JP6114141B2 - Exciter hydraulic power unit - Google Patents

Description

  The present invention relates to a hydraulic power source apparatus for a vibrator that supplies hydraulic oil to the vibrator.

  2. Description of the Related Art Conventionally, a vibrator that performs a durability test by applying a periodic vibration to a subject using expansion and contraction of a hydraulic cylinder has been used.

  Patent Document 1 discloses a control device for a hydraulic exciter that includes a cylinder in which supply and discharge of hydraulic oil from a hydraulic source is controlled by switching a servo valve, and a table that is vibrated by the cylinder.

JP-A-10-103302

  However, in general, in a vibration exciter as described in Patent Document 1, a hydraulic source always supplies a certain amount of hydraulic oil, and excess hydraulic oil not used by the cylinder is supplied to a tank via a relief valve. To reflux. Therefore, the energy consumption of the hydraulic power source cannot be suppressed.

  The present invention has been made in view of the above problems, and an object of the present invention is to save energy in a hydraulic power source device of a vibration exciter.

  The present invention is a hydraulic power source device that supplies hydraulic oil to a vibration exciter that periodically generates vibrations by supplying and discharging hydraulic oil, a variable displacement hydraulic pump capable of adjusting the hydraulic oil discharge capacity, A pressure detector for detecting the pressure of hydraulic oil supplied from the hydraulic pump to the vibration exciter; and a controller for adjusting the discharge capacity of the hydraulic pump based on the pressure of the hydraulic oil detected by the pressure detector; The control unit gradually decreases the discharge capacity of the hydraulic pump from an initial value, and the pressure of the hydraulic oil detected by the pressure detector causes the vibrator to stably generate vibration. The discharge capacity of the hydraulic pump is adjusted to the discharge capacity before being lower than the determination value when it is determined that the determination value is lower than the minimum possible value.

  In the present invention, the control unit decreases the discharge capacity of the variable displacement hydraulic pump step by step, and determines that the pressure of the hydraulic oil supplied from the hydraulic pump to the shaker is lower than the determination value. Adjust the hydraulic pump to the discharge capacity before it falls below the value. This determination value is set to a minimum value at which the shaker can stably generate vibration. Therefore, the discharge capacity of the hydraulic pump is set to the minimum necessary capacity. Therefore, energy saving of the hydraulic power source device of the vibration exciter can be achieved.

1 is a hydraulic circuit diagram of a hydraulic power source device for a vibrator according to an embodiment of the present invention. It is a block diagram of the hydraulic power source apparatus of the vibration exciter concerning an embodiment of the invention. It is a flowchart of the discharge capacity control in the hydraulic power source apparatus of the vibration exciter which concerns on embodiment of this invention. It is a timing chart of the discharge capacity control in the hydraulic power source device of the vibration exciter concerning an embodiment of the invention. (A) And (b) is a figure explaining the case where it determines with the pressure of hydraulic fluid having fallen below the determination value in the hydraulic power source device of the shaker which concerns on embodiment of this invention. It is a figure which illustrates about the stepwise adjustment of the discharge capacity in case a hydraulic pump has a main pump and a sub pump. It is a figure illustrated about the stepwise adjustment of the discharge capacity in case a hydraulic pump has only a main pump.

  Hereinafter, a hydraulic power source apparatus (hereinafter simply referred to as a “hydraulic power source apparatus”) 100 for a vibrator according to an embodiment of the present invention will be described with reference to the drawings.

  The hydraulic power source apparatus 100 supplies hydraulic oil to a vibration exciter 101 (see FIG. 2) that periodically generates vibrations by supplying and discharging hydraulic oil.

  The vibration exciter 101 includes a reciprocating hydraulic cylinder (not shown) having a pair of oil chambers defined in the cylinder by a piston that slides on the inner periphery of the cylinder, and hydraulic oil to the pair of oil chambers. And a servo valve (not shown) for switching between supply and discharge. The vibration exciter 101 imparts vibration to the subject by expansion and contraction of a piston rod provided integrally with the piston of the hydraulic cylinder.

  The vibration exciter 101 applies periodic vibration to the subject by periodically switching the servo valve. When the operation of the vibration exciter 101 is in a steady state, the flow rate of the hydraulic oil necessary for switching the servo valve becomes substantially constant.

  Conventionally, hydraulic oil having a constant flow rate is supplied from the hydraulic power source device to the vibration exciter 101, and excess hydraulic oil not used by the hydraulic cylinder is returned to the tank via the relief valve. Therefore, the energy consumption of the hydraulic power source device cannot be suppressed. In view of this, in the hydraulic power source apparatus 100, the hydraulic oil having the minimum flow rate at which the shaker 101 can stably generate vibration is supplied to the shaker 101. Hereinafter, the hydraulic power source apparatus 100 will be described in detail.

  First, the configuration of the hydraulic power source apparatus 100 will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the hydraulic power source apparatus 100 includes a tank 1 in which hydraulic oil is stored, a hydraulic pump 10 that sucks and discharges hydraulic oil from the tank 1, and an operation that is supplied from the hydraulic pump 10 to the shaker 101. A pressure sensor 20 as a pressure detector that detects the pressure of the oil, and a control unit 30 (see FIG. 2) that adjusts the discharge capacity of the hydraulic pump 10 based on the pressure of the hydraulic oil detected by the pressure sensor 20.

  Although not shown, the hydraulic pump 10 supplies hydraulic oil to the plurality of vibrators 101. That is, the hydraulic power source device 100 is a common hydraulic power source that supplies hydraulic oil to a plurality of shakers 101 installed in a factory or a certain area in the factory. The hydraulic pump 10 is always operated when the vibration exciter 101 is driven to discharge the hydraulic oil, and the sub-pump 12 is operated when the discharge capacity of the main pump 11 is insufficient to discharge the hydraulic oil. And have.

  The main pump 11 and the sub pump 12 are swash plate type variable displacement piston pumps capable of adjusting the discharge capacity of hydraulic oil. Since the main pump 11 and the sub pump 12 may be variable displacement type, other types such as a variable displacement vane pump may be used.

  The main pump 11 is rotationally driven by an electric motor 11a. The main pump 11 has a tilt actuator 11b (see FIG. 2) that adjusts the tilt angle of the swash plate. The main pump 11 discharges hydraulic oil sucked from the tank 1 through the suction passage 2 to the supply passage 3.

  The supply passage 3 is provided with a check valve 3 a that prevents the backflow of the hydraulic oil discharged from the main pump 11. From the supply passage 3 between the main pump 11 and the check valve 3a, a reflux passage 4 is branched to allow a part or all of the hydraulic oil discharged from the main pump 11 to return to the tank 1. The recirculation passage 4 is provided with a relief valve 4a that recirculates the working oil to the tank 1 when the pressure of the working oil becomes a set value or more.

  Similarly, the sub pump 12 is rotationally driven by the electric motor 12a. The sub pump 12 includes a tilt actuator 12b (see FIG. 2) that adjusts the tilt angle of the swash plate. The sub pump 12 discharges the working oil sucked from the tank 1 through the suction passage 5 to the supply passage 6.

  The supply passage 6 is connected to the supply passage 3 through which the hydraulic oil discharged from the main pump 11 flows. The supply passage 6 is provided with a check valve 6 a that prevents the backflow of the hydraulic oil discharged from the sub pump 12. From the supply passage 6 between the sub-pump 12 and the check valve 6a, a return passage 7 that branches back or returns part or all of the hydraulic oil discharged by the sub-pump 12 to the tank 1 is provided. The recirculation passage 7 is provided with a relief valve 7a that recirculates the working oil to the tank 1 when the pressure of the working oil becomes a set value or more.

  The pressure sensor 20 detects the pressure of the hydraulic oil in the supply passage 3 downstream from the joining position of the hydraulic oil discharged from the main pump 11 and the sub pump 12. The pressure sensor 20 is electrically connected to the control unit 30. The pressure sensor 20 transmits an electrical signal corresponding to the detected hydraulic oil pressure to the control unit 30.

  Here, for example, when the amplitude of the hydraulic cylinder in the shaker 101 is increased while the flow rate of the hydraulic oil supplied to the shaker 101 is constant, the pressure of the hydraulic oil decreases. Further, if the flow rate of the hydraulic oil is decreased while the vibration condition in the vibrator 101 is kept constant, the pressure of the hydraulic oil decreases. As described above, the flow rate of the hydraulic oil supplied to the vibration exciter 101 has a correlation with the pressure of the hydraulic oil supplied from the hydraulic power source device 100. Therefore, in the hydraulic power source apparatus 100, the flow rate of the hydraulic oil is controlled based on the pressure of the hydraulic oil supplied from the hydraulic pump 10 to the shaker 101.

  The control unit 30 controls the hydraulic power source device 100. The control unit 30 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and an I / O interface (input / output interface). The RAM stores data in the processing of the CPU, the ROM stores a control program of the CPU in advance, and the I / O interface is used for input / output of information with the connected device. Control of the hydraulic power source apparatus 100 is realized by operating a CPU, RAM, and the like according to a program stored in the ROM.

  The control unit 30 reduces the discharge capacity of the hydraulic pump 10 step by step from the initial value, and the hydraulic oil pressure detected by the pressure sensor 20 is the minimum that the shaker 101 can stably generate vibration. When it is determined that the value is lower than the determination value, the discharge capacity of the hydraulic pump 10 is adjusted to the discharge capacity before the determination value is decreased.

  The hydraulic power source device 100 includes a return passage 8 that returns hydraulic oil discharged from the hydraulic cylinder of the vibration exciter 101 to the tank 1. The return passage 8 is provided with a filter 8a for removing foreign substances from the hydraulic oil.

  Next, discharge capacity control in the hydraulic power source apparatus 100 will be described with reference to FIGS. In the timing chart of FIG. 4, the horizontal axis is time, and the vertical axis is the flow rate and pressure of the hydraulic oil supplied from the hydraulic pump 10 to the shaker 101. 6 and 7 show examples of set values of the discharge capacity of the hydraulic pump 10 when the flow rate of hydraulic oil is switched to 30 levels.

In step 11 of FIG. 3, the hydraulic power source apparatus 100 is activated. Subsequently, in step 12, the operation is performed so that the discharge capacity of the hydraulic pump 10 becomes the maximum flow rate. This state is time t ₀ in FIG. Further, the state of the maximum flow rate corresponds to the initial value of the discharge capacity of the hydraulic pump 10.

  When the hydraulic pump 10 includes the main pump 11 and the sub pump 12, both the main pump 11 and the sub pump 12 are operated with a discharge capacity of 100% as indicated by a set value 1 shown in FIG. At this time, excess hydraulic oil that has not been used in the vibrator 101 is returned to the tank 1 when the relief valve 4a and the relief valve 7a are opened.

  On the other hand, when the hydraulic pump 10 has only the main pump 11, the main pump 11 is operated at a discharge capacity of 100% as shown in the setting value 1 shown in FIG. 7. Also at this time, excess hydraulic oil that has not been used in the shaker 101 is returned to the tank 1 when the relief valve 4a is opened.

  In step 13, it is determined whether or not a vibration signal indicating that vibration has started is input to the control unit 30 from the vibrator 101. If it is determined in step 13 that an excitation signal has been input, the process proceeds to step 14. On the other hand, if it is determined in step 13 that no excitation signal is input, step 13 is repeated until the excitation signal is input.

  Subsequently, in step 14, it is determined whether or not the set time has elapsed. If it is determined in step 14 that the set time has elapsed, the process proceeds to step 15. On the other hand, if it is determined in step 14 that the set time has not elapsed, step 14 is repeated until the set time has elapsed.

In FIG. 4, an excitation signal is input to the control unit 30 at time t ₁ . Then, the between time t ₁ of time t ₂ corresponds to the set time. This set time is set to a sufficient time required for setting the vibration conditions and preparing for the vibration test after the vibrator 101 starts the vibration.

In step 15, the flow rate of the hydraulic pump 10 is decreased by one step. When the hydraulic pump 10 includes the main pump 11 and the sub pump 12, the discharge capacity of the sub pump 12 is set to 90% while the main pump 11 is operated at a discharge capacity of 100% as shown in the setting value 2 shown in FIG. Decrease. At this time, the control unit 30 transmits the operation signal to the tilting actuator 12b, proportionally reducing the discharge capacity during the time t ₂ as shown in FIG. 4 to time t _3. Therefore, the discharge capacity of the sub pump 12 does not decrease rapidly.

On the other hand, when the hydraulic pump 10 has only the main pump 11, the discharge capacity of the main pump 11 is reduced to 95% as shown in the setting value 2 shown in FIG. Also at this time, the control unit 30 transmits the operation signal to the tilting actuator 11b, proportionally reducing the discharge capacity during the time t ₂ as shown in FIG. 4 to time t _3. Therefore, the discharge capacity of the main pump 11 does not rapidly decrease.

  In step 16, it is determined whether or not the pre-monitoring standby time has elapsed. If it is determined in step 16 that the pre-monitoring standby time has elapsed, the process proceeds to step 17. On the other hand, if it is determined in step 16 that the pre-monitoring elapsed time has not elapsed, step 16 is repeated until the pre-monitoring standby time elapses.

In Figure 4, it is between the time t ₃ of the time t ₄ corresponds to the prior waiting time monitoring. This standby time before monitoring is set to a sufficient time required for the hydraulic oil flow rate to stabilize after the discharge capacity of the hydraulic pump 10 is further reduced.

In step 17, the pressure sensor 20 detects the pressure of the hydraulic oil supplied from the hydraulic pump 10 to the shaker 101. The pressure of the hydraulic oil pulsates due to the drive timing of the hydraulic cylinder in the shaker 101. Therefore, the pressure sensor 20 continues to detect the pressure of the hydraulic oil during the pressure monitoring time from time t ₄ to time t ₅ .

  In step 18, it is determined whether or not the hydraulic oil pressure detected by the pressure sensor 20 is smaller than a determination value. In this manner, the control unit 30 determines whether or not the pressure detected by the pressure sensor 20 has fallen below the determination value after a predetermined standby time has elapsed since the discharge capacity of the hydraulic pump 10 has been further reduced. This determination value is set to a minimum value at which the vibration exciter 101 can stably generate vibration.

  The determination in step 18 is specifically two determinations shown in FIGS. 5 (a) and 5 (b). The determination value has an upper limit determination value and a lower limit determination value that is set lower than the upper limit determination value.

  Specifically, the first determination is made when the hydraulic oil pressure detected by the pressure sensor 20 has never reached the upper limit determination value during the pressure monitoring time, as shown in FIG. The hydraulic oil pressure is determined to be lower than the determination value. As shown in FIG. 5 (b), the second determination is that the hydraulic oil pressure is detected when the hydraulic oil pressure detected by the pressure sensor 20 is not more than the lower limit determination value even once during the pressure monitoring time. Is determined to be below the determination value.

  As described above, the control unit 30 operates when the pressure of the hydraulic oil detected by the pressure sensor 20 does not reach the upper limit determination value within a predetermined period or falls below the lower limit determination value within the predetermined period. It is determined that the oil pressure has fallen below the determination value. Thereby, it can be reliably determined that the pressure of hydraulic oil that pulsates due to the drive timing of the hydraulic cylinder in the shaker 101 has fallen below the determination value.

  If it is determined in step 18 that the hydraulic oil pressure is smaller than the determination value, the process proceeds to step 19. On the other hand, if it is determined in step 18 that the hydraulic oil pressure is not smaller than the determination value, that is, it is determined to be equal to or higher than the determination value, the process returns to step 15 and the processes up to step 18 are repeated again.

In the example shown in FIG. 4, during the pressure monitoring time from time t ₄ to time t ₅ , the hydraulic oil pressure detected by the pressure sensor 20 reaches the upper limit determination value once or more, and once less than the lower limit determination value. did not become. Therefore, the processing from step 15 to step 18 is repeated again from time t ₅ to time t ₈ .

Since the between the pressure monitoring time from the time t ₇ to the time t _8, or the pressure of the working oil pressure sensor 20 has detected does not reach even once the upper threshold value, or equal to or less than the lower limit determination value even once, The process has moved to step 19.

  In step 19, the discharge capacity of the hydraulic pump 10 is increased to the maximum flow rate. In step 20, the discharge capacity of the hydraulic pump 10 is decreased so as to become a set value one step before when the pressure detected by the pressure sensor 20 falls below the determination value.

  As described above, the control unit 30 reduces the discharge capacity of the hydraulic pump 10 step by step, and determines that the pressure of the hydraulic oil supplied from the hydraulic pump 10 to the shaker 101 is lower than the determination value. The hydraulic pump 10 is adjusted to the discharge capacity of the previous stage when the value is lower. Therefore, the discharge capacity of the hydraulic pump 10 is set to the minimum necessary capacity. Therefore, energy saving of the hydraulic power source apparatus 100 can be achieved.

  Hereinafter, the process of step 19 and step 20 is demonstrated using a specific example.

  First, a specific example in the case where the hydraulic pump 10 includes the main pump 11 and the sub pump 12 will be described.

(Specific example 1)
For example, at the setting value 8 shown in FIG. 6, the main pump 11 operates with a discharge capacity of 100%, and the sub pump 12 operates with a discharge capacity of 30%. When the process proceeds to step 19 in this state, the discharge capacity of the sub pump 12 is increased to 100%. As a result, both the main pump 11 and the sub pump 12 are operated with a discharge capacity of 100%.

At this time, the control unit 30 transmits the operation signal to the tilting actuator 12b, proportionally increases the discharge capacity during the time t ₈ as shown in FIG. 4 to time t _9. Therefore, the discharge capacity of the sub pump 12 does not increase rapidly.

Then, after waiting for a pre-setting standby time between time t ₉ and time t ₁₀ , the process proceeds to step 20, and the flow rate of the hydraulic pump 10 is set so that the setting value 7 is set to be one stage before the setting value 8. Decrease. Specifically, the discharge capacity of the main pump 11 is kept at 100%, and the discharge capacity of the sub pump 12 is reduced to 40%.

Also at this time, the control unit 30 transmits the operation signal to the tilting actuator 12b, proportionally reducing the discharge capacity during the time t ₁₀ as shown in FIG. 4 to time t _11. Therefore, the discharge capacity of the sub pump 12 does not decrease rapidly.

  As described above, when it is determined that the hydraulic oil pressure detected by the pressure sensor 20 is lower than the determination value, the control unit 30 returns the discharge capacity of the hydraulic pump 10 to the initial maximum flow rate, and then determines Decrease to the previous discharge capacity below the value. Therefore, the discharge capacity of the hydraulic pump 10 can be accurately set to the set value without being affected by hysteresis.

(Specific example 2)
For example, at the set value 20 shown in FIG. 6, the main pump 11 operates at a discharge capacity of 50%, and the sub pump 12 stops operating. At this time, the operation of the electric motor 12a that rotationally drives the sub pump 12 is also stopped. When the process proceeds to step 19 in this state, only the discharge capacity of the main pump 11 is increased to 100% while the operation of the sub pump 12 is stopped.

Then, after waiting for the pre-setting standby time between time t ₉ and time t ₁₀ , the process proceeds to step 20, and the flow rate of the hydraulic pump 10 is set so that the setting value 19 that is one stage before the setting value 20 is set. Decrease. Specifically, the discharge capacity of the main pump 11 is reduced to 55% while the operation of the sub pump 12 is stopped.

  Thus, when setting to the set value in which the sub pump 12 is in a stopped state in step 20, only the discharge capacity of the main pump 11 is set to the set value without restarting the sub pump 12. This prevents the sub-pump 12 from being restarted even though it is scheduled to stop. Therefore, energy saving of the hydraulic power source apparatus 100 can be achieved.

  Next, a specific example when the hydraulic pump 10 includes only the main pump 11 will be described.

(Specific example 3)
For example, at the set value 15 shown in FIG. 7, the main pump 11 is operating at a discharge capacity of 38%. When the process proceeds to step 19 in this state, the discharge capacity of the main pump 11 is increased to 100%.

Then, after waiting for the pre-setting standby time between time t ₉ and time t ₁₀ , the process proceeds to step 20, and the flow rate of the main pump 11 is set so that the setting value 14 that is one stage before the setting value 15 is set. Decrease. Specifically, the discharge capacity of the main pump 11 is reduced to 41%.

  Even after the discharge capacity of the hydraulic pump 10 is set to the minimum necessary capacity as in the specific example described above, the control unit 30 always checks whether the pressure of the hydraulic oil detected by the pressure sensor 20 falls below the determination value. Keep monitoring.

  Then, when the control unit 30 receives a signal indicating that another shaker has started vibration or the pressure of the hydraulic oil detected by the pressure sensor 20 falls below a determination value, the control unit 30 discharges the hydraulic pump 10. After returning the capacity to the initial value, the discharge capacity of the hydraulic pump 10 is decreased stepwise to control the discharge flow rate. As a result, the flow rate of the hydraulic oil required when a vibrator different from the vibrator 101 is activated to use the hydraulic oil or when the setting of the vibrator 101 is changed. Is increased, the hydraulic fluid flow rate is prevented from being insufficient.

  At this time, even if the hydraulic pump 10 has the main pump 11 and the sub pump 12, even if the operation of the sub pump 12 is stopped, the sub pump 12 is restarted and the discharge capacity of the main pump 11 and the sub pump 12 is restored. Are set to 100%. Accordingly, it is possible to cope with a case where a large amount of hydraulic oil is required suddenly as in the case where a plurality of other vibrators are simultaneously operated.

  According to the above embodiment, the following effects are obtained.

  When the controller 30 gradually decreases the discharge capacity of the hydraulic pump 10 and determines that the pressure of the hydraulic oil supplied from the hydraulic pump 10 to the shaker 101 is lower than the determination value, the control unit 30 The hydraulic pump 10 is adjusted to the discharge capacity. This determination value is set to a minimum value at which the shaker can stably generate vibration. Therefore, the discharge capacity of the hydraulic pump 10 is set to the minimum necessary capacity. Therefore, energy saving of the hydraulic power source apparatus 100 can be achieved.

  In addition, when the control unit 30 determines that the hydraulic oil pressure detected by the pressure sensor 20 has fallen below the determination value, the control unit 30 returns the discharge capacity of the hydraulic pump 10 to the maximum flow rate that is the initial value, and then falls below the determination value. Reduce to the previous discharge capacity. Therefore, the discharge capacity of the hydraulic pump 10 can be accurately set without being affected by hysteresis.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 100 Hydraulic power source apparatus 101 Exciter 10 Hydraulic pump 11 Main pump 12 Sub pump 20 Pressure sensor (pressure detector)
30 Control unit

Claims (5)

A hydraulic power source device that supplies hydraulic oil to a vibration exciter that periodically generates vibration by supplying and discharging hydraulic oil,
A variable displacement hydraulic pump with adjustable hydraulic oil discharge capacity;
A pressure detector for detecting the pressure of hydraulic oil supplied from the hydraulic pump to the shaker;
A controller that adjusts the discharge capacity of the hydraulic pump based on the pressure of the hydraulic oil detected by the pressure detector,
The control unit reduces the discharge capacity of the hydraulic pump in a stepwise manner from an initial value, and the hydraulic oil pressure detected by the pressure detector is a minimum value at which the shaker can stably generate vibration. When it is determined that the determination value is lower than the determination value, the discharge capacity of the hydraulic pump is adjusted to the discharge capacity before the determination value is decreased.   When the control unit determines that the pressure of the hydraulic oil detected by the pressure detector is lower than the determination value, the control unit returns the discharge capacity of the hydraulic pump to the initial value, and is one step before the determination value. 2. The hydraulic power source device for a vibration exciter according to claim 1, wherein the hydraulic pressure source device is reduced to a discharge capacity of 2. The determination value has an upper limit determination value and a lower limit determination value set lower than the upper limit determination value,
When the pressure of the hydraulic fluid detected by the pressure detector does not reach the upper limit determination value within a predetermined period or when the pressure becomes equal to or lower than the lower limit determination value within the predetermined period, 3. The hydraulic power source device for a vibration exciter according to claim 1, wherein the hydraulic pressure detected by the pressure detector is determined to be lower than the determination value. 4.   The control unit determines whether or not the pressure detected by the pressure detector has fallen below the determination value after a predetermined standby time has elapsed since the discharge capacity of the hydraulic pump has been reduced by one step. The hydraulic power source apparatus for a vibration exciter according to any one of claims 1 to 3. The hydraulic pump supplies hydraulic oil to a plurality of shakers,
The control unit receives a signal indicating that another shaker has started to vibrate, or adjusts the discharge capacity before the value falls below the judgment value, and the pressure of the hydraulic oil detected by the pressure detector is the judgment. 5. The discharge capacity of the hydraulic pump is decreased stepwise again after returning the discharge capacity of the hydraulic pump to the initial value when the value is lower than the value. The hydraulic power source device of the vibrator according to 1.

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