JPH04256640A - Gear device and paper feeder using it - Google Patents

Abstract

PURPOSE:To reduce power loss and noise generation originating from a ratchet wheel device used as a brake device, and maintain a high locational accuracy. CONSTITUTION:The drive force of a motor 3 is transmitted through gear trains 4, 6, 5, and a ratchet wheel 7 is secured to the shaft of a sheet feed roller 2 which is rotated thereby, and a ratchet 9 energized by a torsion coil spring 8 is put in pressure contact with this ratchet wheel 7. An arm 8a provided at the supported end of this coil spring 8 is supported by a rotary cam interlocking with rotation of the ratchet wheel, and the energization force of the coil spring weakens when the ratchet 9 is positioned at a cog crest of the ratchet wheel, while strengthens when positioned at the bottom.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear device, particularly a ratchet device, and a paper feeding device using the ratchet device.

0002

2. Description of the Related Art In recent years, in order to improve paper feeding accuracy, many paper feeding devices have been seen in facsimile machines, printers, etc., which are equipped with a braking device using a ratchet wheel. Hereinafter, a conventional paper feeding device of this type will be explained with reference to FIG.

In FIG. 3, reference numeral 2 denotes a paper feed roller whose shaft is rotatably supported on a base 1, and a large gear 5 is attached to the shaft.
A ratchet wheel 7 integrally formed with the large gear 5 is attached. Reference numeral 3 denotes an electric motor fixed to the base 1, and a small gear 4 is attached to the rotating shaft of the electric motor. Reference numeral 6 denotes an intermediate gear consisting of a two-stage gear consisting of a large gear portion 6a that meshes with the small gear 4 and a small gear portion 6b that meshes with the large gear 5. A pawl 9 is biased by a torsion coil spring 8 so as to come into pressure contact with the ratchet wheel 7.

In such a configuration, when the electric motor 3 is energized and the small gear 4 rotates in the direction of arrow A, the intermediate gear 6
The large gear 5, which is decelerated through the rotation, rotates, and the paper feed roller 2 and ratchet wheel 7 also rotate in the direction of arrow B.

Since the pawl 9 is biased by the torsion coil spring 8, as the ratchet wheel 7 rotates, the pawl 9 swings along the peaks and valleys of its teeth while being in pressure contact with each other. When the electric motor 3 is de-energized, braking is applied when the pawl 9 falls into the valley of the teeth of the ratchet wheel 7, and the paper feed roller 2 is prevented from rotating due to inertia, and the paper is fed at a predetermined position with precision. It will stop often.

[0006]

However, in the above-mentioned conventional structure, a large frictional force is always generated due to the pressure contact of the pawl 9 against the ratchet wheel 7, and as a result, there is a problem in that the power loss of the electric motor 3 becomes large. Furthermore, when the pawl 9 falls into the valley of the teeth of the ratchet wheel 7, a large impact sound is generated and becomes a noise.If the biasing force of the torsion coil spring 8 is weakened in order to reduce the noise, the braking force will also be reduced to the desired level. There was also the problem that it was not possible to obtain paper feeding accuracy.

The present invention solves the problems of the prior art, and provides a paper feeding device that reduces power loss and noise and provides the required positional accuracy, and a gear device suitable for use therein. The purpose is to

[0008]

[Means for Solving the Problems] In order to achieve the above object, the gear device of the present invention includes a ratchet wheel, a pawl urged by an elastic member so as to come into pressure contact with the ratchet wheel, and a mating member of the elastic member. It consists of a rotating cam that engages with the ratchet wheel and changes the pressing force of the pawl against the ratchet wheel in conjunction with the rotation of the ratchet wheel. The cam has a configuration in which the biasing force of the member is weak and the biasing force becomes strong when the member is located in the valley portion.

Further, the paper feeding device of the present invention includes a paper feeding roller, a driving means for rotationally driving the paper feeding roller, and a gear device configured as described above in which a ratchet wheel is fixed to the shaft of the paper feeding roller. be done.

0010

[Operation] According to the above structure, when the pawl is located at the peak of the teeth of the ratchet wheel, the pressing force of the pawl becomes weaker, so the frictional force is reduced accordingly, reducing power loss, and the valley of the tooth. The impact sound when the paper falls down is reduced, and the pressing force of the pawl increases when the pawl is located in the valley of the teeth of the ratchet wheel. Accuracy is also ensured.

[0011]

[Embodiments] Hereinafter, embodiments will be explained in detail based on the drawings. FIG. 1 shows an embodiment of the present invention, in which the same reference numerals as in FIG. This is a rotating cam that changes the pressing force of the pawl 9 against the ratchet wheel in conjunction with rotation. That is, the driving gear 10 of the rotating cam 11 meshes with the large gear portion 6a of the intermediate gear 6, and the cam portion supports the arm 8a at the support end of the torsion coil spring 8. The gear ratio of the drive gear 10 to the large gear portion 6a of the intermediate gear 6 is set so that one rotation of the rotary cam 11 is synchronized with the rotation of one tooth of the ratchet wheel 7.

Next, the operation of this embodiment will be explained. The operation of transmitting the driving force of the electric motor 3 to the paper feed roller 2 is basically the same as in the conventional example shown in FIG. A major feature of this embodiment is that the pressing force of the pawl 9 against the ratchet wheel 7 changes depending on whether the pawl is located at the peak of the teeth of the ratchet wheel or when it is located at the trough.

That is, when the pawl 9 is located at the crest of the teeth of the ratchet wheel 7, the arm 8a at the supporting end of the torsion coil spring 8 comes into contact with the small diameter portion 11a of the rotary cam 11, as shown in FIG. Since they are in contact with each other, the biasing force of the torsion coil spring 8 against the pawl 9 becomes weak, and therefore the pressing force of the pawl 9 is weak. This means that when the pawl 9 climbs over the ridges of the teeth of the ratchet wheel 7, the frictional force becomes smaller, which can reduce the power loss of the electric motor, and when the pawl 9 falls into the troughs of the teeth of the ratchet wheel 7, the frictional force becomes smaller. Since the force is weak, there is no need to make a loud impact sound.

On the other hand, when the pawl 9 is located at the trough of the teeth of the ratchet wheel 7, the arm 8a at the supporting end of the torsion coil spring 8 moves around the circumference of the rotary cam 11, as shown in FIG. Part 1
1b, the biasing force of the torsion coil spring 8 against the pawl 9 is strong, and therefore the pressing force of the pawl 9 is also strong. As a result, when the electric motor 3 is de-energized and the pawl 9 falls into the valley of the teeth of the ratchet wheel 7, a large brake is applied and the paper feed roller 2 immediately stops. Therefore, the paper being fed is always stably and correctly positioned at a predetermined position.

[0015] The means for transmitting the driving force to the paper feed roller is not necessarily limited to a gear train, and other transmitting means such as a belt may be used. Further, the biasing means for pressing the pawl against the ratchet wheel is not limited to a torsion coil spring.

[0016]

[Effects of the Invention] As explained above, according to the present invention,
This provides effects such as reducing power loss and suppressing noise generation without reducing paper feeding accuracy.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a paper feeding device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of the same embodiment.

FIG. 3 is a configuration diagram of a conventional example.

[Explanation of symbols]

2...Paper feed roller, 3...Electric motor, 4...
Small gear, 5... Large gear, 6... Intermediate gear, 7
... Pawl wheel, 8 ... Torsion coil spring, 8a... Arm,
9... Pawl, 11... Rotating cam, 11a...
Small diameter part, 11b...circumferential part.

Claims (2)

[Claims] 1. A ratchet wheel, a pawl urged by an elastic member so as to come into pressure contact with the ratchet wheel, and a pawl that engages with a portion of the elastic member and rotates in conjunction with rotation of the ratchet wheel. a rotating cam that changes the pressing force of the pawl against the ratchet wheel; when the pawl is located at the peak of the teeth of the ratchet wheel, the urging force of the elastic member is weak; when the pawl is located at the trough, the urging force of the elastic member is weak; A gear device characterized by having a cam shape that increases biasing force. 2. A paper feed roller, a drive means for rotationally driving the paper feed roller, a ratchet wheel fixed to the shaft of the paper feed roller, and a ratchet wheel urged by an elastic member so as to come into pressure contact with the ratchet wheel. a pawl, and a rotary cam that engages a portion of the elastic member and changes the pressing force of the pawl against the ratchet wheel in conjunction with the rotation of the ratchet wheel; A paper feeding device characterized in that the cam has a cam shape such that the biasing force of the elastic member is weak when the ratchet wheel is located at the peak of the teeth, and the biasing force is strong when the elastic member is located at the trough.