JPH05188819A - Multiple cam device for releasing nip pressure for fixing device - Google Patents

Abstract

PURPOSE:To easily execute the releasing action of nip pressure by light force by driving a roll supporting arm by using a multiple cam member in a heat roll system fixing device which fixes a large-sized paper. CONSTITUTION:In the heat roll system fixing device which is obtained by facing and arranging a heating roll 2 and a pressure roll 3 and which releases the nip pressure by depressing the roll supporting arm 5 supporting the roll 3 by the multiple cam member, the multiple cam member 10 is arranged with respect to the arm 5 and the roll 3 is separated from the roll 2 by rotating the can member 10. The cam member 10 is constituted by combining a small-diameter cam member 11 and a large-diameter cam member 12. Then, a guiding action with respect to the arm 5 is easily executed by connecting the cam surfaces of both cams with respect to the arm 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cam device for releasing a nip pressure between both rolls in a heat roll type fixing device, and more particularly to a fixing device for a large size sheet. , Against the strong spring force,
When releasing the nip pressure, the multiple cam member is rotated a plurality of times, and the nip pressure can be released with a weak driving force by using a member such as a roll support arm guided by the multiple cam member. The present invention relates to a multiple cam device for releasing the nip pressure.

[0002]

2. Description of the Related Art In an apparatus such as an electronic copying machine or a printer for forming a toner image on an image bearing member such as a photosensitive drum using an electrophotographic method, the toner image formed on the photosensitive drum is printed on a sheet. After the transfer, it is fixed through a fixing device to make a copy. As the fixing device, a general heat roll type device is used, and in the heat roll type fixing device, a mechanism for pressing a pressure roll against a heating roll containing a heating source is used. ing. Then, in order to set a nip pressure of a predetermined value between the two fixing rolls, a pressure roll is supported by a spring against a heating roll supported by the frame of the fixing device, and the pressure is applied by the spring. A means for pressing the roll is used.

As the fixing device, for example, Japanese Unexamined Patent Application Publication No. Hei 2
As shown in JP-A-282773, JP-A-64-44967, etc., a device in which a spring for setting the nip pressure and a cam member for releasing the nip pressure are combined is used. There is. A mechanism for turning on / off the nip pressure in the fixing device uses a mechanism configured as shown in FIG. 10. The fixing device 1 includes a heating roll 2 provided with a heating source. It is arranged so as not to have a heating source or to face the pressure roll 3 having a heating source.

In the above-mentioned conventional example, the heating roll 3 is supported by the roll supporting arm 5, and one end of the roll supporting arm 5 is supported by the frame 9 of the fixing device via the fulcrum 6 and the roll is supported. A spring 8 for tension setting is arranged between the other end of the support arm 5 and the support frame 9. Then, the tension of the spring 8 causes the pressure roll 3 to be pressed toward the heating roll 2.

Further, a cam member 7 is arranged in order to release the nip pressure between the both rolls, and the roll supporting arm 5 is fulcrumed by driving the cam member via the cam shaft 7b. 6 is rotated clockwise against the force of the spring 8 to turn the pressure roll 3 into the heating roll 2.
Away from. Only when the fixing operation is performed in the fixing device, the pressing action of the cam member is released and the nip pressure is set by the spring 8.

[0006]

As shown in FIG. 10, when the nip pressure is controlled by using the cam member, the cam member 7 as shown in FIG. 11 is generally used. The cam member 7 has a cam surface 7a between the bottom dead center A and the top dead center B, which has a shape such that the cam operating radius gradually increases, and the roll support is pressed by the cam surface 7a. As the rotation angle of the cam member increases, the arm gradually swings greatly through the fulcrum while countering the force of the spring. When the cam member shown in FIG. 11 is used, the cam operating radius gradually increases with respect to the rotation angle of the cam member, and the operation starting point from the bottom dead center A in FIG. Between C, the cam member 15 is set in the non-actuated state,
During the period from point C to point D, the operating radius of the cam changes in a substantially linearly increasing direction.

However, since the operation of pushing down the roll support arm is performed against the force of the spring by rotating the cam member, in proportion to the length of extension of the spring, There is a problem that the torque for driving the cam member increases. When the cam member is used, the driving torque increases in the form of a quadratic curve as the turning radius of the cam increases. The increase in the turning radius of the cam member and the increase in the driving torque of the cam mean that the force of the spring is not large in a fixing device provided in a relatively small electronic copying machine. Even if a motor or the like having a relatively weak driving force is used, it is possible to easily deal with it.

However, it is necessary to set the nip pressure of 100 kgf to 300 kgf in an electronic copying machine for copying a drawing or the like using a large size paper such as A0 size. In such a large fixing device, the pressing force of the pressing member is pushed down by the cam member against the force of the spring that gives the strong nip pressure. It is necessary to Then, in order to drive the cam member, it is necessary to configure a driving motor, a shaft member of the cam member, and the like. For example, when a motor having a relatively small capacity is used, the reduction gear mechanism becomes large. The problem occurs. Further, since other mechanisms attached to the drive mechanism, the support frame, and the like are also formed to have a large strength, the influence on the manufacturing cost of the device becomes very large.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional nip pressure releasing mechanism, in which the force for driving the cam shaft is applied to the cam member for turning on / off the nip pressure. By using a mechanism that multiple cam members are rotated multiple times without using a speed reduction mechanism such as a gear device, by disposing a plurality of cam members so as to be connected in the axial direction so as to prevent a sudden increase. It is an object of the present invention to provide a device capable of simplifying the structure of a drive mechanism.

[0010]

The present invention provides two means.
Two rolls are arranged so as to face each other, and a roll supporting arm that presses a heating roll provided with a heating source so as to set a predetermined nip pressure on the pressing roll and supports the pressing roll. On the other hand, the present invention relates to a fixing device configured to perform a setting operation and a releasing operation of a nip pressure by using a driving means including a multiple cam member and a spring. In the fixing device of the present invention, a multiple cam member used to release the nip pressure in the pressure roll is used.
A plurality of cam members having different cam operating radii are connected in the axial direction, and the adjacent cam surfaces of each of the multiple cam members constitute a portion that coincides in the axial direction with the same working radius; The operation of releasing the nip pressure between both rolls is performed by rotating the multiple cam member a plurality of times. Further, in order to follow the rotation of the multiplex cam member and guide the roll support arm along the cam surface, a mechanism for moving the multiplex cam member in the axial direction is arranged with respect to the roll support arm, It is possible to provide a mechanism for automatically performing the transfer operation at the connecting portion of the cam surface of the cam member.

As described above, by constructing the multiple cam member with a plurality of cam members connected in the axial direction,
By rotating the multiple cam member a plurality of times, the operation of releasing the nip pressure can be easily performed, and by using a drive mechanism such as a relatively small motor, a large spring force can be dealt with. it can. Further, in the multiple cam device for releasing the nip pressure of the fixing device of the present invention,
Since the load applied to the contact portion between the multiple cam member and the roll support arm can be reduced, the configuration of each of these operating members can be simplified, and the wear of the drive member of each member can be reduced. At the same time, it becomes possible to improve durability. When the nip pressure between both rolls of the heat roll type fixing device is set to a very large value, the force that drives the roll support arm against the strong spring force. Since it can be set to be small, the driving device can be made small.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-cam device for releasing nip pressure of a fixing device according to the present invention will be described with reference to the illustrated example. As in the case of the conventional example shown in FIG. 10, the example shown in FIG. 1 has a fixing device 1 and a heating roll 2 in which a heating source is provided.
And the pressure roller 3 having no heating source are arranged to face each other. In the fixing device 1, the heating roll 3 is supported by a roll supporting arm 5, one end of the roll supporting arm 5 is supported by a frame of the fixing device via a fulcrum 6, and a spring 8 is provided at the other end. Are arranged. Then, the force of the spring 8 causes the roll support arm 5 to swing counterclockwise via the fulcrum 6 to press the pressure roll 3 toward the heating roll 2, and a predetermined distance between both rolls. Set the nip pressure of the value to enable the fixing operation.

In order to release the nip pressure between the rolls 2 and 3, a multiple cam member 10 is arranged, and by rotating the cam member via the cam shaft 14, the spring 8 is rotated. The roll supporting arm 5 is swung clockwise through the fulcrum 6 against the pulling force. Then, the pressure roll 3 is separated from the heating roll 2 to release the nip pressure. As shown in FIGS. 2 to 4, the multi-cam member 10 of the present invention has two cam members, a small-diameter cam member 11 and a large-diameter cam member 12, which are axially superposed on a cam shaft 14. It is configured as arranged. Further, a brim member 13 is provided on a side portion of the large-diameter cam so that the arm guided by the cam does not come off. In the embodiment of the multiple cam of the present invention, FIG. 3 is a side view in the YY direction of FIG.
FIG. 4 is shown as a side view in the XX direction of FIG.

As shown in FIGS. 5 and 6, each of the two cam members 11 and 12 constituting the multiple cam member 10 has a shape similar to that of a general cam member. In the small-diameter cam member 11 shown in FIG. 5, a cam surface whose radius of gyration increases linearly linearly is formed between the bottom dead center A and the top dead center G. Also in the large diameter cam member 12 shown in FIG. 6, the bottom dead center H and the top dead center B
Like the case of the small-diameter cam member, a cam surface whose cam radius gradually increases is formed between and. On the cam surfaces of the two cam members, the top dead center G of the small diameter cam member 11 has the same cam radius as the bottom dead center H of the large diameter cam member 12. Further, by moving the roll support arm from the top dead center G toward the bottom dead center H, the pressing action on the roll support arm can be continued.

A multiple cam member 10 constructed by integrally combining the two cam members shown in FIGS. 5 and 6 above.
Constitute a continuous guide surface, as shown in FIGS. Then, the cam surface that operates with respect to the roll support arm that supports the pressure roll reaches the top dead center G from the bottom dead center A of the small diameter cam member 11 to the top dead center G, and then to the large diameter cam member 12. The cam surface is formed in a state of being connected to the top dead center B from the bottom dead center H via the intermediate point I. When the pressing action on the roll supporting arm is performed using the multiple cam member 10 configured as described above, the pressing operation by the cam surface is performed as shown in the graph of FIG. 7.

In the graph of FIG. 7, the horizontal axis shows the rotation angle of the cam shaft, and the vertical axis shows the change of the rotation radius. As shown in the graph, while the multiple cam member 10 makes one rotation for the first time, the roll support arm that supports the pressure roll extends from the bottom dead center A to the start end of the top dead center G. The pressing action is given according to the cam surface whose operating radius changes linearly. Then, while the contact portion of the roll support arm moves from the top dead center G of the small diameter cam member 11 to the bottom dead center H of the large diameter cam member 12, the operating radius does not change, so that the cam surface is in a substantially horizontal state. Maintained by the large diameter cam member 12
In the state of moving to the cam surface of No. 2, until the top dead center B, the operating radius linearly increases according to the cam surface of the large diameter cam member.

Means for moving the roll supporting arm in the direction of the cam shaft is provided for guiding the roll supporting arm in a pressed state with respect to the multiple cam member of the present invention configured as described above. There is a need. Therefore,
For example, as shown in FIG. 8, the roll supporting arm 5 is supported by a screw member 16, and the screw member 16 is used to rotate the motor 1.
It is possible to transfer the roll support arm 5 between the small-diameter cam member and the large-diameter cam member by driving the roll support arm 5 to automatically guide the roll support arm between the two cam members. Is.

Further, as shown in FIG. 8, when a mechanism for moving the roll support arm by using a screw member is used, after the pressure roll in the fixing device is separated from the heating roll, the roll is again moved. When setting the nip pressure, it is necessary to drive the screw member in the reverse direction. Therefore, in that case, for example, a method of rotating the motor at a high speed and directly moving the roll support arm from one cam surface toward the adjacent cam surface of the small diameter may be used. Can be used.

In addition to the method shown in FIG. 8, in the present invention, in order to move the roll supporting arm along the multiple cam members, as shown in FIG. 9, the spring 1 is used.
It is also possible to use a biasing means according to 7. When the moving means of the roll supporting arm shown in FIG. 9 is used,
Since the spring 17 exerts an action of urging the roll support arm 5 toward one side of the shaft, the roll support arm 5 is automatically guided at the transfer portion of the cam surfaces of the two cam members. can do. Further, in the fixing device provided with the moving mechanism, in order to set the nip pressure between both rolls, as means for performing an operation of moving the roll support arm 5 in the opposite direction to the spring 17, For example, a return mechanism such as a solenoid can be used.

As described above, in the fixing device of the present invention, by combining the multi-cam member 10 and the returning mechanism of the roll support arm, the pressure roll can be fixed to the heating roll supported immovably. The operation of releasing the nip pressure can be easily performed from the state of pressing. Then, the pressure roll in a state of being separated from the heating roll is moved toward the heating roll again, and when setting the nip pressure of a predetermined value between both rolls, using an arbitrary returning mechanism, The roll support arm can be returned to the nip position.

The multi-cam device for releasing the nip pressure of the fixing device of the present invention is applied to an electronic copying machine using a large heat roll type fixing device in order to make a copy using a large size paper. And can be easily applied. In the large-sized electronic copying machine, a strong spring is used to set the nip pressure in the fixing device. However, even for such a device, it is easy to use a relatively small drive mechanism with weak force. Can be adapted to.

In the multi-cam member of the present invention, the description has been made on the case where only two cam members are combined, but any number of cam members forming the multi-cam member may be used in combination. You can Then, when a large number of cam members are combined, the top dead center and the bottom dead center of adjacent cam members are formed so as to have the same cam radius, so that the rolls are rolled between the cam members. The support arm can be transferred, and the pressing operation on the roll support arm can be continued. Furthermore, in the case of combining a large number of cam members, it is necessary to cause the multiple cam members to rotate corresponding to the number of cam members in order to release the nip pressure to the roll supporting arm. Becomes

In addition to the above structure, in the multiple cam device for releasing the nip pressure of the fixing device of the present invention, in order to prevent the friction between the roll supporting arm and the multiple cam member from becoming an excessive resistance, for example, multiple A cam follower such as a roll can be arranged on the contact surface of the roll support arm that is pressed against the cam member. Then, by not giving excessive friction between the roll support arm and the multiple cam member, it is possible to perform the rotating operation of the multiple cam member, and prevent the driving force from being excessively consumed. The operation of releasing the nip pressure can be easily performed.

[0024]

As described above, the multiple cam device for releasing the nip pressure of the fixing device of the present invention comprises the multiple cam member in a state in which a plurality of cam members are connected in the axial direction. By rotating the member multiple times,
The operation of releasing the nip pressure can be easily performed. Then, by using a drive mechanism such as a relatively small motor, it is possible to cope with a large spring force. Further, in the multi-cam device for releasing the nip pressure of the fixing device of the present invention, the load applied to the contact portion between the multi-cam member and the roll supporting arm can be reduced. The simplification can be achieved, the wear of the driving member of each member can be reduced, and the durability can be improved. Furthermore, when the nip pressure between both rolls of the heat roll type fixing device is set to a very large value, the force that drives the roll support arm against the force of the strong spring. Since it can be set to be small, the drive device can be made small.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a fixing device of the present invention.

FIG. 2 is a plan view showing a configuration of a multiple cam member of the present invention.

FIG. 3 is a side view taken along line YY of the multiple cam member shown in FIG.

FIG. 4 is a side view of the multiple cam member shown in FIG. 2, taken along line XX.

FIG. 5 is a plan view of a small-diameter cam member that constitutes a multiple cam member.

FIG. 6 is a plan view of a large-diameter cam member that constitutes a multiple cam member.

FIG. 7 is a graph showing the relationship between the rotation angle of the cam member and the working radius.

FIG. 8 is an explanatory diagram of a movement guide mechanism of a roll support arm.

FIG. 9 is an explanatory diagram of another example of the movement guide mechanism of the roll support arm.

FIG. 10 is a side view showing a configuration of a conventional fixing device.

FIG. 11 is a plan view showing a configuration of a conventional cam member.

12 is a graph showing changes in the cam operating radius of the cam member shown in FIG.

[Explanation of symbols]

1 fixing device, 2 heating rolls, 3 pressure rolls, 5 roll support arms, 7 cam members,
8 springs, 10 multiple cam members, 11
Small diameter cam member, 12 Large diameter cam member, 13 Head member, 14 Cam shaft, A / H bottom dead center, B / G
Top dead center, E ・ I midpoint.

Claims (1)

[Claims] 1. A spring mechanism is used to set a predetermined nip pressure for a pressure roll with respect to a heating roll provided with a heating source by arranging two rolls so as to oppose each other. For the roll support arm that supports the pressure roll,
In a fixing device configured to perform a releasing operation of a nip pressure by using a driving means by a cam member, the cam member is a multiple cam member in which a plurality of cam members having different shapes are axially connected. However, in the multiple cam member, the adjacent cam surfaces of the respective cam members form a portion that coincides in the axial direction with the same action radius, and by the operation of rotating the multiple cam member a plurality of times, both rolls are rolled. A multi-cam device for releasing the nip pressure of the fixing device, which is characterized in that the nip pressure is released by the operation.