JP6391299B2 - Inverter control hydraulic unit - Google Patents

Description

  The present invention relates to an inverter-controlled hydraulic unit that rotates and drives a variable displacement hydraulic pump with a motor and controls the flow rate and pressure of hydraulic oil discharged from the variable displacement hydraulic pump by controlling the number of rotations of the motor.

  This type of inverter-controlled hydraulic unit includes a variable displacement hydraulic pump having a pressure adjusting mechanism that mechanically controls the position of a swash plate as a variable discharge amount by hydraulic control based on discharge pressure, and the variable displacement hydraulic pump. A pressure sensor as pressure detection means for detecting the discharge pressure of the variable displacement hydraulic pump, and a controller for controlling the motor at a preset rotational speed corresponding to the pressure detected by the pressure sensor. The controller controls the number of revolutions according to the discharge pressure until it reaches the cutoff start pressure of the variable displacement hydraulic pump, and keeps the number of revolutions constant between the cutoff start pressure and the full cut pressure. By pressure control to reduce the displacement of the variable displacement hydraulic pump by mechanically adjusting the amount according to the discharge pressure, Thereby achieving energy savings by reducing the necessary torque of over data.

JP 2003-172302 A

  However, in such a conventional inverter-controlled hydraulic unit, when the discharge pressure drops below the cutoff start pressure from the state where it exceeds the cutoff start pressure, and repeats pressure fluctuations that rise above the cutoff start pressure again, The rotational speed fluctuates with the pressure fluctuation, and there has been a problem that hunting is generated by repeatedly increasing and decreasing the discharge amount of the pump.

  The subject of this invention is providing the inverter control hydraulic unit which suppresses the hunting of the pump by rotation speed fluctuation | variation.

In order to achieve this problem, the present invention has taken the following measures. That is,
A variable displacement hydraulic pump having a pressure adjustment mechanism that mechanically controls the position of a discharge variable variable element by hydraulic control based on the discharge pressure, a motor that rotationally drives the variable displacement hydraulic pump, and a discharge of the variable displacement hydraulic pump Pressure detecting means for detecting pressure and generating a pressure signal; and an inverter for receiving the pressure signal from the pressure detecting means and controlling the rotational speed of the motor in a variable manner. When the pump discharge pressure reaches the set pressure, the pressure switch emits a pressure signal. The inverter receives the pressure signal from the pressure switch and controls the motor rotation speed from high speed to low speed. between the pressure signal from the pressure switch which receives the inverter, a delay means for delaying a predetermined time after reaching the set pressure, set pressure cutoff Higher than the start pressure is the pressure below the full cut-off pressure, the delay means includes an inverter control, characterized in that setting the predetermined time to a pressure signal from the pressure switch inverter receives at the time of exceeding the full cut-off pressure That is the hydraulic unit.

  In this case, the delay means may set a predetermined time so that the inverter receives a pressure signal from the pressure switch when the full cut-off pressure is exceeded.

As described above in detail, in the invention described in claim 1, the pressure detecting means is a pressure switch that generates a pressure signal when the discharge pressure of the variable displacement hydraulic pump reaches a set pressure, and the inverter is connected to the pressure switch. The delay of delaying the pressure signal from the pressure switch received by the inverter for a predetermined time after reaching the set pressure between the pressure switch and the inverter. The set pressure is higher than the cut-off start pressure and lower than the full cut-off pressure, and the delay means takes a predetermined time so that the inverter receives a pressure signal from the pressure switch when the full cut-off pressure is exceeded. Set . Therefore, after reaching the set pressure, the discharge pressure decreases from the state where it exceeds the cutoff start pressure to below the cutoff start pressure and then repeats the pressure fluctuation that rises above the cutoff start pressure again. In the meantime, since the motor speed is maintained at a high speed, hunting associated with fluctuations in the motor speed can be suppressed.

Further, delay means sets the predetermined time to receive the inverter pressure signal from the pressure switch at the time of exceeding the full cut-off pressure. For this reason, the discharge pressure can be reliably increased to the full cut-off pressure, and a good pump operation can be obtained.

It is a circuit diagram of an inverter control hydraulic unit showing one embodiment of the present invention. The pump characteristics of FIG. 1 are shown, (A) is a characteristic diagram of discharge flow rate-discharge pressure, and (B) is a characteristic diagram of rotational speed-discharge pressure. The pump characteristics of FIG. 1 are shown, (A) is a rotation speed-time characteristic chart, (B) is a discharge pressure-time characteristic chart, and (C) is a discharge flow rate-time characteristic chart.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a variable displacement vane pump as a variable displacement hydraulic pump that supplies hydraulic oil to an actuator (not shown). The variable displacement vane pump 1 has a movable ring 2 as a discharge amount variable element in an eccentric manner. The pressure adjustment mechanism 3 is provided to reduce the discharge amount, and the discharge amount is reduced by reducing the eccentric amount of the movable ring 2. The pressure adjusting mechanism 3 of the variable displacement vane pump 1 operates to reduce the eccentric amount of the movable ring 2 when the discharge pressure of the variable displacement vane pump 1 reaches the cutoff start pressure indicated by P1 in FIG. The discharge amount is decreased from the maximum discharge amount Q1, and thereafter the eccentric amount of the movable ring 2 is decreased as the discharge pressure is increased to further reduce the discharge amount, and the full cut-off indicated by P2 in FIG. When the pressure is reached, the amount of eccentricity of the movable ring 2 disappears, and the discharge amount is made substantially zero of the minimum discharge amount Q2. The pressure adjustment mechanism 3 includes a spring 4 that sets the full cutoff pressure P2 based on the spring force, and the spring force of the spring 4 can be adjusted by the adjustment screw 4A so that the full cutoff pressure P2 can be changed. Yes. Note that the cutoff start pressure P1 is slightly lower than the full cutoff pressure P2.

  A motor 5 rotates the variable displacement vane pump 1 and is coupled to the variable displacement vane pump 1 by a coupling 6. Reference numeral 7 denotes a pressure switch as pressure detection means, which electrically detects the discharge pressure of the hydraulic oil discharged from the variable displacement vane pump 1, and outputs a pressure signal when the detected discharge pressure reaches a set pressure. An inverter 8 receives the pressure signal from the pressure switch 7 and controls the number of rotations of the motor 5 so as to be freely changeable. The inverter 8 outputs a control signal set based on the pressure signal from the pressure switch 7. 7A is a timer as a delay means for delaying a pressure signal from the pressure switch 7 received by the inverter 8 for a predetermined time after reaching the set pressure, and is built in the pressure switch 7 and provided between the pressure switch 7 and the inverter 8. Yes. The timer 7A sets a predetermined time so that the inverter 8 receives the pressure signal from the pressure switch 7 when the full cut-off pressure P2 is exceeded. Thereby, as shown in FIG. 2B, the inverter 8 outputs a control signal set at a high speed N1 until the discharge pressure reaches the full cut-off pressure P2, and the discharge pressure reaches the full cut-off pressure P2. The control signal set to the low-speed rotation speed N2 is output when the value exceeds.

  3 (A), (B), and (C) show the relationship between the rotational speed of the pump, the discharge pressure, and the discharge flow rate with respect to the passage of time. At the time T0 at the start of operation of the actuator, the variable displacement vane pump 1 It is rotationally driven at the rotation speed N1, and discharges the maximum discharge amount Q1. The discharge pressure at this time is P, which is a low pressure, and the discharge pressure of P is maintained until time T1 when the actuator reaches the operating end. The discharge pressure gradually increases from time T1 when the actuator reaches the operating end to time T2 when the actuator is in a pressurized state, and from time T3 when it reaches the cutoff start pressure P1, the discharge flow rate gradually decreases and the full cutoff pressure P2 is reached. At the time T2 when the pressure reaches, the discharge flow rate is set to the minimum discharge amount Q2, which is substantially zero. The set pressure P3 of the pressure switch 7 is higher than the cutoff start pressure P1 and lower than the full cutoff pressure P2. The predetermined time “a” of the timer 7A starts from the time T5 of the set pressure P3, and is the time T4 when the pressure is increased to the full cut-off pressure P2, and the rotational speed is changed from the high speed N1 to the low speed N2. It is set to decrease. When returning from the pressurized state to the operating state, the discharge pressure gradually decreases from the full cut-off pressure P2, and the rotation speed is changed from the low speed N2 to the high speed from time T6 to T7 when the discharge pressure becomes the set pressure P3. The number rises to a number N1, and then returns to the operation at the start of actuator operation.

Next, the operation of this configuration will be described.
When the variable displacement vane pump 1 is driven to rotate at a high speed N1 by the motor 5 at the start of operation of the actuator, the variable displacement vane pump 1 operates at the maximum discharge amount Q1 with the movable ring 2 having the maximum eccentricity. Inhale and discharge oil.

  When the actuator reaches the operating end, the discharge pressure of the variable displacement vane pump 1 increases from the cutoff start pressure P1 to the full cutoff pressure P2. Then, during the time T3 of the cut-off start pressure P1 to the time T2 of the full cut-off pressure P2, the pressure adjusting mechanism 3 operates so as to reduce the eccentric amount of the movable ring 2 to reduce the discharge amount. When the amount of eccentricity disappears, the discharge amount is set to approximately zero of the minimum discharge amount Q2.

  When the actuator reaches the operating end and the discharge pressure reaches the set pressure P3 of the pressure switch 7, the timer 7A starts to elapse and maintains the rotational speed at a high rotational speed N1 for a predetermined time a. Then, after the lapse of the predetermined time a, the inverter 8 receives the pressure signal output from the pressure switch 7, and the inverter 8 reduces the rotational speed of the motor 5 from the high speed rotational speed N1 to the low speed rotational speed N2. Stop operation.

  When returning from the operating end of the actuator to the operation start position, the discharge pressure gradually decreases from the full cut-off pressure P2 with the operation of the actuator, and the pressure switch 7 to the inverter 8 at time T6 when the discharge pressure becomes the set pressure P3. Is stopped, and the inverter 8 increases the rotational speed from the low rotational speed N2 to the high rotational speed N1, and thereafter returns to the operation at the start of the actuator operation.

  With this operation, the pressure detecting means is the pressure switch 7 that generates a pressure signal when the discharge pressure of the variable displacement vane pump 1 reaches the set pressure P3, and the inverter 8 receives the pressure signal from the pressure switch 7 and receives the motor 5 Is controlled from a high speed N1 to a low speed N2, and a pressure signal from the pressure switch 7 received by the inverter 8 is set between the pressure switch and the inverter after reaching the set pressure P3. A timer 7A for delaying during time a is provided. For this reason, after reaching the set pressure P3, the discharge pressure decreases from the state in which it exceeds the cut-off start pressure P1 to the cut-off start pressure P1 or less, and then repeats pressure fluctuations that rise above the cut-off start pressure P1 again. However, since the rotation speed of the motor 5 is maintained at a high speed for a predetermined time a, hunting associated with fluctuations in the rotation speed of the motor 5 can be suppressed.

Further, the timer 7A is a delay means, to set the predetermined time a to the pressure signal from the pressure switch 7 at the time of exceeding the full cut-off pressure P2 inverter 8 receives. For this reason, the discharge pressure can be reliably increased to the full cut-off pressure P2, and a good pump operation can be obtained.

  In one embodiment, an electric pressure switch 7 is used that detects the discharge pressure of the hydraulic oil discharged from the variable displacement vane pump 1 and outputs a pressure signal when the detected discharge pressure reaches the set pressure P3. However, a mechanical pressure switch that outputs a pressure signal when the set pressure P3 is reached may be used by using a spring or the like that sets the pressure. Further, although the variable displacement hydraulic pump is the variable displacement vane pump 1, a variable displacement piston pump may be used. Although the timer 7A is built in the pressure switch 7, it is a matter of course that the timer 7A may be built in the inverter 8, or the timer 7A may be provided separately between the pressure switch 7 and the inverter 8.

1: Variable displacement vane pump (variable displacement hydraulic pump)
2: Moveable ring (Discharge rate variable element)
3: Pressure adjustment mechanism 5: Motor 7: Pressure switch (pressure detection means)
7A: Timer (delay means)
8: Inverter a: Predetermined time

Claims (1)

A variable displacement hydraulic pump having a pressure adjustment mechanism that mechanically controls the position of a discharge variable variable element by hydraulic control based on the discharge pressure, a motor that rotationally drives the variable displacement hydraulic pump, and a discharge of the variable displacement hydraulic pump Pressure detecting means for detecting pressure and generating a pressure signal; and an inverter for receiving the pressure signal from the pressure detecting means and controlling the rotational speed of the motor in a variable manner. When the pump discharge pressure reaches the set pressure, the pressure switch emits a pressure signal. The inverter receives the pressure signal from the pressure switch and controls the motor rotation speed from high speed to low speed. between the pressure signal from the pressure switch which receives the inverter, a delay means for delaying a predetermined time after reaching the set pressure, set pressure cutoff Higher than the start pressure is the pressure below the full cut-off pressure, the delay means includes an inverter control, characterized in that setting the predetermined time to a pressure signal from the pressure switch inverter receives at the time of exceeding the full cut-off pressure hydraulic unit.

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