JPS5951360A - Rotational speed detector - Google Patents

Abstract

PURPOSE:To prevent erroneous detection of rotational speed due to electrical noises during the stoppage of a rotor by making the photoelectric conversin action of a semiconductor light emitting element function as positive feedback action with respect to a semiconductor light receiving element. CONSTITUTION:A signal processing circuit 30 is equippd with resistances 41 and 42 connected in series to an LED32, a transistor 43 Darlington connected to a photo transistor 33, a switching transistor 46 and the like. One end of the resistance 42 is connected to the cathode of the LED32 and the emitter of the transistors 33 and 43 while the other end thereof connected to the ground through a resistance 44. In response to photoelectric conversion action of the transistor 33 accompanied by reception of light from the LED32, the conduction level of the transistor 46 is controlled through the resistances 42 and 44 to effect a positive feedback of forward current of the LED32. The transistor 33 in any of the action area and the interruption area responds to the corrsponding area free from electrical noises when rotor is stopped thereby preventing erroneous detection of rotational speed due to electrical noises during the stoppage of the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational speed detection device, and more particularly, to a rotational speed detection device that includes a semiconductor light emitting element and a semiconductor light receiving element, and detects the rotational state of a rotating member by the photoelectric conversion action of these pixel elements. The present invention relates to a rotational speed detection device that generates a result as an output signal corresponding to the rotational speed of the rotating member.

Conventionally, this type of rotational speed detection device includes, for example, a disc formed by a series of slits formed along the outer peripheral edge of the disc, which are connected to rotate in conjunction with a rotating member; a light emitting diode disposed to face the outer peripheral edge and emitting light toward the outer peripheral edge of the disk when electrically connected by power supply from a power source; a phototransistor that is arranged to face each other and receives light from the light emitting diode through each slit of the disk according to the rotational state of the rotating member, and detects this as a light reception signal when electrical conduction occurs; Some devices include a signal processing circuit that responds to a light reception signal from a transistor and generates an output signal corresponding to the rotational speed of the rotating member.

By the way, in such a rotational speed detection device, the above-mentioned phototransistor, as the disk rotates,
By changing the operating region from the cutoff region to the saturation region (or from the saturation region to the cutoff region), the level of the received light signal is changed from a mutually different first level to a second level (or from the idM2 level to the second level). This fact is utilized to generate the above-mentioned output signal from the signal processing circuit. For example, when the rotating member is in a stopped state, the relative relationship between the disk and the light emitting diode is Depending on the rotational positional relationship, there may be a phenomenon in which the transistor e)) operates in the active region due to an insufficient amount of light received and maintains the level of the light reception signal at an intermediate level between the first and second levels. arise.

Therefore, in such a case, if electrical noise caused by, for example, mechanical vibration of the disc is mixed into the received light signal, the level of the received light signal will change from the above-mentioned intermediate level to the first or second level. As a result, the output signal from the signal processing circuit is erroneously generated as corresponding to a different rotational speed even though the rotational speed of the rotating member is zero. there were.

The present invention has been made in response to the above-mentioned problems, and its purpose is to detect the rotational speed of a rotating member using the photoelectric conversion effects of a semiconductor light emitting element and a semiconductor light receiving element. It is an object of the present invention to provide a rotational speed detection device in which the photoelectric conversion action of a semiconductor light emitting element functions as a positive feedback action to the semiconductor light receiving element.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
In the figures and FIG. 2, numeral 10 indicates a rotating member such as an output shaft of a vehicle internal combustion engine, and numerals 20 and 60 indicate a disk and a photointerrupter, respectively.

The disk 20 is integrally supported pivotally by the rotating member 10 at its center, and a series of slits 21, . . . , 21 and projections 22 . ...,
22 are formed alternately at equal intervals. The photointerrupter 60 includes a casing 61 fixed to a part of a suitable stationary structure near the disk 20, and a pair of protrusions 31 provided on the casing 31 at a predetermined distance.
The outer peripheral edge of the disc 20 is interposed between a, 3i and b. Further, within the protruding portion 31a of the casing 61, a light emitting diode 62 generates a forward current according to the degree of conduction due to its conduction, and an amount corresponding to the forward current toward the outer peripheral edge of the disk 20. On the other hand, in the protruding portion 3Ib of the casing 31, a phototransistor 63 is provided to receive light from the light emitting diode 32 through the slit 21 of the disk 20 and to conduct to the same degree as when it is electrically conductive. The light-receiving current is generated accordingly.

As shown in FIG. 6, the signal processing circuit 40 includes resistors 41 and 42 connected in series to a light emitting diode 62, and a transistor 46 connected to a phototransistor 36 in Darlington. It is connected between the side terminal and the anode of the light emitting diode 32, and applies the power supply current from the DC power supply VD to the light emitting diode 62 while limiting it to a value necessary to generate a forward current in the light emitting diode 62. The resistor 42 has one end connected to the cathode of the light emitting diode 62, the emitter of the phototransistor 36, and the emitter of the transistor 46, and the other end of the resistor 42 is grounded via the resistor 44. This means that the parallel combined resistance value of the resistance reduction of both resistors 42 and 44 and the internal resistance value corresponding to the degree of conduction of the transistor 33 increases (or decreases) the internal resistance value of the phototransistor 66. This means that the degree of conduction of the light emitting diode 62 is decreased (or increased) by increasing (or decreasing) accordingly. Note that the DC power supply VD is grounded at its negative terminal.

Therefore, the resistor 42 is
, receives the forward current from the light emitting diode 32 and, in cooperation with the resistor 44, generates the bias voltage necessary to conduct the transistor 46 at its common terminal with the resistor 44. Furthermore, when the phototransistor 66 operates in the active region, the resistor 42 causes the forward current to flow as a light-receiving current to the phototransistor 33 according to the degree of conduction between the phototransistor 66 and the phototransistor 33. When 33 operates in the saturation region, most of the light-receiving current flows into the phototransistor 36 as a light-receiving current, and the bias voltage is lowered to a value necessary to make the transistor 26 non-conductive. Note that the transistor 45 is in an operating state corresponding to the operating state of the phototransistor 66.

The transistor 46 functions as a switching element, and has its base connected to the common terminal of the sheet resistors 42 and 44, and its collector connected to the positive terminal of the DC power supply vD via the resistor 45. There is. However,
Transistor 46 becomes conductive in response to a bias voltage developed at the common end of sheet resistors 42, 44, and becomes non-conductive in response to a decrease in such bias voltage. This means that the transistor 46 produces a speed signal from its collector, ie the output terminal 46/l, which corresponds to the rotational speed of the rotating member 100 due to its repeated conduction and non-conduction.

In this embodiment configured as follows, when the light emitting diode 62 is supplied with power from the DC power supply VD through the resistor 41 and becomes conductive, it generates a forward current and emits light. For example, if all the light is received by the phototransistor 33 through the slit 21 of the disk 20 in the stopped state,
(I-) The transistor 3 is conductive in its saturation region, the transistor 43 is also conductive, and most of the forward current from the light emitting diode 32 flows into the phototransistor 66 and the transistor 46, and the common sheet resistance 42.44 No bias voltage is generated at the terminal, and transistor 46 remains non-conducting, producing a high level signal from output terminal 46a.

When the disk 20 starts rotating in response to 100 rotations of the rotating member in this state, the phototransistor 33
One of the series of protrusions 22 of the light emitting diode 6
The light reception from the light emitting diode 32 is blocked and the transistor 43 operates in the cutoff region, and becomes non-conductive together with the transistor 43.The resistor 42 receives the light reception current from the light emitting diode 32 and generates a bias voltage at the common terminal with the resistor 44, and the transistor 46 conducts in response to a bias voltage applied thereto, and its output terminal 46
A low level signal is generated from a. Thereafter, as the disk rotates 200 times, the phototransistor 63 alternately receives light from the light emitting diode 32 and blocks it, thereby repeating conduction and non-conduction alternately together with the transistor 43, and the resistor 42 cooperates with the resistor 44. The bias voltage is intermittently generated, and in response, the transistor 46 alternately repeats conduction and non-conduction, thereby alternately producing a low level signal and a high level signal from its output terminal 46a. This means that transistor 4
6 means that these low level signals and high level signals are generated as speed signals corresponding to the rotational speed of the rotating member 10.

As the rotating member 10 stops, the disk 20 is moved by one of its series of protrusions 22 into the phototransistor 3.
When the phototransistor 33 is stopped with light reception from the light emitting diode 32 partially blocked, if the operating region of the phototransistor 33 is in the process of transitioning from the blocking region to the active region, it corresponds to the degree of conduction of the phototransistor 63. Since the parallel combined resistance value of the internal resistance value and the resistance phase of the sheet resistance 42.44 becomes smaller than the resistance phase of the sheet resistance 42.44, both the amount of forward current and the amount of light emission from the light emitting diode 32 increase, As the amount of light received by the phototransistor 63 increases, its operating region shifts toward the saturation region, and its degree of conduction increases (that is, its internal resistance value decreases). Then, the amount of forward current from the light emitting diode 32 flowing into the phototransistor 66 and the transistor 46 increases, and the amount of the forward current flowing into the resistor 42 decreases, thereby lowering the bias voltage of the two series. Accordingly, the transistor 46 becomes non-conductive and its output terminal 461
The output signal from 2 is maintained at a high level.

If the operating region of the phototransistor 33 is still in the process of transitioning from the saturation region to the active region when the disk 20 is stopped as described above, then Since the parallel combined resistance value with the resistance phase of .44 is larger than the internal resistance value in the saturation region of the phototransistor 66, the light emitting diode 6
Both the amount of forward current and the amount of light emitted from the phototransistor 36 decrease, and the phototransistor 36 shifts its operating region toward the cutoff region due to the decrease in the amount of light received, and its degree of conduction decreases (that is, the internal resistance value increases). ). Then, the amount of forward current from the light emitting diode 32 flowing into the phototransistor 33 and the transistor 43 decreases, and the amount of the forward current flowing into the resistor 42 increases, so that the transistor 46 becomes the common source of both resistors 42 and 44. It conducts in response to a bias voltage developed at its terminal 462 to maintain the output signal from its output terminal 462 at a low level.

In other words, when the disk 20 is stopped, the phototransistor 66
Even if the operating region of the light emitting diode 62 is placed in the active region, the amount of light emitted from the light emitting diode 62 will decrease (or increase) in accordance with the above-mentioned increase in the parallel combined resistance value (or decrease in 'i). As a positive feedback effect, the phototransistor 6
Since the operating region of the phototransistor 6 immediately shifts to the cutoff region (or saturation region), the output signal of the transistor 46 is free from electrical noise caused by mechanical vibration of the disk 20, etc. is maintained at low level (or high level) without being affected by SugaIn addition, in the embodiment described above, an example was explained in which the disk 20 and the photointerrupter 30 were used to detect the rotational speed of the rotating member 10. A film is attached, and a pair of a semiconductor light emitting element and a semiconductor light receiving element are arranged facing each other on this film, and the light from the semiconductor light emitting element reflected by the film when the rotating member 10 is rotated is reflected by the semiconductor light emitting element. Even if the light is received by a semiconductor light-receiving element and the result of this light reception is used to detect the rotational speed of the rotating member 100, the same effects as in the embodiment described above can be achieved. In such a case, the resistor 44 may be omitted, and the transistor 46 may be replaced with various semiconductor switching elements such as SIRISK.

As explained above, in the present invention, as exemplified in the above-mentioned embodiments, when the rotating member is disposed to face the rotating body that rotates as the rotating member rotates and receives the applied voltage from the power source and becomes conductive, this a semiconductor light emitting element that generates a forward current depending on the degree of conduction and emits light toward the rotating body in an amount corresponding to the forward current; and a semiconductor light-receiving element that receives light from the semiconductor light-emitting element via the rotating body in response to rotation and generates a light-receiving current according to the degree of conduction when electrically connected, and generates this as a light-receiving signal, A signal processing circuit that responds to the light reception signal and generates the signal as an output signal corresponding to the rotational speed of the rotating member is connected to the semiconductor light emitting element together with the semiconductor light receiving element, and is connected to the semiconductor light receiving element according to the degree of conduction of the semiconductor light receiving element. a resistance element that changes the degree of conduction of the semiconductor light emitting element and receives the forward current at a value defined by the degree of conduction of the semiconductor light receiving element to generate a terminal voltage;
a semiconductor switching element that becomes conductive when the terminal voltage reaches a first predetermined value and becomes non-conductive when the terminal voltage reaches a second predetermined value; and the output signal is determined based on conduction and non-conduction of the semiconductor switching element. Its structural feature lies in the fact that it is made to occur. As a result, as described above, the degree of conduction of the semiconductor light-emitting element changes depending on the degree of conduction of the semiconductor light-receiving element, so that when the rotating member is stopped, the degree of conduction of the semiconductor light-receiving element is set to a value corresponding to its active area. Even if , the amount of light emitted from the semiconductor light emitting element acts on the semiconductor light receiving element in a positive feedback manner, so that the operating region of the semiconductor light receiving element can be immediately shifted to a cutoff region or a saturated region, As a result, the rotational speed of the rotating member is set to zero when the rotating member is stopped, and accurate detection is always possible without the problems described in this specification.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of the disk and photointerrupter that constitute a part of the present invention, FIG. 2 is a side view of the disk and photointerrupter in FIG. 1, and FIG. 3 is a side view of the photointerrupter. FIG. 2 is an electrical circuit diagram of a signal processing circuit connected to the circuit. Explanation of symbols 10... Rotating member, 20... Disc, 32... Light emitting diode, 66... Phototransistor, 40...
Signal processing circuit, 42.44...Resistor, 46...Transistor. Applicant Nippondenso Co., Ltd. Agent Patent Attorney Teru Hase −

Claims (1)

[Claims] When the rotating member is disposed so as to face a rotating body that rotates as the rotating member rotates, and receives an applied voltage from a power source and becomes conductive, a forward current is generated depending on the degree of conduction, and a forward current is generated in accordance with the degree of conduction. a semiconductor light emitting element that emits light toward the rotating body in an amount corresponding to a directional current; and a semiconductor light emitting element that is disposed to face the rotating body and emits light via the rotating body in accordance with rotation of the rotating member. a semiconductor light-receiving element that generates a light-receiving current according to the degree of conduction when electrically connected by receiving light from the element, and generates this as a light-receiving signal; In a rotational speed detection device comprising a signal processing circuit that generates an output signal, the signal processing circuit is connected to the semiconductor light-emitting element together with the semiconductor light-receiving element, and controls the semiconductor light-emitting element according to the degree of conduction of the semiconductor light-receiving element. a resistance element that changes the degree of conduction of the element and generates a terminal voltage by receiving the forward current at a value defined by the degree of conduction of the semiconductor light-receiving element, and the terminal voltage becomes a first predetermined value. and a semiconductor switching element that becomes conductive when a second predetermined value is reached and becomes non-conductive when a second predetermined value is reached, and the output signal is generated based on whether the semiconductor switching element is conductive or non-conductive. Rotation speed detection device.