Source: https://patents.google.com/patent/US7633189?oq=5%2C987%2C610
Timestamp: 2018-05-26 05:22:53
Document Index: 171370038

Matched Legal Cases: ['Application No. 2004', 'Application No. 2004', 'Application No. 2004', 'art 10', 'art 10', 'art 10', 'art 20', 'art 10', 'art 10', 'art 10', 'art 10', 'art 10', 'art 1']

US7633189B2 - Cylinder-type linear motor and moving parts thereof - Google Patents
Cylinder-type linear motor and moving parts thereof Download PDF
US7633189B2
US7633189B2 US12098129 US9812908A US7633189B2 US 7633189 B2 US7633189 B2 US 7633189B2 US 12098129 US12098129 US 12098129 US 9812908 A US9812908 A US 9812908A US 7633189 B2 US7633189 B2 US 7633189B2
US12098129
US20080246351A1 (en )
Takao Iwasa
Hirobumi Satomi
The present invention provides a cylinder-type linear motor capable of shortening the total motor length with respect to a predetermined stroke length and capable of being operated as a brushless DC motor without a sensor means for sensing the position of a moving part being added in the axial direction. The present invention also provides a moving part of said cylinder-type linear motor, which can improve the magnetic flux density distribution waveform near both end portions of the moving part assembly and can improve the thrust characteristic by bringing the magnetic flux density distribution waveform closer to a cosine waveform and by increasing the amplitude of cosine waveform.
This application is a divisional application of U.S. application Ser. No. 11/197,014 filed on Aug. 4, 2005, now U.S. Pat. No. 7,378,765, and claims priority from Japanese Patent Application No. 2004-231993; filed Aug. 9, 2004; Japanese Patent Application No. 2004-253765; filed Sep. 1, 2004; and Japanese Patent Application No. 2004-253766; filed Sep. 1, 2004, the disclosures of which are incorporated by reference herein in their entirety.
An axial length M of a moving part core section is longer than an axial length K of a fixed core section, and therefore is an axial length in which the moving part and the fixed part face each other, namely, a thrust contribution length K. Also, a stroke length S is expressed by (M−K). From FIG. 11, the travel range length of the moving part is expressed by (K+2S), namely, (thrust contribution length+2×stroke length S). The total motor length is set so as to satisfy the travel range length of the moving part. As the related art, Japanese Patent Provisional Publication No. 7-107732 and Japanese Patent Provisional Publication No. 5-15139 can be cited.
For the linear motor having the above-described conventional construction, in order to provide a predetermined stroke S, it is necessary to set the total length of the motor so as to satisfy the travel range length (thrust contribution length+2×stroke length S) of the moving part, which results in a problem of greater total motor length. Also, since the above-described motor having the conventional construction is of a permanent magnet type, it can be operated as a brushless DC motor in principle. For this purpose, however, sensor means for sensing the position of moving part must be provided separately so as to be adjacent to the fixed part section in the axial direction. In this case, there arises a problem in that the total motor length increases further.
To solve the above problems, the present invention provides a cylinder-type linear motor including a fixed part including a coil assembly having a plurality of (n number of) ring-shaped coils arranged in the axial direction to form a cylindrical space, and a yoke member made of a magnetic material, which is provided on the outer periphery side of the coil assembly; and a moving part including a linear motion shaft provided on the axis line of the fixed part so as to be capable of reciprocating in the axial direction, and a permanent magnet assembly having one or more permanent magnets magnetized in the axial direction, which is provided on the linear motion shaft, characterized in that when the axial length of the ring-shaped coil is taken as C, the axial length of the permanent magnet assembly as M, and the outside diameter thereof as D, a stroke S is equal to or smaller than (n×C−M), the axial length Y of the yoke member is set equal to or larger than (M+S+0.8×D), and the ring-shaped coils are arranged in a predetermined phase order and the ring-shaped coils of the same phase are connected to each other to form one phase winding.
The present invention provides a moving part of a cylinder-type linear motor, including a linear motion shaft which is arranged on an axis line of a cylindrical fixed part so as to reciprocate on the axis line in the axial direction; and a permanent magnet assembly which is provided on the linear motion shaft and is configured so that a plurality of permanent magnets magnetized in the axial direction are disposed so that the end faces thereof face to each other, characterized in that a unit is formed by a first permanent magnet magnetized in a first axial direction and second and third permanent magnets magnetized in the direction opposite to the first axial direction, which are arranged on both sides of the first permanent magnet; one or more units are arranged in series in the axial direction to form the permanent magnet assembly; when the first to third permanent magnets are arranged in the order of the second, first and third permanent magnets from the left, a distance between the left-hand side end face of the second permanent magnet and the right-hand side end face of the third permanent magnet is set at 2×L, and a distance between a first central position between the right-hand side end face of the second permanent magnet and the left-hand side end face of the first permanent magnet and a second central position between the right-hand side end face of the first permanent magnet and the left-hand side end face of the third permanent magnet is set at L.
FIG. 1 is a longitudinal sectional view showing an embodiment of a cylinder-type linear motor in accordance with the present invention;
Preferred embodiments of the present invention will now be described exemplarily and in detail with reference to the accompanying drawings.
FIG. 3 is a view schematically showing the relationship of a detent thrust depending on the relationship between a travel range length (M+S) of the moving part 10 and a length Y of the cylindrical yoke 21. In FIG. 3, the center in the axial direction of the permanent magnet assembly 15 is taken as an origin of position. From FIG. 3, it can be seen that a detent thrust that draws the moving part 10 into the yoke is generated near both ends of the stroke. Also, it can be seen that if the length Y of the cylindrical yoke 21 is set so as to be equal to or greater than a certain value Yo, the detent thrust can be kept at a negligible value in the travel range length (M+S) of the moving part 10. A yoke projecting dimension B at the time when Y is equal to Yo depends on the outside diameter D of the permanent magnet, and is expressed as B=kD. It is determined analytically that k is proper when it takes a value of about 0.4. Therefore, Yo=M+S+2×B=M+S+0.8×D.
From the above description, as shown in FIG. 2, when the axial length of the permanent magnet assembly 15 is taken as M, the outside diameter thereof as D, and the stroke length as S, the length Y of the cylindrical yoke 21 is set at a value equal to or larger than (M+S+0.8×D). By doing this, the detent thrust generated at both ends of stroke at the time of de-energization can be kept at a negligible value. When the pitch between the ring-shaped coils 22, 23, . . . , 27 is taken as C, since the number n of the ring-shaped coils 22, 23, . . . , 27 is six, an axial length K of the fixed part 20 is 6C. In this case, the thrust contribution length is M. Also, the stroke length S can take a value equal to or smaller than (K−M), namely, (6C−M). In FIG. 2, the number of the ring-shaped coils 22, 23, . . . , 27 is six. However, by increasing the number of the ring-shaped coils 22, 23, . . . , 27 to seven or decreasing to five, for example, the stroke length S can be increased or decreased with the coil pitch C being a unit to (7C−M) or (5C−M). Since the stroke length S does not depend on the length M of the permanent magnet assembly 15, it can be seen that even if the stroke length S is increased, the inertia moment of the moving part 10 does not increase. Also, since the travel range length of the moving part 10 is (thrust contribution length+stroke length S), the total motor length can be shortened by the stroke length S as compared with the conventional example.
FIG. 4 is a view showing an axial distribution waveform of a radial component of magnetic flux density due to the moving part 10 in accordance with this embodiment and the permanent magnet assembly 15 corresponding to the moving part 10. It can be seen that in the range of the axial length M of the permanent magnet assembly 15, the distribution waveform of magnetic flux density can be approximated as a waveform in which a DC component is added to a cosine component. Specifically, when the axial position with the axial center position of the permanent magnet assembly 15 being the origin is taken as (x), the magnetic flux density B(x) is expressed as B(x)=B1×cos(πx/L)+B0, wherein L is a magnetic pole pitch of moving part. The output voltage of the sensor means 41 is also a voltage proportional to this, so that the position of the moving part 10 can be read by utilizing the same relational expression as described above.
When the axial length of the first permanent magnet 3 is taken as L, the distribution waveform of magnetic flux density formed by the first permanent magnet 3 is represented by a curve W shown in FIG. 8. The peaks of magnetic flux density occur at the axial positions of ±L/2, and the magnetic pole pitch (distance between the N and S poles) P is equal to L. At this time, the magnetic flux density at the axial positions of ±L is not zero, but has a value of ±K as shown in FIG. 8. If the axial lengths of the second and third permanent magnets 2 and 4 are set at L/2 at this time, the magnetic flux distribution formed by the second permanent magnet 2 is represented by a curve X, the peaks thereof occurring at the axial positions of (−L) and (−L/2).
Also, the magnetic flux distribution formed by the third permanent magnet 4 is represented by a curve Y, the peaks thereof occurring at the axial positions of (L) and (L/2). If the outside diameters of the second and third permanent magnets 2 and 4 are made smaller than the outside diameter of the first permanent magnet 3, the cross-sectional areas of the second and third permanent magnets 2 and 4 become smaller than the cross-sectional area of the first permanent magnet 3. Further, the distance between the second and third permanent magnets 2 and 4 and the sensor means becomes longer than in the case of the first permanent magnet 3. By these two facts, the peak values of the second and third permanent magnets 2 and 4 can be made smaller than the peak values of the first permanent magnet 3, so that the outside diameters thereof can be adjusted so that the peak values are substantially close to the values of ±K.
However, in the cylinder-type linear motor having the above-described moving part construction, as shown in FIG. 4, the magnetic flux density distribution near both end portions of the moving part assembly greatly deviates from a cosine waveform, so that the thrust characteristic is sometimes deteriorated. Also, there arises a problem in that the range in which the aforementioned approximate expression of B(x)=B1×cos(πx/L)+B0 can be applied is limited to the range of 2×L shown in the figure.
In FIGS. 9 and 10, a moving part 1 includes the linear motion shaft 11 reciprocating in the axial direction; a pair of permanent magnets 2 and 4 consisting of the permanent magnet 2 magnetized in the axial direction (left to right) and the permanent magnet 4 magnetized in the opposite direction (right to left), which is arranged so as to face to the permanent magnet 2; the paired fixing ring members 6 and 7 which are brought into contact with both end faces of the paired permanent magnets 2 and 4 and are fixed on the linear motion shaft 11; a pair of ring-shaped permanent magnets 8 and 9 which are provided so as to be fitted on or brought into contact with the outer peripheral surfaces of the fixing ring members 6 and 7. The paired ring-shaped permanent magnets 8 and 9 are magnetized in the radial direction so that the polarity of outer peripheral surface is different from the polarity of the opposed surfaces of the paired permanent magnets 2 and 4. Also, the distance between the central positions of the axial length of the ring-shaped permanent magnets 8 and 9 is set at 2×L, and the outside diameters thereof are set so as to be equal to the outside diameters of the paired permanent magnets 2 and 4.
US12098129 2004-08-09 2008-04-04 Cylinder-type linear motor and moving parts thereof Expired - Fee Related US7633189B2 (en)
JP2004-231993 2004-08-09
JP2004231993A JP4551157B2 (en) 2004-08-09 2004-08-09 Cylinder type linear motor
JP2004-253765 2004-09-01
JP2004253766A JP2006074882A (en) 2004-09-01 2004-09-01 Mover of cylinder type linear motor
JP2004253765A JP2006074881A (en) 2004-09-01 2004-09-01 Mover of cylinder type linear motor
JP2004-253766 2004-09-01
US11197014 US7378765B2 (en) 2004-08-09 2005-08-04 Cylinder-type linear motor and moving part thereof
US12098129 US7633189B2 (en) 2004-08-09 2008-04-04 Cylinder-type linear motor and moving parts thereof
US20080246351A1 true US20080246351A1 (en) 2008-10-09
US7633189B2 true US7633189B2 (en) 2009-12-15
ID=35756701
US11197014 Expired - Fee Related US7378765B2 (en) 2004-08-09 2005-08-04 Cylinder-type linear motor and moving part thereof
US12098171 Active US7989994B2 (en) 2004-08-09 2008-04-04 Cylinder-type linear motor and moving part thereof
US12098148 Abandoned US20080185982A1 (en) 2004-08-09 2008-04-04 Cylinder-Type Linear Motor and Moving Part Thereof
US12098129 Expired - Fee Related US7633189B2 (en) 2004-08-09 2008-04-04 Cylinder-type linear motor and moving parts thereof
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