JP2019152124A - Constant pressure liquid supply device - Google Patents

Abstract

To estimate deterioration of a pump in advance in a constant pressure liquid supply device which supplies liquid having a constant pressure to an object having a hole for jetting the liquid.SOLUTION: A constant pressure liquid supply device includes: a supply line 3 connected to an object; a volumetric pump 4 which discharges liquid to be supplied to the object; an electric motor 41 which receives supply of a constant voltage to rotate the pump at a constant rotation number; a relief line 5; a relief valve 51 which is disposed in the relief line and opens when a pressure becomes a setting pressure or higher; and a flow rate detection part 52 which is disposed in the relief line and detects a state that a flow rate of the liquid flowing in the relief line becomes a predetermined flow rate or lower. The constant pressure liquid supply device estimates deterioration of the pump based on detection by the flow rate detection part.SELECTED DRAWING: Figure 1

Description

  The technology disclosed herein relates to a constant pressure liquid supply apparatus that supplies a liquid having a constant pressure to an object having a hole for ejecting liquid.

  Patent Document 1 describes a coolant pump device for a machine tool. The coolant pump device includes a positive displacement hydraulic pump, an electric motor that drives the hydraulic pump, and an inverter device that can change an output frequency to the electric motor. The coolant supplied by the coolant pump device is ejected to a machining location through a hole provided in the tool.

  This coolant pump device increases the discharge flow rate of the hydraulic pump so that a required amount of coolant is supplied to the machining site when the volumetric efficiency of the pump device decreases. Specifically, the rotational speed of the electric motor is increased by increasing the output frequency of the inverter device based on the value of the pressure gauge or flow meter installed in the discharge pipe of the hydraulic pump.

  Patent Document 2 describes a coolant supply device for a machine tool. The coolant supply device includes a pump that discharges coolant, an electric motor that drives the pump, a relief valve that limits the maximum discharge pressure of the pump, a flow rate sensor that detects a drain flow rate of coolant discharged from the relief valve, And a controller for controlling the frequency output to the motor by the inverter circuit in accordance with a signal from the flow sensor. The controller controls the discharge capacity of the pump so as to be the optimum discharge capacity.

JP 7-19162 A Japanese Patent No. 5269955

  By the way, the coolant supply apparatus as described in patent document 1 and patent document 2 adjusts the discharge flow rate of a pump by using an inverter apparatus. Unlike this, the coolant supply device is configured to supply a constant pressure coolant to the tool by making the discharge flow rate of the pump constant and opening a relief line connected to the supply line above a predetermined pressure. It is possible. In this coolant supply device, the pump rotates at a constant rotation speed so as to be equal to or higher than a predetermined pressure, and excess coolant returns to the tank through the relief line. The coolant supply device having such a configuration has an advantage that the device configuration is simplified.

  However, the coolant supply device for machine tools is configured to recover the coolant supplied to the tool and return it to the tank, and the inside of the pump may be worn by chips or the like mixed in the coolant. . As wear progresses, the volumetric efficiency of the pump decreases. In a coolant supply device that does not use an inverter device, when the volumetric efficiency of the pump decreases, the pump discharge flow rate decreases.

  As described above, in the coolant supply device that does not use the inverter device, the discharge flow rate of the pump is larger than the required coolant supply amount required for the tool so that excess coolant flows in the relief line. Therefore, even if the discharge flow rate of the pump slightly decreases, it is possible to supply the required supply amount of coolant to the tool. Since the pressure gauge installed in the supply line shows the target pressure even if the discharge flow rate of the pump is somewhat reduced, the user does not notice that the deterioration of the pump has progressed. Then, the user notices that the pump is deteriorated only when the discharge flow rate of the pump further decreases and falls below the required supply amount, because the pressure gauge indicates less than the target pressure.

  To solve this problem, it is required to accurately estimate the deterioration of the pump in advance. Such a problem is not limited to the coolant supply device for machine tools, but also applies to a cleaning device configured to supply a cleaning liquid having a predetermined pressure in order to clean a workpiece processed by the machine tool. .

  The technology disclosed herein accurately estimates in advance the deterioration of a pump in a constant-pressure liquid supply apparatus that supplies a liquid having a constant pressure to an object having a hole for ejecting liquid.

  Specifically, the technology disclosed herein relates to a constant pressure liquid supply apparatus that supplies a liquid having a constant pressure to an object having a hole for ejecting liquid.

  The constant-pressure liquid supply device includes a supply line connected to the object, a positive displacement pump that is disposed in the supply line and discharges the liquid to be supplied to the object, and is supplied with a constant voltage. An electric motor for rotating the pump at a constant rotational speed; a relief line connected between the object in the supply line and the pump; and a relief valve disposed in the relief line and opened at a set pressure or higher And a flow rate detection unit that is disposed in the relief line and detects that the flow rate of the liquid flowing through the relief line is equal to or lower than a predetermined flow rate. And based on the detection of the said flow volume detection part, it estimates that the said pump deteriorated.

  According to this configuration, the electric motor is supplied with a constant voltage and rotates the pump at a constant rotational speed. Since the pump is a positive displacement type, the pump discharge flow rate is constant.

  A relief valve is disposed in a relief line connected to the supply line. The relief valve opens at a predetermined set pressure or higher. Here, the discharge flow rate of the pump is set larger than the liquid supply amount required for the object. By doing so, the excess liquid flows through the relief line, so that it is possible to supply the liquid with a constant pressure to the object through the supply line.

  A flow rate detector is disposed in the relief line. The flow rate detection unit detects that the flow rate of the liquid flowing through the relief line is not more than a predetermined flow rate. As described above, when the discharge flow rate of the pump is sufficiently larger than the supply amount required for the object and excess liquid is flowing through the relief line, the liquid with a certain pressure is supplied to the object. Yes. In this state, the flow rate detection unit does not detect.

  On the other hand, when the discharge flow rate of the pump decreases, the flow rate of the relief line decreases or the liquid does not flow through the relief line even if the required supply amount of liquid is supplied to the object. When the flow rate of the liquid flowing through the relief line falls below a predetermined flow rate, the flow rate detection unit detects. This state is a state in which the volumetric efficiency of the pump is lowered even if the required supply amount of liquid is supplied to the object at a constant pressure. That is, the pump is in a state of deterioration.

  In this way, by estimating that the pump has deteriorated based on the detection of the flow rate detection unit, the deterioration of the pump is accurately estimated in advance when supplying liquid with a constant pressure to the object. can do. By estimating the deterioration of the pump in advance, the deteriorated pump can be replaced before the liquid supplied to the object falls below the required supply amount. By exchanging the pump, it is possible to avoid that the liquid supplied to the object falls below the required supply amount.

  The constant pressure liquid supply device includes a temperature detection unit that detects a liquid temperature difference between a discharge side and a suction side of the pump, and a liquid temperature difference between the discharge side and the suction side of the pump is determined based on the detection of the temperature detection unit. The pump may be estimated to have deteriorated when the temperature is equal to or higher than a predetermined temperature and the flow rate of the liquid flowing through the relief line is equal to or lower than a predetermined flow rate based on the detection by the flow rate detection unit.

  According to the study of the present inventor, it was found that when the deterioration of the pump progresses, heat is generated as the liquid leaks inside the pump, and the temperature of the liquid discharged from the pump increases. That is, the temperature of the pump is one of the parameters related to the deterioration of the pump. For example, the liquid temperature difference between the discharge side and the suction side of the pump is a predetermined temperature or more (note that the liquid temperature on the discharge side> the liquid on the suction side) It can be estimated that the deterioration of the pump is progressing.

  Therefore, the liquid temperature difference between the discharge side and the suction side of the pump is greater than or equal to a predetermined temperature based on the detection of the temperature detection unit, and the flow rate of the liquid flowing through the relief line is less than or equal to the predetermined flow rate based on the detection of the flow rate detection unit. Sometimes it is estimated that the pump has deteriorated. By considering the temperature parameter, the constant pressure liquid supply apparatus can estimate the deterioration of the pump with higher accuracy.

  As described above, according to the constant pressure liquid supply apparatus, it is possible to accurately estimate the deterioration of the pump in advance.

FIG. 1 is a circuit diagram illustrating the configuration of a coolant supply device according to the first embodiment. FIG. 2 is a circuit diagram illustrating the configuration of the coolant supply apparatus according to the second embodiment.

  Hereinafter, embodiments of the constant pressure liquid supply apparatus will be described in detail with reference to the drawings. The following description is an example of a constant pressure liquid supply apparatus.

(Embodiment 1)
FIG. 1 shows a configuration example in which the constant pressure liquid supply device disclosed herein is applied to a coolant supply device in a machine tool.

  The coolant supply device 1 is configured to supply coolant to the tool 2 in the machine tool. The tool 2 may be anything. As illustrated in FIG. 1, the tool 2 is formed with a hole 21 through which coolant is ejected. The coolant is ejected through the hole 21 to the machining location. The tool 2 is an example of an object having a hole for ejecting liquid.

  A coolant supply line 3 is connected to the tool 2. A pump 4 is disposed in the supply line 3. The pump 4 discharges the coolant toward the tool 2. The pump 4 is a positive displacement positive displacement pump. Specifically, the pump 4 may be a rotary pump such as a gear pump, a vane pump, or a screw pump. The pump 4 may be a reciprocating pump such as a piston pump or a plunger pump.

  An electric motor 41 is connected to the pump 4. An AC power source 42 having a predetermined voltage is connected to the electric motor 41. The electric motor 41 may be, for example, a three-phase motor or a single-phase motor. The electric motor 41 rotates at a constant rotational speed by receiving supply of a constant voltage from the AC power source 42. The electric motor 41 rotates the pump 4 at a constant rotational speed. The discharge flow rate of the pump 4 is a constant amount.

  In the supply line 3, a relief line 5 is connected between the tool 2 and the pump 4. A relief valve 51 is disposed in the relief line 5. The relief valve 51 is configured to open at a predetermined pressure. The pressure at which the relief valve 51 opens corresponds to the pressure of the coolant supplied to the tool 2 (that is, the set pressure). When the relief valve 51 opens at the set pressure, the pressure of the coolant supplied to the tool 2 is maintained at a constant pressure.

  The relief line 5 is connected to a coolant tank 6. Excess coolant flowing through the relief line 5 returns to the tank 6. Although illustration is omitted, the coolant supplied to the tool 2 is recovered and returned to the tank 6. Further, the suction side of the pump 4 and the tank 6 are connected. The pump 4 sucks the coolant in the tank 6.

  A flow rate detection unit 52 is disposed in the relief line 5. In the illustrated example, the flow rate detection unit 52 is disposed downstream of the relief valve 51. The flow rate detection unit 52 detects that the flow rate of the coolant flowing through the relief line 5 is not more than a predetermined flow rate. The flow rate detection unit 52 may be configured by, for example, a flow switch (that is, the flow rate detection unit 52 is turned off when the flow rate is equal to or lower than the predetermined flow rate, and an on signal is output when the flow rate exceeds the predetermined flow rate). The flow rate detection unit 52 may be configured by a flow meter that detects the flow rate of the coolant flowing through the relief line 5.

  Here, the flow rate detector 52 may detect that the coolant flow rate is zero or substantially zero. The flow rate detector 52 may also detect that the coolant flow rate is less than or equal to a predetermined flow rate exceeding zero (that is, the flow rate is low).

  The flow rate detection unit 52 is connected to the control unit 7. The flow rate detection unit 52 outputs a signal to the control unit 7. A warning lamp 71 is also connected to the control unit 7. As will be described later, the control unit 7 turns on the warning lamp 71 based on the signal from the flow rate detection unit 52. The warning lamp 71 is lit when the pump 4 is deteriorated. Thereby, the user can know the replacement time of the pump 4.

  A pressure gauge 31 is connected to the supply line 3.

  Next, the operation of the coolant supply device 1 will be described. When supplying the coolant to the tool 2, as described above, the electric motor 41 rotates at a constant rotational speed by receiving supply of a constant voltage from the AC power supply 42. The electric motor 41 rotates the pump 4 at a constant rotational speed. The pump 4 discharges the coolant sucked from the tank 6 toward the tool 2 at a constant discharge flow rate.

  When the pressure in the supply line 3 becomes equal to or higher than the set pressure, the relief valve 51 is opened. A part of the coolant is supplied to the tool 2 and ejected from the hole 21. The coolant cools the tool 2 and the machining location and removes chips.

  The discharge flow rate of the pump 4 is set to be larger than the coolant supply amount required in the tool 2. Excess coolant flows through the relief line 5. The coolant flow rate in the relief line 5 is greater than the predetermined flow rate detected by the flow rate detection unit 52. The coolant supply device 1 can stably supply coolant at a set pressure to the tool 2 with a simple configuration that does not use an inverter.

  When the operation of the coolant supply device 1 continues, chips and the like are mixed in the coolant, and wear progresses inside the pump 4. As a result, the volumetric efficiency of the pump 4 is reduced.

  When the volumetric efficiency of the pump 4 decreases, the discharge flow rate of the pump 4 decreases. As described above, since the coolant supply device 1 rotates the pump 4 at a constant rotational speed, the decrease in the discharge flow rate of the pump 4 and the decrease in the volumetric efficiency of the pump 4 (that is, the degree of deterioration of the pump 4) are proportional. Or approximately proportional.

  Since the discharge flow rate of the pump 4 is larger than the coolant supply amount required in the tool 2, even if the discharge flow rate of the pump 4 slightly decreases, the required supply amount of coolant to the tool 2 can be satisfied. . As the discharge flow rate of the pump 4 decreases, the flow rate of the coolant flowing through the relief line 5 decreases.

  When the flow rate of the coolant flowing through the relief line 5 becomes equal to or less than a predetermined flow rate (zero or a low flow rate close to zero) due to further deterioration of the pump 4, the required supply amount of coolant to the tool 2 can be satisfied. If the pump 4 deteriorates beyond this, the required supply amount of coolant to the tool 2 cannot be satisfied.

  The flow rate detection unit 52 of the relief line 5 outputs a signal to the control unit 7 when the flow rate of the coolant flowing through the relief line 5 becomes a predetermined flow rate or less. The control unit 7 receives the signal from the flow rate detection unit 52 and turns on the warning lamp 71. In this way, it is notified that the deterioration of the pump 4 is progressing, and the replacement of the pump 4 is prompted. Note that the control unit 7 may determine that the flow rate of the coolant flowing through the relief line 5 has become a predetermined flow rate or less based on a signal from the flow rate detection unit 52 including a flow meter. In this configuration, the control unit 7 outputs a lighting signal to the warning lamp 71 when it is determined that the flow rate of the coolant flowing through the relief line 5 has become a predetermined flow rate or less.

  Even if it is attempted to estimate the deterioration of the pump 4 based on the pressure indicated by the pressure gauge 31 of the supply line 3, when the pressure indicated by the pressure gauge 31 decreases, the amount of coolant supplied to the tool 2 is already insufficient. That is, the timing at which the deterioration of the pump 4 can be estimated is late.

  On the other hand, by estimating the deterioration of the pump 4 based on the flow rate of the coolant flowing through the relief line 5, it is possible to accurately estimate the deterioration of the pump 4 before the supply amount of the coolant to the tool 2 becomes insufficient. it can.

(Embodiment 2)
FIG. 2 shows a configuration example of the coolant supply apparatus 10 according to the second embodiment. Compared with the coolant supply device 1 shown in FIG. 1, the coolant supply device 10 has a temperature detection unit 8 that detects a liquid temperature difference between the discharge side and the suction side of the pump 4. The temperature detector 8 may be constituted by, for example, a thermocouple, a thermistor, or a resistance temperature detector. The temperature detector 8 outputs a signal related to the liquid temperature difference to the controller 7.

  Here, when the deterioration of the pump 4 proceeds, the coolant leaks inside the pump 4. According to the inventor's study, it has been found that heat is generated as the coolant leaks in the pump 4 and the temperature of the liquid discharged from the pump 4 increases. That is, if the liquid temperature difference between the discharge side and the suction side of the pump 4 is equal to or higher than a predetermined temperature, it can be estimated that the deterioration of the pump is progressing.

  In the coolant supply device 10, the control unit 7 determines that the liquid temperature difference between the discharge side and the suction side of the pump 4 is equal to or higher than a predetermined temperature based on the signal from the flow rate detection unit 52 and the signal from the temperature detection unit 8. And when the flow rate of the coolant which flows through the relief line 5 is below a predetermined flow rate, the warning lamp 71 is turned on because the pump 4 has deteriorated. Thus, by estimating the deterioration of the pump 4 using not only the flow rate of the coolant flowing through the relief line 5 but also the temperature-related parameters of the pump 4, the accuracy of the deterioration estimation can be further increased.

  Note that the deterioration of the pump 4 is not estimated based on the signal from the flow rate detection unit 52 and the signal from the temperature detection unit 8, but the deterioration of the pump 4 is determined based on the signal from the temperature detection unit 8. You may make it estimate.

  Moreover, the constant pressure liquid supply apparatus disclosed here is not limited to application to the coolant supply apparatus. For example, although the illustration is omitted, the configuration of the constant pressure liquid supply device may be applied to a cleaning device configured to eject cleaning liquid toward the processed product in order to clean the processed product processed by the machine tool. Good.

  Moreover, as an aspect which alert | reports deterioration of the pump 4 to a user, not only the warning lamp 71 but various alerting | reporting aspects are employable. For example, a warning buzzer may be employed, or the user may be notified by displaying on the display unit.

DESCRIPTION OF SYMBOLS 1 Coolant supply apparatus 10 Coolant supply apparatus 2 Tool (object)
21 Hole 3 Supply line 4 Pump 41 Electric motor 5 Relief line 51 Relief valve 52 Flow rate detector 8 Temperature detector

Claims (2)

A constant pressure liquid supply device for supplying a liquid having a constant pressure to an object having a hole for ejecting liquid,
A supply line connected to the object;
A positive displacement pump that is disposed in the supply line and discharges the liquid to be supplied to the object;
An electric motor that rotates the pump at a constant rotational speed by receiving a supply of a constant voltage;
A relief line connected between the object in the supply line and the pump;
A relief valve disposed in the relief line and opened at a set pressure or higher;
A flow rate detection unit that is disposed in the relief line and detects that the flow rate of the liquid flowing through the relief line is a predetermined flow rate or less,
A constant-pressure liquid supply device that estimates that the pump has deteriorated based on detection by the flow rate detection unit. The constant pressure liquid supply apparatus according to claim 1,
A temperature detector that detects a liquid temperature difference between the discharge side and the suction side of the pump,
Based on the detection by the temperature detection unit, the liquid temperature difference between the discharge side and the suction side of the pump is equal to or higher than a predetermined temperature, and the flow rate of the liquid flowing through the relief line based on the detection by the flow rate detection unit is a predetermined flow rate. A constant-pressure liquid supply device that estimates that the pump has deteriorated when:

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