JPH0125066B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device for a photosensitive drum, which is rotatably mounted on a machine frame and forms an image on its surface by an image forming device.

In electrophotographic copying machines that use a photoreceptor drum, image quality may deteriorate due to dew condensation on the surface of the photoreceptor and the photoreceptor becoming cold, and such deterioration is particularly noticeable in winter and in cold regions. It is.

To solve this problem, a photoreceptor drum heating device has been proposed in which a heater is provided on the shaft of the photoreceptor drum to heat the photoreceptor drum and prevent dew condensation and cooling of the surface. There is.
In this case, heat from the heater is conducted to the photoreceptor through the drum shaft and flanges attached to the drum shaft and supporting the photoreceptor drum on both sides. In the case of a heating device with such a configuration, a temperature difference occurs between the part near the flange and the part far from the flange, which not only makes the temperature distribution on the photoreceptor surface uneven, but also makes it difficult to evaporate condensation. It takes a considerable amount of time to bring the entire surface of the photoreceptor to the desired temperature. Therefore, it is necessary to use a large-capacity heater or to keep the electricity on at all times when not in use, such as at night, to prevent condensation.In both cases, not only does the amount of electricity increase, but in the former case, It was necessary to take measures against the rise in temperature of the bearings and side plates.

In order to improve this problem, a heating device was proposed in which a heat dissipation fin was fixed to a drum shaft with a built-in heater, and the photoreceptor drum was heated from the inside using the heat radiated from the heat dissipation fin. However, the drawback was that the rise time was long.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoconductor drum heating device that eliminates the above-mentioned drawbacks of conventional heating devices, has a uniform photoconductor drum surface temperature distribution, and has a short rise time for the drum surface temperature. do.

Now, there are many ways to heat the surface of the photoreceptor drum. For example, a planar heating element 100, which is considered to be advantageous in shortening the rise time, is formed into a cylindrical shape as shown in FIG. When placed in contact and heated, drum 10
The temperature distribution in the axial and circumferential directions on the surface of 1 is
As shown in Figures 2 and 3, experiments have shown that in the axial direction, the temperature at the center increases due to large heat radiation from both end faces, and in the circumferential direction, the temperature at the top of the drum increases due to the convection effect. Confirmed by.

In order to correct the above non-uniform temperature distribution,
The calorific value density (watts per unit area) near the left and right ends in the axial direction of the drum is made larger than that in the center, and the calorific value density near the top in the circumferential direction of the drum is compared to the bottom. The arrangement of the heating element of the heater can be devised to make it smaller.

The present invention is characterized in that a heater heating element is provided based on the above idea.

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated in detail based on the drawing which shows the Example.

In the first embodiment of the present invention shown in FIGS. 4 and 5, 1 is a photosensitive drum, 2 is a drum shaft, and around the drum 1 is an image forming apparatus consisting of a charger, an exposer, and a developer (not shown). An image forming apparatus consisting of a container is disposed. The drum shaft 2 is supported by side plates 3 and 4 disposed within the main body of the copying machine, and one end of the drum shaft 2 is fitted and fixed to a boss 5 fixed to the side plate 3. The other end of the drum shaft 2 is supported by the side plate 4 via a bearing 6 and an auxiliary side plate 7. The bearing 6 is fixed to an auxiliary side plate 7, and the auxiliary side plate 7 is fixed to the side plate 4 with a hole 7a formed in the auxiliary side plate 7 and a fixing pin 8 provided on the side plate 4 fitted in the hole. There is.

Flanges 9, 10 are provided on both sides of the drum 1, by which the drum 1 is supported. The abutment surfaces of the drum and flange are both tapered so that they abut on the entire surface, and at least a portion of the abutment surfaces are provided with, for example, engagement protrusions and engagement grooves (not shown) for the drum and flange to rotate together. )
etc. are formed and they are engaged. The flanges 9 and 10 are connected to the boss 5 by bearings 11 and 12.
and is rotatable with respect to the drum shaft 2,
A tooth profile 13 is fixedly or integrally formed on the flange 9 as a drive transmission member.

The drum 1 rotates when the tooth profile 13 is driven by a drive device (not shown).

Furthermore, the flange 9 is held in a fixed position by being sandwiched between the boss 5 and a fixing member of a planar heater 16 (to be described later), whereas the flange 10 is movable in the axial direction with respect to the drum shaft. The drum 1 and flanges 9, 10 are connected by action.

Also, the right end of the drum shaft 2 is threaded,
A knob 15 is screwed onto this threaded portion 2a.
By tightening the knob 15, the spring 14
presses the flange 10 in the A direction, and the flange 1
0 drum 1 and flange 9 are connected.

A cylindrical sheet heater 16 is provided on the drum shaft 2.
are fitted and fixed. The planar heater 16 has a length that is almost the same as the width of the drum 1, but the heat generating portion 16a of the planar heater 16 is oriented in the axial direction of the drum 1, as shown by the dashed hatching in FIG. is missing the central part. In the example shown in the figure, there is no heat generating part in about 1/3 of the center. Further, in the circumferential direction of the drum 1, as shown in FIG.
For example, there is a gap of about 30 degrees to the left and right from directly above. Inner surface of drum 1 and sheet heater 1
It is attached close to the outer surface of 6 with a gap of about 2 to 3 mm, for example.

A conductive wire 17 to the planar heater 16 passes through the inside of the drum shaft and is led to the heater 16 from outside the side plate 3.

Since this device is constructed as described above, in the axial direction of the drum 1, the calorific value density at the left and right ends is greater than that at the center, and in the circumferential direction of the drum, the calorific value near the top. The density is smaller than other parts.

In another embodiment, the heater section is shown in FIG.
In the photosensitive drum unit having the same configuration as the embodiment shown in FIG. 4, a heater holding drum 20 made of aluminum, for example, is used instead of the cylindrical sheet heater.
Then, as shown in the cross section in FIG. 7, a coating 2 of silicon, etc.
A band-shaped heating element 2 formed by insulatingly covering a heating element 23 with 2.
1 wound spirally is placed a short distance from the inner surface of the photoreceptor drum 1. The other parts are exactly the same as in Figure 4. The band-shaped heating element 21 is wound with a tight pitch at both ends and a looser pitch at the center, thereby making the heat generation density at both ends greater than that at the center in the axial direction of the drum 1. Also in this case, as in the previous embodiment, the heater and the inner surface of the photosensitive drum 1 are close to each other, so the rise time is shortened.

As described above, according to the present invention, the heating element is provided in contact with or close to the inner surface of the photoreceptor drum, and the heat generation density is changed in the axial direction and circumferential direction of the photoreceptor drum, thereby increasing the temperature of the surface of the drum. The distribution can be made uniform and the rise time can be shortened, which is effective in improving image quality and work efficiency.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an experimental device in which a cylindrical heating element with a uniform calorific value density is provided inside a photoreceptor drum, and Figures 2 and 3 are axial and circular measurements taken by the experimental device, respectively. A curve diagram showing the drum surface temperature distribution in the circumferential direction, FIG. 4 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 5 is a sectional view taken along the line V-V in FIG. 4, and FIG. 6 is a diagram showing the present invention. FIG. 7 is a perspective view showing a heater portion of another embodiment, and FIG. 7 is a sectional view of a band-shaped heating element used therein. 1... Photosensitive drum, 2... Drum shaft, 16...
... Planar heating element, 21... Band-shaped heating element.

Claims (1)

[Claims] 1. In a heating device for a photoreceptor drum that is rotatably mounted on a machine frame and on which an image is formed by an image forming device, the heat-generating parts are arranged at both ends of the photoreceptor drum in the axial direction, and 1. A heating device characterized in that a cylindrical planar heating element, which is disposed in such a manner that a part of its upper side is missing in the direction, is fixed to the machine frame in close proximity to the inner surface of the photoreceptor drum.