CN101005232A - Stepping motor - Google Patents

Abstract

A stepping motor includes: a stator having main magnetic poles each having small stator teeth on its tip, a core-back portion that connects outer portions of the poles, and windings wound around the poles; and two sets of rotor units that are arranged in an axial direction and face the stator with an air gap therebetween. Each rotor unit consists of two rotor cores that are separated in the axial direction and a magnet sandwiched thereby and magnetized in the axial direction. Each rotor core has small rotor teeth around its outer surface. The rotor cores of each rotor unit are deviated by 1/2 pitch of the small rotor teeth, and the two rotor units are arranged to make the magnetic polarities of the small rotor teeth of the adjacent two rotor cores identical. A magnet thickness Tm and a rotor core thickness Tc satisfy Tm/Tc= 0.25-0.45.

Description

Stepping motor

Technical field

The present invention relates to employed hybrid step motor in the OA equipment of processing images such as facsimile machine, ink-jet printer, laser printer or photocopier (below be referred to as motor).

Background technology

People require employed motor in above-mentioned each OA equipment to reduce for not only realizing the cost under the absolute condition, and realize low vibration, low noise.

No. 6781260 communiques of United States Patent (USP) disclose a kind of vibration less, electric machine structure that torque is big.The following configuration of disclosed electric machine structure in this communique and constituting: be wound with in the stator of coil, have two groups by a pair of rotor core clamping chain annularly on its plane by the rotor set of the magnetized magnet of one pole, and motor shaft installed as core so that the pole magnetization of magnet same extremely relative, and the polarity of the little tooth of above-mentioned two groups of rotor cores that adjoin each other is mutually the same.In the electric machine structure of this mode, compare with existing two rotor core structures, the attraction radially of four rotor cores is disperseed balance and is not had unbalanced force of the breath, and then vibration and the noise that causes owing to gaps such as bearings advantageously reduces than existing equipment.In addition, compare with the motor of existing same structure, this stepping motor can obtain the torque of about twice in theory.

Generally, in such stepping motor, be necessary to allow the user select motor torque according to the loading condition of using serially.And, therefore make the radial dimension of motor constant, axial length is changed, so that situation about being taken place as the output torque of the motor of purpose is a lot.As everyone knows, in existing general motor, there is the residual magnetic flux density Br of magnet and only magnetic flux distribution in by the magnetic circuit of the structures shape of rotor core and stator core.

But, disclosed stepping motor in No. 6781260 communiques of United States Patent (USP), be to have two groups of rotor set that on the magnet plane, constituted by link-like ground by the magnetized magnet of one pole, and the structure that does not have in the prior art that motor shaft is upwards installed in same extremely relative mode with the pole magnetization of magnet, and only magnetic circuit is not analyzed.

In addition, real opening the stepping motor that remaining magnetic flux density is little, use the ends of the earth stator structure of a plurality of ferrite lattices formations has been proposed in the clear 52-59212 communique.

But, open in the clear 52-59212 communique in fact,, there is not professor how just can obtain only magnetic circuit about the record of magnetic circuit yet.

On the other hand, for this characteristic is provided, nearly all stepping motor gets the very narrow and small 0.05mm that is with the air-gap setting of the inner peripheral surface on the little tooth outer peripheral face of rotor and stator main pole top.Therefore, on the axiality of circularity, rotor portions outer peripheral face and the motor shaft of rotor portions, just require high precision, in the prior art be with the central layer that forms by punching press overlapping and integrated after, the little tooth outer peripheral face of attrition process rotor portions and the circularity and the axiality that obtain stipulating.

In addition, similarly obtain the circularity of the stator inner peripheral surface of very high degree of precision, implement to be called as the polishing processing of honing.By such processing method, the little tooth outer peripheral face of rotor and the air gap of stator inner peripheral surface just remain on about 0.05mm.

In addition, produce burr when the little tooth outer peripheral face of attrition process rotor portions, burr comes off and snaps in rotor in the rotation, becomes the reason of motor-locking.Therefore, when the little tooth outer peripheral face of attrition process rotor portions, make the processing that does not produce burr on the outer peripheral face of rotor portions.As this processing method, also have coat on the outer peripheral face of rotor portions be used to prevent the resin that burr disperses and the method for the back attrition process rotor portions outer peripheral face that makes it to harden and behind the outer peripheral face of attrition process rotor portions, utilize spray to handle only, polishing is hung, the method for hydraulic pressure etc.

Like this, for the little tooth outer peripheral face of rotor and and the air gap of stator inner peripheral surface remain on about 0.05mm, the factor that the surface treatment of honing processing of attrition process rotor portions outer peripheral face etc. and stator inner peripheral surface etc. and machined burrs scheme etc. increase cost is many.

Therefore, open to disclose in the 2005-6375 communique the spy and have the central layer of a plurality of little teeth and the manufacture method that stacked a plurality of central layer constitutes rotor portions as being formed on the neighboring by the punch process that adopts stamping machine, carry out punch process with the first step that forms little tooth cave with cooperate two stages of second step that the outer peripheral face of little tooth stretches by the shape that cooperates little tooth inner peripheral surface, prevent the burr (グ レ) in little increment face, and do not need the technology of the attrition process of rotor portions outer peripheral face.

But, open in the technology of 2005-6375 communique the spy, though do not need attrition process,, still cause cost to rise owing to increased punch process in second stage.

In addition, be in the stepping motor of 0.05mm at the air gap of standard, with respect to produce torque stator and bitrochanteric diameter to attraction very big, and become the exciting force source of motor.

Open in the 2000-197335 communique the spy,, carried out motion with regard to the circumferential configuration of the configuration of the pillar of all magnetic poles and little tooth portion as the noise of the motor that possesses square stator and the improvement of vibration.

But method motor shape applicatory and size that the spy opens in the 2000-197335 communique are restricted, and be impracticable.

Further, disclosed stepping motor has illustrated that also the air gap of the inner peripheral surface on the little tooth outer peripheral face of rotor core and stator main pole top generally is about 0.05mm in No. 6781260 communiques of above-mentioned United States Patent (USP), and need be used for keeping than the highland surface treatment of the circularity of rotor core and stator.

Summary of the invention

First purpose of the present invention is, is prerequisite with disclosed electric machine structure in No. 6781260 communiques of United States Patent (USP), in order to realize only magnetic flux distribution, provides the new benchmark only design parameter as motor.

Second purpose of the present invention provides the surface treatment of the attrition process of not carrying out the rotor outer peripheral face etc. and stator inner peripheral surface, does not increase the number of steps of punch process simultaneously, and the stepping motor of high torque (HT) and low vibration is provided.

Stepping motor according to first form of the present invention, in order to realize above-mentioned first purpose, this motor has a plurality of little teeth on the top of the outstanding utmost point portion of extending from a plurality of main poles, and by having the stator of the core back that links this main pole periphery integratedly with the coil that on each main pole, is wound with, with by air gap and the two group rotor groups that are disposed at vertically on this stator constitute, this rotor set constitutes by spaced two rotor cores vertically with by the magnetized vertically magnet of these two rotor core clampings, described each rotor core has a plurality of little teeth at its outer peripheral face, two rotor cores of described each group are mutually with the configuration of staggering of 1/2 pitch of the little tooth of circumferencial direction, and the polarity of the little tooth of the rotor core that described two groups adjoin each other disposes mutually the samely, it is characterized in that the relation of magnet thickness Tm and rotor core thickness T c is Tm/Tc=0.25～0.45.

In addition, in above-mentioned first form, the motor of the little tooth of preferred rotor peakflux density radially is 1.4～1.7T, and further, the peakflux density difference of axial both ends of stator main pole and central portion is 0.75～0.85T.

Above-mentioned condition is to calculate magnetic flux density, interlinkage flux, back electromotive force, torque etc. by employing ternary magnetic field analysis, and utilizes this value search to realize that the result of the parameter of breakdown torque derives.The result, the relation of magnet thickness Tm and rotor core thickness T c is Tm/Tc=0.25～0.45, the peakflux density of the little tooth of rotor is 1.4～1.7T, stator core shaft is 0.75～0.85T to the peakflux density difference of both ends and central portion, by do not decide magnet thickness and rotor core thickness can obtain back electromotive force the biglyyest.

It is 4 or 8 two-phase induction motor that said structure goes for the main pole number, and perhaps the main pole number is 3 or 6 three phase electric machine.

Its result utilizes first form of the present invention when the HB type stepping motor of design high de-agglomeration ability, cooperate the total length of motor, can most suitably set the relation of magnet thickness and rotor core thickness, and it is maximum that the back electromotive force that can design becomes.In addition, the residual magnetic flux density of link-like magnet can be used the good magnet of for example ferritic ratio of performance to price during smaller or equal to 0.5T expeditiously.

Stepping motor with second morphologic correlation of the present invention, in order to realize above-mentioned second purpose, this motor has a plurality of little teeth on the top of the outstanding utmost point portion of extending from a plurality of main poles, and connect the core back of this main pole periphery and the stator that on each main pole, is wound with coil by having one, with by air gap and the two group rotor groups that are configured to this stator vertically constitute, this rotor set constitutes by spaced two rotor cores vertically with by the magnetized vertically magnet of these two rotor core clampings, described each rotor core has a plurality of little teeth at its outer peripheral face, two rotor cores of described each group are mutually with the configuration of staggering of 1/2 pitch of the little tooth of circumferencial direction, and the polarity of the little tooth of the rotor core that described two groups adjoin each other disposes mutually the samely, it is characterized in that the air gap of the little tooth outer peripheral face of rotor core and stator main pole top inner peripheral surface is 0.06～0.08mm.

According to said structure, just can set to such an extent that greatly need not reduce torque than existing 0.05mm air gap, desired circularity is relaxed, thus do not need the grinding of rotor core and stator and remove the surface treatments such as burr of accompanying with it, and can reduce the processing cost of motor.In addition,, the gear forces of rotation direction can be reduced, and the vibration of motor can be reduced significantly along with the increase of air gap.

In above-mentioned structure, preferably the length with the circular arc of the top ends of the outstanding utmost point portion of each main pole of stator is made as L, the width of described main pole coil installation portion is made as W, and then the value of L/W is smaller or equal to 2.9, and the angle θ of the root of the main pole and the outstanding utmost point is 95 degree＜θ＜120 degree.

By satisfying above-mentioned condition, suppress displacement corresponding to the radial attraction force that affacts little tooth, be given for the size of the outstanding utmost point portion of only stator that guarantees coil space factor, thereby can realize high efficiency and low vibrationization.

Description of drawings

Fig. 1 is the longitdinal cross-section diagram of the stepping motor of first embodiment of the invention;

Fig. 2 A, 2B are the front elevations that the relation of the rotor core of two-phase four utmost point stepping motors of first embodiment of the invention and stator core is shown;

Fig. 3 is the side view of rotor set that the stepping motor of first embodiment of the invention is shown;

Fig. 4 is the longitdinal cross-section diagram that illustrates according to the radial load of stepping motor of the present invention;

Fig. 5 is the chart of characteristic that the stepping motor of first embodiment of the invention is shown;

Fig. 6 is the chart of characteristic that the stepping motor of first embodiment of the invention is shown;

Fig. 7 is the chart of characteristic that the stepping motor of first embodiment of the invention is shown;

Fig. 8 is the chart of characteristic that the stepping motor of first embodiment of the invention is shown;

Fig. 9 is the chart of vibration characteristics that the stepping motor of first embodiment of the invention and existing example is shown;

Figure 10 is the variation that illustrates as first embodiment of the invention, i.e. the front elevation of the relation of the rotor core of two-phase ends of the earth stepping motor and stator core;

Figure 11 is the variation that illustrates as first embodiment of the invention, i.e. the front elevation of the relation of the rotor core of three-phase three utmost point stepping motors and stator core;

Figure 12 A-12G illustrates the stator of analysis condition of stepping motor of second embodiment of the invention and comparative example and the key diagram of rotor;

Figure 13 illustrates the air gap of stepping motor of second embodiment of the invention and the figure of motor characteristic;

Figure 14 is the figure of little tooth displacement that the stepping motor of second embodiment of the invention is shown;

Figure 15 is the figure of vibration characteristics that the stepping motor of second embodiment of the invention is shown.

Embodiment

Stepping motor about the embodiment of the invention will be described below with reference to the accompanying drawings.Disclosed structure is identical in No. 6781260 communiques of the basic structure of the stepping motor of each embodiment and above-mentioned United States Patent (USP).In addition, first embodiment is corresponding with above-mentioned first form, and second embodiment is corresponding with above-mentioned second form.

First embodiment

The first embodiment of the present invention is shown in Fig. 1～Fig. 3.Fig. 1 is the longitdinal cross-section diagram of stepping motor, and Fig. 2 A, 2B are the front elevations of observing the inside of Fig. 1 motor from rotor shaft direction, and Fig. 3 is the side view of rotor.

The stepping motor of first embodiment is in the stator 1 that the magnetic by four main pole structures constitutes, and disposes HB type rotor 2 and the inner rotator type HB type stepping motor of formation.Shown in Fig. 2 A, as critical piece, stator 1 comprises the stator core 1A that disposes A phase, B phase, A ' phase, four main poles 11 of B ' phase from the core back 10 of ring-type roughly to the inside radially and constitute.The top ends relative with rotor 2 at each main pole 11 forms a plurality of little tooth 11a respectively.In addition, as shown in Figure 1, coil 3 is wound up into each main pole 11.Four coils connect like this, make that each relative main pole coil is anti-phase by excitation, thereby constitute two phase coils.As shown in Figure 1, stator core 1A from axial both sides by support 6,7 clampings that constitute by nonmagnetic materials such as aluminium.

On the other hand, as shown in Figure 1, rotor 2 by with two groups in 21,22 clamp axis of a pair of rotor core to through magnetized magnet 51 and the rotor set that constitutes, in the axial direction in abutting connection with and be fixed in rotating shaft 4 and constitute.Magnet 51 is configured to, and makes the polarity of rotor core 21 of the rotor core 22 of a rotor set of adjacency and another rotor set identical.

In addition, shown in Fig. 2 A, 2B, form a plurality of little tooth 20a on the first-class pitch of the circumference of rotor core 21,22 ground.In Fig. 2 A, rotor core 21 is shown, at rotor core 22 shown in Fig. 2 B.Two rotor cores 21,22 of each rotor set, mutually with the configuration of staggering of 1/2 pitch of little tooth, and the little tooth phase place of the rotor core 21 of the little tooth of the rotor core 22 of a rotor set of adjacency and another rotor set disposes in the same manner at circumferencial direction.

Fixed the rotating shaft 4 of two group rotor groups, mode is supported to rotate freely to be mounted respectively bearing 8,8 in support 6,7 inboards.Therefore, between the little tooth 20a of the little tooth 11a of stator 1 and rotor core 21,22, guaranteed air gap, and rotor 2 can with rotating shaft 4 co-rotation.

Fig. 3 is the side view that illustrates according to the rotor set of first embodiment.The thickness of two magnets 51 is Tm, and rotor core 21 and 22 thickness are respectively Tc/2.The core thickness of central portion is rotor core 21 and 22 thickness that overlap, and is expressed as Tc.In addition, the total length of rotor set can be expressed as 2 (Tc+Tm).

As shown in Figure 3, in the stepping motor of first embodiment, the thickness of the thickness of magnet 51 and rotor core 21,22 is to set like this: the relation of the thickness T m of the magnet 51 of rotor 2 and the thickness T c of rotor core 21 and 22 is Tm/Tc=0.25～0.45, the peakflux density of the little tooth of rotor is 1.4～1.7T, and the peakflux density difference of the axial both ends P of the main pole of stator core and central portion Q (with reference to figure 1) is 0.75～0.85T.

Therefore, can obtain back electromotive force the biglyyest.

In addition, the rotor core 21 of the rotor core of a rotor set of adjacency 22 and another rotor set needn't be always tight adjacency, also can exist space or between to insert the magnetic insulation body between the two.

Radial attraction force when Fig. 4 shows the stepping motor two-phase excitation of first embodiment, F1, F2, F3, F4 represent to affact mutually the attraction radially of the rotor core 21,22,21,22 of configuration successively respectively.The balance because radial attraction force is disperseed is not so exist uneven force of the breath.

As the method for obtaining motor torque significantly,, can not obtain wishing the torque that the magnetic flux of magnet does not also increase though the method for the stacked thickness that increases stator core is arranged.

At this,, the flux flow in two-phase four utmost point stators of first embodiment is described with reference to figure 2A and Fig. 2 B.

In a rotor core 21, at the state shown in Fig. 2 A, A is mutually because the little tooth 20a of rotor is relative with the little tooth 11a projection of stator, so magnetic resistance is little, flows through at most from the magnetic flux of rotor.On the other hand, A ' phase is because the protuberance of the little tooth of rotor is relative with the recess of the little tooth of stator, so the magnetic resistance maximum is less from the magnetic flux that rotor flows into.The protuberance of B phase and little tooth 20a of its rotor of B ' phase and the little tooth 11a of stator is relative in half position that overlaps, and flows into the magnetic flux of A phase and A ' middle size mutually.

In another rotor core 22, under the state shown in Fig. 2 B, A is mutually because the protuberance of the little tooth of rotor is relative with the recess of the little tooth of stator, so the magnetic resistance maximum is less from the magnetic flux that rotor flows into.On the other hand, A ' phase is because the little tooth Ha projection of the little tooth 20a of rotor and stator is relative, so magnetic resistance is little, flows through at most from the magnetic flux of rotor.The protuberance of B phase and little tooth of its rotor of B ' phase and the little tooth of stator is relative in half position that overlaps, and flows into the magnetic flux of A phase and A ' middle size mutually.

When increasing the magnetic flux of magnet at leisure, the magnetic flux of each phase increases.When but the magnetic flux of magnet was too much, in the rotor core shown in Fig. 2 A 21, the magnetic flux of A phase became at most, and the little tooth and the main pole that constitute the A phase are saturated.Its result, the magnetic flux that does not flow into the A phase is as leakage flux, turns back to rotor core 22 from the combination section of the convex-concave portion of the little tooth 20a of the rotor core shown in Fig. 2 B 22 and the little tooth 11a of stator.This leakage flux Φ B is owing to flow in the other direction with respect to the coil interlinkage flux Φ A of standard, the result, and actual interlinkage flux weakens, and the back electromotive force of A phase reduces.That is, setting magnet thickness and rotor core thickness make and do not produce leakage flux Φ B, can obtain making the only relation of back electromotive force maximum thus.

This phenomenon is identical in mixing (HB) the type stepping motor of all same structures, even two-phase ends of the earth motor, three-phase three utmost points, 6-pole motor ground are the same.

Next the torque of test generation.In Fig. 2 A, the effective main flux that enters the A phase coil is  A.The coil back electromotive force e of rotor during the situation considering here to rotate with the electrical angle speed omega _AIt is (1) formula.N is the number of turns of each phase coil, and k is a constant, then  A=Φ cos θ.

$e_A=-n\frac{{\mathrm{d\φ}}_A}{\mathrm{dt}}=\mathrm{n\Φk\ω}\sin \mathrm{\θ}---\left(1\right)$

On the other hand, according to being divided by as the long-pending theory output of back electromotive force and electric current by mechanical angle speed omega M=ω/p, torque becomes (2) formula.At this, p is that number of pole-pairs is the little number of teeth of stator or rotor.

T _A＝e _Ai/ω _M＝inΦkpsinθ (2)

From (2) formula as can be known, if the wire circle and the little number of teeth are constant, in order to increase torque, must increase average magnetic flux Φ and constant k as can be known by coil.

Obtaining the long-pending combination of average magnetic flux Φ and constant k significantly, is to obtain torque significantly, makes the magnet thickness that back electromotive force becomes maximum and the combination of rotor core thickness.

Fig. 5 shows the magnet thickness Tm of Fig. 3 and rotor core thickness T c as parameter, is calculated the result of variation of the back electromotive force of first stepping motor of implementing by FEM (finite element method (FEM)) electromagnetic field analysis.

Four type motor A, B, C, the Ds different to the total length of rotor set analyze.The total length of the rotor set of motor A is 14mm, and that motor B is 18mm, and that motor C is 22mm, motor D be 28mm.To each motor, the back electromotive force when analyzing the thickness T m variation that makes magnet.The transverse axis of Fig. 5 is represented the thickness T m of magnet, and the longitudinal axis is represented the value with the back electromotive force of the A phase under the situation of 500r/min rotary electric machine, has peak value as can be known according to the thickness of magnet in back electromotive force.

Because the total length of rotor set is fixed, so that the thickness of magnet increases, the thickness of rotor core is reduced.In the relation of the position of the rotor of Fig. 2 A, 2B and stator, when the thickness of magnet increased, the magnetic flux of each phase increased, but when reaching the saturated critical point of the little tooth of rotor and stator and main pole, the magnetic flux that does not flow into the A phase flow into A ' phase, B mutually and B ' mutually.For the A phase, flow into the magnetic flux of A ' phase, owing to move on the direction that interlinkage flux is reduced with respect to the motor coil of A phase, the back electromotive force of A phase reduces as a result.

In Fig. 5, be under the situation of 14mm in the rotor set total length of A, Tc is 5.5mm, Tm is 1.5mm, is under the situation of 18mm in the rotor set total length of B, and Tc is 7mm, Tm is 2mm, rotor set total length at C is under the situation of 22mm, and Tc is 8mm, and Tm is 3mm, rotor set total length at D is under the situation of 28mm, Tc is 10mm, and Tm is 4mm, and back electromotive force is peaked combination as can be known.Its result not only carries out electromagnetic field analysis, and can be confirmed through the motor of trial-production by reality.

Fig. 6 is according to the result who obtains among Fig. 5, and transverse axis is represented the ratio Tm/Tc value of the thickness T m and the rotor core thickness T c of magnet, and the longitudinal axis is represented the chart of the value of back electromotive force.In 14mm～28mm scope, the Tm/Tc value of back electromotive force maximum is between 0.25～0.45 as can be known at rotor set thickness.

Fig. 7 is the thickness T m that transverse axis is represented magnet, and the longitudinal axis is represented the figure of magnetic flux density of position of the back electromotive force maximum of the little tooth 20a of rotor.The pass of the back electromotive force of Fig. 5 and magnet thickness Tm tied up on Fig. 7 map, the peakflux density of the little tooth of rotor is distributed in 1.5～2T as can be known.

Fig. 8 is the figure that thickness, the longitudinal axis that transverse axis is represented magnet are represented the magnetic flux density difference of stator main pole portion 11.The pass of the back electromotive force of Fig. 5 and magnet thickness tied up on Fig. 8 map, as can be known the magnetic flux density difference of the axial both ends P of stator main pole and central portion Q and back electromotive force is proportional and the peakflux density difference is distributed in 0.75～0.85T.

Fig. 9 illustrates the figure of vibration characteristics of situation that pulse step drives the stepping motor of first embodiment and existing example, and wherein transverse axis is the motor revolution, and the longitudinal axis is the vibration values radially of motor casing.By from the vibration values of the point outside near the resonance point the 100r/min, can see the effect of motor of the present invention up to the interval of 450r/min.Can see that in the motor of two-phase four utmost points of first embodiment be 3～4G, be the effect that the vibration of 1～3G reduces in the motor of the two-phase ends of the earth.

Figure 10 is the figure that the relation of the rotor core 21 of two-phase ends of the earth motor and stator core 1B is shown, and Figure 11 is the figure that the relation of the rotor core 21 of three-phase three utmost point motors and stator core 1C is shown.Though each main pole number changes, can constitute the magnetic circuit with above-mentioned two-phase four utmost point motor equivalences, and can obtain identical effect.

Second embodiment

The basic structure of the stepping motor of second embodiment is identical with the structure of first embodiment shown in Fig. 1 and Fig. 2 A, the 2B.

In said structure, the stepping motor of second embodiment is set as 0.06～0.08mm with the air gap of the inner peripheral surface of the little tooth 11a on main pole 11 tops of the outer peripheral face of the little tooth 20a of rotor core 21,22 and stator 1.

For the general air gap of existing HB type stepping motor, by air gap is enlarged 20%～60% size, the circularity of requirement is relaxed, do not need the Surface Machining of stator main pole rotor core 21,22 face relative with the stator main pole, can reduce processing cost.

But,,, should be preceding topic with special construction with two above-mentioned group rotor groups in order to reduce torque for only enlarging air gap individually.

Next, introduce magnetic field analysis and evaluates calculation formula and illustrate, also can obtain situation with existing identical above torque even in above-mentioned structure, enlarge air gap.

The stepping motor of the existing type of object has as a comparison, the little tooth internal diameter of stator shown in Figure 12 C is the stator of eight magnetic poles of 26mm and the rotor with single rotor set shown in Figure 12 F, air gap is 0.05mm, and magnet is formed by neodymium and residual magnetic flux density is used 1.05T.With this motor as A type motor.

Therewith relatively, with the stepping motor of second embodiment shown in Figure 12 G with two group rotor groups as B, C type motor.D type motor is the comparative example that does not comprise in a second embodiment.In B, C, D type motor, magnet is formed by ferrite and residual magnetic flux density is 0.4T, and air gap is 0.07mm.The stator that it is the main pole of 26mm that the Type B motor has four little tooth internal diameters of the stator shown in Figure 12 A; The stator that it is 27.5mm that C type motor has the little tooth internal diameter of stator shown in Figure 12 D; The stator that it is 29mm that D type motor has the little tooth internal diameter of stator shown in Figure 12 E.Various types of detailed contents are as shown in table 1 below.

Table 1

Motor type	The quantity of main pole	The quantity of the little tooth of stator	The diameter D (mm) at the tip of the little tooth of stator	Air gap (mm)	The material of magnet
						A
	8	6	26	0.05	Neodymium
						B
	4	11	26	0.07	Ferrite
						C
	4	11	27.5	0.07	Ferrite
						D
	4	11	29	0.07	Ferrite

Because the different characteristic of electric machine structure under coil temperature rises constant condition, is assessed for the torque that back electromotive force analysis result and coil portion effective area according to each circle of coil carry out motor, generate following assessment formula for relatively.The torque tau of each phase ₁By back electromotive force e, current i ₁, formula (3) expression that constitutes of angular velocity omega.

τ ₁ω＝ei ₁ (3)

Astragal is set at n ₁, the back electromotive force of every circle is set at e ₁The time, e is by formula (4) expression, and formula can be changed into formula (5).

e＝e ₁n ₁ (4)

τ ₁ω＝e ₁n ₁i ₁ (5)

At this, the cross-sectional area of all coils portion is set at S _C, occupation efficiency is f _S, when the number of phases is m, the cross-sectional area S of every coil ₁It is (6) formula.

${\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">S</figure-callout>}}_1=\frac{f_{\mathrm{<figure-callout\; id="2"\; label="S\; S\; C"\; filenames="A20061006440100181.png,A20061006440100191.png"\; state="\{\{state\}\}">S</figure-callout>}}{S}_C{}_{}}{{2\mathrm{mn}}_1}---\left(6\right)$

The average length of every coil is set at l ₁, when the resistivity of coil is assumed to be ρ, the coil resistance R of a phase ₁Be formula (7).At this, with m, ρ, l ₁, f _SSet k for _r, as constant.

${\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">R</figure-callout>}}_1=\frac{{\mathrm{\&rho;n}}_1{l}_1}{{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">S</figure-callout>}}_1}={\mathrm{\&rho;n}}_1{\mathrm{<figure-callout\; id="1"\; label="l"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">l</figure-callout>}}_1\&times;\frac{{2\mathrm{mn}}_1}{f_S{S}_C}=\frac{{2\mathrm{m\&rho;l}}_1}{f_S}\&times;\frac{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^2}{S_C}$

$=k_r\&times;\frac{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^2}{S_C}---\left(7\right)$

In addition, copper loss W ₁By formula (8) expression, current i ₁Represent by formula (9).

${\mathrm{<figure-callout\; id="1"\; label="W"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">W</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">i</figure-callout>}}_1^2{R}_1---\left(8\right)$

$i_1=\sqrt{\frac{W_1}{R_1}}---\left(9\right)$

With formula (7) substitution formula (9), if copper loss W ₁For constant

$i_1=\sqrt{\frac{W_1{S}_C}{{\mathrm{<figure-callout\; id="1"\; label="k\; r\; n"\; filenames="A20061006440100181.png,A20061006440100211.png"\; state="\{\{state\}\}">k</figure-callout>}}_r{n}_{}^{}{}_1^2}}=\sqrt{\frac{W_1}{k_r}}\&times;\sqrt{\frac{S_C}{n_1}}---\left(10\right)$

$k_i=\sqrt{\frac{W_1}{k_r}}---\left(11\right)$

Current i wherein ₁Be formula (12).

$i_1=k_i\&times;\frac{\sqrt{S_C}}{n_1}---\left(12\right)$

During with formula (12) substitution formula (5), obtain formula (13).

${\mathrm{\&tau;}}_1\mathrm{\&omega;}=k_i{e}_1\sqrt{S_C}---\left(13\right)$

Therefore, under the constant condition of the caloric value of coil, torque tau ₁Can be according to the back electromotive force e of each coil ₁Cross-sectional area S with all coils portion _CSubduplicate product judge the quality of torque.

The subduplicate result who makes the possible slot part area of near the decomposition result of the back electromotive force each circle of each motor and coil is shown in the table 2.For the A type of the ends of the earth of existing equipment, torque ratio is 1.52 times in Type B of the present invention, and torque ratio is 1.73 times in C type of the present invention, and torque ratio is 1.95 times in D type of the present invention.According to this result,, also can increase substantially torque with respect to the A type even in any one of B, C, D type, air gap is increased 0.07mm.

Table 2

Under the situation of the torque abundance that equates with prior motor, can enlarge the gap of the inner peripheral surface on the little tooth outer peripheral face of rotor and stator main pole top further, the requirement of the circularity of rotor portions outer peripheral face and stator inner peripheral surface more relaxes, and processing becomes easy.

In addition, in order to suppress vibration, the deflection that need to suppress the little tooth from the top of the outstanding utmost point portion that each main pole of stator is extended, for this reason, as Figure 12 A with as shown in Figure 12 B of the enlarged drawing of the part that encloses by its dotted line, the length of circular arc that is formed with the outstanding utmost point 11c of portion of stator 1 each main pole 11 little tooth 11a is L, the width of the coil installation portion 11b of main pole 1 is W, the value of L/W is set at smaller or equal to 2.9, and the angle θ of coil installation portion 11b and the outstanding utmost point 11c of portion is set at 95 degree＜θ＜120 degree.

Figure 13 is that the motor of the Type B rating of electric machine of above-mentioned second embodiment is under the situation of 0.05mm～0.08mm at air gap, by analyzing the result that motor torque, gear torque and motor attraction radially obtain.When enlarging the gap with the benchmark of 0.05mm, torque 55 and attraction 56 are along with the increase in gap reduces with roughly the same slope.As can be known, another gear torque 57 reduces with the slope of about twice.

Existing main pole ends of the earth motor is the A type, and the gap is 0.05mm, and the torque characteristics of motor is 1/1.52 (about 65%) with the ratio of Type B, can be designated as 58 in Figure 13.Even being used to keep the gap of the torque of this existing type expands 0.08mm to and also can satisfy.

In addition, be identical at the air gap of existing A type and Type B as the gear torque 57 of motor oscillating reason during for 0.05mm, can be reduced to about 60% at the Type B air gap during for 0.07mm.Its result, the air gap of the little tooth outer peripheral face of rotor core and the inner peripheral surface on stator main pole top can be 0.06mm～0.08mm, can also realize the improvement of characteristic.

The stepping motor of second embodiment, the core of stator and rotor is stacked automatically in the punch process step, the inner peripheral surface honing step that does not need the outer peripheral face grinding steps and the stator of rotor, make not only marked downly, and the burr that in grinding and honing operation, does not produce, do not need the treatment step that burr disperses that prevents of trouble yet, can also improve reliability.

Analysis in the little tooth on the top of the stator main pole 11 shown in Figure 12 A, interrupt from coil installation portion 11b radially under farthest the situation of attraction of little tooth 11x to motor radially displacement and the result that obtains is shown in Figure 14.Curve 63 is existing A type motors, and curve 62 is Type B motors of second embodiment, and curve 61 is the power along motor little tooth 11x radially that is applied to the D type motor of comparative example, illustrate thus little tooth 11x to motor displacement radially.

From coil installation portion 11b to farthest little tooth 11x apart from Z, by the size of Figure 12 B record, can calculate the poor of little tooth group's circular arc width L and main pole width W, as two parts.In existing A type motor, Z is 2.98mm, is 53mm in the Type B motor, is 5.7mm in C type motor, is 6.25mm in D type motor.Because this value changes according to the size of motor, so when calculating the L/W value of being determined by the ratio of L and W, existing A type is 2.99, Type B is 2.77, and the C type is 2.84, and the D type is 3.08.

In addition, coil installation portion 11b is set at 95～120 degree with the angle θ of the outstanding utmost point Hc of portion that extends from installation portion.The service behaviour variation of coil when θ spends smaller or equal to 95, the occupation efficiency of coil also reduces.The width of the outstanding 11c of utmost point portion attenuated when θ spent more than or equal to 120, and the problem of the occupation efficiency reduction of coil can take place, and therefore preferably angle θ is set at 95 degree＜θ＜120 degree.

The load that is applied to little tooth 11x farthest is the displacement of the situation of 3N, is 0.14 μ m in the A type, is 0.46 μ m in Type B, is 0.78 μ m in the C type, and the displacement quantitative change is big.In the prior motor structure, the vibration during this attraction is rotated motor has direct influence, but in structure of the present invention, as mentioned above, does not have uneven force of the breath basically, and the phenomenon of rotating shaft 4 vibrations can not take place.But, can take place owing to stator self directly vibrates the motor oscillating that causes.

Figure 15 measures and relatively the input pulse number under the situation of micro-stepping drive motors and the figure of vibration characteristics.66 is vibration characteristics of existing A type among the figure, the 67th, and the vibration characteristics of Type B, the 65th, the vibration characteristics of D type.When umber of pulse was smaller or equal to 2500PPS as can be known, the Type B vibration was minimum.In addition, even be identical with Type B in high impulse field A type.But the D type vibrates in whole pulse field and continues to become big as can be known.Reason is because radially the displacement that causes of farthest the relevant radial attraction force of little tooth is big from main pole.

In order to suppress vibration, need set within the specific limits from main pole to farthest little tooth apart from Z.On the other hand, apart from Z too hour, the little number of teeth reduces torque and reduces, and the area coil of groove also reduces, thereby influences motor torque.Consider vibration characteristics in the electric machine structure of present embodiment, the L/W value is set at smaller or equal to 2.9, and is set at 95 degree＜θ＜120 degree according to the angle θ of portion.

As mentioned above, the second embodiment of the present invention has been described, but three-phase stepper motor ground can be implemented similarly with two-phase stepping motor.

The basic fundamental of each key element of the present invention is determined, and can obtain significant improved properties and cost reduction in two-phase or the three-phase stepper motor by applying it to.And, the stepping motor that uses in the OA machine as processing images such as facsimile machine, ink-jet printer, laser printer or photocopiers reduces because can realize the cost under the absolute condition, realizes low vibration, low noise simultaneously, so, can be widely used as only drive source.

Claims (9)

1, a kind of stepping motor, this motor has a plurality of little teeth on the top of the outstanding utmost point portion of extending from main pole, and by having core back that links this main pole periphery integratedly and the stator that is wound in the coil on each main pole, with via air gap and the two group rotor groups that are disposed at vertically on this stator constitute, this rotor set constitutes by spaced two rotor cores vertically with by these two rotor core clampings and magnetized vertically magnet, described each rotor core has a plurality of little teeth at its outer peripheral face, described each the group two rotor cores along the circumferential direction stagger mutually little tooth 1/2 pitch and dispose, and the polarity of the little tooth of the rotor core that adjoins each other of described two groups disposes mutually the samely, it is characterized in that the relation of magnet thickness Tm and rotor core thickness T c is Tm/Tc=0.25～0.45.

2, stepping motor according to claim 1 is characterized in that, described magnet is a ferrimagnet, and the peakflux density of the motor radial component of the little tooth of rotor is 1.4～1.7T.

3, stepping motor according to claim 1 is characterized in that, described magnet is a ferrimagnet, and the axial both ends of stator main pole and the peakflux density difference of central portion are 0.75～0.85T.

According to any one described stepping motor among the claim 1-3, it is characterized in that 4, described main pole number is 4 or 8, described coil is a two-phase.

According to any one described stepping motor among the claim 1-3, it is characterized in that 5, described main pole number is 3 or 6, described coil is a three-phase.

6, a kind of stepping motor, this motor has a plurality of little teeth on the top of the outstanding utmost point portion of extending from main pole, and by having core back that links this main pole periphery integratedly and the stator that is wound in the coil on each main pole, with via air gap and the two group rotor groups that are disposed at vertically on this stator constitute, this rotor set constitutes by spaced two rotor cores vertically with by these two rotor core clampings and magnetized vertically magnet, described each rotor core has a plurality of little teeth at its outer peripheral face, described each the group two rotor cores along the circumferential direction stagger mutually little tooth 1/2 pitch and dispose, and the polarity of the little tooth of the rotor core that adjoins each other of described two groups disposes mutually the samely, it is characterized in that the air gap of the little tooth outer peripheral face of rotor core and the inner peripheral surface on stator main pole top is 0.06～0.08mm.

7, stepping motor according to claim 6, it is characterized in that, the length of the circular arc of the top ends of the outstanding utmost point portion of described each main pole of stator is made as L, the width of the coil installation portion of described main pole is made as W, then the value of L/W is smaller or equal to 2.9, and the angle θ of the root of the described main pole and the described outstanding utmost point is 95 degree＜θ＜120 degree.

According to claim 6 or 7 described stepping motors, it is characterized in that 8, described main pole number is 4, described coil is a two-phase.

According to claim 1 or 7 described stepping motors, it is characterized in that 9, described main pole number is 3, described coil is a three-phase.

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