Warming-up method for electrophotography image forming apparatus using two driving devices

A warming-up method for an electrophotography image forming apparatus. The warming-up method includes the steps of turning on a heat source when the image forming apparatus is turned on or when a wake-up event is generated in a power saving mode, driving an image fix-related driving body for rotating a heated roller and a pressing roller, thereby heating the rollers; driving a main driving body and rotating an OPC drum after driving the image fix-related driving body; and stopping the sub-driving body and the main driving body when surface temperature of the heated roller and surface temperature of the pressing roller reach an objective temperature, respectively, by means of heat from the heat source and rotation of the heated roller and the pressing roller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 2003-68219 filed Oct. 1, 2003, in the Korean Intellectual Property Office, the entire contents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of warming-up an electrophotography image forming apparatus. More particularly, the present invention relates to a method of warming-up an electrophotography image forming apparatus, capable of enhancing a performance efficiency of a pressing roller within a short time by driving an image fix-related driving body built in the electrophotography image forming apparatus immediately after a wake-up event is generated or when power is turned on, thereby securing a warming-up temperature of the pressing roller in advance.

2. Description of the Related Art

An electrophotography technique is often used in image forming apparatuses such as laser beam printers, copiers, or plain paper fax machines.

FIG. 1illustrates a conventional image forming apparatus10employing a related art electrophotography. As shown inFIG. 1, the image forming apparatus10includes a charged roller11for printing an image data on a print paper, an organic photo conductive (OPC) drum12, an exposing device13, a developing roller14, a transfer roller15, a pick up roller16, and a fixer18. In an exemplary print process, a high voltage is provided to the charged roller11. The charged roller11rotates and charges a photosensitive body applied to a peripheral surface of the OPC drum12. Then a light generated by the exposing device13forms on the surface of the charged OPC drum12and forms an electrostatic latent image for printing. Later, a toner supplied from the developing roller14is applied to the electrostatic latent image formed on the surface of the OPC drum12, and forms a visualized image. The high-voltage transfer roller15transfers the visualized image formed on a transported print paper17. The visualized image being transferred to the print paper17is affixed onto the print paper17under high heat and high pressure from a heated roller19and a pressing roller20that are built in the fixer18.

Usually, the image forming apparatus10operates in one of the following four modes: a printing mode, a ready mode, a power-saving mode, and a warming-up mode. To maintain and advance these modes, more than one driving body is required to be inside the image forming apparatus10. Another related driving body is also set to work when the image forming apparatus10is turned on or changes from the power-saving mode to the warming-up mode when the wake-up event is generated. In other words, the image forming apparatus10has two driving bodies. One is a main driving body that is related to rotation of the OPC drum12, and the other is an image fix-related driving body that is related to an image fixing process. According to a related art algorithm, when the heated roller19reaches a warming-up starting temperature after power-on or generation of the wake-up event, the main driving body connected to the OPC drum12and the image fix-related driving body connected to the fixer18are, respectively, set to drive for the warming-up, to raise temperature of the heated roller18up to a warming-up objective temperature. There are differences in these two driving bodies in terms of driving objectives. Through the main driving body's action, the OPC drum12is evenly charged by the high voltage provided by the charged roller11, and through the image fix-related driving body's action, the heated roller19and the pressing roller20are, respectively, rotated and warmed up to an appropriate temperature for fixing an image. Because the OPC drum12has a short lifespan and is very expensive, it is set to rotate only for a predetermined time in order to prevent any damages from frequent rotations. However, in case of the related art image forming apparatus, temperature transition of the pressing roller20is disregarded, and thus both driving bodies are designed to drive together at the same point. That is, the main driving body and the image fix-related driving body start driving together following power-on or generation of the wake-up event, or from a certain warming-up starting point. This is because the same algorithm applied to an image forming apparatus having one single driving body is applied to the image forming apparatus having the main driving body and the image fix-related driving body, and also because the main driving body is driven only for a predetermined time to reduce damage in the OPC drum12. However, it is not necessary that the main driving body and the image fix-related body always drive together. Moreover, a heat source built in the heated roller19starts driving from the warming-up starting point. As the heat source drives and the pressing roller20and the heated roller19rotate, temperature of the heated roller and the pressing roller20reaches an objective temperature, respectively. More specifically, the heated roller19is heated directly by the heat source therein while the pressing roller20is heated using an indirect method. In other words heat is transferred from the heated roller19as the pressing roller20is in contact with the heated roller19. The heated roller19is heated more than the pressing roller20because the heated roller19has its own source for raising temperature. Therefore, the pressing roller20, which is heated indirectly, takes a relatively longer time to get to its objective temperature. Accordingly, even after the heat source is turned off because the heated roller19reached the warming-up objective temperature, there needs to be a predetermined time for heat transfer from the heated roller19to the pressing roller20. In fact, this is a major factor that determines standby time for the warming-up period. As discussed above, the conventional warming-up method requires a long period of time to transfer heat from the heated roller19to the pressing roller20, thereby consuming more time for the warming-up, which indicates that a user has to wait longer before using the image forming apparatus. Therefore, an improved warming-up method is required to solve the above-mentioned problem.

SUMMARY OF THE INVENTION

The present invention has been developed in order to solve the above drawbacks and other problems associated with the conventional arrangement. An aspect of the present invention is to provide a warming-up method for an electrophotography image forming apparatus using two driving devices, in which a main driving body and an image fix-related driving body each operate under an independent algorithm. Thus, by driving the image fix-related driving body immediately after generation of a wake-up event or following power-on, a pressing roller and a heated roller can be rotated from the beginning, and thus, a temperature of the pressed roller can reach an objective temperature as soon as possible.

To achieve the above object, there is provided a warming-up method for an electrophotography image forming apparatus including an image fix-related driving body for rotating a heated roller with a built-in heat source and a pressing roller in contact with the heated roller, and a main driving body for rotating an organic photo conductive (OPC) drum. The method comprises turning on the heat source when the image forming apparatus is turned on or when a wake-up event is generated in a power saving mode, driving the image fix-related driving body (a sub-driving body) to rotate the heated roller and the pressing roller, thereby heating the rollers; driving the main driving body and rotating the OPC drum after driving the image fix-related driving body; and stopping the sub-driving body and the main driving body when a surface temperature of the heated roller and the surface temperature of the pressing roller reach an objective temperature, respectively, by means of heat from the heat source and rotation of the heated roller and the pressing roller.

In an exemplary embodiment, it is determined whether the surface temperature of the heated roller reaches a warming-up starting temperature, by means of the heat from the heat source and the rotation of the heated roller and the pressing roller, and when the surface temperature of the heated roller reaches the warming-up starting temperature, the main driving body is driven and the OPC drum is rotated.

The present invention can reduce a warming-up time period and thus the waiting time of a user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain embodiments of the present invention will be described in greater detail with reference to the accompanying drawings.

In the following description of the present invention, exemplary diagrams and elements are provided. However, the present invention is not limited to the exemplary diagrams and elements. Thus, it should be apparent that the present invention can be performed without the specific examples used. Also, well-known functions or constructions are not described in detail since they would unnecessarily obscure the invention.

FIG. 2is a schematic diagram illustrating an image forming apparatus using a warming-up method in accordance with an embodiment of the present invention. The image forming apparatus100according to an embodiment of the present invention includes a heated roller110, a pressing roller120, a sub-driving body130, a power supply140, a controller150, and a temperature detecting means160. The sub-driving body130is an image fix-related driving body. It is referred to as the ‘sub-driving body’ to distinguish it from a main driving body related to an organic photo conductive (OPC) drum (not shown).

The heated roller110is a part of a fixer, and heated by a heat source110ainstalled therein. When the image forming apparatus100is turned on or turns from a power-saving mode to a warming-up mode at the generation of a wake-up event, the heat source110ais turned on by an applied voltage fed from the power supply140. Also, the temperature detecting means160is mounted at a predetermined position of the heated roller110to detect the surface temperature of the heated roller110, and transfers the detected temperature to the controller150. Preferably, a thermistor is used as the temperature detecting means160. The controller150, based on the transmitted surface temperature being detected, determines whether a present surface temperature is appropriate for image fixing, and determines to turn on or off the heat source110aon the basis of the determination.

The pressing roller120together with the heated roller110comprise the fixer. A pressing spring120ais attached to a shaft (not shown) of the pressing roller120, to press the pressing roller120against the heated roller110tightly. Therefore, when a print paper to which a visualized image is transferred passes between the heated roller110and the pressing roller120, the transferred visualized image is fixed onto the print paper by heat and pressure from the rollers.

The heated roller110uses the sub-driving body130as a driving source. To accomplish this, a connected gear connected to the sub-driving body130is pivotably fixed at one end of the heated roller110, and the pressing roller120is rotated by a contact force generated between the rollers.

The controller150controls the image forming apparatus, including a warming-up time period, a warming-up temperature and so forth. That is, when the image forming apparatus100is turned on or wakes up from the power-saving mode, the controller150controls the power supply140so that the heat source110can be turned on. According to an embodiment of the present invention, the controller150controls the power supply140to ensure that the sub-driving body130starts driving immediately after the heat source110ais turned on. The controller150, based on the surface temperature provided by the temperature detecting means160, determines whether to turn on the heat source110a, whether to drive the sub-driving body130, and whether to drive the main driving body (not shown). On the basis of the determination, the controller150controls the power supply140.

FIG. 3is a flow chart describing the warming-up method in accordance with an embodiment of the present invention. For convenience, a warming-up starting point is limited to the case where power of the image forming apparatus100is on.

When the image forming apparatus100is turned on at step S200, the controller150, in response thereof, controls the power supply140to turn on the heat source110aat step S210. Also, the controller150controls the power supply140to start driving the sub-driving body130at step220. As the sub-driving body130starts driving, the heated roller110rotates, and the pressing roller in contact with the heated roller110rotates also. In this manner, heat transfer from the heated roller110to the pressing roller120is actively done at step S220. The temperature detecting means160selectively detects the surface temperature of the heated roller, and reports the detected surface temperatures to the controller150. Then the controller150determines whether the transferred surface temperature has reached the warming-up starting temperature at step230. If not, the controller150continues the detection process to determine whether the transferred surface temperature has reached to the warming-up starting temperature. If the surface temperature has reached the warming-up starting temperature, the controller150recognizes that a present state of the image forming apparatus is ready for the warming-up mode at step S240. According to an embodiment of the present invention, at this point, the temperature of the heated roller110as well as the temperature of the pressing roller120is already at a predetermined high surface temperature, respectively. Accordingly, at the warming-up starting point, the surface temperature of the pressing roller120according to an embodiment of the present invention is relatively higher than that of the conventional devices, whereby the objective temperature of the pressing roller can be achieved more quickly.

The controller150drives the main driving body (not shown) related to the OPC drum (not shown) at step S250, and electrifies the OPC drum. On the other hand, since the heat source110ahas already been driven, the surface temperature of the heated roller continuously increases. Similarly, the surface temperature of the pressing roller120, compared to the surface temperature at the warming-up starting point, continuously increased. Based on the detected surface temperature provided by the temperature detecting means160, the controller150determines whether the surface temperature of the heated roller110has reached the warming-up objective temperature at step260. If the warming-up objective temperature has been reached, the controller150controls the power supply140to cut off power supply to the heat source110at step S270. However, the sub-driving body130does not stop driving even after power to the heat source110ais cut off, and the pressing roller120in contact with the heated roller110continues to rotate. Through rotation of the pressing roller120in contact with the heated roller110, the heat of the heated roller110is transferred to the pressing roller120, resulting in an increase of the temperature of the pressing roller120. Based on the transferred surface temperature from the temperature detecting means160, the controller150determines whether the surface temperature of the pressing roller120has reached its objective temperature at step S280. There are diverse methods for detecting the surface temperature of the pressing roller120. In an exemplary embodiment of the present invention, a certain time interval can be predetermined according to the initial setting conditions of the image forming apparatus such that the surface temperature of the pressing roller120is assumed to have reached the objective temperature of the pressing roller120after the predetermined time interval from the turn-off of the heat source110a. The predetermined time interval may be set differently in consideration of different printing environments. However, the present invention is not limited thereby. Once it is determined that the surface temperature of the pressing roller is raised as high as the objective temperature, the controller150ends the whole process for warming up the present image forming apparatus at step S290.

FIG. 4is a timing diagram comparing a transition of the surface temperature of the heated roller and the pressing roller based on the warming-up method in accordance with an embodiment of the present invention to a transition of the surface temperature of the heated roller and the pressing roller based on a conventional warming-up method.FIGS. 2 through 4will also be referred to. InFIG. 4, the solid line indicates a temperature transition line of the heated roller110, and a dotted line indicates a temperature transition line of the pressing roller120, and a centerline (i.e. dash-dot-dash line) indicates a temperature transition line of the pressing roller120in accordance with a conventional method. Further, an x-axis represents time, and a y-axis represents temperature. For convenience, the warming-up objective temperature and the warming-up starting temperature occurs where the temperature crosses the temperature transition line, and the objective temperature of the pressing roller occurs where the temperature crosses the temperature transition line.

In the image forming apparatus100, the heat source110ais turned on at t1point where the image forming apparatus100is on or the wake-up event is generated in the power-saving mode. In accordance with an embodiment of the present invention, the sub-driving body130at t1point starts driving via the applied voltage. On the other hand, the sub-driving body130in the prior art does not drive at this point.

Referring again toFIG. 4, between the t1and t2interval, the surface temperature of the heated roller110is raised by means of the heat source110abeing turned on. In an embodiment of the present invention, since the pressing roller120and the heated roller110rotate, they have a broad contact area. Therefore, heat can be more easily transferred, and the surface temperature of the pressing roller120is increased. However, because the pressing roller120is heated indirectly, the increasing slope of the temperature transition of the pressing roller120is relatively smaller than the increasing slope of the surface temperature of the heated roller110. The sub-driving body130of the related art does not drive during this interval, and thus the contact area between the two rollers is small. As a result thereof, although heat transfer is made between the two rollers, the temperature increase of the pressing roller120is rather insignificant.

At the t2point, when the heated roller110reaches the warming-up starting temperature, the image forming apparatus100goes into the warming-up mode. For the prior art, this is the point where the sub-driving body130starts driving. Thus, from this point, the increasing slope of the surface temperature of the pressing roller120of the present invention and the increasing slope of the surface temperature of the pressing roller120of the prior art run substantially parallel with each other.

In the t2–t3interval, not only the surface temperature of the heated roller but also the surface temperature of the pressing roller120continuously increase because of the continual driving of the heat source110aand the rotation of the pressing roller120in contact with the heated roller110.

At the t3point, the surface temperature of the heated roller110has reached the warming-up objective temperature, and the heat source110ais turned off.

In the t3–t4interval, the surface temperature of the heated roller110still continues increasing above the warming-up objective temperature because of the remaining heat in the heat source110a, and at a certain point, it gradually decreases. Similarly, the surface temperature of the pressing roller120is increased by the heat provided from the heated roller110, and at a certain point, it gradually decreases.

T4is a point where the warming-up mode of the image forming apparatus100according to an embodiment of the present invention ends. The t4point is where the surface temperature of the pressing roller120has reached the objective temperature thereof. Through this, the heated roller110and the pressing roller120can retain proper temperatures for image fixing.

On the other hand, at the t4point, the surface temperature of the pressing roller120according to the prior art has not yet reached the objective temperature of the pressing roller120, so the warming-up mode has not ended, and thus, the sub-driving body130and the main driving body (not shown) keep driving even in the t4–t5interval. Finally, the objective temperature of the prior art pressing roller is reached at the t5point, and the warming-up mode is ended. That is, the related art requires more time (e.g., t4–t5) for warming up than the present invention.

In conclusion, the image forming apparatus according to an embodiment of the present invention can be advantageously used for reducing the warming-up time period of the image forming apparatus. This in turn reduces waiting time of users and is convenient for users.

Since the warming-up time is reduced, power consumption can be reduced, and thus, the economic burden on the user is reduced. As a result, reliability of the product is improved.

Another problem with the prior art was that the warming-up process ended long after the heat source was turned off. Thus, by the time image fixing occurred, the surface temperature of the heated roller was often lower than desired. However, in an embodiment of the present invention, since the warming-up process ends soon after the heat source is turned off, the surface temperature of the heated roller at the end of the warming-up mode is the desired surface temperature for the heated roller.