JP3076218B2 - Automatic paper thickness detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic paper thickness detecting method.

[0002]

2. Description of the Related Art Conventionally, in a printer in which printing is performed by driving a wire dot type print head, printing is performed by projecting a print wire from a print head in accordance with print data. . In this case, for example, the gap from the leading end of the print head to the surface of the paper differs between when the paper is thin paper and when it is thick paper, copy paper, or the like. Therefore, the thickness of the paper (hereinafter referred to as "paper thickness") is detected before printing is started, and the gap is adjusted based on the detected paper thickness.

In the automatic paper thickness detection method based on the inductance detection method, the carriage is pushed in the direction of the platen by the stepping motor, and the change in inductance when the detector is abutted against the paper is observed. For this purpose, a coil is wound around one of a pair of ferrite cores (UI type and UU type) made of a ferromagnetic material, and a gap distance between the ferrite cores (hereinafter referred to as a “core gap”). The change in inductance is converted into a pulse using an LC oscillation circuit, and the change in frequency is determined. Then, when the amount of change in the frequency exceeds a set value, a determination is made that the detector has hit the sheet (hereinafter, referred to as a "hitting determination").

In this case, a sampling time for detecting a change in frequency is set to be equal to a phase switching cycle of a stepping motor for pushing a carriage toward a platen, and output from the LC oscillation circuit within the sampling time. The number of pulses is counted by a timer counter, and it is determined whether or not the count value changes.

[0005]

However, in the above-mentioned conventional automatic paper thickness detection method, in order to increase the gap accuracy of the print head, a collision determination is made for each phase switching cycle which is the minimum resolution of the stepping motor. In addition to the necessity, the stepping motor must be driven within the self-starting frequency so that the stepping motor can be stopped immediately after the detector hits the paper, and the phase switching cycle is shortened. Can not do.

[0006] Therefore, if the paper thickness is to be detected in a printer capable of printing on thick paper, copy paper, or the like,
Since the home position of the print head is located away from the platen and the gap is two to three times that of a normal printer, the thickness of thin paper such as plain paper (55 kg: single paper) is detected. If this is attempted, the operating distance until the detector hits the paper becomes long, and the time until the frequency change starts becomes long. As a result, the time required to detect the paper thickness increases.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional automatic paper thickness detection method and to provide an automatic paper thickness detection method capable of detecting various paper thicknesses in a short time.

[0008]

For this purpose, in the automatic paper thickness detecting method of the present invention, a pulse signal is generated by pulse-converting an inductance corresponding to a core gap.
A sample time is set by a first timer counter, the number of pulses of the pulse signal within the sample time is counted by a second timer counter to calculate a sample frequency, and whether the sample frequency has changed based on the sample frequency A determination is made as to whether the detector has hit the paper.

When it is determined that the sample frequency has changed, the sample time is extended,
When it is determined that the detector has hit the sheet, the stepping motor is stopped.

[0010]

According to the present invention, as described above, in the automatic paper thickness detection method, the inductance corresponding to the core gap is pulse-converted to generate a pulse signal, and the sample time is set by the first timer counter. The number of pulses of the pulse signal within the sample time is counted by a second timer counter to calculate a sample frequency. Based on the sample frequency, it is determined whether the sample frequency has changed, and whether the detector has hit the paper. Make a decision.

When it is determined that the sample frequency has changed, the sample time is extended,
When it is determined that the detector has hit the sheet, the stepping motor is stopped. In this case, the phase switching cycle can be changed by changing the sample time. Therefore, until the sample frequency changes, a sample time outside the self-starting frequency is set to shorten the phase switching period, and when the sample frequency changes, a sample time within the self-starting frequency is set to change the phase switching period. The cycle can be lengthened.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of a paper thickness detecting circuit according to an embodiment of the present invention, FIG. 2 is a time chart of the paper thickness detecting circuit according to the embodiment of the present invention, and FIG. FIG. 3 is a diagram illustrating a relationship between a pulse rate of a stepping motor and a pulse rate; In FIG. 3, the horizontal axis represents the amount of pushing of the carriage, and the vertical axis represents the sampling frequency f and the pulse rate of the stepping motor.

In FIG. 1, reference numeral 11 denotes a stepping motor for pushing a carriage (not shown) toward a platen, and reference numeral 21 denotes an LC oscillation circuit which detects a change in inductance corresponding to a core gap and converts the change in inductance into a pulse. In this case, in addition to the oscillation circuit itself, the LC oscillation circuit 21 includes a detector (auto gap sensor) for detecting a change in inductance corresponding to the core gap. The detector is attached to the ribbon protector of the carriage, and is pushed together with the carriage toward the platen.

Reference numeral 22 denotes the stepping motor 11
And a first timer counter 23 for generating a sampling time for sampling the pulse signal SG1 from the LC oscillation circuit 21. The first timer counter 23 generates a sampling time for sampling the pulse signal SG1 from the LC oscillation circuit 21 within the sampling time. A second timer counter for counting the number of pulses, 24
Is an inverter for inverting the signal IPT-P of the first timer counter 22 to make it a signal SG2, and 25 is a motor driver for driving the stepping motor 11.

The terminal CLK of the first timer counter 22
1, a clock CLK-P is input as a control signal to a gate terminal GATE1, and a signal IPT-P is output from an output terminal OUT1.
Is output. The signal IPT-P is inverted by the inverter 24 to become a signal SG2, and is input to the gate terminal GATE2 of the second timer counter 23 as a gate signal and output to the motor driver 25.

A pulse signal S from the LC oscillation circuit 21 is applied to a terminal CLK2 of the second timer counter 23.
G1 is input. Further, the motor driver 25 is connected to the stepping motor 11. In the first timer counter 22 and the second timer counter 23, a count value can be arbitrarily set, and a CPU (not shown) inputs a gate signal GATE input to a gate terminal GATE1.
When -P is set to "1", the first timer counter 22 starts counting and sets the signal IPT-P output from the output terminal OUT1 to "0". When the first timer counter 22 finishes counting, the signal IP
TP is set to "1". Thereafter, the CPU sets the gate signal GATE-P to "0".

In the paper thickness detecting circuit having the above-described configuration, the initial frequency before the collision determination is set to f _0, and the first timer counter 2
The sampling time outside the self-starting frequency set to 2 is T _m
, The number of pulses of the pulse signal SG1 within the sample time T _m , that is, the sample frequency is f _m
And then, when the first change amount set to Delta] f _1, if a _{f m -f 0 ≦ Δf 1 ...} (1), the pulse signal from LC oscillating circuit 21 SG1
Sample frequency f _m is determined not to be a change in. Then, continued the pushing of the carriage, determining the frequency change point alpha, becomes the _{f m -f 0> Δf 1 ...} (2), a sample frequency f _m of the pulse signal SG1 from the LC oscillator 21 changes I do. in this case,
Since sample time T _m is set at a self-starting frequency outside of the stepping motor 11, it is possible to increase the rotational speed of the stepping motor 11, the time until it is determined that the sample frequency f _m of the pulse signal SG1 changes Can be shorter.

The pulse signal from the LC oscillation circuit 21 is
The sample frequency f of the signal SG1_mIs determined to have changed
And the sample time is T_mTo T_n(T_m<T_n)
You. As a result, the pulse rate of the stepping motor 11
Is 1 / T_mFrom 1 / T_nbecome. Next, within the self-starting frequency
The sample time of_nAnd the sample time T
_n, The number of pulses of the pulse signal SG1,
Let the sample frequency be f_nAnd the second change amount is Δf_Twoage
When f_n−f₀≤Δf_Two … (3), it is determined that the detector has not hit the paper
I do.

Then, the pushing of the carriage is continued,
When f _n −f ₀ > Δf ₂ (4) at the abutting detection point β, it is determined that the detector has hit the paper. In this case, since the sample time T _n is set in the self-starting frequency of the stepping motor 11, not only the change of the sample frequency f _n can be accurately determined, after abutting the detector sheet, immediately The stepping motor 11 can be stopped.

FIG. 4 is a flowchart showing the operation of the paper thickness detecting circuit according to the embodiment of the present invention. Step S1 A sample time (phase switching cycle) T _m (FIG. 2) outside the self-starting frequency of the stepping motor 11 is set in the first timer counter 22 (FIG. 1). Step S2: The CPU (not shown) outputs the gate signal GATE.
When -P is set to "1", the first timer counter 22 starts counting and sets the signal IPT-P to "0". When the signal IPT-P is set to "0", the signal SG2 inverted by the inverter 24 becomes "1", the gate of the second timer counter 23 opens, and the second timer counter 23 Starts counting the number of pulses of the pulse signal SG1. Step S3: Wait until the signal IPT-P becomes "1". When the first timer counter 22 finishes counting, the signal IPT-P changes from “0” to “1”, and the signal SG2 input to the second timer counter 23 changes from “1” to “0”. As a result, the second timer counter 23 stops counting. Step S4: The CPU sets the gate signal GATE-P to “0” and outputs the clock CL to the first timer counter 22.
Mask the input of K-P. Step S5 for the second sample frequency f _m which is calculated based on the count value of the timer counter 23, it is determined whether an expression (1) is satisfied. If expression (1) is satisfied, the process proceeds to step S8, and if expression (1) is not satisfied, the process proceeds to step S6. Step S6 The phase of the stepping motor 11 is switched. Step S7: Clear the count value of the second timer counter 23 and return to step S1. Step S8 self-start frequency within the sample time of the stepping motor 11 to the first timer counter 22 (phase switching period) is set to T _n. Step S9: Clear the count value of the second timer counter 23. Step S10 The phase of the stepping motor 11 is switched. Step S11: The CPU sets the gate signal GATE-P
Is set to "1", the first timer counter 22 starts counting and sets the signal IPT-P to "0". The signal IP
When TP is set to "0", the signal SG2 inverted by the inverter 24 becomes "1", the gate of the second timer counter 23 opens, and the second timer counter 23
The counting of the number of pulses of the pulse signal SG1 from the oscillation circuit 21 is started. Step S12: Wait until the signal IPT-P becomes "1". When the first timer counter 22 finishes counting, the signal IPT-P changes from “0” to “1”, and the signal SG2 input to the second timer counter 23 changes from “1” to “0”. As a result, the second timer counter 23 stops counting. Step S13: The CPU sets the gate signal GATE-P
To “0” and the clock C to the first timer counter 22
Mask the input of LK-P. Step S14: It is determined whether Expression (3) is satisfied for the sample frequency f _n calculated based on the count value of the second timer counter 23. If Expression (3) is satisfied, the processing is terminated by judging that the detector has hit the sheet, and if Expression (3) is not satisfied, the process returns to Step S8.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0022]

As described above in detail, according to the present invention, in the automatic paper thickness detecting method, a pulse signal is generated by pulse-converting the inductance corresponding to the core gap, and the pulse signal is generated by the first timer counter. A time is set, the number of pulses of the pulse signal within the sample time is counted by a second timer counter to calculate a sample frequency, and based on the sample frequency, it is determined whether or not the sample frequency has changed, and detection is performed. A determination is made as to whether the container has hit the paper.

When it is determined that the sample frequency has changed, the sample time is extended,
When it is determined that the detector has hit the sheet, the stepping motor is stopped. In this case, until the sample frequency changes, a sample time outside the self-starting frequency can be set to shorten the phase switching cycle, increase the rotation speed of the stepping motor, and determine that the sample frequency has changed. Time until the time can be shortened.

When the sample frequency changes,
The phase switching cycle can be lengthened by setting the sample time within the self-starting frequency. Therefore, not only can the change in the sample frequency be accurately determined, but also the stepping motor can be stopped immediately after the detector hits the paper.

[Brief description of the drawings]

FIG. 1 is a block diagram of a paper thickness detection circuit according to an embodiment of the present invention.

FIG. 2 is a time chart of the paper thickness detection circuit according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a pushing amount of a carriage according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating a relationship between a sample frequency and a pulse rate of a stepping motor.

FIG. 4 is a flowchart illustrating an operation of the paper thickness detection circuit according to the embodiment of the present invention.

[Explanation of symbols]

11 the stepping motor 21 LC oscillator circuit 22 first timer counter 23 second timer counter SG1 pulse signal T _m, T _n sample times f _m, f _n sample frequency

Continuation of the front page (56) References JP-A-3-272881 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B ^7/ 00-7/34 102 G01B 21/00- 21/32 B41J 23/00-25/32

Claims (1)

(57) [Claims] 1. A pulse signal is generated by pulse-converting an inductance corresponding to a core gap.
The sample time is set by the first timer counter,
(C) counting the number of pulses of the pulse signal within the sample time by a second timer counter to calculate a sample frequency; (d) determining whether the sample frequency has changed based on the sample frequency; Determine whether the detector has hit the paper,
(E) The sample time is lengthened when it is determined that the sample frequency has changed, and the stepping motor is stopped when it is determined that the detector has hit a sheet. Automatic paper thickness detection method.