JPH1071830A - Motor driven actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve abrasion resistance of a sliding part by loosely fitting a gear shaft fixing part to a step difference part arranged in a bearing part of a gear, and forming a grease reservoir in a clearance between a side wall of the step difference part and a surface of the gear shaft fixing part in a motor-driven actuator to transmit torque of a motor to an output shaft through the gear. SOLUTION: In a motor-driven actuator to drive various doors of air conditioner for an automobile, torque of a motor is transmitted to an output shaft through a worm wheel and a gear row, and the respective doors are rotated thereby. In this case, a spot facting-shaped step difference part 20 is formed in a side end part (an upper end part) of an upper case 2 of a bearing part 17 of a gear 7, and a gear shaft 12 projecting from a lower case 3 is loosely inserted into a through hole-shaped bearing part 17. An end part 23 of this gear shaft 12 is fitted to a fitting hole 25 of a support part 24 projecting from the upper case 2. The support part 24 is formed into a cylindrical shape to be loosely fitted by forming a prescribed clearance (play) in the step difference part 20 of the gear 7, and this clearance is formed as a grease reservoir G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear mounting structure incorporated in an electric actuator for driving various doors of, for example, an air conditioner for an automobile.

[0002]

2. Description of the Related Art As a production method which has greatly contributed to improvement in productivity in recent years, there is a method generally called modularization or unitization. In these, we consider a structure or function with certain features as a single component, and combine them to construct the basic structure or function of the product, so that the parts used can be shared between different types of products. It is a thing.

[0003] Such a concept has already spread to automobile parts. For example, as a means for driving various doors incorporated in an air conditioner for automobiles, a unitized electric actuator as shown in FIG. Some use.

As shown in FIG. 1, a motor 4 for driving and a motor 4 for deceleration are provided in a casing 1 which is divided into an upper case 2 (upper casing) and a lower case 3 (lower casing). Gears 5, 6, and 7,
Output shafts 8 are provided respectively.

[0005] The motor 4 has a main body fixed to the lower case 3 and a worm wheel 9 attached to a drive shaft.
Are adapted to mesh with the gear 5.

The gears 5, 6, 7 are gear shafts 10, 11, 1 formed so as to protrude integrally with the lower case 3.
2 are loosely inserted into each other so that each tooth meshes. As shown in FIG. 4, the gear shafts 10, 11, and 12 are adapted to be fitted into a supporting portion 16 formed such that an end protrudes integrally with the upper case 2. By fitting the gear 2, the respective gear shafts 10, 11, 12 are fixed by the support portion 16 of the upper case 2, and the gears 5, 6, 7 are rotatably supported. FIG. 4 is a sectional view showing a state in which the gear 7 is supported by the gear shaft 12, but the other gears 5 and 6 are also rotatably supported.

The gears 5, 6, 7 and the gear shafts 10, 1
Grease is applied to the contact surfaces 1 and 12 in order to improve slidability.

The output shaft 8 is attached to the lower case 3 such that the gear 13 integrally formed with the output shaft 8 meshes with the gear 7.

Thus, the rotational force of the drive shaft of the motor 4 is
The power is transmitted to the output shaft 8 via the worm wheel 9, the gears 5, 6, 7, and the gear portion 13, whereby various doors connected to the output shaft 8 are rotated.

A board 14 for electrically detecting the rotational position of the output shaft 8 is attached to the lower case 3, and an electric signal indicating the rotational position is provided to one end of the substrate 14. And a connector 15 for outputting power to the motor 4 and inputting power to be supplied to the motor 4. As a result, an external controller for controlling air conditioning
The drive control of the motor 4 can be performed while detecting the rotation position of the output shaft 8, that is, the rotation position of the door via the reference numeral 5.

Therefore, such an electric actuator has a function of detecting the rotational position of a door connected to the output shaft 8 and a function of driving the door. The actuator can be used in different types of automobiles, which contributes to improving productivity.

[0012]

However, since the electric actuator unitized as described above is considered as a single component as described above, it is required to improve the durability and reliability as a whole. .

However, in the above-described conventional electric actuator, since the surfaces (bearing surfaces) of the bearings 17 of the gears 5, 6, 7 are straight surfaces, the gears 5, 6, 7 are not provided.
The grease applied to the contact surfaces of the gear shafts 10, 11, and 12 tends to flow out to other parts (so-called grease running), and there is a certain limit in terms of abrasion resistance. this is,
Due to the rotational movement of the gears 5, 6, 7, in particular the gears 5, 6, 7
This is because centrifugal force acts on the grease interposed in the gaps (play) between the gears and the gear shafts 10, 11, and 12, so that the grease flows out to the surfaces of the gears 5, 6, and 7 and scatters around.

Further, since the bearing surfaces of the gears 5, 6, 7 are straight as described above, the gear shaft becomes longer,
When a large load is applied to the gears 5, 6, and 7, the gear shafts 10, 11, and 12 that receive the load are easily bent, and there are certain limits in terms of accuracy and strength.

The present invention has been made in view of the above problems in the gear mounting structure of the electric actuator, and has been made.
In addition to improving the grease holding capacity interposed in the gap between the gear and the gear shaft, and improving the wear resistance of the sliding part,
An object of the present invention is to provide an electric actuator capable of improving the strength and accuracy of a gear shaft with respect to a load applied to a gear.

[0016]

According to a first aspect of the present invention, a drive motor is provided in an upper and lower casing, and the motor is protruded from one of the upper and lower casings and is fixed by the other casing. A gear loosely inserted into the gear shaft, and an output shaft, transmitting the torque of the motor to the output shaft via the gear, and driving an external driven member connected to the output shaft. In the electric actuator to be driven, a step portion is provided at an end of the gear bearing portion on the other casing side,
A gear shaft fixing portion protruding from the other casing is loosely fitted to the step portion, and a grease reservoir is formed in a gap between a side wall of the step portion and a surface of the gear shaft fixing portion.

According to the present invention, the gear is such that the gear is loosely inserted into a gear shaft protruding from one casing, and the gear protrudes from the other casing to a step provided in a bearing portion of the gear. By loosely fitting the shaft fixing portion, the shaft fixing portion is rotatably supported (a two-stage bearing structure), and a grease reservoir is formed in a gap between the side wall of the step portion and the surface of the gear shaft fixing portion. That is, since the grease reservoir is formed by providing a step portion in the bearing portion of the gear, the grease is prevented from moving due to centrifugal force on the side wall of the step portion even when the gear rotates, so that the grease does not easily flow out. Is provided. In addition, the length of the gear shaft portion that slides with the gear is shorter than that of the gear having no step, and the gear shaft is less bent when the gear receives a load.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a gear mounting structure of an electric actuator according to an embodiment of the present invention, and FIG.
FIG. 2 is an external view of a gear used in the gear mounting structure. Here, the members other than the gear and the mounting structure thereof are the same as the members constituting the conventional electric actuator, and therefore, description thereof will be omitted. FIG. 1 shows, for simplicity, as an example, the case where the gear 7 described in the related art and the gear mounting structure of the present invention are applied to the gear shaft 12 supporting the same. , 6
It goes without saying that the present invention can be similarly applied to the gear shafts 10 and 11.

In this gear mounting structure for an electric actuator, a step 20 is formed at an end (upper end) of the bearing 17 of the gear 7 on the upper case 2 side. The bearing portion 17 of the gear 7 has a shape of a through hole, and the step portion 20 has a counterbore (borebore) shape formed concentrically with the center axis of the bearing portion 17. The step portion 20 has an inner diameter larger than that of the bearing portion 17 and is formed at an appropriate predetermined depth. The depth of the step portion 20 is set to a value smaller than the height of the tooth portion having the larger diameter in order to secure a certain strength. Also,
The bottom surface of the step portion 20 is formed to be orthogonal to the center axis of the bearing portion 17 and to be flat. The gear shaft 12 projecting from the lower case 3 is loosely inserted into the bearing 17 of the gear 7.

That is, the step portion 20 has substantially the same shape as that formed when a so-called boring process, which is a kind of cutting process, is performed, and the side wall 21 is formed parallel to the center axis direction of the gear 7. Have been. Here, the gear 7 is formed by injection molding using a resin material such as POM (polyacetal).
Although it is not formed by boring, it is needless to say that the same shape can be formed by boring.

Since the gear 7 is formed by injection molding as described above, the end 22 of the bottom surface of the step portion 20 is curved to avoid stress concentration.

On the other hand, the gear shaft 12 is, as in the prior art,
It protrudes from the lower case 3 and is formed integrally therewith.

The end portion 23 of the gear shaft 12 projects from the upper case 2 and is formed integrally with the support portion 2.
4 (a gear shaft fixing portion), and the center axis of the fitting hole 25 is the center axis of the gear shaft 12 when the upper case 2 is attached to the lower case 3. It is formed so as to match. Therefore, the gear shaft 12 is fixed by fitting the end 23 of the gear shaft 12 into the fitting hole 25 of the support portion 24.

The support portion 24 of the upper case 2
Has a predetermined gap (play) with respect to the stepped portion 20 and has a cylindrical shape that fits (freely fits). Specifically, the size of the gap is, for example, 0.05 mm to 0.1 mm. This gap becomes the grease reservoir G. This gap has the same size as the gap between the gear shaft 12 and the bearing 17 of the gear 7.

The protruding end 26 of the supporting portion 24 of the upper case 2 is opposed to the bottom end 22 of the step 20 formed as a curved surface, so that a tapered surface is formed.

Even in the case where the gear 7 is mounted as described above, the electric actuator can be assembled in the same manner as in the prior art.

First, when the gear 7 is loosely fitted to the gear shaft 12, the stepped portion 20 of the gear shaft 12 and the gear 7 is used.
Grease is applied to each surface of the gear 7, and the gear shaft 12 is inserted into the bearing 17 of the gear 7 to rotatably support the gear 7 on the gear shaft 12.

Thereafter, after the other parts are assembled into the lower case 3, the upper case 2 is attached to the lower case 3 so that the gear shaft 12 is fixed to the support portion 24 of the upper case 2 as shown in FIG. And
In addition, the support portion 24 is loosely fitted to the step portion 20 of the gear 7 (a so-called two-stage bearing structure). At this time,
The grease is interposed in the gap between each sliding portion, that is, the surface of the support portion 24 and the gear shaft 12 of the upper case 2 and the surface of the step portion 20 and the bearing portion 17 of the gear 7. In particular, the side wall 21 of the step portion 20 and the support portion 24
Since the gap with the surface is relatively large, it functions as a grease reservoir G.

Therefore, the grease interposed in each gap has a grease reservoir G formed in the gap between the step portion 20 and the support portion 24.
Movement due to the centrifugal force is suppressed on the side wall 21 of the main body. As a result, the ability to retain grease interposed in the gap between the gear 7 and the gear shaft 12 is improved as compared with the conventional one having no stepped portion, and the amount of grease scattered can be reduced. The parts are less likely to be worn, and the durability or the life of the electric actuator can be improved.

Further, due to the drastic reduction in the amount of grease consumed (scattered amount), it is difficult to produce a frictional sound even after a long time.
It also contributes to noise reduction.

Further, since the grease holding ability is improved as described above, it becomes possible to lubricate with a smaller amount of grease and to reduce the amount of grease applied as compared with the conventional one having no stepped portion. it can.

The gear 7 is supported by the gear shaft 12 in which the length of the portion of the gear shaft 12 sliding with the gear 7 is reduced by the depth of the step portion 20 as compared with the conventional gear having no step portion. Therefore, the bending of the gear shaft 12 when the gear 7 receives a load is reduced, and the strength of the gear shaft 12 is improved. Therefore, the mounting rigidity is increased as compared with the conventional gear mounting structure, and the reliability of the electric actuator can be improved.

Further, if the strength of the gear shaft 12 is improved and the same strength as the conventional one is sufficient, the material of the gear shaft 12 can be softened, and the molding properties of the material and the resin can be reduced in a short time. Cost can be reduced.

Further, as the deflection of the gear shaft 12 is smaller, the shift of meshing between the gears is reduced. Therefore, various doors (driven members) can be controlled with higher accuracy.

The protruding end 26 of the supporting portion 24 of the upper case 2 is not limited to the above-described tapered surface, but is formed into a curved surface similar to the curved surface of the bottom end 22 of the step portion 20. Of course, it is possible.

Although the case where the gear shaft 12 is fixed by the support portion 24 of the upper case 2 is shown here, the present invention is not limited to this. For example, the gear shaft is fixed by the lower case, or the gear shaft 12 is fixed. Needless to say, it may be one that can be divided at the center.

[0037]

As described above, according to the first aspect of the present invention, the step portion is provided in the bearing portion of the gear to form the grease reservoir, so that a structure in which the grease hardly flows out is provided. The grease holding ability interposed in the gap with the gear shaft is improved, and the durability of the electric actuator is improved. Further, since the bearing has a two-stage structure, the deflection of the gear shaft is reduced, and the strength of the gear shaft is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a gear mounting structure of an electric actuator according to an embodiment of the present invention.

FIG. 2 is an external view of a gear used in the gear mounting structure.

FIG. 3 is a perspective view showing a configuration of a conventional electric actuator.

FIG. 4 is a sectional view showing a gear mounting structure of the electric actuator.

[Explanation of symbols]

 2. Upper case (upper casing) 3. Lower case (lower casing) 5, 6, 7 ... Gear 10, 11, 12 ... Gear shaft 17 ... Bearing section 20 ... Step section 24 ... Support section (gear shaft fixing section) G ... Grease reservoir

Claims (1)

[Claims] A driving motor (4) is provided in upper and lower casings (2, 3) and fixed to the other casing (2) by projecting from one of the upper and lower casings (2, 3). Gear shaft (10,11,1)
2) a gear (5, 6, 7) loosely inserted into the gear (2), and an output shaft (8); An electric actuator configured to transmit a shaft (8) to drive an external driven member connected to the output shaft (8), wherein the gear (5, 6, 7) includes a bearing portion (17). A step portion (20) is provided at the end of the other casing (2), and a gear shaft fixing portion (24) projecting from the other casing (2) is loosely fitted into the step portion (20). (20) and the gear shaft fixing portion (2).
An electric actuator characterized in that a grease reservoir (G) is formed in a gap with the surface of 4).