JP2003254783A - Inductive position transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-band position transducer (magnetic encoder) having a small size and improved accuracy. <P>SOLUTION: The three-band position transducer is constituted of coils 10, 12 and 14 each having wavelengths λ1, λ2, and λ3 all arranged on the scale side, and transmission coils 20, 22 and 24, and reception coils 30, 32, and 34 all arranged in the read head (grid) side. The reception coils 30, 32, and 34 are placed oppositely to the transmission coils 10, 12 and 13. If the transmission coil 20 is driven, the transmission coils 12 and 14 function as the reception coil, generating a directive current. An electromagnetic field is generated from the transmission coil 10 and detected at the reception coil 30. Under a condition of λ2<λ3<λ1, λ1 is prevented from being incomplete form a lack of some pulses. Three wavelengths are synthesized using a phase difference between λ1 and λ2, and a phase difference between λ1 and λ3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductive position transducer, and more particularly to a position transducer having a read head and a scale for detecting an absolute position (ABS) of the read head with respect to the scale.

[0002]

2. Description of the Related Art Position transducers (or magnetic encoders) using an induced current have been known. The position transducer comprises a read head and a scale which are arranged opposite to each other. The read head side is provided with a transmission coil and a reception coil, and the scale side is also provided with a reception coil and a transmission coil. A magnetic field is generated from the read head side transmission coil, and an induced current is generated in the scale side reception coil by this magnetic field. The transmitter coil and the receiver coil on the scale side are connected, and a magnetic field is generated from the transmitter coil due to the induced current generated. The receiving coil on the reading head side detects the magnetic field generated from the transmitting coil on the scale side and outputs it as a detection signal. Since the phase of the detection signal varies depending on the positional relationship between the read head and the scale, the position of the read head from the reference point on the scale, that is, the absolute position can be detected based on the phase of the detection signal.

Usually, on the scale side, transmitting coils having different pitches (wavelengths) λ1 and λ2 are arranged in parallel in the width direction of the scale, and the absolute position is detected based on the phase difference between λ1 and λ2. That is, since the phase of the detection signal is the same for each λ1 only with the coil of λ1, the absolute position exceeding λ1 cannot be uniquely determined. Therefore, λ1
The absolute position is detected by detecting the cycle of λ1 based on the phase difference between λ1 and λ2. Let λ1 be λfine, and λ
One period of the phase difference between 1 and λ2 is defined as λmed, and λme
The following formula is established, where n is the number in which λfine is included in d.

[0004]

## EQU1 ## λmed = n · λfine (1) n is a value determined by the wavelength difference between λ1 and λ2, and the smaller the wavelength difference is, the larger n becomes. ) Increases. The number of cycles of λ1 can be found by determining which range of the range obtained by dividing 360 degrees into n equal parts by the value of the phase difference between λ1 and λ2, and (λ1
The absolute position is calculated by the following equation: (period of) × (number of periods of λ1) + (phase of λ1).

As described above, the measurement range is expanded with the two-wavelength type position transducer. Similarly, a position transducer having a three-wavelength type, that is, a position transducer in which transmitting coils having three different wavelengths of λ1, λ2 and λ3 are arranged on the scale side is also proposed. Has been done.

FIG. 7 shows the structure of such a three-wavelength position transducer. 7A shows the configuration on the scale side, and FIG. 7B shows the configuration on the read head (grid) side. Actually, the scale and the reading head are arranged so as to face each other so as to overlap each other, but for convenience of explanation, the scale and the reading head are shown side by side.

On the scale side, a coil of wavelength λ1 is formed, and also coils of wavelengths λ2 and λ3 are formed. The coil having the wavelength λ1 is formed by the central transmission coil 10 and the reception coils 11 arranged on both sides of the central transmission coil 10 so as to sandwich the central transmission coil 10. Also, the wavelengths λ2 and λ
The coils of 3 also serve as a transmission coil and a reception coil, respectively. That is, the coils of wavelengths λ2 and λ3 are connected,
The receiving coil for the transmitting coil 12 of wavelength λ2 is the transmitting coil 14 of wavelength λ3, and the transmitting coil 1 of wavelength λ3
The transmitter coil 12 having the wavelength λ2 generates a magnetic field by the induced current generated in No. 4. The receiving coil for the transmitting coil 14 of wavelength λ3 is the transmitting coil 12 of wavelength λ2, and
The induced current generated in the transmitter coil 12 causes the transmitter coil 14 having the wavelength λ3 to generate a magnetic field.

On the other hand, on the grid side, a transmitting coil 20 for generating a magnetic field toward the receiving coil 11 of wavelength λ1 and a receiving coil 30 for detecting the magnetic field generated by the transmitting coil 10 of wavelength λ1 are provided. Further, a transmitting coil 22 that generates a magnetic field toward the λ2 receiving coil and a receiving coil 32 that detects the magnetic field from the λ2 transmitting coil 12 are provided. Further, a transmitting coil 24 that generates a magnetic field for the receiving coil of λ3 and a receiving coil 34 that detects the magnetic field from the transmitting coil 14 of wavelength λ3 are provided. The transmission coil 20 of the grid faces the reception coil 11 of the scale,
The receiving coil 30 faces the transmitting coil 10 and is magnetically coupled. Similarly, the transmission coil 24 has a wavelength of λ
Facing the receiving coil for the transmitting coil 14 of 3),
The receiving coil 32 faces the transmitting coil 12 and is magnetically coupled. The transmission coil 22 faces the transmission coil 14 (the reception coil for the transmission coil 12 having the wavelength λ2), and the reception coil 34 faces the transmission coil 14 and is magnetically coupled.

Transmission coils 20, 22, 24 on the grid side
Drive current is sequentially supplied to the receiver coil 3 in a time-division manner.
0, 32, and 34 detect the magnetic fields sequentially generated in the scale transmission coils 10, 12, and 14 by the respective drive currents, and output signals. λfine is formed by λ1, λmed is formed by the phase difference between λ1 and λ2, and λcoa is formed by the phase difference between λ2 and λ3. If the number of λmed included in λcoa is m,

(2) λcoa = m · λmed = m · n · λfine = m · n · λ1 (2) Since the measurement range is determined by m · n, 2 wavelengths λ
The measurement range is increased as compared with the position transducer using 1 and λ2.

FIG. 8 shows the above-mentioned λfine and λme.
The positional accuracy of d and λcoa is shown. In the figure,
The horizontal axis is the position from the reference point of the scale, and the vertical axis is the phase. The precision becomes lower (rougher) in the order of λfine, λmed, and λcoa, and by combining these, the absolute position can be uniquely determined within the range of λcoa.

It should be noted that λfine, λmed, λcoa
Is specifically defined as follows.

[0012]

[Equation 3] λfine = λ1 λmed = λ2λ1 / (λ2-λ1) = nλfine λcoa = λ3λ2 / (λ3-λ2) = mλmed (3) Here, m and n are positive integers.

[0013]

As described above, the three wavelengths λ
Although it is possible to increase the measurement range by using 1, λ2 and λ3, as shown in FIG.
With respect to the above, even if the transmitting coil and the receiving coil are made common, a total of five rows of coil groups are formed in the width direction of the scale, and there is a problem in that the scale size and eventually the position transducer size increase. In recent years, devices such as NCs have been downsized, and there is a demand for further miniaturization and higher accuracy of position transducers that are attached to these devices and output position data.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a small-sized and highly accurate three-wavelength position transducer.

[0015]

In order to achieve the above object, the present invention provides a read head having a magnetic field generating means and a magnetic field detecting means, and a magnetic field from the magnetic field generating means which is arranged so as to face the read head. A magnetic coupling coil including a receiving coil that generates an induced current and a transmitting coil that generates a magnetic field by the induced current includes a scale formed at a predetermined pitch λ along the measurement direction, and a magnetic field from the transmitting coil of the scale. Is an inductive transducer for detecting the position of the read head with respect to the scale based on the phase of a detection signal obtained by detecting the magnetic field by the magnetic field detecting means,
A first transmitting coil formed along the measuring direction at a pitch λ1 of the second, and a second transmitting coil formed along the measuring direction at a second pitch λ2 different from the first pitch λ1; A third transmission coil formed along the measurement direction at a third pitch λ3 different from the first pitch λ1 and the second pitch λ2, and the first transmission coil and the second transmission coil.
The transmission coils are connected to each other, the first transmission coil and the third transmission coil are connected to each other, and the second transmission coil and the third transmission coil function as a reception coil connected to the first transmission coil, The first transmitting coil functions as a receiving coil connected to the second receiving coil or the third receiving coil.

Here, the first transmitting coil, the second transmitting coil and the third transmitting coil are formed side by side in the width direction of the scale, and the first transmitting coil is the second transmitting coil and the third transmitting coil. Is preferably formed between the two.

Further, it is preferable that the first pitch λ1, the second pitch λ2, and the third pitch λ3 satisfy a magnitude relation of λ2 <λ3 <λ1 or a magnitude relation of λ3 <λ2 <λ1. .

In this case, the phase of the magnetic field detection signal from the first transmission coil, the phase of the magnetic field detection signal from the first transmission coil, and the phase of the magnetic field detection signal from the second transmission coil. It is preferable to detect the position based on a phase difference and a phase difference between the phase of the detection signal of the magnetic field from the first transmission coil and the phase of the detection signal of the magnetic field from the third transmission coil.

As described above, in the position transducer (magnetic encoder) of the present invention, coils with three pitches (λ1, λ2, λ3) (three wavelengths) are used, but the transmitter coil and the receiver coil are used as the coil arrangement on the scale side. By doing so, the number of coils in the scale width direction is reduced and the size is reduced. That is, the first transmission coil (λ1 coil) and the second transmission coil (λ2 coil) are connected so that the λ2 coil functions as the reception coil of the λ1 coil. That is,
The magnetic field generated from the transmission coil on the read head side causes an induced current in the λ2 coil, and the induced current is supplied to the λ1 coil to generate a magnetic field from the λ1 coil. Similarly, the λ1 coil is made to function as a receiving coil for the λ2 coil. The same applies to the relationship between the first transmission coil and the third transmission coil. In this way, the number of coils can be reduced and the size can be reduced by also functioning as a receiving coil of the transmitting coil to which the three transmitting coils are respectively connected. Since the first transmission coil (λ1 coil), the second transmission coil (λ2 coil), and the third transmission coil (λ3 coil) are driven in a time division manner, there is no problem even if they are used for both transmission and reception.

When the first transmitting coil and the second transmitting coil having different pitches (wavelengths) are connected to each other and the first transmitting coil and the third transmitting coil are connected to each other, if the pitch of the first transmitting coil is minimized, One transmitter coil may cause a "floating coil" or "tooth missing" that cannot be connected, and the position cannot be detected in such a floating portion, resulting in a decrease in accuracy.
Therefore, by causing the second transmitting coil or the third transmitting coil, which only detects the number of cycles of λ1, to have floating or missing teeth, it is possible to suppress the influence of floating or missing teeth on accuracy. The prevention of floating or missing of λ1 can be obtained by adopting a wavelength configuration that maximizes the pitch of λ1.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a three-wavelength position transducer (magnetic encoder) according to this embodiment. FIG. 1A shows the configuration on the scale side.
(B) is a configuration on the read head (grid) side.
Note that, in reality, the scale and the grid are opposed to each other with a predetermined distance therebetween, as in the conventional device. First, the configuration on the scale side will be described.

On the scale side, a transmission coil 10 having a wavelength (pitch) λ1, a transmission coil 12 having a wavelength λ2, and a wavelength λ
Three transmitter coils 14 are formed side by side in the width direction of the scale. The transmission coil 10 having the wavelength λ1 is arranged between the transmission coil 12 having the wavelength λ2 and the transmission coil 14 having the wavelength λ3. The transmission coil 10 having the wavelength λ1 and the transmission coil 12 having the wavelength λ2 are connected to each other, and the transmission coil 10 having the wavelength λ1 and the transmission coil 14 having the wavelength λ3 are connected to each other. Wavelength λ2
The transmitting coil 12 of 1 functions as a receiving coil for the transmitting coil 10 of wavelength λ1. Further, the transmission coil 10 having the wavelength λ1 functions as a reception coil for the transmission coil 12 having the wavelength λ2. Similarly, the transmission coil 14 of wavelength λ3
Functions as a receiving coil for the transmitting coil 10 having the wavelength λ1, and the transmitting coil 10 having the wavelength λ1 functions as a receiving coil for the transmitting coil 14 having the wavelength λ3.

On the other hand, the structure on the grid side is as follows. That is, the transmission coils 20, 22, and 24 are provided, the transmission coil 20 is arranged to face the transmission coil 12 having the wavelength λ2 and the transmission coil 14 having the wavelength λ3, and the transmission coils 22 and 24 are provided to the transmission coil 10 having the wavelength λ1. It is arranged facing each other. Further, the reception coil 30 is arranged so as to face the transmission coil 10, the reception coil 32 is arranged so as to face the transmission coil 12, and the reception coil 34 is arranged so as to face the transmission coil 14 and are magnetically coupled to each other.

By supplying a drive current to the transmitter coil 20, the transmitter coil 20 transmits the transmitter coil 12 having the wavelength λ2 (the receiver coil for the transmitter coil 10 having the wavelength λ1) and the transmitter coil 14 having the wavelength λ3 (the transmitter coil having the wavelength λ1). A magnetic field is generated toward the receiver coil), and the induced current generated in the transmitter coil 12 of wavelength λ2 and the induced current generated in the transmitter coil 14 of wavelength λ3 are both supplied to the transmitter coil 10 of wavelength λ1. A magnetic field is generated by the induced current supplied to the transmission coil 10 having the wavelength λ1, and this magnetic field has the wavelength λ1.
Receiver coil 30 arranged to face the transmitter coil 10
Is received by and output as a detection signal.

Further, by supplying a drive current to the transmission coil 22, a magnetic field is generated from the transmission coil 22 toward the transmission coil 10 having the wavelength λ1, and the transmission coil 1 having the wavelength λ1 is generated.
An induced current occurs at 0. This induced current is supplied to the transmission coil 12 of wavelength λ2, a magnetic field is generated from the transmission coil 12 of wavelength λ2, and is received by the reception coil 32 and output as a detection signal.

Further, by supplying a driving current to the transmission coil 24, a magnetic field is generated from the transmission coil 24 toward the transmission coil 10 having the wavelength λ1, and an induced current is generated in the transmission coil 10. This induced current is supplied to the transmission coil 14. The transmission coil 14 generates a magnetic field by this induced current, and is received by the reception coil 34 arranged facing the transmission coil 14 and output as a detection signal. The transmission coils 20, 22, and 24 are sequentially driven as in the conventional device.

Since the coils of three wavelengths on the scale side mutually function as a transmitting coil and a receiving coil, it is only necessary to form coils in three rows in the scale width direction, unlike FIG.
The width of the scale can be reduced.

The operation of the three-wavelength position encoder of this embodiment will be described in more detail below.

2 to 4, transmission coils 20, 22,
The operation explanatory view of the scale and the grid in the case of sequentially driving 24 is shown. FIG. 2 is an operation explanatory diagram when the transmission coil 20 is driven. Transmission coil 2 on the grid side
0 is arranged facing the transmission coils 12 and 14 on the scale side,
The receiving coil 30 on the grid side is arranged to face the transmitting coil 10 on the scale side. A magnetic field is generated from the scale-side transmission coil 10 by driving the grid-side transmission coil 20, and this magnetic field is received by the reception coil 30 and a detection signal is output. The transmitter coil 10 on the scale side includes the transmitter coil 1
Since the induced current from 2 and the induced current from the transmitting coil 14 are both supplied, the receiving coil 30 can obtain a detection signal with high intensity. That is, noise-resistant measurement can be performed. The period of the detection signal is λ1.

FIG. 3 is an explanatory view of the operation when driving the transmission coil 22. The grid-side transmission coil 22 is arranged to face the scale-side transmission coil 10, and the grid-side reception coil 32 is arranged to face the scale-side transmission coil 12. By driving the transmitting coil 22, a magnetic field is generated from the transmitting coil 12 via the transmitting coil 10, and this magnetic field is detected by the receiving coil 32. The detection signal from the receiving coil 32 is a detection signal with a period λ2.

FIG. 4 is an explanatory view of the operation when driving the transmission coil 24. The grid-side transmission coil 24 is arranged to face the scale-side transmission coil 10, and the grid-side reception coil 34 is arranged to face the scale-side transmission coil 14. By driving the transmitting coil 24, a magnetic field is generated from the transmitting coil 14 on the scale side via the transmitting coil 10, and this magnetic field is detected by the receiving coil 34. The detection signal from the receiving coil 34 is a detection signal having a period λ3.

Therefore, as in the conventional device,
fine, λmed and λ2 and λ3 by the phase difference between λ1 and λ2
Λcoa is formed by the phase difference of
The absolute position can be detected using ed and λcoa.

On the other hand, the three wavelengths λ1, λ2, λ3 are
By forming both the transmission coil and the reception coil on the scale, there is a problem that so-called "tooth missing" of the coil occurs. This is because the three coils are λ1, λ2, and λ respectively.
Since it has a wavelength different from 3, when connecting the coil of λ1 and the coil of λ2, and the coil of λ1 and the coil of λ3, the positional relationship between both coils gradually deviates, so it is possible to connect somewhere. No, connection "jump"
Is caused.

In FIG. 5, the coil of λ1 is arranged in the center,
The state of missing teeth is shown when the coils of λ2 and λ3 are arranged on both sides. For example, λ1 = 1.024 mm,
If λ2 = 1.092 mm and λ3 = 1.028 mm, the λ1 coil that cannot be connected to the λ2 coil and λ3
There is a λ1 coil that cannot be connected to (the part indicated as “floating coil” in the figure). When such a floating coil (or missing tooth) is present, the periodic distribution of the magnetic field is disturbed at that portion, and particularly when it occurs in the transmission coil 10 having the wavelength λ1 which is the most accurate transmission coil, the detection accuracy is greatly affected. There is.

Therefore, in the present embodiment, simply λ1 <λ2
Rather than setting <λ3 (or λ1 <λ3 <λ2), the wavelength configuration is changed to suppress accuracy deterioration.

Specifically, λ located at the center of the scale
The wavelength λ1 of one transmitter coil 10 is maximized, and λ2 <λ3 <λ1 or λ3 <λ2 <λ1. With such a wavelength configuration, it is possible to cause tooth gaps in λ2 or λ3 instead of λ1. Since .lamda.2 and .lamda.3 are only for calculating .lamda.med and .lamda.coa, the permissible error is significantly larger than that of .lamda.1, and therefore it is possible to suppress the accuracy deterioration due to tooth loss. Specifically, for example, λ1 =
1.024 mm, λ2 = 0.963 mm, λ3 = 1.0
It may be 20 mm, so that the transmission coil 1 of λ2
It is possible to cause tooth loss only in 2. FIG. 6 shows a coil configuration on the scale side when λ2 <λ3 <λ1.

If λ1 is increased in order to prevent tooth loss, the resolution will be reduced accordingly.
Since the detection signal of λ1 has a high intensity, sufficient detection accuracy can be ensured.

Further, for example, λ2 <λ3 <λ1 and λ2
If a tooth gap occurs in λ, the λfine defined by λ1 is not affected, but the accuracy of λmed defined by the phase difference between λ1 and λ2 or λcoa defined by λ2 and λ3 decreases. Especially, with respect to λcoa, λ2 and λ with low accuracy
Since 3 is used, it is considered that the effect is large. Therefore, when a missing tooth is generated in λ2 or λ3, λ
coa is not defined by the phase difference between λ2 and λ3, but λ
It is preferable to define the phase difference between 1 and λ3. Specifically, it is defined as follows.

[0040]

## EQU00004 ## .lamda.fine = .lamda.1 .lamda.med = .lamda.2.lamda.1 / (. Lamda.2-.lamda.1) .lamda.coa = .lamda.3.lamda.1 / (. Lamda.3-.lamda.1) (4) As described above, in the present embodiment, the three-wavelength type position transducer has the scale side. Since the coils are arranged such that the coils are arranged in three rows in the scale width direction, the scale size, and hence the size of the entire position transducer, can be reduced.

Further, in the present embodiment, in the case of the three-row coil structure, the coil is not lifted or the tooth missing is caused in the coil of λ1 having the highest accuracy, and the coil is only for purifying λmed or λcoa. It has a wavelength configuration that causes λ2 or λ3, and
Since a is defined not by λ2 and λ3 but by λ1 and λ3, it is possible to effectively suppress deterioration in accuracy due to floating or missing teeth.

[0042]

As described above, according to the present invention, it is possible to increase the detection range and obtain a compact and highly accurate position transducer.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a scale and a grid of a position transducer according to an embodiment.

FIG. 2 is an operation explanatory view when the transmission coil 20 is driven in FIG.

FIG. 3 is an operation explanatory diagram when the transmission coil 22 is driven in FIG.

FIG. 4 is a diagram for explaining the operation when the transmission coil 24 is driven in FIG.

FIG. 5 is an explanatory diagram of missing teeth (lifting) of the λ1 transmission coil.

FIG. 6 is an explanatory diagram of missing teeth (lifting) of a λ2 transmission coil.

FIG. 7 is a scale and grid configuration diagram of a conventional three-wavelength position transducer.

8 is a λfin of the three-wavelength position encoder of FIG.
It is explanatory drawing of e, (lambda) med, and (lambda) coa.

[Explanation of symbols]

10, 12, 14 Transmit coil (scale side), 20,
22, 24 Transmit coil (grid side), 30, 32,
34 Receiver coil (grid side).

Claims (5)

[Claims] 1. A read head having a magnetic field generating means and a magnetic field detecting means, a receiving coil arranged to face the read head and generating an induced current by a magnetic field from the magnetic field generating means, and a magnetic field generated by the induced current. A scale in which a magnetic coupling coil formed of a transmission coil is formed at a predetermined pitch λ along the measurement direction; and a phase of a detection signal obtained by detecting the magnetic field from the transmission coil of the scale by the magnetic field detection means. An inductive transducer for detecting the position of the read head with respect to the scale based on, wherein the magnetic coupling coil includes a first transmission coil formed along the measurement direction at a first pitch λ1; A second transmission coil formed along the measurement direction at a second pitch λ2 different from the pitch λ1 of Pitch λ1 and a third which is formed along the measuring direction and at a different third pitch λ3 second pitch λ2
A transmission coil, the first transmission coil and the second transmission coil are connected to each other, the first transmission coil and the third transmission coil are connected to each other, the second transmission coil and the third transmission coil Is the first
The first transmitting coil functions as a receiving coil connected to the transmitting coil, and the first transmitting coil is the second receiving coil or the third receiving coil.
An inductive position transducer, which functions as a receiving coil connected to a receiving coil. 2. The position transducer according to claim 1, wherein the first transmission coil, the second transmission coil and the third transmission coil are formed side by side in the width direction of the scale, and the first transmission coil is the second transmission coil. An inductive position transducer formed between a transmission coil and the third transmission coil. 3. The position transducer according to claim 2, wherein the first pitch λ1, the second pitch λ2, and the third pitch λ3 satisfy a magnitude relation of λ2 <λ3 <λ1. Mold position transducer. 4. The induction device according to claim 2, wherein the first pitch λ1, the second pitch λ2, and the third pitch λ3 satisfy a magnitude relation of λ3 <λ2 <λ1. Mold position transducer. 5. The position transducer according to claim 3, wherein the phase of the detection signal of the magnetic field from the first transmission coil, the phase of the detection signal of the magnetic field from the first transmission coil, and the phase of the detection signal of the detection signal of the magnetic field from the first transmission coil. The phase difference between the phase of the magnetic field detection signal from the second transmission coil and the phase difference between the phase of the magnetic field detection signal from the first transmission coil and the phase of the magnetic field detection signal from the third transmission coil. An inductive position transducer, which detects the position based on the above.