JPH04330384A - Delivery pressure pulsation reducing mechanism for liquid pump - Google Patents

Abstract

PURPOSE:To reduce the occurrence of delivery pulsation of a liquid pump throughout a wide range of the number of revolutions. CONSTITUTION:A variable displacement swash plate type axial plunger pump 10 changes the inclination angle of a non-rotating swash plate 18 by means of a capacity control piston 17 to vary a delivery amount. In control through which a delivery amount is maintained at a constant value when the number of revolutions of a rotary shaft 14 is fluctuated, a control oil pressure having magnitude responding to the number of revolutions is fed to a hole part 13b to move the piston 17. In structure shown in a figure, displacement of the piston 17 is transferred to a spool 320 through a rod 312, and the volume of a resonance chamber 322 and the length of a communicating pipe between a delivery passage 30 and a cylindrical passage 323 are simultaneously changed. Since the resonance frequency of a resonator 300 is changed in response to the number of revolutions and thus the frequency of delivery pulsation, a resonance frequency can coincide with the frequency of pulsation in any running state, and the occurrence of delivery pressure pulsation can be reduced in a wide range of the number of revolutions.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a mechanism for reducing the discharge pressure pulsation of a liquid pump, and in particular, the present invention relates to a mechanism for reducing the discharge pressure pulsation of a liquid pump. The present invention relates to a mechanism that can reduce the pulsation.

0002

[Prior Art] First method for reducing discharge pressure pulsation of a liquid pump
The prior art is described in Japanese Utility Model Application Publication No. 62-11730. This conventional technology connects a viscoelastic substance filled in a damper container to the discharge side of the pump via an elastic membrane, and reduces discharge pressure pulsations through the vibration damping effect of this viscoelastic substance. . Changes in pulsation frequency are dealt with by adjusting the viscoelasticity of the viscoelastic material.

[0003] Furthermore, a second prior art is described in Japanese Patent Laid-Open No. 2-47638. This connects a resonance chamber to the discharge side of the pump, and since the resonance frequency is determined as an almost constant value depending on the dimensions of the resonance chamber, it absorbs and reduces the pump's discharge pressure pulsations that match the resonance frequency. Can be done. In this example, in order to avoid stagnation of liquid in the resonance chamber, multiple communication passages were provided between the resonance chamber and the discharge side conduit to allow liquid to flow within the resonance chamber. There are characteristics.

0004

[Problems to be Solved by the Invention] In the first prior art, if the spring constant of the viscoelastic material is set small, it cannot adapt to large pulsations in the high frequency region; If the spring constant is set to a large value, there is a problem in that it cannot be expected to be effective against relatively small pulsations. In the second conventional technique, it is effective for a specific resonance frequency determined by the dimensions of the resonance chamber, but since the resonance frequency is a value specific to the resonance chamber,
If the frequency of the pump's discharge pressure pulsations varies, there is no effect unless the pulsation frequency matches the resonance frequency.

[0005] In the field of pneumatics, there are systems in which a variable frequency resonator whose resonance frequency changes is installed in a pipe line, and it is possible to use this means for a liquid pump, but in general, in this type of system, This includes a sensor that detects the frequency, a microcomputer into which the output signal of the sensor is input, and a linear type that mechanically adjusts a part of the resonator structure to change the resonant frequency based on the output of the microcomputer. It is necessary to provide several actuators, which not only results in an expensive and complicated configuration, but also
Mechanically, it is usually difficult to widen the frequency change range.

[0006] In a liquid pump, even if the frequency of discharge pressure pulsation fluctuates significantly with changes in the driving rotation speed of the pump, the present invention provides a solution to the fluctuation of the pulsation frequency (or the rotation speed of the drive shaft). An object of the invention is to provide a pulsation reduction mechanism that can follow a wide range and effectively reduce pulsation, and that is not structurally complex and can be manufactured at low cost.

[0007]

[Means for Solving the Problems] As a means for solving the above-mentioned problems, the present invention reduces the pulsation of the discharge pressure in a liquid pump in which the driving rotation speed fluctuates and the pulsation frequency of the discharge pressure changes accordingly. a resonance chamber that is provided to communicate with the discharge passage of the liquid pump; a control hydraulic pressure generating means that generates a control hydraulic pressure having a value corresponding to a varying drive rotational speed or pulsation frequency; a movable control member to be changed; and a hydraulic system that moves the movable control member by the control oil pressure supplied from the control oil pressure generating means so that the resonance frequency of the resonance chamber follows the change in the pulsation frequency of the discharge pressure. A discharge pressure pulsation reduction mechanism is provided, which is provided with an interlocking means.

Further, the liquid pump performs constant flow rate control, and further includes a capacity control means for generating a control oil pressure corresponding to the driving rotation speed, and a liquid pump that is moved by the control oil pressure supplied from the capacity control means. In the case of a variable displacement liquid pump having a displacement control piston that changes the discharge capacity of the liquid pump, the displacement is adjusted such that the resonance frequency of the resonance chamber follows the change in the pulsation frequency of the discharge pressure. A discharge pressure pulsation reduction mechanism is provided, which includes a movable control member that changes the resonance frequency of the resonance chamber by mechanically or hydraulically interlocking with a control piston.

[0009]

[Operation] When the drive rotation speed of the liquid pump changes and the pulsation frequency of the discharge pressure changes accordingly, a control oil pressure having a value corresponding to the changing drive rotation speed or pulsation frequency is generated in the control oil pressure generating means. The control hydraulic pressure moves the movable control member of the resonance chamber via hydraulic interlocking means, thereby changing the resonance frequency of the resonance chamber to follow changes in the pulsation frequency of the discharge pressure. Therefore, even if the driving rotation speed of the liquid pump fluctuates and the pulsation frequency of the discharge pressure changes, the resonant frequency of the resonance chamber will automatically change accordingly, so no matter what the operating state, resonance will not occur. The chamber exerts a pulsation reducing effect.

The target liquid pump is of a variable discharge capacity type, and in order to perform control to maintain a constant flow rate, a capacity control means for generating control hydraulic pressure corresponding to the drive rotation speed, and a capacity control means are provided. In the case where a displacement control piston is provided which changes the discharge capacity of the liquid pump by moving according to the control hydraulic pressure supplied from the means, the control hydraulic pressure generating means or hydraulic interlocking means generates the control hydraulic pressure having a value corresponding to the pulsation frequency. There is no need to provide a special mechanism for reducing the discharge pressure pulsation, and the position (displacement) of the displacement control piston corresponds to the driving rotation speed and therefore the pulsation frequency of the discharge pressure. Mechanically or hydraulically interlocked movable control members automatically change the resonant frequency of the resonant chamber, whatever the operating conditions.
The resonance chamber exerts a pulsation reducing effect.

[0011]

[Embodiment] In FIG. 1, reference numeral 10 denotes a variable displacement swash plate type axial plunger pump, and this pump 10 has a disc-shaped cover 13 coaxially attached to the opening of a cylindrical housing 11 via a sealing material 12. It is configured. Reference numeral 14 denotes a rotating shaft which is supported in the housing 11 and cover 13 via bearings 15a and 15b so as not to be movable in the axial direction. Above this rotating shaft 14 is a cylindrical cylinder portion 1.
3a is arranged to extend from the cover 13 into the housing 11, and a displacement control piston 17 (simply referred to as piston 17) that changes the discharge displacement of the pump is fitted in the cylinder 13a so as to be freely slidable in the axial direction. and compression spring 2
It is balanced with a biasing force of 50.

The swash plate 18 has its center hole 19 connected to the rotation axis 14.
At the same time, the hemispherical base 20 is loosely fitted into the holder 21.
The swash plate 18 has a substantially spherical recess 23 on the upper side and is in contact with the head 17a of the piston 17 for relative rotational movement. . The basic structure of the pump is the same as that of conventional pumps, so a detailed explanation will be omitted, but 1 is a cylinder that is connected to a rotating shaft 14 and rotates, and 3 is several plungers inserted into the opening of cylinder 1. , is given a reciprocating motion by the swash plate 18 and pressurizes the liquid within the cylinder 1. A discharge passage 30 is provided within the cover 13 for discharging pressurized liquid.

Next, a resonator 30 formed within the cover 13
The configuration of 0 will be explained in detail. The bush 310 is a cylindrical member having two large and small holes 310a and 310b bored in its center, and the hole 310a is provided with a communication hole 310c that connects the discharge passage 30 and the hole 310a in the circumferential direction. Furthermore, this bush 310 is fixed to the cover 13 by a circlip 311 so as not to be movable in the axial direction. A communication hole 13c connecting the hole 13b in which the piston 17 is fitted and the large diameter hole 310a of the bush 310 is bored in the left end of the cylinder portion 13a, and a cylinder 13c is slidable in the axial direction within the communication hole 13c. A bar-shaped rod 312 is fitted into the piston 17, and the right end of the rod 312 is in contact with the left end of the piston 17. Further, on the left side of the rod 312, a spool 320 having four large and small cylindrical parts is fitted so as to be slidable in the axial direction into a cylindrical hole 321 provided in the cover 13.
The right end of the middle diameter portion 320a of the spool 320 is connected to the rod 31.
2, a resonance chamber 322 is formed in the hole 321, and this resonance chamber 322 is made up of the bush small diameter hole 310b and the spool medium diameter portion 3 pushed into the approximate center of the bush small diameter hole 310b.
It communicates with the discharge passage 30 through a cylindrical passage 323 formed by the discharge passage 20a.

A spring 330 is installed on the left side of the spool 320, and its right end contacts the large diameter portion 320b of the spool 320, and its left end contacts a hole 341 provided in a disc-shaped screw member 340, which will be described later. It comes into contact with the bottom surface and urges the spool 320 to the right. This disc-shaped threaded member 340 has a threaded portion formed on the outermost diameter, and the cover 1
3, and an annular groove is provided in the middle diameter part of the O.
The ring 342 maintains a seal with the outside of the pump. Further, the spool 320 and the disc-shaped screw member 3
A chamber 343 formed by 40 communicates with the discharge passage 30 through a communication passage 344 .

In the variable displacement pump shown in FIG. 1, in order to obtain the rotation speed-flow rate characteristic shown in FIG. 3, the theoretical discharge amount is given by equation (2) shown in FIG. Therefore, it is necessary to change the angle α of the swash plate 18 as shown in FIG. This change in the angle α of the swash plate 18 is achieved by introducing hydraulic pressure into the cylinder hole 13b by means of a capacity control means (not shown) consisting of a control valve and an appropriate hydraulic pressure source, and causing the piston 17 to slide in the axial direction. This is achieved by rotating the
The stroke of the piston 17 at this time is shown as S in FIG.

Here, the resonator is usually formed in the structure shown in FIG. 2, and its resonant frequency is expressed by equation (1) shown in FIG. And in order to change this resonance frequency f,
It is necessary to change one or more of the following three: opening cross-sectional area A, resonance chamber volume V, and communication pipe length L.

In FIG. 1, the cross-sectional area of the cylindrical passage 323 is defined as the opening cross-sectional area, and the length in which the medium diameter portion 320a of the spool 320 and the cylindrical passage 323 overlap in the axial direction is defined as the communicating pipe length 325. Pressure oil discharged from the pump 10 passes through the discharge passage 30 and is supplied to the resonance chamber 322 via the cylindrical passage 323. Moreover, since the chamber 343 on the left side of the spool 320 also communicates with the discharge passage through the communication passage 344, pressure oil can freely flow in and out between the chamber 343 and the discharge passage 30. Therefore, the hydraulic forces acting on the spool 320 from both left and right directions are equal. Also rod 3
The force due to the hydraulic pressure acting on the left end of the rod 312 is only a minute force because the diameter of the rod 312 is made small, and therefore, the force that causes the piston 17 to slide is not generated.

In this state, when the aforementioned capacity control means (not shown) introduces hydraulic pressure into the cylinder hole 13b and the piston 17 strokes to the right, the spool 320
is urged rightward by the spring 330, so it slides along with the rod 312 following the piston 17, and the volume of the resonance chamber 322 and the length of the communicating tube 325 are equal to the piston 1.
It changes linearly as shown in FIGS. 4(a) and 4(b) for a stroke of 7.

Now, if the variation range of the pulsation frequency is set from 225 Hz to 900 Hz, the resonance frequency also needs a variation range four times the same as the pulsation frequency. Since the resonant frequency is expressed by equation (1) as described above, in order to change the resonant frequency over a range of 4 times, it is necessary to change the inside of √ by 16 times. In this embodiment, as described above, the volume (V) of the resonance chamber 322 and the length of the communication tube 325 (L) each change about 4 times with respect to the piston stroke, so the overall change is 16 times. Therefore, as shown in FIG. 5, the resonance frequency can be made approximately linearly proportional to the change in the pulsation frequency. As a result of the above effects, a pulsation reduction effect due to resonance can always be obtained with respect to changes in pulsation frequency due to changes in rotational speed. In this way, in the case of a variable displacement liquid pump that performs constant flow rate control, the displacement control means generates a control hydraulic pressure corresponding to the driving rotation speed and supplies it to the piston 17, so that the position of the piston 17 ( displacement)
Since it corresponds to the rotational speed, it also corresponds to the discharge pulsation frequency. Therefore, there is an advantage that by moving the spool 320 in conjunction with the piston 17, the resonance frequency can also be changed at the same time. However, even in non-variable displacement liquid pumps, if a control hydraulic pressure generation means consisting of a control valve similar to the displacement control means is specially installed for this purpose, the discharge pressure pulsation caused by fluctuations in the driving rotation speed can be reduced. The resonant frequency of the resonant chamber that performs this can be changed.

A second embodiment will be explained using FIG. 6. Whereas in the first embodiment, the resonant frequency was changed by changing the length L of the communication tube of the resonator and the volume V of the resonance chamber, in this example, the length L of the communication tube and the cross-sectional area A of the opening were changed. The second embodiment differs from the first embodiment only in the configuration of the resonator. Therefore, first, the resonator 35
The configuration of 0 will be explained. The collar 351 has a large diameter hole 351
It is a cylindrical member having a conical hole 351b and a conical hole 351b, and the large diameter side of the conical hole 351b opens into the large diameter hole 351a. This large diameter hole 351a forms a resonance chamber together with the wall surface of the cover 13. Also this color 3
51 is fixed to the cover 13 so as not to be movable in the axial direction by a screw member 352 having a threaded portion formed on the outer periphery.

This screw member 352 consists of a large-diameter threaded portion and a cylindrical portion with a smaller diameter than the threaded portion, and the cylindrical portion has two large and small annular grooves 352a and 352b formed therein, and a small annular groove 3.
An O-ring 353 is installed at 52b to maintain sealing inside the pump. Further, a small diameter hole 352c is bored approximately at the center of the cylindrical portion, and the small diameter hole 352c and the annular groove 3
A communication path 352d connecting the 52a is formed in the radial direction. Further, a communication passage 354 connecting the annular groove 352a and the discharge passage 30 is formed in the cover 13. Further, at the left end of the cylinder portion 13a, there is a communication hole 3 that connects the hole 13b in which the piston 17 is fitted and the collar large diameter hole 351a.
A rod 356 having a conical member 356a formed at its tip is fitted into the communication hole 355 so as to be slidable in the axial direction.

Further, a spring 357 is installed on the left side of the rod 356, and its right end contacts the small diameter side of the conical member 356a of the rod 356, and its left end contacts the small diameter hole 352c bored in the threaded member 352. It comes into contact with the bottom surface and urges the rod 356 to the right in the figure. The amount of overlap between the conical member 356a of the rod 356 and the conical hole 351b of the collar is the length of the communicating tube, and the area of the passage formed by each tapered surface is the opening cross-sectional area.

The operation of the second embodiment will be explained. As in the first embodiment, the rod 35 follows the movement of the piston 17.
6 strokes, the length of the communicating tube changes as shown in FIG. 4(b) because the amount of overlap between the conical portions 351b and 356a changes. At the same time, the cross-sectional area of the opening changes as shown in FIG. 7 because each surface is tapered. As a result, the resonant frequency shown by equation (1) changes approximately squarely within √ in equation (1), as the numerator A becomes larger, the denominator L becomes smaller, or vice versa. As shown in 5, the pulsation reduction effect can be obtained by making the resonant frequency approximately linearly proportional to the change in the pulsation frequency.

A third embodiment will be explained using FIG. 8. In contrast to the first and second embodiments in which two values in equation (1) were changed, this example changes all three values of A, V, and L to change the resonant frequency. It is something that changes. First, the configuration will be explained. FIG. 8 shows an enlarged view of the resonator, and other parts such as the variable displacement pump section are the same as those in the first and second embodiments.

The screw member 401 is a donut-shaped member with a threaded portion formed on the outer periphery and a through hole provided in the center, and thereby fixes the collar 402 to the cover 13 so as not to be movable in the axial direction. This collar 402 has a hole 402 approximately in the center.
It is a cylindrical member in which a conical hole 402b is formed, and a radial passage 402c is formed from the hole 402a toward the outer periphery. Further, an annular groove 403a is formed in the hole 403 of the cover 13 into which the collar 402 is fitted, and the annular groove 403a and the discharge passage 30 are connected by a communication passage 404. A communication hole 405 is bored between the cylinder hole 13b into which the piston 17 is fitted and the collar hole 402a, and a rod-shaped rod is inserted into the communication hole 405 so as to be slidable in the axial direction. 406 is fitted.

Further, on the left side of this rod 406, a rod-shaped spool 407 having a conical member 407a at the tip is installed, and as in the second embodiment, the conical hole 402b of the collar 402 and the conical member 407a are connected to each other. The tapered surface forms the length of the communicating tube and the cross-sectional area of the opening of the resonator. A cylindrical bush 408 is attached to the left side of the spool 407 so as to be slidable in the axial direction with respect to the cover 13, and the spool 407 and the bush 408 are integrally attached by a fastening means (not shown). There is. A spring 409 is installed on the left side of the spring 409, and the right end of the spring 409 is connected to the bush 409.
The left end is in contact with the left end surface of plug 4, which will be described later.
The bushing 408 is urged to the right by coming into contact with the bottom surface of a hole 410a bored approximately in the center of the bushing 408. As a result, a resonance chamber is formed by the cover 13 and the bush 408.

The plug 410 has an annular groove 410b on its outer periphery.
A cylindrical member with a hole 410a bored in the approximate center thereof,
An O-ring 411 is installed in the annular groove 410b to maintain sealing inside the pump. This plug 410 also includes a threaded member 412 having a threaded portion formed on the outer periphery.
It is fixed immovably to the cover 13 by. Chamber 4 formed by plug 410 and bush 408
13 communicates with the discharge passage 30 through a communication passage 414.

[0028] With the above configuration, this embodiment can obtain a combined effect of the first and second embodiments, so that each of A, L, and V in formula (1) Even if the amount of change is set smaller than in the first and second embodiments, the same effect can be obtained by selecting a shape in which the inside of √ changes squarely. In other words, it is possible to reduce pulsations in a wide range of frequencies.

A fourth embodiment will be explained using FIG. 9. This embodiment is a modification of the first embodiment, in which the length of the communication pipe and the volume of the resonance chamber are changed to change the resonance frequency. First, the configuration will be explained. Similar to FIG. 8, FIG. 9 shows an enlarged view of the resonator portion. The screw member 51 is a donut-shaped member having a threaded portion formed on the outer periphery and a through hole provided in the center, and thereby fixes the cylinder 16 to the cover 13 so as not to be movable in the axial direction. Further, a hole 16a is formed at the left end of the cylinder 16, and the hole in which the piston 17 is fitted communicates with the outside.A rod 52 is fitted into the hole 16a so as to be slidable in the axial direction. equipped with rod 52
The right end of the piston 17 is in contact with the left end of the piston 17 .

Further, on the left side of the rod 52, a plug 53 having three large and small cylindrical portions is fitted so as to be slidable in the axial direction in a cylindrical hole 54 provided in the cover 13.
The right end of the rod 52 contacts the left end of the rod 52 to form a resonance chamber 55 , and this resonance chamber 55 communicates with the discharge passage 30 through a cylindrical passage 56 . Further, a spool 57 consisting of two large and small cylindrical parts is fixed to the plug 53 by a method not shown, and the large diameter part of the spool 57 is attached to the cylindrical passage 53.
The large diameter portion of the spool 57 and the passage 56 are pushed into the approximate center of the spool 57.
A gap 58 is formed between the wall surfaces.

A spring 59 is installed on the left side of the plug 53, and its right end contacts the large diameter portion of the plug 53, and its left end contacts a hole 61 provided in a disc-shaped member 60. The plug 53 is urged rightward by contacting the bottom surface of the plug 53. An annular groove is provided in the outer diameter portion of this member 60, and an O-ring 62 installed in the groove maintains sealing performance with the outside of the pump. And the member 60 is
The cover 13 is fixed to the cover 13 so as not to be movable in the axial direction by a disk-shaped screw member 63 having a threaded portion formed on the outer diameter portion. Further, a chamber 64 formed by the plug 53 and the cylindrical member 60 communicates with the discharge passage 30 through a communication passage 65 .

Next, the operation of the fourth embodiment will be explained. In FIG. 9, the cross-sectional area of the gap 58 formed between the large diameter portion of the spool 57 and the wall surface of the passage 56 is the opening cross-sectional area, and the large diameter portion of the spool 57 and the cylindrical passage 56 overlap in the axial direction. The length of the communication pipe is 70. Pressure oil discharged from the pump passes through the discharge passage 30 and is supplied to the resonance chamber 55 via the gap 58. Furthermore, since the chamber 64 on the left side of the plug 53 also communicates with the discharge passage 30 via the communication passage 65, pressure oil can freely flow in and out between the chamber 64 and the discharge passage 30. Therefore, the hydraulic forces acting on the plug 53 from both left and right directions are equal. Further, the force due to the hydraulic pressure acting on the left end of the rod 52 is only a minute force because the diameter of the rod 52 is formed small, and therefore no force that causes the piston 17 to slide is generated.

In this state, when hydraulic pressure is introduced into the cylinder 16 by the aforementioned capacity control means (not shown) and the piston strokes to the right, the plug 53 is moved by the spring 5.
9 to the right, the rod 52 and the piston 17 slide together, and the volume of the resonance chamber 55 and the length 70 of the communication tube are as shown in FIG. It changes linearly as shown in (b). As a result, as shown in FIG. 5, the resonance frequency can be made approximately linearly proportional to the change in the pulsation frequency. As a result of the above, a pulsation reduction effect due to resonance can always be obtained with respect to changes in pulsation frequency due to changes in rotational speed.

A fifth embodiment will be explained using FIG. 10. In the fourth embodiment, the left chamber 64 of the plug 53 is connected to the communication passage 6.
5 to communicate with the discharge passage 30 through the plug 53 to balance the hydraulic force acting on the plug 53. However, in this embodiment, the force acting from the right side of the plug 80 is balanced by the urging force of the spring 81. Plug 80 for cancellation
This can be used when the discharge pressure acting on the pump is always constant. An annular groove is formed on the outer periphery of the plug 80, and an O-ring 82 installed in the annular groove maintains sealing between the resonator volume 55 and the chamber 83.

A spring 81 is disposed within the chamber 83 and is set to generate a biasing force slightly larger than the force acting from the right side of the plug 80. Further, this spring 81 is held by a cup-shaped cylindrical member 84, and the cylindrical member 84 is fixed to the cover 13 so as not to be movable in the axial direction by a fixing member 85 having a threaded portion formed on the outer periphery. Furthermore, an air vent hole 86 is formed in the center of the cylindrical member 84 and the fixing member 85. The operation is substantially the same as that of the fourth embodiment.

A sixth embodiment will be explained using FIG. 11. Unlike the previous embodiments, this embodiment does not detect the frequency based on the stroke amount of the piston 17, but rather detects the pressure supplied from a capacity control means (not shown) to the cylinder hole 13b into which the piston 17 is fitted. The frequency is detected based on the change. In FIG. 11, the spring 250 that biases the swash plate 18 toward the piston 17 is compressed as shown in FIG. generate force. Since the piston 17 moves in balance with this urging force, the control pressure inside the cylinder hole 13b also gradually increases with the piston stroke as shown in FIG.
Piston stroke and control pressure can be matched in a 1:1 ratio.

Next, the configuration of the resonator of the sixth embodiment will be explained with reference to FIG. 11 again. The screw member 201 consists of two cylindrical parts, large and small, and a threaded part is formed on the outer periphery of the large diameter part so that it is integrally fixed to the cover 13, and the small diameter part is inserted into a hole provided in the cover 13. is fitted in. Further, the sealing material 202 is attached to an annular groove 2 formed in the wall surface of the hole 203 of the cover 13 into which the small diameter portion of the screw member is fitted.
04 and maintains the sealing performance inside the cover 13. The plug 205 has a total of six cylindrical parts (a contact part 205a with the screw member 201, a sliding part 205b with the hole 203, a sliding part 205c with the hole 203a having a smaller diameter than the hole 203, and a spring 206 (described later). Seat part 205d
, a rod portion 205e with the smallest diameter, and a spool portion 205f at the tip), and is fitted into the cover 13 so as to be slidable in the vertical direction in the figure. Also, the cylindrical portion 205b
and 205c are provided with seal members 207a and 207b, respectively. A spring 206 is provided between the plug 205 and the cover 13 and generates a force that urges the plug 205 upward in the figure, and the cover 13 and the plug 205 form a resonance chamber 208. Further, the cover 13 is provided with a communication passage 210 connecting the hole 203a and the discharge passage 30, and within this communication passage 210, the aforementioned spool portion 20 is disposed.
5f is inserted to form a resonator opening and a communicating tube.

A chamber 211 formed by the sliding portion 205c and the cover 13 communicates with the drain via a passage 212. Further, since the chamber 213 formed by the plug 205 and the screw member 201 communicates with the cylinder hole 13b via the passage 214, the control pressure supplied by the capacity control means (not shown) is applied to the cylinder hole 13b. Both chambers 213 are supplied.

Now, assuming that the discharge pressure is always constant, the plug 2
The force that 05 receives upward in the figure due to the discharge pressure is constant with respect to the piston stroke, as shown as F1 in FIG. On the other hand, the force that the plug 205 receives downward in the figure due to the control pressure varies linearly with the piston stroke, as shown in FIG. At this time, since a difference in area is provided between the pressure receiving area receiving the discharge pressure and the pressure receiving area receiving the control pressure, the force due to the control pressure can be made larger than the force due to the discharge pressure. Since the difference ΔF between these forces increases in proportion to the piston stroke, the spring 206 is compressed and the plug 205 moves until it balances this force. As a result, the volume of the resonance chamber 208 and the length of the communicating tube change, so that a pulsation reduction effect can be obtained. In this example, the volume of the resonance chamber and the length of the communication pipe were made variable, but any combination of A, V, and L in equation (1) may be used, and as shown in the third example, All of them may be made variable.

A seventh embodiment will be explained using FIG. 14. This embodiment is a modification of the sixth embodiment, in which the spring 206 in FIG. 11 is changed to a spring 261 having nonlinear characteristics, and the shape of the plug 205 is changed to a plug 262 consisting of four cylindrical parts of different sizes. . Thereby, pulsation can be reduced only by changing the volume of the resonance chamber. Since the spring 261 has the biasing force characteristics shown in FIG. 15 with respect to its deformation amount, the displacement amount of the plug 262 shows the displacement characteristics shown in FIG. 16, and the resonance chamber volume changes approximately squarely. (1) In the formula, pulsation can be reduced only by changing V in A, V, and L.

[0041]

[Effects of the Invention] Since the present invention has the configuration described in the section of the means, even if the pulsation frequency of the discharge pressure changes due to fluctuations in the driving rotation speed of the liquid pump, the change is automatically accommodated. Since the resonant frequency of the resonant chamber changes in accordance with the current, the effect of reducing discharge pulsation by the resonant chamber can be exhibited regardless of the operating state. Therefore, the liquid pump according to the present invention can stably deliver pressurized liquid with less discharge pulsation.

In particular, when the liquid pump is of a variable discharge capacity type, and in order to control the flow rate at a constant rate, the liquid pump has a capacity control means that generates a control oil pressure corresponding to the driving rotation speed, and a control oil pressure supplied from the capacity control means. and a displacement control piston that moves to change the discharge volume of the liquid pump;
There is no need to specially provide a control oil pressure generating means for generating a control oil pressure of a value corresponding to the driving rotation speed or pulsation frequency, or a hydraulic interlocking means for moving a movable control member that changes the resonance frequency of the resonance chamber. There is also the advantage that a similar operation can be performed using part of the capacity control system.

In any case, by carrying out the present invention, a sensor for detecting a pulsating frequency, a microcomputer for processing its output signal, and a microcomputer, which are generally required in this type of system, can be obtained. There is no need to install an actuator or the like to change the resonant frequency of the resonant chamber depending on the output of Pulsation can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing the structure of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the basic configuration of a resonator, as well as a diagram showing an equation for determining the resonant frequency.

FIG. 3 is a diagram showing a formula for determining a theoretical discharge amount in addition to a diagram showing control characteristics of a variable displacement hydraulic pump.

FIGS. 4(a) and 4(b) are both diagrams illustrating the operation of the first embodiment.

FIG. 5 is a diagram illustrating control results.

FIG. 6 is a longitudinal sectional front view showing a second embodiment.

FIG. 7 is a diagram illustrating the operation of the second embodiment.

FIG. 8 is a partial longitudinal sectional front view showing a third embodiment.

FIG. 9 is a partial longitudinal sectional front view showing a fourth embodiment.

FIG. 10 is a partial longitudinal sectional front view showing the fifth embodiment.

FIG. 11 is a longitudinal sectional front view showing a sixth embodiment.

FIG. 12 is a diagram showing the operation of the sixth embodiment.

FIG. 13 is a diagram showing the operation of the sixth embodiment.

FIG. 14 is a longitudinal sectional front view showing a seventh embodiment.

FIG. 15 is a diagram showing the operation of the seventh embodiment.

FIG. 16 is a diagram showing the operation of the seventh embodiment.

[Explanation of symbols]

10...Variable displacement swash plate type axial plunger pump 1
4...Rotating shaft 17...Capacity control piston 18...Swash plate 30...Discharge passage 53, 205, 262...Plug (movable control member) 55
, 208, 322... Resonance chamber 56, 323... Cylindrical passage 57, 2320, 407... Spool (movable control member)
86...Air vent hole 205f...Spool portion 210, 344, 354, 404, 414...Communication path 26
1... Springs with nonlinear characteristics 300, 350... Resonators 312, 356... Rods 330, 357, 409... Spring 351b... Conical holes 356a, 407a... Conical member (movable control member) 40
8...Bush (movable control member)

Claims (2)

[Claims] 1. In a liquid pump in which the driving rotational speed varies and the pulsation frequency of the discharge pressure changes accordingly, a resonance chamber is provided to reduce the pulsation of the discharge pressure and communicates with a discharge passage of the liquid pump. a control hydraulic pressure generating means that generates a control hydraulic pressure having a value corresponding to a varying drive rotational speed or pulsation frequency; a movable control member that changes the resonance frequency of the resonance chamber; and hydraulic interlocking means for moving the movable control member by the control hydraulic pressure supplied from the control hydraulic pressure generating means so as to follow changes in the pulsation frequency of the liquid pump. Pulsation reduction mechanism. 2. Capacity control means that generates a control hydraulic pressure corresponding to the drive rotation speed in order to perform constant flow rate control as the drive rotation speed changes and the pulsation frequency of the discharge pressure changes accordingly; A variable displacement liquid pump having a displacement control piston that is moved by control hydraulic pressure supplied from a displacement control means to change the discharge capacity of the liquid pump, which is attached to reduce pulsations in the discharge pressure, a resonance chamber communicating with the discharge passage of the pump; and a resonance chamber mechanically or hydraulically interlocked with the displacement control piston so that the resonance frequency of the resonance chamber follows changes in the pulsation frequency of the discharge pressure. A discharge pressure pulsation reduction mechanism for a variable displacement liquid pump, comprising: a movable control member that changes the resonance frequency of the pump.