JP2019210849A - Inverter drive hydraulic unit - Google Patents

Abstract

To provide an inverter drive hydraulic unit capable of making an inverter device control a variable speed motor so as to be operated at a prescribed low speed rotation by easily detecting a full-cut-off state of a variable displacement hydraulic pump in a simple configuration not requiring a pressure sensor and an exclusive control.SOLUTION: An inverter drive hydraulic unit includes: a variable displacement hydraulic pump having a pressure adjustment mechanism for mechanically controlling a position of a discharge variable element by hydraulic control based on a discharged pressure; a variable speed motor for driving the variable displacement-side hydraulic pump; and an inverter device for switchably driving and controlling the variable speed motor at multistage speed rotational frequencies including low speed rotation corresponding to full-cut-off of the predetermined variable displacement type hydraulic pump. The inverter drive hydraulic unit also includes drainage amount detection means for monitoring a drainage amount from the variable displacement-type hydraulic pump, detecting the drain amount corresponding to the full-cut-off state of the predetermined variable displacement type hydraulic pump, and outputting the detection signal to the inverter device as a rotational frequency command signal at the low speed.]SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inverter-driven hydraulic unit that controls the discharge flow rate and discharge pressure of a variable displacement hydraulic pump in a full cut-off state, and more specifically, the rotational speed of a variable-speed motor with a simpler configuration than that of the prior art. It relates to what can control.

  For a variable displacement hydraulic pump having a pressure adjustment mechanism that mechanically controls the position of a discharge amount variable element by hydraulic control based on discharge pressure, the rotational speed of a variable speed motor that drives the pump is controlled by an inverter device. There is an inverter drive hydraulic unit that controls the discharge flow rate and discharge pressure of the pump with energy saving (see, for example, Patent Document 1 and Patent Document 2).

  In the inverter drive control in such a hydraulic unit, for example, as shown in FIG. 4, the discharge pressure of a variable displacement hydraulic pump 102 such as a swash plate type piston pump is detected by a pressure sensor 105, and the detected pressure is set in advance. Based on the rotation speed condition, the controller 106 creates the rotation speed command signal 107 of the variable speed motor 103 and instructs the inverter device 104 to control the rotation speed of the variable speed motor 103.

  Therefore, when the discharge pressure becomes equal to or higher than the cutoff start pressure of the variable displacement hydraulic pump, the discharge amount variable element 111 is mechanically displaced by the pressure control system by the pressure adjustment mechanism 110 to a position where the capacity is reduced and discharged. Although the pressure and discharge flow rate are controlled, in the full cut-off state, the rotation speed of the variable speed motor is set based on a preset low speed rotation speed condition capable of stably maintaining the discharge pressure by the inverter drive control. Is controlled. As described above, the low-speed rotation operation in the full cut-off state significantly reduces wasteful power consumption and enables energy-saving operation with low heat generation.

JP 2002-172302 A Japanese Patent No. 5023852

  However, in the prior art, as described above, the mechanical control by the pressure control system in the full cut-off state of the variable displacement hydraulic pump, for example, the tilt angle control of the swash plate in the swash plate type piston pump, is performed to reduce the full cut-off pressure. In order to control the rotation of the variable speed motor at a low speed that can be stably maintained, a pressure sensor and a dedicated controller are necessary, and the cost is increased accordingly.

  In addition, since the controller's full cut-off pressure must be set to the pressure set by the mechanical pressure setter attached to the variable displacement hydraulic pump, this is a very laborious work.

  In view of the above problems, an object of the present invention is to easily detect the full cut-off state of a variable displacement hydraulic pump, while having a simple configuration without requiring a pressure sensor and dedicated control. An object of the present invention is to provide an inverter-driven hydraulic unit capable of controlling a transmission motor at a predetermined low-speed rotation.

In order to achieve the above object, an inverter-driven hydraulic unit according to the first aspect of the present invention has a variable displacement hydraulic pressure having a pressure adjusting mechanism that mechanically controls the position of a discharge amount variable element by hydraulic control based on discharge pressure. A pump,
A variable speed motor for driving the variable displacement hydraulic pump;
An inverter device that drives and controls the variable speed motor so that the variable speed hydraulic pump can be switched at a multistage speed including a predetermined low speed rotation corresponding to a full cut-off of the variable displacement hydraulic pump;
The drain amount from the variable displacement hydraulic pump is monitored, the drain amount corresponding to a predetermined full cutoff state of the variable displacement hydraulic pump is detected, and the detection signal is used as the rotation speed command signal at the low speed. As a drain amount detecting means for outputting to the inverter device.

  The inverter-driven hydraulic unit according to the invention of claim 2 is the inverter-driven hydraulic unit of claim 1, wherein the drain amount detecting means detects a preset flow rate and outputs an ON signal, The flow rate switch is characterized in that the signal is turned off when the flow rate is smaller than the set value.

  According to the present invention, by utilizing the pump characteristic that the drain amount increases when the variable displacement hydraulic pump reaches the full cut-off pressure, the drain amount detecting means does not use the pressure sensor and the dedicated controller, but the full cut is performed. A variable displacement hydraulic pump with an inverter-driven hydraulic unit is possible because it can control the inverter device as a rotational speed command signal with a detection signal that detects the drain amount corresponding to the OFF state, and switch the motor to low-speed rotational operation. Energy saving operation by low-speed rotation operation of the motor in the full cut-off state can be realized at a low cost with a greatly simplified configuration compared to the conventional, and a very simple operation that does not require complicated labor of controller setting. There is an effect of becoming.

It is a block diagram which shows schematic structure of the inverter drive hydraulic unit by one Example of this invention. It is a diagram which shows the relationship of the drain amount with respect to the pressure which shows the characteristic of a variable displacement hydraulic pump. It is a diagram which shows the operation state at the time of performing rotation speed control of the motor by the inverter drive hydraulic unit of FIG. 1 using the flow switch as a drain amount detection means. It is a block diagram which shows schematic structure of the conventional inverter drive hydraulic unit.

  In the inverter-driven hydraulic unit of the present invention, a variable displacement hydraulic pump having a pressure adjusting mechanism that mechanically controls the position of the discharge variable variable element by hydraulic control based on the discharge pressure, and the variable displacement hydraulic pump are driven. A variable speed motor, and an inverter device that drives and controls the variable speed motor to be switchable at a multistage speed including a predetermined low speed rotation corresponding to a full cut-off of the variable displacement hydraulic pump. The drain amount from the variable displacement hydraulic pump is monitored, the drain amount corresponding to a predetermined full cutoff state of the variable displacement hydraulic pump is detected, and the detection signal is used as the rotation speed command signal at the low speed. A drain amount detecting means for outputting to the inverter device is provided.

  The present invention has been conceived by paying attention to the pump characteristic that the drain amount increases when the discharge pressure of the variable displacement hydraulic pump reaches the full cutoff pressure. That is, in the above configuration, the drain amount detecting means detects the drain amount corresponding to the predetermined full cutoff state of the variable displacement hydraulic pump, and uses this detection signal as the rotation speed command signal to the inverter device. To do.

  Therefore, according to the present invention, there is no need to provide a pressure sensor for detecting the full cutoff state and a dedicated controller for outputting a rotation speed command signal to the inverter device based on the pressure detection result from the pressure sensor, The inverter device can be driven to control the variable speed motor so that a predetermined low speed rotation corresponding to when the variable displacement hydraulic pump reaches the full cut-off pressure.

  For this reason, excellent energy-saving operation by low-speed rotation operation of the motor in the full cut-off state of the variable displacement hydraulic pump by the inverter-driven hydraulic unit is realized at a low cost with a greatly simplified configuration compared to the conventional one, and a pressure sensor or Not only the wiring process for the dedicated controller but also the complicated work of setting the pressure of the controller is not necessary, and it can be realized by a very simple work.

  As an inverter device, a multi-speed capable of controlling the number of rotations in at least two types of a low-speed rotation operation corresponding to a full cut-off state and a high-speed rotation operation below a full cut-off pressure for a variable speed motor. (Multistage frequency) Set type.

  Various drain amount detecting means can be used as long as the drain flow rate preset as the drain amount corresponding to the full cut-off state can be detected, but the configuration is as simple as possible and the cost is low. Is desirable. Therefore, it is convenient and preferable to use a flow switch. The flow rate switch detects a preset flow rate and outputs an ON signal. When the flow rate becomes smaller than the set value, the signal is turned OFF. In the present invention, the drain amount corresponding to the full cutoff state should be detected. For the inverter device, the ON signal may be set as a low speed rotational speed command signal, and the signal OFF may be set corresponding to the high speed rotational speed command signal.

  Accordingly, when the inverter device receives the ON signal from the flow rate switch, it can control to switch to the operation at the preset low-speed rotation speed for the full cut-off for the motor. Also, if the discharge pressure of the variable displacement hydraulic pump decreases from the full cut-off pressure, the drain amount decreases and the ON signal from the flow switch turns OFF, and the inverter device goes to high-speed rotation operation with respect to the motor. Switching control is performed.

  An inverter-driven hydraulic unit according to an embodiment of the present invention is shown in the block diagram of FIG. In this embodiment, the variable displacement hydraulic pump is a swash plate type piston pump. That is, the inverter driven hydraulic unit 1 mechanically adjusts the inclination angle against the spring 12 of the swash plate 11 that is a variable discharge amount by hydraulic control based on the discharge pressure of the variable displacement hydraulic pump 2 that is a swash plate type piston pump. The pressure adjustment mechanism 10 is controlled to the above. A variable speed motor 3 that rotationally drives the variable displacement hydraulic pump 2 and an inverter device 4 that controls the rotational speed of the variable speed motor 3 are provided.

  In this embodiment, the flow rate switch 5 as the drain amount detecting means is provided in the drain flow path to the tank, and ON / OFF of the flow rate setting contact signal output from the flow rate switch 5 is rotated to the inverter device 4. The number command signal 6 is input.

  Here, the characteristic that the drain amount increases when the discharge pressure found in the variable displacement hydraulic pump 2 reaches the full cutoff pressure is shown in the diagram of FIG. FIG. 2 shows an example of two set full cut-off pressures of 10 MPa and 21 MPa, and the drain amount (vertical axis: flow rate [L / L], which changes according to the pressure increase (horizontal axis: pressure [MPa]), respectively). min]) is plotted.

  As shown in FIG. 2, it can be seen that in any setting, when the drain amount that does not reach 2 L / min below the full cut-off pressure reaches the full cut-off pressure, it rapidly increases to 8 L / min. Therefore, by monitoring the drain amount of the variable displacement hydraulic pump and detecting such a large drain amount, the full cutoff state can be recognized without detecting the pressure by the pressure sensor, and the inverter device 4 A low-speed rotation command can be sent to

  In this embodiment, the set full cut-off pressure of the variable displacement hydraulic pump 2 is set to 7 MPa, the number of rotations of the motor is set to 450 rpm during the low-speed rotation operation, and 1800 rpm during the high-speed rotation operation. Based on the characteristics shown in FIG. 2, the number of revolutions of the motor 3 was controlled at 8 L / min. The operation state in this control process is shown in the diagram of FIG. The flow switch 5 is a simple and compact piston type linear flow path type.

  FIG. 3 shows changes in discharge pressure (vertical axis: pressure [MPa], motor rotation speed [rpm]) according to the passage of time (horizontal axis: time [sec]) in driving the variable displacement hydraulic pump 2. It is a thing. As can be seen from FIG. 3, when the motor rotation speed that was operating at a high speed under the full cut-off pressure reaches the full cut-off pressure and the ON signal is output from the flow switch 5, the motor speed is immediately switched to the low speed rotation speed. Set full cut-off pressure is maintained. When the discharge pressure is reduced and the signal from the flow switch 5 is turned off, the motor speed is immediately switched to the high speed.

  As described above, in the inverter driven hydraulic unit 1 of the present embodiment, the drain amount of the variable displacement hydraulic pump 2 is monitored without a pressure sensor or a dedicated controller, and the drain amount corresponding to the full cut-off state is monitored. It is possible to satisfactorily switch and control the motor rotation speed between the low-speed rotation operation and the high-speed rotation operation only by detecting the presence or absence.

DESCRIPTION OF SYMBOLS 1,101: Inverter drive hydraulic unit 2, 102: Variable displacement type hydraulic pump 3, 103: Variable speed motor 4, 104: Inverter device 5: Flow rate switch 6, 107: Revolution command signal 10, 110: Pressure adjustment mechanism 11 111: Discharge amount variable element (swash plate)
12, 112: Spring 105: Pressure sensor 106: Controller

In order to achieve the above object, an inverter-driven hydraulic unit according to the first aspect of the present invention has a variable displacement hydraulic pressure having a pressure adjusting mechanism that mechanically controls the position of a discharge amount variable element by hydraulic control based on discharge pressure. A pump,
A variable speed motor for driving the variable displacement hydraulic pump;
An inverter device that drives and controls the variable speed motor so that the variable speed hydraulic pump can be switched at a multistage speed including a predetermined low speed rotation corresponding to a full cut-off of the variable displacement hydraulic pump;
The drain amount from the variable displacement hydraulic pump is monitored, the drain amount corresponding to a predetermined full cutoff state of the variable displacement hydraulic pump is detected, and the detection signal is used as the rotation speed command signal at the low speed. As a drain amount detecting means for outputting to the inverter device ,
The drain amount detection means is a flow rate switch that detects a drain amount corresponding to the preset full cut-off state and outputs an ON signal, and the signal is turned OFF when the flow rate is smaller than a set value. It is what.

Claims (2)

A variable displacement hydraulic pump having a pressure adjustment mechanism that mechanically controls the position of the discharge amount variable element by hydraulic control based on the discharge pressure;
A variable speed motor for driving the variable displacement hydraulic pump;
An inverter device that drives and controls the variable-speed motor so that the variable-speed motor can be switched at a multistage speed including a low-speed rotation corresponding to a full cutoff of the variable displacement hydraulic pump,
The drain amount from the variable displacement hydraulic pump is monitored, the drain amount corresponding to a predetermined full cut-off state of the variable displacement hydraulic pump is detected, and the detection signal is used as the rotational speed command signal at the low speed. An inverter drive hydraulic unit comprising a drain amount detecting means for outputting to the inverter device.   2. The inverter according to claim 1, wherein the drain amount detection means is a flow rate switch that detects a preset flow rate and outputs an ON signal, and the signal is turned OFF when the flow rate is smaller than the set value. Drive hydraulic unit.

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