JPH0357519Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a solenoid that drives the writing block of a writing head in an automatic writing device such as an automatic drafting machine or an X-Y plotter in an up and down direction perpendicular to the writing surface. The present invention relates to a solenoid control circuit for a writing head for controlling a plunger, and more particularly to a solenoid control circuit for a writing head that can reduce the impact when the tip of the writing part comes into contact with a writing surface.

[Background technology and its problems]

Generally, in automatic writing devices such as automatic drafting machines, automatic drafting machines, X-Y plotters, and - While performing the down motion, the writing operation is performed by relatively moving the writing means on the writing surface in two-dimensional directions, for example, X and Y. That is, the pen is moved to the writing start position in the pen-up state, the tip of the pen is brought into contact with the writing surface by the pen-down operation, the pen is moved along the desired trajectory to be written, and the pen-up operation is performed at the writing end position. By repeating a series of operations in which the tip of the pen is raised and separated from the writing surface, a desired symbol, figure, etc. is drawn on the writing surface.

Incidentally, the up/down operation of the writing means such as a pen is generally performed by a solenoid plunger, and the writing means such as a pen is made to move down or up in response to energization or interruption of solenoid current. In this case, it is preferable to establish a correspondence relationship in which the pen-down operation is performed when the solenoid is energized, since the pen-up state is maintained when the power is turned off.

By the way, when the pen moves up and down, especially when moving down, the tip of the pen collides with the writing surface, which can cause negative effects such as impact noise, shortened pen life, and damage to the paper that serves as the writing surface. Particularly when writing a lot of numbers, alphanumeric characters, kanji, etc., or when the writing speed is high, the number of times the pen goes up and down per unit time is high, and the tip of the pen during the down movement described above may become damaged. Impact generation has become a major problem.

In particular, in the case of a writing head that uses a pencil lead as a writing means, there is a risk that the lead will break due to the impact when the pen is down, and some kind of impact mitigation measures are required.

[Purpose of invention]

In view of these conventional circumstances, the present invention prevents damage to the writing means such as a pen by alleviating the impact at the tip of the writing means during the so-called pen-down operation in which the writing means such as a pen comes into contact with the writing surface. It is an object of the present invention to provide a solenoid control circuit for a writing head which can prevent shortening of the life of the writing head, prevent damage to the paper used as the writing surface, and further reduce impact noise.

[Summary of the idea]

In other words, the feature of the solenoid control circuit for a writing head according to the present invention is that the writing means such as a pen placed in the writing head of an automatic writing device such as an In a writing head solenoid control circuit for controlling a solenoid plunger driven in a direction,
a down operation signal generation circuit that generates a down operation pulse signal for moving the writing means in the downward direction and bringing the tip of the writing means into contact with the writing surface; an integrating circuit that integrates the down operation pulse signal; A level addition circuit adds a constant DC level to the integrated output from this integration circuit to improve the rise characteristics at the start of driving within the down operation pulse signal output period, and the output from this level addition circuit is pulse width modulated. and a pulse width modulation circuit that outputs a pulse signal whose pulse width gradually becomes wider as time passes, and the solenoid plunger is driven and controlled by the output from the pulse width modulation circuit.

[Embodiment] Hereinafter, a solenoid control circuit for a writing head according to the present invention will be described with reference to the drawings.

FIG. 1 is a block circuit showing an embodiment of the present invention. In this FIG. 1, input terminal 1 has
For example, a signal for controlling the vertical movement of the writing means as shown in FIG. 2A, a so-called pen up/down signal, is supplied. The pen up/down signals in FIG. 2A are switched from pen up UP to pen down DN at time _t1 , and switched from pen down DN to pen up signal UP at time _t3 . This pen up/down signal A is sent to the pen down operation signal generating circuit 2. This pen-down operation signal generating circuit 2 is constituted by, for example, a mono-multi circuit, and is triggered by the rise of the pen-up/down signal A, and as shown in FIG. 2B, from time _t1 to time _t2 . A pen-down operation pulse signal having a constant pulse width T is output. During this time T, the solenoid plunger is driven, for example, by suction, and shifts from the pen-up state to the pen-down state. The pen-down operation pulse signal B is
The integrated output C is sent to the integrating circuit 3, and the level increases with a substantially constant slope from time _t1 to _t2 , as shown in FIG. sent to. Level addition circuit 4
is a constant DC level L _DC time at the above integral output C
It is added only from t ₁ to t ₂ , and the simplest way is to add the level of the pulse signal B from the pen-down operation signal generation circuit 2 to the integral output C, but in addition, the broken line in FIG. As shown in
The level of the output from the DC voltage generating means 5 which generates the desired DC level L _DC based on the pulse signal B may be added to the integrated output C. The output from the level addition circuit 4 is as shown in FIG. 2D, and is sent to the pulse width modulation circuit 7 via the addition circuit 6.

The level is added to the DC level L _DC integrated output during this pen down drive (between times t ₁ and t ₂ ).
This is to allow a certain amount of drive current to flow when the solenoid starts energizing, thereby allowing the output shaft to smoothly transition from a stationary state to a moving state.If the integral output is used, the start-up at the start of driving will be poor and the output shaft will not move until the pen-down state is reached. This takes into consideration the fact that it takes time.

By the way, between the above-mentioned times _t1 and _t2 , for example, the solenoid plunger is driven by suction to cause the pen to move downward (pen-down operation), but after the pen has descended, the solenoid plunger is held by suction and the pen is moved down. must be kept down. This solenoid is held from time t ₂
The connection is performed until t ₃ , and during this time it is required to continue supplying a weaker holding current to the solenoid than during suction driving.

The adder circuit 6 is for adding this solenoid holding output, and the output for solenoid suction drive from the level adder circuit 4 (see Fig. 2D).
reference. ) and the output from the solenoid holding output generation circuit 8 (see FIG. 2E) are added to form the output signal shown in FIG. 2F, which is sent to the pulse width modulation circuit 7.

The solenoid holding output generation circuit 8 is set at the falling edge (time t 2 ) of the pen-down operation pulse signal (FIG. _2B ), and is set at the falling edge (time t ₃ ) of the pen-up/down signal (FIG. 2 A). It may be constructed of a flip-flop that is reset by the flip-flop, and a voltage generator that generates an output of the level L _HLD necessary to hold the solenoid based on the output of this flip-flop.

Next, the pulse width modulation circuit 7 outputs a pulse having a pulse width corresponding to the level of the input signal, and may have a configuration as shown in FIG. 3, for example. 3, a triangular wave as shown in FIG. 4a from the triangular wave generator 12 is supplied to one input terminal (inverting input terminal) of the differential amplifier or comparator 11, and the other input terminal An input signal to be pulse width modulated may be supplied to the (non-inverting input terminal) 13. In this FIG. 3, the level of the input signal supplied to the input terminal 13 is as shown in FIG.
When the level L _b is, a pulse output with _a pulse width T _b as shown in FIG. _4b is obtained from the output terminal 14. A pulse output with a wide pulse width T _C as shown in Figure 4c can be obtained. That is,
As the input signal level rises, the output pulse width becomes wider, and as the input signal level falls, the output pulse width becomes narrower.

Therefore, from time t ₁ to t ₂ of the input signal supplied to the pulse width modulation circuit 7 (FIG. 2 F), the pulse width becomes a pulse output whose pulse width increases with time, and from time t ₂ to t ₃ Up to this point, a pulse output with a constant narrow pulse width can be obtained (second
(See Figure G). This solenoid driving pulse signal G
is taken out from an output terminal 10 via a drive circuit 9 and supplied to a solenoid coil of a solenoid plunger for pen up/down.

Note that the addition circuit 6 and the pulse width modulation circuit 7 in the configuration shown in FIG. 1 may be replaced to form a configuration as shown in FIG. 5. In the configuration shown in Fig. 5,
Only the pen-down drive signal (D in Figure 2) from the level addition circuit 4 is sent to the pulse width modulation circuit 7 for pulse width modulation, and this pulse width modulation output is sent to the addition circuit 6 to generate a solenoid holding output. Since it is added to the solenoid holding output from circuit 8 (FIG. 2E), a solenoid drive signal as shown in FIG. 2H is sent from addition circuit 6 to the solenoid coil via drive circuit 9. The holding current in this case (from time t ₂ to t ₃ in FIG. 2H) is a steady DC current, and since the current value is small, problems such as heat generation do not occur.

Then, at time _t3 , when the mode is switched to the pen-up mode as shown in FIG. 2A, for example, a flip-flop in the solenoid holding output generation circuit 8 is reset, and the holding current changes as shown in FIG. 2G or H. By being cut off, the suction holding force of the solenoid plunger, for example, is released, and the pen-up state is entered by the return force of a return spring or the like.

FIG. 6 shows the relationship between the moving distance (stroke) and the moving speed of the pen when the solenoid plunger for pen up/down is driven and controlled by the solenoid control circuit as described above. The solid line in FIG. 6 shows the solenoid drive characteristics of the circuit according to the above embodiment of the present invention. Compared to the conventional example (broken line in FIG. 6), when the pen reaches the pen-down position, the pen moves at a lower speed and the impact is smaller. I know what will happen.

Here, when driving the pen down (time t ₁ in FIG. 2,
The driving current during the period t ₂ ) is the output obtained by adding a constant DC level L _DC to the output of the integrating circuit 3 (Fig. 2 C) (Fig. 2 D), which is pulse width modulated. However, this takes into consideration the following points. That is, first, by using a pulse current, it is possible to suppress heat generation when the solenoid is driven. Next, the slope component of the integral output whose level increases over time cancels out the increase in return force caused by, for example, compressing the return spring due to suction operation, and also completely suctions the output shaft of the solenoid plunger. Immediately before the pen down drive ends (time t ₂
(just before) to ensure pen-down operation. Furthermore, at the start of pen-down drive (immediately after time t ₁ ), a current with a certain pulse width corresponding to the DC level L _DC is passed, so that the solenoid output shaft at the start of drive transitions from a stationary state to a moving state. The required energy is sufficiently supplied to improve the so-called start-up characteristics of the operation, thereby shortening the time from the start of pen-down drive until reaching the pen-down state. While satisfying each of these points, the moving speed of the pen is kept low when the pen reaches the pen-down state, thereby alleviating the impact.

Such a solenoid control circuit that alleviates the impact of the pen tip when the pen is down is extremely desirable, especially when applied to a writing head that uses a pencil lead as a writing means, and prevents the lead from breaking due to the impact when the pen is down. This can be prevented and smooth writing operations can be achieved.

Note that the present invention is not limited to the above-mentioned embodiment, and for example, the solenoid holding output generation circuit 8 may be configured to detect the peak of the output level (D in FIG. 2) of the level addition circuit 4, and detect this peak. A configuration may be adopted in which an output for holding the solenoid is generated from the time of detection (time t ₂ ). Furthermore, in the above embodiment, an example using a suction drive type solenoid plunger was explained, but a protrusion drive type solenoid whose output shaft protrudes when driven with current may also be used. In this case, If the pen-down operation is performed by the output shaft protruding, the protruding state is maintained by the solenoid holding current, and when the holding current is cut off, the output shaft is retracted by the spring return force, etc., and becomes the pen-up state. good.

[Effect of idea]

As is clear from the above description, the solenoid control circuit for the writing head according to the present invention can reduce the impact on the tip of a writing device such as a pen during pen-down operation, thereby preventing damage to the writing device. This can extend the life of the writing surface, prevent damage to the paper used as the writing surface, and reduce impact noise. Furthermore, the pen-down operation is performed reliably, the so-called start-up characteristics of the operation are improved, and the time from the start of the pen-down drive until reaching the pen-down state is shortened.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the circuit in FIG. 1, and FIG. 3 is a circuit diagram showing an example of a pulse width modulation circuit. FIG. 4 is a circuit diagram for explaining the operation of the circuit in FIG. 3, FIG. 5 is a block circuit diagram showing a modification of the above embodiment, and FIG. 6 is a diagram showing the solenoid drive control operation by the above embodiment circuit. It is a graph showing the relationship between stroke and speed. 1...Input terminal, 2...Pentown operation signal generation circuit, 3...Integrator circuit, 4...Level addition circuit, 7...Pulse width modulation circuit, 8...Solenoid holding output generation circuit, 9...Drive Circuit, 10...output terminal.

Claims (1)

[Scope of Claim for Utility Model Registration] In a solenoid control circuit for a writing head for controlling a solenoid plunger that drives the writing means of the writing head of an automatic writing device vertically up and down with respect to the writing surface, a down-action signal generation circuit that generates a down-action pulse signal for bringing the tip of the writing device into contact with the writing surface by moving the writing device in a direction; an integrating circuit that integrates this down-action pulse signal; and an integral from this integrating circuit. A level addition circuit that adds a constant DC level to the output to improve the rise characteristic at the start of driving within the output period of the down operation pulse signal, and a pulse width modulation of the output from this level addition circuit to increase the What is claimed is: 1. A solenoid control circuit for a writing head, comprising: a pulse width modulation circuit that outputs a pulse signal whose pulse width gradually increases; and the solenoid plunger is driven and controlled by the output from the pulse width modulation circuit.