JPH0642594A - Gear transmission mechanism - Google Patents

Abstract

PURPOSE:To solve the problems accompanied by the backlash of the gear with as simple constitution by using the combination of two helical gears. CONSTITUTION:A driving gear 3 and a driven gear 4 are integratedly constituted by arranging two helical gears 3A, 3B; 4A, 4B respectively so that the helical direction of the teeth for both groups may be opposite to each other, and at the same time, the driving gear 3 and the driven gear 4 are engaged with each other so as to constitute two gear rows, and one of two gear rows has the tooth contact in the forward direction while the other has the tooth contact in the reverse direction, and a driving shaft 1 to fix the driving gear 3 and a driven shaft 2 to fix the driven gear 4 are pivotably supported in an axially movable manner respectively and slightly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear transmission mechanism which eliminates the influence of backlash.

[0002]

2. Description of the Related Art As is well known, a gear is provided with a backlash so that the gearwheel can be smoothly rotated without causing a wedge action in meshing the gears. That is, no matter how precision machining is performed on the gear, an unavoidable machining error occurs, so that smooth operation is theoretically impossible without backlash.

In a power transmission system such as an industrial robot whose rotation direction is frequently switched between forward and reverse, since gears have backlash, each time the rotation direction is switched back and forth, a corresponding amount of backlash occurs. There is a problem that the rotation delay occurs. To prevent this, the backlash should be reduced, but due to the existence of the above-mentioned unavoidable processing errors, the smaller the backlash, the greater the vibration and noise during high-speed rotation. After all, these problems have been regarded as problems that cannot be solved as long as there is an unavoidable processing error.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems associated with gear backlash with a simple structure by utilizing a combination of two helical gears. It is to provide a transmission mechanism.

[0005]

SUMMARY OF THE INVENTION In the present invention for achieving the above object, a driving gear and a driven gear are coaxially arranged from two helical gears so that their helical directions are opposite to each other. In addition to the above, the driving gear and the driven gear are meshed with each other so as to form two gear trains, and one of the two gear trains has a tooth contact in the forward rotation direction, while the other has a reverse rotation. It is characterized in that the driving shaft for fixing the driving gear and the driven shaft for fixing the driven gear are respectively rotatably supported by a slight amount so as to be axially movable.

By combining two helical gears for each of the driving gear and the driven gear, a gear train transmitting power and a gear train not transmitting power are simultaneously formed, and the gear train not transmitting the power. By automatically setting the tooth contact of the machine so that it is free from vibration and noise during high speed rotation due to machining error.
Further, when the motor is operated by alternately rotating it in the forward and reverse directions, the rotation delay is not substantially generated by switching the power transmission path when switching the rotation direction.

[0007]

1 and 2 show an example of the present invention, showing a case where the structure is used as a control speed change mechanism for an industrial robot. In the figure, 1 is a drive shaft and 2 is a driven shaft. The drive gear 3 is fixed to the drive shaft 1, while the driven shaft 2
The driven gear 4 is fixed to. Drive shaft 1 and driven shaft 2
Are rotatably supported by bearings 5 and 6 so as to allow a slight amount of axial movement. When these bearings 5 and 6 are ball bearings for small horsepower, for example, an axial movement of about 15μ can be permitted.

The driving gear 3 and the driven gear 4 have two helical gears 3A, 3B; 4A, 4B coaxially arranged, and the helical directions of their teeth are opposite to each other with respect to a plane orthogonal to the axis. It is integrally fixed by a bolt 7 so as to face the direction. The driving gear 3 of the helical gears 3A and 3B and the driven gear 4 of the helical gears 4A and 4B form two gear trains and mesh with each other, and as shown in FIG. 3, the gears of the helical gears 3A and 4A. While the example shows tooth contact in the forward direction F, helical gears 3B, 4B
Of the gear trains of (1) and (2) mesh with each other so as to have a tooth contact in the reverse rotation direction R.

In the above structure, the drive shaft 1 and the drive gear 3
Is rotated in the forward direction F, the helical gear 3A of one gear train presses the helical gear 4A on the driven gear 4 side, while the helical gear 3B of the other gear train presses the helical gear 4B. Absent. Moreover, due to the pressing drive of the helical gear 3A of one gear train against the helical gear 4A, an axial component force as indicated by the white arrow is generated between the helical gears 3A and 4A and between the helical gears 3B and 4B. They occur in opposite directions.

Therefore, the drive shaft 1 and the driven shaft 2, which are rotatably supported by the bearings 5 and 6 which allow a small amount of axial movement, perform a small amount of axial movement in mutually opposite directions, whereby the helical gear 4B becomes a helical gear 3B. It follows and rotates while becoming self-reliant. With such an action, the drive gear 3 and the driven gear 4 can perform smooth rotation without generating a vibration or noise in a state substantially free from the influence of backlash and without a wedge action. Further, when the rotation direction is switched to the reverse rotation direction R, the driven gear 4 becomes the driving side and the driving gear 3 becomes the driven side, but the helical gear 4B is in a state where there is substantially no clearance (extremely small clearance). Since the follow-up rotation is performed, the pressing drive can be started without causing a rotation delay with respect to the helical gear 3B.

In the case of driving in the reverse direction R,
Since a component force like a black arrow is generated in the axial direction and the helical gears 3A and 4A side are separated, the same smooth rotation as in the case of the forward rotation direction F can be performed. It is considered that the allowable rotation delay angle when switching the rotation direction should be within 3 minutes from a practical point of view. Now, in the gear transmission mechanism of the present invention, the bearing 5,
6, a ball bearing having an allowable axial movement amount of about 15μ is used, the helix angle α of the helical gears 3A, 3B; 4A, 4B is 15 °, and the diameter D of the driven shaft 2 is 50 mm.
In such a case, if the rotation delay angle is estimated, it can be confirmed by the following simple calculation.

That is, since the total axial movement amount AB of the drive shaft 1 and the driven shaft 2 is 30 μ from the above setting, as shown in FIG. 4, the clearance BC measured in the rotational direction between the helical gears 3B and 4B. The (distance) is BC = AB × tan α = 30 μ × 0.59 = 17.7 μ. Since the diameter D of the driven shaft 2 is 50 mm, the rotation delay angle δ (min) is δ = (BC / 0.5D) × (60 × 180 ° / π) = (0.0177 / 25) × (60 × 180 ° / π) = 2.4 minutes That is, the rotation delay angle δ becomes only about 2.4 minutes,
Actually, from the present situation where generally 3 minutes is allowed, it means that the purpose of substantially causing no rotation delay is achieved. Therefore, as the bearing used in the present invention,
Since a commercially available one can be selected relatively easily, a gear transmission mechanism which is not affected by backlash can be easily obtained with a simple structure. Further, in the present invention, there is also an advantage that the rotation delay angle can be easily calculated and predicted in advance as described above, so that the design can be facilitated. That is, since the rotation delay angle δ is a function of the helix angle α and AB, there is a feature that the above-mentioned effects can be easily obtained by setting these numerical values.

[0013]

As described above, in the gear transmission mechanism of the present invention, the driving gear and the driven gear are each constituted by a combination of two helical gears, so that the power is transmitted in the engagement between the driving gear and the driven gear. The gear train that does not transmit power and the gear train that does not transmit power are formed at the same time, and the tooth contact of the gear train that does not transmit power is automatically separated. Can be prevented from occurring. Further, when the operation is performed while switching the rotation direction in the forward and reverse directions, the rotation delay is not generated by switching the power transmission path when switching the rotation direction.

[Brief description of drawings]

FIG. 1 is a front view showing a gear transmission mechanism according to an embodiment of the present invention.

FIG. 2 is a sectional view of the gear transmission mechanism shown in FIG. 1 taken along the line II-II.

3 is an enlarged view showing an outline of a cross section taken along the line III-III of the gear transmission mechanism shown in FIG.

FIG. 4 is an explanatory diagram of rotation delay due to the gear transmission mechanism of the present invention.

[Explanation of symbols]

1 drive shaft 2 driven shaft 3 drive gears 3A, 3B
Helical gear 4 Driven gear 4A, 4B
Helical gear 5, 6 bearing

Claims (1)

[Claims] 1. A drive gear and a driven gear are integrally formed by arranging coaxially from two helical gears so that the helical directions of both teeth are opposite to each other, and these drive gear and driven gear are combined. The two gear trains are meshed with each other so that one of the two gear trains has a tooth contact in the forward rotation direction and the other has a tooth contact in the reverse rotation direction.
A gear transmission mechanism in which a drive shaft that fixes the drive gear and a driven shaft that fixes the driven gear are respectively rotatably supported by a small amount.