JPH09238449A - Linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cooling performance by fitting a cooling means for each driving coil. SOLUTION: When a driver 17 is controlled by a control part 18 to pass electric current through a plurality of coils 1, a moving element 6 obtains thrust for movement. At the coil 1 through which electric current has passed, heat is generated by Joule heat. In a temperature sensor 19 embedded in the coil 1 by the heat, electric potential rises with temperature rise, and its outputted voltage is compared with voltage corresponding to the preset temperature of a reference voltage source 23. When the coil 1 is heated to the preset temperature or higher, a distributor 9 for transporting refrigerant only to the heated coil is opened to deliver refrigerant, thus restraining the temperature of the coil from rising.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor which is used as an actuator of, for example, an ultra-precision stage, and is provided with a cooling pipe independently controlled for each drive coil.

[0002]

2. Description of the Related Art A moving coil type linear motor has, for example, as shown in FIG. 4, a stator 2 around which a coil 1 is wound, and a mover in which a permanent magnet 4 is provided on a movable side yoke 3. And a plurality of coils 1 so as to be sandwiched between the permanent magnets 4.
Is located. The permanent magnet 4 of the movable yoke 3 constitutes a mover. In the linear motor having such a configuration, thrust is obtained by sequentially switching the currents flowing through the plurality of coils 1.

Conventionally, as a method for removing heat generated by an electric current passed through a coil, natural air cooling or JP-A-63-
A method (collective cooling method) of uniformly forcibly cooling the entire coil as described in 157643 has been adopted. FIG.
Shows a conventional batch cooling type linear motor. The linear motor shown in the figure includes a coil 1, a pipe 5 wound around the coil 1, and a mover 6 made of a permanent magnet. The pipe 5 is adapted to allow a temperature-controlled fluid to flow therein.

[0004]

However, in the above-mentioned conventional example, the temperature of the coil 2 is raised by the heat radiation only by the cooling effect by the natural air cooling, which causes the following inconvenience. (1) When a linear motor is attached to a precision machine, the linear motor becomes a heat source and the structure is thermally deformed, resulting in a loss of accuracy. (2) The electrical characteristics of the linear motor change due to the temperature rise of the coil. (3) Since the temperature of the permanent magnet attached to the yoke rises, the life of the magnet is shortened.

Further, the batch cooling system using a medium disclosed in Japanese Patent Laid-Open No. 63-157643 solves the above problems in natural air cooling, but has the following disadvantages. (1) Since the cooling medium is flown to the coil cooling pipe which is not necessary for cooling, a device having a large cooling capacity is required, which results in an increase in cost. (2) Since all the coils are cooled, the temperature difference between the coils cannot be suppressed to a small level, the electrical characteristics of the coils are not stable, and precise control becomes difficult.

It is expected that the number of coils of the linear motor will increase as the wafer size increases in the future, and the problems of heat generated from the coils and the temperature difference between the coils will become more important.

In view of the above-mentioned problems in the conventional example, the present invention effectively prevents the temperature difference between the drive coils in the linear motor, suppresses thermal deformation of the driven object, and improves the electrical characteristics of the linear motor itself. The purpose is also to improve reliability.

[0008]

In order to achieve the above object, the present invention comprises a stator and a mover, and at least one of the stator and the mover has a plurality of drive coils. In the linear motor having a cooling unit for cooling the driving coil, the cooling unit is an individual cooling unit provided for each of the driving coils.

In a preferred embodiment of the present invention, the individual cooling means has individual control means for independently controlling the cooling operation thereof, and the individual control means controls the temperature of the coil detected by the temperature detector. Based on this, the cooling operation is controlled. This individual control can also be performed based on a signal corresponding to the coil drive signal. For cooling, heat exchange is performed using a refrigerant. Cooling can also be performed using an electric / heat conversion element.

[0010]

The above-mentioned problems in the collective cooling system using the medium disclosed in Japanese Patent Laid-Open No. 63-157643 are caused by the fact that the individual coils are not independently cooled. . In the present invention, since the individual coils are independently cooled, it is not necessary to cool the coils that are not necessary for cooling, and the cooling means can be downsized as a whole and the cost can be reduced. Also,
The temperature difference between the coils can be suppressed to a small level, the electrical characteristics of the coils can be stabilized, and precise control can be easily performed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to one embodiment of the present invention,
Piping means for transporting heat to the driving coil portion, which is a heat source, and control means for controlling the flow of the heat transfer medium are provided in each drive coil, and the heat transfer medium flows through the piping according to the heat generation of each drive coil. By controlling in this manner, a linear motor is provided in which the temperature rise of each heat source and its vicinity due to radiation is suppressed, and each coil portion has the same temperature. Further, since it is not necessary to transport the heat transfer medium to all the coils, the device can be downsized.

As the heat transfer medium, for example, a liquid such as water, a gas such as air, or another fluid is used. Further, a proportional valve, a flow rate controller or the like can be used as the control means.

With such a structure, the Joule heat generated in the drive coil section is effectively taken out by the heat transfer medium (refrigerant) in the pipe, and the heat generation in a part of the entire coil section is suppressed uniformly. The equipment accuracy is improved, the equipment is downsized, the cost is reduced, and the factory equipment is labor-saving.

[0014]

1 shows a coil portion and a cooling portion of a linear motor according to an embodiment of the present invention. In the figure, 1 is a coil, 2 is a stator, 7 is a pipe A for sending the temperature-controlled refrigerant from a cooler (not shown), and 8 is for distributing the refrigerant to a cooling tank 12 attached to each coil 1. , Pipe B (1
Pre-distribution tank placed in front of 1), 9 is a pre-distribution tank 8
A distributor for selectively sending the refrigerant stored in the tank 12 to one of the tank 12 that needs cooling and the bypass pipe 10 when it is not necessary to cool the coil, and 11 sends the refrigerant to each cooling tank 12. Pipes B and 13 for returning the refrigerant that has absorbed heat from the coil for cooling again.
Is a collection and delivery tank for converting multiple pipes into one pipe, 15
Indicates a pipe D for returning the heat-absorbed refrigerant to a cooler (not shown).

FIG. 2 is a conceptual diagram of the linear motor of FIG. 1 and a cooling system for cooling the linear motor. In FIG. 2, 16 is a cooler for controlling (cooling) the temperature of the refrigerant, and 17
Is a coil driver for supplying a current to the drive coil 1 to drive the mover, and 18 is a coil current control unit for controlling the drive unit (driver 17). Further, 19 is a temperature sensor for detecting the temperature of each coil portion, 2
0 is a distribution control unit (a distributor opening / closing control unit) for controlling from which distributor the refrigerant is sent to the cooling tank based on the information of each temperature sensor, and 21 is a distributor drive for driving the distributor. The circuit is shown. Reference numeral 22 denotes a bypass control and drive circuit for operating the bypass path of the refrigerant when the temperature of each coil is uniform, and 23 denotes a reference voltage source.

In the above-mentioned structure, when the driver 17 is controlled by the control unit 18 and the current is passed through the plurality of coils 1 while switching the current, the mover 6 (FIG. 5) obtains thrust.
Moving. At this time, heat is generated in the coil 1 in which the current has flowed due to Joule heat. Due to this heat, the potential of the temperature sensor 19 embedded in the coil 1 rises as the temperature rises, the output voltage thereof is compared with the voltage according to the set temperature from the reference voltage source 23, and the coil 1 generates heat above the set temperature. If so, the distributor 9 for transporting the refrigerant only to the coil that has generated heat is opened, and the refrigerant is sent to suppress the temperature rise of the coil.

According to the present embodiment, the circulation mechanism as described above cools only the coils that generate heat, suppresses the temperature rise of the coils, and keeps each coil at a constant temperature. As a result, (1) thermal deformation of the mover 6 and peripheral parts can be suppressed, (2) the electrical characteristics of the linear motor are stable, (3) the life of the magnet is extended, and (4) cooling. The advantage is that the amount of refrigerant can be reduced in the entire system and the device can be downsized.

In the control shown in FIG. 2, the control unit 2
Although each distributor 9 is opened and closed by using a comparator for 0, if a flow rate controller is used instead of the distributor 9 and the amount of the refrigerant flowing in each coil 1 is controlled by an analog amount corresponding to the temperature difference, Precise temperature control is possible.

Further, as shown in FIG. 3, if the distributor 9 or the flow rate controller is controlled according to the coil drive signal, the system can cope with the temperature rise at an earlier stage. Further, as long as the device operates in a predetermined sequence, the distributor 9 or the flow rate controller can be controlled in the sequence to construct a system capable of coping with the temperature rise. Further, the temperature sensor 19 may be omitted if the accuracy of temperature control permits.

According to the above-described embodiment, by independently mounting the cooling pipes on the plurality of drive coils of the linear motor and controlling each of them, the temperature difference between the coils can be effectively and uniformly suppressed. . Therefore, the overall thermal deformation of the structure with the linear motor attached is suppressed, the electrical and mechanical characteristics of the linear motor are kept stable, the life of the permanent magnet of the linear motor is extended, and the accuracy is kept stable. It is also effective in reducing the size of the entire device.

[0021]

Modifications of Embodiments Although the cooling means using the refrigerant has been described in the above embodiments, the same effect can be obtained even if a Peltier element which is an electric / heat exchange element is used as the cooling means. In this case, a cooling system using a refrigerant is not required, which allows further miniaturization.

[0022]

As described above, according to the present invention,
By providing cooling means independently to a plurality of drive coils of the linear motor and individually controlling each cooling means, the temperature difference between the coils can be effectively and uniformly suppressed. Therefore, the overall thermal deformation of the structure with the linear motor attached is suppressed, the electrical and mechanical characteristics of the linear motor are kept stable, the life of the permanent magnet of the linear motor is extended, and the accuracy is kept stable. It is also effective in reducing the size of the entire device.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a linear motor according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a cooling device used in the linear motor of FIG.

FIG. 3 is a conceptual diagram of a cooling control method according to another embodiment of the present invention.

FIG. 4 is a perspective view of a conventional linear motor.

FIG. 5 is a perspective view of a conventional cooling device for a linear motor.

[Explanation of symbols]

1: coil, 2: stator, 3: movable side yoke, 4: permanent magnet, 5: piping, 6: mover, 9: distributor, 10, 1
1, 13: piping, 12: cooling tank, 17: coil driver, 18: coil current control unit, 19: temperature sensor, 20: distributor opening / closing control unit, 21: distributor drive circuit, 22: bypass control and Drive circuit, 23:
Reference voltage source.

Claims (7)

[Claims] 1. A linear system comprising a stator and a mover, at least one of the stator and the mover having a plurality of drive coils, and a cooling means for cooling the drive coils. In the motor, the cooling means is an individual cooling means provided for each of the drive coils, and is a linear motor. 2. The linear motor according to claim 1, wherein the individual cooling means has an individual control means for independently controlling the cooling operation thereof. 3. The linear controller according to claim 2, wherein the individual control unit includes a temperature detector that detects the temperature of the corresponding coil, and controls the cooling operation based on the detected temperature. motor. 4. The linear motor according to claim 2, wherein the individual control unit controls the cooling operation based on a signal corresponding to a drive signal of a corresponding coil. 5. The linear motor according to claim 1, wherein the individual cooling means performs heat exchange using a refrigerant. 6. The linear motor according to claim 2, wherein the individual cooling means performs heat exchange using a refrigerant, and the individual control means controls the temperature of the refrigerant. . 7. The linear motor according to claim 1, wherein the individual cooling means cools using an electric / heat conversion element.