JPH10132037A - Mechanism for eliminating worm gear backlash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized drive mechanism with a low power consumption and a low cost which can perform a high precision angular positioning without producing jointing of the screen in a security purpose camera universal head. SOLUTION: At the step part of three pins with step which are planted on a base on which is mounted a worm wheel, a worm bearing holder 9 which holds a worm 11 is positioned in the direction of a worm wheel bearing one of the three pins shall be a fulcrum pin and disposed on the tangent line of the meshing point between the worm wheel 1 and worm 11, the clearance between the fulcrum pin and a fulcrum hole 10 of the worm wheel bearing holder 9 shall be small and the clearance between the remaining two holes and a hole 10 of the worm wheel bearing holder 9 shall be large so that a spring 20 impart force to the worm wheel bearing holder 9 to press the worm 11 against the worm wheel 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlash removing mechanism for a worm gear for driving a pan / tilt head used in a security surveillance camera.

[0002]

2. Description of the Related Art Conventional security surveillance cameras require a camera to be turned in horizontal (pan) and vertical (tilt) directions so as to monitor a predetermined field of view by remote control or preset. Worm gears are often used. Worm gears have a large reduction ratio and can transmit a large rotation angle of the motor to a small rotation angle of the camera, so that precise angular positioning can be performed. In order to maintain the camera angular position even if the camera is cut off, it is often used for camera heads.

However, since the worm gear mechanism has a backlash, the camera is rattled by the amount of the backlash after the camera is positioned at a predetermined angular position as it is, and the television screen shakes. In order to prevent this, a backlash removal mechanism that presses the worm against the worm wheel is often used.However, the torque of the motor that drives the camera to rotate turns the force that presses the worm against the worm wheel and the force between the worm and the worm wheel. It is very sensitive to the occlusal position, and the movement guide for pressing the worm that has been used conventionally is a sliding guide between planes, and the frictional force changes because the contact situation between the planes changes slightly each time it is assembled. Variations, it is difficult to press the worm wheel with a constant force at a constant pressure, and therefore a large force may be applied to the motor.Therefore, a motor with a large torque is required, miniaturization, low power consumption, and cost reduction. Had become a bottleneck.

[0004]

As described above, in the prior art, when the worm is pressed against the worm wheel, the contact point of the moving guide is not stable, so that the sliding frictional force is not constant, and therefore the pressing force and the occlusal force are reduced. The point is not fixed, the adjustment is troublesome, and the variation at the time of adjustment is large, so a motor with a large torque is required, the size is large, the power consumption is large, and the cost increases including the time required for adjustment. Had.

[0005]

SUMMARY OF THE INVENTION The present invention eliminates these drawbacks so that the contact state of the movement guide of the worm pressing mechanism is always constant so that the frictional force is constant and the worm pressing force is also constant. It was done.

As a guide for the worm pressing mechanism, three stepped pins are fixed to a base on which a worm wheel bearing is mounted. One of the three pins is provided as a fulcrum pin on a tangent line from a point where the worm meshes with the worm.

In the worm bearing holder to which the worm is mounted, a fulcrum pin is provided with a clearance hole which can rotate smoothly as a fulcrum and does not cause blur of the camera screen, and has two other pins. Is provided with a hole having a clearance which does not prevent the rotation movement about the fulcrum pin which presses the worm against the worm wheel.

In the axial direction of the three pins, the shoulder of the hole of the worm bearing holder is pressed against the step of the pin so as to position the worm in the worm wheel axial direction.

A spring for pressing the worm and the worm wheel is provided between the worm bearing holder and the base.

[0010] In this manner, the movement when pressing the worm against the worm wheel is applied as a rotational movement about the fulcrum pin by a spring, and the axial movement of the worm wheel during the rotational movement is guided by three pins. The stepped part of the worm and the shoulder of the worm bearing holder hole are guided at three points. Therefore, even if there is a rotational movement around the pin, the three points always contact, and the contact point fluctuates. And the worm pressing force is constant.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3 and 4. FIG. FIG. 1 is a plan view of one embodiment of the present invention, and FIG. 2 is a side view of FIG. 1 and 2, a worm wheel 1 is a worm wheel bearing 2,
It is rotatably fixed to the base 4 via the housing 3. The base 4 has a pin 6 having a step 5 and three screws 8
Has been fixed by.

A washer 7 is fastened to the upper part of the pin 6 by a screw 8. The three pins 6 are fitted with three holes 10 and 10 'of the worm bearing holder 9, and the fulcrum holes 10 are provided on the worm wheel 1 as shown in the enlarged view of FIG.
Pin 6 on the tangent to the occlusal point 12 with the worm 11
And the other two guides 10 'have a hole diameter of 10 .mu.m between them, as shown in the enlarged view of FIG.
It has a hole diameter to form a gap of 0 μm. Further, a wave washer 13 is inserted between the worm bearing holder 9 and the washer 7 in the holes 10 and 10 ′, and the worm bearing holder 9 is pressed against the step 5 of the pin 6.

The worm bearing holder 9 has a worm bearing 1
4 and a motor 15 are mounted. The motor 15 incorporates ball bearings 16 and 16 ′ and a preload spring 17. Further, a worm 11 is fitted to a motor shaft 18 and fixed with a set screw 19, and the worm 11 is substantially fixed. And motor shaft 18
And are integrated. Worm bearing 14 and ball bearing 1
The worm 11 supported by the worm wheels 6, 16 ′ is positioned in the axial direction of the pin 6 by the step 5 and the worm bearing holder 9 so that the center of the worm 11 just meshes with the center of the teeth of the worm wheel 1. Have been.

Further, a force is applied to the worm bearing holder 9 in a direction in which the worm 11 is pressed against the worm wheel 1 by a spring 20.

The worm wheel 1 is further connected to a television camera 22 via a shaft 21.

In this operation, when the motor 15 is driven via a control unit (not shown), the motor shaft 18 rotates, and the worm 11 integrated therewith also rotates.

At this time, the worm 11 is the worm wheel 1
Is pressed by the worm wheel 1 while being positioned by the step portion 5 of the pin 6 and positioned by the ball bearing 16, the pin 6 and the holes 10, 10 ′ in the axial direction of the worm 11. The frictional resistance when pressed is the sliding resistance between the pin 6 and the fulcrum hole 10 and the sliding resistance between the step 5, the worm bearing holder, and the wave washer 13. It is almost zero because of having, and also in the case of the step portion 5 and the worm bearing holder 9, the force for weakly pressing with the wave washer 13 because the bearing holder 9 does not float up from the step portion 5 when pulled by the spring 20. Multiplied by the coefficient of friction (up to 0.2). Further, in order to reduce the sliding resistance, the wave washer 13 is removed, and the friction between the washer 7 and the step portion 5 is reduced to almost zero by setting the dimension between the washer 7 and the step portion 5 to about 30 μm of the thickness of the bearing holder 9. It is also possible. In this case, the axial direction of the worm wheel 1 is 30.
Although a contact error of μm occurs, it is sufficiently acceptable.

Since the frictional resistance of the guide portion can be made very small in this manner, the force for pressing the worm 11 against the worm wheel 1 can be slightly adjusted.

[0019]

According to the worm gear reducer, in order to prevent backlash, when the pressing force increases when the worm is pressed against the worm wheel, the frictional force of the worm gear becomes very large, and a large driving force is required. Although abnormal wear is caused, in this embodiment, there is no fear of such wear, and the drive can be performed with a small driving force without backlash. Accordingly, the television camera 22 can be positioned at an arbitrary angular position without backlash with a small driving force of the motor 15.

As described above, according to the present invention, since the pressing force of the worm can be kept constant with a simple structure and no particular fine adjustment is required, it can be driven by a motor having a small power, and has a small size, low power consumption and high precision. The camera head can be constructed quietly and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a side view of FIG. 1 showing one embodiment of the present invention;

FIG. 3 is a partially enlarged view showing an embodiment of the present invention.

FIG. 4 is a partially enlarged view showing an embodiment of the present invention.

[Explanation of symbols]

1: worm wheel, 4: base, 6: pin, 7: washer, 9: worm bearing holder, 10: fulcrum hole, 10 ':
Guide holes, 11: worm, 14: worm bearing, 2
0: Spring.

Claims (1)

[Claims] 1. A worm wheel, a worm wheel bearing that supports the worm wheel, a base to which the worm wheel bearing is fixed, a worm that meshes with the worm wheel, and a worm that rotatably supports the worm. A worm bearing for positioning the worm bearing so as not to move in the axial direction of the worm, a worm bearing holder for holding the worm bearing, a rotatably supporting the worm bearing holder without looseness, and rotation of the bearing. A fulcrum pin that is axially positioned at a fixed position, and is fixed on a tangent line passing through a worm bite of the worm wheel on the base, and is fixed on the base and cooperates with the fulcrum pin on the base. The worm bearing holder is positioned at three points in the axial direction of the fulcrum pin, and the clearance of the worm wheel bearing holder is By fitting into a certain hole, two pins that do not prevent rotation for backlash removal around the fulcrum pin of the worm wheel bearing holder and the worm are pushed to the worm wheel via the worm bearing holder. A worm gear backlash removing mechanism, comprising a spring to be attached.