TW202020307A - Constant-pressure liquid supply device - Google Patents

Abstract

This constant-pressure liquid supply device is provided with: a pump unit (4) including a volumetric pump body (41) and an electric motor (42); an inverter (72); and a controller (71). The controller includes a table or a relational expression defining the relationship among a first parameter related to an actual torque of the electric motor, a second parameter which is a rotational speed of the pump unit 4, and a discharge pressure of the pump unit. The controller controls the electric motor in accordance with the table or the relational expression while feeding back the first parameter and the second parameter, so that the discharge pressure of the pump becomes a target pressure.

Description

Constant pressure liquid supply device

The present invention relates to a constant-pressure liquid supply device that supplies liquid to an object having a liquid ejection hole.

Patent Document 1 describes a coolant supply device of a working machine. The aforementioned coolant supply device includes a pump, an electric motor, a pressure sensor, and a controller. The pump system sprays coolant. The electric motor runs the pump. The pressure sensor detects the discharge pressure of the coolant discharged from the pump. The controller controls the output frequency of the inverter circuit to the motor based on the detection value of the pressure sensor and the way that the pump's discharge pressure reaches the target pressure.

The coolant supply device described in Patent Document 1 performs feedback control based on the discharge pressure detected by the pressure sensor. The inventor of the present application found that the actual torque of the electric motor in the coolant supply device is directly proportional to the discharge pressure of the pump. Based on this finding, the inventor of the present application has proposed a coolant supply device that adjusts the discharge pressure of the pump based on the actual torque of the electric motor (refer to Patent Document 2).

As the rotation speed of the electric motor increases, the rotation speed of the positive displacement pump also increases, thereby increasing the discharge flow rate of the pump. The tool of the working machine has a hole for spraying the cooling liquid. Therefore, as the discharge flow rate of the pump increases, the discharge pressure of the pump also increases. As the discharge pressure of the positive displacement pump increases, the actual torque of the electric motor will also increase. Therefore, the actual torque of the electric motor is directly proportional to the discharge pressure of the pump.

The controller of the coolant supply device described in Patent Document 2 has a table or relational expression that determines the relationship between the actual torque of the electric motor and the discharge pressure of the pump. The controller controls the electric motor in such a way that the actual torque of the electric motor reaches the target torque according to the table or relationship. As a result, the discharge pressure of the pump will reach the target pressure. The actual torque of the electric motor can be replaced by the output torque calculated by the output current of the inverter, for example. The cooling liquid supply device described in Patent Document 2 does not require a pressure sensor, and has the advantage of simplifying the device configuration. [Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2004-36421. Patent Document 2: Japanese Patent Laid-Open No. 2009-215935.

(Problems to be solved by the invention)

Although not explicitly disclosed in Patent Document 2, the conventional coolant supply device uses a general-purpose motor as an electric motor. General motors cannot continuously output fixed torque stably in the low rotation speed domain. Therefore, the conventional cooling liquid supply device has to limit the output frequency of the inverter in such a manner that the electric motor does not operate below a specific rotation speed.

Compared with general-purpose motors, motors dedicated to inverters have excellent constant torque characteristics in the low rotation speed range. If a motor dedicated to the inverter is used for the coolant supply device, the pump can be operated in the low rotation speed range. If the pump is operated in the low rotation speed range, energy saving of the coolant supply device can be expected. Furthermore, the inverter-specific motor system includes a constant-torque motor dedicated to the inverter.

However, according to the review by the inventor of the present application, it is difficult for the coolant supply device with a motor dedicated to the inverter to perform feedback control based on the actual torque of the electric motor in the low rotation speed range. The reason is that if the rotational speed of the positive displacement pump becomes lower, the volumetric efficiency will drop sharply. The proportional relationship between the actual torque of the electric motor and the discharge pressure of the pump will not be established or difficult to establish especially in the low rotation speed domain.

In addition, according to the review by the inventors of the present application, it can be seen that, as far as the inverter-specific motor is concerned, even if the actual torque is the same, the output current of the inverter will be different when the rotation speed is high and when the rotation speed is low. Therefore, it is difficult to adjust the discharge pressure of the pump by using the output torque calculated from the output current of the inverter to adjust the discharge pressure of the pump.

Therefore, the coolant supply device described in Patent Document 2 makes it difficult to properly adjust the discharge pressure of the pump even if the electric motor and the pump are to be operated in the low rotation speed range.

Furthermore, this problem is not limited to the cooling liquid supply device for the working machine, and the cleaning liquid supply device for the cleaning device has the same problem. The cleaning device is a device that supplies a specific pressure cleaning liquid to the processed product in order to clean the processed product processed by the working machine. Both the cooling liquid supply device and the cleaning liquid supply device are constant-pressure liquid supply devices that supply a specific pressure liquid to an object.

The technique disclosed in this case is to properly adjust the pump discharge pressure in a constant-pressure liquid supply device. (Means to solve the problem)

Specifically, the technology disclosed in this case is a constant-pressure liquid supply device that supplies liquid to an object having a liquid ejection hole.

The constant-pressure liquid supply device includes: a pump unit having a positive displacement pump body that discharges liquid and an electric motor connected to the pump body and operating the pump body; an inverter that changes the rotational speed of the electric motor; and a controller , The pump is controlled by the inverter. The controller has a table or a relational expression that determines the first parameter related to the actual torque of the electric motor, the second parameter of the rotation speed of the pump portion, and the discharge pressure of the pump portion Relationship. The controller controls the electric motor according to the table or the relational expression in such a manner that the first parameter and the second parameter are fed back while the discharge pressure of the pump unit reaches the target pressure.

The controller has a table or relational expression. The aforementioned table or relational expression determines the relationship between the first parameter, the second parameter, and the discharge pressure of the pump. The first parameter is related to the actual torque of the electric motor. The second parameter is the rotation speed of the pump. The conventional device described in Patent Document 2 has a table or a relational expression, and the table or the relational expression determines the relationship between the actual torque of the electric motor and the discharge pressure of the pump part. In the above table or relational expression of the constant-pressure liquid supply device, the second parameter which is the rotational speed of the pump part is added compared to the conventional one. Furthermore, the rotation speed of the pump portion is the rotation speed of the electric motor and the rotation speed of the pump body.

By adding the rotation speed of the pump part to the table or relational expression, the characteristics of the positive displacement pump body can be reflected in the table or relational expression. As described above, the characteristic of the pump body is that as the rotational speed becomes lower, the volumetric efficiency decreases. In addition, the characteristics of the electric motor can also be reflected in the table or relationship. As mentioned above, the characteristic of the electric motor is that even if the electric motor outputs the same torque, the output current value of the inverter is different when the rotational speed is high and when it is low. When the pump part is operated in the low rotation speed range, the controller can appropriately adjust the discharge pressure of the pump part to the target pressure according to the table or the relationship.

Furthermore, the rotation speed of the pump unit as the second parameter can be replaced by the rotation speed of the electric motor calculated by the inverter. In this way, no new sensor is needed, and the structure of the constant pressure liquid supply device will be more simplified.

The aforementioned first parameter may also be the output torque of the aforementioned inverter, or may be the current value of the aforementioned electric motor.

The controller uses the output torque of the inverter or the current value of the electric motor to properly adjust the pump's discharge pressure to the target pressure. The output torque of the inverter is the output torque calculated by the inverter. In particular, if the first parameter is the output torque of the inverter, no new sensor is needed. The structure of the constant pressure liquid supply device can be simplified.

The controller has a table or a relational expression, the table or the relational expression determines the relationship among the first parameter, the second parameter, the third parameter, and the discharge pressure of the pump part, and the controller feeds back the first Parameter, the second parameter and the third parameter, while controlling the electric motor according to the table or the relational expression in such a way that the discharge pressure of the pump part reaches the target pressure, the third parameter may also be the liquid temperature and At least one of the aforementioned operating times of the electric motor.

If the temperature of the liquid changes, the viscosity of the liquid will change. Therefore, if the liquid temperature changes, the relationship between the actual torque of the electric motor and the discharge pressure of the pump part will also change. In addition, if the electric motor runs for a long time, the characteristics of the actual torque of the electric motor relative to the input current value of the motor will change. The operation time of the electric motor is, for example, the total operation time. The controller uses the liquid temperature and/or the operating time of the electric motor to adjust the discharge pressure of the pump unit more appropriately.

Furthermore, the third parameter may be either or both of the aforementioned liquid temperature and the aforementioned electric motor operating time.

The operation area of the pump section can also be divided into a plurality of rotation speed domains, the controller can have a plurality of relational expressions corresponding to the plurality of rotation speed domains, respectively, and can control the electric power according to the corresponding relational expression in accordance with the rotation speed of the pumping section motor.

The inventor of the present application has found that it is preferable to set the relational expression when the rotation speed of the pump portion is high and the relational expression when the rotation speed is low, respectively. The rotation speed of the pump is the rotation speed of the electric motor and the rotation speed of the pump body. For example, when the rotation speed of the pump part is low, the characteristics of the electric motor are strongly reflected in the relational expression. When the rotation speed of the pump part is high, the characteristics of the pump body are strongly reflected in the relational expression. At this time, the controller has two relational expressions, and the two relational expressions are selected according to the rotation speed of the pump part.

The controller has a complex relationship, and controls the electric motor according to the relationship of the rotation speed of the corresponding pump part. With this, the controller can more appropriately adjust the discharge pressure of the pump to the target pressure.

The aforementioned object may also be a tool of a working machine, and the aforementioned liquid may also be a cooling fluid. That is, the constant pressure liquid supply device may be a cooling liquid supply device of a working machine.

The aforementioned electric motor may also be a motor dedicated to the inverter.

When the motor dedicated to the inverter is continuously operated at a low rotational speed, the torque of the motor dedicated to the foregoing inverter is stable. If the electric motor is an inverter-specific motor, the constant-pressure liquid supply device can operate the electric motor and the pump body in the low rotation speed range. By operating the electric motor and the pump body in the low rotation speed range, the constant pressure liquid supply device can achieve energy saving. As mentioned above, the table or relational system includes the second parameter, namely the rotation speed of the electric motor. When the electric motor and the pump body are operated in the low rotation speed range, the controller can appropriately adjust the discharge pressure of the pump part to the target pressure. (Effect of invention)

As described above, the discharge pressure of the pump can be adjusted appropriately according to the aforementioned constant-pressure liquid supply device.

The embodiment of the constant pressure liquid supply device will be described in detail below based on the drawings. The following description is an example of a constant-pressure liquid supply device.

(Structure of coolant supply device) FIG. 1 shows a configuration example in which the constant-pressure liquid supply device disclosed in this case is applied to the cooling liquid supply device 1.

The coolant supply device 1 is attached to the tool 21 in the work machine 2 to supply the coolant. The tool 21 can be anything. As illustrated in FIG. 1, the tool 21 is formed with a discharge hole 22 for discharging a cooling liquid. The cooling liquid is ejected to the processing place through the aforementioned ejection hole 22. The tool 21 is an example of an object having a hole for ejecting liquid.

The coolant supply line 23 is connected to the tool 21. The supply line 23 is connected to the discharge line 3 in the cooling liquid supply device 1 through the connection portion 20 of the cooling liquid supply device 1. The cooling liquid is supplied to the tool 21 through the discharge line 3 and the supply line 23.

A pump unit 4 is arranged in the discharge line 3. The pump unit 4 ejects the cooling liquid toward the tool 21. The pump unit 4 includes a pump body 41 and an electric motor 42.

The pump body 41 is a positive displacement pump of fixed capacity. The pump body 41 may specifically be a rotary pump such as a gear pump, a vane pump, or a screw pump. The pump unit 4 may be a reciprocating pump such as a piston pump or a plunger pump.

The electric motor 42 is connected to the pump body 41. The electric motor 42 may be, for example, a motor dedicated to an inverter. The electric motor 42 may be a PM motor or a general-purpose motor.

The electric motor 42 is connected to the inverter 72. The inverter 72 outputs a rotation speed command to the electric motor 42. The electric motor 42 can change the rotation speed in accordance with the rotation speed command output by the inverter 72.

A controller 71 is connected to the inverter 72. The controller 71 controls the electric motor 42 via the inverter 72. When the working machine 2 is processing, the flow rate of the required coolant is always changed, so the controller 71 always controls the rotation speed of the electric motor 42 through the frequency converter 72.

The frequency converter 72 calculates the output torque to the electric motor 42 and the rotation speed of the electric motor 42. The details will be described later, but the inverter 72 outputs the output torque of the inverter 72 and the rotation speed of the electric motor 42 to the controller 71 as feedback signals. The controller 71 feedback-controls the electric motor 42 based on the output torque of the inverter 72 and the rotation speed of the electric motor 42. Furthermore, the output torque of the frequency converter 72 is an example of a first parameter related to the torque of the electric motor 42. The rotation speed of the electric motor 42 is the second parameter.

A relief line 5 is connected to the discharge line 3 and between the connection portion 20 and the pump portion 4. A safety valve 51 is arranged in the safety line 5. The safety valve 51 is opened under a certain pressure. When the required coolant flow rate of the tool 21 is greatly reduced and the control command output by the controller 71 is abnormal, the safety valve 51 is opened for safety.

The safety wire 5 is connected to the coolant tank 6. The remaining coolant flowing through the safety line 5 is returned to the tank 6. The coolant supplied to the tool 21 also returns to the tank 6, and the illustration is omitted here. The pump part 4 is connected to the tank 6, thereby sucking the coolant in the tank 6.

Furthermore, a pressure gauge 31 showing the pressure of the coolant is connected to the discharge line 3.

(Operation control of coolant supply device) In addition, the operation of the coolant supply device 1 will be described. As described above, the controller 71 performs feedback control of the electric motor 42.

The tool 21 to which the cooling liquid is supplied has a discharge hole 22 through which the cooling liquid is discharged. Therefore, if the flow rates of the coolant in the discharge line 3 and the supply line 23 increase, the discharge pressure of the pump unit 4 becomes higher. The rotation speed of the electric motor 42 is proportional to the discharge pressure of the pump unit 4. In addition, in the fixed displacement positive displacement pump body 41, the discharge pressure is proportional to the torque. The actual torque of the electric motor 42 is equivalent to the output torque of the inverter 72. Therefore, the output torque of the inverter 72 is proportional to the discharge pressure of the pump unit 4. The controller 71 uses the output torque of the frequency converter 72 as a feedback signal. The controller 71 controls the electric motor 42 so that the torque of the electric motor 42 reaches the target torque. The controller 71 can control the pump unit 4 so that the discharge pressure of the pump unit 4 reaches the target pressure without using a pressure sensor that detects the discharge pressure of the pump unit 4. The omission of the pressure sensor can thereby simplify the structure of the coolant supply device 1.

When the pressure of the ejection line 3 and the supply line 23 becomes higher and a feedback signal of a certain torque or more is input to the controller 71, the controller 71 will rapidly reduce the rotation speed of the electric motor 42 to reduce the pressure. Since the amount of the coolant discharged from the discharge hole 22 is adjusted, the safety valve 51 will not open when the coolant supply device 1 is operating normally. Excess coolant will not flow into the safety line 5.

Here, the inverter-specific motor has excellent constant torque characteristics in the low rotation speed domain. If the electric motor 42 is an inverter-specific motor, the pump unit 4 can be operated in the low rotation speed range. By operating the pump unit 4 in the low rotation speed range, the coolant supply device 1 can save energy. However, if the rotation speed of the positive displacement pump body 41 becomes low, the volumetric efficiency will drastically decrease. Therefore, in the low rotation speed domain, the proportional relationship between the output torque of the frequency converter 72 and the discharge pressure of the pump unit 4 is not established or difficult to establish.

In addition, the inventor of the present application found that when the motor dedicated to the inverter has a higher rotation speed and a lower rotation speed, even if the actual torque output by the motor is the same, the output current value of the inverter 72 will be different.

The total efficiency of the pump unit 4 includes the relationship between the volumetric efficiency of the pump body 41 and the input current value and actual torque of the electric motor 42. When the pump portion 4 is operated in the low rotation speed range and when the pump portion 4 is operated at a higher rotation speed than the low rotation speed range, the total efficiency of the pump portion 4 may be different. Therefore, when the pump unit 4 operates in the low rotation speed range, as described above, it is difficult for the controller 71 to control the pump unit 4 based only on the relationship between the output torque of the inverter 72 and the discharge pressure of the pump unit 4.

Therefore, the controller 71 of the coolant supply device 1 has a table or a relational expression that determines the first parameter related to the actual torque of the electric motor 42 and the second parameter of the rotation speed of the pump unit 4, The relationship between the discharge pressure of the pump unit 4 and the pump unit 4 is controlled according to the aforementioned table or the aforementioned relationship. The first parameter is specifically the output torque of the frequency converter 72.

FIG. 2 is an example of a relationship formula (y=a ₁ x ₁ ) that determines the relationship between the output torque (y) of the inverter 72, the discharge pressure of the pump unit 4 (x ₁ ), and the rotation speed of the pump unit 4 (x ₂ ) +a ₂ x ₂ +b ₁ ). The pump unit 4 having the pump body 41 and the electric motor 42 can be operated under various operating conditions, and a multivariate analysis can be performed on the test results (refer to the black dots in FIG. 2) to thereby set the aforementioned relationship. For example, using the torque (y) as the strain number and the ejection pressure (x1) and the rotation speed (x2) as the independent variables, the relationship can be set by multiple linear regression analysis. The constants a ₁ , a ₂ , and b ₁ of the relational expression of the linear expression can be set using, for example, the least square method (OLS). Furthermore, the relational expression is not limited to the first-order expression. The relationship can be quadratic or cubic. The controller 71 can set the target output torque of the inverter 72 based on the target pressure of the pump unit 4, the rotation speed of the pump unit 4, and the relational expression.

In addition, although not shown in the figure, the aforementioned table determines the relationship between the output torque of the inverter 72, the rotational speed of the pump unit 4, and the discharge pressure of the pump unit 4 in the same manner as the aforementioned relationship. The controller 71 can set the target output torque of the inverter 72 based on the target pressure of the pump unit 4, the rotation speed of the pump unit 4, and the gauge.

The controller 71 uses the output torque of the inverter 72 and the rotation speed of the pump unit 4 calculated by the inverter 72 as feedback signals, and controls the pump unit 4 according to the aforementioned table or the aforementioned relationship. As shown in FIG. 1, the controller 71 has a table or relational expression 711 and a subtractor 712 as functional blocks. The controller 71 accepts the signal of the target pressure designated by the working machine 2. The controller 71 also receives the rotation speed signal of the electric motor 42 output by the frequency converter 72. The rotation speed of the electric motor 42 coincides with the rotation speed of the pump body 41. The controller 71 sets the target output torque according to the target pressure and the rotation speed, and according to the table or relational expression 711.

The subtractor 712 calculates the deviation between the target output torque and the output torque of the inverter 72. The output torque of the inverter 72 is the feedback signal output by the inverter 72. The controller 71 outputs the control signal corresponding to the torque deviation to the inverter 72. The frequency converter 72 operates the electric motor 42 in such a way that the torque deviation is eliminated. As a result, the discharge pressure of the pump unit 4 will reach the target pressure.

The rotation speed of the pump part 4 is added to the table or the relational expression 711, whereby the volumetric efficiency of the pump body 41 can be reduced, and the relationship between the input current value of the electric motor 42 and the actual torque output can be reflected to the control of the pump part 4 in. As a result, when the pump unit 4 is operated in the low rotation speed range, the controller 71 can appropriately adjust the discharge pressure of the pump unit 4 to the target pressure. The pump unit 4 is operated in the low rotation speed range, whereby the coolant supply device 1 can save energy. Also, when the pump unit 4 is operated at a higher rotation speed in a lower rotation speed range, the controller 71 can also appropriately adjust the discharge pressure of the pump unit 4.

The feedback signal of the coolant supply device 1 is the output torque of the inverter 72 and the rotation speed of the pump unit 4 calculated by the inverter 72. There is no need to add sensors that are detected as the first parameter and the second parameter of the feedback signal to the coolant supply device 1. The structure of the coolant supply device 1 can be simplified.

Furthermore, in the coolant supply device 1 configured as described above, the table or relational expression 711 contains the first parameter and the second parameter. The table or relation 711 may further contain the coolant temperature as the third parameter. If the temperature of the coolant changes, the viscosity of the coolant will change. If the viscosity of the coolant changes, the relationship between the actual torque of the electric motor 42 and the discharge pressure of the pump body 41 will also change. Therefore, by adding the coolant temperature as the third parameter to the table or relational expression 711, the coolant supply device 1 can adjust the discharge pressure of the pump unit 4 more appropriately. At this time, the relationship between the output torque of the inverter 72 (y), the discharge pressure of the pump unit 4 (x ₁ ), the rotation speed of the pump unit 4 (x ₂ ), and the coolant temperature (x ₃ ) is determined An example is y=a ₁ x ₁ +a ₂ x ₂ +a ₃ x ₃ +b ₁ .

In addition, the third parameter may be the operating time of the electric motor 42. If the operating time of the electric motor 42 becomes longer, the characteristics of the actual torque of the electric motor 42 relative to the input current value of the electric motor 42 will change. Therefore, the operation time of the electric motor 42 is added to the table or the relational expression 711, whereby the coolant supply device 1 can adjust the discharge pressure of the pump portion 4 more appropriately.

Furthermore, as mentioned above, the third parameter may be only the coolant temperature or only the operating time of the electric motor 42. In addition, the third parameter may be both the coolant temperature and the operating time of the electric motor 42.

The first parameter may be the current value of the electric motor 42 instead of the output torque of the inverter 72. The current value of the electric motor 42 can be detected by the sensor.

In addition, the first parameter may be a value proportional to the actual torque of the electric motor 42 in combination of the voltage value and the power value, instead of the output torque of the inverter 72.

(Variation of relational expression) FIG. 2 shows an example of setting a relational expression for the entire operation area of the pump unit 4. The inventors of the present application found that it is preferable to set the relational expression when the rotational speed of the pump portion 4 is high and the relational expression when it is low. The rotation speed of the pump unit 4 is the rotation speed of the electric motor 42 and the rotation speed of the pump body 41. For example, when the rotation speed of the pump portion 4 is low, the characteristics of the electric motor 42 are strongly reflected in the relational expression. When the rotation speed of the pump portion 4 is high, the characteristics of the pump body 41 are strongly reflected in the relational expression. At this time, the controller 71 has two relational expressions, and the two relational expressions are selected according to the rotation speed of the pump portion 4.

FIG. 3 shows an example in which the operation area of the pump unit 4 is divided into a low rotation speed domain and a high rotation speed domain, and the controller 71 has a relational expression corresponding to the low rotation speed domain and a relational expression corresponding to the high rotation speed domain. Furthermore, as shown in FIG. 3, the plane of the single-point straight line displays the virtual plane at the specific rotation speed N. The low rotation speed range is an area below a specific rotation speed N, and the high rotation speed area is an area that exceeds a specific rotation speed N. In the example of FIG. 3, the first relationship (y=a ₃ x ₁ +a ₄ x ₂ +b ₂ ) corresponds to the low rotation speed domain, and the second relationship (y=a ₅ x ₁ +a ₆ x ₂ + b ₃ ) Corresponds to the high rotation speed domain. At a specific rotation speed N, the relational expression has a point of inflection.

When the rotation speed of the pump unit 4 is in the low rotation speed range, the controller 71 controls the electric motor 42 according to the first relationship. In addition, when the rotation speed of the pump unit 4 is within the high rotation speed range, the controller 71 controls the electric motor 42 according to the second relational expression. Thereby, when the pump portion 4 is at a low rotation speed or at a high rotation speed, the controller 71 can more appropriately adjust the discharge pressure of the pump portion 4 to the target pressure.

Furthermore, the operation area of the pump unit 4 is not limited to being divided into two areas as shown in FIG. 3. The operation area of the pump unit 4 can be divided into three or more areas. The controller 71 only needs to have a relational expression corresponding to each area.

The constant pressure liquid supply device disclosed in this case is not limited to the cooling liquid supply device. Although not shown in the drawings, the constant pressure liquid supply device disclosed in this case may be, for example, a cleaning liquid supply device for a cleaning device. The cleaning device sprays a cleaning liquid to the processed product in order to clean the processed product processed by the work machine. The cleaning liquid supply device supplies a specific pressure of cleaning liquid to the cleaning device.

1: Coolant supply device 2: working machinery 3: ejection line 4: Pump Department 5: Safety line 6: slot 20: Connection 21: Tool (object) 22: Spray hole 23: Supply line 31: Pressure gauge 41: Pump body 42: Electric motor 51: Safety valve 71: Controller 72: frequency converter 711: Table or relation 712: Subtractor

FIG. 1 is a circuit diagram illustrating the configuration of a cooling liquid supply device. Fig. 2 illustrates the relationship between the output torque of the inverter, the rotation speed of the pump part, and the discharge pressure of the pump part. FIG. 3 illustrates a relationship different from FIG. 2.

1: Coolant supply device

2: working machinery

3: ejection line

4: Pump Department

5: Safety line

6: slot

20: Connection

21: Tool (object)

22: Spray hole

23: Supply line

31: Pressure gauge

41: Pump body

42: Electric motor

51: Safety valve

71: Controller

72: frequency converter

711: Table or relation

712: Subtractor

Claims (9)

A constant-pressure liquid supply device that supplies liquid to an object with a liquid ejection hole and includes: The pump unit has a positive displacement pump body that ejects liquid and an electric motor connected to the pump body and operating the pump body; a frequency converter that changes the rotational speed of the electric motor; and a controller that uses the frequency converter Controls the pump section; the controller has a table or relational formula that determines the first parameter related to the actual torque of the electric motor, the second parameter of the rotation speed of the pump section, and the pump The relationship between the discharge pressure of the three parts; the controller is to feedback the first parameter and the second parameter while controlling the electric power according to the table or the relationship formula in such a way that the discharge pressure of the pump part reaches the target pressure motor. The constant pressure liquid supply device according to claim 1, wherein the first parameter is the output torque of the inverter or the current value of the electric motor. The constant-pressure liquid supply device according to claim 1 or 2, wherein the controller has a table or a relational expression that determines the first parameter, the second parameter, the third parameter, and the pump part The relationship between the four of the pressure; The controller controls the electric motor according to the table or the relational expression in such a manner that the first parameter, the second parameter and the third parameter are fed back while the discharge pressure of the pump unit reaches the target pressure; The third parameter is at least one of the liquid temperature and the operating time of the electric motor. The constant pressure liquid supply device according to claim 1 or 2, wherein the operation area of the aforementioned pump section is divided into a plurality of rotation speed domains; The controller has a complex relationship corresponding to the complex rotation speed domain, and controls the electric motor according to the corresponding relationship according to the rotation speed of the pump. The constant pressure liquid supply device as described in claim 3, wherein the operation area of the aforementioned pump section is divided into a plurality of rotation speed domains; The controller has a complex relationship corresponding to the complex rotation speed domain, and controls the electric motor according to the corresponding relationship according to the rotation speed of the pump. The constant-pressure liquid supply device according to claim 1 or 2, wherein the electric motor is a motor dedicated for an inverter. The constant-pressure liquid supply device according to claim 3, wherein the electric motor is a motor dedicated for an inverter. The constant-pressure liquid supply device according to claim 4, wherein the electric motor is a motor dedicated for an inverter. The constant-pressure liquid supply device according to claim 5, wherein the electric motor is a motor dedicated for an inverter.

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