JPH062451Y2 - Electric motor with encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an electric motor with an encoder, in which an encoder for detecting a rotation angle of a rotary shaft of the electric motor is attached to an end portion of the electric motor.

[Prior Art] An electric motor for precision control, such as a servo motor, used for controlling a robot or the like includes an encoder for detecting a rotation angle of the electric motor. Currently used encoders include a photoelectric encoder that uses light and a magnetic encoder that uses magnetism, and semiconductor elements are often used as constituent parts of these encoders.

Most encoders malfunction due to dust, oil, moisture, etc. Therefore, the output shaft of the bracket of the electric motor protrudes so that the encoder is stored in the storage case in a substantially sealed state so that dust, oil, etc. do not enter. It is attached to the side end.

However, the permissible ambient temperature for general semiconductor devices is
The maximum temperature is around 70 ° C., and there is a problem that the life of the encoder including a semiconductor element becomes shorter as the ambient temperature becomes higher.

Therefore, various measures have been conventionally made to reduce the temperature inside the storage case. For example, in the conventional electric motor shown in FIG. 3, the storage case 3 is attached to the end 1a of the electric motor bracket 1 via a heat insulating spacer 2 '. A photoelectric encoder 5 for detecting the rotation angle of the output shaft 4 of the electric motor is housed in the housing case 3. The shape of the heat insulating spacer 2'is flat so that the heat from the electric motor side is mainly transferred from the end surface 1a1 of the end 1a of the bracket 1 into the storage case 3, so that the heat is prevented from covering the end 1a1. Is formed in.

[Problems to be Solved by the Invention] However, even if the heat insulating spacer 2'is used, the temperature in the storage case 3 may exceed the allowable range temperature of the semiconductor element. This is a heat insulating material and is a heat insulating spacer 2 '.
The reason is that even if the heat sink is formed, the heat transfer cannot be completely blocked, and some heat is transferred through the heat insulating spacer 2 '.

For example, when a servomotor rated at 700 W is operated for a long time at a rated torque of 100% using a heat insulating spacer 2'having a thickness of about 100 mm, the temperature rise in the storage case 3 relative to the ambient temperature of the electric motor (maximum temperature) is Although depending on the temperature, it was confirmed that the temperature was approximately 35 ° C to 45 ° C. If the ambient temperature at this time is 30 ° C., the maximum temperature in the storage case 3 exceeds the allowable ambient temperature of the semiconductor element.

If the thickness of the heat insulating spacer 2'is increased, the storage case 3
Although the internal temperature rise can be significantly reduced, the length of the electric motor including the storage case 3 becomes extremely long, so that it cannot be used for a small device at all. Therefore, conventionally, the motor is operated below the rated value to lower the heat generation temperature of the motor. Therefore, conventionally, since the electric motor cannot be used at the rated torque, an unnecessarily large electric motor must be used, and there has been a problem that the electric motor cannot be downsized and the price cannot be reduced.

An object of the present invention is to provide an electric motor with an encoder that can drive the electric motor with a larger torque without making the total length of the electric motor too long.

[Means for Solving the Problems] As shown in FIGS. 1 and 2 showing an embodiment of the present invention, the present invention has a storage case 3 attached to an end 1a of an electric motor via a heat insulating spacer. In the electric motor with an encoder in which the encoder 5 for detecting the rotation angle of the output shaft 4 is housed in a substantially sealed state, the above-mentioned problem is solved by using the heat insulating spacer 2 having a novel structure.

The heat insulating spacer 2 used in the present invention includes a tubular portion 2a that rotatably houses a part of the output shaft 4 of the electric motor. The outer peripheral surface 2a2 of the tubular portion 2a is the end portion 1a of the electric motor.
And the storage case 3 is formed so as to be located radially inward of the respective outer peripheral surfaces 1a2 and 3b.

In the specification of the present application, the term "electric motor" is not limited to a servomotor, and includes all types of electric motors to which an encoder is attached. Further, the term "encoder" includes all types of encoders that use semiconductor elements for at least some of their components.

[Operation of the Invention] In the present invention, the outer peripheral surface 2a of the tubular portion 2a of the heat insulating spacer 2 is
2 is the outer peripheral surface 1a2 of the end 1a of the motor and the storage case 3
Since the outer peripheral surface 3b is positioned radially inward of the outer peripheral surface 3b, the outer peripheral surface 2a2 of the tubular portion 2a and the end portion 1 of the electric motor
The end surface 1a1 of a and the end surface 2b11 of the storage case 3 on the electric motor side.
An air flow path surrounded by and is formed between the electric motor and the storage case 3. This air flow path is the end face 1 of the motor.
It prevents the transfer of heat from a1 and promotes the dissipation of heat from the end face 1a1 of the electric motor.

That is, the outer peripheral surface 2a2 of the tubular portion 2a of the heat insulating spacer 2
End face 2 on the electric motor side of storage case 3 located outside of
Since b11 faces the end surface 1a1 of the electric motor through the air layer having a small heat transfer rate, the heat transfer from the electric motor side can be greatly reduced. Further, for example, when the electric motor is used horizontally, the air that is heated and moves upward flows through the air flow path, so that the heat can be advantageously dissipated from the end surface 1a1 of the electric motor. In addition, when some air flow occurs in the device in which the electric motor is arranged, the air flow passage exerts a chimney effect, and the air flow is generated in the air flow passage, which promotes heat dissipation from the electric motor. To do.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, the same members as those of the conventional electric motor shown in FIG. 3 are designated by the same reference numerals as those shown in FIG.

The electric motor of the present embodiment is a servo motor, and a plurality of brush holders 7 are provided on the outer periphery of the end 1a of the metal bracket 1 at substantially equal intervals. The heat insulating spacer 2 is formed using a heat insulating resin material having heat resistance and less thermal deformation, for example, a PPS resin manufactured by Philips Petroleum Co., Ltd. under the name of "Ryton".

The heat insulating spacer 2 has a shape as shown in FIGS. 2A and 2B, and is a disk-shaped plate to which the cylindrical tubular portion 2a that rotatably accommodates the base of the output shaft 4 and the storage case 3 are attached. The tubular portion 2b and the columnar portions 2c fixed to the end portion of the plate-shaped portion 2b on the tubular portion 2a side at substantially equal intervals so as to surround the tubular portion 2a.

An annular step portion 2a1 is formed at one end of the tubular portion 2a, and this step portion 2a is fitted with a cylindrical convex portion 1a provided at the end portion 1a of the bracket 1. In this way, the step portion 2a of the tubular portion 2a and the convex portion 1a2 of the bracket 1 are fitted to each other to prevent dust and oil from entering from the outside.

A plate-shaped portion 2b is integrally provided at the other end of the tubular portion 2a, and an annular flange portion 2b1 is provided on the outer periphery of the plate-shaped portion 2b on the tubular portion 2a side. At the center, a through hole 2b2 is formed through which the output shaft 4 of the electric motor is rotatably passed. In addition, the end surface 2 of the plate-shaped portion 2b on the tubular portion 2a side
b11 has four columnar portions 2c at equal intervals around the tubular portion 2a.
Are integrally provided with the plate-shaped portion 2b.

A screw mounting hole 2c1 is formed so as to penetrate the columnar portion 2c and the plate-shaped portion 2b, and the end portion 1 of the bracket 1 is formed.
The blocking spacer 2 is firmly fixed to the bracket 1 of the electric motor by aligning the screw hole portion (not shown) provided in a with the screw mounting hole 2c1 and screwing in the screw. In this embodiment, the plate-shaped portion 2b of the blocking spacer 2 also serves as a lid member that closes the opening of the storage case 3, in other words, the plate-shaped portion 2
b constitutes a part of the storage case 3.

In this embodiment, the outer peripheral surface 2a2 of the tubular portion 2a is the outer peripheral surface 3b of the storage case 3 and the outer peripheral surface 1 of the bracket 1 of the electric motor.
The tubular portion 2a is formed so as to be located radially inward of a3. Therefore, the end surface 2 of the plate-like portion 2b located outside the outer peripheral surface 2a2 of the tubular portion 2a of the heat insulating spacer 2
b11 (the end surface of the storage case on the electric motor side) is connected to the end surface 1a1 of the bracket 1 of the electric motor through an air layer having a small thermal conductivity.
The heat transfer from the motor side can be significantly reduced.

Further, by doing so, the end surface 1 of the bracket 1 of the electric motor
An air flow path exhibiting a chimney effect can be formed between a1 and the end surface 2b11 of the plate-shaped portion 2b and the outer peripheral surface 2a2 of the tubular portion 2a. For example, when the electric motor is used horizontally, the heated air moving upward moves through this air flow path and effectively dissipates the heat from the end surface 1a1 of the bracket 1 of the electric motor. In addition, even if some air flow occurs in the device in which the electric motor is arranged, the air flow path exerts a chimney effect, and the air flow is generated in the air flow path. Promote.

In addition, it is preferable that the thickness of the tubular portion 2a and the cross-sectional area of the columnar portion 2c be small enough not to significantly reduce the mechanical strength. This is because even if the heat insulating spacer 2 is formed of a resin having a heat insulating property, the heat transfer cannot be completely insulated, and a certain amount of heat is transferred through the spacer 2.

The storage case 3 is formed by pressing a metal plate, which is a material having good heat transfer, into a bowl shape by press molding. A flange portion 3a that abuts the flange portion 2b1 of the plate-shaped portion 2b of the heat insulating spacer 2 is provided on the peripheral portion of the opening of the bowl-shaped storage case 3.

A photoelectric encoder 5 and a signal processing circuit that processes an output signal of the encoder 5 are housed in a space surrounded by the housing case 3 and the plate-shaped portion 2 b of the heat insulating spacer 2. The photoelectric encoder 5 includes a light emitting element 5a and a light receiving element 5
b and the slit plate 5c. Light receiving element 5b
Is formed by forming a plurality of light receiving element bodies at equal intervals on an annular semiconductor substrate, and the plate-shaped portion 2 of the heat insulating spacer 2 is formed.
It is positioned and fixed in the annular recess 8a of the cylindrical mounting portion 8 fixed on the end surface of the storage case 3 side of b. The mounting portion 8 is formed of a resin having a heat insulating property similarly to the heat insulating spacer, and can be integrally formed with the heat insulating spacer 2 when manufacturing the heat insulating spacer.

The light emitting element 5a and the semiconductor element forming the signal processing circuit are mounted on the circuit board 9 fixed to a fixing member 8b protruding from the mounting portion 8. Generally, the light emitting element 5a
Is composed of a light emitting diode. Slit plate 5c
Is fixed to a metal boss 10 fixed to the output shaft 4 of the electric motor. The slit plate 5c is formed by forming a plurality of slits 5 on an annular glass plate.

As in the case of FIG. 3, a servomotor rated at 700 W was used to measure the average temperature rise in the storage case 3 relative to the ambient temperature during continuous operation of the motor. It was confirmed that the temperature can be lowered by about 5 to 10 ° C. The thickness of the heat insulating spacer 2 used at this time (value obtained by adding the height of the tubular portion 2a and the thickness of the plate portion 2b) was about 20 mm. As shown by the chain double-dashed line, the radiation fins 1
If the number 1 is provided, the temperature rise in the storage case 3 can be further reduced, and if the number of the radiation fins 11 is increased, the motor can be operated at the rated torque 100% without any trouble.

In the above embodiment, the heat insulating spacer 2 is composed of the tubular portion 2a and the plate-like portion 2b. However, when the lid member for closing the opening of the storage case 3 is separately provided, the heat insulating spacer 2 is tubular. It can be configured by only the portion 2a. In this case, the end of the tubular portion 2a on the side of the storage case 3 and the lid member may be connected to each other by an appropriate means such as bonding.

In the above embodiment, the tubular portion 2a is formed in a cylindrical shape, but if the output shaft 4 is rotatably housed,
Of course, it may have any shape and may have a prismatic shape.

Further, in the above embodiment, in order to improve the positioning accuracy,
Although the four columnar portions 2c ... Are fixedly provided on the plate-shaped portion 2b of the heat insulating spacer 2, the columnar portions are not always necessary.

Although the photoelectric encoder is used as the encoder in the above embodiment, the present invention can be applied to the case where a magnetic encoder using a Hall element as the detecting element is used. Further, the electric motor is not limited to the servo motor, and the present invention can be applied to all electric motors.

Further, in the above embodiment, the tubular portion 2 of the heat insulating spacer 2 is used.
Although a is fixed to the end face 1a1 of the bracket 1 of the electric motor, it goes without saying that the tubular portion 2a may be fixed to the end of the iron core of the electric motor.

ADVANTAGES OF THE INVENTION According to the present invention, the outer peripheral surface of the tubular portion of the heat insulating spacer is positioned radially inward of the outer peripheral surfaces of the end portion of the electric motor and the storage case, and the outer peripheral surface of the tubular portion and the electric motor. Since the air flow path surrounded by the end face of the end of the and the end face of the storage case on the electric motor side is formed between the electric motor and the storage case,
It is possible to suppress the transfer of heat from the end surface of the electric motor and promote the dissipation of heat from the end surface of the electric motor. Therefore, according to the present invention, the electric motor can be operated with a larger torque without making the total length of the electric motor too long.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view of an embodiment of the electric motor of the present invention, and FIGS. 2A and 2B are a plan view and a partial cross-sectional view of a heat insulating spacer used in the embodiment of FIG. 1, respectively. FIG. 3 is a schematic partial sectional view showing the structure of a conventional electric motor. 1 ... Bracket, 2 ... Insulation spacer, 3 ... Storage case,
4 ... Output shaft, 5 ... Encoder, 7 ... Brush holder, 11
… Radiation fins.

Claims (4)

[Scope of utility model registration request] 1. An electric motor with an encoder, wherein an encoder for detecting a rotation angle of an output shaft is housed in a storage case attached to an end of the electric motor via a heat insulating spacer in a substantially sealed state. A tubular portion that rotatably accommodates a part of the output shaft of the electric motor, the outer circumferential surface of the tubular portion being radially inward from the respective outer peripheral surfaces of the end portion of the electric motor and the storage case. An electric motor with an encoder, characterized in that it is formed to be located at. 2. The heat insulating spacer has a plate-shaped portion that constitutes a lid member of the storage case at an end portion on the storage case side, and the plate-shaped portion is with respect to the end portion of the electric motor. The electric motor with an encoder according to claim 1, wherein a plurality of columnar portions for supporting are provided between the plate-shaped portion and the end portion. 3. The motor with encoder according to claim 2, wherein the tubular portion, the plate-shaped portion and the columnar portion are integrally formed of a heat insulating resin material. . 4. The utility model registration claim according to claim 2, wherein the storage case is formed of a material having good heat conduction, and a heat radiation fin is fixedly provided on the outer peripheral surface of the storage case. An electric motor with an encoder according to paragraph.