JP2013063009A - Dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC brushless motor capable of achieving motor cost cutting, prevention of leakage of oil contained in a bearing, and reductions in swing noise and motor thickness.SOLUTION: The DC brushless motor includes: a housing; a porous bearing pressed in the housing and containing oil; a shaft penetrating through the bearing; and a rotor and has no felt on both ends of the bearing. The shaft is rotatably retained on thrust bearings or fixes a disc in the vicinity to a plane of the bearing.

Description

  The present invention relates to a DC brushless motor that is low in price, prevents leakage of oil contained in a bearing, and can reduce swing noise even if it is further thinned. A claw-shaped magnetic pole (pole) consisting of a wound coil and upper and lower yokes surrounding it, with both sides of the upper and lower yokes protruding alternately from above and below, inserted into a cylindrical permanent magnet The present invention relates to a pole type DC brushless motor and a motor fan.

  The DC brushless motor is obtained by replacing the functions of the brush and commutator of a conventional brush motor with a switching element such as a semiconductor and a control circuit for controlling the driving thereof. Compared with a brush motor, the DC brushless motor is superior in that it has a long life, can be miniaturized, and can be assembled into a variety of shapes, is highly efficient and easy to control, and operates more silently. For example, it is rapidly spreading to CD / DVD-ROM drives, hard disks, refrigerators, air conditioners and the like.

  And as claw pole type motors of DC brushless motors, there are products such as MF50E-12 (cooling fan) of Non-Patent Document 1, for example. A cooling fan using a conventional claw pole type DC brushless motor has a structure shown in FIG.

  FIG. 5 is a schematic cross-sectional view of a conventional claw pole type DC brushless motor fan. The claw pole type DC brushless motor fan 21 is press-fitted into the housing 2, the housing 2 formed by cutting, the air core coil 6 wound around a circle disposed outside the housing 2, or the coil 6 wound around a bobbin, and the housing 2. Porous bearing 4 sintered with metal powder, shaft 3 inserted through bearing 4 and rotatably held on thrust bearing 2b, and felt 5 positioned on the flat surfaces at both ends of bearing 4 through shaft 3 An upper yoke 7 fixed to the housing 2 and positioned on the coil 6 and having a magnetic pole 7c (pole) protruding from the side of the coil 6, and an upper yoke fixed to the housing 2 and positioned below the coil 6 on the side of the coil 6 7 includes a lower yoke 7a having a magnetic pole 7c protruding between the magnetic poles 7c, and a cylindrical permanent magnet 9a which is fixed to the shaft 3 and into which the upper and lower yokes 7 and 7a are inserted. A rotor 8 provided, a substrate 8 including an electronic component including a semiconductor element that inserts and fixes the housing 2 and controls the rotation of the shaft 3, and the housing 8 and the thrust bearing 2b are fixed with the substrate 8 interposed therebetween, and the fin 9b is surrounded. And a case 10 having a hole 10a through which it passes.

  The housing 2 is formed by cutting a metal such as free-cutting steel or pure iron. The dimensional accuracy required for the housing 2 is high from the viewpoint of press-fitting of the bearing 4 and control of the lines of magnetic force.

  The bearing 4 is formed by sintering metal powder such as iron-copper powder or copper powder. By sintering, voids (porous) containing lubricating oil are formed. The volume ratio (void ratio) of the gap to the entire conventional bearing 4 is controlled to about 20% by a known technique such as a material, a binder, an additive, and a sintering temperature.

  On the other hand, both ends of the bearing 4 are covered with felt 5 so that oil contained in the bearing 4 does not leak. The felt 5 is a sheet made by compressing fibers and is a so-called nonwoven fabric.

  A conventional claw pole type DC brushless motor fan 21 is configured such that a rotating shaft 3 is inserted into a bearing 4 which is press-fitted into a machined housing 2 and which is press-fitted into a metal sintered and oil-impregnated. The structure includes a felt 5 that prevents leakage of oil-containing oil, and other shapes and configurations are not limited to cooling fans depending on the purpose, and there are various forms. Furthermore, there are some which are used as a mere motor without the fins 9b.

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  However, the conventional housing is required to have a high dimensional accuracy on the inner diameter of the housing because the metal is cut and molded and a bearing is press-fitted. Also, a high dimensional accuracy is required on the outer periphery to magnetically connect the upper and lower yokes. Therefore, the processing cost was high and the unit price of the parts was high.

  Further, in order to prevent leakage of oil contained in the porous bearing, felts that absorb oil are attached to the top and bottom of the bearing as shown in FIG. 5 to increase the unit price of the motor.

  On the other hand, there is a growing need for ultra-thin motor fans. By making the motor fan thinner, the bearing is also thinner. As a result, the length of the sliding portion between the shaft and the bearing is shortened, causing a problem of shaft runout accompanying rotation of the shaft. In particular, shaft shake that occurs when the attitude of the motor fan is changed has become a problem as shaft noise (swing noise).

  Accordingly, the present invention provides a DC brushless motor fan which can reduce the motor unit price, prevent leakage of oil contained in the bearing, reduce swing noise, and reduce the thickness of the DC brushless motor fan. Is intended to provide.

In order to solve the above problems, the present invention provides:
(1)
Porous housing in which metal powder mainly composed of iron powder is sintered, circular air-core coil or coil wound around bobbin disposed outside the housing, and metal powder press-fitted into the housing A porous bearing that is sintered and oil-impregnated, a shaft that is inserted through the bearing and is rotatably supported on a thrust bearing, and a magnetic pole that is fixed to the housing and is positioned on the coil and protrudes from a coil side surface. An upper yoke, a lower yoke fixed to the housing and positioned below the coil and having a magnetic pole projecting between the magnetic poles of the upper yoke on a coil side surface; a cylindrical permanent fixed to the shaft and surrounding the upper and lower yokes A claw pole type DC brushless comprising a rotor having a magnet and fins on the outside, and no felt at both ends of the bearing It has a configuration of Tafan.
(2)
Porous housing in which metal powder mainly composed of iron powder is sintered, circular air-core coil or coil wound around bobbin disposed outside the housing, and metal powder press-fitted into the housing Porous bearings that are sintered and impregnated, a shaft that is rotatably inserted through the bearings, a disk that is fixed to the shaft in the vicinity of the plane of the bearings, and a coil that is fixed to the housing and fixed to the housing An upper yoke having a magnetic pole located above and projecting from the side of the coil; a lower yoke secured to the housing and located below the coil and having a magnetic pole projecting between the magnetic poles of the upper yoke; The rotor is fixed and includes a cylindrical permanent magnet that surrounds the upper and lower yokes, and is provided with a fin on the outside, and has no felt at both ends of the bearing. That was of the claw-pole DC brushless motor fan configuration.
(3)
(2) The flat surface on the disk side of the bearing is provided with a plurality of substantially arc-shaped grooves protruding in the rotation direction of the shaft from the hole of the bearing through which the shaft is inserted toward the side surface. The claw pole type DC brushless motor fan is configured.
(4)
The claw-pole type DC brushless motor fan according to any one of (1) to (3) is characterized in that a clearance ratio of the housing is higher than a clearance ratio of the bearing.
(5)
A porous housing, a circular air-core coil disposed outside the housing or a coil wound around a bobbin, a porous bearing that is sintered and oil-impregnated with metal powder press-fitted into the housing, and An upper shaft having a shaft inserted through a bearing and rotatably held, a disk fixed to the shaft in the vicinity of the plane of the bearing, and a magnetic pole fixed to the housing and positioned on the coil and projecting from a coil side surface. A yoke, a lower yoke which is fixed to the housing and is located below the coil and has a magnetic pole protruding between the magnetic poles of the upper yoke on a coil side surface; a cylindrical permanent magnet which is fixed to the shaft and surrounds the upper and lower yokes A claw pole type DC brushless motor that does not have felt at both ends of the bearing,
The claw pole type DC brushless motor has a configuration in which a plurality of substantially arc-shaped grooves convex in the rotation direction of the shaft are provided in a row on the disk-side plane of the bearing and the hole surface of the bearing.
(6)
A porous housing, a porous bearing that is press-fitted into the housing and impregnated with oil, a shaft that passes through the bearing, and a disk that is fixed to the shaft in the vicinity of the plane of the bearing, DC brushless motor that does not use felt
The DC brushless motor has a configuration in which a plurality of substantially arc-shaped grooves convex in the rotation direction of the shaft are provided in a row on the disk-side plane of the bearing and the inner surface of the hole of the bearing.
(7)
The DC brushless motor according to (6) is provided with a notch on the outer periphery of the surface on the side opposite to the bearing of the disk.
(8)
The bearing includes a sintered porous bearing having a plurality of substantially arc-shaped grooves protruding in the rotation direction of the shaft on an inner surface, and a shaft disposed on a plane opposite to the bearing disposed on an upper plane of the bearing. (6) or (7), characterized in that the non-sinterable metallic second thrust bearing is provided with a plurality of substantially arc-shaped grooves convex in the rotation direction. The configuration is a brushless motor.

  The present invention includes a porous housing obtained by sintering a metal powder containing iron powder as a main component, thereby satisfying the dimensional accuracy required for the housing and temporarily preventing oil from leaking from the bearing. Since it absorbs and replaces the action of the conventional felt, it is not necessary to use the felt used in the conventional claw-pole type DC brushless motor fan, and the housing is not cut, so the claw-pole type DC brushless motor The unit price of fans can be kept low.

  In addition, by fixing a metallic disk to the shaft, a dynamic pressure effect can be obtained in the axial direction, and a long sliding surface can be secured as shown in FIG. Can do. Furthermore, by providing a plurality of substantially arc-shaped grooves that are convex in the direction of rotation of the shaft from the hole of the bearing through which the shaft is inserted to the side surface on the disk-side plane of the bearing, the oil is retained on the bearing side during rotation. To do.

  Moreover, the housing in which the iron powder is sintered becomes a part of the magnetic circuit of the fan motor, and generates torque for rotating the rotor by connecting the upper yoke and the lower yoke with the magnetic circuit.

  If the gap ratio of the housing is higher than the gap ratio of the bearing, the temperature rises when the motor rotates and oil that leaks from the bearing is temporarily absorbed, and when the rotor stops and the temperature of the bearing portion decreases, the capillary tube The phenomenon causes the oil to return to the bearing.

  In addition, by providing a plurality of substantially arc-shaped grooves that protrude in the rotational direction of the shaft in a row on the bearing plane and the inner surface of the bearing, swing noise can be reduced even if the bearing is made thinner, so the motor is made thinner. Can be planned.

  Furthermore, if the bearing is a bearing provided with a groove only on the inner surface and a second thrust bearing provided with a groove on a flat surface, and the second thrust bearing is a metal plate or the like, the swing of the motor is suppressed, swing noise, While ensuring stable rotation of the shaft, it can be made thin and can be provided at a lower cost.

It is a cross-sectional schematic diagram of 1st Embodiment of the claw pole type | mold DC brushless motor fan which is this invention. It is a cross-sectional schematic diagram of 2nd Embodiment of the claw pole type DC brushless motor fan which is this invention. It is an expanded section schematic diagram of a bearing part. It is an expansion schematic diagram of a bearing plane. It is a cross-sectional schematic diagram of a conventional claw pole type DC brushless motor fan. It is a cross-sectional perspective view of a bearing. (A) is the conventional example, and (B) is the third embodiment. It is a partial section perspective schematic diagram of a DC motor using a thinned bearing. It is a longitudinal cross-sectional schematic diagram of the DC motor using the bearing reduced in thickness. It is the decomposition | disassembly partial cross-section perspective schematic diagram (A) of the DC motor using the bearing of other embodiment reduced in thickness, and the one part assembly enlarged view.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic cross-sectional view of a first embodiment of a claw pole type DC brushless motor fan according to the present invention. The claw pole type DC brushless motor fan 1 includes a housing 2a, a coil 6, a bearing 4a, a shaft 3a, an upper yoke 7, a lower yoke 7a, and a rotor 9. Further, as in the prior art, the rotor 9 A substrate 8 on which electronic components including a semiconductor element that controls the rotation of the substrate 8 are mounted, and a case 10 having a hole 10a that accommodates them and allows air to pass therethrough.

  The housing 2a is obtained by molding and sintering a metal powder mainly composed of iron powder into a cylindrical shape. It becomes porous by sintering. The void ratio of the housing 2a (the volume ratio of the gap to the total volume including the gap of the housing 2a × 100) is higher than the void ratio of the bearing 4a (the volume ratio of the gap to the total volume including the gap of the bearing 4a × 100). Is desirable. If the gap ratio of the bearing 4a is 20%, the gap ratio of the housing 2a is desirably 25% or more, and preferably 30% or more. The difference between the gap ratios of the housing 2a and the bearing 4a is better.

  If the clearance ratio of the housing 2a is higher than the clearance ratio of the bearing 4a, the housing 2a temporarily absorbs oil leaking from the bearing 4a when the temperature rises during motor rotation, and the rotor 9 stops and the bearing 4a portion When the temperature decreases, the oil returns to the bearing 4a by capillary action. As a result, by sintering the housing 2a, there is no need to provide the felt 5 that absorbs the oil leaking from the bearing 4a as in the prior art.

  The air-core coil 6 wound in a circle or the coil 6 wound on a bobbin is disposed outside the housing 2a. The bearing 4a is press-fitted into the housing 2a, and is molded by sintering a metal powder, for example, an iron-copper powder or a copper powder, as in the conventional case. By sintering, voids containing lubricating oil are formed. The voids may be about 20% as in the conventional case, and are controlled by known techniques such as materials, binders, additives, and sintering temperature. It is desirable that the air gap ratio is lower than the housing 2a. In order to make the motor fan thinner, the bearing 4a is also thinner than the conventional bearing 4.

  The shaft 3a is inserted into the bearing 4a and is rotatably held on the thrust bearing. The thrust bearing 2b is a bearing that receives force (thrust, thrust) acting in the axial direction of the rotating body.

  The upper yoke 7 has a magnetic pole 7b that is fixed to the housing 2a, is positioned on the coil 6 and protrudes from the side surface of the coil 6. On the other hand, the lower yoke 7a is fixed to the housing 2a, is positioned below the coil 6, and has a magnetic pole 7b protruding between the magnetic poles 7b of the upper yoke 7 on the side of the coil 6.

  The rotor 9 is fixed to the shaft 3a, includes a cylindrical permanent magnet 9a that surrounds the upper and lower yokes 7 and 7a, is provided with fins 9b on the outside, and rotates together with the shaft 3a.

  The claw pole type DC brushless motor fan 1 configured as described above can push the motor unit price low without using the felt 5.

  FIG. 2 shows a schematic sectional view of a second embodiment of the claw pole type DC brushless motor according to the present invention. The claw pole type DC brushless motor fan 11 is provided with a disk 2d which is in contact with the plane of the bearing 4a and fixed to the shaft 3a except for the thrust bearing 42b in the first embodiment. Therefore, the description other than the disk 2d is omitted.

  When the rotor 9 rotates, a dynamic pressure is generated between the rotor 9 and the disk 2d by the action of a groove formed on the end surface of the bearing 4a, and the disk 2d is rotated several μm above the bearing 4a. Therefore, a sliding surface 4b longer than the conventional one is formed not only in the circumferential direction of the shaft 3a but also in the direction perpendicular to the shaft 3a with the bearing 4a (see FIG. 3). As a result, swing noise can be reduced. As the material of the disk 2d, metal, resin, ceramic or the like can be used.

  Further, as shown in FIG. 4, a substantially arc-shaped groove convex in the rotation direction of the shaft 3a from the hole 4c of the bearing 4a passing through the shaft 3a toward the outer surface may be formed in the plane on the disk 2d side of the bearing 4a. As an example of the substantially arc-shaped groove, the planar shape of the groove in FIG. 4 (A) is an arc-shaped groove 4d that is convex in the rotational direction of the shaft 3a, and the planar shape of the groove in FIG. 4 (B) is in the rotational direction of the shaft 3a. The convex V-shaped groove 4e is illustrated.

  Thus, by providing a substantially arc-shaped groove having a convex surface in the rotation direction of the shaft 3a on the bearing 4a plane, a dynamic pressure is generated between the bearing 4a plane and the disk 2d during rotation, and the disk 2d floats. The rotor 9 can be rotated in the state. In FIG. 2, the disk 2d is disposed on the upper side of the bearing 4a, but may be disposed on the lower side of the bearing 4a.

  The claw pole type DC brushless motor fan 11 thus configured can prevent oil leakage and can reduce the motor unit price without using the felt 5. Furthermore, swing noise can be further suppressed than when the thrust bearing 2b is used. Therefore, it contributes to the thinness of the motor. And it is applicable also to motors other than a motor fan.

  FIG. 6A is a schematic cross-sectional perspective view of the conventional bearing 4 in the height direction of the conventional bearing 4 and FIG.

  In the conventional bearing 4, the flat surface 4f is flat, and a plurality of V-shaped grooves 4h that protrude in the rotational direction of the shaft 3a (white broken arrow) are formed in two rows in the upper and lower rows and one row on the inner surface 4g. Yes. Thereby, the stable rotation of the shaft 3a is maintained. Therefore, in the conventional bearing 4, the length of the shaft 3a insertion direction cannot be shortened. Therefore, it has been difficult to reduce the thickness of the motor.

  On the other hand, in the bearing 14 shown in FIG. 6B, a V-shaped groove 14b that protrudes in the plane 14a in the direction of rotation of the shaft 3a (white broken arrow) and the inner surface 14c also in the direction of rotation of the shaft 3a. A convex V-shaped groove 14d is provided. By providing such grooves 14b and 14c, swing noise is suppressed and stable rotation of the shaft 3a is ensured even if the height of the bearing 14 in the direction of the shaft 3a (double arrow in the figure) is reduced. Therefore, the motor can be thinned.

  As shown in FIG. 7, the DC brushless motor 15 using the thinned bearing 14 according to the present invention is a bearing 14 press-fitted into a housing 2a fitted to a housing 16 or a case 10 if it is a motor fan. And a disk 17 fixed to the shaft 3 a in the vicinity of the plane of the bearing 14. The shaft 3a is fixed to the rotor 9, or is inserted into the rudder 16 side so as to be rotatable and not swingable.

  As shown in FIG. 8A, by providing a notch 17a on the outer periphery of the surface of the disk 17 on the side opposite to the bearing 14, the surface of the notch 17a has an outward (arrow) centrifugal force due to the rotation of the disk 17a. And the oil contained in the housing 2a is prevented from being transmitted to the rotor 9 side, and the oil is prevented from scattering.

  If the notch 17a is not formed on the outer periphery of the surface opposite to the bearing 14 as in the disk 17c shown in FIG. 8B, the oil contained in the housing 2a is transmitted to the rotor 9 side, and the oil is generated by the rotation of the rotor. The life of the motor may be shortened by scattering due to centrifugal force and depletion of oil in the bearing 14. Therefore, it is desirable to provide the notch 17a like the disk 17.

  As shown in FIG. 9, the bearing 4a is flat without integrating the bearings, the bearing 18a is provided with a groove 14d on the inner surface 14c, and the second thrust bearing 18b is located above the bearing 18a and is inserted into the shaft 3a. Even when divided into two, the same effects as the bearing 14 are obtained in swing control, swing noise reduction, and stable shaft rotation.

  The second thrust bearing 18b is provided with a groove 14b provided on the flat surface 14a of the bearing 14 on the flat surface 18c on the side opposite to the bearing 18a. The second thrust bearing 18b may be formed by sintering and molding metal powder or the like in the same manner as the bearings 4a, 14 and 18a, and may be an oil-impregnated material on the bolus, or provided with a groove 14b on a simple metal plate or the like. May be.

  By using the second thrust bearing 18b as a separate bearing, the material is not limited and the productivity is high, and a thin DC brushless motor can be provided at a lower cost.

  Further, since the second thrust bearing 18b can be assembled separately from the radial bearing 18a, the squareness accuracy of the radial bearing 18a and the second thrust bearing 18b can be improved in the assembly process. With the integrated bearing 14, when the squareness accuracy is poor, stable rotation of the shaft 3a is not ensured, and therefore stable rotation of the shaft 3a cannot be ensured. Therefore, the product yield improves by making it a separate body.

DESCRIPTION OF SYMBOLS 1 Claw pole type DC brushless motor fan 2 Housing 2a Housing 2b Thrust bearing 2d Disk 3 Shaft 3a Shaft 4 Bearing 4a Bearing 4b Sliding surface 4c Hole 4d Groove 4e Groove 4f Plane 4g Inner side surface 4h Groove 5 Felt 6 Coil 7 Upper yoke 7a Lower yoke 7b Magnetic pole 8 Substrate 9 Rotor 9a Permanent magnet 9b Fin 10 Case 11 Claw pole type DC brushless motor fan 14 Bearing 14a Plane 14b Groove 14c Inner surface 14d Groove 15 DC brushless motor 15a DC brushless motor 16 Housing 17 Disc 17a Notch 17b Space 17c Disk 18 DC brushless motor 18a Bearing 18b Second thrust bearing 18c Plane 21 Claw pole type DC brushless motor fan

Claims (8)

A porous housing obtained by sintering metal powder mainly composed of iron powder;
A circular air-core coil or a coil wound around a bobbin disposed outside the housing;
Porous bearings that are sintered and oil-impregnated with metal powder pressed into the housing;
A shaft inserted through the bearing and rotatably held on a thrust bearing;
An upper yoke having a magnetic pole fixed to the housing and positioned on the coil and protruding from a side surface of the coil;
A lower yoke having a magnetic pole fixed to the housing and positioned below the coil and projecting between the magnetic poles of the upper yoke on a coil side surface;
A claw pole type DC brushless motor comprising a rotor having a cylindrical permanent magnet fixed to the shaft and surrounding the upper and lower yokes, and having fins on the outside, and no felt at both ends of the bearing. fan. A porous housing obtained by sintering metal powder mainly composed of iron powder;
A circular air-core coil or a coil wound around a bobbin disposed outside the housing;
Porous bearings that are sintered and oil-impregnated with metal powder pressed into the housing;
A shaft inserted through the bearing and rotatably held;
A disc fixed to the shaft in proximity to the plane of the bearing;
An upper yoke having a magnetic pole fixed to the housing and positioned on the coil and protruding from a side surface of the coil;
A lower yoke having a magnetic pole fixed to the housing and positioned below the coil and projecting between the magnetic poles of the upper yoke on a coil side surface;
A claw pole type DC brushless motor comprising a rotor having a cylindrical permanent magnet fixed to the shaft and surrounding the upper and lower yokes, and having fins on the outside, and no felt at both ends of the bearing. fan. The flat surface on the disk side of the bearing is provided with a plurality of substantially arc-shaped grooves convex in the rotation direction of the shaft from a hole of the bearing through which the shaft is inserted toward a side surface. Claw pole type DC brushless motor fan. The claw pole type DC brushless motor fan according to any one of claims 1 to 3, wherein a clearance ratio of the housing is higher than a clearance ratio of the bearing. A porous housing;
A circular air-core coil or a coil wound around a bobbin disposed outside the housing;
Porous bearings that are sintered and oil-impregnated with metal powder pressed into the housing;
A shaft inserted through the bearing and rotatably held;
A disc fixed to the shaft in proximity to the plane of the bearing;
An upper yoke having a magnetic pole fixed to the housing and positioned on the coil and protruding from a side surface of the coil;
A lower yoke having a magnetic pole fixed to the housing and positioned below the coil and projecting between the magnetic poles of the upper yoke on a coil side surface;
A claw pole type DC brushless motor that is fixed to the shaft and includes a rotor having a cylindrical permanent magnet surrounding the upper and lower yokes, and has no felt at both ends of the bearing;
A claw pole type DC brushless motor, wherein a plurality of substantially arc-shaped grooves convex in the rotational direction of the shaft are provided in a line on the disk-side plane of the bearing and the hole surface of the bearing. A porous housing, a porous bearing that is press-fitted into the housing and impregnated with oil, a shaft that passes through the bearing, and a disk that is fixed to the shaft in the vicinity of the plane of the bearing, DC brushless motor that does not use felt
A DC brushless motor, wherein a plurality of substantially arc-shaped grooves convex in the rotation direction of the shaft are provided in a row on the disk-side plane of the bearing and the inner surface of the hole of the bearing. The DC brushless motor according to claim 6, wherein a notch is provided on an outer periphery of a surface of the disk on the side opposite to the bearing. The bearing,
A sintered porous bearing having a plurality of substantially arc-shaped grooves that are convex in the rotational direction of the shaft on the inner surface;
The non-sinterable metallic second thrust bearing is provided with a plurality of substantially arc-shaped grooves that are arranged on the upper plane of the bearing and that are convex in the rotational direction of the shaft on the non-bearing plane. The DC brushless motor according to claim 6 or 7, characterized by the above.

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