JPH0130402B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a linear gauge, a tactile roller type, or a spatial filter type length measuring device to generate a distance pulse at every minute pitch length, and then calculates the distance by multiplying the number of generated pulses by the pitch length. The present invention relates to a method for measuring the pitch length between distance pulses at a given temperature in a device that calculates distance pulses.

This type of device depends on the number of distance pulses generated.
The moving distance or length is calculated by multiplying the pitch length (hereinafter simply referred to as pitch), and the pitch is a value actually measured at a certain predetermined temperature.

Therefore, when the temperature changes, the distance pulse generator, that is, the slit plate in a linear gauge, and the roll connected to the pulse generator in a touch roller type, changes due to thermal expansion.
As a result, the pitch naturally changes, causing an error in the calculated value of the moving distance, and especially when the moving distance is long, this error becomes large enough to not be ignored.

To find the pitch when the temperature changes like this, measure the temperature at that time, find the difference from the predetermined temperature, and then multiply the pitch actually measured at the predetermined temperature by the linear expansion coefficient of the distance pulse generator. , and further multiplying by the temperature difference to obtain the change in pitch. However, it is difficult to measure the temperature of parts that change temperature. For example, linear gauges have a scale made of glass and may break if they come into contact with it, and tatsuchi rollers that are used in hot environments are extremely difficult to measure the roller temperature. . Therefore, the pitch change is determined based on the temperature in the vicinity, but it is inevitable that the pitch change will be inaccurate.

Therefore, to consider the pitch measurement method from a different perspective, if we set a test section of an appropriate length and measure the number of distance pulses generated corresponding to the movement of the length of that section, it is possible to The temperature can be calculated from this change in the number of distance pulses, and the changed pitch can then be determined.

The present invention aims to provide a method of determining pitch through temperature calculation based on the number of distance pulses generated during a verification interval, without measuring temperature.

Hereinafter, the present invention will be explained in detail by taking a linear gauge as an example.

In FIG. 1, the linear gauge supports a spindle 1 in a housing 2 so as to be movable upward and downward, the lower part of the spindle 1 protrudes below the housing 2, and the spindle 1 is supported inside the housing 2. Move to slit plate 3
The light-receiving element 5 and the light source 6 are fixed to the inner wall of the housing 2 in a state where they are sandwiched and facing each other, and a fixing slit and a plate 4 are fixed to the opposing surface of the light-receiving element 5. When the spindle 1 moves, the moving slit plate 3 also moves together with it, and the light source 6
The amount of light introduced into the light-receiving element 5 changes periodically for each slit pitch, and a distance pulse is generated in the light-receiving element 5 every time the slit moves one pitch. Therefore, by measuring the number of distance pulses generated and multiplying by the slit pitch, the moving distance of the spindle 1 can be determined.

The above is a linear gauge.

The present invention provides a verification section of an appropriate length in the moving direction of the spindle 1 of this linear gauge, and counts the number of distance pulses taken out from the light receiving element 5 while the spindle 1 moves through this section length, The temperature is then calculated to accurately calculate the distance pulse generation pitch under arbitrary temperature conditions.

For this purpose, a pair of light receiving element 7 and light source 8 and a light receiving element 9 are arranged at an appropriate length in the moving direction of spindle 1.
and a light source 10 are fixed to the inner wall of the housing 2 so as to face each other with the movable slit plate 3 in between, and each time the tip of the movable slit plate 3 passes through each pair 7 and 8 and 9 and 10, A verification section is provided in which output is taken from the light receiving elements 7 and 9.

The moving slit plate 3 and fixed slit plate 4 of the linear gauge are formed under predetermined temperature conditions, and the slit pitch under the temperature conditions is known. In addition, the linear expansion coefficient α _P and the linear expansion coefficient α _L of the housing 2, that is, the linear expansion coefficient α _L of the verification section where the light receiving element and light source pairs 7 and 8 and 9 and 10 are fixed are also calculated. It is determined by the material and is a known quantity.

Therefore, in advance, set the temperature T _O at which the slit pitch of the entire linear gauge is maintained at a known value P _O , that is,
The spindle 1 is placed under the temperature at which the slit is formed, and the spindle 1 is moved by the length of the test section at that temperature _T.sub.O. At this time, as shown in FIG. 2, the output of the light receiving element 5, that is, the distance pulse, is introduced into the counter 21, while the output of the light receiving elements 7 and 9,
That is, the detection outputs of the start and end points of the verification section are sent to the control signal generator 22, the switches 23 and 24 of the output terminals are closed, and when the light receiving element 7 generates an output, a zero reset command is sent to the counter 21.
By applying a storage command to the memory circuit 25 when the light receiving element 9 generates an output, the number _NO of distance pulses generated during the verification period is stored in the memory circuit 25. The respective linear expansion coefficients α _L , α _P and pitch _PO are also written in the memory circuit 25 .

As a result of the above, the number of distance pulses N _O corresponding to the test interval length under the predetermined temperature T _O , the pitch P _O that is a known quantity, and the coefficients of linear expansion α _L and α _P are stored.

Note that the above is a case where the test interval length is unknown and the pitch P _O is known, but if the test interval length is also measured in advance under the condition of temperature T _O and is a known amount L _O , then the number of pulses generated is The same is true when calculating N _O using the formula L _O /P _O.

Next, when measuring the distance pulse generation pitch P under arbitrary temperature conditions, the number of distance pulses generated during the test interval is counted in the same manner as described above. In this case, there is a difference between the linear expansion coefficient α _L of the housing 2, that is, the verification section, and the linear expansion coefficient α _P of the slit plates 3 and 4, that is, the distance pulse generation part, so the number of distance pulses generated is It was different from N _O
It becomes N _O ′. This value N _O ′ is also the memory circuit 2
5 to be memorized.

Next, the pitch at this memorized predetermined temperature _TO
P _O , number of distance pulses generated corresponding to the test interval length N _O ,
From the number of distance pulses generated N _O ′ corresponding to the length of the test section at the changed temperature T and the respective linear expansion coefficients α _L and α _P of the test section and the distance pulse generation part, the state of the temperature T that has changed can be calculated as follows. Find the distance pulse generation pitch.

Now, if we let the temperature change be △T (=T-T _O ), the resulting change in the test interval length be △L, and the pitch change be △P (=P-P _O ), then the temperature T
Under the condition, the following relationship exists between the number of distance pulses N O ′ and the number N _O ′.

(L _O +△L) = (P _O +△P)N _O ′ (1) Also, L _O =N _O・P _O (2) △P=P _O・α _P・△T (3) △L =L _O・α _L・△T (4) Since there is a relationship, substituting equations (2) to (4) into equation (1) and finding the temperature change △T, we get the following .

△T=N _O ′−N _O ／N _O α _L −N _O ′α _P ＝N _O ′−N _O ／N _O (α _L −α _P )−(N _O ′−N _O ) α _P (5 ) Therefore, by substituting equation (5) into equation (3), the change in pitch ΔP becomes as follows.

△P=P _O・N _O ′−N _O /N _O (α _L /α _P −1) − (N _O ′−N _O ) (6
) As a result, the changed pitch P at temperature T
is, P=(P _O +△P) =P _O {1+N _O ′−N _O /N _O (α _L /α _P −1)−(N _O ′−
N _O )}(7).

Here, N _O (α _L /α _P −1) and P _O are constants,
In the end, the pitch P at any temperature T can be calculated by simply measuring the difference in the number of distance pulses (N _O '-N _O ) corresponding to the length of the test section.

Therefore, the calculation unit 26 in FIG. 2 calculates the above (7).
After calculating the equation, the calculation result is stored in the memory circuit 25 again, thereby maintaining the pitch between distance pulses under the temperature condition.

Below, during actual measurement, switches 23 and 24 are
, the number of distance pulses counted by the counter 21 is sent to the calculator 26, and the pitch P
The true moving distance of the spindle 1 can be found by multiplying by .

The above describes an example in which the present invention is applied to one type of linear gauge, but the long movable slit plate 3 is fixed to the housing 2, and the light receiving element 5,
It goes without saying that the present invention can be implemented in the same manner as described above even in a system in which the light source 6 and the fixed slit 4 are fixed to the spindle 1. In addition, the present invention can also be carried out in the same manner as described above by providing a verification section in a length measuring device of the tatsuchi roller type or the spatial filter type. Pitch is measured in the same manner as above.

Further, in the above embodiment, the pitch is calculated using equation (7), but the calculation may be simplified by using an approximate equation. For example, in equation (1) above, if the change in distance pulse corresponding to the test interval length is set as △N _O (=N _O ′−N _O ), then (L _O +△L) = (P _O +△P )(N _O +△N)=P _O N _O +△
PN _O +△P△N _O ≒P _O N _O +△PN _O (1)′. This is omitted because △PN _O is small, and if the pitch P under the condition of temperature T is calculated from equation (1)' in the same way as above, the calculation formula is simplified as follows. .

P=P _O +△P ≒P _O {1+(N _O ′−N _O )/N _O (α _L /α _P −1)} =P _O +K(N _O ′−N _O ) (7)′ However , K=P _O /N _O (α _L /α _P -1)...Constant The difference between when the pitch P is measured in this way and the distance pulse count value is corrected is as follows.

Now, the coefficient of linear expansion α _P of the slit plate made of glass is 9×10 ^-6 /deg, the coefficient of linear expansion α _L of the test section made of aluminum is 22×10 ^-6 /deg, and the pitch P at a temperature of 15°C is If _O is 1 μm and the test section length L _O is 100 mm, N _O is 10 ⁵ and the temperature difference is 10 degrees (25
℃) is ₁₀₀₀₁₃ , which causes an error of 13 μm in a 100 mm measurement unless multiplied by the changed pitch P. In contrast, the above
The pitch P calculated by (7) or its approximate expression (7)' is an accurate calculation of the pitch under the temperature condition.

In this case, the difference between equation (7) and its approximate equation (7)' is extremely small, and the approximate equation is sufficient.

Also, the pitch P under this measured arbitrary temperature
When correcting the number _of distance pulses during measurement by
_PO is formed at 10 ^-n . n: an integer), and at the moment the tip of the movable slit plate 3 passes the light receiving element 9 from below to above, the value obtained by multiplying △P in equation (7) or (7)' by N is calculated. By adding △P and N at the moment of passing from above to below, the error at 1/2 of the measurement range becomes 0, so the overall error can be reduced to 1. /2. Of course, if a plurality of test sections are provided and addition and subtraction are performed in the same manner as described above, the overall error can be reduced accordingly.

As described above, the present invention calculates the changed pitch under arbitrary temperature conditions by measuring the number of distance pulses during the verification interval, and the pitch can be accurately determined.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an example of an apparatus embodying the present invention, and FIG. 2 is a block diagram showing an example of a measuring circuit embodying the present invention. 1: spindle, 2: housing, 3, 4: slit plate, 5, 7, 9: light receiving element, 6, 8, 10: light source, 21: counter, 22: control signal generator, 2
5: Memory circuit, 26: Arithmetic unit.

Claims (1)

[Claims] 1. At least one test section of an appropriate length is provided, and the number of distance pulses generated during the test section under appropriate temperature conditions N _O , the pitch between the distance pulses P _O ,
The length of the verification interval and the coefficients of linear expansion α _L and α _P of the distance pulse generation part are memorized in advance, and the next time you measure the pitch between distance pulses under any temperature condition, perform the verification under those conditions. The number of distance pulses N _O ' generated during the interval is measured and the stored values N _O , P _O , α _L , α _P are obtained.
From this, the pitch P or its approximate value under that temperature condition is P=(P _O +△P)=P _O {1+(N _O −N _O ′)/N _O (α
_L / α _P −1)−(N _O ′−N _O )}≒P _O {1+(N _O −N _O ′)
/N _O (α _L /α _P −1)} A pitch measurement method between distance pulses in distance measurement.