JPH04295193A - Pulsation eliminating device for hydraulic circuit - Google Patents

Abstract

PURPOSE:To effectively prevent pulsation of pressure oil generated in a main line by varying the length of an auxiliary line according to the intensity of a frequency detected by a frequency detecting means, in a device having an auxiliary line to prevent pulsation of a pump delivery pressure. CONSTITUTION:A pulsation removing device 8a is provided with a number of revolutions detector 12 to detect the number of revolutions of a hydraulic pump 2, a pressure detector 13 to detect the pressure of a main line 7, and a temperature detector 14 to detect a pressure oil temperature. First and second auxiliary lines 9a and 9b in which on-off valves 10 and 11, respectively, are located are connected to a main line 7. By controlling the on-off valves 10 and 11 by a control device 15 by means of output signals from the detectors 12-14, the length of the auxiliary line is varied and pulsation of pressure oil discharged with the aid of a hydraulic pump 2 is prevented from occurring. A length L1 of the first auxiliary line 9a is set to a value suitable for damping of pulsation in the maximum drive state of an actuator 5 and set to a value higher than lengths L2 and L1 of the second auxiliary line 9b.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit pulsation eliminating device for eliminating pressure oil pulsations occurring in a hydraulic circuit provided in a hydraulic machine such as a hydraulic excavator.

0002

2. Description of the Related Art FIG. 4 is a circuit diagram showing the basic configuration of a hydraulic circuit including a conventional pulsation removing device, and FIG. 5 is an enlarged view showing the essential parts of the pulsation removing device shown in FIG.

The hydraulic circuit shown in FIG. 4 includes a prime mover 1, a hydraulic pump 2 driven by the prime mover 1, a tank 3, an actuator 5 driven by pressure oil discharged from the hydraulic pump 2, and a hydraulic pump 2 driven by the hydraulic pump 2. Actuator 5
A directional control valve 4 that controls the flow of pressure oil supplied to the hydraulic circuit, a main pipeline 7 that connects the hydraulic pump 2 and the actuator 5, and a relief valve 6 that regulates the pressure of the pressure oil flowing through this hydraulic circuit. ing. A pulsation removing device 8 is provided in the discharge line of the hydraulic pump 2 to remove pulsation of the pressure oil. As shown in FIG. 5, this pulsation removing device 8 has a length L,
It consists of a cylindrical auxiliary conduit with an inner diameter of a.

In such a hydraulic circuit, the prime mover 1
When the hydraulic pump 2 is driven by
discharges the oil sucked in from the tank 3 into the main pipe 7, and this pressure oil is supplied to the actuator 5 through the directional control valve 4, and drives the actuator 5. At this time, the main pipe line 7 is likely to vibrate due to the pulsation of the pressure oil, but such vibrations may cause noise and reduce the reliability of the equipment that constitutes this hydraulic circuit. In order to cope with such a situation, the hydraulic circuit shown in FIG. 4 is provided with a pulsation removing device 8 that removes the pulsation of the pressure oil flowing through the main pipe 7. As shown in FIG. 5, this pulsation removing device 8 reflects and attenuates the pulsation generated in the main pipe 7, and the length L of the auxiliary pipe is L=(C/4Hz)-ka

It is given by (1). Here, L is the length of the pulsation remover 8, C is the sound speed in the pressure oil flowing through the main pipe 7, and Hz
is the frequency of the pulsation to be removed, k is the coefficient, and a is the inner diameter of the auxiliary pipe constituting the pulsation removal device 8 as described above. Such a pulsation removing device 8 is well known, for example, as disclosed in Japanese Patent Application Laid-open No. 5
It is described in the publication No. 6-83689.

[0005]

[Problems to be Solved by the Invention] However, the conventional pulsation removing device 8 described above is provided only one for one hydraulic circuit. The length L is uniquely set in consideration of the relevant frequency, Hz, etc. However, in actual operating conditions, the frequency Hz changes greatly depending on the operating conditions such as changes in the rotation speed of the prime mover 1, and the sound speed C changes slightly depending on the temperature and pressure of the pressure oil, so it is not always effective to eliminate pulsation. This causes problems such as noise generation and damage to equipment within the circuit.

The present invention has been made in view of the above-mentioned actual situation in the prior art, and its purpose is to effectively eliminate the pulsation of pressure oil that occurs in the main pipeline regardless of the operating state of the prime mover. The object of the present invention is to provide a pulsation removal device for a hydraulic circuit that can eliminate pulsations in a hydraulic circuit.

[0007]

[Means for Solving the Problems] In order to achieve this object, the present invention provides a prime mover, a hydraulic pump driven by the prime mover, an actuator driven by pressure oil discharged from the hydraulic pump, and a hydraulic pump. A pulsation removal device for a hydraulic circuit, which is installed in a hydraulic circuit and has an auxiliary pipe line for removing pulsations in pressure oil discharged from a hydraulic pump, which is installed in a hydraulic circuit and has a main pipe line communicating with an actuator, and detects the frequency of the pulsation. The apparatus is configured to include a frequency detecting means for detecting a frequency, and a conduit length changing means capable of changing the length of the auxiliary conduit in accordance with at least the magnitude of the frequency detected by the frequency detecting means.

[0008]

[Operation] Since the present invention has the above-mentioned structure, when the frequency of pulsation changes particularly in response to a change in the operating condition of the prime mover, the changed frequency is detected by the frequency detection means, and the frequency detection means The conduit length changing means is activated in accordance with the magnitude of the frequency detected at , and the length of the auxiliary conduit for attenuating pulsation is changed to a length effective for attenuation. Therefore, regardless of the operating condition of the prime mover,
It is possible to satisfactorily attenuate the pulsation of the pressure oil flowing through the main pipe.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the pulsation removing device for a hydraulic circuit according to the present invention will be described below with reference to the drawings. 1 is a circuit diagram showing a hydraulic circuit including a first embodiment of the present invention, and FIG. 2 is a circuit diagram showing a hydraulic circuit including a first embodiment of the present invention.
It is a control flow diagram which shows the processing procedure in the control device with which the Example is equipped. Note that the hydraulic circuit shown in FIG. 1 and FIG. 3 including the second embodiment described later is installed in, for example, a hydraulic excavator, and parts in FIGS. 1 and 3 that are equivalent to FIG. 4 described above are the same. It is indicated by a symbol.

Even in the hydraulic circuit shown in FIG. 1 including the first embodiment, a prime mover 1 similar to that in the hydraulic circuit shown in FIG. 4 described above, a hydraulic pump 2 driven by this prime mover 1, A tank 3, an actuator 5 driven by pressure oil discharged from the hydraulic pump 2, a directional control valve 4 that controls the flow of pressure oil from the hydraulic pump 2 to the actuator 5, and a directional control valve 4 that controls the flow of pressure oil from the hydraulic pump 2 to the actuator 5. It is equipped with a main conduit 7 for guiding the circuit, and a relief valve 6 for regulating the magnitude of the pressure within the circuit.

A first embodiment of the hydraulic circuit, that is, a pulsation removing device 8a, is configured to reduce the number of revolutions N of the hydraulic pump 2.
, a pressure detector 13 that detects the pressure P of the main pipe 7 , a temperature detector 14 that detects the temperature T of the pressure oil flowing through the circuit, and a first The auxiliary pipe 9a, the second auxiliary pipe 9b which is longer than the first auxiliary pipe 9a, the on-off valve 10 provided in the first auxiliary pipe 9a, and the second auxiliary pipe 9b. An on-off valve 11 provided,
It has arithmetic functions including memory and logical judgment, and a rotation speed detector 1
2. The control device 15 processes signals output from the pressure detector 13 and the temperature detector 14 and outputs drive signals to the on-off valves 10 and 11.

The first auxiliary conduit 9a described above damps pulsations that may occur empirically, for example, in a driving state where the prime mover 1 is driven at the rated rotation speed and the actuator 5 requires maximum operating speed and force. has a length L1 suitable for
As described above, the second auxiliary pipe 9b is longer than the first auxiliary pipe 9a, and for example, the rotation speed of the prime mover 1 is slightly lower than the rated rotation speed, and the operating speed and force of the actuator 5 are suppressed. It has a length L2 suitable for attenuating pulsations that may occur empirically in the driving state. Also,
The control device 15 described above determines the pulsation frequency Hz based on the rotation speed N of the hydraulic pump 2 output from the rotation speed detector 12.
a first calculation unit 15a that calculates the sound velocity C in the pressure oil based on the pressure P and temperature T output from the pressure detector 13 and the temperature sensor 14;
The length Lx of the auxiliary conduit suitable for attenuating pulsation in the current driving state is calculated based on the frequency Hz and the sound speed C calculated by the calculation unit 15a and the second calculation unit 15b, and this length is Compare Lx with the length L1 of the first auxiliary conduit 9a and the length L2 of the second auxiliary conduit 9b stored in advance, and determine the length L.
1. A third calculation unit 15c that sets the length L2 that is closer to the length Lx as the length LR.

Note that the rotation speed detector 12 and the first calculation section 15a of the control device 15 constitute a frequency detection means for detecting the frequency of pulsation of the pressure oil discharged from the hydraulic pump 2. . In addition, the pressure detector 13 described above,
The temperature detector 14 and the second calculation section 15b of the control device 15 constitute a sound speed detection means for detecting the sound speed C in the pressure oil discharged from the hydraulic pump 2. Furthermore, the first
auxiliary conduit 9a, second auxiliary conduit 9b, on-off valves 10, 1
1 and the third calculation unit 15c of the control device 15 attenuates the pulsation according to the magnitude of the frequency Hz detected by the frequency detection means and the magnitude of the sound speed C detected by the sound velocity detection means. It constitutes a pipe length changing means that can change the length of the auxiliary pipe to a length suitable for attenuating pulsation.

In the embodiment configured as described above, when the prime mover 1 is operated to drive the hydraulic pump 2, the rotational speed detector 12, the pressure detector 13, and the temperature detector 14 each output an output signal. The rotational speed N of the hydraulic pump 2 , the pressure P of the main pipe 7 , and the temperature T of the pressure oil flowing through the main pipe 7 are input to the control device 15 . At this time, as shown in FIG. 5, the first calculation unit 15a of the control device 15 calculates the frequency
The following calculation is performed to determine z. Hz=M・N・d [
M: Number of pistons (or number of gear teeth), N:

rotation speed, d: order]
(2) Further, the second calculation section 15b of the control device 15 performs the following calculation to determine the sound speed C in the pressure oil. K=κP [K: bulk modulus of pressure oil, κ: specific heat ratio, P: pressure] (3) Here, the specific heat ratio κ is unique to the pressure oil discharged from the hydraulic pump 2. Cx=(K/ρ) to the (1/2) power
[Cx: Target sound speed, K
: Bulk modulus of pressure oil, ρ: Density of pressure oil] (4)
C=Cx+f(T)

[C: Sound velocity, Cx: Target sound velocity, f(T): Corrected sound velocity which is a function of temperature] (5) Then, control is performed based on the frequency Hz and sound velocity C determined by the above equations (2) and (5). In the third calculation unit 15c of the device 15,
The following calculation is performed to obtain the target length Lx. Lx=(C/4Hz)-ka
[k and a are the same as in equation (1) above]
(6)
Furthermore, in this third calculation unit 15c, the length L1 of the first auxiliary pipe 9a, which is stored in advance, and the length L1 of the second auxiliary pipe 9a are calculated.
Compare the length L2 of b and Lx obtained by the above formula (6),
The value closer to the value of Lx is set as LR. Then, a drive signal corresponding to LR is output to the corresponding on-off valve 10 or 11 of either the first auxiliary pipe 9a or the second auxiliary pipe 9b, which has a length close to the length of Lx.

In this case, if the driving state of this hydraulic circuit is such that the prime mover 1 is driven at the rated rotation speed and requires the maximum operating speed and force of the actuator 5, then
Since the target length Lx in equation (6) is approximately L1 from the magnitude of the frequency Hz of the pulsation of the pressure oil, this L1 is set to LR, and the on-off valve 10 provided in the first auxiliary pipe 9a
A drive signal is output to. As a result, the first auxiliary pipe 9a is opened, and the pulsation of pressure oil generated in the main pipe 7 is reduced to the first auxiliary pipe 9a.
is guided into the first auxiliary pipe 9a and attenuated within this first auxiliary pipe 9a. In addition, from such a driving state, the prime mover 1
When the rotation speed of the actuator 5 is slightly lowered and the operating speed and force of the actuator 5 are slightly suppressed, the frequency Hz of the pressure oil pulsation also changes, and the target length Lx in equation (6) becomes approximately L2. This L2 is set to LR, and a drive signal is output to the on-off valve 11 provided in the second auxiliary pipe 9b. As a result, this second auxiliary conduit 9b is opened,
The pulsations of the pressure oil generated in the main line 7 are guided into the second auxiliary line 9b and are attenuated within the second auxiliary line 9b.

In the first embodiment configured in this manner, as described above, the pulsation of the pressure oil is attenuated in response to a change in the frequency of the pulsation of the pressure oil, particularly in response to a change in the rotational speed of the prime mover 1. A suitable auxiliary line is automatically selected for the prime mover 1.
The pulsation of the pressure oil generated in the main pipe line 7 can be effectively eliminated regardless of the operating state of the main pipe line 7.

FIG. 3 is a circuit diagram showing a hydraulic circuit including a second embodiment of the present invention. In the second embodiment shown in FIG. 3, the pulsation removing device 8b includes a rotation speed detector 12 that detects the rotation speed N of the hydraulic pump 2, and A hydraulic cylinder 20 that is equipped with a control device 15 that calculates the length of the auxiliary conduit and is connected to the main conduit 7 to form the auxiliary conduit, and a drive body that operates in response to a drive signal output from the control device 15. 21 and
The structure includes a link 22 that rigidly connects the rod 20a of the hydraulic cylinder 20 and the rod 21a of the drive body 21. Note that the control device 15 has a configuration in which the second calculation section 15b is removed from the configuration shown in FIG. The speed of sound C when the pressure oil is at a predetermined pressure and a predetermined temperature is stored in advance in the third calculation unit 15c as a constant. In this second embodiment, the above-mentioned rotation speed detector 12 and the first calculation section 15a included in the control device 15 constitute a frequency detection means for detecting the frequency Hz. Third calculation unit 1 included
5c, hydraulic cylinder 20, drive body 21, and link 2
2 constitutes a pipe length changing means for changing the length of the auxiliary pipe according to the magnitude of the frequency Hz.

In the second embodiment configured as described above, the rotation speed N of the hydraulic pump 2 is detected by the rotation speed detector 12, and the first In the arithmetic unit 15a, the frequency Hz is calculated by the above equation (2), and the calculated frequency Hz
Based on this, the third calculation unit 15c of the control device 15 calculates the target length Lx from the above equation (6), sets the target length Lx to LR, and sends a drive signal corresponding to the LR to the driving body. 21. Accordingly, the driver 21
The rod 21a of the hydraulic cylinder 20 expands and contracts, and the rod 20a of the hydraulic cylinder 20 integrally expands and contracts via the link 22, so that the length of the internal space of the cylinder section of the hydraulic cylinder 20, that is, the length of the auxiliary pipe, is adjusted to the above-mentioned frequency Hz. The length is automatically changed to a length suitable for attenuating pulsation depending on the size of the pulsation.

Even in the second embodiment configured as described above, the pulsation of the pressure oil occurring in the main pipe line 7 can be suppressed regardless of the operating state of the prime mover 1, as in the first embodiment described above. Can be removed well.

[0020] In the above-mentioned first embodiment,
A pressure detector 13 and a temperature detector 14 are provided, and the sound velocity C in the pressure oil is determined from the pressure P and temperature T output from these detectors 13 and 14, but the present invention is not limited to this. However, a transmitter may be provided at a predetermined position in the main conduit 7, a receiver may be provided at a predetermined position in the main conduit 7 at a distance Ls from the transmitter, and these receivers and transmitters may be connected to the control device 15. Then, the second calculation unit 15b of the control device 15 counts the time t required from when the transmitter emits the sound until the receiver receives the sound, and from this time t and the above-mentioned distance Ls,
The speed of sound C in the pressure oil may be detected by calculating C=L/t.

Furthermore, in the first embodiment, the speed of sound C in the pressure oil is detected and the target length Lx is calculated according to this speed of sound C and the frequency Hz. Since the effect of changes in sound speed C on attenuation is relatively small,
For example, the sound speed in pressure oil, which is normally considered when the prime mover 1 is driven at the rated rotation speed, is set as a constant for calculation of equation (6), that is, only the frequency Hz is detected, and the target is determined based on this frequency Hz. The length Lx may also be calculated.

Further, in the first embodiment, two auxiliary pipes are provided, but the present invention is not limited to this, and three or more auxiliary pipes may be provided.

[0023]

[Effects of the Invention] Since the hydraulic circuit pulsation removing device of the present invention is configured as described above, the pulsation of pressure oil generated in the main pipe can be effectively removed regardless of the operating state of the prime mover. In other words, it is possible to prevent the vibration of the hydraulic circuit due to the occurrence of pulsation regardless of the operating state of the prime mover, and it is possible to suppress noise and prevent damage to equipment in the circuit compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a hydraulic circuit including a first embodiment of a pulsation removing device for a hydraulic circuit according to the present invention.

FIG. 2 is a control flow diagram showing a processing procedure in a control device included in the first embodiment shown in FIG. 1;

FIG. 3 is a circuit diagram showing a hydraulic circuit including a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing the basic configuration of a hydraulic circuit including a conventional pulsation removing device.

FIG. 5 is an enlarged view of a main part of the pulsation removing device shown in FIG. 4;

[Explanation of symbols]

1 Prime mover 2 Hydraulic pump 3 Tank 4 Directional control valve 5 Actuator 7 Main pipeline 8a, 8b Pulsation removal device 9a, 9b Auxiliary pipe line 10, 11 Open/close valve 12 Rotation speed detector 13 Pressure detector 14 Temperature detector 20 Hydraulic cylinder 21 Driving body 22 Link

Claims (4)

[Claims] Claim 1: A hydraulic circuit comprising a prime mover, a hydraulic pump driven by the prime mover, an actuator driven by pressure oil discharged from the hydraulic pump, and a main pipe connecting the hydraulic pump and the actuator. A pulsation removal device for a hydraulic circuit having an auxiliary pipe line for removing pulsation of pressure oil discharged from a hydraulic pump, comprising a frequency detection means for detecting the frequency of the pulsation, and at least a frequency detected by the frequency detection means. A pulsation removal device for a hydraulic circuit, characterized in that a pulsation removing device for a hydraulic circuit is provided, comprising a pipe length changing means capable of changing the length of the auxiliary pipe line according to the size of the auxiliary pipe line. 2. A sound velocity detection means for detecting the sound velocity in the pressure oil discharged from the hydraulic pump is provided, and the pipe length changing means comprises:
Claim 1 characterized in that the pipe length changing means is capable of changing the length of the auxiliary pipe according to the magnitude of both the frequency detected by the frequency detection means and the sound speed detected by the sound speed detection means. The described hydraulic circuit pulsation removal device. 3. Claim 1 or 2, wherein the pipe length changing means has a plurality of auxiliary pipes having different lengths.
The described hydraulic circuit pulsation removal device. 4. The pulsation eliminating device for a hydraulic circuit according to claim 1, wherein the pipe length changing means has a cylinder forming an auxiliary pipe.