttle member 24d can be replaced, and the replacement is easy. In addition, by replacing it, the flow passage cross section of the first throttle 24a, etc. can be changed. This makes it possible to adjust the frequency band of pulsation to be reduced.

Furthermore, in the hydraulic pump 1 of this embodiment, the second throttle 26a is formed in the valve plate 16. Since the second throttle 26a is formed in the valve plate 16, which is separate from the casing 11, it is easy to form the second throttle 26a.

Furthermore, in the hydraulic pump 1 of this embodiment, the first throttle 24a is formed in the casing 11 by attaching a throttle member 24d to the casing 11. Therefore, by replacing the throttle member 24d, the flow passage cross section of the first throttle 24a can be changed. This makes it possible to adjust the frequency band of pulsation to be reduced.

Furthermore, the hydraulic pump 1 of this embodiment is further provided with a volume adjustment mechanism 11c that changes the volume of the chamber 25. Therefore, the volume of the chamber 25 can be changed by the volume adjustment mechanism 11c. This makes it possible to adjust the degree of pulsation reduction and the frequency band of pulsation that can be reduced.

Furthermore, in the hydraulic pump 1 of this embodiment, the chamber 25 has a volume larger than the cylinder bore 12a. This provides a significant reduction in the pulsation of the hydraulic fluid flowing through the discharge passage 23, particularly due to the vibration absorption function.

Furthermore, in the hydraulic pump 1 of this embodiment, the chamber 25, together with the first communication passage 24, constitutes a resonator 31, and together with the second communication passage 26 and the second orifice 26a, constitutes a backflow suppression mechanism 32. The resonator 31 reduces pulsations in a higher frequency band than the backflow suppression mechanism 32. The backflow suppression mechanism 32 reduces pulsations in a lower frequency band more than the resonator 31. Therefore, pulsations in a wide frequency band can be reduced.

<Other embodiments>
The hydraulic pump 1 of the present embodiment may be a fixed displacement hydraulic pump or a bent-axis pump. The hydraulic pump 1 of the present embodiment may also be applied to a tandem pump configured by arranging the hydraulic pumps 1 in series, or a parallel pump configured by arranging the hydraulic pumps 1 in parallel.

In this embodiment, the casing 11 is composed of a casing body 11a and a chamber block 11b that are constructed separately from each other, but they may also be constructed integrally (i.e., the casing 11 may be constructed as a single unit).

The casing 11 does not necessarily have to have a volume adjustment mechanism 11c, and the chamber 25 may have a fixed volume. Also, the chamber 25 does not necessarily have to have a volume larger than the cylinder bore 12a.

In the hydraulic pump 1 of this embodiment, the second throttle 26a is formed in the valve plate 16, but it may also be formed in the casing 11. Also, the first communication passage 24 may be formed from the casing body 11a to the chamber block 11b, like the second communication passage 26. Furthermore, the first throttle 24a does not necessarily have to be constituted by the throttle member 24d, and may be formed directly in the chamber block 11b.

Exemplary embodiments
a valve plate provided in the casing and having an intake port connected to the intake port and an exhaust port connected to the exhaust port, the valve plate including a plurality of cylinder bores and sliding on the valve plate; and a plurality of pistons inserted into the cylinder bores and reciprocating within the cylinder bores. The casing is further provided with a first communication passage having a first throttle, a chamber, and a second communication passage extending to the valve plate, the first communication passage communicating with the exhaust port and the chamber, the chamber storing the working fluid introduced from the exhaust port via the first communication passage, the second communication passage having a second throttle, opening at a bottom dead center side blocking surface between the intake port and the exhaust port of the valve plate and connected to the chamber, the first throttle having a flow path cross-sectional area larger than that of the second throttle.

According to the above aspect, the chamber is connected to the discharge passage through the first communication passage. Therefore, the chamber and the first communication passage constitute a resonator. The vibration absorbing function of the resonator can suppress the pulsation of the working fluid flowing through the discharge passage. The chamber is also connected to a second communication passage having a second throttle and opening at the bottom dead center side blocking surface. Therefore, the chamber 25 is connected to the cylinder bore located between the suction port and the discharge port on the bottom dead center side through the second communication passage. Therefore, the chamber and the second communication passage constitute a backflow suppression mechanism. The backflow suppression mechanism can increase the internal pressure of the cylinder bore until the connection destination of the cylinder bore switches from the suction port to the discharge port. This makes it possible to suppress the working fluid from flowing back from the discharge passage to the cylinder bore when the connection destination of the cylinder bore switches to the discharge port (i.e., to achieve the backflow suppression function). Therefore, the pulsation caused by the backflow of the working fluid to the cylinder bore can be reduced. Furthermore, the first throttle has a flow passage cross-sectional area larger than that of the second throttle. Therefore, the backflow suppression mechanism mainly reduces pulsation in the low frequency band. On the other hand, the resonator mainly reduces pulsation in the higher frequency band than the backflow suppression mechanism. Therefore, a single chamber can reduce pulsation in a wide frequency band. Also, a single chamber can be used to configure both the resonator and the backflow suppression mechanism.

In the hydraulic pump of the second aspect, in the hydraulic pump of the first aspect, the casing includes a casing body and a chamber block, the suction passage and the discharge passage are formed in the casing body, the chamber block is separate from the casing body, and the chamber is formed in the chamber block.

In accordance with the above aspect, the chamber block is separate from the casing body. The chamber is formed in the chamber block. Therefore, the chamber block can be attached to the casing body when it is necessary to reduce pulsation, and can be removed from the casing body when it is not necessary.

The hydraulic pump in the third aspect is the hydraulic pump in the second aspect, wherein the chamber block is formed with the first communication passage and a housing opening, the first communication passage has a passage portion and a throttle housing portion arranged to intersect with each other, and a throttle member forming the first throttle, the throttle housing portion extends in one predetermined direction and houses the throttle member, and the housing opening is formed on an extension of the throttle housing portion in the chamber block.

In accordance with the above aspect, the accommodation opening is formed on an extension line of the throttle accommodation portion in the chamber block. Therefore, the throttle member can be inserted from the accommodation opening and accommodated in the throttle accommodation portion. Therefore, the throttle member can be replaced, and the replacement is easy. Furthermore, by replacing it, the flow passage cross section of the first throttle, etc. can be changed. This makes it possible to adjust the frequency band of pulsation to be reduced.

In the fourth aspect of the hydraulic pump, the valve plate is formed with the second restriction in the hydraulic pump of any one of the first to third aspects.

In accordance with the above aspect, the second restriction is formed in the valve plate. Since the second restriction is formed in the valve plate that is separate from the casing, it is easy to form the second restriction.

In the hydraulic pump of the fifth aspect, the first restriction is formed in the casing by attaching a restriction member to the casing in the hydraulic pump of any one of the first to fourth aspects.

In accordance with the above aspect, the first throttle is formed in the casing by attaching a throttle member to the casing. Therefore, by replacing the throttle member, the flow passage cross section of the first throttle can be changed. This makes it possible to adjust the frequency band of pulsation to be reduced.

In a sixth aspect of the hydraulic pump, the casing of any one of the first to fifth aspects further includes a volume adjustment mechanism that changes the volume of the chamber.

According to the above aspect, a volume adjustment mechanism for changing the volume of the chamber is further provided. Therefore, the volume of the chamber can be changed by the volume adjustment mechanism. This makes it possible to adjust the degree of pulsation reduction and the frequency band of pulsation that can be reduced.

In the seventh aspect of the hydraulic pump, the chamber has a volume larger than the cylinder bore in the hydraulic pump of any one of the first to sixth aspects.

In accordance with the above aspect, the chamber has a larger volume than the cylinder bore. Therefore, a significant reduction effect can be obtained with respect to the pulsation of the hydraulic fluid flowing through the discharge passage, particularly due to the vibration absorption function.

In an eighth aspect, the hydraulic pump includes a casing in which an intake passage through which hydraulic fluid is introduced and a discharge passage through which hydraulic fluid is discharged are formed, a valve plate provided in the casing in which an intake port connected to the intake passage and a discharge port connected to the discharge passage are respectively formed, a cylinder block including a plurality of cylinder bores and sliding on the valve plate, a plurality of pistons inserted into each of the cylinder bores and reciprocating within the cylinder bores, the casing including a first communication passage having a first restriction, a chamber, and a second communication passage extending to the valve plate, the first communication passage communicating the discharge passage with the chamber, and the chamber stores the working fluid guided from the discharge passage through the first communication passage, the second communication passage has a second throttle, opens at a bottom dead center side blocking surface between the intake port and the discharge port of the valve plate, and is connected to the chamber, the chamber constitutes a resonator that reduces the pulsation of the working fluid flowing through the discharge passage together with the first communication passage, and constitutes a backflow suppression mechanism that reduces the pulsation of the working fluid flowing through the discharge passage by suppressing backflow to the cylinder bore together with the second communication passage and the second throttle, the backflow suppression mechanism reduces pulsation in the low frequency band, and the resonator reduces pulsation in the high frequency band.

According to the above aspect, the chamber, together with the first communication passage, constitutes a resonator, and the second communication passage and the second throttle constitute a backflow suppression mechanism. The resonator reduces pulsation more than the backflow suppression mechanism in the high frequency band. The backflow suppression mechanism reduces pulsation more than the resonator in the low frequency band. Therefore, pulsation can be reduced over a wide frequency band. In addition, the resonator and the backflow suppression mechanism can be formed by a single chamber.

REFERENCE SIGNS LIST 1 hydraulic pump 11 casing 11a casing body 11b chamber block 11c volume adjustment mechanism 12 cylinder block 12a cylinder bore 13 piston 16 valve plate 16a suction port 16b discharge port 22 suction passage 23 discharge passage 24 first communication passage 24a first throttle 24c throttle housing portion 24d throttle member 24e housing opening 25 chamber 26 second communication passage 26a second throttle 31 resonator 32 backflow suppression mechanism

Claims (8)

a casing in which a suction passage through which the working fluid is introduced and a discharge passage through which the working fluid is discharged are formed;
a valve plate provided in the casing, the valve plate having a suction port connected to the suction passage and a discharge port connected to the discharge passage;
a cylinder block including a plurality of cylinder bores and configured to slide on the valve plate;
a plurality of pistons inserted into each of the cylinder bores and reciprocating within the cylinder bores;
The casing further includes a first communication passage having a first throttle, a chamber, and a second communication passage extending to the valve plate,
the first communication passage communicates the discharge passage with the chamber,
the chamber stores the hydraulic fluid guided from the discharge passage via the first communication passage,
the second communication passage has a second throttle, opens at a bottom dead center side blocking surface between the suction port and the discharge port of the valve plate, and is connected to the chamber;
The first restriction has a larger flow cross-sectional area than the second restriction. The casing includes a casing body and a chamber block.
The casing body is formed with the suction passage and the discharge passage,
the chamber block is separate from the casing body,
The hydraulic pump of claim 1 , wherein the chamber is formed in the chamber block. The chamber block is formed with the first communication passage and a receiving opening,
the first communication passage has a passage portion and a throttle accommodating portion that are arranged to intersect with each other, and a throttle member that forms the first throttle,
The throttle housing portion extends in one predetermined direction and houses the throttle member,
The hydraulic pump according to claim 2 , wherein the accommodation opening is formed on an extension line of the throttle accommodation portion in the chamber block. The hydraulic pump according to claim 1, wherein the second restriction is formed in the valve plate. The hydraulic pump according to claim 1, wherein the first restriction is formed in the casing by attaching a restriction member to the casing. The hydraulic pump according to claim 1, wherein the casing further includes a volume adjustment mechanism for changing the volume of the chamber. The hydraulic pump of claim 1, wherein the chamber has a volume larger than the cylinder bore. a casing in which a suction passage through which the working fluid is introduced and a discharge passage through which the working fluid is discharged are formed;
a valve plate provided in the casing, the valve plate having a suction port connected to the suction passage and a discharge port connected to the discharge passage, the valve plate having a suction port connected to the discharge passage and a discharge port formed therein;
a cylinder block including a plurality of cylinder bores and configured to slide on the valve plate;
a plurality of pistons inserted into each of the cylinder bores and reciprocating within the cylinder bores;
the casing includes a first communication passage having a first restriction, a chamber, and a second communication passage extending to the valve plate;
the first communication passage communicates the discharge passage with the chamber,
the chamber stores the hydraulic fluid guided from the discharge passage via the first communication passage,
the second communication passage has a second throttle, opens at a bottom dead center side blocking surface between the suction port and the discharge port of the valve plate, and is connected to the chamber;
the chamber, together with the first communication passage, constitutes a resonator that reduces pulsation of the working fluid flowing through the discharge passage, and, together with the second communication passage and the second throttle, constitutes a backflow suppression mechanism that suppresses backflow into the cylinder bore, thereby reducing pulsation of the working fluid flowing through the discharge passage,
The backflow suppression mechanism reduces pulsation in a low frequency band,
The resonator reduces pulsation in a high frequency band.

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