JPH0732516U - Index pulse generator - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to an index pulse generator, and an object thereof is to be able to generate an index pulse with stable timing. The rotation speed detection means 11 generates a rotation speed detection pulse having a frequency corresponding to the rotation speed of a rotating body and having an index portion indicating that the rotating body is at a predetermined rotation position. Index part detecting means 12
Detects the index portion of the rotation speed detection pulse supplied from the rotation speed detection means 11 and generates an index portion detection signal. The index pulse generation means 13 is supplied with the index portion detection signal and the rotation speed detection pulse, and is supplied with the index portion detection signal, and then, when the predetermined number of rotation speed detection pulses arrive, the rotation An index pulse synchronized with the speed detection pulse is generated.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an index pulse generator, and more particularly to an index pulse generator using a photo encoder.

[0002]

[Prior art]

 FIG. 8 is a block diagram of a conventional index pulse generation device. FIG. 9 shows an explanatory diagram of the photo encoder 21. A photo encoder is used to detect the number of rotations of a rotating body such as a rotary head or a spindle motor. The photo encoder 21 generates an encoder pulse having a frequency proportional to the rotation speed of the rotating body.

The photo encoder 21 includes a slit member 31, a photo sensor 44, and a waveform shaping circuit 45. The slit member 31 rotates about the shaft 31a as the rotator rotates. A predetermined number of teeth 32 are provided at equal angles along the circumference of the slit member 31. A slit 33 having a predetermined length is formed between the adjacent teeth 32. However, an index portion (tooth missing portion) 34 having a tooth missing is formed at one location on the circumference.

As shown in FIG. 9B, the photo sensor 44 includes a photo interrupter 41 and resistors R ₄₂ and R ₄₃ . As shown in FIGS. 9A and 9B, the photo interrupter 41 is positioned so that the teeth 32 of the slit member 31 are fitted in the grooves 41a of the photo interrupter 41.

When the teeth 32 of the slit member 31 are located in the groove portion 41a, the light of the LED of the photo interrupter 41 is blocked, and the output terminal of the photo interrupter 41 (the collector of the phototransistor) is at the high level ( H level). When the slit 33 of the slit member 31 is located in the groove 41a, the light of the LED of the photo interrupter 41 enters the phototransistor, and the output terminal of the photo interrupter 41 becomes low level (L level).

The output signal of the photo sensor 44 (output signal of the photo interrupter 41) is supplied to the comparator 49 via the buffer amplifier 46 of the waveform shaping circuit 45. The threshold voltage of the comparator 49 is set by the constant voltage diode D ₄₈ connected to the power source via the resistor R ₄₇ , and the input analog signal is converted into a digital signal and output. Here, the threshold voltage is V _th1 . The output signal of the waveform shaping circuit 45 is an encoder pulse.

FIG. 10 shows a timing chart of signals of respective parts of the index pulse generating device of FIG. Here, it is assumed that the rotating body and the slit member 31 are rotating at a constant speed, and an encoder pulse having a constant frequency (cycle T ₁ ) is generated.

As shown in FIG. 10 (A), the output signal of the photosensor 44 increases when the tooth 32 is located in the groove 41a and decreases when the slit 33 is located in the groove 41a. It is a wavy signal. When the index portion 34 is not located in the groove portion 41a, the cycle T ₁ is constant, but when the index portion 34 ₁ with the missing tooth 32 is located in the groove portion 41a, the cycle T ₁ is It has changed and the minimum level has dropped.

[0009] The output signal of the waveform shaping circuit 45 (encoder pulses), by sea urchin shown in FIG. 10 (B), at the H level when the output signal of the photo sensor 44 exceeds a threshold value V _th1, the threshold value V _th1 following It is a pulse which sometimes becomes L level. When the rotation speed of the slit member 31 is constant, the cycle T ₁ is constant. However, when the index portion 34 with the missing tooth 32 is located on the photo sensor 44, one pulse is missing as shown by the dotted line in FIG. The missing part of this pulse is the index part (missing part) of the encoder pulse. This encoder pulse is supplied to the tacho pulse generation circuit 22 of FIG.

The tacho pulse generation circuit 22 generates a tacho pulse (FIG. 10C) synchronized with the encoder pulse. This tacho pulse is supplied to the monitoring timer 23. The monitoring timer 23 monitors the time interval of the tacho pulse and generates a time-out pulse (FIG. 10 (D)) when the tacho pulse is not supplied for the reference time t _R1 or longer. The reference time t _R1 is set to T ₁ <t _R1 <2 · T ₁ .

As shown in FIG. 10, this time-out pulse is generated in the index portion where one tacho pulse is missing.

The index pulse generation circuit 24 is supplied with a tacho pulse and a time-out pulse, and generates an index pulse (FIG. 10 (E)) in synchronization with the tacho pulse that comes after the time-out pulse.

In the case of a tape streamer using a rotary head, the index pulse is used for switching control of the rotary head.

[0014]

[Problems to be solved by the device]

Due to the characteristics of the photo sensor 44, the timing t _{T1 at which} the output voltage of the photo sensor 44 first reaches the threshold voltage V _th1 after the index portion (tooth missing portion) 34 of the slit member 31 passes through the photo sensor 44 (see FIG. 10 (A)) becomes unstable.

In the conventional index pulse generation device, the index pulse is generated based on the unstable timing t _T1 after the index portion of the encoder pulse, which causes a problem that the timing of the index pulse becomes unstable. is there. For example, when the rotary head switching control is performed on the basis of the index pulse, if the timing of the index pulse becomes unstable, the rotary head switching cannot be performed accurately.

The present invention has been made in view of the above points, and an object thereof is to provide an index pulse generation device capable of generating an index pulse with stable timing.

[0017]

[Means for Solving the Problems]

 FIG. 1 shows the basic configuration of the present invention. In the invention of claim 1, the rotation speed detection means 11 has a frequency corresponding to the rotation speed of the rotating body, and has a rotation speed detecting pulse having an index portion indicating that the rotating body is in a predetermined rotating position. To generate.

The index portion detecting means 12 detects the index portion of the above rotation speed detection pulse supplied from the above rotation speed detecting means 11 and generates an index portion detection signal.

The index pulse generation means 13 is supplied with the index part detection signal and the rotation speed detection pulse, and when a predetermined number of rotation speed detection pulses arrive after the index part detection signal is supplied. At the same time, an index pulse synchronized with the rotation speed detection pulse is generated.

In the invention of claim 2, the rotation speed detecting means 11 has a frequency corresponding to the rotation speed of the rotating body and has a rotating speed having an index portion indicating that the rotating body is at a predetermined rotating position. Generate a detection pulse.

The index portion detecting means 12 detects the index portion of the above rotation speed detection pulse supplied from the rotation speed detecting means 11, and generates an index portion detection signal.

The index pulse generation means 13 is supplied with the index portion detection signal and the rotation speed detection pulse, and is synchronized with the rotation speed detection pulse after a predetermined time has elapsed since the index portion detection signal was supplied. To generate the index pulse.

[0023]

[Action]

 According to the invention of claim 1, when the predetermined number of rotation speed detection pulses arrive after the index portion detection signal is supplied and the timing of the rotation speed detection pulse is sufficiently stable, the rotation speed detection pulse is detected. Generate a synchronized index pulse. Therefore, even if the timing of the rotation speed detection pulse becomes unstable immediately after the index portion, it is possible to generate an index pulse with sufficiently stable timing.

According to the second aspect of the present invention, the index synchronized with the rotation speed detection pulse is provided when the timing of the rotation speed detection pulse is sufficiently stable after a predetermined time has elapsed after the index detection signal is supplied. Generate a pulse. Therefore, even if the timing of the rotation speed detection pulse becomes unstable immediately after the index part, it is possible to generate an index pulse with sufficiently stable timing.

Further, even if the rotation speed detection pulse, which should originally exist, is lost immediately after the index portion, in synchronization with the rotation speed detection pulse that arrives after a predetermined time has elapsed from the time when the index portion was detected, It is possible to generate the index pulse at a fixed timing.

[0026]

【Example】

 FIG. 2 is a block diagram of an index pulse generator according to the first embodiment of the present invention. The index pulse generation device of FIG. 2 includes a photo encoder 21, a tacho pulse generation circuit 61, a monitoring timer 62, an index pulse generation circuit 63, and a clock generation circuit 64. The photo encoder 21 which is the rotation speed detecting means in FIG. 2 has the same configuration as the photo encoder 21 described in FIGS. 8 and 9, and thus the description thereof will be appropriately omitted.

FIG. 3 and FIG. 4 show timing charts of signals of respective parts of the index pulse generation device of FIG. Note that (B), (C), and (G) in FIG. 4 are the same signals as (B), (C), and (G) in FIG. Here, it is assumed that the rotating body and the slit member 31 are rotating at a constant speed, and an encoder pulse having a constant frequency (cycle T ₁ ) is generated. As shown in FIG. 3A, the output signal of the photo sensor 44 is a substantially sinusoidal signal that increases when the tooth 32 is located in the groove 41a and decreases when the slit 33 is located in the groove 41a. Is. When the index portion 34 is not located in the groove portion 41a, the cycle T ₁₁ is constant, but when the index portion 34 lacking the tooth 32 is located in the groove portion 41a, as shown by the arrow P ₁₁ , Has changed and the minimum level has decreased.

As shown in FIG. 3B, the encoder pulse (rotational speed detection signal) output from the waveform shaping circuit 45 is at H level when the output signal of the photo sensor 44 exceeds the threshold value V _th1 , This pulse has an L level when the threshold value is V _th1 or less. When the rotation speed of the slit member 31 is constant, the cycle T ₁₁ is constant. However, when the index portion 34 lacking the tooth 32 is located on the photo sensor 44, one pulse is missing as shown by the dotted line in FIG. The missing part of this pulse is the index part (tooth missing part) of the encoder pulse. This encoder pulse is supplied to the tacho pulse generation circuit 61 of FIG.

The slit member 31 is in a tooth missing state, for example, with one of the 128 teeth 32 as an index portion 34. When the rotation speed of the slit member 31 is, for example, 7500 rpm, the cycle T _{11 of the} encoder pulse is about 62.5 μs (frequency, about 16 kHz).

The clock generated by the clock generation circuit 64 is set to a frequency sufficiently higher than the frequency of the encoder pulse. For example, the cycle T _{11 of the} encoder pulse is about 6 2.5 μs, and the cycle T _K of the clock is about 244 ns (frequency, about 4 MHz).

The tacho pulse generation circuit 61 is composed of flip-flops 65, 66, 67, 69 and an AND circuit 68. 3D to 3G show output signals of the Q output terminals of the flip-flops 65, 66, 67 and 69, respectively. The output signal of the flip-flop 69 (FIG. 3G) is a tacho pulse.

As shown in FIG. 3, the tacho pulse generation circuit 61 generates a tacho pulse synchronized with the third clock after the encoder pulse changes from the L level to the H level. The tacho pulse generation circuit 61 generates a tacho pulse synchronized with the clock, in which the influence of noise on the encoder pulse is removed. The pulse width of the tacho pulse is 1 clock cycle. In FIG. 3, the clock cycle T _K is set longer for the sake of explanation, but in reality, the clock cycle T _K is sufficiently shorter than the encoder pulse cycle T ₁₁ . Therefore, the tacho pulse generation timing is very close to the rising timing of the encoder pulse.

The monitoring timer 62 includes a counter 71, a flip-flop 72, and an OR circuit 73. The monitoring timer 62 monitors the time interval of the tacho pulse, and the reference time t _R11 When the tacho pulse is not supplied, the time-out pulse is generated.

The counter 71 counts a fixed number of clocks from the time when the H-level signal is supplied to the reset terminal R and is reset, and when the counting is completed, the counter 71 outputs the H-level count from the output terminal T C. The end pulse (FIG. 4 (H)) is output. The counting time of this clock is the reference time t_R11Becomes This reference time t_R11Is T₁₁<T_R11<2-T₁₁Is set to. For example, the period of the encoder pulse (that is, the period of the tacho pulse) T₁₁Is 62.5 μs, clock cycle T_KIs 244 ns, the reference time t _R11 Is about 100 μs, the count value of the counter 71 is 410.

When the tacho pulse arrives within the reference time t _R11 , the counter 62 is reset via the OR circuit 73, so that the output signal of the counter remains L level. Since one tacho pulse is missing at the position corresponding to the index portion of the encoder pulse, the tacho pulse does not arrive for the reference time t _R11 or more, and the count end pulse of H level is generated. A time-out pulse (index part detection signal) is output from the Q output terminal of the flip-flop 72 one clock after the count end pulse (FIG. 4 (I)).

Next, the index pulse generation circuit 63 will be described. The index pulse generation circuit 63 is composed of flip-flops 75 to 79.

FIGS. 4J to 4N show signals at the Q output terminals of the flip-flops 75 to 79, respectively. The output signal of the flip-flop 78 (FIG. 4 (M)) is the index pulse.

The flip-flop 75 outputs an H-level signal when the index section is detected and a time-out pulse is supplied. The flip-flops 76 to 78 form a three-stage shift register. The output signals of the flip-flops 76 to 78 become the H level at the first tacho pulse, the second tacho pulse, and the third tacho pulse that arrive after the output signal of the flip-flop 75 becomes the H level. Therefore, the index pulse becomes H level at the third tacho pulse.

The output signal of the flip-flop 79 becomes H level with a delay of one clock from the index pulse. The output signal of the flip-flop 79 resets the flip-flop 78. Therefore, the pulse width of the index pulse is one clock cycle. Further, the flip-flops 75 to 77 are reset when the index pulse becomes H level.

As described above, the index pulse generation circuit 63 generates an index pulse synchronized with the third octopus pulse that has arrived after the index portion is detected and the timeout pulse is supplied.

Here, it is assumed that the timing at which the output voltage of the photosensor crosses the threshold value V _th1 is sufficiently stable with respect to the third tooth 32 and subsequent teeth following the index portion 34 of the slit member 31. In this case, the timing is sufficiently stable for the third and subsequent encoder pulses and tacho pulse that arrive after the index section. Therefore, the index pulse generation circuit 63 can generate an index pulse whose timing is sufficiently stable.

As described above, in the first embodiment, when a predetermined number of encoder pulses arrive after the index portion of the encoder pulse and the timing of the encoder pulse is sufficiently stable, the index synchronized with the encoder pulse is obtained. Generate a pulse. Therefore, it is possible to generate an index pulse whose timing is sufficiently stable without being influenced by the timing of the output signal of the photo sensor 44 becoming unstable after the index unit 34.

Therefore, for example, when the rotary head switching control is performed based on this index pulse, the rotary head switching can be accurately performed.

The timing of generating the index pulse is not limited to the third encoder pulse after the index section, and may be synchronized with the encoder pulse when the timing of the encoder pulse is sufficiently stable. Therefore, in some cases, the index pulse may be generated in synchronization with the fourth and subsequent encoder pulses after the index section.

FIG. 5 is a block diagram of an index pulse generator according to a second embodiment of the present invention. 5, the same components as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted as appropriate. In the second embodiment, a retriggerable one-shot multivibrator 82 is provided as a monitoring timer for detecting the index portion. Further, an index pulse generation circuit 83 is provided.

FIG. 6 shows a time chart of signals at various parts of the circuit of FIG. 6 (B), (C), and (G) are the same signals as those in FIGS. 3 (B), (C), and (G). FIG. 6 (O) shows the output signal (timeout pulse) of the one-shot multivibrator 82. The one-shot multi-vibrator 82 is triggered by the rising edge of the signal supplied to the trigger terminal TR and outputs an H level signal from the output terminal O. Output signal pulse width (H level time) t_R12Is T₁₁<T_R12<2 · T ₁₁ Is set to. This pulse width t_R12Is the reference time.

When the tacho pulse arrives within the reference time t _R12 , the one-shot multivibrator 82 is re-triggered before the output signal returns from the H level to the L level, so that the output signal maintains the H level. . At the location corresponding to the index portion of the encoder pulse, one tacho pulse is missing, so the tacho pulse does not arrive for the reference time t _R12 or longer, and at the point when t _{R12 has} elapsed from the tacho pulse immediately before the index portion, one shot The output signal of the multivibrator 82 becomes L level, and a time-out pulse is generated. This time-out pulse (index part detection signal) is supplied to the index pulse generation circuit 83.

The index pulse generation circuit 83 includes a one-shot multivibrator 86, inverter circuits 85 and 87, flip-flops 88 and 90, and an AND circuit 89.

6 (P) to 6 (S) show the output signal of the one-shot multivibrator 86, the output signal of the flip-flop 88, the output signal of the AND circuit 89, and the output signal of the flip-flop 90, respectively. The output signal of the AND circuit 89 (FIG. 6 (R)) is an index pulse.

The one-shot multivibrator 86 is triggered by the rising edge of the signal supplied to the trigger terminal TR and outputs an H level signal from the output terminal O. That is, triggered by the falling edge of the time-out pulse output from the one-shot multivibrator 82, an H-level pulse having a constant time width t _R13 is output.

The time width t _R13 is set so that the falling timing t _T21 of this output pulse comes before the third tacho pulse that arrives after the index portion. The relationship between the pulse width t _R13 of the one-shot multivibrator 82 and the period T _{11 of the} encoder pulse is set to 3 · T ₁₁ <t _R12 + t _R13 <4 · T ₁₁ .

The output signal of the flip-flop 88 becomes H level at the falling timing t _T21 of the output pulse of the one-shot multivibrator 86. The output signal of the AND circuit 89 becomes H level at the rising edge of the first arriving tacho pulse after the timing t _T21 . Therefore, after the timing t _T21 , the H-level index pulse is generated at the first rising edge of the tacho pulse.

The output signal of the flip-flop 90 becomes H level with a delay of one clock from the time when the index pulse is generated. The output signal of the flip-flop 90 is supplied to the reset terminal R of the flip-flop 88 as a reset signal. Therefore, the pulse width of the index pulse is one clock cycle.

The generated index pulse is synchronized with the third encoder pulse that arrives after the index section.

Here, it is assumed that the timing at which the output voltage of the photo sensor crosses the threshold value V _th1 is sufficiently stable with respect to the third tooth 32 and subsequent teeth following the index portion 34 of the slit member 31. In this case, the timing is sufficiently stable for the third and subsequent encoder pulses that arrive after the index section. Therefore, the index pulse generation circuit 83 can generate an index pulse whose timing is sufficiently stable.

As described above, in the second embodiment, an index pulse synchronized with the encoder pulse is generated when the timing of the encoder pulse is sufficiently stable after a certain time has elapsed after the index portion of the encoder pulse. . Therefore, the index pulse whose timing is sufficiently stable can be generated without being influenced by the timing of the output signal of the photosensor 44 becoming unstable after the index unit 34.

Immediately after the index section, the output voltage of the photo sensor 44 does not become equal to or higher than the threshold voltage V _th1 for several cycles, and the encoder pulse that should be present is missing. There are cases. In this case, it is possible to generate the index pulse in synchronization with the encoder pulse that arrives after the missing portion of the encoder pulse after a certain time has elapsed from the time when the index portion was detected. Therefore, the index pulse can be generated at a constant timing without being affected by the loss of the encoder pulse.

The timing of generating the index pulse is not limited to the third encoder pulse after the index section, and may be synchronized with the encoder pulse when the timing of the encoder pulse is sufficiently stable. Therefore, in some cases, the time width t of the one-shot multivibrator 86 is set so as to generate the index pulse in synchronization with the fourth and subsequent encoder pulses after the index section. _R13 May be set.

FIG. 7 is a circuit diagram showing another example of the index portion detection circuit. In FIG. 7, the same components as those of the photo encoder 21 of FIG. 9B are designated by the same reference numerals. In the example of FIG. 7, a waveform shaping circuit 51 is provided to detect the index portion. The reference voltage V _th2 is set by the constant voltage diode D ₅₃ . As shown in FIG. 3A, the reference voltage V _th2 is set to a value slightly higher than the minimum value of the output voltage of the photo sensor 44 in the index section. As a result, when the output voltage of the photosensor becomes equal to or lower than the reference voltage V _{th2 in} the index section, the comparator 54 generates an H level index section detection pulse.

Instead of the monitoring timer 62 of the first embodiment shown in FIG. 2, the index section detection circuit of FIG. 7 may be used to configure an index pulse generator having the same function as that of the first embodiment. it can.

Further, instead of the one-shot multivibrator 82 of the second embodiment of FIG. 5, the index detection circuit of FIG. 7 (provided that the polarity of the output signal of the comparator 54 is reversed) is used for the second operation. An index pulse generator having the same function as that of the embodiment can be configured. In this case, the time width t _R13 of the one-shot multivibrator 86 is set so that the timing t _T21 of the rear end of the output pulse of the one-shot multivibrator 86 becomes an appropriate timing.

[0062]

[Effect of device]

 As described above, according to the invention of claim 1, when the predetermined number of rotation speed detection pulses arrive after the index portion detection signal is supplied and the timing of the rotation speed detection pulses is sufficiently stable, Since the index pulse synchronized with the above rotation speed detection pulse is generated, even if the timing of the rotation speed detection pulse becomes unstable immediately after the index part, it is possible to generate an index pulse with sufficiently stable timing. Have.

According to the invention of claim 2, when the timing of the rotation speed detection pulse is sufficiently stabilized after a predetermined time has passed after the index detection signal is supplied, the rotation speed detection pulse is synchronized with the rotation speed detection pulse. Since the generated index pulse is generated, even if the timing of the rotation speed detection pulse becomes unstable immediately after the index part, the index pulse with sufficiently stable timing can be generated.

Further, even if the rotation speed detection pulse that should originally be missing immediately after the index portion, in synchronization with the rotation speed detection pulse that arrives after a predetermined time has elapsed from the time when the index portion was detected, The index pulse can be generated at a fixed timing.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of the present invention.

FIG. 2 is a configuration diagram of an index pulse generator according to a first embodiment of the present invention.

FIG. 3 is a timing chart of signals of various parts in FIG.

FIG. 4 is a timing chart of signals at various parts in FIG.

FIG. 5 is a configuration diagram of an index pulse generator according to a second embodiment of the present invention.

FIG. 6 is a timing chart of signals of respective parts of FIG.

FIG. 7 is a circuit diagram showing another example of the index portion detection circuit.

FIG. 8 is a configuration diagram of a conventional index pulse generation device.

FIG. 9 is an explanatory diagram of a photo encoder.

FIG. 10 is a time chart of signals of respective parts of FIG.

[Explanation of symbols]

 Reference Signs List 11 rotation speed detecting means 12 index detecting means 13 index pulse generating means 21 photo encoder 31 slit member 41 photo interrupter 44 photo sensor 45, 51 waveform shaping circuit 61 tacho pulse generating circuit 62 monitoring timer 63 index pulse generating circuit 64 clock generating circuit 83 Index pulse generation circuit

Claims (5)

[Scope of utility model registration request] 1. A rotation speed detecting means for generating a rotation speed detection pulse having a frequency corresponding to a rotation speed of a rotating body and having an index portion indicating that the rotating body is in a predetermined rotation position, Detecting the index part of the rotation speed detection pulse supplied from the rotation speed detection means, an index part detection means for generating an index part detection signal, and the index part detection signal and the rotation speed detection pulse supplied, An index pulse generation device having index pulse generation means for generating an index pulse synchronized with the rotation speed detection pulse when a predetermined number of the rotation speed detection pulses arrive after being supplied with the index detection signal. 2. A rotation speed detecting means for generating a rotation speed detection pulse having a frequency corresponding to a rotation speed of the rotating body and having an index portion indicating that the rotating body is at a predetermined rotation position, Detecting the index portion of the rotation speed detection pulse supplied from the rotation speed detection means, the index portion detection means for generating an index portion detection signal, the index portion detection signal and the rotation speed detection pulse is supplied, An index pulse generation device having index pulse generation means for generating an index pulse synchronized with the rotation speed detection pulse after a predetermined time has elapsed after the index portion detection signal was supplied. 3. The rotation speed detecting means has slits of a predetermined length formed in the circumferential direction along the circumference at predetermined angles.
Moreover, a slit longer than the slit length other than the index portion is formed as the index portion, and a slit member that rotates with the rotation of the rotating body and a photosensor that detects the slit are used. Two
The described index pulse generation device. 4. The index pulse generation device according to claim 1, wherein the index portion detection means generates an index portion detection signal when the rotation speed detection pulse does not arrive for a predetermined time. 5. The index pulse generation device according to claim 3, wherein instead of the index detection means, an output voltage of the photo sensor is compared with a reference voltage to generate an index detection signal.