JPH0325453A - Heat insulating device for photosensitive drum - Google Patents

Abstract

PURPOSE:To accurately hold the photosensitive material drum at desired temperature by detecting temperature with two temperature sensors which are brought into contact with a no-image area, and controlling energizing to a heat insulating heater and also making the distribution density of the heat generating body larger at both its end parts than at the center part. CONSTITUTION:The heat insulating heater 10 is arranged in a drum main body 2 so as to be in contact with its inner peripheral surface and the distribution density of its heat generating wire is low at the axial center part of the drum main body 2 and high at both end parts. Then the two temperature sensors 13 and 14 invariably brought into contact with no-image areas 11 and 12 at both ends of the drum main body 2 are provided and a control part 15 controls a power circuit 16 according to the outputs of the temperature sensors 13 and 14 to turn on/off the heat insulating heater 10. Consequently, the whole photosensitive drum 1 is accurately held at the desired temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat-retaining device for a photosensitive drum used in copying machines, printers, and the like.

Traditional technology> Quiet? Due to their nature, photosensitive drums used in IS copying machines, electrostatic printers, and the like must be kept at a constant temperature during use.

For this reason, various proposals have been made regarding temperature sensors for detecting the temperature of the photoreceptor drum, temperature control, and heat-retaining heaters.

For example, JP-A-60-129772 discloses a configuration in which a temperature sensor is held in a non-contact state with respect to the surface of a photoreceptor drum, and a heater is controlled based on the output of the temperature sensor.

In addition, JP-A-56-54474 discloses that while the photoreceptor drum is stopped, a temperature sensor is brought into contact with the surface of the photoreceptor drum, and the temperature of the photoreceptor drum is controlled based on the output of the temperature sensor. discloses a structure in which the temperature sensor is separated from the drum surface while the photosensitive drum is being driven.

Furthermore, ■Japanese Patent Application Laid-Open No. 58-62665 and Japanese Patent Application Laid-open No. 6
1 - 2 6 2 7 5. No. 1 discloses a configuration in which a temperature sensor is brought into contact with a non-image area of a photoreceptor drum.

<Problems to be Solved by the Invention> The above-described conventional proposals regarding temperature sensors and heat retention control each have the following drawbacks.

First, in the technique (2), since the temperature sensor is not in contact with the photoreceptor drum, the temperature sensor is easily affected by the temperature atmosphere around the photoreceptor drum, making it difficult to accurately measure the temperature of the photoreceptor drum. However, there is a drawback that the ability to follow temperature changes of the photoreceptor drum is also poor.

Further, in the structure (2), the drum temperature is kept constant while the photoreceptor drum is stopped, but since the temperature is not detected while the photoreceptor drum is being driven, there is a drawback that the drum temperature fluctuates while the photoreceptor drum is being driven.

Furthermore, in the case of configuration (2), the non-image area of the photoreceptor drum is usually located at both ends of the photoreceptor drum in the axial direction, and since both ends are parts where heat is easily dissipated, the temperature at which the temperature of that part is detected is Even if the temperature is simply controlled based on the output of the sensor, there is a drawback that it is difficult to maintain the photosensitive drum at a desired temperature.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-retaining device that can accurately maintain a photoreceptor drum at a desired temperature by eliminating the various drawbacks of the prior art as described above.

Means for Solving the Problems> The present invention is arranged in a photoreceptor drum, and the distribution density of the heating element is higher in the portions located at both ends than in the portion located in the center in the axial direction of the drum. A raised heater and
at least two temperature sensors for measuring the temperature of the photoreceptor drum, each of which is in contact with a non-image area of the outer peripheral surface of the photoreceptor drum that is not used for the image bottom at both ends in the axial direction, and for measuring the temperature of the photoreceptor drum; 1. A photoreceptor drum heat-retaining device comprising: a control means for controlling energization of the heat-retaining heater based on outputs of two temperature sensors.

Further, the present invention includes a plurality of heat-retaining heaters arranged in the axial direction of the photoreceptor drum, and a non-heater that is not used for forming an image at both ends in the axial direction of the outer peripheral surface of the photoreceptor drum. at least two temperature sensors each in contact with an image area for measuring the temperature of the photoreceptor drum; and energization control means for selectively energizing the plurality of heat-retaining heaters based on outputs of the at least two temperature sensors. 1 is a photoreceptor drum heat retention device characterized by comprising:

Effect> The temperature of the photoreceptor drum can always be detected accurately and without time lag by the at least two temperature sensors that are in contact with the non-image area of the photoreceptor drum.

The control means controls the electricity supply to the heat retention heater,
Since control is performed based on accurate photoreceptor drum temperatures without time lag detected by at least two temperature sensors, temperature control quickly follows temperature changes of the photoreceptor drum.

According to an aspect of the present invention, in the heat-retaining heater, the distribution density of the heating element is higher at both end portions than in the central portion, so that the heat-retaining heater can effectively reduce the axial end portions of the photoreceptor drum from which heat easily escapes. The temperature distribution of the photoreceptor drum in the axial direction can be made even.

According to another aspect of the invention, there are a plurality of heat-retaining heaters and they are arranged in the axial direction within the photoreceptor drum.
By selectively energizing the plurality of heat-retaining heaters, it is possible to heat the portion where the temperature has decreased in the axial direction, and the temperature distribution in the axial direction can be made uniform.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of the present invention.

The photosensitive drum 1 includes a drum body 2 having a photosensitive layer formed on the surface of a cylindrical, for example, aluminum tube, and flanges 3 and 4 fitted into both ends of the drum body 2. Each flange 3.4 has a ball bearing 5, respectively.
．． It is designed to be rotatably held in the 6th grade. Furthermore, a gear 7 and a gear shaft 8 are attached to one flange 3 so that driving force can be transmitted thereto.

A heat-retaining heater 10 is arranged inside the drum body 2 so as to be in close contact with the inner peripheral surface thereof. As will be described in detail later, the heat-retaining heater 10 includes a flexible sheet-like substrate and a heat-generating wire arranged on the substrate. As shown in the figure, the distribution density of the heating wire is low in the axially central portion of the drum body 2 and high in the portions located at both ends.

The drum body 2 has an electrostatic latent image formed on its outer peripheral surface, but there are non-image areas 11 and 12 at both ends in the axial direction that are not used for image formation. In this embodiment, two temperature sensors 13.14 are provided in the non-image areas 11.12 at both ends, respectively, and are in constant contact with each other. Detection is possible without any time lag.

The detection outputs of the two temperature sensors 13 and 14 are given to the control section 15. The control unit 15 includes two temperature sensors 13 and 14.
The power supply circuit 16 is controlled based on the output of the power supply circuit 16 to turn on/off the heat-retaining heater.

By the way, as explained in the prior art, the drum body 2
has a characteristic that heat is more easily dissipated from both ends than from the center in the axial direction. This is because flanges 3.4 made of a heat conductor are fitted into both ends of the drum body 2, so the heat at both ends of the drum body 2 is transferred from these flanges 3, 4 to the ball bearings 5.6, etc. It is easy to escape.

In particular, heat conduction increases on the side of the device main body that is connected to the drive mechanism (not shown).

Therefore, it is difficult to say that the temperature detected by the temperature sensor 13.14 in contact with the non-image area 11.12 of the drum body 2 accurately detects the surface temperature of the axially central portion of the drum body 2. The surface temperature of the axially central portion of the drum body 2 is measured by a temperature sensor 13. ] It is slightly higher than the temperature detected in 4.

Therefore, in order to cope with such a temperature difference distribution in the direction of the drum axis, in this embodiment, the distribution density of the heat generating heaters of the heat retention heater 10 is changed in the direction of the drum axis.

FIG. 2 is a diagram showing a specific example of the heat retention heater 10, and is a partially cutaway developed view of the heat retention heater 10 in an expanded state. The heat-retaining heater 10 has a structure in which, for example, a heating wire 21 is arranged in a meandering manner on one side of a thin stainless steel substrate 20, and the heating wire 21 is covered with a cotton cloth 22. When the heat retention heater 10 is housed in the drum body 2, the upper side 23 is aligned with the lower side 24.
It is rolled up so that it faces and touches the , and the cotton cloth 22 side is on the inside.

The heating wire 21 is a coated wire made of tungsten or the like, in which one or many long wires are tied together. The distribution density of the heating wire 21 is low in the center and high in the left and right sides in the drum axis direction.

Specifically, the region of the substrate 20 is divided into three in the direction of the drum sleeve, and the heating wires are connected to the upper side 23 and the lower side 2 for each region.
Line segments arranged parallel to 4 are arranged in a meandering manner so that they are lined up at equal intervals. In the central part, the intervals between the line segments are made relatively wide, so that the distribution density of the heating wires 21 is made low;
On both sides, the intervals between the line segments are relatively narrow, and the distribution density of the wires 21 is increased.

As a result of the heat generating wire 21 being arranged in this manner, when the heat generating wire 21 is energized, the amount of heat generated on both sides of the drum pongee direction is greater than that at the center. Therefore, both ends of the drum body 2, which easily radiate heat, are effectively heated and kept warm.

Therefore, according to this embodiment, two temperature sensors 13
, 14, the heat retention heater 10 heats both ends of the drum body 2 more than the center, and the surface temperature of the drum body 2 changes to the drum axis. Any position can be kept constant regardless of direction.

FIG. 3 is a partially cutaway developed view showing another specific example of the heat-retaining heater 10. If the distribution density of the heat generating wire 21 is to be low at the center in the axial direction of the drum and high at both left and right sides, the meandering arrangement of the heat generating wire 21 may be changed to the left side 25 in the direction orthogonal to the drum axis.
The line segments parallel to the right side 26 may be arranged in parallel, and the interval between the parallel line segments may be relatively wide at the center and relatively narrow toward both left and right ends. This arrangement has the advantage that the distribution density of the heating wires 21 can be gradually increased toward both ends in the drum axis direction.

The rest of the configuration is the same as that in FIG. 2, and the explanation here will be omitted.

In each of the heat-retaining heaters 10 shown in FIGS. 2 and 3, the shape of the substrate 20 is a parallelogram. In other words, it has a parallelogram shape that roughly corresponds to the shape obtained by cutting a cylinder with a diameter corresponding to the inner diameter of the drum body 2 along a cutting line along the helical direction with a constant lead angle θ. This shape has the advantage that the heat-retaining heater 10 can be easily inserted into the drum body 2, or that the heat-retaining heater 10 can be brought into close contact with the inner surface of the drum body 2 in the inserted state.

Other features of the substrate shape of the heat-retaining heater 10 are disclosed in detail in an earlier application of the present applicant (see Japanese Patent Laid-Open No. 60-254587).

In the heat-retaining heater 10 used in the present invention, the substrate shape does not necessarily have to be a parallelogram as described above, but may be rectangular.

Further, in each specific example of the heat-retaining heater 10 described above, one long heating wire 21 is used as the heating element, and the heating wire 21 is arranged in a meandering manner, and the distribution density is changed by adjusting the arrangement interval. However, the distribution density of the heating elements may be changed by other configurations.

For example, instead of a heating wire, a heating coil or a planar heating element may be used as the heating element.

Further, even when heat generating wires are used, instead of arranging one heat generating wire in a single stroke, a plurality of heat generating wires may be appropriately connected and arranged in a ladder shape or other shape. In short, it is sufficient that the distribution density of the heating elements in the heat-retaining heater 10 is low at the center in the drum axis direction and high at both left and right sides.

FIG. 4 is a diagram showing a schematic configuration of another embodiment of the present invention. A feature of this embodiment is that the heat-retaining heaters arranged inside the drum body 2 are composed of three heat-retaining heaters Ha, Hb, and Hc arranged in the axial direction of the drum body 2. The three heat-retaining heaters Ha, Hb, and He are selectively energized based on the outputs of the two temperature sensors 13 and 14.

An example of this energization control is as follows.

Now, let To be the temperature of the drum body 2 that you want to maintain, that is, the set temperature, Ta1 be the temperature detected by the temperature sensor] 3, and Tb be the temperature detected by the temperature sensor 14, then each temperature sensor 13
, 14 and the set temperature TO, the heat retaining heaters Ha, Hb, Hc are switched on/off as follows.

■ Ta<To and Tb TO Ha, Hb, Hc are all turned on ■ Ta<To is T b − To Ha is turned on, H
b, Hc off ■ TamTo and Tb TO Turn on Hc, turn off Ha, Wb ■ TamTbmTo Turn off all Ha, Hb, He Such switching control is performed in the control section 15, but the control section 15 is In the case of a configuration including a computer, the on/off control of the three heat retention heaters Ha, Hb, and Hc is specifically performed according to the flowchart shown in FIG. 5 or the flowchart shown in FIG.

The flowchart in FIG. 5 will be briefly explained. Control unit 15
compares the detected temperature Ta of the temperature sensor 13 and the set temperature TO (step S1), and if Ta < TO, turns on the heat retention heater Ha (step S2), otherwise turns off the heat retention heater Ha. (Step S3).

Next, the control unit 15 compares the detected temperature Tb of the temperature sensor 14 with the set temperature TO (step S4), and if Tb<To, turns on the heat retention heater He (step S5); otherwise, Turn off the melon heater Hc (step S6
).

Further, the control unit 15 determines whether or not the detected temperatures Ta and Tb of the two temperature sensors 13 and 14 are both lower than the set temperature To (step S7), and if both are lower than the set temperature, the temperature retaining heater Hb is turned on. If not, turn off the heat retaining heater Hb (step S8).
9).

By repeating steps 81 to S9 above, the control section 15 selectively turns on/off the heat-retaining heaters Ha, Hb, and Hc to maintain the temperature of the photoreceptor drum 1 at a constant temperature Ho.

The flowchart in FIG. 6 also controls on/off of the heat retention heaters Ha, Hb, and Hc by comparing the detected temperatures Ta and Tb of the temperature sensors 13 and 14 with the set temperature To. Since it is more obvious, the explanation here will be omitted.

In this embodiment, as in (1) and (2) above, when the detected temperature Ta of the temperature sensor 13 is Ta > TO or when the detected temperature Tb of the temperature sensor 14 is Tb<To, only the heat retaining heater Ha is activated. In the above embodiments, only the heat retaining heater He is turned on, or only the heat retaining heater He is turned on, but instead of this, more detailed control may be performed as follows.

The average value of the temperatures Ta and Tb detected by the temperature sensors 13 and 14 is calculated, and the average value and the temperature (To-(Z) (however, α is a predetermined minute temperature) are compared to calculate the temperature of the central heat-retaining heater. It turns Hb on/off.

Specifically, (T a + T b ) / 2 <
When T o - a, turn on Hb, otherwise,
This turns off Hb.

In any case, in this way, multiple heat retention heaters Ha, Hb
, Hc are arranged in the direction of the drum axis, and the heat-retaining heaters Ha
, Hb, and Hc, both ends of the drum body 2 can be heated more than the central part in the axial direction, and both ends, which tend to radiate heat, can be appropriately kept warm. Therefore, the drum body 2 has an even temperature distribution in its axial direction.

Effects of the Invention Since the present invention is configured as described above, the surface temperature of the photoreceptor drum can be measured accurately and without time lag based on two temperature sensors.

In addition, the heat-retaining heater has a variable distribution density of heating elements, a plurality of heat-retaining heaters, and selective energization control, so it can be used to effectively target parts of the photoreceptor drum that are likely to radiate heat. It can be kept warm. Therefore, the entire photoreceptor drum can be accurately maintained at a desired temperature.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of a heat retention device according to an embodiment of the present invention. FIG. 2 is a partially cutaway developed view showing a specific example of the heat-retaining heater. FIG. 3 is a partially cutaway developed view showing another specific example of the heat-retaining heater. FIG. 4 is a diagram showing a schematic configuration of a heat retention device according to another embodiment of the present invention. 5 and 6 are flowcharts showing the control operation of the control section of FIG. 4, respectively. In the figure, 1... Photosensitive drum, 2... Drum body, 3.4... Flange, 10... Heat retention heater, 1
5... Control unit, 16... Power supply circuit, 20... Board, 21... Heat generating wire. (2 others)

Claims (1)

[Claims] 1. Arranged within the photoreceptor drum, the drum compared to the part located in the axial center of The part located at both ends is the heating element. A heat-retaining heater with high cloth density, Both axial ends of the outer peripheral surface of the photoreceptor drum Non-images that are not used for image formation each in contact with the image area and the photoreceptor driver at least two for measuring the temperature of the one temperature sensor, output of the at least two temperature sensors; The energization of the heat retention heater is controlled based on the power. control means for controlling the A photosensitive drum characterized by comprising: Heat retention device. 2. Inside the photoreceptor drum, in the axial direction of the drum multiple heat insulating heaters arranged in Both axial ends of the outer peripheral surface of the photoreceptor drum Non-images that are not used for image formation each in contact with the image area and the photoreceptor driver at least two for measuring the temperature of the one temperature sensor, output of the at least two temperature sensors; the plurality of heat retention heaters based on the power; energization control means for selectively energizing; A photosensitive drum characterized by comprising: Heat retention device.