JPS604099B2 - Transfer paper detection device in copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detection device in a copying machine, and more particularly to a transfer paper detection device that always stably detects a transfer paper in a copying machine.

Using a transmitter-receiver (hereinafter referred to as a transceiver) that uses a signal medium that propagates in space such as electromagnetic waves (including light waves) and sound waves, the received signal, especially the reception gain, is In a detection device that detects the condition of a subject by detecting the influence of the object, the gain generally varies depending on the atmosphere of the space, such as temperature and humidity, or the presence of special gases, and also due to variations in the efficiency of each transmitter/receiver, the arrangement, and the detection device. It has unstable elements that fluctuate due to differences in the built-in state, changes in operating hours, etc.

These fluctuations occur completely unrelated to physical conditions such as the presence and position of the subject, and are therefore a major obstacle when using this type of apparatus.

Conventionally, methods to solve this problem include using a detection device equipped with a transceiver that is not easily affected by the above-mentioned fluctuation factors, or
Measures have been taken to adjust the gain of the transceiver each time it is used or to use it only under limited conditions, but these methods have the drawbacks that the detection device becomes expensive and the conditions of use are limited. Furthermore, as an example of a specific transmitter/receiver, a device for correcting fluctuations by feeding back the receiving gain to the transmitter side is disclosed in Japanese Patent Laid-Open No. 48-58.
This is introduced in Publication No. 866, but since it uses a light source as a transmitter and corrects its brightness, it is not suitable for detecting transparent objects, and is limited to extremely narrow applications. The positional relationship also has the disadvantage that it is limited to a narrow position due to the feedback effect. The present invention eliminates these drawbacks, allows use in a wide range of areas without limiting factors other than the subject that cause unstable fluctuations, the type of subject, and the position of the subject and the transceiver, and provides an extremely stable system. An object of the present invention is to provide a detection device for a subject that detects the state of a subject.

Furthermore, the present invention can speed up the detection speed for determining only the presence or absence of a subject. In other words, the present invention is
In a transfer paper detection device in a copying machine that uses a transmitter and a receiver to detect a transfer paper based on a change in a signal received by the transfer paper, a memory that stores the reception signal of the receiver as a reference value for detecting the transfer paper. means (C501), timing signal input means (terminal 35) for inputting a timing signal at a predetermined time before the transfer paper is detected, and the storage of the received signal of the receiver when the transfer paper is not detected. timing control means (switching element 502) for controlling the storage timing of the storage means according to the timing signal so as to be stored in the storage means; and comparing the reference value stored in the storage means with the received signal of the receiver. A comparison means (comparator 2) outputs a transfer paper detection signal by
7) A transfer paper detection device for a copying machine is provided.

This prevents the reference value from being taken in at an inconvenient timing, and it is possible to store the reference value that has been passed through the detection operation without being affected by the transfer paper. Therefore, changes in the received signal due to the transfer paper can be reliably detected, and a transfer paper detection signal can always be obtained satisfactorily. The basic configuration of the present invention will be explained with reference to the block diagram of FIG. This means that the gain of the signals exchanged between these transmitters and receivers (hereinafter, gain will be taken as an example) is affected by the presence or absence of the object 13, its location, etc. A transmitter/receiver is placed at

This arrangement may be an arrangement in which the four transceivers are faced to each other and the subject is interposed to reduce the reception gain, or it may be an arrangement in which the signal from the transmitter is reflected by the subject and received to increase the gain. good. The received signal is amplified by amplifier 17. Further, if the signal cannot be obtained as a DC signal from the receiver itself, the DC converter 19 converts the signal into a DC level corresponding to the reception level. The above DC level V.
is input from the terminal 29 to the comparator 27 and the reference value setter 28. Here, the reference value setter is used to relatively correct the signal amount when the received amount due to signal transmission and reception fluctuates due to influences other than the subject. Furthermore, if necessary, a storage command signal generator 2
It consists of 3. The reference value storage device stores the state of the received signal affected by the subject as a reference, for example, when the subject is not present, or the signal state resulting from a specific positional relationship between the transmitter/receiver and the subject. The output V of the terminal 29 obtained at that time is stored as a reference value. If the receiving gain changes by either increasing or decreasing depending on the presence or absence of the object, the reference value memory stores the maximum or minimum value of each value and corrects it according to the influence other than the object. However, at that time V. The reference value is memorized by re-memorizing the reference value.

Note that the reference value should be maintained against a natural decrease in the stored reference value; however, the above decrease can also be prevented depending on the V at that time. Note: The recording operation is performed in a slower time than the time required for transient changes caused by the influence of the subject. Alternatively, as another storage method, a signal notifying that the received signal is in the reference state from another device rather than from the terminal 29 or a manual signal for re-storing, that is, a command for the storage operation, can be generated by a storage command signal generator as shown in the figure. It is also possible to store the reference signal V at the terminal 29 by appropriately supplying it to a reference value storage device as shown by the dotted line.

Next, based on the stored reference values, the reference values are input as V and M to the threshold value setter 25 in order to set a dark value which will be a comparison reference for detecting the object.

The dark value setter converts the input reference values V and M into appropriate values and inputs them to the comparator from the terminal 31 as a threshold value for the comparator.

This comparison threshold setting will be explained with reference to FIG.

Figure 2 shows an arrangement in which the object is present between opposing transmitters and receivers, thereby reducing the received signal such as the amount received by the receiver.
It is a level correlation diagram in an apparatus having a function of determining whether or not a subject is present.

Assume that the output when there is no subject is VH, and that the output decreases to VL due to the insertion of the subject, and the comparison bell or dark value serving as a reference for detecting the change is Vo. Here, V
The values H and VL take are based on 1) differences in initial gain due to variations in transmitter/receiver efficiency and mounting method, etc., and 2) relatively slow fluctuations in gain due to changes in space atmosphere and transmitter/receiver efficiency over time, etc. 3. This is a value that fluctuates due to something that also occurs suddenly. In the conventional method of detecting the dark value level while it is fixed, the variation due to the above item 1 can be set to the optimum state by adjusting the value of each Z for each device as needed before use. However, the function values VH and V caused by the causes of 2nd term and 3rd term
Relative fluctuations with respect to L occur during the detection operation and cannot be prevented. In Figure 2, the fluctuation due to the cause of the second term is △VH,, △
Let VL,2, and the difference between these lower limits be ΔVD, and those based on the third term be ΔVH2, ΔVL2, and ΔVo2, respectively. Here, the reason why the variation due to the second term is larger than the variation due to the third term is that rapid gain variation that occurs in a short period of time is also included in the slow gain variation. In conventional detection devices, the cutoff value V depends on influences other than the subject.

does not change, so the lower limit of △VH or the upper limit of △VL, which is changing due to the second term, is the function value Vo that is set in advance.
may be exceeded, resulting in complete loss of detection capability. On the other hand, in the method according to the present invention, the memorized reference value is re-memorized every time the subject becomes the reference state, or at an appropriate time while the subject is in the reference state. In accordance with this, the threshold value Vo also changes, and in the end, the two do not change relatively. Incidentally, the term "slow fluctuation" refers to a fluctuation occurring in a period longer than the period during which the reference value is re-stored by the aforementioned storage command signal generator. Therefore, those having the above signal generator are △VH2, △V
L2 is not corrected, but the figure shows that the variation due to the third term is relatively smaller than that due to the second term over a certain period of time.
The fault related to item 3 is not important because it is easy to judge the fluctuation and furthermore, it can be substantially corrected by continuously re-memorizing the reference value and performing the detection operation. Further, the optimization of the relational value Vo for the first term is done based on the highest value of the damping ratio VL/VH, and by setting Vo to VH fixedly in advance using the threshold value setter 25, the device can be used without any adjustment thereafter. It becomes possible. Furthermore, in the present invention, V. can be set near the lower limit of △VH2 by the threshold value setter 25, and in particular, when detecting the presence or absence of a subject, it immediately drops to a level that is determined to be in the VH to VL region, so the presence or absence can be detected extremely quickly. be. Furthermore, in the present invention, the instability caused by the fluctuation due to the above two terms can be corrected only on the receiving side, so it is possible to correct the instability caused by the fluctuation due to the above two terms. This also provides a significant advantage over a method in which the transmitter output is controlled by the amount of reception without any hindrance. Hereinafter, as a specific embodiment of the present invention, a paper detection device using ultrasonic waves as a signal medium will be described in more detail with reference to the circuit diagram of FIG.

In this case, the arrangement is such that the ultrasonic waves emitted from the transmitter are received by the receivers facing each other with a space between them, and the paper 0 enters the space, thereby reducing the amount of reception. Although the receiver section is omitted in FIG. 3, the signal transmitted by the receiver at about 40 KHz is received by the receiver 15. This receiver converts the incident ultrasonic wave into an alternating current electrical signal at the same frequency according to the received amount using a photoelectric conversion element PET, such as a crystal. Furthermore, the resistance R
, is the load resistance of the above element FET. This AC signal is amplified by 17 amplifiers. Reference numeral 17 designates an AC amplifier, and the input signal passes through a DC blocking capacitor C, and enters the base of a transistor Q, which is appropriately biased by o resistors R2 and R3.

The above Q, resistors R4 to R5, and capacitor C2 constitute a normal emitter negative feedback type transistor AC amplifier, and C2 is a bypass converter and is about the tortoise on the electric hoof side. The amplified signal here is input to the DC converter 19.

The signal passes through the DC blocking capacitor of capacitor C3, is half-wave rectified by diode D, and its peak value is held by 0 in the charge of capacitor C4, and is sent to terminal 2.
9 as a DC level signal. Here resistance R7
, R8 are for correcting the forward rising voltage of the diode D, and the resistor R9 is a discharge resistance of the capacitor C4. Therefore, the output signal of the amplifier 17 is reduced to a peak-to-peak voltage Vo
, 7, the DC voltage V at the terminal 29 is V,≠Vo,
It will be 7/2. The output from terminal 29 is input to comparator 27 and reference value storage 21 . At 21 the signal from terminal 29 is applied to the base of transistor Q2.

Transistor Q2 is used as a normal emitter follower and serves as an impedance converter that increases input impedance and lowers output impedance. The impedance-converted voltage signal passes through diode D2 and charges capacitor C5.

The reason for ○2 above is to prevent backflow so that the electricity charged in C5 will not be discharged through transistor Q2.
The voltage is the base-emitter voltage VB of transistor Q2.
It also serves to compensate for being shifted up by E. Therefore, assuming that the discharge time constant of C5 is sufficiently long, the highest voltage at terminal 29 will be held across capacitor C5. Resistance R,. ,R,2
First, it forms a discharge time constant as C5 x (R, .0R.2), and also serves to divide the voltage held by the capacitor C5 to an appropriate value as the dark value voltage in the comparator. This also corresponds to the function value setting device shown in FIG. 125. The divided voltage enters terminal 31, and comparator 27 eventually compares the output voltages at terminals 29 and 31. This comparator 27 uses an operational amplifier Q3 in an open loop with no feedback effect, and inputs the voltage at the terminal 29 as an e input.
By connecting the voltage of 1 to the input terminal, the input voltage becomes e
If the voltage is higher than the input, the output will be 10 Vcc, which is close to the operational amplifier power supply, and in the opposite case, it will be about 1 Vcc. The output divided by the resistors R, 3, R, 4 is sent to the detection terminal 33.
In addition to this, a lamp or the like will be activated to notify that paper has been detected. Note that since the input impedance of the operational amplifier input terminal is large, it hardly affects the time constants of the capacitors C4 and C5. If the transfer paper used in the copying machine passes between the ultrasonic transmitter and receiver, the gain will be at least 12 times lower than when the transfer paper is not used. Therefore, the level that has been reduced by the divider 25 from the terminal voltage of the capacitor etc. becomes the function value, and relatively, △VH, △VL, in FIG. 2 are corrected, and △VH2,
Even if each of ΔVL2 has a phantom B fluctuation with respect to VL and VH, a stable detection function is exhibited without malfunction. Incidentally, the slow fluctuation in the ultrasonic transmission/reception gain due to influences other than the subject is approximately 2> which is extremely large compared to the fluctuation of 1 phantom B due to the above paper, but the present invention sufficiently compensates for this. That's what I got. Further, in general, from the viewpoint of improving the start-up of the detection operation, it is preferable that the time constant C4×R9 is 4. However, the filter is appropriately set so as to absorb sudden changing elements such as noise that occur in a short time as a filter, and to reduce ripples in the DC current. Next, the discharge time constant of the capacitor C5 is set to be equal to or longer than the maximum time required for paper to pass in the case of paper binding detection in a copying machine. In other words, if the voltage across both ends decreases due to the discharge of the capacitor C5 and attenuates beyond a certain value, a detection error will occur. but,
If this time constant is too long, the storage operation will not be able to follow the decrease in the reference value when there is no paper, and there will be a limit to the detection effect under conditions where the reference value changes rapidly. Generally, it takes less than 0.01 seconds to start up the change depending on the presence or absence of paper such as transfer paper in a copying machine, and the paper passage time is about 19 sand, so in this example, C4×R9≠0.009 sand ,C5×(R,.10R
, 2) Extremely stable detection operation was obtained by using the main 9 Tochisa.

Further, the circuit according to the present invention is not limited to the example shown in FIG. 3, but may also be configured in a detection device using light from a pair of a lamp and a light receiving element as shown in FIG. 4, for example.

FIG. 4 11 shows a normal lamp lighting circuit, so 12, 14
becomes visible light.

The receiving circuit 15 is composed of a cadmium sulfide CdS side and a fixed resistor R side, and the amount of light from 14 is large unless it is blocked by the object 13, and since the resistance value on the CdS side decreases, the voltage level at the terminal 29 is large. . When the subject 13 is present in the optical path, a situation opposite to the above occurs. Hereinafter, the same detection function will be achieved using the circuit after the terminal 29 in FIG. Since the output of the converter 15 is at a DC level, the DC converter 19 is not necessary, but when using mid-oscillation modulation light, the circuit configuration shown in FIG. 3 is used.

Also, by using a transmitter/receiver with little variation in the reference value, the resistances R, . By increasing the division ratio of , R, 2, the threshold value can be set near the reference value of terminal 29 or, conversely, near the level passing the grade, thereby speeding up the detection rising operation when paper enters or is ejected. I can do it. Although the object of the present invention can be achieved by the standards shown in FIGS. 3 and 4, the criteria shown in FIGS. The value storage 21 will be explained below.

If the reference state level decreases or increases due to the influence of the subject, a simple reference value storage device using a capacitor as shown in FIG. 3 is constructed.

In particular, when detecting the presence or absence of paper by detecting the reflection of a signal by paper, the state where there is no paper is set as the reference state or the third
When detecting the transmission gain as shown in the figure, if the state where paper is present is set as the reference state, the minimum value of the received amount Z is stored as the reference value. In this case, from the terminal 29 to the reference value memory 21
The maximum value may be stored by inverting the input to the circuit as shown in FIG. 3, or the minimum value may be stored using a configuration with a current flow completely opposite to that shown in FIG. 3, as shown in FIG. Z is possible. In either case, the stored value changes or evaporates due to discharge as described above over time. In FIG. 5, a switching element is provided on the input side of a storage capacitor C5o, and a storage command in the form of a positive pulse is given from the storage command 2 signal generator 23 in FIG. It has a memory function.

This allows you to detect the object without constantly memorizing the maximum or minimum value as the reference value in the reference state as in the example above.
The purpose of this method is to memorize the reference value by memorizing the signal just before the reference value is reached, by using another device to detect and memorize the reference state, or by manually performing the judgment operation through observation, thereby preventing memory loss. be. In FIG. 5, the switching element Qo2 and the resistors R 2 to 3R and 4 are not switching elements, and the gate bias of the element Q5.2 changes from negative to zero or positive due to the positive pulse from the terminal 35, and the gate bias between the drain and source changes. The resistance changes from a high resistance state to a low resistance state.

The value at the terminal 29 at that time is stored as a reference value in the capacitor C5 via the transistor Q of the emitter-follower connection 3. Here, if the previous stored value is higher than the current reference value, the difference is released through the transistor Q5o. In other words, since the input impedance of the transistor Q law 3 is high and the length of the resistor R is large, the operation is different from that shown in FIG. 3. Therefore, since re-memory is performed by an external command, the transistors Q5.3, Q5.

Through the complementary emitter follower of C5o, approximately the same voltage as the terminal of C5 is applied to resistor R5.

6, R5.

9, the example of FIG. 5 obtains an extremely large discharge time constant.

Furthermore, when the level of the reference value is the maximum or minimum value as in the setting in the example shown in Figure 3, defects due to the volatility of the memory device can be eliminated by a method such as the circuit example shown in Figure 6. I can do it.

In FIG. 6, the transistor Q6o, the diode D6, the capacitor C, the resistor R6, and the comparator 27 in the reference value memory 21 operate in exactly the same way as in the example of FIG. When the subject is inserted between the opposing transceivers and the electrode shown in Figure 29 is lowered, the potential at the output terminal 37 of Q6.4 increases.

Therefore, the base electrode of transistor Qo2, which had been lowered through resistance R and diode D fence 3, is now connected to diode ○6.
As the transistor Qo2 becomes non-conductive, the transistor Qo2, which had been properly conductive, becomes non-conductive. Operational amplifier Q6 when the above Q6.2 is applied.

Since the source input terminal of 3 and the e input terminal had almost the same electrode and were at zero potential, the output was also at zero potential, so the diode D
6.

2 became non-conductive, and amplifier Qo3 had no effect on C.

However, because the transistor Q6.2 becomes non-conductive at one end, the transistor Q6.2 becomes non-conductive.

The voltage at terminal 29 is connected to resistor R6.

5, R6.

Only the portion divided by 6 is input.

Therefore, the output at this time is (6 of R/R6 of the voltage at terminal 29)
o50R6.6) × The electric potential of the fin becomes diode D6
.

2. 0 is applied to the capacitor C6o terminal through side R602.

However, diode D fence, resistor R6, . is diode D6
This was inserted to correct the voltage drop between the anode and cathode of o2, and the diode D6.3 is the transistor Q6.

This is to prevent excessive reverse voltage from being applied between the two base emitters.

In this way, the potential of terminal 29 decreases and capacitor C
When the arc starts discharging, a constant voltage proportional to the voltage at the terminal 29 is applied to the terminal C, so that the voltage at the terminal C does not drop below that level.

Therefore, by appropriately setting this level, it is possible to perform the detection function without malfunctioning even if the sensor does not return to the reference state for a long time. At this time, when the reference state is restored again, the output voltage of the instantaneous amplifier Q6.3 rises as the voltage at terminal 29 rises. The voltage at the terminal 29 does not suddenly rise above the voltage at the terminal 29.

Meanwhile, the output of operational amplifier Q6.4 naturally falls to a low level and the output of transistor Q6.

Operational amplifier Q6 because 2 is conductive.

The output of C6o is again reduced to zero potential and has no effect on the potential of C6o.

An example of the memory hold method in FIG.
6.

Of course, the method example shown in FIG. 7, which does not use 3, can also be used.

In the case of FIG. 7, the potential of the terminal 29 is set by resistors R7o, R7.
2, and this division ratio is R7.

2-R70, 10R702-R formulas can be considered in exactly the same way as the example in Figure 6 from Nada.

However, in this case, the output of terminal 29' must be connected to the e terminal of the comparator. As described above, the circuit of the present invention can correct initial gain variations or gradual gain changes in this type of device without making adjustments. Of course, the changes and corrections for variations are not infinite.

So, what factors are limiting? First, when the receiver input level becomes high, there is saturation related to the power supply voltage +Vcc, -Vcc of each active element, and this saturation limits the high level of the input. . In order to deal with this problem, there is only a simple method of selecting a high power supply voltage, each high-voltage element, and a simple method of appropriately attenuating the input signal at the beginning.
On the other hand, the limiting factor for the low level of the input is an error due to a voltage level shift of each active element, such as the base-emitter drop voltage VBE in the emitter follower and the forward rising voltage V^K in the diode. For example, in the circuit example shown in FIG. 3, when the input signal becomes very small, these errors occur because
The output of terminal 29, that is, the voltage value of terminal 29, is no longer completely proportional to the error caused by the forward rising voltage of diode D, and the maximum voltage at terminal 29 and the voltage value of capacitor C5 of reference value memory 21 are not completely proportional to each other. Transistor Q2 also for voltage
A voltage shift occurs due to the emitter follower type amplifier. Simple correction methods for these errors have been mentioned in each of the circuit examples cited so far. For example, in the above two examples, the bias circuit includes resistors R7 and R8, and the voltage correction uses diode D2, respectively. However, none of these methods are perfect. Now, in order to further correct the error caused by the rectifier diode D in the DC converter 13 in FIG. 3, the example shown in FIG. 9 can also be considered. In 19 circuits corresponding to amplifiers, the output from the receiver is connected to the output terminal of the operational amplifier through a DC blocking capacitor C. This operational amplifier Q9. , it is necessary to select one with a small input offset voltage, but the resistor R9.2 has a large value that does not affect the input signal from the terminal 16, and the anode voltage of the diode D9o is set to the DC bias voltage of the terminal 16. In addition, by making the bias voltage of the e terminal of the amplifier Q9 the same using the resistor R, the DC level of the output is equal to that of the input, that is, the diode D
It can be made equal to the anode voltage of 9o.

The amplifier Q9o amplifies the AC input voltage signal from the terminal 16 by a factor of four using the negative feedback resistor R. This amplified AC signal can be biased at the output end by the anode voltage of the diode D, ie, the forward rising voltage of the diode, as described above. Therefore, if the forward rising voltages of the rectifier diode D2 and the diode D9o in the DC converter 19 are equal, then the voltage between the peak values of the input voltage from the input terminal 16 is the voltage at the terminal 29.
The DC voltage V, at is V,=vinXSagi÷2, and can be made proportional to the complete war Vin'. In addition, in order to equalize the rising voltage of the diodes, the diodes D9o, ,D
9 is the same in terms of temperature and daily direction characteristics, and furthermore, the forward bias rectification of the D Yanagi according to the rectification current of the diode D law 2 by the female capacitor C9 and the resistor R9 is appropriately performed by the resistor R Yanagi. This can be done by setting it to . By using the amplifier 17 and DC converter 19 shown in FIG. 9 and the reference value storage 21 shown in FIG. The correction range is approximately 54B, which corresponds to the peak-to-peak input voltage Vinp-p of the input terminal 16, from approximately 3V to 1.5V, and it is clear that it is effective even for extremely large fluctuations. It became. As described above, the present invention
It can be used without any adjustment due to influences other than the subject, and can quickly detect the condition of the subject, and can be used in an extremely wide range of applications regardless of the position of the transmitter/receiver, the type of subject, or the atmosphere of the space.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention.
Transmitter, 12: Transmission signal, 13; Subject, 14; Reception signal, 15; Receiver, 17: Amplifier, 19; DC converter,
21: Reference value storage device, 23; Storage command signal generator, 25
: threshold value setter, 28; reference value setter. Figure 2 is a level correlation diagram showing the level fluctuation of the received signal.
FIG. 3 is an embodiment based on the present invention, FIG. 4 is an example of a transceiver based on the present invention, and FIGS. 5, 6, 7, and 8 are embodiments of a reference value storage device based on the present invention. , FIG. 9 is an example of an amplifier and a DC converter according to the present invention. Hair-Picture Pig Z Picture Younger brother 3 Picture Many 4 Picture Many 5 Picture Tsutomu 7 Picture 8 Younger brother? figure

Claims (1)

[Claims] 1. In a transfer paper detection device in a copying machine that uses a transmitter and a receiver to detect a transfer paper based on a change in a signal received by the transfer paper, the reception signal of the receiver is stored as a reference value for detecting the transfer paper. storage means; timing signal input means for inputting a timing signal at a predetermined time before the transfer paper is detected; a timing control means for controlling the storage timing of the storage means in accordance with a timing signal; and a comparison for outputting a transfer paper detection signal by comparing the reference value stored in the storage means with the received signal of the receiver. 1. A transfer paper detection device in a copying machine, comprising: means.