JP2010255780A - Hydraulic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a hydraulic device which allows a flow rate discharged from a hydraulic pump to be substantially constant regardless of a difference in temperature of a working fluid stored in a tank. <P>SOLUTION: The hydraulic device is provided with a tank 10 which stores the working fluid, the hydraulic pump 1 which sucks the working fluid in the tank 10 and then discharges it, an electric motor 6 which rotatably drives the hydraulic pump 1, a control circuit 50 which controls the number of rotations of the electric motor 6 and the first temperature sensor 14 which detects the temperature of the working fluid stored in the tank 10. As the temperature of the working fluid detected by the temperature sensor 14 lowers, the control circuit 50 exerts control to increase the number of rotations of the electric motor 6. Furthermore, the hydraulic device includes the second temperature sensor 16 which detects the temperature of the hydraulic pump 1 and the control circuit 50 stops the rotation of the electric motor 6 when the temperature detected by the second temperature sensor 16 reaches or exceeds the setting temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic apparatus that drives a hydraulic pump by an electric motor and pressurizes and discharges hydraulic oil sucked from a tank by the hydraulic pump.

  Conventionally, as disclosed in Patent Document 1, a hydraulic pump that sucks and discharges hydraulic oil stored in a tank and an electric motor that rotationally drives the hydraulic pump are provided, and the hydraulic oil discharged from the hydraulic pump is used as an actuator. Supply and drive the actuator. In addition, hydraulic oil from the actuator is returned to the tank.

JP 2008-39021 A

  However, in such a conventional hydraulic apparatus, when the temperature of the hydraulic oil stored in the tank is different, the viscosity changes with the difference in the temperature of the hydraulic oil, and thus the discharge flow rate from the hydraulic pump varies. That is, when the viscosity is high, the amount of hydraulic oil sucked into the hydraulic pump decreases, and the discharge flow rate also decreases. For example, the temperature of hydraulic oil stored in the tank differs between winter and summer, or after driving for a certain period of time, and the viscosity changes with the difference in hydraulic oil temperature. There is a problem that the discharge flow rate from the pump fluctuates and the cycle time fluctuates in winter and summer.

  The subject of this invention is providing the hydraulic apparatus which can make the discharge flow volume from a hydraulic pump substantially constant irrespective of the difference in the temperature of the hydraulic fluid stored in a tank.

In order to achieve this problem, the present invention has taken the following measures in order to solve the problem. That is,
A tank for storing hydraulic oil;
A hydraulic pump for sucking and discharging the hydraulic oil in the tank;
An electric motor for rotationally driving the hydraulic pump;
A control circuit for controlling the rotational speed of the electric motor;
A temperature sensor for detecting the temperature of the hydraulic oil stored in the tank;
The control circuit controls the rotational speed of the electric motor to be higher as the temperature of the hydraulic oil detected by the temperature sensor is lower.

  In addition, a second temperature sensor for detecting the temperature of the hydraulic pump is provided, and the control circuit stops the rotation of the electric motor when the temperature detected by the second temperature sensor exceeds a set temperature. Also good. Furthermore, it is good also as a structure using the numerical control circuit of a machine tool for the said control circuit.

The hydraulic device of the present invention has an effect that the discharge flow rate from the hydraulic pump can be made substantially constant regardless of the difference in temperature of the hydraulic oil stored in the tank.
Further, by providing the second temperature sensor and stopping the driving of the electric motor when the temperature becomes equal to or higher than the set temperature, it is possible to prevent seizure of the hydraulic pump and the like. Furthermore, it can be configured more easily by using a numerical control circuit of a machine tool as the control circuit.

It is a block diagram of the hydraulic apparatus as one Embodiment of this invention. It is a graph which shows the relationship between the discharge flow rate and discharge pressure of the variable displacement hydraulic pump with pressure compensation of this embodiment. It is a graph which shows the relationship between the temperature of the hydraulic fluid in this embodiment, and the rotation speed of an electric motor. It is a block diagram of the hydraulic apparatus as 2nd Embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, reference numeral 1 denotes a variable displacement hydraulic pump with pressure compensation, and a variable displacement hydraulic pump 1 with pressure compensation has a built-in pressure compensation mechanism 2. The variable displacement hydraulic pump 1 with pressure compensation is a so-called swash plate type variable displacement hydraulic pump that can change the discharge flow rate by changing the inclination angle of the swash plate, or the discharge flow rate by moving the cam ring position. A variable displacement vane pump that can vary the pressure is used.

  The pressure compensation mechanism 2 controls the inclination angle of the swash plate and the position of the cam ring when the discharge pressure of the variable displacement hydraulic pump 1 with pressure compensation reaches a cutoff pressure set according to the biasing force of the spring 4. The discharge flow rate is mechanically controlled.

  When the variable displacement hydraulic pump 1 with pressure compensation is driven at a constant rotational speed, as shown in FIG. 2, the hydraulic fluid is discharged at a maximum discharge flow rate QMAX corresponding to the rotational speed. The biasing force of the spring 4 can be changed by an adjusting screw (not shown), and the full cut-off pressure P3 is set by the adjusting screw, and the discharge pressure of the variable displacement hydraulic pump 1 with pressure compensation reaches the cut-off start pressure P2. Then, when the discharge flow rate decreases and the discharge pressure reaches the full cut-off pressure P3, the discharge flow rate becomes the minimum discharge flow rate Q0 which is almost zero. The variable displacement hydraulic pump 1 with pressure compensation is not limited to a constant displacement hydraulic pump.

  The variable displacement hydraulic pump 1 with pressure compensation is connected so as to be driven to rotate by an electric motor 6. The electric motor 6 is a motor having a variable number of rotations such as a servo motor. An encoder 8 for detecting the number is attached.

  The variable displacement hydraulic pump 1 with pressure compensation draws hydraulic oil from the tank 10 and discharges the pressurized hydraulic oil to the discharge passage 12. The discharge passage 12 is connected to an actuator such as a hydraulic cylinder via a directional control valve (not shown), and hydraulic oil is returned from the actuator to the tank 10 via a return passage (not shown).

  A first temperature sensor 14 for detecting the temperature of the hydraulic oil stored in the tank 10 is provided, and a second temperature sensor 16 for detecting the temperature of the variable displacement hydraulic pump 1 with pressure compensation is provided. The first temperature sensor 14 detects the temperature of the hydraulic oil in the tank 10, and the second temperature sensor 16 detects the temperature of a casing or a bearing portion (not shown) of the variable displacement hydraulic pump 1 with pressure compensation. A detection signal corresponding to the signal is output. Further, a pressure sensor 18 for detecting the pressure of the hydraulic oil in the discharge flow path 12 is provided, and the pressure sensor 18 outputs a detection signal corresponding to the hydraulic oil pressure in the discharge flow path 12.

  Detection signals from the first temperature sensor 14, the second temperature sensor 16, and the pressure sensor 18 are connected to be input to the controller 52 of the control circuit 50, and the rotation speed detection signal from the encoder 8 is connected to the control circuit 50. The servo amplifier 54 is connected so as to be input.

  The controller 52 outputs a rotation speed signal of the electric motor 6 corresponding to the temperature detected by the first temperature sensor 14 to the servo amplifier 54, and the servo amplifier 54 receives the input rotation according to the input rotation speed signal. The rotation of the electric motor 6 is controlled so as to be a number.

  The controller 52 outputs a rotation speed signal so that the rotation speed of the electric motor 6 increases as the temperature of the hydraulic oil decreases. In the present embodiment, as shown in FIG. 3, the relationship between the temperature of the hydraulic oil and the rotational speed of the electric motor 6 is set in advance, and when the hydraulic oil temperature is lower than the temperature T1, the rotational speed is the highest. The rotation speed is set to N4, and when the temperature of the hydraulic oil is between the temperature T1 and lower than the temperature T2, the rotation speed is set to a rotation speed N3 lower than the rotation speed N1.

  Further, when the temperature of the hydraulic oil is between the temperature T2 and lower than the temperature T3, the rotation speed N2 is further set to be low. When the temperature of the hydraulic oil is higher than the temperature T3 and lower than the temperature T4, the lowest rotation speed is set. The rotation speed is set to N1. Thus, it sets so that the rotation speed of the electric motor 6 may be switched in steps with respect to the temperature of hydraulic fluid. In addition, when the temperature of hydraulic oil is more than temperature T4, it sets so that the drive of the electric motor 6 may be stopped.

  Further, the controller 52 outputs a stop signal for stopping the driving of the electric motor 6 to the servo amplifier 54 when the temperature detected by the second temperature sensor 16 becomes equal to or higher than a preset temperature. The preset temperature is a temperature at which the variable displacement hydraulic pump 1 with pressure compensation becomes high and an abnormality due to seizure or the like may occur, and may be determined by experiments or the like.

  Furthermore, the controller 52 outputs a signal to the servo amplifier 54 so that the rotation speed is set to a low rotation speed when the hydraulic oil pressure detected by the pressure sensor 18 is equal to or higher than a preset pressure. . This preset pressure may be a pressure lower than the full cutoff pressure P3 of the variable displacement hydraulic pump 1 with pressure compensation and a pressure near the cutoff start pressure P2.

  Further, the preset number of rotations of low rotation is the number of rotations of the variable displacement hydraulic pump 1 with pressure compensation corresponding to the discharge flow rate that can compensate for the leakage amount of hydraulic oil from a directional control valve or actuator (not shown). And it is sufficient. When the discharge pressure from the variable displacement hydraulic pump 1 with pressure compensation is controlled from the cutoff start pressure P2 to the full cutoff pressure P3 by the pressure compensation mechanism 2, the variable displacement hydraulic pump 1 with pressure compensation The discharge flow rate is greatly reduced. At that time, if the rotation speed is such that a discharge flow rate that can compensate for the leak amount is secured, the pressure of the discharge flow path 12 does not decrease, and the rotation speed at that time may be determined in advance by experiments or the like.

Next, the operation of the hydraulic device of the present embodiment described above will be described.
At the time of start-up, the electric motor 6 is driven, the variable displacement hydraulic pump 1 with pressure compensation sucks the hydraulic oil stored in the tank 10, and the hydraulic oil is pressurized from the variable displacement hydraulic pump 1 with pressure compensation. And discharged to the discharge flow path 12.

  The temperature of the hydraulic oil stored in the tank 10 is detected by the first temperature sensor 14, and the temperature of the hydraulic oil is input to the controller 52. The controller 52 sets the rotation speed of the electric motor 6 according to the temperature of the hydraulic oil detected by the first temperature sensor 14.

  For example, when the ambient temperature is very low and the temperature of the hydraulic oil detected by the first temperature sensor 14 is lower than the very low temperature T1, such as at the start in winter, the controller 52 causes the servo amplifier 54 to be high. The rotation speed N4 is set. The servo amplifier 54 controls the electric motor 6 to rotate at the rotation speed N4.

  By rotating the electric motor 6 at a high rotational speed N4, the variable displacement hydraulic pump 1 with pressure compensation also rotates at the rotational speed N4. The decrease in the amount of suction and discharge flow per rotation due to the low temperature and high viscosity of the hydraulic oil is compensated by the increase in the number of rotations. Even when the hydraulic oil temperature is low, the variable displacement hydraulic pump 1 with pressure compensation is used. For example, the discharge flow rate is approximately the maximum discharge flow rate QMAX.

  The hydraulic fluid detected by the first temperature sensor 14 when the variable displacement hydraulic pump 1 with pressure compensation is driven to rotate for a while or when the ambient temperature is relatively high as in summer. When the temperature is between the slightly higher temperature T1 and lower than the temperature T2, the controller 52 sets the servo amplifier 54 to a slightly lower rotational speed N3.

  The viscosity changes according to the temperature of the hydraulic oil. When the temperature is slightly high, the variable displacement hydraulic pump with pressure compensation 1 is rotationally driven at a slightly low rotational speed N3. As a result, the rotational speed is reduced more than when the rotational speed N4 is high, and an increase in the discharge flow rate due to a decrease in viscosity is suppressed. Even if the viscosity decreases, for example, the maximum discharge flow rate QMAX is set.

  When the variable displacement hydraulic pump 1 with pressure compensation is rotationally driven, the temperature of the hydraulic oil rises as time elapses. Even when the summer is very hot, the temperature of the hydraulic oil is relatively high from the start. When the temperature of the hydraulic oil detected by the first temperature sensor 14 is further between the temperature T2 and the temperature T3, the controller 52 sets the low speed N2 in the servo amplifier 54. Further, when the temperature of the hydraulic oil is between the temperature T3 and lower than the temperature T4, the lowest rotation speed N1 is set.

  As a result, the servo amplifier 54 controls the electric motor 6 to rotate at the set rotational speeds N2 and N1, and the pressure-compensated variable displacement hydraulic pump 1 also rotates at the rotational speeds N2 and N1. Even if the viscosity is reduced by suppressing the increase in the discharge flow rate due to the decrease in viscosity due to the temperature rise of the hydraulic oil, the discharge flow rate from the variable displacement hydraulic pump 1 with pressure compensation is, for example, approximately the maximum discharge flow rate QMAX. And

  Thus, by controlling the rotation of the variable displacement hydraulic pump 1 with pressure compensation in accordance with the temperature of the hydraulic oil in the tank 10, fluctuations in the discharge flow rate due to changes in viscosity can be suppressed. Regardless of the temperature, the discharge flow rate can be made substantially constant. Therefore, the discharge flow rate of the variable displacement hydraulic pump 1 with pressure compensation is almost the same regardless of whether it is in winter or summer, or whether it is at the beginning of the start or the time has elapsed since driving. Can be constant.

  On the other hand, when the temperature of the hydraulic oil detected by the first temperature sensor 14 is equal to or higher than the temperature T4, the driving of the electric motor 6 is stopped. This prevents an oil seal (not shown) of the variable displacement hydraulic pump 1 with pressure compensation from being deteriorated by the high temperature of the hydraulic oil.

  Further, when operating the variable displacement hydraulic pump 1 with pressure compensation, when the temperature detected by the second temperature sensor 16 is equal to or higher than a preset temperature, the servo amplifier 54 is electrically operated. A stop signal for stopping the driving of the motor 6 is output. As a result, the variable displacement hydraulic pump 1 with pressure compensation is prevented from becoming abnormal due to seizure or the like due to high temperature.

  Even when the temperature detected by the second temperature sensor 16 is equal to or higher than a preset temperature, the temperature of the first temperature sensor 14 is not always higher than the temperature T4, and the first temperature sensor 14 and the second temperature are not limited. By detecting the temperature with the sensor 16, it is possible to reliably prevent the abnormality of the variable displacement hydraulic pump 1 with pressure compensation.

  Further, when the hydraulic oil pressure of the discharge flow path 12 detected by the pressure sensor 18 becomes equal to or higher than a preset pressure, the controller 52 is set to a low rotation speed preset in the servo amplifier 54. Output a signal. As a result, the variable displacement hydraulic pump 1 with pressure compensation is driven at a low rotational speed.

  When the hydraulic oil pressure in the discharge passage 12 increases and reaches the full cut-off pressure P3 from the cut-off start pressure P2, the discharge flow rate of the variable displacement hydraulic pump 1 with pressure compensation compensates for the leak amount by the pressure compensation mechanism 2. The degree is sufficient. Even if the variable displacement hydraulic pump 1 with pressure compensation is driven at a low rotational speed, the discharge flow rate can be maintained, and by reducing the rotational speed, energy saving and increase in the temperature of hydraulic oil can be suppressed. .

Next, a second embodiment different from the above-described embodiment will be described with reference to FIG. The same members as those in the embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.
In the second embodiment, a numerical control circuit 60 of a machine tool is used as the control circuit 50 of the above-described embodiment. The numerical control circuit 60 includes a controller 62, a servo amplifier 64 that controls the X axis, a servo amplifier 66 that controls the Y axis, and a servo amplifier 68 that controls the Z axis. The controller 62 is connected to output control signals to the servo amplifiers 64, 66 and 68.

  A servo amplifier 70 for controlling the electric motor 6 is additionally provided in the numerical control circuit 60, and the controller 62 is connected to output a rotation speed signal to the servo amplifier 70. A temperature signal from the first temperature sensor 14, a temperature signal from the second temperature sensor 16, and a pressure signal from the pressure sensor 18 are input to the controller 62.

  The controller 62 outputs a rotational speed signal corresponding to both the temperature signal and the pressure signal to the servo amplifier 70, and controls the rotational speed of the electric motor 6 to the rotational speeds N1 to N4 according to the temperature and pressure. Thereby, the control circuit can be configured more easily than the control circuit 50 of the above-described embodiment.

  The present invention is not limited to such embodiments as described above, and can be implemented in various modes without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Variable displacement hydraulic pump with pressure compensation 2 ... Pressure compensation mechanism 6 ... Electric motor 10 ... Tank 12 ... Discharge flow path 14 ... 1st temperature sensor 16 ... 2nd temperature sensor 18 ... Pressure sensor 50 ... Control circuit 52, 62 ... Controllers 54, 64, 66, 68, 70 ... Servo amplifier 60 ... Numerical control circuit

Claims (3)

A tank for storing hydraulic oil;
A hydraulic pump for sucking and discharging the hydraulic oil in the tank;
An electric motor for rotationally driving the hydraulic pump;
A control circuit for controlling the rotational speed of the electric motor;
A temperature sensor for detecting the temperature of the hydraulic oil stored in the tank;
The said control circuit controls the rotation speed of the said electric motor to high rotation, so that the temperature of the said hydraulic fluid detected with the said temperature sensor is low. A second temperature sensor for detecting the temperature of the hydraulic pump is provided, and the control circuit stops the rotation of the electric motor when the temperature detected by the second temperature sensor is equal to or higher than a set temperature. The hydraulic device according to claim 1. The hydraulic device according to claim 1, wherein a numerical control circuit of a machine tool is used as the control circuit.

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