JP3254676B2 - Rotation direction detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a rotation direction of a rotating body, and more particularly to an apparatus for detecting a rotation direction using magnetism.

[0002]

2. Description of the Related Art As a device for detecting the direction of rotation of a rotating body, there is a device disclosed in Japanese Patent Application Laid-Open No. 2-307011. According to this conventional apparatus, N-poles and S-poles in a stripe shape oblique to the rotation axis are arranged on the outer peripheral surface of the columnar rotating body, and two magnetic detectors are opposed to this,
The direction of rotation is detected based on which detector outputs the detection signal earlier (refer to page 19, upper right column, line 19 to lower left column, line 2).

[0003]

On the other hand, in this type of detecting device, the detecting section and the rotation direction judging section are generally arranged at different places, and therefore are connected by some kind of communication path. According to this conventional device, the rotation direction is detected based on which of the two detectors outputs the detection signal earlier, so that a rotation direction determination unit (arithmetic device) and the detector are connected. Two communication paths must be formed, and the connection becomes complicated. This is particularly problematic when mounting the device.

[0004]

SUMMARY OF THE INVENTION The rotation direction detecting device of the present invention has been made in view of such a problem, and has one cycle of a change of a periodic applied magnetic field accompanying rotation of a rotating body of four.
A magnetic detection unit that classifies and outputs an electric signal at a level corresponding to each classification; and a determination unit that determines a rotation direction of the rotating body based on a change in an output signal level of the magnetic detection unit. .

When one cycle of the magnetic field change is divided into the first to fourth sections, an electric signal indicating any one of the first to fourth sections is output from the magnetic detection section. Here, when the rotating body is rotating forward, the sections indicated by the output signal of the magnetic detection unit are sequentially from the first section to the fourth section, such as 1, 2, 3, 4, 1, 2,. If it is assumed that the change is repeated to return to the first section and the rotating body is rotating in reverse, the section is reversed to 4, 3, 2, 1, 4, 3,.
・ ・ It changes so that it goes down and down repeatedly. Therefore, the discriminator can determine the rotation direction from the state of the change of the section indicated by the output signal of the magnetic detector.

[0006]

FIG. 1 is a block diagram showing an embodiment of a rotation direction detecting device according to the present invention. The rotation direction detection device according to the present embodiment includes a magnetic detection unit 1 and a determination unit 3, both of which are connected by a signal line 2.

The magnetic detecting section 1 has two magnetic sensing elements 16 and 17, and these magnetic sensing elements 16 and 17 are elements for detecting a periodically changing magnetic field generated with the rotation of the rotor described later. is there. Magnetic sensing elements 16, 17
Is an element that converts the strength of a magnetic field into an electric signal, and various elements such as a magnetoresistive element and a Hall element can be used as specific elements. Here, a phenomenon in which electric resistance changes due to a magnetic field is used. A magnetoresistive element is used.

The magnetic sensing elements 16 and 17 receive necessary current supply from the power supply circuit 11 and output voltages according to the applied magnetic field to the amplifiers 14 and 15, respectively. Amplifier 1
Reference numerals 4 and 15 amplify the voltage signals output from the magnetic sensing elements 16 and 17, respectively.

The waveform shaping circuits 12 and 13 include an amplifier 14,
This is a circuit for binarizing 15 output signals with reference to a predetermined threshold value, and the output terminal is connected to the bases of npn transistors 18 and 19. Transistor 1
The emitters of 8 and 19 are both grounded, and the transistor 1
The collectors 8 and 19 are respectively connected to the resistor 2 having the resistance value R1.
0, connected to a resistor 21 having a resistance value R2.

The other ends of the resistors 20, 21 are connected to the output terminal 22, the wiring 2, the input terminal 23 of the discriminating section 3, and the resistor 39 having the resistance value R3.
Is connected to the power supply 30 of the voltage Vb. Therefore, when the transistor 18 is turned on, a current flows from the power supply 30 to the resistor 39, the wiring 2, the resistor 20, and a circuit that is connected to the ground via the transistor 18, and when the transistor 19 is turned on, the power supply 30 outputs the resistance 39, the wiring 2, and the resistor 21. , A current flows through a circuit to the ground via the transistor 19. Note that the resistance values R1 and R2 of the resistors 20 and 21 are R1 <R2
There is a relationship.

The turning on and off of the transistors 18 and 19 are controlled by the strength of the magnetic field applied to the magnetic sensing elements 16 and 17. When the applied magnetic field increases, the magnetic sensing element 1
When the output voltages of 6 and 17 become high and exceed a predetermined value, the waveform shaping circuits 12 and 13 which have output low-level voltages until now output high levels. The transistors 18 and 19 are turned on when the output signals of the waveform shaping circuits 12 and 13 are at a high level, and are turned off when the output signals are at a low level.

The discriminating unit 3 includes three comparators 31 to 3
3 One input terminal of each of the comparators 31 to 33 is connected to a node 40 which is one end of a resistor 39, and power supplies 34 to 36 having different reference potentials V1 to V3 are connected to the other input terminals. Reference potentials V1 to V
3 have a relationship of V1>V2> V3, and each comparator 3
In 1 to 33, when the voltage of the node 40 exceeds each reference potential, the output signal is at a high level, and at other times, it is at a low level. Output terminal 22 of magnetic detector 1
Is the same potential as the node 40.

Output terminals of the comparators 31 to 33 are connected to input terminals of a CPU (central processing unit) 38 which is a discrimination processing circuit. The output terminal of the comparator 32 is not only directly connected to one input terminal of the CPU 38 but also connected to another input terminal of the CPU 38 via a delay circuit 37.

The CPU 38 determines the rotation direction of the rotor 5 based on the output signals of the comparators 31 to 33 and the output signal of the delay circuit 37 by a first interrupt process and a second interrupt process described later.

FIG. 2 is a layout diagram showing a positional relationship between the magnetic detection unit 1 and a rotor 5 coaxially mounted on a detection target whose rotation direction is to be detected. The rotor 5 is a cylindrical body made of a magnetic material in which grooves 51 and ridges 52 that are parallel to its rotation axis (a direction perpendicular to the drawing) are alternately provided over the entire side peripheral surface. The magnetic detection unit 1 is provided near the side peripheral surface of the rotor 5, and the magnetic sensing elements 16 and 17 are arranged so as to be arranged in the rotation direction of the rotor 5. Also, the magnetic sensing element 16
The permanent magnet 4 is arranged behind the and 17. Therefore, the magnetic sensing elements 16 and 17 are located between the permanent magnet 4 and the rotor 5.

The applied magnetic field to the magnetic sensing elements 16 and 17 becomes strong when it is located between the permanent magnet 4 and the ridge 52, and weak when it is located between the permanent magnet 4 and the groove 51. Therefore, when the detection object (not shown) rotates and the rotor 5 rotates, the periodically changing magnetic fields are applied to the magnetic sensing elements 16 and 17 with different phases.

The magnetic detecting section 1 outputs four-level electric signals corresponding to the applied magnetic field, and the discriminating section 3 detects the rotation direction of the rotor 5 based on the signal from the magnetic detecting section 1, that is, the rotation of the object to be detected. Detect direction.

Next, the operation of this embodiment will be described with reference to FIGS.

FIGS. 3 and 4 show the relationship between the position of the magnetic detector 1 with respect to the groove 51 or the ridge 52 of the rotor 5 and the output signal of the magnetic detector 1, that is, the potential of the output terminal 22, respectively. , FIG. 3 shows forward rotation (the direction of arrow A in FIG. 2).
FIG. 4 shows the case of reverse rotation (the direction of arrow B in FIG. 2).

In the state (1) of FIG. 3, the magnetic sensing element 1
Since both 6 and 17 face the groove 51 and the magnetic fields applied to the magnetic sensing elements 16 and 17 are both weak, the output voltage is low. Therefore, the outputs of the waveform shaping circuits 12 and 13 become low level, and the transistors 18 and 19 are both turned off. At this time, the voltage Vout of the output terminal 22 of the magnetic detection unit 1 becomes the power supply voltage Vb and becomes the highest voltage level, Level 4.

When the rotor 5 rotates in the direction A, (2) in FIG.
Then, the magnetic sensing element 16 faces the ridge 52 while the magnetic sensing element 17 faces the groove 51. In this state, only the magnetic field applied to the magnetic sensing element 16 becomes strong, and the output of the waveform shaping circuit 12 becomes high level.
The transistor 18 turns on. Since the transistor 19 is still in the off state, the resistor 39,
A current path that is grounded via the wiring 2, the resistor 20, and the transistor 18 is formed. At this time, the voltage Vout of the output terminal 22 is given by the following equation: Vout = Vb × (R1 / (R3 + R1)) (1)
This is the second level.

When the rotor 5 further rotates in the direction A and shifts to the state shown in FIG. 3C, the magnetic sensing elements 16 and 17 both face the ridge 52. In this state, the waveform shaping circuit 1
Since both output signals of 2 and 13 are at high level, both transistors 18 and 19 are turned on. Therefore, a current path grounded from the power supply 30 via the resistor 39, the wiring 2, the resistor 20, and the transistor 18 and a current path grounded from the power supply 30 via the resistor 39, the resistor 21, and the transistor 19 are formed. Output terminal 22 at this time
Is given by the following equation: Vout = Vb × (Rc / (R3 + Rc)) (2) where Rc = R1 · R2 / (R1 + R2), and the lowest level among the four output voltage levels It becomes 1.

Further, when the rotor 5 rotates in the same direction as shown in FIG.
In the state (4), the magnetic sensing element 16 faces the groove 51, and the magnetic sensing element 17 faces the ridge 52. In this state, the transistor 18 is off and the transistor 1
9 is turned on, a current path is formed which is grounded from the power supply 30 via the resistor 39, the resistor 21, and the transistor 19, and the voltage Vout of the output terminal 22 is expressed by the following equation: Vout = Vb × (R2 / (R3 + R2 ))... Given by (3), the lower three of the four output voltage levels
The third level.

When the rotor 5 further rotates, the state again becomes the state (1), and thereafter, the same operation is repeated. Therefore, the output voltage of the magnetic detection unit 1 when the rotor 5 is rotating forward is level 4-level 2-level 1-level 3
Is repeated.

Next, the operation when the rotor 5 rotates in the reverse direction will be described with reference to FIG.

The state (1) in FIG. 4 is the same as the state (1) in FIG. 3, and both the magnetic sensing elements 16 and 17 face the groove 51. At this time, the output voltage Vout of the output terminal 2 becomes level 4 as described above. When the rotor 5 rotates in the direction B shown in FIG. 2, a state (2) shown in FIG. 4 is obtained. This state is the same as (4) in FIG. 3, and the output voltage Vout
Becomes level 3. When the rotor 5 further rotates and shifts to the state (3) in FIG. 4, the state becomes the same as the state (3) in FIG. 3, and the output voltage Vout becomes the level 1. When the rotor 5 further rotates and shifts to the state (4) of FIG. 4, the state becomes the same as the state (2) of FIG. 3, and the output voltage Vout becomes the level 3.

As described above, when the rotor 5 is rotating in the reverse direction, the output voltage of the magnetic detector 1 repeats a change of level 4-level 3-level 1-level 2.

The four-stage output voltage signal generated by the magnetic detection unit 1 in this way is
33 and compared with three voltages V1, V2, V3. The voltage V1 is the level 3 of the output signal of the magnetic detection unit 1.
Is set to a value between level 3 and level 4, voltage V2 is set to a value between level 3 and level 2, and voltage V3 is set to a value between level 2 and level 1.

FIG. 5 is a timing chart showing the output signals of the comparators 31 to 33 in association with the output signals of the magnetic detector 1. In the figure, (A) is the output signal of the magnetic detection unit 1, (B) is the output signal of the comparator 31, (C) is the output signal of the comparator 32, (D) is the output signal of the comparator 33, and (E) is The output signal of the delay circuit 37 is shown on the left side when the rotor 5 rotates forward, and on the right side when the rotor 5 rotates reversely.

The CPU 38 receives the signals shown in FIGS. 5B to 5D and determines the rotation direction of the rotor 5 based on the flowcharts shown in FIGS.

FIG. 6 is a flowchart showing a first interrupt process in the CPU 38, in which the rotation direction of the rotor 5 is determined based on the output signal of the comparator 31 and the output signals of the comparator 32 and the delay circuit 37. FIG. 7 is a flowchart showing a second interrupt process in the CPU 38, in which the rotation direction of the rotor 5 is determined based on the output signal of the comparator 33 and the output signals of the comparator 32 and the delay circuit 37.

In the first interrupt processing of FIG. 6, first, it is determined whether or not the output signal (FIG. 5B) of the comparator 31 is at the timing of the falling edge (step 61).
If it is the falling edge timing as at times t3, t7, t11 and t15, the comparator 3
It is determined whether or not the output signal No. 2 (FIG. 5C) is at a low level (step 62). A low level immediately after times t3 and t7 means forward rotation (step 64), and a high level immediately after times t11 and t15 means reverse rotation (step 65).

In step 61, the comparator 31
Of the output signal at times t2, t6, t10, t14
If it is a rising edge as in
And the output of the delay circuit 37 immediately thereafter (see FIG. 5).
(E)) is determined to be at a high level. Time t2, t
If the level is high, as in the case immediately after 6, the rotation is normal (step 66), and if the level is low, the rotation is reverse (step 65).

By the above interrupt processing, the rotation direction of the rotor 5 can be determined at the timing of the output signal edge of the comparator 31.

In the second interrupt process of FIG. 7, it is determined whether or not the output signal of the comparator 33 (FIG. 5D) is at the rising edge timing (step 71). Time t
If the timing is the rising edge as in 1, t5, t9, and t13, it is determined whether or not the output signal (FIG. 5C) of the comparator 32 immediately thereafter is at the high level (step 72). When it is at the high level immediately after the times t1 and t5, it means normal rotation (step 74).
If the level is low as immediately after the times t9 and t13, it means reverse rotation (step 75).

In step 71, the comparator 33
Of the output signal at times t4, t8, t12, and t16
If it is a falling edge as in
And the output of the delay circuit 37 immediately thereafter (see FIG. 5).
(E)) is determined to be at a high level. Time t4, t
If the level is low as in the case immediately after 8, the rotation is normal (step 76), and if the level is high, the rotation is reverse (step 75).

By this interrupt processing, the comparator 3
The rotation direction of the rotor 5 can be determined at the timing of the output signal edge of No. 3.

As described above, the rotation direction of the rotor 5 can be determined at all the changing points of the output signal of the magnetic detection unit 1.

The magnetic detecting section 1 of the present embodiment has a structure in which the magnetic sensing elements 16 and 17 provided with the permanent magnets 4 are arranged in the vicinity of the magnetic rotor 5 rotating coaxially with the object to be detected. The magnetic sensing element 16 according to the rotation of the detection object,
Although the applied magnetic field to the magnetic field 17 is periodically changed, a magnet rotor whose polarity alternates in the circumferential direction is used instead of the magnetic rotor 5 and the permanent magnet 4 behind the magnet is removed. Can be applied to the magnetic sensing elements 16 and 17 periodically changing in accordance with the rotation of the magnetic field.

Although the above description has been made on the determination of the rotation direction, the present embodiment can also detect the rotation speed with high accuracy. That is, in the output waveforms of FIGS. 3 and 4, when the number of rising edges and falling edges of the pulse is counted, four edges can be obtained for the passage of one protrusion, and thus two edges can be obtained. Double edges can be obtained. Therefore, double-precision rotation speed detection can be performed.

[0041]

As described above, according to the rotation direction detection device of the present invention, the rotation direction of the rotating body can be detected by the discrimination unit based on one output signal from the magnetic detection unit. In addition, the connection between the magnetic detection unit and the discrimination unit is simplified, and the usability is good.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a rotation direction detecting device according to an embodiment of the present invention.

FIG. 2 is a layout diagram showing a positional relationship between a magnetic detection unit 1 and a rotor 5.

FIG. 3 is a diagram showing a relationship between a position of a magnetic detection unit 1 with respect to a groove 51 or a ridge 52 during normal rotation of a rotor and an output signal of the magnetic detection unit 1;

FIG. 4 is a diagram showing a relationship between a position of the magnetic detection unit 1 with respect to a groove 51 or a ridge 52 during reverse rotation of the rotor and an output signal of the magnetic detection unit 1;

FIG. 5 is a timing chart showing output signals of comparators 31 to 33 in association with output signals of the magnetic detection unit 1;

FIG. 6 is a flowchart showing a first interrupt process in a CPU 38;

FIG. 7 is a flowchart showing a second interrupt process in the CPU 38;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic detection part, 2 ... Signal line, 3 ... Judgment part, 4 ... Permanent magnet, 5 ... Rotor, 16, 17 ... Magnetic sensing element, 18, 1
9 ... transistor, 20, 21, 39 ... resistor, 31, 3
2, 33: comparator, 37: delay circuit, 38: CP
U.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-227118 (JP, A) JP-A-59-8161 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01D 5/00-5/62 G01P 1/00-3/80 G01P 13/00-13/04 G01B 11/00-11/30 G01B 7/00-7/32

Claims (1)

(57) [Claims] 1. A magnetic detector for dividing one cycle of a change in a periodically applied magnetic field accompanying rotation of a rotating body into four sections and outputting an electric signal of a level corresponding to each section, and an output signal level of the magnetic detector. and a discrimination unit for discriminating a rotational direction of the rotating body based on the change, the magnetic detection unit periodically indicia associated with the rotation of the rotating body
Detect changes in applied magnetic field with their phases shifted from each other, and
Two magnetic sensing elements that convert to electric signals,
Based on the electrical signals output by the magnetic sensing elements,
Two switch means for performing on / off switching, and
Different from each other depending on the on / off state of the two switch means.
Output a signal of any one of the four signal levels
And a rotation direction detecting device.