JP2012090007A - Image reading device and image reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately cool a motor in an ADF scanner, when driving respective two different mechanisms of an ADF unit and a carriage having a mounted image reading unit, with the one motor.SOLUTION: In an image reading device for forming image data from data read from a manuscript, a controller is provided to control a first mode for reading an image from the manuscript in a stop state, by driving a carriage unit by a drive unit, and a second mode for reading the image while carrying the manuscript to the position of the image reading unit in the stop state, by driving a manuscript carrying unit by the drive unit. In the first mode, the controller calculates a heat amount of the drive unit using a first heat generation parameter, while in the second mode, the controller calculates the heat amount of the drive unit using a second heat generation parameter different from the first heat generation parameter.

Description

  The present invention relates to an image reading apparatus and an image reading method.

  An image reading apparatus (scanner) that reads an original and forms image data is known. One such image reading apparatus is an ADF scanner that reads an image while moving a document. In general, an ADF scanner includes an ADF (auto document feeder) unit that conveys a document and an image reading unit that reads an image from the conveyed document. As a method for reading a document, a method for reading an image while driving the ADF unit to convey the document, and a method for reading an image from a document set on a document table by moving a carriage on which the image reading unit is mounted. There is. When performing these two types of reading methods using an ADF scanner, driving the ADF unit and the carriage (image reading unit) with a single motor reduces the number of parts and costs, and reduces the size of the product. Can be realized.

  As a technique for driving two different mechanisms with one motor, a printer that realizes driving of a carriage on which a print head is mounted and driving of a sheet feeding mechanism for conveying print target paper with one motor has been proposed. (For example, Patent Document 1).

JP 58-33487 A

  In an ADF scanner, when two different mechanisms of an ADF unit and a carriage (image reading unit) are driven by a single motor, the load on the motor, environmental conditions, and the like differ between when the ADF unit is driven and when the carriage is driven. Therefore, the heat generation status of the motor is also different. Therefore, when the motor is cooled, it is necessary to change the cooling method in accordance with the driven mechanism of the two mechanisms. That is, it is necessary to perform appropriate cooling in accordance with each situation when the ADF unit is driven and when the carriage is driven.

  However, Patent Document 1 and the like do not consider the change in the heat generation state of the motor due to the difference in the driven mechanism, and do not consider changing the cooling method. For this reason, it has been difficult to cool the motor so that the two conditions are appropriate for both cases.

  In the present invention, in the ADF scanner, when two different mechanisms of the ADF unit and the carriage on which the image reading unit is mounted are driven by one motor, it is an object to perform appropriate motor cooling at the time of driving each mechanism. It is said.

  A main invention for achieving the above object includes: a document conveying unit that conveys a document; an image reading unit that reads an image from the document; a carriage unit that supports and moves the image reading unit; the document conveying unit; A driving unit that drives a carriage unit; a first mode in which the carriage unit is driven by the driving unit to read an image from the document in a stopped state; and the document conveying unit is driven by the driving unit; An image for forming image data from data obtained by reading the document, the control unit performing control of a second mode for reading the image while conveying the document to the position of the image reading unit in a stopped state; In the first mode, the control unit calculates a heat generation amount of the drive unit using a first heat generation parameter in the first mode, and in the second mode, To calculate the heating value of the drive unit with different second heating parameters from the first heating parameters, it is an image reading apparatus according to claim.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1A and 1B are external perspective views of the image forming apparatus 1. FIG. 3 is a diagram for explaining an image reading method by an image reading unit 30. FIG. 2 is a schematic diagram illustrating a configuration of a carriage unit 40. FIG. FIG. 6 is a diagram illustrating a state in which a document is conveyed by an ADF unit 50 in an ADF drive mode. 3 is a schematic diagram illustrating a configuration of a controller 60. FIG. FIG. 6A is a diagram for explaining the operation in the carriage drive mode. FIG. 6B is a diagram for explaining the operation in the ADF drive mode. It is a figure showing the flow for restricting the emitted-heat amount of the motor 41 in 1st Embodiment. It is explanatory drawing of the heat_generation | fever temperature T_sum of the motor 41. FIG. It is a figure showing the flow for restricting the emitted-heat amount of the motor 41 in a comparative example.

At least the following matters will become clear from the description of the present specification and the accompanying drawings.
A document conveying unit that conveys a document, an image reading unit that reads an image from the document, a carriage unit that moves while supporting the image reading unit, a driving unit that drives the document conveying unit and the carriage unit, and the carriage A first mode in which an image is read from the document in a stopped state by driving the drive unit, and the document conveying unit is driven by the drive unit at a position of the image reading unit in a stopped state. A second mode in which an image is read while conveying a document, and a control unit that controls the image, and an image reading device that forms image data from data obtained by reading the document, wherein the control unit includes: In the first mode, the heat generation amount of the drive unit is calculated using a first heat generation parameter, and in the second mode, a first heat generation parameter different from the first heat generation parameter is calculated. To calculate the calorific value of the driving unit with the heating parameters, the image reading apparatus characterized by.

  According to such an image reading apparatus, when two different mechanisms of the ADF unit and the carriage on which the image reading unit is mounted are driven by one motor in the ADF scanner, an appropriate motor is driven when each mechanism is driven. Cooling can be performed.

In such an image reading apparatus, it is preferable that the driving unit is mounted on the carriage unit.
According to such an image reading apparatus, two types of mechanisms can be driven by moving the carriage, and the cost can be reduced by downsizing the image reading apparatus and reducing the number of parts.

In the image reading apparatus, in the first mode, the heat generation of the drive unit is limited based on the heat generation amount of the drive unit calculated using the first heat generation parameter, and in the second mode, Preferably, the heat generation of the drive unit is limited based on the heat generation amount of the drive unit calculated using the second heat generation parameter.
According to such an image reading apparatus, it is possible to limit the heat generation of the motor based on the heat generation amount calculated corresponding to each mode. Therefore, the heat generation amount can be appropriately suppressed in any mode. .

In such an image reading apparatus, it is desirable to limit heat generation of the driving unit by providing a pause time during which the driving of the document conveying unit or the carriage unit is stopped during the image reading operation.
According to such an image reading apparatus, it is possible to provide a cooling time by stopping the driving of the motor in the middle, and to promote cooling by heat dissipation of the motor.

In such an image reading apparatus, when the heat generation of the driving unit is limited in the first mode, the carriage unit moves to the original position at the start of the image reading operation and then responds to the pause time. It is desirable to stop driving the carriage unit.
According to such an image reading apparatus, since the carriage does not stop suddenly during movement, it can be prevented that the user mistakes it as a failure of the carriage drive unit.

In such an image reading apparatus, when the heat generation of the driving unit is limited in the second mode, the pause time is divided into a plurality of times, and the document conveying unit performs a predetermined operation during the operation of conveying the document. It is desirable that the driving of the ADF unit is stopped at each timing according to the divided pause time.
According to such an image reading apparatus, since the document does not suddenly stop for a long time during conveyance, it is possible to prevent the user from misidentifying that the ADF unit is out of order.

In this image reading apparatus, it is preferable that the initial heat generation amount of the driving unit at the start of the image reading operation is calculated based on the temperature of the driving unit at the previous image reading operation.
According to such an image reading apparatus, since the temperature at the previous operation can be reflected in the temperature calculation in the current operation, a more accurate heat generation amount can be predicted.

  In addition, the document conveying unit conveys the document, the image reading unit reads the image from the document, the carriage unit supports and moves the image reading unit, and the driving unit moves the document conveying unit and A first mode in which the carriage unit is driven, and the carriage unit is driven by the driving unit by the control unit to read an image from the document in a stopped state; and the document conveying unit is driven by the driving unit. And a second mode in which an image is read while conveying the original to a position of the image reading unit in a stopped state, and the control unit includes: In the first mode, the heat generation amount of the drive unit is calculated using a first heat generation parameter, and in the second mode, the first heat generation parameter is calculated. Calculating the calorific value of the driving unit by using a different second heating parameters a meter, an image reading method, wherein it is apparent.

=== Basic Configuration of Image Reading Apparatus ===
The image reading apparatus 1 and its driving method used in this embodiment will be described. The image reading apparatus 1 has a scanner (image reading) function for reading an image from a document and generating image data. In this embodiment, as a method of reading an image, a document is automatically printed using a “carriage driving mode” in which an image is read while moving a carriage on which an image reading unit is mounted and an auto document feeder (hereinafter also referred to as ADF). There is an “ADF driving mode” in which an image is read while being conveyed. Details of both modes will be described later.

  1A and 1B are external perspective views of the image forming apparatus 1. FIG. The image reading apparatus 1 includes a main body unit 10, an image reading unit 30, a carriage unit 40, an ADF unit 50, and a control unit 60.

  The main body 10 includes a housing 11, a document table 12, and a document table cover 13. The housing 11 stores therein an image reading unit 30, a carriage unit 40, and a control unit 60. In addition, a rack gear 111, a guide rail 112, and an ADF drive gear train 113, which will be described later, are provided in the housing, and an operation panel is provided on the front surface of the housing 11. A document table 12 is provided on the upper surface of the casing 11 as shown in FIG. 1B. The document table 12 is a transparent plate such as a glass plate. By placing the original on the glass plate and setting it, the image can be read through the glass plate (original table 12) by the image reading unit 30 installed at the lower part of the original table 12. The document table cover 13 is connected to the upper portion of the housing 11 and can be opened and closed as shown in FIGS. 1A and 1B. In the ADF drive mode described later, the document table cover 13 is closed, and an image is read in the state shown in FIG. 1A. On the other hand, in the carriage drive mode, the document table cover 13 is opened before the image reading operation is started, and the state shown in FIG. 1B is set. After the document is set on the document table 12, the document table cover 13 is closed and the image is read. An ADF unit 50 is installed on the upper part of the document table cover 13.

  The image reading unit 30 is provided in the housing 10 at a position facing the document via the document table 12 described above, and reads an image from the document in accordance with an image reading command from the control unit 60. FIG. 2 is a diagram for explaining an image reading method by the image reading unit 30. The image reading unit 30 includes a light source 31, a mirror 32, a lens 33, and a light receiving sensor 34. The light source 31 irradiates light on a document set on the document table 12 through a glass plate of the document table 12. The light reflected by the document is guided to the lens 33 by the mirror 32 while changing the course. A plurality of mirrors 32 are provided, and the distance from the document to the lens 33 can be adjusted by repeating the reflection by these mirrors 32. In addition, the broken line in a figure has shown the locus | trajectory of reflected light. The reflected light transmitted through the lens 33 is received by the light receiving sensor 34 with the focus adjusted.

  In the present embodiment, the light source 31 includes, for example, RGB light emitting diodes (hereinafter also referred to as LEDs). Then, the LEDs of the respective colors emit light while being switched in order, and red (R), green (G), and blue (B) light is emitted sequentially at a predetermined cycle, whereby reflected light reflected from the document is The light is incident on the light receiving sensor 34 in the state of being separated into RGB color components. The light receiving sensor 34 includes a linear CCD sensor in which a plurality of photoelectric conversion elements such as photodiodes that convert optical signals into electric signals are arranged in a line along the main scanning direction of FIG. 1A. As a result, it is possible to read an image in the main scanning direction. The image in the sub-scanning direction can be read by moving the image reading unit 30 in the sub-scanning direction that intersects the main scanning direction. Note that the light receiving sensor 34 may employ a configuration of a contact image sensor (CIS image sensor: Contact Image Sensor).

  The carriage unit 40 moves in the sub-scanning direction in parallel with the document set on the document table 12 while supporting the image reading unit 30.

  FIG. 3 is a schematic diagram showing the configuration of the carriage unit 40. The carriage unit 40 includes an image reading unit 30 support unit and a motor support unit. The image reading unit 30 support unit supports the image reading unit 30, and the motor support unit supports the motor 41 and the gear train 42. The carriage unit 40 is supported by guide rails 112 installed along the sub-scanning direction inside the housing 11. When moving in the sub-scanning direction, the guide rail 112 moves while being guided.

  In the present embodiment, a stepping motor is used as the motor 41. When the motor 41 rotates, the gear wheel train 42 rotates via a worm gear attached to the output shaft of the motor 41. The rack gear 111 installed along the sub-scanning direction inside the housing 11 and the gear wheel train 42 mesh with each other, so that the entire carriage unit 40 moves in the sub-scanning direction along the rack gear 111 from side to side. That is, the motor 41 has a function as a drive unit for moving the carriage 40 on which the image reading unit 30 is mounted along the sub-scanning direction. The drive control of the motor 41 is performed by a control signal from the control unit 60. Further, the motor 41 can freely change the rotation direction, and the movement direction of the carriage 40 is changed by changing the rotation direction.

  In the ADF drive mode, the gear wheel train 42 is disengaged from the rack gear 111 and meshes with the ADF drive gear train 113 provided adjacent to the rack gear 111 as described later. Thus, in the ADF drive mode, the image reading unit 30 (carriage 40) reads an image in a state where movement in the sub-scanning direction is stopped.

  The ADF unit 50 is provided on the document cover 13 and reads an image while conveying the document to the position of the image reading unit 30 in the ADF drive mode. FIG. 4 is a diagram illustrating a state in which a document is conveyed by the ADF unit 50 in the ADF drive mode. As shown in FIGS. 1A and 4, the ADF unit 50 includes a document tray 55 and a plurality of transport rollers inside the ADF. The document tray 55 is provided with a document sensor (not shown). If a document is set on the document tray 55 when an image reading command is issued from the control unit 60, the document is detected by the document sensor, and "ADF drive mode" is selected. When the ADF drive mode is selected, the conveyance roller starts to rotate and the document is conveyed into the ADF unit 50. If no document is detected on the document tray 55 when an image reading command is issued from the control unit 60, the “carriage drive mode” is selected, and the drive of the carriage unit 40 is started.

  The document transported from the document tray 55 into the ADF is transported to the back side of the document cover 13 by the transport roller. The image reading unit 30 reads an image when passing through a position facing the image reading unit 30 with the document table 12 interposed therebetween. (See FIG. 4). The document after the image is read is guided to the outside of the ADF by the transport roller, and is discharged to a discharge tray (see FIG. 1) provided on the upper part of the document cover.

  A transport roller inside the ADF unit 50 is driven by a motor 41 provided in the carriage unit 40. That is, the motor 41 has a function as a drive unit that provides a driving force for conveying a document when the ADF is driven, in addition to a function as a drive unit of the carriage unit 40. Details of the operation of the motor 41 will be described later.

  The controller 60 controls the rotation direction and rotation speed of the motor 41 to drive the carriage unit 40 and the ADF unit 50, and causes the image reading unit 30 to read a document. The controller 60 also selects a unit to be driven (in the present embodiment, the carriage unit 40 or the ADF unit 50) based on a signal from a document sensor provided on the document tray 55.

  FIG. 5 is a schematic diagram showing the configuration of the controller 60. As shown in the figure, the controller 60 includes a CPU 61, a ROM 62, a RAM 63, an EEPROM 64, an ASIC 65, a motor driver 66, and the like, which are connected to each other via a transmission path 67 such as a bus. The control unit 60 is connected to the computer COM. The motor 41 is controlled by the cooperation of these hardware and software and / or data stored in the ROM 62 or the EEPROM 64, or by adding a circuit or a component for performing a specific process.

  The CPU 61 has an RTC (Real Time Clock) function that can measure time even when the power is OFF. In the present embodiment, the RTC is used to measure an elapsed time from when the power source of the image reading apparatus 1 is turned off to when it is next turned on.

<Driving of Carriage 40 and ADF 50>
In the image reading apparatus 1 of the present embodiment, two types of operations of “carriage driving mode” and “ADF driving mode” are realized by using a single motor 41. Hereinafter, the driving of each unit and the switching method of each mode will be described.
FIG. 6A is a diagram for explaining the operation in the carriage drive mode. FIG. 6B is a diagram for explaining the operation in the ADF drive mode.

  When reading an image from a document set on the document table 12 in the “carriage driving mode”, the image reading unit 30 mounted on the carriage 40 is moved in the sub-scanning direction to read the image. That is, the image is read by moving the carriage 40 (image reading unit 30) with respect to the document whose position is fixed. When the carriage unit 40 is driven, the gear train 42 provided on the carriage unit 40 and the rack gear 111 provided on the housing 11 are engaged with each other, so that the carriage unit 40 moves along the guide rail 112. That is, when the gear train 42 is in the range of the teeth of the rack gear 111 (hereinafter also referred to as a carriage drive region), the carriage unit 40 is driven.

  On the other hand, in the “ADF driving mode”, the image is read while automatically conveying the document to the position of the image reading unit 30 in the stopped state (see FIG. 4). That is, an image is read from the moving document by the image reading unit 30 (carriage 40) whose position is fixed. Since the document is automatically conveyed, when the operation of setting the document on the document table 12 is omitted and the image is read, for example, the number of documents is large and each document is set on the document table 12 one by one. This is useful when you want to read images without any problems.

  The driving of the ADF is performed by rotating the ADF driving gear train 113. The ADF drive gear train 113 is provided adjacent to the rack gear 111 as shown in FIG. 6B, and is arranged at a position where the gears of the ADF drive gear train 113 are arranged on a straight line of the gear train of the rack gear 111. When the carriage unit 40 moving in the sub-scanning direction passes through the carriage drive region and reaches the region of the adjacent ADF drive gear train 113, the gear train 42 provided in the carriage unit 40 disengages the rack gear 111 and performs ADF drive. Engage with the gear train 113. As a result, the carriage unit 40 stops moving in the sub-scanning direction and rotates the ADF drive gear train 113. The output shaft of the ADF drive gear train 113 is connected to the transport roller of the ADF unit. Therefore, the conveyance roller of the ADF unit 50 can be rotationally driven by the rotation of the motor 41 via the gear wheel train 42 and the ADF drive gear train 113. Then, at the position where the carriage unit 40 (image reading unit 30) is stopped (see FIG. 6B), the document conveyed by the ADF unit 50 is read.

  Note that when switching from the ADF drive mode to the carriage drive mode, the motor 41 may be rotated in the reverse direction. When the motor 41 rotates in the reverse direction, a planetary gear (not shown) is disengaged from the ADF drive gear train 113 and stops the rotation of the ADF drive gear train 113. Since the ADF drive gear train 113 does not rotate, the gear train 42 moves in the sub-scanning direction to the carriage drive region and meshes with the rack gear 111 again. As a result, the ADF driving state is switched to the carriage driving state.

<About the amount of heat generated by the motor 41>
By the way, the motor 41 generates heat by driving the carriage unit 40 or the ADF unit 50. In the carriage drive mode, when the carriage unit 40 reciprocates in the sub-scanning direction, the surrounding air moves while stirring, so the motor 41 that moves with the carriage unit 40 can be cooled.
On the other hand, in the ADF drive mode, since the carriage is stopped as described above, the cooling is insufficient, and the heat dissipation of the motor 41 is impaired as compared with the carriage drive mode. Further, depending on the arrangement (layout) of the ADF drive gear train 113 and the like, heat may easily accumulate in a narrow space surrounded by the housing 11 and the carriage unit 40 when the ADF is driven. Further, since the document transport operation is performed when the ADF is driven, more current is consumed than when the carriage is driven, and heat is easily generated.
That is, the heat generation characteristics and heat dissipation characteristics of the motor 41 are greatly different between the carriage driving and the ADF driving.

=== First Embodiment ===
In the first embodiment, the amount of heat generated by the motor 41 is calculated separately for the carriage drive mode and the ADF drive mode. Then, a “pause time” for pausing the operation of the motor 41 according to the amount of heat generated in each case is provided. Thereby, the calorific value of the motor 41 is appropriately limited.

<Method of limiting calorific value>
FIG. 7 shows a flow for limiting the amount of heat generated by the motor 41.

(S101: Initial setting)
First, initial setting is performed. When the power supply of the image reading apparatus 1 is turned on, the temperature ΔT_sum (EE) of the motor 41 at the previous operation recorded in the EEPROM 64 and the elapsed time Tp from the time when the power supply was turned off are called. Then, the amount of heat radiation with the passage of time from when the power supply is turned off to when the power supply is turned on is calculated, and the current temperature ΔT_sum of the motor 41 is calculated. This value is recorded in the EEPROM 64 as the initial set temperature, and the image reading operation is started. Note that the elapsed time Tp is initialized to zero at the stage when the processing of S101 is completed.

(S102: Calculation of effective current value)
After the image reading operation is started, the effective current value I_cur flowing through the motor 41 is calculated by the CPU 61 every minute. The reason why the effective current value is calculated every minute is to calculate the amount of change in the heat generation temperature over time from the effective current value in the subsequent steps (S104, S107, etc.). Note that the interval for calculating the current is not limited to one minute, and may be shorter or longer.

  For calculating the effective current value I_cur, a constant table that defines the effective current value with respect to the set current value is used. The constant table is created based on the current value experimentally investigated in advance in the manufacturing stage of the image reading apparatus 1 and is stored in the RAM 63 of the control unit 60. The CPU 61 calculates an effective current value I_cur based on the set current value, using a constant table created and stored in accordance with the characteristics of the motor 41 (stepping motor) used in the present embodiment.

(S103: Determination of drive mode)
Subsequently, it is determined whether the current operation is “carriage drive mode” or “ADF drive mode”. That is, it is determined which unit of the carriage unit 40 or the ADF unit 50 is currently driven by the motor 41. As described above, in the present embodiment, the heat generation / heat radiation characteristics of the motor 41 are different between the “carriage drive mode” and the “ADF drive mode”. Therefore, in order to appropriately limit the heat generation amount, it is necessary to calculate the heat generation temperature of the motor 41 separately for each mode. Therefore, the current operating state of the motor 41 is determined in S103.

  The current operation mode is determined based on whether or not a document is set on the document tray 55 when an image reading command is issued from the control unit 60. As described above, in the image reading apparatus 1, the ADF drive mode is selected when the document sensor provided on the document tray 55 detects the document, and the carriage drive mode is selected when the document is not detected. Therefore, when the image reading operation is started, the operation mode can be determined based on whether or not the document is set on the document tray 55.

  If it is determined in S103 that the carriage drive mode is selected, the process proceeds to S104, and the heat generation temperature in the carriage drive mode is calculated (S104). On the other hand, if it is determined that the ADF drive mode is selected, the process proceeds to S107, and the heat generation temperature in the ADF drive mode is calculated (S107).

(S104: Calculation of estimated heat generation temperature of motor 41 in carriage drive mode)
In S104, the estimated heat generation temperature of the motor 41 in the carriage drive mode is calculated. The calculation of the heat generation temperature is performed as follows.

Generally, the calorific value Q is obtained by the equation Q = k · W (k: coefficient for converting work W into heat). Here, W = i ² · R · t. That is, Q = k · i ² · R · t. Therefore, the CPU 61 can obtain the heat generation amount Q_cur per minute based on the current value I_cur obtained every minute in S102. Further, the CPU 61 obtains the heat generation amount Q_sigma per unit time (here, every minute) by integrating the heat generation amount Q_cur per minute. The initial value of the calorific value Q_sigma is a value obtained from ΔT_sum set in S101, and here it is set to zero for the sake of simplicity of explanation. The calorific value Q_sigma is reset every time a unit time elapses. Therefore, when the motor 41 is not driven once in a unit time, the heat generation amount Q_sigma is “0”.

  Next, the CPU 61 converts the heat generation amount Q_sigma for 1 minute into a heat generation temperature ΔT_new. ΔT_new is obtained by the equation ΔTnew = Kc · Q_sigma. Here, Kc is a conversion coefficient from the heat generation amount Q to the heat generation temperature ΔT_new in the carriage drive mode, and is a value obtained by a preliminary experiment in the manufacturing process of the image reading apparatus 1. The coefficient Kc obtained in the manufacturing process is stored in the RAM 63 as a heat generation parameter in the carriage drive mode.

  FIG. 8 is an explanatory diagram of the total heat generation temperature T_sum. As shown in the figure, the heat generation temperature due to energization for the first one minute is ΔT1_new, the heat generation temperature due to the next one minute energization is ΔT2_new, and the heat generation temperature due to the next one minute energization is ΔT3_new. The first heat generation temperature ΔT1_new decreases along the heat dissipation curve with time, and after one minute, it decreases to ΔT1_old due to natural heat dissipation. Therefore, the total heat generation temperature ΔT2_sum in the second minute is expressed by ΔT2_sum = ΔT1_old + ΔT2_new. Further, the total heat generation temperature ΔT2_sum in the second minute decreases along the heat radiation curve with time, and after one minute, it decreases to ΔT2_old by natural heat dissipation. Therefore, the total heat generation temperature ΔT3_sum for the third minute is represented by ΔT3_sum = ΔT2_old + ΔT3_new.

  Here, the exothermic temperature ΔT_old that reaches ΔT_sum by dropping along the heat dissipation curve after 1 minute is expressed as ΔT_old = K1c · ΔTsum using the heat dissipation coefficient K1c. The heat dissipation coefficient K1c is obtained by a preliminary experiment in the manufacturing process of the image reading apparatus 1 and is stored in the RAM 63 as a heat generation parameter in the carriage drive mode, as with the above-described Kc.

  The latest total heat generation temperature ΔTn_sum is calculated by adding the latest heat generation temperature ΔTn_new to the value obtained by multiplying the previous total heat generation temperature ΔTn-1_sum by the heat release coefficient K1, and is obtained by the equation ΔTn_sum = K1 · ΔTn-1_sum + ΔTn_new. The total heat generation temperature ΔTn_sum is a temperature increase due to heat storage of the motor 41. The CPU 61 adds the total heat generation temperature ΔTn_sum to the room temperature to calculate the estimated heat generation temperature ΔTn_sum (C) of the motor 41 when the carriage is driven. By using the heat generation parameters Kc and K1c in this way, it is possible to accurately calculate the estimated temperature in the carriage drive mode.

(S105 / S106: Setting of pause time)
When the estimated temperature ΔTn_sum (C) of the motor 41 calculated in S104 exceeds a predetermined threshold TH (C), the control unit 60 drives the motor 41 while performing heat generation restriction control. That is, when the estimated temperature of the motor 41 exceeds a predetermined temperature (S105), the control unit 60 inserts a pause time between the intermittent driving of the motor 41 and sets the interval of intermittent driving of the motor 41. The heat generation is limited by spreading (S106). According to this heat generation restriction control, the heat generation of the motor 41 can be suppressed and the motor 41 can be prevented from becoming high temperature.

  In the carriage drive mode, it is desirable to provide a pause time when the carriage unit 40 reciprocates in the sub-scanning direction and returns to the initial position (home position) at the start of the image reading operation. If a pause time is provided while the carriage unit 40 is moving and the carriage movement is stopped halfway, the user may mistakenly recognize that the carriage unit 40 has stopped due to a failure. In order to prevent such misidentification, the carriage unit 40 is stopped after returning to the initial position.

(S107 to S109: Heat generation restriction in ADF drive mode)
The heat generation restriction in the ADF drive mode is basically the same as the method of heat generation restriction (S104 to A106) in the carriage drive mode.

  However, since the heat generation / heat radiation characteristics of the motor 41 are different, the conversion coefficient K from the heat generation amount Q to the heat generation temperature ΔT_new and the heat radiation coefficient K1 are different from those in the carriage drive mode (S104). That is, the estimated heat generation temperature ΔTn_sum (A) in the ADF drive mode is calculated using the conversion coefficient Ka and the heat dissipation coefficient K1a in the ADF drive mode (S107). Both Ka and K1a are obtained by preliminary experiments in the manufacturing process of the image reading apparatus 1, and are stored in the RAM 63 as heat generation parameters in the ADF drive mode.

  Further, the threshold value TH (A) for the ADF drive mode is used as the threshold value TH for determining whether or not there is a pause time. That is, when the estimated temperature of the motor 41 calculated in S107 exceeds the threshold value TH (A) (S108), the control unit 60 drives the motor 41 while performing heat generation restriction control (S109). The threshold value TH (C) in the carriage drive mode and the threshold value TH (A) in the ADF drive mode may be the same value or different values.

  In the carriage drive mode, it has been described that the pause time is provided when the carriage unit 40 returns to the initial position (S106). In the ADF drive mode, the pause time is divided according to the document transport operation. For example, in the document transport operation by ADF, the document is first fed, the head is positioned to match the reading position of the document, the actual reading is performed, and the scanned document is discharged outside the ADF. The As described above, the pause time is divided immediately before each of the sheet feeding / cueing / reading / paper discharge operations to provide a pause time for each short period. If a long pause time is provided between the operations, the conveyance operation seems to be interrupted in the middle, and the user may misunderstand that the ADF unit 50 has failed. Therefore, it is assumed that the pause time is divided between the operations of the document conveyance process by the ADF. The balance of the pause time division may be changed by the user himself.

(S110: Stop operation)
When the image reading operation is completed, the image reading apparatus 1 is stopped. In the image reading apparatus 1 of the present embodiment, appropriate heat generation restriction is performed by reflecting the influence of heat generation during the current operation during the next operation. Therefore, when performing the stop operation, the heat generation temperature ΔT_sum (A) or ΔT_sum (C) calculated this time is stored in the EEPROM 64 as the final heat generation temperature ΔT_sum (EE). Further, the CPU 61 measures an elapsed time Tp from the moment when the power is turned off to the next time when the power is turned on, and stores it in the EEPROM 64. These values are used when calculating the initial temperature of the motor 41 during the next operation, as described in the above (S101).

=== Comparative Example ===
For reference, an image reading apparatus in the case where the calculation of heat generation of the motor is shared between the carriage driving mode and the ADF driving mode is shown as a comparative example.

  FIG. 9 is a diagram illustrating a flow for limiting the amount of heat generated by the motor 41 in the comparative example. In the comparative example, there is no processing corresponding to S103 of the first embodiment, and it is not determined which mode is selected between the carriage driving mode and the ADF driving mode. In S203, the heat generation calculation is performed, and the calculated estimated heat generation temperature ΔTn_sum is calculated as a common heat generation temperature in the carriage driving mode and the ADF driving mode. That is, the conversion coefficient K from the heat generation amount Q to the heat generation temperature ΔT_new and the heat dissipation coefficient K1 are common values in the carriage drive mode and the ADF drive mode. Then, the threshold value TH common to both modes in S204 is compared with the calculated estimated heat generation temperature ΔTn_sum, and if ΔTn_sum> TH, the heat generation restriction process is performed in S205. Since the determination of the drive mode is not made, the setting of the pause time is common to both modes, and the unit in operation is forcibly paused at the moment when the heat generation temperature ΔTn_sum exceeds the threshold value TH. Other operations are the same as those in the first embodiment.

  As described above, since the heat generation characteristics and the heat dissipation characteristics are different between the carriage drive mode and the ADF drive mode, a heat generation restriction process corresponding to each mode is necessary. However, in the case of the comparative example, since the heat generation restriction process common to each mode is performed, the heat generation restriction of the motor becomes insufficient or a useless downtime is provided. For example, when the heat generation limit value is adjusted to the carriage drive mode, the pause time is short in the ADF drive mode, and the motor may not be sufficiently cooled. Also, with the heat generation limit value matched to the ADF drive mode, the pause time is long in the carriage drive mode, and the image reading time may be delayed by stopping the carriage unnecessarily.

=== Summary ===
In the image reading apparatus of the present embodiment, two different mechanisms of the carriage unit 40 and the ADF unit 50 on which the image reading unit 30 is mounted are driven by one motor 41. An estimated heat generation temperature ΔTn_sum (C) when the motor 41 drives the carriage unit 40 (carriage drive mode) and an estimated heat generation temperature ΔTn_sum (A) when the motor drives the ADF unit 50 (ADF drive mode). Are calculated separately.

  Thereby, the exact heat_generation | fever amount of a motor can be obtained corresponding to the magnitude | size of the load concerning the motor at the time of both modes, and the difference in heat dissipation conditions. By providing an optimal pause time according to the calorific value calculated for each mode, the motor can be appropriately cooled during the image reading operation.

=== Other Embodiments ===
Although the image reading apparatus as one embodiment has been described, the above embodiment is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About motor>
In the above-described embodiment, the stepping motor is used as the motor 41. However, the motor 41 is not limited to the stepping motor. For example, a DC motor can be used.
When a DC motor is used, it is possible to calculate the effective current value from the load when the motor is used, so there is no need to create a constant table of effective current values by preliminary experiments at the manufacturing stage, There is no need to record the constant table in the RAM of the control unit. Further, by using the encoder, it is possible to detect the movement position of the carriage to which the motor is attached during the image reading operation.

<About the control unit>
The control unit 60 is not limited to the above-described embodiment, and may be configured to control the motor 41 with only the ASIC 65, for example. In addition, one chip in which various peripheral devices are incorporated. The control unit 60 may be configured by combining microcomputers or the like.

10 image reader, 11 housing, 12 document table, 13 document table cover,
111 rack gear, 112 guide rail, 113 ADF drive gear train 30 image reading unit, 31 light source, 32 mirror, 33 lens,
34 light receiving sensor, 40 carriage section, 41 motor, 42 gear train,
50 ADF section, 55 document tray, 60 control section

Claims (8)

A document transport section for transporting a document;
An image reading unit for reading an image from the original;
A carriage unit that moves while supporting the image reading unit; a driving unit that drives the document conveying unit and the carriage unit;
A first mode in which the carriage unit is driven by the driving unit to read an image from the document in a stopped state, and a position of the image reading unit in a stopped state by driving the document conveying unit by the driving unit. A second mode for reading an image while conveying the original document, and a control unit for controlling the second mode;
An image reading apparatus for forming image data from data obtained by reading the original,
The controller is
In the first mode, the heat generation amount of the drive unit is calculated using the first heat generation parameter,
In the second mode, the heat generation amount of the drive unit is calculated using a second heat generation parameter different from the first heat generation parameter. The image reading apparatus according to claim 1,
An image reading apparatus, wherein the driving unit is mounted on the carriage unit. The image reading apparatus according to claim 1 or 2,
In the first mode, the heat generation of the drive unit is limited based on the heat generation amount of the drive unit calculated using the first heat generation parameter,
In the second mode, the heat generation of the drive unit is limited based on the heat generation amount of the drive unit calculated using the second heat generation parameter. The image reading apparatus according to claim 3,
An image reading apparatus that limits heat generation of the driving unit by providing a pause time during which the driving of the document conveying unit or the carriage unit is stopped during an image reading operation. The image reading apparatus according to claim 4,
When limiting the heat generation of the drive unit in the first mode,
An image reading apparatus that stops driving of the carriage unit in accordance with the pause time after the carriage unit moves to an original position at the start of an image reading operation. The image reading apparatus according to claim 4,
When limiting the heat generation of the drive unit in the second mode,
Dividing the pause time into a plurality of
An image reading apparatus that stops driving of the ADF unit according to the divided pause time at every predetermined timing during an operation in which the document conveying unit conveys the document. The image reading apparatus according to claim 1,
The initial heat generation amount of the drive unit at the start of the image reading operation is
An image reading apparatus, wherein the image reading device is calculated based on a temperature of the driving unit at the time of a previous image reading operation. Conveying the document by the document conveying section;
Reading an image from the document by an image reading unit;
Moving the image reading unit while supporting it by a carriage unit;
Driving the document conveying section and the carriage section by a driving section;
The control unit drives the carriage unit with the driving unit to read an image from the document in the stopped state, and drives the document conveying unit with the driving unit to stop the image in the stopped state. Controlling the second mode in which the image is read while conveying the document to the position of the reading unit;
An image reading method comprising:
The controller is
In the first mode, the heat generation amount of the drive unit is calculated using the first heat generation parameter,
In the second mode, the heat generation amount of the driving unit is calculated using a second heat generation parameter different from the first heat generation parameter.