JPS6360324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an assembly accuracy measuring device that measures the attachment accuracy of a plurality of objects attached along the circumferential direction of a rotating body.

[Technical background of the invention and its problems]

In a VTR, two heads are attached to a rotating disk at a 180 degree angle, and screen signals are extracted by running these heads over a magnetic tape. Therefore, unless it is mounted at a precise 180 degree angle in the circumferential direction of the disk,
This will cause the image on the TV screen to shift.
In the VTR assembly process, it is extremely important to inspect the assembly accuracy of the head to the disk.

Conventionally, in order to inspect the assembly accuracy of the head relative to the disk, a pair of microscopes is placed at exactly 180 degrees to the rotation axis of the disk, and a pair of microscopes is placed on the end face of each head to be magnified by each microscope. Whether each head was assembled to the disk at a precise angle of 180 degrees was determined by whether the slit section was located at the center of the field of view of each microscope.

However, according to such measurement means,
Accurately aligning the optical axes of a pair of microscopes with the center of the rotational axis of the disk and arranging them at 180-degree opposing angles not only requires a great deal of effort, but also tends to cause errors, and it is also necessary to adjust the focus during measurement. In addition, it is necessary to look through a pair of microscopes, which is extremely inefficient. Moreover, since measurements made using a microscope are made by the person measuring them visually, there are variations in the criteria for judgment, and there is a limit to the improvement of measurement accuracy.

Therefore, a laser beam is incident on the head that rotates with the disk, and the laser beam scattered from the slit on the end face of the head is received by two sensors connected to a differential amplifier, and a signal is output from the differential amplifier. The time from the zero cross point of one head to the zero cross point of the other head is compared with the time from the zero cross point of the other head to the zero cross point where the first head is detected again. A device has been proposed that requires an assembly accuracy of 180 degrees.

However, such a device has the problem that accurate assembly accuracy cannot be obtained unless the disk is rotated very stably. This is because when measuring the assembly accuracy of a VTR head, the rotational speed of the disk is generally 16.7 m/s, and the measurement error must be less than 0.1 μ/s due to the head assembly tolerance. Rotation is also 6.0×
A stability of 10 ^-6 is required, but it is extremely difficult with current technology to rotate the disk with such high stability. Moreover, with the above-mentioned apparatus, measurement cannot be carried out without waiting for a long time until the rotation of the disk becomes stable.

[Purpose of the invention]

This invention was made in view of the above circumstances, and its purpose is to provide an assembly accuracy measuring device that can obtain assembly accuracy of each object without requiring highly stable rotation of a rotating body. There is a particular thing.

[Summary of the invention]

This invention corrects changes in the rotational speed of the rotation means for rotating the object to be measured, and calculates the amount of deviation in the mounting angle between any two objects, thereby eliminating the influence of rotational fluctuations. The objective is to find the amount of deviation between the mounting angles of two arbitrary objects.

[Embodiments of the invention]

The present invention will be described below based on an embodiment shown in the drawings. In the figure, numeral 1 indicates a VTR disk which is a disc-shaped rotating body. This disk 1
A rotating shaft 2 is provided at the center of the disk 1, and two heads 3a and 3b are provided as objects at the periphery of the upper surface so as to form an angle of 180 degrees in the circumferential direction of the disk 1. As shown in FIG. 2, these heads 3a and 3b have a substantially semicylindrical shape with one end surface curved, and the curved surface protruding from the outer peripheral surface of the disk 1 has a slit portion as a scattering portion along the thickness direction. 4 are provided.

The disk 1, which is the object to be measured, has the heads 3a and 3b assembled in this way.
is supported by a support (not shown) and rotationally driven by a motor 15, and the measuring device 5 determines whether or not the pair of heads 3a, 3b are precisely provided at an angle of 180 degrees in the circumferential direction of the disk 1. measured. This measuring device 5 is configured as follows. That is, the disks 3a, 3b that are rotationally driven together with the disk 1 have heads 3a, 3b.
Laser light L output from the laser oscillator 6 is focused by the first lens 6a and sequentially irradiated onto the curved surface of the laser beam 3b at a predetermined angle of incidence. Heads 3a, 3b
The laser beam irradiated on the curved surface is normally reflected specularly by the curved surface, but is scattered at the slit portion 4.
The specularly reflected light L1 from the curved surface hits the light shielding plate 7 arranged in this reflection direction and is absorbed, and the scattered light _L2 is focused by the second lens 8 arranged in this scattering direction and is sent to the spatial filter 9. Head over. This spatial filter 9 is provided with an elongated through hole 10 in a direction perpendicular to the slit portion 4 . Therefore, only the scattered light _L2 passes through the through hole 10. In addition, at the position where the scattered light L ₂ that has passed through the through hole 10 forms an image of the slit portion 4, a first sensor 11 and a second sensor 12 composed of photodetectors are arranged side by side with a slight distance between them. has been done. Therefore, the image of the slit portion 4 due to the scattered light _L2 is not only reflected on the disk 1 but also on the heads 3a and 3b.
By rotating, it is detected by the first sensor 11 and then detected by the second sensor 12. Of these sensors 11 and 12, the first sensor 11 is connected to the non-inverting input terminal of the differential amplifier 13, and the second sensor is connected to the inverting input terminal of the differential amplifier 13. The output from the first sensor 11 by the amplifier 13
The difference between E ₁ and the output E ₂ from the second sensor 12 is calculated. The output from the differential amplifier 13 is then input to the arithmetic circuit 14. In the arithmetic circuit 14, the output E ₁ from the first sensor 11
and the output E2 from the second sensor ₁₂ to detect the period of the zero cross point, and
The amount of deviation in the mutual mounting angles of the heads 3a and 3b is calculated from the average rate of the cycle time between zero crossing points with respect to the rotation of the head. That is,
After rotating the disk 1 a predetermined number of times (n≧2) or more and starting the measurement using the laser beam L, the zero cross point corresponding to the head 3a, which is performed at the i-th rotation, corresponds to the head 3b after another half rotation. Let T ₁ ⁱ be the cycle time until the zero crossing point appears,
Further, when the cycle time until the disk 1 rotates half a rotation and the zero cross point corresponding to the head 3a appears again is T ₂ ⁱ , the mutual deviation amount Δθ of the heads 3a and 3b is: By digitally calculating the difference between the heads 3a and 3b, it is possible to detect the mutual deviation between the heads 3a and 3b in a state where it is least affected by fluctuations in the rotational speed of the disk 1. The result of this deviation amount is displayed on a display unit (not shown) built into the arithmetic circuit 14. Note that in the above equation, k is a conversion constant for converting a time difference into an angular difference.

Next, the operation of the measuring device 5 configured as described above will be explained. First, the disk 1 is rotated and the laser oscillator 6 is activated to emit a laser beam L.
When this laser beam L is outputted, the curved surfaces of the pair of heads 3a and 3b rotating together with the disk 1 are sequentially irradiated with the laser beam L. When the laser beam L irradiates the curved surface of one head 3a, the laser beam L is specularly reflected at a portion other than the slit portion 4, so that the specularly reflected light _L1 hits the light shielding plate 7 and is absorbed. However, when the laser beam L irradiates the slit portion 4, it is scattered by the slit portion 4, so this scattered light _L2 is focused by the second lens 8 and passes through the through hole 10 of the spatial filter 9. The scattered light L ₂ that formed the image of the slit portion 4 is
As the head 3a rotates together with the disk 1, the first sensor 1 is rotated as shown by the arrow in FIG.
1 to the second sensor 12 and is detected by these sensors 11 and 12. Therefore, the difference ΔE between the output E ₁ of the first sensor 11 and the output E ₂ of the second sensor 12 in the differential amplifier 13 is reversed from positive to negative as shown in FIG. Then, the moment when the scattered light L ₂ forming the image of the slit portion 4 transfers from the first sensor 11 to the second sensor 12 becomes the zero cross point Z ₁ ¹ , and when this zero cross point Z ₁ ¹ occurs The time is stored in the arithmetic circuit 14.

Then, by rotating disk 1 by half a rotation,
Scattered light from the slit portion 4 of the other head 3b
L ₂ is detected by the first and second sensors 11 and 12, and the zero crossing point Z ₂ ¹ at this time is calculated by the differential amplifier 13 in the same way as before. and,
The time T 1 1 from when the previous zero-crossing point Z ₁ ¹ is detected to when _the next zero-crossing point Z ₂ ^{1 is} detected is stored in the arithmetic circuit 14 .

Furthermore, by rotating the disk 1 by half a rotation,
Scattered light L ₂ from the slit portion 4 of the head 3a again
is detected by the first and second sensors 11 and 12, and the zero-crossing point Z ₁ ² at this time is calculated again by the differential amplifier 13. The time T 2 1 from when the zero cross point Z ₂ ¹ of the head 3b is calculated to when _the current zero cross point Z ₁ ^{2 is} calculated is stored in the calculation circuit 14.

Then, by comparing the time T ₁ ¹ and the time T ₂ ¹ obtained in this way, the deviation of the opposing angle (180 degrees) between the two slit parts 4, 4 can be obtained. Obtaining the amount of deviation by comparing the period times of the two requires high stability of disk 1, which is technically difficult, and accuracy can only be obtained by comparing the first half rotation and the second half rotation. disk 1
If the rotational speed of the motor changes, an error will occur in the measurement.

However, in this invention, by using the arithmetic circuit 14 that corrects the variation in the rotational speed of the disk 1 and calculates the amount of deviation in mounting angle between the heads 3a and 3b, highly stable rotation of the disk 1 is not required. Accurate assembly precision of the heads 3a and 3b can be obtained.

To explain this point in detail, when the rotation speed of the disk monotonically increases or decreases, the rotation of the disk 1 described above enters the second rotation, and the zero cross point corresponding to the slit portion 4 of the head 3b is reached again. By obtaining the time T ₁ ² until Z ₂ ² appears; and performing the digital calculation Δθ=k×(T ₁ ¹ −T ₂ ¹ )−(T ₂ ¹ −T ₁ ² )/2, the disk 1 The changes in rotational speed are canceled out, and an accurate facing angle deviation amount Δθ for 180 degrees can be obtained. However, k
is a conversion constant for converting a time difference into an angular difference.

In addition, when the rotational speed of disk 1 fluctuates in a single time period, by rotating disk 1 n times (n≧2) and calculating the simple average of T ₁ - T ₂ using the following formula, the opposing angle deviation amount Δθ can be obtained accurately. It will be done.

Δθ=k× _o 〓 ^m=K − ^N (T ₁ ⁱ −T ₂ ⁱ ) However, in the case of a drive such as a general motor that rotates in a complicated manner by combining the above-mentioned changing states, the above two equations are The opposing angle deviation amount Δθ is programmed in the arithmetic circuit 14. By performing the following calculation from the signal from the differential amplifier 13, the pair of heads 3a and 3b assembled on the disk 1 can be accurately aligned at an angle of 180 degrees (opposing angle).
If it is set, Δθ=0, so
The arithmetic circuit 14 calculates the average rate (correction) of the periodic time for the rotation of the disk 1, so that even if the rotational speed of the disk 1 changes, the assembly precision of the pair of heads 3a and 3b can be determined with high accuracy. become. The result of this calculation is then displayed on a display section (not shown).

In addition, in the above-mentioned embodiment, a case was described in which two heads were assembled as objects on a disk, which is a rotating body, but the present invention can be widely applied not only to VTR heads but also to a wide range of installation measurements of parts attached to a rotating body. Furthermore, even if there are an even number of objects such as four or more, the amount of deviation of the objects between two points can be measured in the same way as in the first embodiment by skipping one point and measuring.

〔Effect of the invention〕

As explained above, according to the present invention, even if the rotational speed of the rotating body changes, it is possible to determine the amount of deviation in the mounting angle between the objects without being affected by the fluctuation in rotation, resulting in high stability. The assembly accuracy of each object can be measured without the need for rotating a rotating body. Furthermore, since accurate measurements can be made even if the rotational speed of the rotating body changes, measurements can be made immediately after the rotation starts. Moreover, the calculation formula to be processed is simple, so the calculation circuit is simple.
It also has the advantage of being simple.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is a schematic configuration diagram of an assembly accuracy measuring device, Fig. 2 is a perspective view of the head, which is an object, and Fig. 3 is a A front view showing a state in which laser light from an object is detected, and FIG. 4 is a diagram showing arithmetic signals output from a differential amplifier. 1... Disk (rotating body), 3a, 3b... Head (object), 4... Slit part (scattering part), 6...
...Laser oscillator, 11...First sensor, 12...
...Second sensor, 13...Differential amplifier, 14...
Arithmetic circuit, 15...Motor (rotating means), L...
Laser light, L ₁ ... specularly reflected light, L ₂ ... scattered light.

Claims (1)

[Claims] 1. An assembly accuracy measuring device for measuring the assembly accuracy between any two objects to be measured, in which a plurality of objects each having a scattering section are attached along the circumferential direction of a rotating body. , means for supporting and rotating the object to be measured; a laser oscillator for irradiating a laser beam onto a certain position of the object rotated by the rotating means; a first sensor and a second sensor arranged in parallel at a position to detect laser light scattered by the sensor; a differential amplifier into which output signals from these sensors are input; and a predetermined object to be measured from this differential amplifier. Detect first and second output signals corresponding to the first and second objects, which are arbitrary two of the objects mentioned above, when rotated at least n times (n≧2), and from the start of this measurement. , period time T 1 i from the zero-crossing point of the first output signal of the i-th rotation to the zero-crossing point of the second output signal, period time T ₁ ⁱ of the zero-crossing point of the second output signal of the i-th rotation to the first output signal. When the cycle time is T ₂ ⁱ , An assembly accuracy measuring device characterized by comprising: a calculation circuit for calculating the amount of deviation between two objects.