JPH0960785A - Pressure oil pulsation reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the pulsation of pressure oil even when the revolving speed of a hydraulic pump is changed under any operating conditions by adjusting the shift position of a reflector based on the data calculated by a pump revolving speed calculating means, and adjusting the effective length of the passage of a side branch. SOLUTION: A motor 8 drives a pinion rack mechanism constituted of a gear 12 and teeth 11 while its revolving speed is controlled by a motor control device 7 based on the data from an engine revolving speed monitor device 6. A magnet fitting member 9 is slid in the guide groove of a guide member 10, and a magnet 13 is moved to the prescribed position in response to the rotation quantity of the motor 8 along the outer wall face of a side branch 5. Since the magnet 13 attracts and holds a steel reflector 14 via the magnetic force transmitting the wall of the ceramic side branch 5, the reflector 14 is smoothly slid in the passage 5a of the side branch 5 while pressure oil flows through a fine hole 15, and the shift position is adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure oil pulsation reducing device for reducing pulsation of pressure oil generated by a hydraulic pump and propagating in a flow path of pressure oil at a side branch, and more particularly to a hydraulic excavator and a hydraulic excavator. It is useful for hydraulic work machines for construction work such as cranes.

[0002]

2. Description of the Related Art In a hydraulic drive circuit composed of a hydraulic pump, a hydraulic actuator, etc., the hydraulic pump causes pressure fluctuations in the pressure oil to be discharged in the course of repeated discharge and suction of the oil. Pulsation of pressure oil occurs in the flow path. The pulsation of the pressure oil is transmitted to various hydraulic devices connected to the pressure oil pipe through the pipe and causes noise, and in some cases causes resonance and damages the pipe and the hydraulic device. Therefore, it is necessary to reduce it as much as possible. Conventionally, a side-branch type pressure oil pulsation reducing device having a structure as shown in FIG. 3 has been generally used as one means for reducing such pressure oil pulsation. Therefore, the basic technical contents of such a conventional general side branch type pressure oil pulsation reducing device will be described with reference to FIGS. 3 and 4. FIG. 3 is a sectional view of a conventional general side-branch type pressure oil pulsation reducing device, and FIG. 4 is a view for explaining a pulsation reducing effect of a conventional general side-branch type pressure oil pulsation reducing device. It is a characteristic diagram.

In FIG. 3, 3 is a hydraulic pump such as an oblique shaft type plunger pump or a swash plate type plunger pump which is a source of hydraulic pressure, 4 is connected to the discharge side of the hydraulic pump 3, and the pressure oil is hydraulically driven by a hydraulic drive circuit. Of the main pipe that constitutes the main flow path for guiding to each place of the tank, 16 is a tank from which the pressure oil supplied to each place via the main pipe 4 is discharged, and 17 is branched and connected to the main pipe 4. It is a bottomed branch-shaped side branch that functions to reduce the pulsation of the pressure oil in the pipe 4.
The pressure oil of the hydraulic pump 3 supplied to the main pipe 4 is guided to various hydraulic devices such as actuators through the branch flow passages, but in the figure, such hydraulic flow passages and hydraulic devices such as actuators are not shown. On the side branch 17,
A passage 17b is formed, and the end on the side opposite to the branch point is closed so that the pulsation of the pressure oil in the main pipe 4 entering the passage 17b from the branch point with the main pipe 4 is reflected and returned. To form the reflection surface 17a.

In the conventional side-branch type pressure oil pulsation reducer, the main pipe 4 is provided with the side branch 17 having such a structure as a branch.
The pulsation of the pressure oil discharged from the main pipe 4 is propagated to the passage 17b in the side branch 17, and the pulsation of the pressure oil propagated to the passage 17b is reflected on the reflection surface 17
It is reflected at a and returns to the main pipe 4 again through the passage 17b. Therefore, a pulsating wave having a specific frequency to be reduced is predetermined and the side branch 17 is
If the length of the passage 17b is adjusted appropriately, the pulsating wave of the pressure oil that travels back and forth through the side branch 17 and returns to the main pipe 4 collides with the pulsating wave of the main pipe 4 and the peaks and troughs of the wave. Since they can be interfered in such a relationship, the pulsation of the specific frequency among the pulsations of the pressure oil propagating in the main pipe 4 can be intensively reduced. The pulsation of the pressure oil discharged from the hydraulic pump 3 is composed of a fundamental frequency and a harmonic having a frequency that is an integral multiple of the fundamental frequency. The fundamental frequency f at the pulsation-reducing center frequency reduced by the side branch 17 is When the sound velocity of the pressure oil is V and the length of the passage 17b of the side branch 17 is L, it can be obtained by the following equation (1).

F = V / 4L (1) In the equation (1), the pipe diameter of the main pipe 4 can be ignored compared to the length L of the passage 17a of the side branch 17. I think it is very small. The pulsation reduction center frequency is
Side branch 1 among the pulsations of hydraulic pressure of various frequency components
It is the frequency of the pulsation that is most greatly reduced by interfering with the pulsation of the hydraulic pressure reflected and returned at 7. The pulsation reducing effect exhibited by the conventional pressure oil pulsation reducing device of FIG. 3, that is, the transmission loss is shown in a diagram in FIG. In the diagram of FIG. 4, the pulsation of the frequency at the apex point is the side branch 17
It is the pulsation that is most greatly reduced by interfering with the pulsation of the pressure oil reflected and returned, and is the pulsation corresponding to the pulsation reduction center frequency. The pulsation of the pressure oil reflected and returned by the side branch 17 not only interferes with the pulsation of the pressure oil having the pulsation reducing center frequency but also interferes with the pulsation of the pressure oil having the frequency in the peripheral region to reduce the pulsation to some extent. Therefore, Fig. 4
The diagram will draw a symmetrical curve like a mountain. Therefore, by using such a side branch 17, not only the pulsation of the pressure oil having the pulsation reduction center frequency but also the pulsation of the pressure oil having the frequency in the peripheral region of the pulsation reduction center frequency can be reduced to some extent. With respect to the pulsation of the pressure oil deviated from the frequency, the pulsation reduction effect suddenly deteriorates.

On the other hand, the pulsation of the pressure oil generated by the hydraulic pump 3 varies depending on the rotational speed of the hydraulic pump 3 such that the pulsation of the hydraulic oil increases as the rotational speed of the hydraulic pump 3 increases. However, the pulsation reduction center frequency depends on the length of the passage 17b of the side branch 17 and is uniquely determined by the length thereof, as is clear from the equation (1), and therefore is shown in FIG. The conventional general pressure oil pulsation reduction device is effective only when the rotation speed of the hydraulic pump does not change, and is used for a machine in which the rotation speed of the hydraulic pump changes such as a hydraulic working machine such as a hydraulic excavator. If it does not work effectively. Conventionally, in order to solve such a problem, a plurality of types of pressure oil pulsation reducing devices have been proposed in Japanese Utility Model Laid-Open No. 3-30583. One of the devices is that "a side branch provided in the main pipe is provided with one or more opening / closing valves, and the opening / closing valves are opened / closed so that the length of the passage of the side branch can be adjusted in multiple stages. It is something. In addition, the other device "provides a piston that balances the discharge pressure of the hydraulic pump and the spring force in the side branch provided in the main pipe, and the pulsating wave of the pressure oil in the main pipe passage is reflected by this piston. I did. "

[0007]

However, the conventional pressure oil pulsation reducing device proposed in Japanese Utility Model Laid-Open No. 3-30583 has a problem to be improved.
That is, in the former device in which an opening / closing valve is attached to the side branch, the effective length of the passage of the side branch is adjusted in several steps according to the number of opening / closing valves. However, it is impossible to effectively reduce the pulsation of the pressure oil in such a state that the pulsation reduction effect is always the best because there is a limit due to practical constraints such as manufacturing cost. In the latter device, which is equipped with a piston in the side branch, the hydraulic pressure caused by load fluctuations is used under operating conditions in which the engine operates without changing the target engine speed, as in the case of always operating at the rated engine speed. This is effective when the actual rotational speed of the hydraulic pump changes due to changes in the pump torque.However, as with hydraulic work machines for construction work such as hydraulic excavators, the operator can set the target rotational speed of the engine according to the working conditions. It cannot be said to be effective when the rotational speed of the hydraulic pump changes under the operating condition in which the operation is performed while largely changing itself.

The present invention is intended to solve such problems found in the prior art, and its object is to make the pulsation of pressure oil effective regardless of the operating conditions of the rotational speed of the hydraulic pump. It is to provide a side-branch type pressure oil pulsation reducing device that can be effectively reduced.

[0009]

The object of the present invention is to reduce the pulsation of pressure oil that is generated in a hydraulic pump and propagates in the pressure oil passage by means of a side branch provided in the pressure oil passage. In the pressure oil pulsation reducing device, a reflecting plate is slidably provided in the passage of the side branch, and a reflecting plate moving mechanism capable of sliding and moving the reflecting plate in the passage of the side branch, and a hydraulic pump A pump rotation speed calculation means capable of calculating data regarding the rotation speed is provided, and the operation of the reflection plate moving mechanism is controlled based on the data calculated by the pump rotation speed calculation means to adjust the movement position of the reflection plate. By doing so, the effective length of the passage of the side branch can be adjusted so as to reduce the pulsation of the pressure oil of a predetermined frequency generated in the pressure oil flow passage in accordance with the rotational speed of the hydraulic pump. It is accomplished by a hydraulic fluid pulsation reducing device as described in claim 1., wherein.

[0010]

Since the present invention has such a structure,
When the hydraulic pump is driven to rotate, the pulsation of pressure oil with a predetermined frequency according to the number of rotations propagates in the flow path of pressure oil and also in the side branch. The data regarding the rotational speed of the pump is calculated by the pump rotational speed calculation means. Then, the reflector moving mechanism adjusts the moving position of the reflector by sliding the reflector in the passage of the side branch while controlling the operation based on the calculated data, and as a result, the hydraulic pump moves. The effective length of the passage of the side branch is adjusted so as to reduce the pulsation of the pressure oil having a predetermined frequency generated in the pressure oil flow passage in accordance with the rotation speed. In this way, the effective length of the passage of the side branch is adjusted, so that the pulsation of the pressure oil propagating in the side branch is reflected by the reflecting surface of the reflection plate and is effective as the pulsation of the pressure oil in the passage of the pressure oil. It is possible to reduce the pulsation of the pressure oil having a predetermined frequency in the flow path of the pressure oil depending on the rotation speed of the hydraulic pump.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a pressure oil pulsation reducing device according to an embodiment of the present invention, and FIG. 2 is an A- of the pressure oil pulsation reducing device of FIG.
FIG. 3 is a sectional view taken along line A. 1 and 2, the parts denoted by the same reference numerals as those in FIG. 3 represent the same parts as those in FIG. As is apparent from FIG. 1, the pressure oil pulsation reducing device of the embodiment of the present invention is similar to the conventional general pressure oil pulsation reducing device shown in FIG. The pulsation of the pressure oil propagating inside, especially the pulsation of the pressure oil propagating in the main pipe 4 connected to the discharge side of the hydraulic pump 3, is reduced by the side branch provided in the main pipe 4. However, the basic structure is the same as that of the device shown in FIG. 3 and the conventional device proposed in Japanese Utility Model Laid-Open No. 3-30583.

Therefore, the characteristic technical contents of the pressure oil pulsation reducing device of the present embodiment will be described below with reference to FIGS. 1 and 2. 1 and 2, 1 is an engine as a prime mover for driving the hydraulic pump 3, and 2 is a coupling for connecting an output shaft of the engine 1 to an input shaft of the hydraulic pump 3.
Is a ceramic side branch branched and connected to the main pipe 4 according to the present embodiment, 6 is an engine speed monitor device for calculating the speed of the hydraulic pump 3 by monitoring the speed of the engine 1, and 7 is this engine. This is a motor control device to which data regarding the rotation speed calculated by the rotation speed monitor device 6 is input. The engine speed monitor device 6 is, in essence, a means for calculating data relating to the speed of the hydraulic pump 3. Therefore, instead of the engine speed monitor device 6, the speed of the hydraulic pump 3 is directly measured to measure the speed. A means for calculating data regarding the number of rotations may be provided.
Since the frequency of the pulsation of the pressure oil generated by the hydraulic pump 3 is determined by the rotational speed of the hydraulic pump 3 as described above, the hydraulic pump 3 is calculated by such pump rotational speed calculation means.
By calculating the data relating to the number of rotations, it is possible to detect the frequency of the pulsation of the hydraulic pressure to be reduced that occurs in the flow path of the main pipe 4 isobaric oil. The motor controller 7 controls the operation of the reflector moving mechanism described in detail below to adjust the moving position of the reflector 14 based on the data from the engine speed monitor 6 to adjust the side branch 5 The effective length of the passage 5a is adjusted to reduce the pulsation of the pressure oil of a predetermined frequency generated in the main pipe 4 according to the rotation speed of the hydraulic pump 3.

The reflecting plate moving mechanism will be described below.
Is an electric motor controlled by the electric motor control device 7, 9 is a vertically long magnet mounting member for mounting a magnet 13, which will be described later, 10 is a guide member for guiding the magnet mounting member 9, and 11 is a rack-shaped member provided on the magnet mounting member 9. Tooth, 12 is a gear provided on the output shaft of the electric motor 8 and meshes with a rack-shaped tooth 11 to act as a pinion, 13 is a magnet attached to the magnet attaching member 9, 14 is a side branch 5 having a reflecting surface 14a. An iron reflector slidably fitted in the passage 5a of
Reference numeral 5 is a pore formed in the center of the reflection plate 14 through which pressure oil can flow. The magnet mounting member 9 includes the teeth 11 and the magnet 1.
3a, a guided piece 9b guided by the guide member 10, and a connecting piece 9c for connecting these.
And has a substantially H-shaped cross section. Guide member 10
Has a guide groove 10a into which the guided piece 9b of the magnet mounting member 9 is slidably fitted and which moves the magnet 13 along the outer wall surface of the side branch 5. The magnet 13 attached to the magnet attachment member 9 is arranged at a position facing the reflection plate 14 through the wall of the side branch 5, and the magnetic reflection force transmitted through the wall of the side branch 5 made of ceramic causes the reflection plate 14 made of iron to move. It is designed to be held by adsorption. Therefore, by moving the magnet 13, the reflecting plate 14
The side branch 5 can be moved in the longitudinal direction to adjust its moving position. As described above, in this embodiment, the reflector moving mechanism includes the electric motor 8 and the gear 1 provided on the output shaft.
2 and a rack-shaped tooth 11 and a magnet mounting member 9 provided with a magnet 13 and a guide member 10 for guiding the magnet mounting member. By moving the magnet 13 of the mounting member 9, the iron reflection plate 14 can be moved to an appropriate position of the side branch 5.

The pressure oil pulsation reducing device of this embodiment has such a structure. Therefore, when the engine 1 is driven, the hydraulic pump 3 is rotationally driven through the coupling 2, and the predetermined frequency corresponding to the rotational speed thereof. Pulsation of pressure oil in the main piping 4
Of the side branch 5 and the passage 5a of the side branch 5, and the hydraulic pump 3 for detecting the frequency.
The data relating to the number of revolutions is obtained by monitoring the number of revolutions of the engine 1 by the engine revolution number monitor device 6 and input to the electric motor control device 7. Then, the electric motor 8 drives the pinion rack mechanism including the gears 12 and the teeth 11 while the rotation amount is controlled by the electric motor control device 7 based on the data from the engine speed monitor device 6, so that the magnet mounting is performed. The member 9 slides in the guide groove 10a of the guide member 10 to move the magnet 13 along the outer wall surface of the side branch 5 to a predetermined position according to the rotation amount of the electric motor 8. Since this magnet 13 attracts and holds the iron reflection plate 14 by the magnetic force passing through the wall of the ceramic side branch 5, the reflection plate 14 is pressed by the pores 15 as the magnet 13 moves. While moving the oil, it smoothly slides in the passage 5a of the side branch 5 to adjust the moving position. As a result, the effective length of the passage 5a of the side branch 5 is adjusted so as to reduce the pulsation of the pressure oil of the predetermined frequency generated in the main pipe 4 according to the rotation speed of the hydraulic pump 3. In other words, the reflection surface 1 of the reflection plate 14 in which the pulsation of the pressure oil propagated in the side branch 5 is adjusted in position.
It reflects on 4a and interferes effectively with the pulsation of the pressure oil in the main piping 4, and reduces the pulsation of the pressure oil of the predetermined frequency which arises in the main piping 4 according to the rotation speed of the hydraulic pump 3.

As described above, in this embodiment, based on the data relating to the rotational speed of the hydraulic pump 3 calculated by the engine rotational speed monitor device 6, the amount of rotation of the electric motor 8 is controlled so that the moving position of the reflection plate 14 is controlled. The passage 5a of the side branch 5 is adjusted so as to reduce the pulsation of the pressure oil having a predetermined frequency generated in the main pipe 4 according to the rotation speed of the hydraulic pump 3.
Since the effective length of the engine 1 can be adjusted, not only when the rotational speed of the hydraulic pump 3 changes under the condition that the target rotational speed of the engine 1 is constant, but also when the target rotational speed of the engine 1 is significantly changed. The pulsation of the pressure oil can be effectively reduced even when the number of rotations of the hydraulic pump 3 changes under the operating conditions for the operation. Therefore, according to the present embodiment, the side-branch type pressure oil pulsation reducing device capable of effectively reducing the pressure oil pulsation regardless of the operating conditions of the rotation speed of the hydraulic pump. Is obtained. Further, the reflector moving mechanism uses the magnet 13 that moves along the outer wall surface of the side branch 5 to move the magnet 13 so that the iron reflector 14 inside the side branch 5 is moved while being attracted. Since it is configured to adjust the position,
There is no need to perform special processing on the side branch 5 and it is not necessary to provide a sealing means for preventing oil leakage. A prime mover such as the engine 1 is usually provided with a means for detecting the prime mover speed in order to drive the prime mover at a predetermined target speed such as the rated speed. Since the engine rotation speed monitor device 6 that calculates the rotation speed of the hydraulic pump 3 by monitoring the rotation speed of the engine 1 is used as the calculation means, the existing means for detecting the rotation speed of the prime mover can be effectively utilized. .

In the present embodiment, the reflector moving mechanism includes a motor 8, a gear 12 provided on the output shaft, a magnet mounting member 9 provided with rack-shaped teeth 11 and a magnet 13, and a guide member 10 for guiding the magnet mounting member 9. It is composed of, but the point is that the reflector 14
Since it is only necessary to move the side branch 5 to a desired position, a screw feeding mechanism may be used in place of the pinion rack mechanism composed of the gear 12 and the teeth 11, and even a seal is suitable. Then, the reflecting plate 14 may be directly moved by using a piston rod or the like. In the present embodiment, the side branch 5 is made of ceramic, but it may be made of other material as long as it is a non-magnetic material having a property of transmitting magnetic force.
Is not limited to iron, but may be made of other ferromagnetic material. In this embodiment, the engine rotation speed monitor device 6 that calculates the rotation speed of the hydraulic pump 3 by monitoring the rotation speed of the engine 1 that drives the hydraulic pump 3 is used as the pump rotation speed calculation means.
The pump rotation speed calculation means may be any means that can appropriately calculate data regarding the rotation speed of the hydraulic pump 3 regardless of the operating conditions of the hydraulic pump 3. Instead of the rotation speed monitor device 6, other means such as a means for directly measuring the rotation speed of the hydraulic pump 3 and calculating data on the rotation speed can be used.

[0017]

As is apparent from the above description, the present invention relates to a side-branch type pressure oil pulsation reducing device, in particular, "providing a reflecting plate slidably in the passage of the side-branch and A reflecting plate moving mechanism capable of sliding and moving the reflecting plate in the passage, and a pump rotation speed calculating means capable of calculating data regarding the rotation speed of the hydraulic pump are provided. By controlling the operation of the reflection plate moving mechanism based on the calculated data and adjusting the movement position of the reflection plate, the pressure oil of a predetermined frequency generated in the flow path of the pressure oil according to the rotation speed of the hydraulic pump The effective length of the side-branch passage can be adjusted to reduce pulsation. "Therefore, the pulsation of pressure oil is effective regardless of the operating conditions of the hydraulic pump. It is possible to provide a pressurized fluid pulsation reducing device side branch type that can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pressure oil pulsation reducing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of the pressure oil pulsation reducing device of FIG.

FIG. 3 is a sectional view of a conventional general side-branch type pressure oil pulsation reducing device.

FIG. 4 is a characteristic diagram for explaining a pulsation reducing effect of a conventional general side-branch type pressure oil pulsation reducing device.

[Explanation of symbols]

 1 Engine 2 Coupling 3 Hydraulic Pump 4 Main Pipe 5 Side Branch 5a Side Branch Passage 6 Engine Speed Monitoring Device 7 Motor Control Device 8 Electric Motor 9 Magnet Mounting Member 10 Guide Member 11 Teeth 12 Gear 13 Magnet 14 Reflector 14a Reflector Reflective surface 15 Pore

Claims (3)

[Claims] 1. A side branch passage in a pressure oil pulsation reducing device for reducing a pulsation of pressure oil generated in a hydraulic pump and propagating in the pressure oil flow path by a side branch provided in the pressure oil flow path. A reflector is slidably mounted on the
A reflecting plate moving mechanism capable of sliding and moving the reflecting plate in the passage of the side branch, and a pump rotation speed calculating means capable of calculating data on the rotation speed of the hydraulic pump are provided. By controlling the operation of the reflecting plate moving mechanism based on the data calculated by the calculating means to adjust the moving position of the reflecting plate, A pressure oil pulsation reducing device characterized in that the effective length of a passage of a side branch can be adjusted so as to reduce pressure oil pulsation. 2. The reflecting plate moving mechanism has a magnet that moves along the outer wall surface of the side branch, and the reflecting plate is a ferromagnetic body, and the side branch is a non-magnetic body that transmits magnetic force. The pressure oil pulsation reducing device according to claim 1. 3. The engine rotation speed monitor device for calculating the rotation speed of the hydraulic pump by monitoring the rotation speed of a prime mover driving the hydraulic pump, wherein the pump rotation speed calculating means is a prime mover rotation speed monitor device. Item 2. A pressure oil pulsation reducer according to item 2.