JPH08266014A - Overheat protective device for motor - Google Patents

Abstract

PURPOSE: To provide an overheat protective device for a motor which can perform optimal temperature control in accordance with the driving state of a motor. CONSTITUTION: A heater coil 2 to which a current flowing through a motor 3 is applied is wound and fixed to a thermostat 1 and at the sane time heat generated by the heater coil 2 is dissipated from a bracket 6 which is a radiating member through an elastic body 9. When the temperature of the thermostat 1 becomes not less than a predetermined temperature, an internal contact is opened to cut off a current to the motor 3, thereby stopping the rotational operation of the motor 3. Heat from the heater coil 2 is dissipated from the bracket 6, thereby being able to properly adjust the operation time of the thermostat 1, so that optimal temperature control may be performed in accordance with the driving state of a motor as at the time when an overcurrent flows or at the time of rated-load operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor temperature protection device, and more particularly to a motor temperature protection device used in a hydraulic pump or the like.

[0002]

2. Description of the Related Art Conventionally, in the case of a vehicle having a driver's cab (cab) above the engine such as a truck, a hydraulic pump is used to move the driver's cab upward to repair or inspect the engine. It has a flip-up structure. This hydraulic pump is driven by a motor. For example, when the cab cannot be rebounded due to an abnormal overload, the motor is controlled to further increase the torque. The current may increase and overcurrent may flow. Therefore, in such a case, the motor may be heated and burned. Therefore, as a protection thereof, it is necessary to detect the temperature of the motor and stop the driving of the motor.

Further, when the motor is driven for a predetermined time or longer even during the rated operation of the motor, it is necessary to stop the driving of the motor when the temperature of the motor exceeds a predetermined temperature.

As a conventional motor temperature protection device, for example, as disclosed in Japanese Utility Model Laid-Open No. 2-88454, a relay holder including a thermal relay is formed by a conductor itself through which a load current of the motor flows. A thermal relay directly detects the temperature rise due to the heat generation of the relay holder to prevent the motor from burning.

[0005]

However, in such a prior art, since the electric contacts of the thermal relay are opened and closed by the heat generated by the relay holder, the motor temperature can be quickly increased with respect to the instantaneous temperature rise, for example, in about 10 seconds. When the contact of the thermal relay is configured to open, there is a problem that the contact operates to open in a short time, for example, several minutes even during rated operation of the motor.

That is, in order to maintain the engine, when the operator's cab is flipped up, the engine is inspected and maintained, and the operator's cab is lowered to inspect the engine operating condition several times, the temperature protection operation is performed. If it is performed in a short time, the motor will stop during the inspection and maintenance, and there will be a problem that the motor cannot be restarted for more than 10 minutes until the temperature of the protection device naturally decreases. In order to solve this point, if the heat generation of the relay holder is suppressed so that the rated time during the rated operation of the motor is, for example, 10 minutes, this time the relay will operate quickly when an overcurrent flows through the motor. Instead, a problem that the motor burns out occurs.

An object of the present invention is to provide a motor temperature protection device capable of performing optimum temperature protection according to the driving state of the motor.

[0008]

In order to achieve the above object, the present invention detects a temperature with a thermostat, and when the detected temperature exceeds a predetermined temperature, shuts off energization to the motor to shut off the motor. In the motor temperature protection device that stops the rotation operation of, the heating coil wound around the thermostat and fixed, the heating coil to which the current flowing in the motor is supplied, and the heat radiation member that radiates the heat generated by the heating coil. When the temperature of the thermostat becomes higher than a predetermined temperature, the contacts inside the thermostat are opened to interrupt the power supply to the motor to stop the rotation operation of the motor.

In the motor temperature protection device, preferably, the heat dissipation member is a bracket forming a part of the outer shell of the motor, and the bracket and the heat generating coil are in close contact with each other to prevent the heat generating coil from the heat generating coil. And a heat transfer member for transferring heat to the heat dissipation member.

In the motor temperature protection device, preferably, the heat transfer member is an elastic body, and the elastic force of the elastic body causes the heat dissipation member and the heat generating coil to come into close contact with each other.

In the motor temperature protection device, preferably, the operation time of the thermostat can be varied by changing the thickness of the elastic body.

[0012]

In the present invention, the heating coil to which the current flowing through the motor is supplied is wound around and fixed to the thermostat, so that the current flowing through the motor is detected and the heat generated by the heating coil is radiated by the heat radiating member. With such a configuration, when the temperature of the thermostat becomes equal to or higher than a predetermined temperature, the contact inside the thermostat is opened to cut off the energization to the motor to stop the rotation operation of the motor.

The heat radiating member is a bracket which constitutes a part of the outer shell of the motor, and is provided with a heat transfer member which is in close contact with the bracket and the heat generating coil to transfer heat from the heat generating coil to the heat radiating member. As a result, the heat from the heating coil can be effectively transferred to the heat dissipation member via the heat transfer member.

Further, the heat transfer member is an elastic body, and the elastic force of this elastic body allows the heat dissipating member and the heat generating coil to come into close contact with each other.

By changing the thickness of the elastic body,
The operation time of the thermostat can be changed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of temperature detecting means according to an embodiment of the present invention.

The thermostat 1 has a temperature contact built in a resin case. When the temperature exceeds a predetermined temperature,
The internal temperature contact opens and becomes non-conductive. On the surface of the thermostat 1, a heating coil 2 which is a conductor made of an insulated wire is wound, and is fixed by an insulating varnish (not shown) or the like. Therefore, the thermostat 1 opens the internal contacts by being heated to a predetermined temperature or higher by the heating coil 2.

By passing a current through the motor through the heating coil 2, when the current becomes abnormally large, the temperature of the heating coil 2 suddenly rises, so that the temperature of the heating coil 2 reaches a predetermined temperature instantly. You can protect the temperature by opening the contact. Further, in a steady state, the motor current is gradually heated, so that when the temperature exceeds a predetermined temperature, the internal contact can be opened to protect the temperature of the motor. Note that a specific configuration for protecting the temperature in the steady state after a desired time has passed will be described later with reference to FIG.

FIG. 2 is a cross-sectional view of an essential part of a motor temperature protection device according to an embodiment of the present invention.

The motor 3 is composed of a stator 5 and a rotating armature 4 rotatably supported inside the stator 5. The rotary shaft 42 of the rotary armature 4 is rotatably supported at both ends by bearings 62 supported by the metal bracket 6. The commutator 41 is fixed to the end of the rotating shaft 42 near the bearing 62. The brush base 7 that supports the brush 8 is fixed to the bracket 6 with screws 71. The commutator 41 is the brush 8
It is slidable with respect to.

On a thermostat 1 having a temperature contact built in a resin case, a heating coil 2 wound with a conductor made of an insulated wire is fixed by an insulating varnish (not shown) or the like. Thermostat 1 to which this heating coil 2 is fixed
Is fixed in the space between the bracket 6 and the brush base 7 via an elastic body 9 such as rubber.

As the elastic body, for example, silicon rubber having a hardness of 20 ° is used. Normal rubber has a hardness of about 40 °. Silicon rubber is softer than this, and even if the silicone rubber is pressed against the bracket 6 side by the thermostat 1, the silicone rubber itself is not deformed and unnecessary stress is not applied to the thermostat 1. Also, the adhesion with the heating coil 2 wound around the surface of the thermostat 1 is enhanced. When the inner surface of the bracket 6 has a large unevenness, liquid silicon rubber is injected between the elastic solid silicon rubber and the bracket 6, and the liquid silicon rubber is naturally cured to serve as a sealant. You may raise the adhesiveness of. Further, sponge-like foamed rubber can be used instead of silicone rubber. As the elastic body, a material having elasticity and good thermal conductivity is selected as described below. Regarding the thermal conductivity, for example, by improving the thermal conductivity by putting aluminum powder in silicon rubber, the operating time of the thermostat is lengthened, or the thermal conductivity is lowered.
It can also be adjusted to shorten the time the thermostat operates.

The heat from the heating coil 2 is transferred to the thermostat 1, and this heat is also transferred to the metal bracket 6 via the elastic body 9 and the bracket 6
Radiated from. Therefore, the temperature of the thermostat 1 is
It rises and falls according to the difference between the amount of heat generated from the heating coil 2 and the amount of heat released to the bracket 6. In the past, since the thermostat was only fixed to the brush base and not in contact with the bracket, heat was only dissipated from the thermostat to the space inside the motor, which caused a rise in the temperature of the brush base. The temperature was rising rapidly. On the other hand, by bringing the thermostat 1 into contact with the bracket 6 which is a heat radiating member via the elastic body 9, the amount of heat radiated through the bracket 6 becomes larger than in the conventional case, so that the temperature rise of the thermostat 1 becomes higher than in the conventional case. Due to the reduction, the time required for the temperature of the thermostat 1 to open the temperature contact becomes longer than before even during operation at the rated load. Moreover, since this time can be varied by adjusting the amount of heat generation, the amount of heat transfer, and the amount of heat radiation, it is possible to achieve temperature protection in an optimum state according to the structure and operating conditions of the motor. The amount of heat generation can be adjusted by changing the number of turns of the heating coil 2 wound around the thermostat 1, changing the thickness of the heating coil, and changing the electrical resistance. The heat transfer amount can be adjusted by changing the material of the elastic body 9 or by changing the elastic body 9 between the bracket 6 and the thermostat 1.
This can be achieved by changing the thickness of the bracket or by changing the contact area of the elastic body 9 between the bracket 6 and the thermostat 1. Further, the amount of heat radiation can be adjusted by changing the size, material and shape of the bracket 6.

The operation of the temperature protection circuit according to the embodiment of the present invention shown in FIG. 3 will be described below.

The thermostat 1 is connected to a power supply voltage V of a battery or the like via a switch S1. Also,
The power supply voltage V is connected to the heating coil 2 via the switch S2, and further connected to the rotating armature 4 via the brush 8 of the motor 3.

Therefore, when the switch S1 is closed, the coil of the switch S2 is energized via the thermostat 1 so that a current flows through the motor 3 and the rotary armature 4 of the motor 3 rotates.

At a steady load, for example, the energizing current is also 15
As low as about A, part of the heat generated from the heating coil 2 is radiated to the outside from the bracket 6 via the elastic body 9,
As shown in FIG. 4, the temperature rise of the thermostat 1 is gentle. When a predetermined temperature is reached after a long-time operation of 10 minutes, for example, 100 ° C. is reached after 10 minutes, the temperature contact of the thermostat 1 is opened.
As a result, since the coil of the switch S2 is de-energized, the switch S2 is opened and the operation of the motor 3 is stopped.
Prevent the motor 3 from burning. Here, in the case of the rated load, the time until the thermostat 1 operates can be adjusted by the heat generation amount, the heat transfer amount, and the heat radiation amount described above, and the thermostat 1 reaches the operating temperature after the time elapses. Then, the rotation of the motor 3 stops. After the motor is stopped, when the temperature of the motor 3 gradually decreases and the temperature of the thermostat 1 also decreases, the temperature contact of the thermostat 1 closes again, so the switch S2 closes and the power supply to the motor 3 resumes automatically. The motor 3 starts rotating.

Further, at the time of overload, for example, 100
When the A current is applied, the temperature of the heating coil 2 rapidly rises as shown in FIG. This temperature rise of the heating coil 2 also raises the temperature of the thermostat 1, but the heat radiation from the bracket 6 via the elastic body 9 cannot be followed, and
In 0 seconds, the contact temperature of the thermostat 1 reaches 100 ° C., the temperature contact of the thermostat 1 opens, and the motor 3
To stop the motor 3 from burning. In this case, the temperature difference between the heating coil 2 and the thermostat 1 reaches about 30 ° C. in 10 seconds, so the temperature and time of the thermostat 1 are set so that the contacts open before the resin case of the thermostat 1 melts. ing.

As described above, when the overcurrent of 100 A flows, the thermostat 1 is operated for 10 seconds, and when the rated load of 15 A is operated, the thermostat 1 is operated for 10 minutes. The thickness of the silicone rubber used as was 1.0 mm.

By the way, the thickness of this silicone rubber is set to 0.
When it was set to 5 mm, the operation time of the thermostat 1 required 15 seconds for an overcurrent of 100 A. This is because the heat radiation from the bracket 6 through the elastic body 1 is larger than that when the thickness of the silicon rubber is 1.0 mm, so that it takes time to raise the temperature of the thermostat 1. After 15 seconds, the surface temperature of the thermostat 1 was 130 ° C. or higher, so that the resin case on the surface was slightly melted. Moreover, during the rated load operation of 15 A, the operation time of the thermostat 1 required 10 minutes or more. This is because the heat radiation from the bracket 6 through the elastic body 1 is larger than that when the thickness of the silicon rubber is 1.0 mm, so that it takes time to raise the temperature of the thermostat 1.

On the other hand, in the conventional method not using the elastic body 1, the operating time of the thermostat 1 was 10 seconds with respect to the overcurrent of 100A. However, 15A
The operating time of the thermostat 1 was 3 minutes during the rated load operation of. At this time, the heat radiation from the thermostat 1 was not sufficient, so that the operation time was short because the thermostat 1 was heated in a short time. The time required to move the cab up and down is about one and a half minutes, and in steady operation for 3 minutes, the cab can be moved up and down only twice, and even during normal engine maintenance, the cab should be moved up and down about twice a day. Therefore, this causes a state in which the motor does not operate during engine maintenance.

As described above, the temperature of the motor can be protected by the simple method of changing the thickness of the elastic body in the originally desired desired time and desired motor condition.

The thickness of the elastic body can be easily changed by cutting the inner surface of the bracket 6 to change the thickness, or by engaging a washer or the like with the bracket 6 for fixing the brush base 7. . Of course, instead of changing the thickness of the elastic body, the material of the elastic body may be changed, or the amount of heat generated by the heating coil 2 may be changed.

Further, the mounting position of the thermostat is not limited to between the brush base 7 and the bracket 6 and may be another place. In the present invention, the temperature of the motor itself is not measured, but the temperature of the motor is measured from the current flowing through the motor, so there are few restrictions on the mounting position of the thermostat. However, for example,
If the brush 8 is mounted near the brush 8, the temperature of the brush 8 rises to about 160 ° C., and at that time, it is necessary to use a thermostat resin case having a heat resistant temperature of 160 ° C. or higher.

The thermostat may be attached to the side surface of the stator, and at this time, a yoke forming the outer shell of the stator may be used as a heat dissipation member. However, since the temperature of the stator yoke is higher than that of the bracket, the heat dissipation effect is small and
Considering the lead wire from the thermostat, it is preferable to mount it on the bracket side. This is because the lead wire is wired from the bracket to the brush in order to energize the brush, and considering the convenience of wiring, it is more convenient to use the thermostat wiring on the bracket side.

According to one embodiment of the present invention, the thermostat 1 can be operated for 10 seconds when an overcurrent of 100 A flows, and the thermostat 1 can be operated for 10 minutes at a rated load operation of 15 A. Depending on the state of the motor, optimum temperature protection of the motor can be performed at a desired time.

Further, this operating time can be easily changed only by changing the thickness of the elastic body interposing the heat radiating means and the heat generating means.

Regarding the assemblability, since the wound thermostat is held by the brush base through the elastic body and sandwiched, the heat dissipation is good and the assembling is easy.

Further, since an existing bracket can be used as the heat radiating means, it is not necessary to use a special heat radiating means in carrying out the present invention.

In the above embodiment, the bracket 6 is used as a heat radiating member and the heat generated from the heat generating coil 2 is radiated from the bracket 6 via the elastic body. However, a separate heat radiating case is used as the heat radiating member. In this heat dissipation case,
A thermostat wound with a heating coil may be embedded.

Further, a heat dissipation plate may be used as the heat dissipation member, and the heat generating coil may be wound on the one in which the heat dissipation plate and the thermostat are closely fixed.

Further, the case of the thermostat itself may be provided with a radiation fin, and the heating coil may be wound on the radiation fin.

In short, by providing a member capable of radiating the heat from the heating coil, a structure capable of radiating a part of the heat from the heating coil even during the rated operation is mitigated to increase the temperature of the thermostat by the heating coil. Then, by extending the time until the thermostat reaches the operating temperature, the desired operating time can be obtained.

[0045]

According to the present invention, in the motor temperature protection device, optimum temperature protection can be performed according to the state of the motor.

[Brief description of drawings]

FIG. 1 is a perspective view of a temperature detecting means according to an embodiment of the present invention.

FIG. 2 is a sectional front view of an essential part in which a thermostat is attached to a motor according to an embodiment of the present invention.

FIG. 3 is an operation circuit diagram according to an embodiment of the present invention.

FIG. 4 is a temperature change graph under steady load according to an embodiment of the present invention.

FIG. 5 is a temperature change graph during overload according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Thermostat 2 ... Heating coil 3 ... Motor 4 ... Armature 5 ... Stator 6 ... Bracket 7 ... Brush base 8 ... Brush 9 ... Elastic body 41 ... Commutator 42 ... Rotating shaft 62 ... Bearing 71 ... Screw S1 ... Switch S1 S2 ... Switch S2

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironori Watanabe 3085 Higashiishikawa Nishikonai 3085, Hitachinaka City, Ibaraki Prefecture Hitachi Car Electronics Co., Ltd.

Claims (4)

[Claims] 1. A temperature protection device for a motor, wherein a temperature is detected by a thermostat, and when the detected temperature exceeds a predetermined temperature, the motor is de-energized to stop the rotation operation of the motor. A heating coil, which is wound and fixed, and through which a current flowing through the motor is conducted, and a heat radiating member that radiates heat generated by the heating coil are provided, and when the temperature of the thermostat becomes a predetermined temperature or higher, the internal contacts A temperature protection device for a motor, which is opened to shut off the power supply to the motor to stop the rotation operation of the motor. 2. The motor temperature protection device according to claim 1, wherein the heat dissipation member is a bracket that constitutes a part of the outer shell of the motor, and the bracket and the heating coil are in close contact with each other to generate the heat. A temperature protection device for a motor, comprising: a heat transfer member that transfers heat from a coil to the heat dissipation member. 3. The motor temperature protection device according to claim 2, wherein the heat transfer member is an elastic body, and the elastic force of the elastic body brings the heat dissipation member and the heat generating coil into close contact with each other. Temperature protector. 4. The motor temperature protection device according to claim 1, wherein the operating time of the thermostat can be varied by changing the thickness of the elastic body.