JPS6362966A - Worm gear transmitting device - Google Patents

Abstract

PURPOSE:To prevent the generation of backlash without a reduction in transmitting efficiency, by meshing first and second worms with a worm wheel, and pressing the second worm against the first worm by means of an elastic connection member. CONSTITUTION:A worm wheel 14 is meshed with first and second separate worms 6 and 8. The second worm 8 is biases in its rotating direction by an elastic connection member 11. With this arrangement, when a load on a driven side is fluctuated to change a rotating speed of the worm wheel 14, a force due to such a change is greatly reduced to be transmitted to the elastic connection member 11. Therefore, a weak spring may be used as the elastic connection member 11, and the generation of backlash may be reliably prevented without a reduction in transmitting efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mechanism for eliminating backlash in a worm gear transmission.

[Conventional technology]

Wheel drive using a worm gear is superior in that it has a large reduction ratio and can provide stable rotation transmission even under load fluctuations. By the way, even in the case of this worm gear, since it is a @car transmission mechanism, bank crash inevitably occurs.In order to eliminate the occurrence of this buff crash, extremely high precision is required in the processing and manufacturing of the worm and worm wheel. However, in order to obtain such a high-precision gear, there are problems in that processing and manufacturing is difficult, takes time, and increases costs.Also, even if such a high-precision gear is used, backlash may occur due to wear. cannot be eliminated.

Here, a case will be described in which the worm gear transmission device is used in a drive system for rotating a drum of a copying machine or the like. Figure 5 shows the change in drum rotational speed when there is a change in the load on the driven side, that is, when paper enters the drum and paper escapes from the drum.The solid line shows the worm gear without bank crash countermeasures. When a transmission device is used, the broken line indicates the case when a device with banklash countermeasures is used.As shown in Figure 0, when backlash countermeasures are not taken, the paper enters and escapes more easily than when backlash countermeasures are taken. The rotational speed varies greatly over time, and this speed variation leads to disturbances in the formed image.

Therefore, to prevent the occurrence of backlash in the worm gear as described above, USP 2゜273, 784
There is something shown in The worm gear transmission shown in this figure has a worm connected in two parts in the center as shown in Figure 4.
One worm 30 is fixed to the drive shaft 31, the other worm 32 is supported movably in the axial direction of the drive shaft 31, and these two worms 30 and 32 are integrated with the drive shaft 31. It is designed to rotate. An extensible spiral spring 33 is fitted between the two worms 30 and 32 of the drive shaft 31. A worm wheel 34 is meshed with the worm 30, 32, one side 35 of the teeth of the worm wheel 34 is in contact with the teeth of a fixed worm 3o, and the other side 36 of the teeth of the worm wheel 34 is in contact with the worm 30, 32. The teeth of a worm 32 movable in the axial direction are pressed by a spiral spring 33 and are in contact with the worm 32 .

In this way, the teeth of the two divided worms 30 and 32 are simultaneously brought into contact with both side surfaces of the teeth of the worm wheel 34 by the spiral spring 33, thereby eliminating backlash.

[Problem that the invention seeks to solve]

However, the above-mentioned worm gear transmission has the following problems.

t In other words, bank lash is removed by moving one of the two worms in the axial direction using a spring and pressing it against the worm wheel, but the direction in which this movable worm moves is The direction of rotation of the worm wheel is a problem. Therefore, the structure is such that changes in the rotational speed of the worm wheel due to changes in the load on the worm wheel side (that is, the driven side) are directly applied in the direction of deformation of the spring that biases the worm to move in the axial direction. It becomes. Therefore, the spring may expand or contract due to changes in the rotational speed of the worm wheel, which may cause backlash.

In order to prevent this, it would be best to use a strong spring so that it does not fluctuate due to changes in wheel speed, but if the spring force is made too strong, the transmission efficiency will decrease due to the resistance (masatsuka). A strong spring has the problem that the wire diameter or spring diameter becomes thick, so it is not possible to make the spring very strong.

This invention was made with attention to the above-mentioned problems, and uses a weak spring to prevent the backlash caused by the change in the rotational speed of the wheel when the load on the wheel changes. It is an object of the present invention to provide a worm gear transmission device which can reliably prevent this, without reducing transmission efficiency, and which has a simple and compact mechanism.

[Means and operations for solving the problems] In order to achieve the above-mentioned objects, the present invention takes the following measures.

In this device, two worms are provided on the drive shaft, a first worm fixed to the drive shaft and a second worm rotatably provided, and a worm wheel is arranged so as to mesh with these two worms. It is arranged. and,
An elastic connecting member is provided between the second worm and the drive shaft, and the elastic connecting member biases the second worm in the rotational direction with respect to the drive shaft, and this biasing force rotates the worm wheel. energize.

The rotationally biased worm wheel is pressed against the first worm to eliminate backlash between the worm wheel and the worm.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1st
1 is a perspective view showing a first embodiment of a worm gear transmission according to the present invention, and FIG. 2 is a partial sectional view of this embodiment. As shown in FIG. 0, a worm 2 is inserted into a drive shaft 1.

The drive shaft 1 is rotatably supported by a support frame 4 via a bearing 3. The worm 2 above is the drive shaft 1
A first worm 6 and a drive shaft 1 fixed by a pin 5 to
A second worm 8 is rotatably inserted through a bearing 7 and is divided into two parts. The second worm 8 has one end in contact with the first worm 6, and the other end is a connecting ring 1 fixed to the drive shaft 1 by a pin 9.
0, the second worm 8 is prevented from moving in the axial direction with respect to the drive shaft 1 (it is provided so that it can move only in the rotational direction. Furthermore, this second worm 8 is connected by a wire spring 11 as an elastic connecting member. The wire spring 11 is connected to the ring 10. One end of the wire spring 11 is wound around a pin 12 attached to the second worm 8, and the other end is wound around a groove 13 provided in the axial direction on the circumferential surface of the connection ring 10. The first worm 6 and the second worm 8 are fitted together, and a force is applied so that the second worm 8 rotates in the same direction as the rotational direction a of the drive shaft 1.
The worm wheel 14 is engaged with the worm 8 of
is installed. The left side surface 16 of the teeth of the first worm is in contact with the right side surface 15 of the teeth of the worm wheel 14,
The right side surface 18 of the teeth of the second worm 8 , which is urged to rotate by the wire spring 11 , is pressed against the left side surface 17 of the teeth of the wheel 14 . By sandwiching the teeth of the worm wheel 14 from both sides with the teeth of the two worms 6.8 thus divided, backlash is made zero. and,
The first worm 6 and the second worm 8 rotate integrally with the drive shaft 1 in the direction of arrow a, and the second worm 8 presses the worm wheel 14 against the first worm 6. The worm wheel 14 is rotated in the direction indicated by the arrow at a reduction ratio of 1/100.

Next, the operation of the device configured as described above will be explained. An end of the drive shaft 1 is connected to a motor (not shown), and the drive shaft 1 is rotated in the direction of arrow a by this motor. As the drive shaft 1 rotates, the first. A second worm 6.8 rotates integrally, and this second worm 8 operates as a driving worm that rotates the worm wheel 14 in the direction indicated by the arrow. The second worm 8 biased in the rotational direction by the wire spring 11 presses the worm wheel 14 against the first worm 6 to eliminate backlash.

Here, if the rotational speed of the worm wheel 14 changes due to a change in the load on the worm wheel 14, which is the driven side, this change in speed may cause backlash as in the conventional example. However, when the rotational speed of the worm wheel 14 is about to become faster than the speed at which it is rotated by the drive shaft 1, the force that causes the wheel 14 to rotate is applied to the first worm 6; Since it is fixed to the drive shaft 1, the rotation of the wheel 14 is locked and cannot become faster, so bank crash does not occur.Also, when the rotation speed of the worm wheel 140 tries to slow down,
A force acts in the direction opposite to the rotational direction of the wheel 14 (the direction of the arrow), and a force tries to push the second worm 8 back in the axial direction. Since the second worm 8 moves only in the direction of rotation and not in the direction of rotation, the force pushing back the second worm 8 is significantly reduced in proportion to the 4-speed reduction ratio. Furthermore, the second worm 8 is a wire spring 11
Since a force is applied in the rotational direction so as to press the worm wheel 14, a force is generated that is strong enough to rotate the second worm 8 against the force of the linear spring 11 and push it back. Since there is no backlash, no backlash occurs.

In this way, the force generated by the change in the rotational speed of the worm wheel 14 due to the change in the load on the driven side is
Backlash that causes the worm 8 in the rotational direction does not occur.

FIG. 3 is a partial sectional view showing a second embodiment of the invention. The same parts as in the first embodiment are given the same reference numerals, and details will be omitted. The difference between this second embodiment and the first embodiment is that, in the first embodiment, a drive shaft is provided on the downstream side of the part where the worm 2 and the wheel 14 mesh along the rotational direction of the wheel 14. The arrangement of the fixed first worm 6 and the rotatable second worm 8 provided on the upstream side is reversed, and the first worm 19 is provided on the upstream side and the second worm 20 is provided on the downstream side. The point is that And the first
The second worm 19 rotates the worm wheel 12 in the direction indicated by the arrow, and the second worm 20 is applied with a rotational force in the direction opposite to the rotational direction of the drive shaft by the wire spring 21 so as to come into contact with the first worm 20. The teeth of the wheel 12 are sandwiched between the teeth of the wheel 12 in cooperation with the worm 19 .

With this configuration, the action of the worm on changes in wheel rotational speed due to changes in load is opposite to that in the first embodiment. That is, in this embodiment, the force due to a change in the rotational speed of the wheel is applied to the fixed first worm 19 when the rotational speed becomes slow, but this first worm 19 is fixed to the drive shaft 1. Therefore, no backlash occurs due to movement of the worm in the axial or rotational direction.

On the other hand, when the rotation speed of the wheel 14 increases,
The rotational force of the wheel 14 is applied in a direction that moves the rotatable second worm 20 in the axial direction. However, the second
Since the worm 20 can only be moved in the rotational direction and not in the axial direction, the force that attempts to move the worm in the axial direction is converted into a force that rotates the worm and the second worm 20 is moved.
It is greatly reduced due to the application to the wire spring 11, does not deform the wire spring 11, and no backlash occurs.

In this way, in the second embodiment as well, as in the first embodiment, backlash of the worm gear transmission device due to changes in the rotational speed of the wheel due to changes in load can be almost eliminated.

In the above embodiment, bank lash is removed by sandwiching the teeth of the worm wheel between the first worm and the second worm. The backlash may be removed by opening it up and coming into contact with the teeth of the worm wheel.

Further, in the above embodiment, a wire spring is used as the elastic connecting member for connecting the rotatable second worm to the drive shaft, but a temporary spring, a torsion spring, etc. may also be used. Furthermore, although a cylindrical worm is used in the embodiment, a drum-shaped worm like the conventional example may also be used.In short, any type of worm that applies rotational force to the drive shaft may be used. be.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

〔Effect of the invention〕

As explained above, according to the present invention, the second worm, which is movably provided with respect to the drive shaft, does not move in the axial direction, but is biased only in the rotational direction by the elastic connecting member. The force caused by changes in the rotational speed of the worm wheel when the side load fluctuates is greatly reduced through the worm gear connection mechanism and is applied to the elastic connection member, allowing the use of weaker springs and reducing transmission efficiency. (The occurrence of backlash can be reliably prevented, and the mechanism is simple and the device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a first embodiment of the present invention;
The figure is a partial sectional view of the first embodiment, FIG. 3 is a partial sectional view of the second embodiment, and FIG. 4 is a partial sectional view of the conventional example. FIG. 5 is a graph showing changes in the rotational speed of the drum due to changes in the load on the drum when the worm gear transmission device is used in the drive system of the drum of a copying machine or the like. 1-.-Drive shaft 6, 19-.First worm 8
, 20--Second worm 11, 21...-Wire spring (elastic connection member) 14--
・Worm wheel 14: Two ohm wheel Figure 2

Claims (1)

[Claims] A drive shaft, a first worm fixed to the drive shaft, a second worm rotatably provided to the drive shaft, and elasticity for elastically connecting the drive shaft and the second worm. The worm wheel is composed of a connecting member and a worm wheel arranged to mesh with a first worm and a second worm, and the second worm is biased in the rotational direction by the elastic connecting member to cause the worm wheel to rotate. A worm gear transmission device characterized in that backlash is eliminated by pressing against and abutting a first worm.