JP2000221225A - Disconnection sensor and image input device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a disconnection of wiring for transmitting a control signal from a control board to a drive board. SOLUTION: A control circuit mounted on a control board 100 counts number of times of changes of a clock signal transmitted from the board 100 to a drive board 300 by a counter 5A. The signal transmitted to the board 300 is returned to the board 100 through an AND gate 9, and number of times of the changes of the returned signal is counted by a counter 5B. A processor 3 decides the effect that a disconnection occurs at any of wiring group 200 for wiring the boards 100 and 300 in the case that a counted value of the counter 5A is different from that of the counter 5B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disconnection detecting device and an image input device provided with the disconnection detecting device.

[0002]

2. Description of the Related Art An image input apparatus such as a copying machine has a drive circuit for driving a movable portion such as a scanner. The drive circuit is directly connected to a stepping motor for driving the scanner. Therefore, noise is easily generated. on the other hand,
The image input device includes a control circuit for controlling each part of the device in addition to the drive circuit. If the drive circuit and the control circuit are formed on the same printed circuit board, noise generated in the drive circuit is input to the control circuit, and the control circuit may run away. For this reason, the drive circuit is mounted on a drive board separate from the control board on which the control circuit is mounted, and these period plates are connected by wiring, and a control signal from the control circuit is transmitted to the drive circuit via the wiring. Such a configuration is generally adopted.

[0003]

However, in the above configuration, the wiring connecting the control board and the drive board may be disconnected. When this wiring is broken, various problems occur. For example, when a control signal line of a fan used for cooling the device is disconnected, even if a signal to be driven is output from the control circuit, the signal is not input to the drive circuit and the fan stops. Accordingly, the temperature of the apparatus main body continues to rise abnormally, causing an abnormality in the control circuit and the like.
In order to prevent such a problem beforehand, a simple means for detecting disconnection of the wiring connecting the two substrates is required.

Therefore, the present applicant has conducted a prior art search in order to obtain a simple means for detecting such a disconnection, but has failed to find a suitable one. For example, Japanese Patent Laid-Open No. 5-2
Japanese Patent Application Laid-Open No. 15536 discloses an apparatus including a position detector and a motor control device. In order to detect disconnection of an output signal line of an encoder in the position detector, an encoder is provided on both the position detector side and the motor control device side. And a circuit for generating a pulse from the output signal and counting the number of pulses. That is, when the output signal line of the encoder is disconnected, the output signal level becomes unstable, and the difference between the count value obtained by the circuit on the position detector side and the count value obtained by the circuit on the motor control device side is utilized. To detect disconnection. However, a problem in the image input device is the disconnection of the wiring for transmitting the control signal between the two types of boards. It cannot be applied to disconnection detection between the two.

[0005] Also, Japanese Patent Application Laid-Open No. Hei 4-326410 discloses that
A clock monitoring device that detects a clock abnormality by counting the number of clocks is disclosed. In accordance with the teachings of this publication, a method may be considered in which a counter for obtaining the clock frequency sent from the control board is provided on the drive board, and it is determined that a disconnection has occurred when the clock frequency deviates from a predetermined range. However, the control signal sent from the control board to the drive board includes not only such a steady clock but also a single pulse which is sent only when a certain condition is satisfied. Regarding the wiring for transmitting such a control signal, it is impossible to detect a disconnection even if the frequency of the control signal supplied via the wiring is obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and it is possible to detect disconnection of a wiring for transmitting a control signal from a control board to a drive board, and furthermore, it is possible to provide an inexpensive structure. It is an object of the present invention to provide a disconnection detecting device capable of performing the above-described operation and an image input device including the disconnection detecting device.

[0007]

SUMMARY OF THE INVENTION The present invention provides a moving part,
A control circuit is mounted on a device including a drive board on which a drive circuit for driving the movable portion is mounted, and a control board on which a control circuit for generating a control signal is mounted, and transmits a control signal from the control circuit to the drive circuit. Control signal feedback means for returning a control signal sent from the control circuit to the drive circuit through the wiring to the control circuit, and the control circuit The first counts the number of changes of the control signal transmitted to the circuit.
Counting means, a second counting means for counting the number of changes of the control signal returned to the control circuit by the control signal feedback means, a count value of the first counting means and the second counting means And a determination means for determining that the wiring is disconnected when the count value is different from the above.

According to this invention, the control board counts the number of changes in the control signal sent to the drive board and counts the number of changes in the control signal returned from the drive board. By comparing the count values, the presence or absence of disconnection is determined.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. A. First Embodiment FIG. 1 is a block diagram showing a configuration of an image input device according to a first embodiment of the present invention. This image input device has movable members such as a scanner and a fan. The drive substrate 300 shown in FIG. 1 is a substrate on which a drive circuit for driving such a movable member is mounted. FIG. 1 illustrates a driving unit 10A and a driving unit 10B as driving targets of the driving circuit. Further, the image input device has a control circuit for controlling each unit, and this control circuit is mounted on the control board 100 shown in FIG. Then, the control board 100
And the drive board 300, the drive clock line 2
0A, a confirmation clock line 20B and a drive signal line 20C are interposed.

Next, the configuration of a control circuit mounted on the control board 100 will be described. In the control board 100,
1 is a ROM in which a program is stored in advance, 2 is a RAM which is a temporary storage means, 3 is an arithmetic processing unit which outputs a control signal to each unit of the image input device according to the program stored in the ROM 1, and 4 is a timing control of each unit of the device. , 5A and 5B are counters for counting the number of input pulses, and 6 is a buffer.

One of the timing signals generated by the timing generator 4 is a driving clock signal a
There is. The drive clock signal a is a signal for controlling the drive timing of the drive unit 10A, and is transmitted to the drive control unit 8A via the drive clock line 20A. The counter 5A counts the number of pulses of the drive clock signal a output from the timing generator 4 to the drive clock line 20A. The drive clock signal a sent to the drive control unit 8A passes through an AND gate 9 described later, becomes a check clock signal b via a check clock line 20B, and is returned to the control board 100. Counter 5B
Counts the number of pulses of the confirmation clock signal b. Here, the input terminal of the counter 5B to which the confirmation clock signal b is input is grounded via the pull-down resistor 7A. The count values of the counters 5A and 5B are sent to the arithmetic processing unit 3 and compared. The driving signal c is output from the arithmetic processing unit 3 via the buffer 6, and the driving signal line 2
The data is transmitted to the drive control unit 8B via OC. The drive signal c is a continuous signal, and at least the drive clock signal a
Is always at the high level while is output.

Next, the configuration of the drive circuit mounted on the drive board 300 will be described. First, the drive control unit 8A
Drive clock signal a via drive clock line 20A
Is a means for controlling the drive of the drive unit 10A. Here, the input terminal of the drive control unit 8A to which the drive clock signal a is input is grounded via the pull-down resistor 7B. Next, the drive control unit 8B is a unit that performs drive control of the drive unit 10B by receiving a high-level drive signal c via the drive signal line 20C. The drive control unit 8B to which the drive signal c is input
Are grounded via a pull-down resistor 7C. The AND gate 9 outputs a confirmation clock signal b which is a logical product of the driving clock signal a supplied via the driving clock line 20A and the driving signal c supplied via the driving signal line 20C. It is.
This confirmation clock signal b is transmitted to the confirmation clock line 20B.
, The data is returned to the counter 5B in the control board 100 described above.

In such a configuration, when the drive clock signal a is output from the timing generator 4, the arithmetic processing unit 3 issues a count start instruction to the counters 5A and 5B. The counters 5A and 5B count the number of pulses of the driving clock signal a and the number of pulses of the confirmation clock signal b until the output of the driving clock signal a is stopped and a counting end command is issued.

(1) All wirings 20A, 20B and 2
FIG. 2 is a waveform diagram showing signal waveforms at various parts in this case.
In this case, the drive clock signal a output from the timing generator 4 is transmitted via the drive clock line 20A, and is input to the drive control unit 8A and one input terminal of the AND gate 9. The drive signal c output from the arithmetic unit 3 is transmitted via the drive signal line 20C, and is input to the drive unit 8B and the other input terminal of the AND gate 9. Here, the drive signal c is set to the high level by the arithmetic processing unit 3 at least during a period in which the drive clock signal a is output from the timing generator 4. Accordingly, the drive clock signal a sent from the control board 100 via the drive clock line 20A during this time is output as it is from the AND gate 9 as the confirmation clock signal b. This confirmation clock signal b is returned to the control board 100 via the confirmation clock line 20B. In the control board 100, the timing generator 4
The counter 5A counts the number of pulses of the drive clock signal a output from the counter 5A, while counting the number of pulses of the confirmation clock signal b returned via the confirmation clock line 20B. Here, the waveform of the driving clock signal a and the confirmation clock signal b
Are the same as shown in FIG. 2, so that the count values of the counters 5A and 5B match.
The arithmetic processing unit 3 confirms that the count values of the two counters are the same, so that all the wirings 20A,
It is determined that no disconnection has occurred in 20B and 20C.

(2) When the Drive Clock Line 20A is Disconnected FIG. 3 shows each part when the drive clock line 20A is disconnected while the drive clock signal a and the high-level drive signal c are supplied to the drive substrate 300. FIG. 4 is a waveform diagram showing a signal waveform. In this case, when the drive clock line 20A is broken, the supply of the drive clock a to the drive substrate 300 via this line is cut off, and the level of one input terminal of the AND gate 9 is fixed to the low level by the pull-down resistor 7B. Is done. For this reason, the output signal level of the AND gate 9 is also fixed to the low level, and the supply of the confirmation clock signal b to the control board 100 is stopped. Therefore, on the control board 100 side, the count value of the pulse number of the confirmation clock signal b by the counter 5B remains stopped after the disconnection of the drive clock line 20A, despite the count value of the counter 5A increasing. The arithmetic processing unit 3
Since the difference between the count values of the two counters has occurred, it is determined that a disconnection has occurred in any of the wirings 20A, 20B, and 20C.

(3) When the Drive Signal Line 20C is Disconnected FIG. 4 shows each part when the drive signal line 20C is disconnected while the drive clock signal a and the high-level drive signal c are supplied to the drive substrate 300. FIG. 4 is a waveform diagram showing a signal waveform. In this case, when the drive signal line 20C is broken, the supply of the drive signal c to the drive substrate 300 via this line is cut off, and the level of one input terminal of the AND gate 9 is fixed to a low level by the pull-down resistor 7C. Is done. For this reason, the output signal level of the AND gate 9 is also fixed to the low level, and the supply of the confirmation clock signal b to the control board 100 is stopped. Therefore, on the control board 100 side, after the drive signal line 20C is disconnected, the counter 5
Although the count value of A increases, the counter 5B
, The count value of the number of pulses of the confirmation clock signal b remains stopped. The arithmetic processing unit 3 determines that the count values of the two counters differ from each other,
It is determined that a disconnection has occurred in any of A, 20B and 20C.

(4) Case in which the Confirmation Clock Line 20B is Disconnected FIG. 5 shows the components of the respective parts when the confirmation clock line 20B is disconnected during a period in which the drive clock signal a and the high-level drive signal c are supplied to the drive substrate 300. FIG. 4 is a waveform diagram showing a signal waveform. In this case, when the check clock line 20B is disconnected, the supply of the check clock b to the control board 100 via this line is cut off, and the level of one input terminal of the counter 5B is fixed to the low level by the pull-down resistor 7A. You. Therefore, on the control board 100 side, after the disconnection of the confirmation clock line 20B, the count value of the number of pulses of the confirmation clock signal b by the counter 5B remains stopped despite the count value of the counter 5A increasing. The arithmetic processing unit 3 determines that any of the wirings 20A, 20B, and 20C has a disconnection because the count values of the two counters differ as described above.

In the above-described embodiment, the logical product of the driving clock signal a and the driving signal c is returned to the control board as the confirmation clock signal b. Some devices may not be supplied with anything to do. In such an apparatus, the drive clock signal a sent from the control board to the drive board may be directly returned to the control board as the confirmation clock signal b.

In the above-described embodiment, the wiring for transmitting the periodic drive clock signal a is targeted for disconnection detection. However, the wiring for other general control signals whose level changes at irregular timing is replaced by the wiring. It may be a target of disconnection detection.
In this case, the control board counts the number of rises of the control signal, for example, counts the number of rises of the control signal returned to the control board after being sent to the drive board, and determines whether the two count values are different. It may be determined whether there is a disconnection in the wiring for the control signal.

B. Second Embodiment In the first embodiment, the line connecting the control board on which the control circuit is mounted and the drive board on which the drive circuit is mounted is targeted for disconnection detection. However, actually, there are lines such as power supply voltages that are input from other modules to the control board and the drive board, and such lines also require disconnection detection. Therefore, in the present embodiment, when a power supply voltage is input to the control board and the drive board from another module, the disconnection of the line connecting the power supply and the drive board is also detected. Specifically, it is as follows.

FIG. 6 is a block diagram showing the configuration of an image input device according to a second embodiment of the present invention. In FIG. 6, portions corresponding to those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. In this image input device, the driving substrate 300 includes a stepping motor driving unit 8 instead of the driving control unit 8A in the first embodiment.
A ′ is provided with a fan level driver 8B ′ as a drive circuit instead of the drive controller 8B.

The stepping motor 10A 'and the fan 10B' are driven by each of the above driving circuits. Here, the stepping motor 10A 'is means for driving a carriage (not shown) to perform sub-scanning. The fan 10B 'is a unit for cooling the inside of the image reading device.

The control circuit on the control board 100 is a means for generating various control signals to be supplied to the drive board 300 and the like, and has substantially the same configuration as that in the first embodiment. In this embodiment, the control board 10
CPU 400 is mounted on the
00 performs various functions of the arithmetic processing unit 3, the timing generator 4, and the counters 5A and 5B in the first embodiment. However, the arithmetic processing unit 3 in the present embodiment
Has a function of generating a control signal d in addition to the function of the arithmetic processing unit 3 in the first embodiment. The control signal d is a signal for controlling the stepping motor 10A ', and is transmitted to the stepping motor driving unit 8A' via the control signal line 20D.

A low-voltage power supply (hereinafter abbreviated as LPVS) 1
1 generates a voltage e of 24V and a voltage f of 5V. Then, the CPU 400, the ROM1, and the R
The voltage f of 5 V generated by the LPVS 11 is supplied to the AM 2 and the buffer 6 as a power supply voltage.

The drive board 300 is supplied with a voltage e of 24 V and a voltage f of 5 V generated by the LPVS 11 via lines 20E and 20F, respectively. The voltage e of 24 V is applied to the stepping motor driving unit 8.
A ′ and the fan drive unit 8B ′ are supplied as a power supply voltage. A power supply line for supplying a power supply voltage to the stepping motor drive section 8A 'and the fan drive section 8B' is grounded via a pull-down resistor 7D. Also, 24
The voltage e of V is converted into 5 V by the voltage level converter 12 and supplied to the AND gate 9. Driving board 300
Is supplied as a power supply voltage to various logic circuits such as the AND gate 9. According to the present embodiment, in addition to the excitation clock signal a and the drive signal b supplied from the control board 100 side, the 5 V voltage obtained from the voltage level converter 12 is also input to the AND gate 9. Therefore, even when the line 20E for transmitting the power supply voltage of 24V is disconnected in addition to the wiring for transmitting the excitation clock signal a and the drive signal b, the detection can be performed.

That is, when the line 20E is disconnected during transmission of the excitation clock signal a from the control board 100 to the drive board 300, the voltage of the voltage level converter 12 does not output a voltage of 5V. As a result, the output signal of the AND gate 9 is fixed at the low level, and the supply of the confirmation clock b to the counter 5B on the control board 100 is interrupted. Then, the arithmetic processing unit 3 detects the disconnection of the wiring from the difference between the count values of the counters 5A and 5B.

[0027]

As described above, according to the present invention,
A movable section, mounted on a device including a drive board on which a drive circuit for driving the movable section is mounted, and a control board on which a control circuit for generating a control signal is mounted, from the control circuit to the drive circuit In a disconnection detecting device for detecting disconnection of a wiring for transmitting a control signal, control signal feedback means for returning a control signal sent from the control circuit to the drive circuit through the wiring to the control circuit; First counting means for counting the number of changes in the control signal transmitted from the circuit to the drive circuit; and second counting means for counting the number of changes in the control signal returned to the control circuit by the control signal feedback means. Counting means, and when the count value of the first counting means is different from the count value of the second counting means, the determination means for determining that the wiring is broken, provided There is an effect that can detect the disconnection of the line connecting the control substrate and the driving substrate.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image input device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing signal states in the embodiment.

FIG. 3 is a diagram showing each signal state in the embodiment.

FIG. 4 is a diagram showing each signal state in the embodiment.

FIG. 5 is a diagram showing each signal state in the embodiment.

FIG. 6 is a block diagram showing a configuration of an image input device according to a second embodiment of the present invention.

[Explanation of symbols]

100: control board, 200: wiring, 300
..Drive board 3 ... Calculation processing unit 4 ... Timing generator 5A, 5B ... Counter 9 ... AND gate

Claims (4)

[Claims] 1. A disconnection detection device for detecting disconnection of a wiring for transmitting a control signal from a first module to a second module, wherein the disconnection is detected from the first module to the second module via the wiring. Control signal feedback means for returning the control signal to the first module, first counting means for counting the number of changes of the control signal transmitted from the first module, and A second counting means for counting the number of changes of the control signal returned to the first module; and a wiring when the count value of the first counting means is different from the count value of the second counting means. And a determining means for determining that the wire is disconnected. 2. A movable board such as a scanner for reading an image, a drive board equipped with a drive circuit such as a stepping motor for driving the movable section, a control board equipped with a control circuit for generating a control signal, A disconnection detecting device for detecting disconnection of a wiring for transmitting a control signal from a control circuit to the driving circuit, wherein the disconnection detecting device is configured to transmit the control signal from the control circuit to the driving circuit via the wiring. Control signal feedback means for returning the control signal sent to the control circuit to the control circuit; first counting means for counting the number of changes of the control signal transmitted from the control circuit to the drive circuit; and the control signal feedback means Second counting means for counting the number of changes of the control signal returned to the control circuit, and a count value of the first counting means and a count of the second counting means Doo is if different, the image input apparatus characterized by comprising a determination means for the determination that the wiring is disconnected. 3. A movable section such as a scanner for reading an image, a drive board on which a drive circuit such as a stepping motor for driving the movable section is mounted, and a clock signal and a predetermined level for at least a period during which the clock signal is output. An image input comprising: a control board on which a control circuit for generating a control signal to be generated is mounted; and a disconnection detecting device for detecting disconnection of wiring for transmitting a clock signal and a control signal from the control circuit to the drive circuit. In the device, while the disconnection detection device, while the control signal sent from the control circuit to the drive circuit is maintaining a predetermined level,
A logic circuit for returning a clock signal sent from the control circuit to the drive circuit to the control circuit as a confirmation signal; and a first count for counting the number of changes of the clock signal transmitted from the control circuit to the drive circuit. Means, a second counting means for counting the number of changes of the confirmation signal returned from the driving circuit to the control circuit, a count value of the first counting means and a count value of the second counting means, An image input device comprising: a determination unit configured to determine that the wiring is disconnected when the values are different from each other. 4. The control circuit according to claim 1, wherein the logic circuit is configured to output the control signal from the control circuit during a period in which a voltage supplied from a module other than the control board is maintained at a predetermined level. 4. The image input device according to claim 3, wherein the clock signal sent to the control circuit is returned to the control circuit as a confirmation signal.