CA1167545A - Length measuring device - Google Patents
Length measuring deviceInfo
- Publication number
- CA1167545A CA1167545A CA000396520A CA396520A CA1167545A CA 1167545 A CA1167545 A CA 1167545A CA 000396520 A CA000396520 A CA 000396520A CA 396520 A CA396520 A CA 396520A CA 1167545 A CA1167545 A CA 1167545A
- Authority
- CA
- Canada
- Prior art keywords
- magnetic
- signal magnetic
- origin
- scale
- measuring device
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
- Transmission And Conversion Of Sensor Element Output (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is a length measuring device, which makes use of magnetic recording and recording techniques of effecting quasi-absolute system length measurement by reading reference graduations provided on a plane magnetic scale where a magnetic grating is formed and an origin signal provided from an origin signal magnetic member.
Disclosed is a length measuring device, which makes use of magnetic recording and recording techniques of effecting quasi-absolute system length measurement by reading reference graduations provided on a plane magnetic scale where a magnetic grating is formed and an origin signal provided from an origin signal magnetic member.
Description
LENGTH MEASURING DEVICE
BACKGROUND OF THE INVENTION
Field of the invention:
This invention relates to length measuring devices based on the measuring principles by a magnetic grating and, more particularly, to length measuring devices, in ~hich standard graduations of a plane-magnetic scale formed in a magnetic grating are reaa out by a detecting head.
Description of the prior art:
The length measuring.systems using a magnetic scale formed on a magnetic grating are generally based upon an incremental system, in which pulse signals each obtained for unit displaceme.nt of a detecting head relative to a magnetic scale are cumulatively counted to derive the measurement value. The length measuring system based upon-such an incremental system is simple in construction and inexpensive. On the demerit side, however, the past positional information is entirely lost with a loss of power supply. .In addition, iron particles and other particles are likely to be accumulated on the magnetic scale surface. If iron particles are caught between the magnetic scale and the detecting head which is moved relative thereto in a close prosimity thereo~, they will cause damage to the detecting head and magnetic scale.
i^fS~5 SUMMARY OF THE INVENTION
An object of the present invention is to provide a length measuriny system, which permits measurement in an absolute system based upon the measuring principles of the magnetic grating.
Another objoct of the present invention is to provide a length measuring device, which uses a plane magnetic scale and has superior environment-proof properties.
A further object of the present invention is to provide a length measuring device, which has a function of cleaning iron particles and other particles deposited on the surface of a magnetic scale having a detecting head.
BRIEF DESCRIPTION OF THE DRAWINGS
.
Figs. 1 and 2 show an embodiment of the length measuring system according to the present invention, with Fig. 1 b~ing a schematic plan view and Fig. 2 being a longitudinal sectional view;
Figs. 3 and 4 show a different embodiment of the length measuring device according to the present invention, with Fig. 3 being a schematic plan view and Fig. 4 being
BACKGROUND OF THE INVENTION
Field of the invention:
This invention relates to length measuring devices based on the measuring principles by a magnetic grating and, more particularly, to length measuring devices, in ~hich standard graduations of a plane-magnetic scale formed in a magnetic grating are reaa out by a detecting head.
Description of the prior art:
The length measuring.systems using a magnetic scale formed on a magnetic grating are generally based upon an incremental system, in which pulse signals each obtained for unit displaceme.nt of a detecting head relative to a magnetic scale are cumulatively counted to derive the measurement value. The length measuring system based upon-such an incremental system is simple in construction and inexpensive. On the demerit side, however, the past positional information is entirely lost with a loss of power supply. .In addition, iron particles and other particles are likely to be accumulated on the magnetic scale surface. If iron particles are caught between the magnetic scale and the detecting head which is moved relative thereto in a close prosimity thereo~, they will cause damage to the detecting head and magnetic scale.
i^fS~5 SUMMARY OF THE INVENTION
An object of the present invention is to provide a length measuriny system, which permits measurement in an absolute system based upon the measuring principles of the magnetic grating.
Another objoct of the present invention is to provide a length measuring device, which uses a plane magnetic scale and has superior environment-proof properties.
A further object of the present invention is to provide a length measuring device, which has a function of cleaning iron particles and other particles deposited on the surface of a magnetic scale having a detecting head.
BRIEF DESCRIPTION OF THE DRAWINGS
.
Figs. 1 and 2 show an embodiment of the length measuring system according to the present invention, with Fig. 1 b~ing a schematic plan view and Fig. 2 being a longitudinal sectional view;
Figs. 3 and 4 show a different embodiment of the length measuring device according to the present invention, with Fig. 3 being a schematic plan view and Fig. 4 being
2 longitudinal view; and ~~~~~ Fig. 5 is a partly broken-away perspective ~iew showing a modification of the magnetic scale body employed in the length measuring device according to the present invention; and Fig. 6 is a schematic plan view showing a different modification of the magnetic scale body according to the present inve~tion.
DESCRIPTIOM OF THE PRF,FERRED EMBODIMENTS
Figs. 1 and 2 show an embodiment of the present invention applied to a magnetic scale device, in which the magnetic grating is formed by a transversal magnetic recording. A magnetic scale body 4 includes a scale base 1, in which an origin s~gnal magnetic member 2 is burried, and one surface la of the scale base 1 inclusive of the top 2a of the origin signal magnetic member 2 is covered by a measurement signal magnetic member 3.
The scale base 1 is made of an non-magnetic material and formed near one end thereof with a recess lA, in which the origin signal magnetic member-2 is burried. The origin signal magnetic member 2 is made of a rare earth element magnet, a rubber magnet or a plastic magnet and generates a magnetic field Ho as an origin signal in the direction perpendicular to the surface la. The measurement signal magnetic member 3 is constituted by a rolled magnet made of spin^dal magnetic material such as Cu~Ni~Fe or Cu~N} Co and is magnetized to provide a magnetic grating such that a surface field measurement signal is generated by transversal magnetic recording parallel to a plane-finished 5~i frictional surface 4a~ The rolled magnet forming the measurement signal magnetic member 3 has a magnetic permeability of 1 to 3, and ~he signal field for the origin i5 not spoiled by covering the surface 2a of the origin signal magnetic member 2. The magnetic grating of *he measurement signal magne~ic member 3 may be formed up to a position covering the origin signal magnetic member 2.
A detecting head body ~, which is movable relat`ive to the magnetic scale bo~y 4, includes a head case 6, which accommodates an origin detecting head 7 and a measurement detecting head 8, these heads being spaced apart a predetermined distancP Ll. Scrapers 9A and 9B
are mounted on the opposite side walls 6a and 6b of the head case 6. The scrapers 9A and 9B are made of an elastic material such as polyrethane or nitrile rubbex. The scrapers 9A and 9s have respective sharp edges 9a and 9b, which are in elastic contact with a frictional surface 4a of the measurement signal magnetic member 3. As the detecting head body 5 is moved relative to the magne~ic scale body 4, they are also moved in frictional contact with the frictional surface 4a of the--magnetic scale body 4 to remove iron particles deposited on the frictional surface 4a.
The origin detecting head 7 consists of a magnetic switch making use of a ferromagnetic magnetic reluctance ~1~7S~l~
effect element or the like, and is secured with a comparatively large clearance provided with respect to the frictional surface 4a of the magnetic scale body 4.
The measurement detecting head 8 consist~ of a multi-~
gap magnetic head of a magnetic flux response type or a magnetic sensor based upon the ferromagnetic magnetic reluctance effect element. It is disposed such that it is and is moved in elastic contact with the frictional surface 4a with the movement of the detecting head body 5 with respect to the magnetic scale body 4.
The embodiment of the above construction is mos,t,, suitably used as a high resolution length measurement device, in which magnetic grating of a short wavelength of 2 mm or less is formed by lateral magnetic field recording in the measurement signal magnetic member 3 of the magnetic scale body 4. The magnetic field Ho from the origin signal magnetic member 2 may be detected as origin signal information by the origin detecting head 7, and the signal field HS from the measurement signal magnetic member 3, i.e., the measurement position information detected by the measurement detecting head 3, may be provided as the absolute position information based upon the origin position information. In addition, the frictional surface 4a of the magnetic scale body 4 is always cleaned by the scrapers 9A and 9B, so that it is possible to provide a length measurement device 7~
which c~n withstand use even in a heavy operational environment where iron particles are scattered.
Figs. 3 and 4 show a different embodiment of the present invention applied to a magnetic scale device/ - -in which the magnetic grating is formed by longitudinal magnetic recording. A magnetic scale body 14 includes a scale base 11, an origin signal magnetic member 12 and measurement signal magnetic member 13 formed thereon, and a protective layer 20 consisting of a non-magnetic material formed over the entire top surface of the magnetic members 12 and 13~ In this embodiment, an origin track TRor in which the origin signal magnetic member 12 is disposed, and a measurement track T~ , in which the measuremen~ signal magnetic member 13 i5 disposed, are formed on the magnetic scale body~l4.
A magnetic head body 15 includes an origin detecting head 17 and a measurement detecting head 18 respectively for tracing the tracks TRo and TRS, these heads being spaced apart a predetermined distance L2. The origin signal magnetic member 12 and mea~urement signal magnetic member 13 are made of rubber magnet or barium ferrite which can be comparatively readily available~
The scale base 11 is made of a magnetic material in order to reinforce the signal field HS formed by the measurement signal magnetic member 13. Further, in a po~tion of the origin track TRo exclusive of t~e origin ~7~i~5 track TRo exclusive of the origin signal magnetic member 12~ a spacer 10 having substantially the same thickness t as the measurement signal magnetic member 13 is interposed between the 5cal2 base il and the protective layer 20 consisting of a non-magnetic sheet.
In this embodiment, the scale base 11 is formed with a recess llA for accommodating the origin signal magnetic member-12, while the spacer 10 which is made of a magnetic plate is used together with the measurement signal magnetic member 13 for accurate matching of the thickness -t of the magnetic member 13 and spacer 10 and also uniform finish of the upper surface of the protective layer 20.
The detecting head body 15, which includes the origin detecting head 17 and measurement detecting ~,.. ~ .
head 18 for tracing the respective tracks TRo and TRS of the magnetic scal~ body 14, has the opposite side walls 16a and 16b of the h~ad case 16 provided scrapers l9A
and 19B having respective sharp edges l9a and l9b having a width T across the individual tracks TRo and TRS.
In the embodiment of the above construction, a magnetic grating of a comparatively large wavelength of 1 mm or above is formed by longitudinal magnetic recording in the measurement signal magnetic member 13. Thus, it can be most suitably used as a length measuring device having a comparatively low resolution. Also, ~y setting ~7~
the wavelength of the magnetic gra-ting to be comparatively ~arye, a large clearance between the measurement signal magnetic member 13 and measurement detecting head 18 may be obtained~ and a'so~ ickness of the protective layer 20 as a non-magnetic sheet provided on the surface of the magnetic scale body 14 can be sufficiently accommodated within the aforementioned range of clearance.
In this embodiment again, the frictional surface 14a of the magnetic scale body 14 may be obtained as a uniformly finished plane ~urface. Thus, it is possible to obtain sufficient effect of cleanlng by the scrapers l9A and l9B. In addition, it is possible to obtain an absolute length measurement output on the basis of the information of the point of origin~
The spacer 10 in the embodiment may be formed on a common magnetic plate integral with the measurement signal magnetic member 13. Fig. 5 shows a modification of the magnetic scale device utilizing the magnetic grating formed by the longitudinal magnetic recording as described above. This modification has a structure sonsisting of a scale base 21, a magnetic plate 25 made of barium ferrite and a protective layer 30 made of a non-magnetic sheet. The magnetic grating by the longitudinal recording is selectively provided in a region of the magnetic plate 25 corresponding to the measurement track T ~ , and thus the measurement signal ~67~
magnetic member 23 is formed. The plate 25 is formed in a region corresponding to the origin track TRo with a recess defining an acco~nodating section 26 for the origin signal magnetic merr~er ~2. The origin signal magnetic member 22 is received and secured in the accommodating section 26 formed in the magnetic plate 25 on the scale base 21. A protective layer 30 is provided to cover the entire surface of the magnetic plate 25 and origin signal magnetic member 30, whereby a uniformly finished plane surface can be provided as the frictional surface 24a of the magnetic scale body 24.
While in the above individual embodiments a single origin signal magnetic member is arranged on the scale base, it is also possible to apply the present invention to a length measuring device as shown in Fig. 6, in which a magnetic scale body 32 including a plurality of origin signal magnetic members 32a,32b ... 32n providing information of respective predetermined positions is used to obtain a length measurement output based upon the information of the individual origin points.
DESCRIPTIOM OF THE PRF,FERRED EMBODIMENTS
Figs. 1 and 2 show an embodiment of the present invention applied to a magnetic scale device, in which the magnetic grating is formed by a transversal magnetic recording. A magnetic scale body 4 includes a scale base 1, in which an origin s~gnal magnetic member 2 is burried, and one surface la of the scale base 1 inclusive of the top 2a of the origin signal magnetic member 2 is covered by a measurement signal magnetic member 3.
The scale base 1 is made of an non-magnetic material and formed near one end thereof with a recess lA, in which the origin signal magnetic member-2 is burried. The origin signal magnetic member 2 is made of a rare earth element magnet, a rubber magnet or a plastic magnet and generates a magnetic field Ho as an origin signal in the direction perpendicular to the surface la. The measurement signal magnetic member 3 is constituted by a rolled magnet made of spin^dal magnetic material such as Cu~Ni~Fe or Cu~N} Co and is magnetized to provide a magnetic grating such that a surface field measurement signal is generated by transversal magnetic recording parallel to a plane-finished 5~i frictional surface 4a~ The rolled magnet forming the measurement signal magnetic member 3 has a magnetic permeability of 1 to 3, and ~he signal field for the origin i5 not spoiled by covering the surface 2a of the origin signal magnetic member 2. The magnetic grating of *he measurement signal magne~ic member 3 may be formed up to a position covering the origin signal magnetic member 2.
A detecting head body ~, which is movable relat`ive to the magnetic scale bo~y 4, includes a head case 6, which accommodates an origin detecting head 7 and a measurement detecting head 8, these heads being spaced apart a predetermined distancP Ll. Scrapers 9A and 9B
are mounted on the opposite side walls 6a and 6b of the head case 6. The scrapers 9A and 9B are made of an elastic material such as polyrethane or nitrile rubbex. The scrapers 9A and 9s have respective sharp edges 9a and 9b, which are in elastic contact with a frictional surface 4a of the measurement signal magnetic member 3. As the detecting head body 5 is moved relative to the magne~ic scale body 4, they are also moved in frictional contact with the frictional surface 4a of the--magnetic scale body 4 to remove iron particles deposited on the frictional surface 4a.
The origin detecting head 7 consists of a magnetic switch making use of a ferromagnetic magnetic reluctance ~1~7S~l~
effect element or the like, and is secured with a comparatively large clearance provided with respect to the frictional surface 4a of the magnetic scale body 4.
The measurement detecting head 8 consist~ of a multi-~
gap magnetic head of a magnetic flux response type or a magnetic sensor based upon the ferromagnetic magnetic reluctance effect element. It is disposed such that it is and is moved in elastic contact with the frictional surface 4a with the movement of the detecting head body 5 with respect to the magnetic scale body 4.
The embodiment of the above construction is mos,t,, suitably used as a high resolution length measurement device, in which magnetic grating of a short wavelength of 2 mm or less is formed by lateral magnetic field recording in the measurement signal magnetic member 3 of the magnetic scale body 4. The magnetic field Ho from the origin signal magnetic member 2 may be detected as origin signal information by the origin detecting head 7, and the signal field HS from the measurement signal magnetic member 3, i.e., the measurement position information detected by the measurement detecting head 3, may be provided as the absolute position information based upon the origin position information. In addition, the frictional surface 4a of the magnetic scale body 4 is always cleaned by the scrapers 9A and 9B, so that it is possible to provide a length measurement device 7~
which c~n withstand use even in a heavy operational environment where iron particles are scattered.
Figs. 3 and 4 show a different embodiment of the present invention applied to a magnetic scale device/ - -in which the magnetic grating is formed by longitudinal magnetic recording. A magnetic scale body 14 includes a scale base 11, an origin signal magnetic member 12 and measurement signal magnetic member 13 formed thereon, and a protective layer 20 consisting of a non-magnetic material formed over the entire top surface of the magnetic members 12 and 13~ In this embodiment, an origin track TRor in which the origin signal magnetic member 12 is disposed, and a measurement track T~ , in which the measuremen~ signal magnetic member 13 i5 disposed, are formed on the magnetic scale body~l4.
A magnetic head body 15 includes an origin detecting head 17 and a measurement detecting head 18 respectively for tracing the tracks TRo and TRS, these heads being spaced apart a predetermined distance L2. The origin signal magnetic member 12 and mea~urement signal magnetic member 13 are made of rubber magnet or barium ferrite which can be comparatively readily available~
The scale base 11 is made of a magnetic material in order to reinforce the signal field HS formed by the measurement signal magnetic member 13. Further, in a po~tion of the origin track TRo exclusive of t~e origin ~7~i~5 track TRo exclusive of the origin signal magnetic member 12~ a spacer 10 having substantially the same thickness t as the measurement signal magnetic member 13 is interposed between the 5cal2 base il and the protective layer 20 consisting of a non-magnetic sheet.
In this embodiment, the scale base 11 is formed with a recess llA for accommodating the origin signal magnetic member-12, while the spacer 10 which is made of a magnetic plate is used together with the measurement signal magnetic member 13 for accurate matching of the thickness -t of the magnetic member 13 and spacer 10 and also uniform finish of the upper surface of the protective layer 20.
The detecting head body 15, which includes the origin detecting head 17 and measurement detecting ~,.. ~ .
head 18 for tracing the respective tracks TRo and TRS of the magnetic scal~ body 14, has the opposite side walls 16a and 16b of the h~ad case 16 provided scrapers l9A
and 19B having respective sharp edges l9a and l9b having a width T across the individual tracks TRo and TRS.
In the embodiment of the above construction, a magnetic grating of a comparatively large wavelength of 1 mm or above is formed by longitudinal magnetic recording in the measurement signal magnetic member 13. Thus, it can be most suitably used as a length measuring device having a comparatively low resolution. Also, ~y setting ~7~
the wavelength of the magnetic gra-ting to be comparatively ~arye, a large clearance between the measurement signal magnetic member 13 and measurement detecting head 18 may be obtained~ and a'so~ ickness of the protective layer 20 as a non-magnetic sheet provided on the surface of the magnetic scale body 14 can be sufficiently accommodated within the aforementioned range of clearance.
In this embodiment again, the frictional surface 14a of the magnetic scale body 14 may be obtained as a uniformly finished plane ~urface. Thus, it is possible to obtain sufficient effect of cleanlng by the scrapers l9A and l9B. In addition, it is possible to obtain an absolute length measurement output on the basis of the information of the point of origin~
The spacer 10 in the embodiment may be formed on a common magnetic plate integral with the measurement signal magnetic member 13. Fig. 5 shows a modification of the magnetic scale device utilizing the magnetic grating formed by the longitudinal magnetic recording as described above. This modification has a structure sonsisting of a scale base 21, a magnetic plate 25 made of barium ferrite and a protective layer 30 made of a non-magnetic sheet. The magnetic grating by the longitudinal recording is selectively provided in a region of the magnetic plate 25 corresponding to the measurement track T ~ , and thus the measurement signal ~67~
magnetic member 23 is formed. The plate 25 is formed in a region corresponding to the origin track TRo with a recess defining an acco~nodating section 26 for the origin signal magnetic merr~er ~2. The origin signal magnetic member 22 is received and secured in the accommodating section 26 formed in the magnetic plate 25 on the scale base 21. A protective layer 30 is provided to cover the entire surface of the magnetic plate 25 and origin signal magnetic member 30, whereby a uniformly finished plane surface can be provided as the frictional surface 24a of the magnetic scale body 24.
While in the above individual embodiments a single origin signal magnetic member is arranged on the scale base, it is also possible to apply the present invention to a length measuring device as shown in Fig. 6, in which a magnetic scale body 32 including a plurality of origin signal magnetic members 32a,32b ... 32n providing information of respective predetermined positions is used to obtain a length measurement output based upon the information of the individual origin points.
Claims (7)
1. A length measuring device comprising a magnetic scale body including at least one origin signal magnetic section and a measurement signal magnetic section forming a magnetic grating, said magnetic scale body having a uniform frictional surface formed over the entire effective length of said scale body, and a detecting head body including an origin detecting head for detecting an origin signal and a measurement detecting head for detecting a measurement signal and provided with scraper means in elastic contact with said frictional surface of said magnetic scale body, said detecting head body being moved relative to said magnetic scale body along said length of the latter.
2. A length measuring device according to claim 1, wherein said scale body has a scale base in which an origin signal magnetic member is buried to form said origin signal magnetic section, and one surface of said scale base including the top surface of said origin signal magnetic member is covered by a measuring signal magnetic member forming said measurement signal magnetic section.
3. A length measuring device according to claim 1, wherein said scale body include a scale base and an origin signal magnetic member and a measuring signal magnetic member are provided on said scale base to define said origin signal magnetic section and said measurement signal magnetic section, respectively and a protective layer consisting of a non-magnetic material is formed to entirely cover a surface of each of said magnetic members.
4. A length measuring device according to claim 3, in which said origin signal magnetic member and said measuring signal magnetic member are arranged side-by-side on said scale base.
5. A length measuring device according to claim 3, in which said origin signal magnetic member and said measuring signal magnetic member are arranged in succession in the direction of said length of the magnetic scale body. _
6. A length measuring device according to claim 1, in which said origin signal magnetic section and said measurement signal magnetic section are arranged side-by-side on said scale body.
7. A length measuring device according to claim 1, in which said origin signal magnetic section and said measurement signal magnetic section are arranged in succession in the direction of the relative movement of said detecting head body and said scale body.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000396520A CA1167545A (en) | 1982-02-18 | 1982-02-18 | Length measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000396520A CA1167545A (en) | 1982-02-18 | 1982-02-18 | Length measuring device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1167545A true CA1167545A (en) | 1984-05-15 |
Family
ID=4122089
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000396520A Expired CA1167545A (en) | 1982-02-18 | 1982-02-18 | Length measuring device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1167545A (en) |
-
1982
- 1982-02-18 CA CA000396520A patent/CA1167545A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |