JPS62146632A - Ink volume detection circuit - Google Patents

Abstract

PURPOSE:To provide a circuit which can dispense with circuit packaging restrictions and erroneous detection due to the adverse effect of a floating volume by enabling a monostable circuit to change the pulse width of an output signal in accordance with a static capacity detected by an electrode, and also a phase comparison means to compare the phases of an output signal of the monostable circuit with a reference signal. CONSTITUTION:A prearranged amount of ink 4 is contained in an ink container 6 and when an electrode 3 contacts the ink 4, the static capacity C4 by the high dielectric constant of the ink 4 is detected by the electrode 3 and then the detected data is given to a capacitor input terminal C. A nonstable multivibrator circuit 8 generates a corresponding pulse signal, which is in turn, input to the trigger terminal of a monostable multivibrator circuit 7, outputting a corresponding pulse signal. A flipflop 9 reads an output signal from the monostable multivibrator circuit 7 and thereby compares the phases of output signals from the nonstable multivibrator circuit 8 and monostable multivibrator circuit 7. If a prearranged amount of ink is available, the output signal comes to high level. In addition, when the ink 4 has been consumed and consequently an electrode 3 does not touch the ink 4 at time t1, the output signal of the flipflop 9 comes to low level.

Description

[Detailed description of the invention] (Technical field) The present invention relates to an ink amount detection circuit for a printing press.

(Prior art) The ink amount detection circuit includes a pair of capacitor electrodes, at least one of which is connected to a detection electrode provided facing the printing ink in the ink reservoir, and changes in capacitance between the pair of capacitor electrodes. An oscillation circuit whose oscillation frequency changes according to the oscillation frequency, a receiver circuit which receives the output signal of this oscillation circuit and tunes to it at a set frequency, and a circuit which converts the output signal of this receiver circuit into a DC voltage and compares it with a reference voltage. A method having the following is known from Japanese Patent Application Laid-Open No. 58-62520.

However, in this ink amount detection circuit, the receiving circuit is tuned to the output of the oscillation circuit at a set frequency, so the oscillation frequency generally used for the oscillation circuit is several MIIZ to 100 MH2.
In this high frequency range, implementation that suppresses the effects of stray capacitance of the five circuits is required. The relationship between the amount of ink, the oscillation frequency of the oscillation circuit, and the tuning strength of the receiving circuit is shown in Figure 3. The frequency becomes lower than the set tuning frequency of the receiving circuit, resulting in a false detection that there is no ink.

(Objective) It is an object of the present invention to provide an ink amount detection circuit that can improve the above-mentioned drawbacks and eliminate restrictions on circuit implementation and false detection due to the influence of stray capacitance.

(Structure) The present invention has an electrode that detects a capacitance corresponding to the amount of ink, a reference signal generation circuit, a monostable circuit, and a phase comparison means, and the monostable circuit detects the reference signal generated by the reference signal generation circuit. Starts in response to. In this monostable circuit, the pulse width of the output signal changes depending on the capacitance detected by the electrode, and the one-phase comparison means compares the phases of the reference signal and the output signal of the monostable circuit.

FIG. 1 shows an embodiment of the invention. In the figure, 1 is an ink amount detection section, 2 is a detection circuit section, 3 is an electrode that detects a capacitance C4 corresponding to the ink amount, 4 is ink of the object to be detected, 5
is an ink feed roller, 6 is a grounded conductive ink container, 7 is a monostable multivibrator circuit, 8 is a reference signal generation circuit consisting of an astable multivibrator circuit, 9 is a flip-flop for phase comparison, 10 is an output terminal, 11.1
2 is a conductor. In a printing press, the ink in the ink reservoir formed by the ink container 6 and the ink feed roller 5 is fed by the ink feed roller 5, and the amount changes. Electrostatic capacitance C4 due to the ink between the ink container 6 and the ink container 6 is detected by the electrode 3. Note that an electrode may be provided separately from the ink container 6, and a capacitance corresponding to a predetermined amount of ink may be detected between this electrode and the electrode 3. The voltage vi3 is placed above the ink container 6, and the ink 4 is interposed between the ink container 6 and the ink container 6.

The capacitance CA of the capacitor that constitutes the element that determines the oscillation time constant of the astable multivibrator circuit 8 is CA=C
Therefore, the astable multivibrator circuit 8 always generates a pulse signal having a pulse interval corresponding to its capacitance CA. Here, C is the capacitance of the capacitor mounted in the detection circuit section 2, C1 is the capacitance of the capacitor mounted between the conductor 11 and the ink container 6 in the ink amount detection section 1, and C5 is the capacitance of the capacitor mounted in the conductor 11. and the stray capacitance of its connected parts. The monostable multivibrator circuit 7 is triggered by the fall (or rise) of the output pulse signal of the astable multivibrator circuit 8 to generate a pulse.

The astable multivibrator circuit 8 may be another oscillation circuit that generates pulses repeatedly, and the monostable multivibrator 7 is triggered by a different pulse signal at the falling edge of the pulse signal of the astable multivibrator circuit 8. It's okay. The capacitance CB of the capacitor that constitutes the element that determines the oscillation frequency of the monostable multivibrator circuit 7 is CB=C, +C4+C, and the monostable multivibrator circuit 7' has a pulse width corresponding to this capacitance CB. Outputs a pulse signal.

Here, C2 is the capacitance of the capacitor mounted in the detection circuit section 2, and C4 is the capacitance of the electrode 3. The capacitance C6 of the capacitor formed by the ink container 6 and the ink interposed therebetween is the stray capacitance of the conductor 12 and its connected parts. In the flip-flop 9, the output pulse signal of the monostable multivibrator circuit 7 is inputted to the data terminal, and the output pulse signal of the astable multivibrator circuit 8 is inputted to the clock terminal, and binarization is performed depending on the presence or absence of a predetermined amount of ink. Output a signal.

Next, the operation of this embodiment will be explained.

First, the ink container 6 contains a predetermined amount of ink 4, and the electrode 3
When is in contact with the ink 4, the capacitance C4 due to the high dielectric constant of the ink 4 is detected by the electrode 3 and applied via the conductor 12 to the capacitor input terminal C which determines the time constant of the monostable multivibrator circuit 7. The capacitance CB to this capacitor input terminal C is CB=C2+C4+C. In addition, the capacitor input terminal C that determines the time constant of the astable multivibrator circuit 8 is supplied with the capacitance C3 of a capacitor mounted in the ink amount detection section 1 via a conductor 11, and the capacitor input terminal C is connected to the capacitor input terminal C. The total capacitance CA is CA=C +C, +C.

As shown in FIG. 2 (1), the astable multivibrator circuit 8 generates a pulse signal with a pulse interval T0 corresponding to its capacitance CA, and this pulse signal is applied to one trigger terminal of the monostable multivibrator circuit 7. is input. The monostable multivibrator circuit 7 is triggered by the fall of the pulse signal input to the trigger terminal, and outputs a pulse signal with a pulse width T corresponding to the capacitance CB as shown in FIG. 2 (2). . The flip-flop 9 converts into an astable multivibrator by reading the output signal of the monostable multivibrator circuit 7 inputted to the data terminal at the rising edge (or falling edge) of the pulse signal inputted to the clock terminal from the astable multivibrator circuit 8. The phases of the output signals of the circuit 8 and the monostable multivibrator circuit 7 are compared, and when there is a predetermined amount of ink, the output signal of the flip-flop 9 becomes T>TI, as shown in FIG. 2 (3). Become a high level.

Furthermore, when the ink 4 in the ink container 6 is consumed and the electrode 4 no longer contacts the ink 4 at time t1, air enters between the electrode 4 and the ink container 6, and the capacitance C4 due to the ink 4 increases. 4, the monostable multivibrator circuit 7 outputs a pulse signal with a pulse width T2, with the capacitance CB to the capacitor input terminal becoming CB=C, +Cr.

Therefore, when the predetermined amount of ink is used up (when ink 4 is less than the predetermined amount), T2 becomes To, and as shown in Figure 2 (
As shown in 3), the output signal of the flip-flop 9 becomes low level.

This embodiment shows the capacitance CA to the capacitor input terminal C of the astable multivibrator circuit 8 and the capacitance CB when detecting ink to the capacitor input terminal C of the monostable multivibrator circuit 7 with the electrode 4. , and the capacitance CB when ink is not detected by the electrode 4, CB,'
By establishing the relationship >CA>CB2, ink amount detection becomes possible with a simple circuit configuration. Furthermore, the conductor 11
．． By taking measures such as twisting 12 to make C, Gin C, this detection method based on phase comparison can sufficiently compensate for fluctuations in stray capacitance, and is not subject to restrictions on circuit implementation, resulting in stable detection. became possible.

(Effects) As described above, according to the present invention, a monostable circuit in which the pulse width of the output signal changes depending on the capacitance corresponding to the amount of ink detected by the electrode is started in response to the reference signal, and the monostable circuit is activated in response to the reference signal. Since the phase is compared with the output signal of the monostable circuit,
It is possible to eliminate restrictions on circuit implementation due to the influence of stray capacitance, and it is also possible to eliminate false detections.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart of the same embodiment, and FIG. 3 is a characteristic curve diagram of a conventional circuit. 3... Electrode, 7... Monostable circuit, 8... Reference signal generation circuit, 9... Phase comparison means. Figure 1 λm

Claims (1)

[Claims] A reference signal generation circuit that generates a reference signal, an electrode that detects capacitance corresponding to the amount of ink, and a pulse width of the output signal that starts in response to the reference signal and changes depending on the capacitance detected by the electrode. An ink amount detection circuit comprising: a monostable circuit that performs a phase comparison; and a phase comparison means that performs a phase comparison between an output signal of the monostable circuit and the reference signal.