JPS5834790B2 - Butsutikenshiyutsusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an object detection device using ultrasonic waves.

More specifically, the present invention relates to an object detection device for preventing an object detection function from being inhibited by influences other than objects.

It is well known to use ultrasound instead of light to detect objects.

However, changes in ultrasonic waves due to objects vary depending on the atmosphere of the space, dirt on the transmitter/receiver, variations in efficiency of the transmitter/receiver, placement of the transmitter/receiver, reflections from sources other than the object, etc.

Since these unstable elements occur almost independently of the state of existence of the object, they increase the detection error.

Conventionally, a transmitter/receiver that is difficult to absorb the above-mentioned unstable factors or a receiver with high reception sensitivity has been used, but for example, copying, which requires an expensive transmitter/receiver and performs secondary detection of objects such as transfer paper, etc. Such a detection device is inappropriate in the device.

To explain this with reference to the drawings, FIG. 1 shows an example of detecting the passage and ejection of transfer paper within a moving path in an electrophotographic apparatus using ultrasonic waves. is a transfer paper, and the transfer paper P is fed to a moving path by a paper feed roller (■) that operates in synchronization with a copy start signal, transfers a visible image from the surface of the photosensitive drum (8) on which the latent image is visualized, and transfers a visible image to the conveyor belt (T). -H, it is conveyed through the fixing unit W and discharged.

That is, when the transfer paper P passes through the transmitter/receiver placed oppositely via the movement path, the ultrasonic transducer (UltraS) of the transmitter
onic 0scillator (hereinafter referred to as USO)
The detection level by the USO on the receiving side is set to O.

Therefore, this O level is determined to be a high level in the reference state, and a transfer paper presence signal is obtained.

However, the ultrasonic waves are not completely blocked by the transfer paper and are reflected on the support material of the transmitter/receiver and sensed by the receiver, causing the receiver to malfunction.

Furthermore, transfer type copying machines tend to generate noise and scattering of developed toner.

Therefore, the reliability of the received signal tends to decrease, and there are many factors that cause the transfer paper detection accuracy to deteriorate.

Further, the reference value for detecting the transfer paper may fluctuate due to external noise or the like, which may lead to erroneous detection.

The present invention eliminates this drawback and improves the reliability of transfer paper detection by arranging transmitter and receiver units facing each other across a transfer paper path, providing screens on them, and providing a predetermined period of time related to the copying operation. A signal from the receiving element is taken into a storage circuit in accordance with a timing signal, and the transfer paper is detected based on this reference value and the signal from the receiving element.

An embodiment will be described with reference to FIGS. 2 to 7.

In FIG. 2, a slit 102 is provided between opposing transceivers 101 and 103, and a paper 105 is detected by detecting ultrasonic waves through the slit. The transmitter/receiver 101,
Interfering waves reflected or wrapped around the support member 104 of 103 are reduced.

In this case, if a slit is provided in the paper guide member 108, there are fewer factors that hinder the movement of the paper.

In the example of the slit in FIG. 3, the slit of the guide member 108 is
This is provided on the front side of the receiver 103 that has a built-in SO.

A ceramic microphone 119 shown in FIG. 4 is used as the receiver 103, and the screen 12 of the microphone is used.
By forming the zero surface into a slit shape, it is possible to omit the slit member.

The narrower the gap between the slits is, the more effective it is, but at least one of them requires the wavelength of ultrasonic waves.

Furthermore, if the narrow portion of the slit is arranged perpendicular to the paper moving direction, the rising accuracy of the paper detection operation will be increased.

In FIG. 5, a cone 107 corresponding to an opening for paper detection is provided between opposing transmitters and receivers 101 and 103 as shown in the figure to prevent scattering of ultrasonic waves and reduce ultrasonic waves that are reflected by supporting materials and the like.

In this case, if the opening corresponding to the cone is made into a slit, the accuracy will be higher, and sufficient accuracy can be obtained with only the cone on the receiver side.

The smaller the angle α of the cone, the better, but since the absolute amount of ultrasonic waves arriving at the receiver will be small, the optimal α is determined experimentally, taking into account the sensitivity of the receiver.

Incidentally, scattering can be conveniently prevented by using the above-mentioned ceramic microphone as a transmitter/receiver and arranging the edge of the conical cone around the shield screen 120.

In Fig. 6, the guide member 108 through which paper passes is an ultrasonic transmission line, and the transmitter 101 is arranged so as to send ultrasonic waves to the guide member 108, and when no paper is carried into the transmission line. The ridge receivers 109 and 11 receive the same amount of reception.
Place 0.

Then, the passage of paper is determined based on the imbalance in the amount of reception when the paper passes through the moving path.

In this case, it is possible to detect the decrease in the amount of reception using only the receiver 109 and determine whether the paper has passed, but since the absolute amount of the received sound waves has decreased, the above detection is more accurate.

Furthermore, if a slit or a cone is used at the opening of the moving path near the receiver, the accuracy will be further improved.

By using the paper movement path as an ultrasonic transmission path in this way, the movement of paper in a long and curved path can be detected with a few small elements.

Figure 7 shows that depending on the location of the transmitter/receiver, if a slit is not provided, the transmitter/receiver is placed diagonally opposite to the direction of paper movement, so that almost all of the ultrasonic waves during paper detection are reflected, increasing the detection accuracy. It is something that

In this case, the appropriate angle of the oblique direction is 20 to 40 degrees in consideration of the sensitivity of the receiver and the installation location of the transceiver in the copying machine.

FIG. 8 shows the distance γ from the transmitter 101 to the detected paper.
is set so that the wave reflected by the paper has exactly the opposite phase to the wave transmitted by the transmitter 101.

Therefore, the influence of the transmitted wave does not affect the receiver, and the accuracy when detecting paper becomes substantially higher.

Note that U in the ceramic microphone (Fig. 4)
The main components of SO121 are P b T i03 t2 P bZros , P b (MgaNb a )03
The structure is a bimorph type vibrator, and the center frequency is 40 KHz.

FIG. 9 shows a circuit for correcting the reference level for comparison according to external conditions by the reference level setting means 21 in order to reliably discriminate the reception levels detected as shown in FIGS. 2 to 6.

To explain the operation, the electric signal from the ultrasonic wave 14 received by the receiver PET□ is amplified by the AC amplifier 17 with a gain of R4/R5 and input to the DC converter 19 via the capacitor C3.

The input signal is rectified by a diode D1 whose level is corrected by resistors R7 and R8, and a DC voltage is obtained at a terminal 29 by a capacitor C4.

When no slip sheet is detected, the signal from here is input to the comparator 27 and also to the memory 2 as reference level setting means.
1 and its impedance is converted by transistor Q2.

The converted signal charges capacitor C5 via reverse blocking diode D2.

Resistors R10, R, 2 form a discharge time constant of capacitor C5 to hold the charged charge, and serve as a setting device 25 that divides the voltage of capacitor C3 as a threshold voltage in comparator 27.

Based on the signal from the capacitor C5, the operational amplifier Q3 determines the reception level input from the terminal 29 and determines whether the input is ○.
When the voltage is lower than the input, that is, when there is no detection, an output signal of -vCC is generated, and on the other hand, when it is higher, that is, when paper is detected, an output signal of
It generates an output signal of Vcc to notify that paper has been detected.

Therefore, the capacitor C5 stores the peak of the reception level in the reference state when paper is not detected, and re-memorizes the stored level as the reception level increases, so that the reception level that decreased when paper was detected will be the same. Even if the voltage increases, the comparator 27 will not malfunction and the detection accuracy will not be impaired.

In this case, if the values of the dividing resistors R11 and R12 are set in consideration of the time required for the paper to pass through the receiver and the time requirement that the reception level fluctuates due to factors other than the paper, a more accurate detection function can be obtained.

Details regarding this point are described in Japanese Patent Application No. 49219/1972.

FIG. 10 is an example of a reference level storage device that can remove the limit of the detection function related to capacitor C5, and stores the reference received signal based on the storage command signal 23 immediately before paper is detected or when the reference state is detected. This can prevent the memory value from decreasing.

That is, switching element Q502 + resistors R502 to R5
04 constitutes a switching element, and a positive pulse as a command signal from a terminal 35 causes the element Q to be switched.

As the gate bias of No. 2 changes from negative to zero or positive, the resistance between the drain and source changes from a high resistance state to a low resistance state.

At that time, the voltage at the terminal 29 is set as a reference value, and the capacitor C501 is connected via the emitter-follower connected transistor Q501.
is memorized.

Here, if the previous stored value is higher than the current reference value, the difference is released through transistor Q501.

Also, since the high resistance R505 and the transistor Q503 t Q5゜4 forming a complementary emitter follower are connected to the capacitor C501, the capacitor C3
The charge of o1 is hardly discharged through the voltage dividing resistor R5o8°R6°9.

Therefore, until the next positive pulse is input, capacitor C5
01 holds the charge, that is, continues to store the reference value.

Note that the diode D501 corrects each voltage drop between the base and emitter in the transistors Q5ol2, Q5o3, and Q5°4 that constitute the emitter follower.

Therefore, a voltage of approximately the same level as the level input as the reference value is applied to the voltage dividing resistor.

FIG. 11 is a schematic diagram for conveniently obtaining the pulses in a copying machine.

Generally, means J for detecting paper P is provided near the end of the paper movement path in order to confirm discharge of the transferred paper.

The time it takes for the paper P to be normally conveyed by the conveyor belt N and reach the detection means J after being fed by the paper feed roller (2) is generally constant.

That is, the time when the detection means detects the paper P can be fully predicted.

Therefore, by using a timer that starts a timed operation in synchronization with paper feeding and ends immediately before copying paper is detected, the pulse generated at the end of the timed period can be used as the above command signal, and the correction of the above reference level can be applied to the copying paper. Can be done just before detection.

Also, by reciprocating the original table R or the light source, the original
When scanning optically, the paper feeding timing is synchronized with the above movement, so either the timer is activated by the cam switch E that operates according to the movement, or the fed copy paper is ejected during the above reciprocating movement. In this case, the pulse as the command signal can be obtained by a cam switch (not shown) which is activated immediately before discharge.

Similarly, when the rotation of the photosensitive drum B on which the electrostatic latent image is formed is synchronized with the paper feeding timing, the above pulse is obtained by the cam switch D.

The cam switches D, F, and G are used for drum home, paper feed,
Corresponds to the copy paper ejection timing.

Note that X is a developing device, W is a fixing device, and U is a charging device.

As described above, the present invention prevents the influence of reflected waves and wraparound sound waves on received signals when detecting objects using ultrasonic waves, and also corrects the reference level of the detection circuit according to the reception level in the reference state. The present invention provides an ultrasonic object detection device with extremely high accuracy.

In this manner, the present invention provides timing 23 related to the copying operation.
Since the received signal is taken into the storage circuit 21 and the receiver is provided with a screen, reliability in detecting transfer paper can be increased in a transfer type copying machine that has many requirements for reducing reliability.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a conventional copying machine that performs paper detection;
Figures 5, 6, and 7.8 are schematic cross-sectional views of the object detection device of the present invention used for paper detection, Figure 3 is a schematic diagram of the slit of the object detection device of the present invention, and Figure 4 is a plan view of the ultrasonic transmitter/receiver. 9 and 10 are examples of the drive circuit of the object detection device according to the present invention, and FIG. 11 is a schematic diagram of a copying machine to which the present invention is applied. In the figure, 101 is a transmitter, 102 is a slit, 103, 109, 110
is a receiver, 107 is a cone, 108 is a guide member, 105
is paper.

Claims (1)

[Claims] 1. In a transfer type copying machine having an oscillating element and a receiving element that receives an ultrasonic signal from the oscillating element, a screen is provided thereon, and the oscillating element and the receiving element are arranged opposite to each other via a transfer path of transfer paper. Object detection characterized in that the signal from the receiving element is taken into a storage circuit as a reference value in accordance with a timing signal of a predetermined time, and the transfer paper is detected based on this reference value and the signal from the receiving element. Device.