JP2014169763A - Pulsation suppression mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulsation suppression mechanism which can simply adjust actuation resistance of a cylinder and, moreover, can suppress the occurrence of vibrations.SOLUTION: A mechanism suppresses vibrations in equipment which includes: a hydraulic cylinder 2 provided with a piston lateral chamber 2s having a variable volumetric capacity into which hydraulic oil is enclosed, and an inertia fluid chamber 2i; a high-pressure side switch 3H which performs communication and cutoff between the inertia fluid chamber 2i and a high-pressure source HP; a low-pressure side switch 3L which performs communication and cutoff between the inertia fluid chamber 2i and a low-pressure source LP; and a control part 5 which controls actuation of the low-pressure side switch 3L and the high-pressure side switch 3H. Therein, a substantially pipe-shaped side branch 11 communicated with the inertia fluid chamber 2i is provided, and the control part 5 controls actuation of the low-pressure side switch 3 L and the high-pressure side switch 3H such that a switching frequency H which alternately communicates the low-pressure side switch 3L and the high-pressure side switch 3H with the inertia fluid chamber 2i satisfies L=V/4H when the length of the side branch 11 is L and sound speed of hydraulic oil is V.

Description

  The present invention relates to a pulsation suppression mechanism.

  In a construction machine or the like, when a boom or an excavator is swiveled or a machine body is swung, a very large force is required, and therefore hydraulic pressure is used as the power. In a general hydraulic system adopted in such construction machines, a hydraulic pump is operated by an engine or the like to generate hydraulic pressure, and high pressure hydraulic oil is supplied to an actuator such as a cylinder or a hydraulic motor, so that a boom or A driving force for driving an excavator, a machine main body, and the like (hereinafter referred to as a driving target) is generated. And when controlling this actuator, in order to control the hydraulic fluid supplied to an actuator, the solenoid valve is employ | adopted (for example, patent document 1).

  By the way, when a hydraulic cylinder is used as an actuator, if the meter-out side of the hydraulic cylinder is connected to both a high-pressure hydraulic source and a low-pressure hydraulic source via a solenoid valve, the solenoid valve is opened and closed continuously at high speed. By doing so, there is a possibility that the pressure and flow rate of the hydraulic oil flowing out from the hydraulic cylinder can be controlled. In other words, if the ratio of the time for connecting to the high pressure source and the time for connecting to the low pressure source (hereinafter referred to as duty ratio) is controlled, the pressure and flow rate of the hydraulic oil flowing out from the hydraulic cylinder may be controlled. There is.

  And when it is set as the above structure, there exists a possibility that the energy which the hydraulic fluid discharged | emitted from a hydraulic cylinder has can be collect | recovered by a high pressure source. That is, if the hydraulic oil is caused to flow from the hydraulic cylinder to the high pressure source, the energy of the hydraulic oil flowing into the high pressure source can be accumulated in the high pressure source. Then, the hydraulic oil that has flowed into the high pressure source can be used again as an energy source.

JP 2008-266909 A

However, when controlling the frequency of opening and closing the solenoid valve to control the pressure of the hydraulic cylinder and the flow rate of hydraulic oil flowing out of the hydraulic cylinder, the hydraulic oil pulsates due to the opening and closing of the solenoid valve, and the hydraulic cylinder and hydraulic circuit There is a possibility that the pulsation will increase and the hydraulic equipment will vibrate greatly and generate noise. Such vibration of the hydraulic cylinder and the hydraulic circuit may cause vibration of the drive target. In particular, when the resonance frequency of the hydraulic cylinder or hydraulic circuit matches the opening / closing frequency of the solenoid valve, a large vibration may occur.
If the pulsation of the hydraulic cylinder or the hydraulic circuit increases, the fluctuation of the flow rate of the hydraulic oil increases, and as a result, energy consumption may increase and energy efficiency may decrease.

  In view of the above circumstances, the present invention suppresses the pulsation of the working fluid and suppresses vibration and noise even when the pressure and flow rate of the working fluid in the cylinder are controlled by high-speed switching of the solenoid valve. An object is to provide a pulsation suppressing mechanism that can be prevented.

A pulsation suppressing mechanism according to a first aspect of the present invention includes a fluid chamber in which a working fluid is enclosed and a variable volume, and an inertial fluid chamber communicated with the fluid chamber. The inertial fluid chamber communicates with a high pressure source and a low pressure source. Provided between the inertial fluid chamber of the cylinder and the high-pressure source, and provided between the inertial fluid chamber of the cylinder and the low-pressure source. A mechanism for suppressing pulsation in an apparatus comprising: a low-pressure side switch that cuts off communication between the two; and a control unit that controls the operation of the low-pressure side switch and the high-pressure side switch, A substantially tubular side branch communicated with a chamber, wherein the control unit communicates the high-pressure side switch and the low-pressure side switch alternately with the inertial fluid chamber, and Controlling the high-pressure side switch; The switching frequency of the high-pressure side switch and the low-pressure side switch is controlled so that the switching frequency of the high-pressure side switch and the low-pressure side switch matches the natural frequency of the side branch. And
The pulsation suppressing mechanism of the second invention comprises a fluid chamber in which a working fluid is enclosed and a variable volume and an inertial fluid chamber communicated with the fluid chamber, and the inertial fluid chamber is communicated with a high pressure source and a low pressure source. Provided between the inertial fluid chamber of the cylinder and the high-pressure source, and provided between the inertial fluid chamber of the cylinder and the low-pressure source. A mechanism for suppressing pulsation in an apparatus comprising: a low-pressure side switch that cuts off communication between the two; and a control unit that controls the operation of the low-pressure side switch and the high-pressure side switch, A side branch that is variable in length and communicated with the chamber, wherein the control unit communicates the high-pressure side switch and the low-pressure side switch alternately with the inertial fluid chamber. Control the side switch and the high voltage side switch , And the said as switching frequency of the high voltage side switch the low-pressure side switch coincides with the natural frequency of the side branch, characterized in that changing the length of the side branch.
The pulsation suppressing mechanism of the third invention is the pulsation suppressing mechanism according to the first or second invention, wherein the control unit is configured to pulsate the working fluid in the vicinity of the switching frequency of the high-pressure side switch and the low-pressure side switch and the opening of the side branch. The frequency is controlled so as to coincide with the frequency at which the amplitude of is the smallest.
The pulsation suppressing mechanism of the fourth invention is characterized in that, in the first, second or third invention, a plurality of side branches having different frequency components to be absorbed are provided.
A pulsation suppressing mechanism according to a fifth aspect of the present invention is characterized in that, in the first, second, third or fourth aspect of the invention, the side branch contains therein a gas functioning as an elastic body.

According to the first invention, the pulsation of the working fluid generated due to switching between the high pressure side switch and the low pressure side switch can be absorbed by the side branch, so that the pulsation is generated in the device. Can be suppressed. Further, even if the pressure of the working fluid changes, and as a result, the natural frequency of the side branch changes, the pulsation of the working fluid can be appropriately suppressed by changing the switching frequency accordingly. And when regenerating the energy of a working fluid, the fall of energy regeneration efficiency can also be prevented.
According to the second invention, the pulsation of the working fluid generated by switching the high-pressure side switch and the low-pressure side switch can be absorbed by the side branch, so that the pulsation is generated in the device. Can be suppressed. Even if the sound velocity of the working fluid changes, the length of the side branch can be changed to make the natural frequency of the side branch coincide with the switching frequency. it can. And when regenerating the energy of a working fluid, the fall of energy regeneration efficiency can also be prevented.
According to the third invention, the mechanism and control for suppressing pulsation can be further simplified.
According to the fourth aspect of the invention, not only the primary frequency component but also the higher-order frequency component can be absorbed by the side branch, so that the pulsation of the working fluid can be more appropriately suppressed.
According to the fifth invention, since the gas functioning as an elastic body is accommodated in the side branch, even if the length of the side branch itself is shortened, it is possible to absorb the pulsation of the low switching frequency. .

It is a schematic block diagram of the hydraulic circuit 1 which employ | adopted the pulsation suppression mechanism of this embodiment. It is a schematic block diagram of the hydraulic circuit 1 which employ | adopted the pulsation suppression mechanism of other embodiment. It is a schematic block diagram of the hydraulic circuit 1 which employ | adopted the pulsation suppression mechanism of other embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings.
The pulsation suppressing mechanism of the present invention can suppress pulsation of working fluid generated in a fluid circuit having a cylinder. In particular, the pulsation suppressing mechanism of the present invention is characterized in that the pulsation of the working fluid generated when the energy of the working fluid is recovered in the fluid circuit having the cylinder can be suppressed.
In the present invention, the type of the working fluid is not particularly limited, and examples thereof include hydraulic oil, water, and air. Below, the case where hydraulic fluid is used as a hydraulic fluid is demonstrated.

(Description of the hydraulic circuit 1 provided with the pulsation suppressing mechanism of the present embodiment)
In FIG. 1, the code | symbol 1 has shown the hydraulic circuit provided with the pulsation suppression mechanism of this embodiment. The hydraulic circuit 1 includes a hydraulic cylinder 2. The hydraulic cylinder 2 has a rod 2r protruding from the main body 2b, and can apply an external force or receive an external force via the rod 2r.

  As shown in FIG. 1, the hydraulic cylinder 2 has a piston 2p to which the base end of a rod 2r is connected, and a space 2h inside the main body 2b is divided by the piston 2p. In the space 2h in the main body 2b divided by the piston 2p, the space (piston side chamber 2s) on the side where the piston 2p and the rod 2r are not connected is filled with hydraulic oil. The piston side chamber 2s corresponds to a fluid chamber referred to in the claims.

  As shown in FIG. 1, the main body 2b includes an inertial fluid chamber 2i that communicates with the piston-side chamber 2s. The inertial fluid chamber 2i is a hollow space having a smaller internal volume than the space 2h of the main body 2b. The inertial fluid chamber 2i is also filled with hydraulic oil in the same manner as the piston side chamber 2s. The inertial fluid chamber 2i may be a simple pipe, and its shape and size are not particularly limited.

  As shown in FIG. 1, a low pressure source LP is connected to the inertial fluid chamber 2i by a low pressure pipe PL. The low-pressure source LP is, for example, a tank for storing hydraulic oil, and is normally maintained at atmospheric pressure. That is, the hydraulic oil in the low pressure source LP is in an atmospheric pressure state.

  The low-pressure pipe PL is provided with a low-pressure side switch 3L. By opening and closing the low-pressure side switch 3L, the inertia fluid chamber 2i and the low-pressure source LP can be disconnected from each other. It has become.

  As shown in FIG. 1, a high pressure source HP is connected to the inertial fluid chamber 2i by a high pressure pipe PH. The high pressure source HP is, for example, a tank in which hydraulic oil having a pressure higher than that of the low pressure source LP is accumulated.

  The high-pressure pipe PH is provided with a high-pressure side switch 3H. By opening and closing the high-pressure side switch 3H, the inertia fluid chamber 2i and the high-pressure source HP can be disconnected from each other. ing.

  For this reason, if the high pressure side switch 3H is opened and the inertia fluid chamber 2i communicates with the high pressure source HP, high pressure hydraulic oil can be supplied from the high pressure source HP to the piston side chamber 2s via the inertia fluid chamber 2i. . Then, if the pressure of the hydraulic oil higher than the pressure applied to the piston side chamber 2s via the piston 2p is larger, the piston 2p can be moved so that the volume of the piston side chamber 2s becomes larger. .

  Moreover, in FIG. 1, the code | symbol 5 has shown the control part which controls the action | operation of the high voltage | pressure side switch 3H and the low voltage | pressure side switch 3L. The control unit 5 has a function of instructing the switching timing to the high voltage side switch 3H and the low voltage side switch 3L. Specifically, it has a function of controlling the opening and closing timing of the high voltage side switch 3H and the low voltage side switch 3L so that they are alternately opened. Hereinafter, a cycle in which the high-voltage side switch 3H and the low-voltage side switch 3L are alternately opened is referred to as a switching frequency H.

  Since the configuration is as described above, when an external force F that presses the rod 2r of the hydraulic cylinder 2 in the hydraulic circuit 1 (hereinafter, simply referred to as an external force F) is applied, the hydraulic circuit 1 Energy can be recovered in the high pressure source HP.

  First, when an external force F is applied, the low pressure side switch 3L is opened, and the inertial fluid chamber 2i and the low pressure source LP are communicated. Then, a flow of hydraulic oil is generated from the piston side chamber 2s through the inertial fluid chamber 2i toward the low pressure source LP.

  In a state where the flow of hydraulic oil is generated, the low pressure side switch 3L is closed and the high pressure side switch 3H is opened. Then, since the flow of the hydraulic oil has inertial energy, the hydraulic oil flows out from the inertial fluid chamber 2i toward the high pressure source HP until the hydraulic oil is decelerated and the kinetic energy is lost. In other words, the hydraulic oil flows into the high pressure source HP from the inertial fluid chamber 2i.

  Then, in the high pressure source HP, even if the stored hydraulic fluid increases, the pressure of the hydraulic fluid does not decrease. Therefore, energy can be recovered in the high pressure source HP as much as the amount of hydraulic fluid increases. .

  Before the hydraulic oil decelerates and loses kinetic energy, the high pressure side switch 3H is closed and the low pressure side switch 3L is opened. As a result, the flow of hydraulic oil from the piston side chamber 2s through the inertial fluid chamber 2i toward the low pressure source LP is generated again.

  When the flow of the hydraulic oil occurs, the low pressure side switch 3L is closed and the high pressure side switch 3H is opened. Then, since the hydraulic oil flows into the high pressure source HP from the inertial fluid chamber 2i, energy can be recovered to the high pressure source HP.

  As described above, in the hydraulic circuit 1 provided with the pulsation suppressing mechanism of the present embodiment, the energy of the external force F applied to the rod 2r of the hydraulic cylinder 2 can be increased by alternately opening and closing the high pressure side switch 3H and the low pressure side switch 3L. It can be recovered in the high pressure source HP.

(Description of pulsation suppression mechanism of this embodiment)
Next, the pulsation suppressing mechanism will be described.
As described above, when the high-pressure side switch 3H and the low-pressure side switch 3L are alternately opened and closed to recover the energy of the hydraulic oil, the force ( (Exciting force) may occur and pulsation may occur in the hydraulic oil. The pulsation suppression mechanism of this embodiment is provided to suppress the pulsation of such hydraulic oil.
If there is pulsation of the hydraulic oil when recovering the energy of the hydraulic oil, there is a possibility that the flow of the hydraulic oil described above is disturbed and the hydraulic oil does not sufficiently flow to the high pressure source HP or the low pressure source LP of the hydraulic oil. Yes, there is a possibility that the energy recovery efficiency of the hydraulic oil will be reduced. However, if the pulsation suppressing mechanism of the present embodiment is provided in the hydraulic circuit 1, the pulsation of the hydraulic oil can be suppressed, so that the energy regeneration rate can be improved.

  As shown in FIG. 2, the pulsation suppressing mechanism includes a side branch 11. The side branch 11 is a hollow tubular or cylindrical member, and is a member having one end opened and the other end closed. The side branch 11 has an opening end connected to the inertial fluid chamber 2i described above, and the inside thereof communicates with the inside of the inertial fluid chamber 2i through the opening. For this reason, the inside of the side branch 11 is also filled with the working oil, and when the working oil moves in the inertial fluid chamber 2i, the working oil in the side branch 11 also vibrates.

  In the pulsation suppressing mechanism of the present embodiment, a method of suppressing the pulsation of the hydraulic circuit 1 by providing the side branch 11 is adopted. When the side branch 11 is provided, the effect of reducing the pulsation of the hydraulic oil increases as the natural frequency of the side branch 11 and the frequency of the pulsation of the hydraulic fluid flowing in the hydraulic circuit 1 including the inertial fluid chamber 2i coincide with each other with higher accuracy. Becomes larger. On the other hand, if the natural frequency of the side branch 11 deviates from the frequency of hydraulic oil pulsation, the pulsation reduction effect is significantly reduced.

  For this reason, in the pulsation suppression mechanism of the present embodiment, the control unit 5 adjusts the switching frequency H in order to obtain the hydraulic oil pulsation reduction effect, and matches the natural frequency of the frequency side branch 11 of the hydraulic oil pulsation. You are in control.

That is, if the high-pressure side switch 3H and the low-pressure side switch 3L are switched, pulsation occurs in the hydraulic oil in the hydraulic circuit 1 and the hydraulic oil pressure fluctuates. However, since the switching frequency H is adjusted so that the pulsation of the hydraulic oil matches the natural frequency of the side branch 11, the pulsation of the hydraulic oil can be absorbed by the side branch 11.
Therefore, even if the high pressure side switch 3H and the low pressure side switch 3L are alternately opened and closed, the occurrence of pulsation in the hydraulic circuit 1 can be suppressed.

For example, when the sound speed of hydraulic oil is V and the length of the side branch 11 is L, the primary natural frequency f of the side branch 11 can be obtained by the following formula 1 from acoustic theory. For this reason, if the switching frequency H is controlled so as to satisfy the following expression, the pulsation of the hydraulic oil can be absorbed by the side branch 11.

L = V / 4f (Formula 1)

(Adjustment of switching frequency H)
By the way, since the natural frequency f of the side branch 11 is affected by the speed of sound (or elastic modulus and density) as shown in the above equation, there is a possibility that the natural frequency f changes with changes in conditions such as the hydraulic oil pressure. To control the natural frequency f of the side branch 11 at all times.

  Control of the switching frequency H is easy when the sonic speed of the hydraulic oil hardly changes during the operation of the hydraulic equipment provided with the hydraulic circuit 1 or when the sonic speed of the hydraulic oil can be estimated according to the operating state of the hydraulic equipment. .

  For example, if the relationship between the operating status of the hydraulic device and the sound speed of the hydraulic oil is obtained in advance and a map showing the relationship between the operating status of the hydraulic device and the sound speed of the hydraulic oil is stored in the control unit 5, The controller 5 can estimate the sound speed according to the map. Then, if the control unit 5 controls the switching frequency H based on this sound speed, the switching frequency H can be matched with the natural frequency f of the side branch 11.

  On the other hand, in a hydraulic circuit such as a construction machine, air is generally mixed in hydraulic oil, and the equivalent elastic modulus changes considerably due to a change in pressure of the hydraulic oil. If the relationship between the operating state of the hydraulic device and the sound speed (or elastic modulus and density) is obtained in advance, the state of the sound speed change due to the pressure change can be predicted approximately.

  Then, since the length L of the side branch 11 is known, if the approximate value of the natural frequency f of the side branch 11 can be obtained by directly measuring the sound speed of the hydraulic oil, it is based on the natural frequency f. The control unit 5 can control the switching frequency H. Then, the pulsation frequency of the hydraulic oil and the natural frequency f of the side branch 11 can be matched to some extent, so that even if the sound speed of the hydraulic oil changes and as a result, the natural frequency f of the side branch 11 changes. The occurrence of hydraulic oil pulsation can be appropriately suppressed to some extent.

  For example, the approximate value of the sound speed is estimated based on the relational expression between the average value Ys of the hydraulic oil and the sound speed. The relational expression between the two is obtained in advance through experiments or the like. Then, using the approximate value of the obtained sound speed, the approximate natural frequency f of the side branch 11 is obtained by the above equation 1, and the switching frequency H of the approximate optimum condition is set. In the vicinity of the switching frequency H, the optimum switching frequency H can be set by estimating the natural frequency f by a method as described later in (1) to (3).

  In the above method, an approximate value of the natural frequency f is obtained. However, the natural frequency f of the side branch 11 can be directly estimated, and the control unit 5 can control the switching frequency H so as to coincide with the estimated natural frequency f. Since this method can further improve the accuracy of the estimated natural frequency f, the pulsation suppressing effect can be further improved.

For example, pressure sensors Pa and Ps are attached to the inside and outside of the side branch 11 as shown in FIG. 1, and the pressure pulsation of the hydraulic oil is measured. That is, the pressure pulsation inside the side branch 11 (the back side, that is, the closed end) is measured by the pressure sensor Pa, and the pulsation outside the side branch 11 (near the opening end or in the inertial fluid chamber 2i) is measured by the pressure sensor Ps. Measure with
In this case, the amplitude of the primary component of the switching frequency H among the pressure pulsations inside the side branch 11 is | Xs |, and the amplitude of the primary component of the switching frequency H among the pressure pulsations outside the side branch 11 is | Xc |. Then, the natural frequency f of the side branch 11 can be estimated by the following three methods. Xs and Xc are complex numbers including phase information.

(1) A method of changing the switching frequency H, searching for a frequency that minimizes the absolute value of Xs, and setting the frequency to the natural frequency f. (2) Changing the switching frequency H, so that the absolute value of Xs / Xc is A method of searching for a frequency so as to be maximized and setting the frequency to the natural frequency f (3) A frequency at which the phase of Xs / Xc changes by approximately 180 degrees or a frequency that is shifted by approximately 90 degrees by changing the switching frequency H Is used as a resonance point, and the frequency is set to the natural frequency f.

  Further, the relationship between the average value Ys of the hydraulic oil and the natural frequency f is stored as a mathematical expression or data based on the results of the above measurements (1) to (3) under various conditions, as described in paragraph 0039 above. A method for estimating the natural frequency f from the average value Ys of the hydraulic oil is conceivable. In the case of this method, the accuracy is lower than that of directly measuring the natural frequency f, but it can be estimated more accurately than the method of paragraph 0039.

(Other examples)
Further, in the above example, when conditions such as the pressure of hydraulic oil change, the switching frequency H is changed to suppress the occurrence of vibration.
However, if a side branch 11 whose length can be changed (variable length side branch) is adopted, pulsation occurs when conditions such as hydraulic oil pressure change by changing the length of the side branch 11. Generation can be suppressed, and the energy regeneration rate can be improved.

  For example, the side branch 11 having a cylinder structure having a piston inside is adopted. In this case, if the piston is operated, the length of the space inside the side branch 11 can be changed. Then, according to the speed of sound of the hydraulic oil, if the control unit 5 operates the piston so that the length L of the space inside the side branch 11 satisfies the condition of the formula 1, the switching frequency H is not changed. Moreover, the pulsation reduction effect by the side branch 11 can be acquired.

  Even when the length L of the side branch 11 is changed, it is necessary to check whether or not the natural frequency f matches the switching frequency H. In this case, similarly to the above-described embodiment (when the switching frequency H is changed), the length L of the side branch 11 is changed, and the pressure in the side branch 11 is measured to determine whether or not they match. You just have to check. For example, the length L of the side branch 11 obtained from the approximate value of the natural frequency f calculated using the average pressure in the side branch 11 is set as the initial value. Then, in the vicinity of the initial value, a condition that optimizes the length L of the side branch 11 can be examined by a method that approximates the above-described method (that is, a method that changes the length L of the side branch 11). .

(About side branch 11)
The side branch 11 only needs to be hollow and have a space in which hydraulic oil can be accommodated, and its material and structure are not particularly limited. For example, a metal pipe with one end closed may be used as the side branch 11, or a tubular member having flexibility and deformability such as a rubber tube having an effect of reducing the sound speed may be used as the side branch 11. Also good.

(Other examples of side branch)
Further, the side branch 11 may be a side branch 11 using a small accumulator using air pressure (accumulator-type side branch) instead of a side branch having a continuous structure (such as a tube) as described above (see FIG. 2). ). For example, a structure in which the air portion is a spring and the moving hydraulic oil portion is a mass can be employed. In this case, since the natural frequency f of the side branch 11c is determined from the cross-sectional area of the hydraulic oil, if the mechanism for adjusting the amount of hydraulic oil is provided, the natural frequency f of the side branch 11c is changed. Is also possible.

  In addition, a room filled with air is connected to a high-pressure and low-pressure air source (for example, a high-pressure source HP, a low-pressure source LP, etc.), and the room filled with air and the air source are normally shut off by a valve. You may leave as. Even in this case, the natural frequency f of the side branch 11c can be adjusted by sending air from the high-pressure air source and allowing the air to escape to the low-pressure air source.

  Furthermore, when the switching frequency H is high, the length L of the side branch 11 does not have to be so long. However, when the switching frequency H is low, the length L must be increased. . If the length of the side branch 11 is increased, the structure of the hydraulic circuit 1 provided with the pulsation suppressing mechanism is complicated accordingly. However, if the accumulator side branch as described above is employed, such a problem can be prevented.

  In FIG. 2, the code | symbol 11c has shown the accumulator type | mold side branch. The accumulator side branch 11c is separated into two chambers by a bag-like elastic body, a piston, or the like. In the case of a piston, it can be moved along the axial direction of the side branch. Of the two chambers separated by the piston and the elastic body, one chamber communicates with the hydraulic circuit, and the other chamber is filled with air a. With such a configuration, the air a can function like a spring, so that it is possible to absorb pulsations at a low switching frequency even if the length of the side branch itself is shortened.

  Further, if the mass portion (that is, the portion containing the hydraulic oil) is made sufficiently small, the accumulator side branch 11c exhibits only the spring effect due to the elasticity of air. Even in this case, if the spring constant is sufficiently small, the pulsation suppressing effect can be obtained to some extent although the natural frequency f of the side branch 11c is not as high as that of the side branch 11c regardless of the natural frequency f of the side branch 11c. it can. Further, in the case of this configuration, there is an advantage that the pulsation suppressing effect can be effectively obtained not only for the primary component of pulsation but also for higher-order components.

  Note that the elasticity of the air a changes greatly depending on the pressure, and if the elasticity of the air a changes, the natural frequency f of the side branch 11c also changes. However, if the natural frequency f is adjusted by a method such as adjusting the switching frequency H by the method as described above, or adjusting the passage cross-sectional area of hydraulic oil or the amount of charged air, the elasticity of the air a changes. However, the pulsation of hydraulic fluid can be absorbed appropriately.

  Further, the accumulator side branch 11c does not necessarily need to be divided by a piston or a bag-like structure, and the air a may be simply brought into contact with the hydraulic oil forming an interface. However, in order to prevent problems such as mixing of air a and hydraulic oil, it is preferable to separate them so as not to contact each other by a piston or the like.

(Other control methods)
Further, in the above example, a case where both the pressure outside the side branch 11 and the pressure inside the side branch 11 are measured, and the switching frequency H and the natural frequency f of the side branch 11 are changed based on both measured values. Explains.
However, the switching frequency H and the natural frequency of the side branch 11 are based only on the pressure outside the side branch 11 (near the opening end or in the inertial fluid chamber 2i), that is, based only on the amplitude of the pulsation outside the side branch 11. f may be changed. Specifically, the switching frequency H and the natural frequency f of the side branch 11 may be changed to obtain a condition that minimizes the amplitude of pulsation outside the side branch 11.
In this case, it is only necessary to measure the pressure at one location and analyze the measured value, and the pressure measurement can be performed easily and accurately, so the mechanism and control for suppressing pulsation are easier. Become.

(Multiple side branch)
In the above example, the case where only one side branch 11 or the like is provided has been described. Even in this case, it is possible to effectively absorb the pulsation of the frequency component which is one time the switching frequency H. However, when the high pressure side switch 3H and the low pressure side switch 3L are switched, the hydraulic oil is vibrated. However, components that excite the hydraulic oil have an integral multiple of the switching frequency H. That is, the pulsation of the hydraulic oil includes a component having a frequency that is an integral multiple of the switching frequency H.

  Therefore, in order to effectively absorb the pulsation by the side branch 11 or the like, it is preferable to provide the side branch 11 or the like that absorbs not only the primary frequency component but also the high-order frequency component. That is, it is preferable to provide the side branch 11 and the like suitable for the frequency component to be absorbed. Then, not only the primary frequency component but also the higher-order frequency component can be appropriately absorbed by the side branch 11 or the like, so that the occurrence of hydraulic oil pulsation can be more appropriately suppressed.

  For example, as shown in FIG. 3, two side branches 11A and 11B are provided, and the length of the side branch 11B is set to half the length of the side branch 11A. Then, if the natural frequency f of the side branch 11A matches the switching frequency H, the side branch 11B can absorb the secondary frequency component of pulsation.

  Of course, even when variable length side branches and accumulator side branches that can change the length are used, if the frequency components absorbed by each side branch are adjusted differently, not only the primary frequency components but also the higher order frequency components Can also be absorbed.

(About the high pressure side switch 3H and the low pressure side switch 3L)
The high pressure side switch 3H and the low pressure side switch 3L are not particularly limited as long as they can cut off communication between the inertial fluid chamber 2i and the high pressure source HP or the low pressure source LP. For example, a generally used high-speed switchable solenoid valve can be used.

  The pulsation suppressing mechanism of the present invention is suitable as a mechanism for suppressing vibration in a hydraulic system using a hydraulic cylinder.

DESCRIPTION OF SYMBOLS 1 Energy recovery apparatus 2 Cylinder 2h Space 2s Fluid chamber 2i Inertial fluid chamber 3H High pressure side switch 3L Low pressure side switch 5 Controller 10 Pulsation suppression mechanism 11 Side branch HP High pressure source LP Low pressure source PH High pressure piping PL Low pressure piping

Claims (5)

A cylinder having a variable volume in which a working fluid is enclosed and an inertial fluid chamber communicating with the fluid chamber, the inertial fluid chamber communicating with a high pressure source and a low pressure source;
A high-pressure side switch provided between the inertial fluid chamber of the cylinder and the high-pressure source, for disconnecting communication between the two;
A low-pressure side switch provided between the inertial fluid chamber of the cylinder and a low-pressure source, which cuts off communication between the two;
A control unit for controlling the operation of the low-pressure side switch and the high-pressure side switch;
Comprising a substantially tubular side branch communicating with the inertial fluid chamber;
The controller is
Controlling the low-pressure side switch and the high-pressure side switch so that the high-pressure side switch and the low-pressure side switch communicate with the inertial fluid chamber alternately,
The operation of the high-pressure side switch and the low-pressure side switch is controlled so that the switching frequency of the high-pressure side switch and the low-pressure side switch matches the natural frequency of the side branch. The pulsation suppression mechanism. A cylinder having a variable volume in which a working fluid is enclosed and an inertial fluid chamber communicating with the fluid chamber, the inertial fluid chamber communicating with a high pressure source and a low pressure source;
A high-pressure side switch provided between the inertial fluid chamber of the cylinder and the high-pressure source, for disconnecting communication between the two;
A low-pressure side switch provided between the inertial fluid chamber of the cylinder and a low-pressure source, which cuts off communication between the two;
A control unit for controlling the operation of the low-pressure side switch and the high-pressure side switch;
A side branch that is communicated with the inertial fluid chamber and capable of changing its length;
The controller is
Controlling the low-pressure side switch and the high-pressure side switch so that the high-pressure side switch and the low-pressure side switch communicate with the inertial fluid chamber alternately,
A pulsation suppressing mechanism, wherein a length L of the side branch is changed so that a switching frequency of the high-pressure side switch and the low-pressure side switch coincides with a natural frequency of the side branch. The controller is
The switching frequency of the high-pressure side switch and the low-pressure side switch is controlled so as to coincide with a frequency at which the amplitude of the pulsation of the working fluid in the vicinity of the opening of the side branch is the same. Item 3. A pulsation suppressing mechanism according to Item 1 or 2. 4. The pulsation suppressing mechanism according to claim 1, further comprising a plurality of side branches having different frequency components to be absorbed. The side branch is
5. The pulsation suppressing mechanism according to claim 1, wherein a gas functioning as an elastic body is accommodated therein.

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