JPH0367122A - Rotational angle detecting device - Google Patents

Abstract

PURPOSE:To simplify the structure and to reduce the cost by providing a scale which has small pitch and equal intervals, and two noncontact type sensors which detect blank parts formed at large intervals. CONSTITUTION:The outer peripheral surface of a rotary body 1 is divided into an upper half scale formation area 1b and a lower half gear part 1c, and a cam driving gear 2 is engaged with the gear part 1c. Further, the scale 4 is formed in the area 1b at equal intervals of 1 deg. in a range of 0-270 deg. while matching the center angle of a cam groove 1a. Further, the blank parts E1-E4 which differ in circumferential width are formed in the area 1b at four places which are formed at intervals of 90 deg.. Then the absolute rotational angle of the rotary body 1 can be known by judging which of 1st and 2nd sensors 5a and 5b detect the blank parts E1-E4 and also judging how many graduations of the scale 4 are detected by a sensor different from the sensor detecting the blank parts.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to controlling the rotation angle of a rotating body in order to control the rotation of the rotating body or to control the operation of a movable part that is linked to the rotating body. It relates to a device for detecting.

The rotation angle detection device of the present invention is suitable for detecting the rotation angle of a cam as a rotating body, and for detecting a VT that needs to detect a minute rotation angle.
Suitable for detecting the rotation angle of R loading cam, etc.
It is not limited to this.

<Conventional technology> Below, the loading cam of a VTR is given as a representative example.
The rotation angle detection device will be explained.

A typical conventional cam rotation angle detection device is of a contact type.

That is, as shown in FIG. 7, the cam drive gear 2 is engaged with the teeth on the outer peripheral surface of the rotor 1 in which the cam groove 1a is formed (the teeth of the rotor 1 and the teeth of the cam drive gear 2). (not shown), a rotary switch 3 is attached to the teeth of the rotating body 1.
The passive gear 3a is engaged with the passive gear 3a. The rotary switch 3 includes a large number of switches that are sequentially switched as the passive gear 3a rotates.

The cam drive gear 2 is driven to rotate the cam grooved rotary body 1, and in conjunction with the rotation of the rotary body 1, the passive gear 3a is rotated, and the switch groups inside the rotary switch 3 are switched one after another. The rotation angle of the rotating body 1 with cam grooves is detected by this mechanical method.

There is also a non-contact type cam rotation angle detection device as shown in FIG. 8, although it is rarely used. This is done by attaching scales 4 (detailed illustrations are omitted) at equal intervals at a relatively small angle (for example, l") using paint or a magnetic film on the outer circumferential surface of the rotor 1 with cam grooves, and at the same time markings 4 (detailed illustrations are omitted). The rotation of the rotating body 1 is determined by installing one optical or magnetic sensor 5 in the rotation body 1 and counting the scale marks 4 detected by the sensor 5 one by one with a counter (not shown) as the rotating body 1 rotates. It detects corners.

The count increases by 1 each time a scale 4 is detected when the rotating body 1 at the origin position rotates in the forward direction, and counts up by 1 each time a scale 4 is detected when rotating in the reverse direction. The count value (rotation angle) is updated in RAM (not shown). To know the current rotation angle of the rotating body l,
All you have to do is read the count value from .

<Problems to be Solved by the Invention> (A) The contact type cam rotation angle detection device shown in FIG. 7 has the following problems.

That is, the structure of the rotary switch 3 is complicated, leading to an increase in cost, and the space occupied by the rotary switch 3 is large, leading to an increase in the size of the device. Also,
The passive gear 3a of the low grease inch 3 contacts the rotating body l (
(meshing), it becomes a load when the rotating body 1 rotates, and torque loss cannot be avoided.

(B) Although the non-contact type cam rotation angle detection device shown in FIG. 8 has a relatively simple structure and is advantageous in terms of space, and there is no torque loss, it has the following problems.

■ The pitch of scale 4 is relatively small (1'),
Since the scale 4 is detected one by one, and there is a certain limit to the responsiveness of the sensor 5 and counter,
The rotating body 1 cannot be rotated at high speed.

■ Since the width of each scale 4 is small, the scale 4 may become thin or chipped when applying paint or magnetic film to attach the scale 4, or with continued use. It may be missed. If there are a plurality of such missed marks 4, the number of missed marks increases as the amount of rotation increases, and the error in the detected rotation angle increases.

Also, when reading errors occur due to noise,
I have a similar problem.

■ If the RAM does not have a bank-up power supply, if the power plug is unplugged from the outlet or a power outage occurs, the count value (rotation angle) stored in the RAM will be saved.
is cleared, and even if the power is restored, the current rotation angle of the rotating body 1 cannot be determined. When the rotating body 1 is rotated in this state, the angle of rotation can be determined by the count on the scale 4, but this is only a relative rotation angle and not an absolute rotation angle from the origin position.

Since the absolute rotation angle is important for controlling the rotation of the rotating body 1, if the above situation occurs, the desired rotation control will become impossible.

In order to detect the absolute rotation angle after the power is restored, the rotating body 1 must be returned to the home position for -1 time, but the larger the rotation angle when the power is turned off, the longer it takes to return to the home position. It takes.

If the RAM is provided with a bank amplifier power supply, this problem will not occur, but it will increase the cost.

In view of such circumstances, the present invention aims to eliminate the above-mentioned disadvantages found in the conventional example.

<Means for Solving the Problems> In the rotation angle detection device of the present invention, scales are formed on the rotary body at equal intervals with a relatively small pitch on an arc around the rotation center of the rotary body, and in the scale forming area. Blank areas without scales are formed at a plurality of locations separated by relatively large intervals, the widths of the plurality of blank areas are different from each other, and at least two sensors for detecting the scales and the blank areas are provided. It is characterized in that the non-contact sensors are provided at different positions.

Effect〉 The effects of the above configuration of the present invention are as follows.

■ When a blank area is detected by one non-contact sensor, the number of scale marks detected by the other non-contact sensor is, because the width of the blank area is different from each other.
It differs depending on which blank area is detected by the one non-contact type sensor.

@ When the detected blank area is detected by the other non-contact sensor as the rotating body rotates, the number of scales detected by the one non-contact sensor is
The number is the same as in the case of . However, this is different from the case (2) in which the non-contact sensor detecting the blank area is used.

From ■ and @ above O, determine which non-contact sensor detected the blank area [summer], and which non-contact sensor other than the non-contact sensor that detected the blank area when it was detected. Judgment of how many scale marks the sensor has detected (n)
From this, it is possible to know the absolute rotation angle of the rotating body from its origin position to its blank area detection position.

In other words, the absolute rotation angle is uniquely determined based on the AND condition of conditions (1) and (II).

0 The position of the target absolute rotation angle of the rotating body may be the blank portion detection position or may be another position. In the former case, predetermined control such as stopping the rotating body at the blank detection position may be performed.

In the latter case, the rotating body is moved at the position where the number of scale marks corresponding to the angle difference between the blank detection position (the absolute rotation angle at this position is known) and the target absolute rotation angle is detected. Predetermined control such as stopping may be performed.

(2) By integrating the above (2) to (2), it becomes possible to control the rotation based on the following rotation angle detection method.

That is, the rotating body is rotated at high speed until a blank portion is detected at a rotation angle closest to the target absolute rotation angle, which is to be detected by the non-contact sensor. Since the width of the blank area is sufficiently larger than one scale, it is possible to detect the blank area even if the rotating body is rotated at high speed. In this high-speed rotation, the purpose is to detect blank areas, and there is no need to detect scales with small pitches one by one as in the conventional example.

After the rotating body detects the blank area, it is sufficient to rotate the scale from that position to the target absolute rotation angle while moving the scale one by one.

Therefore, the overall rotation up to the target absolute rotation angle can be achieved at high speed.

○ Even if a reading error occurs due to a missing scale or noise, and an error occurs in the detected absolute rotation angle, it is possible to confirm the absolute rotation angle that is uniquely determined by the detection position of the blank area. Therefore, it is relatively easy to correct the detection angle error at the blank portion detection position.

■ Due to disconnection of the 2B plug or power outage, the RA
Count if stored in M! , (rotation angle) is cleared and the current absolute rotation angle is no longer known, there is no need to return the rotating body to the origin position by a large distance after the power is restored, as in the conventional example.

In the same sense as the origin position, the absolute rotation angle of a blank area is uniquely determined, so by returning from the current rotation position to the closest blank area, you can quickly return to a state where the absolute rotation angle is known. I can do it.

Therefore, a backup power source for the RAM is not required, and costs can be reduced accordingly.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a plan view of the main parts of the rotation angle detection device, and FIG. 2 is a side view thereof.

The outer peripheral surface of the disc-shaped rotating body 1 in which the cam groove 1a is formed,
It is divided into a smooth scale forming area 1b in the upper half and a gear part IC in which teeth are formed in the lower half. A cam drive gear 2 is meshed with the gear portion 1c of the rotary body 1 with cam grooves. Further, in the scale forming area 1b, scales 4 are formed at equal intervals of 1@ by applying paint in a range of 0 to 270 degrees in accordance with the central angle of the cam groove 1a.

Scale 4 is a repeating pattern of white and black.
One black and white pattern has an angle of 1°, 0.5
The black part of " is the scale 4. Since the scale 4 is formed in the scale forming area 1b of the circular arc, it is formed on the circular arc around the rotation center of the rotating body 1.

In the scale forming area 1b, the scale 4 is not formed in the entire range, but first to fourth blank parts E1 to E4 without a hundred marks are formed at four locations separated by 90 degrees. These four blank parts E1 to E4 have different widths in the circumferential direction.

That is, the width of the first blank area El is the width of 3 black and white patterns for scale 4, the width of the second blank area E2 is the width of 5 black and white patterns, the width of the third blank area E3 is the width of 7 black and white patterns, and the width of the third blank area E3 is the width of 7 black and white patterns. The width of the blank part E4 of No. 4 is nine spaces.

When the scale forming area 1b is developed and shown in a plane, it becomes as shown in FIG.

FIG. 1 shows a state in which the cam grooved rotating body l is at the origin position (0'), and in this state, the radially outer position of the first blank part El, First and second non-contact type sensors 5a, 5b of optical light emitting/receiving type are installed at the outer radial position exactly in the middle of the blank area E4 (45° from the origin position in the rotational direction). are arranged at a short distance from the rotating body 1. Both of these non-contact type sensors 5a and 5b have a scale 4 and a blank area E1 to
This detects E4.

The following table shows the absolute rotation angle of the rotating body 1 every 45' (range of 0 to 270°) and the results of both non-contact types when the rotating body 1 rotates to the position of each absolute rotation angle. Sensor 5a
, 5b is summarized.

Table [Absolute rotation angle and output of both sensors] For example, when the absolute rotation angle is O'' of the magnetic field, the first sensor 5a detects the first blank area El, and the second sensor 5b
is in a state where three scale marks 4 are detected. Further, when the absolute rotation angle is 45' of floor (2), the second sensor 5b detects the first blank area El, and the first sensor 5a detects three scale marks 4.

When the absolute rotation angle is 90", the first sensor 5a
detects the second blank part E2, the second sensor 5b detects five scale marks 4, and when the absolute rotation angle is 135@, the second sensor 5b detects the second blank part E2. , and the first sensor 5a is in a state where it detects five scale marks 4.

Conversely, when a certain blank area is detected by the first sensor 5a, the scale 4 detected by the second sensor 5b
For example, if the number of blank spaces is 7 (Hiro), then the blank space is the third blank space E3, and it can be seen that the absolute rotation angle of the rotating body 1 at this time is 180'.

In this case, if the number of scale marks 4 detected by the second sensor 5b is 9, the blank part is the fourth blank part E4, and the absolute value of the rotating body 1 at that time is 9. It can be seen that the rotation angle is 270@.

Further, when a certain blank part is detected by the second sensor 5b, if the number of scale marks 4 detected by the first sensor 5a is 7 fish (■), the blank part is replaced by a third blank part. part E3, and the absolute rotation angle of the rotating body 1 at that time is 2
It turns out that the angle is 25°.

In this way, the blank part is the first. Second sensor 5a.

5b, by determining which sensor detected the blank area (1), and determining how many scale marks 4 were detected by a sensor different from the sensor that detected the blank area (IT). , the absolute rotation angle of the rotating body l can be known, and the absolute rotation angle is uniquely determined.

FIG. 4 is a schematic system configuration diagram of the rotation angle detection device.

1st. The detection signals of the second sensors 5a and 5b and the absolute rotation angle target value θ. bJ signal is manually input to the control circuit 6. The control circuit 6 performs a predetermined calculation based on the detection signals of both sensors 5a and 5b to determine the current absolute rotation angle θ of the rotating body 1.
, is updated and stored in the RAM 7, and the current absolute rotation angle θ is set to the absolute rotation angle target value θ.
. A drive signal is outputted to the motor 8 that drives the cam drive gear 2 via the amplifier circuit 9 until .

Below, more detailed operation will be explained based on FIG. 1, FIG. 5, and FIG. 6.

It is assumed that the rotating body 1 is rotated from the origin position O'' shown in FIG. 1 to 100@.

By 100', the blank space is detected by the sensor twice. That is, when the first blank part El of Nu ■ is detected by the second sensor 5b (45@), and when the second blank part E2 of Hiro ■ is detected by the first sensor 5a (90 °). The blank portion is detected at the rotation angle closest to ioo' at rotation position 906. This rotation angle of 90'' is calculated by the control circuit 6.

Therefore, the control circuit 6 ignores 456 in the middle,
A high voltage is output to the amplifier circuit 9 so that the rotating body l is once rotated at high speed up to 90 degrees.

To rotate to 90 degrees and stop, do the following (5th
(see figure).

That is, the target point 90' corresponds to when the first sensor 5a detects a blank area (second blank area E2) and the second sensor 5b detects five scale marks 4.

Both the first sensor 5a and the second sensor 5b display "12', "H', "L", "H", etc. until they detect a blank area.
The control circuit 6 inverts the first
When the sensor 5a detects the white part of the black and white pattern, "
From the state where the “L” signal and the “H” signal when the black area is detected are repeated as “L”, “H”, “L”, “■4”, etc., the blank area is detected. First, it is determined that the detection signal has started to be detected and that the detection signal has become continuous as “1,” “L”, “L”, etc., and from the point when “L” starts to occur continuously, Counting of the number of times the second sensor 5b becomes @H'' is started.

Then, when the number of counts until the first sensor 5a changes from the continuous "L" state to "H" reaches the target number of five, the output from the control circuit 6 to the amplifier circuit 9 is stopped. Then, the rotation of the rotating body 1 is stopped. Now, as shown in FIG. 5, it is temporarily stopped at the 90'' position.

After stopping the rotating body 1 at 90°, immediately turn the rotating body 1 again.
Rotate at low speed. At this time, the output voltage from the control circuit 6 to the amplifier circuit 9 is made low. Since the distance from 90° to 1006 is 106, the rotary body 1 continues to rotate at low speed until the second sensor 5b counts 10 "H"s, and stops the rotating body 1 when it counts 10 times.

As a result, as shown in FIG. 6, the rotating body 1 is moved to the absolute rotational angle target value θ. It can rotate and stop up to bJ=100a. Further, the control circuit 6 stores the result of adding 106 to 906, 1006, in the RAM 7 as the absolute rotation angle θ.

Note that the target value θ. When bj is exactly 90'', there is no need for low-speed rotation. Also, when the target value θ.
It is sufficient to stop the rotating body 1 when the count is down.

In addition, if the center (third) of the five scale marks 4 is set to 90'', strictly speaking, the absolute rotation angle θ of the rotating body 1 when the number of counts reaches five is 1 Since the scale is 1 degree, we count the fourth and fifth points from the center scale, so we add 26 and get 92 degrees.

Therefore, in the above explanation, 90'' is 92'',
10 degrees can be interpreted as 8'' and 4 as 6. When the target values θ and J are exactly 90'', the rotation is reversed by 2''.

As another example, a case of rotation from 1006 to 210' will be explained.

The blank space at the rotation angle closest to 210' is detected at the 225 degree rotational position of M■. The control circuit 6 outputs a high voltage so that the rotating body 1 is once rotated at a high speed of 225', ignoring the intermediate 135'' and 180''. This corresponds to when a blank portion (third blank portion E3) is detected and seven scale marks 4 are detected by the first sensor 5a.

The control circuit 6 is configured such that the second sensor 5b is 1L""H","L"
","H", etc. are repeated, then a blank section is detected. First, it is determined that the detection signal has become a continuous state of "L", and when "L" From the point in time when the sequence starts, counting of the number of times the first sensor 5a becomes "H" is started.

Then, when the number of counts until the second sensor 5b changes from the continuous "L" state to "H" reaches seven, the rotation of the rotating body 1 is stopped. Now 225
' It will stop once at the position.

After stopping the rotating body 1 at 225', the rotating body 1 is immediately rotated again at low speed in the opposite direction. At this time, the control circuit 6
The output voltage from the Since the angle from 225° to 210° is 15@, the first sensor 5a detects "H" at 15@.
The rotating body 1 continues to rotate at a low speed in reverse until it counts 15 pieces, and then stops the rotating body 1 when 15 pieces are counted.

As a result, the rotating body 1 is set to the absolute rotation angle target value θ−bJ
= Can rotate up to 210' and stop. Further, the control circuit 6 stores the result of subtracting 15'' from 2256, 2106, in the RAM 7 as the absolute rotation angle θ1.

In addition, if the center (4th) of the 7 scales 4 is set to 225°, strictly speaking, the absolute rotation angle θt of the rotating body I when the number of counts reaches 7 is 2296. be.

Therefore, in the above explanation, 225'' is 229
You can read @, 15'' as 19'', and 15 pieces as 19 pieces.

By the way, when rotating from 210' to 215', read 210° from RAM 7 and set it as the target value θ. , J.
= 215° and find the difference 56. Then, while rotating the rotating body 1 in the forward direction at a low speed, the rotation may be stopped when the count number of the first sensor 5a (or the second sensor 5b) increases by 5.

If the contents of the RAM 7 are cleared due to a power outage, etc., the current absolute rotation angle θ of the rotating body 1 will not be known, but it will be found first after the power is restored and the rotating body 1 is rotated forward or reverse. Stop at a blank space.

The blank space is the first. Depending on which sensor among the second sensors 5a and 5b detected the blank area and how many scale marks 4 were detected by a sensor other than the one that detected the blank area, the blank area is determined based on the table above. It is possible to know the absolute rotation angle θ of the rotating body 1 when it is stopped at .

There is no need to return to the origin position as in the conventional example.

However, if the rotational position at the time of power outage is close to the original position, it may return to the original position.

The present invention also includes the following configuration as an example.

(i) The pitch of scale 4 may be arbitrarily selected other than 1''.

(ii) The pitch and number of blank parts are arbitrary.

(iii) The number of scale marks corresponding to the blank area is not limited to an odd number, but may be an even number, or may be increased by one.

(1v) Although the scale forming area 1b is formed on the outer peripheral surface of the rotating body 1, it may be formed on the surface of the rotating body 1.

(v) A magnetic sensor may be used as the non-contact sensor. In this case, the scale is made of magnetic film.

(vl) The number of non-contact sensors does not need to be limited to two,
It can be implemented even if there are three or more.

(vj) The present invention is not limited to detecting the rotation angle of a cam, but can be widely used to detect the rotation angle of a general rotating body.

<Effect of the invention> According to the present invention, the following effects are achieved.

■ Since it is a non-contact detection method, the structure is relatively simple and space-saving, and there is no torque loss.

■ Determining which non-contact sensor detected the blank area (1) and how many scale marks were detected by a non-contact sensor other than the one that detected the blank area when the blank area was detected. Based on the determination CI+), it is possible to know the absolute rotation angle of the rotating body from the origin position to the blank detection position. In other words, condition (1)
, C11), the absolute rotation angle can be uniquely determined based on the AND condition.

Therefore, the blank area will be detected at the rotation angle closest to the target absolute rotation angle.The rotating body is rotated at high speed until the blank area is detected (the width of the blank area is smaller than one scale). (Since the scale is large, blank areas will not be missed even when rotating at high speed.) After that, all you have to do is rotate the scale to the target absolute rotation angle while detecting the scale one by one.
Overall, high-speed operation is possible.

■ Even if errors occur in the detected absolute rotation angle due to missing readings or noise,
By confirming the absolute rotation angle that is uniquely determined at the detection position of the blank area, the detection angle error can be easily corrected.

■ If the power plug is unplugged or a power outage occurs, the RAM
If the volatile memory such as It is possible to quickly return to a state in which the target rotation angle can be determined. In addition, it is possible to eliminate the need for a power supply for volatile memory, thereby reducing costs.

[Brief explanation of drawings]

1 to 6 relate to an embodiment of the present invention, in which FIG. 1 is a plan view of the main parts of the rotation angle detection device, FIG. 2 is a side view thereof, and FIG. 3 is a diagram of the scale-shaped Ifi pJl area. 4 is a schematic system configuration of the rotation angle detecting device. FIG. 3 is a developed view of the scale forming area. FIG. 4 is a plan view of the angle detecting device.

Claims (1)

[Claims] (1) Scales are formed on the rotary body at equal intervals with a relatively small pitch on an arc around the rotation center of the rotary body, and in the scale formation area, there are blank areas without scales at multiple locations separated by relatively large intervals. are formed, the widths of the plurality of blank parts are configured to be different from each other, and at least two non-contact sensors for detecting the scale and the blank part are provided at different positions. Rotation angle detection device.