CN206992894U

CN206992894U - Permanent magnet DC motor and food processor

Info

Publication number: CN206992894U
Application number: CN201720819939.XU
Authority: CN
Inventors: 梁显堂; 刘云祥; 陈连城; 王志锋
Original assignee: Guangdong Midea Consumer Electric Manufacturing Co Ltd
Current assignee: Guangdong Midea Consumer Electric Manufacturing Co Ltd
Priority date: 2017-07-07
Filing date: 2017-07-07
Publication date: 2018-02-09
Anticipated expiration: 2027-07-07

Abstract

The utility model provides a kind of permanent magnet DC motor for food processor, including：Rotor assembly, it includes rotating shaft and commutator, and commutator is set in rotating shaft, and commutator includes at least one commutator segment；And carbon brush, carbon brush are strip, it includes the first carbon brush and the second carbon brush, and the two is symmetrically distributed in the both sides of commutator, and the first end face of a carbon brush is connected with power supply, and the second end face of a carbon brush and at least one commutator segment are inconsistent；Full-size of the second end face along the length direction of rotating shaft is its thickness a, and full-size of the second end face along the direction perpendicular with thickness is its width b, and the thickness a and width b of carbon brush ratio a/b are more than or equal to 1.7.Permanent magnet DC motor provided by the utility model, make the thickness a and width b of carbon brush ratio be more than or equal to 1.7, can allow carbon brush thickness in the case of equal sectional area is bigger, and width is smaller, significantly reduces the generation of invalid winding, improves electric efficiency.

Description

Permanent magnet DC motor and food processor

Technical field

Household appliance technical field is the utility model is related to, more specifically, is related to a kind of permanent magnet DC motor and food preparation Machine.

Background technology

After motor in correlation technique is because of hook commutator bending, the effective length of commutator segment will be shortened, to ensure carbon The sectional area of brush meets the demand that the current density of motor can not be too small, and carbon brush must shorten carbon brush thickness and larger width, so as to The thickness of carbon brush and the ratio of width is made to be less than 1.7；The width of carbon brush is bigger, and the contact chip number of single carbon brush and commutator is got over More, present situation is that carbon brush completely attaches to 2 to 3 commutator segments or more.Carbon brush and commutator contact chip number are more, cause short circuit invalid Winding it is more, the winding of short circuit is now effective winding of motor, that is, the effective edge of these windings should be by Power, and turn into invalid winding after being shorted so that the torque of direct current generator now reduces, and also correspondingly increases armature electricity Stream, then damages motor because increasing the electric current in other windings.

Existing solution method to widen the width of each commutator segment, but can make commutator for commutator brush track diameter is increased External diameter becomes big, so as to add risk when motor runs at high speed, reduces the reliability of motor.

Utility model content

The utility model is intended at least solve one of technical problem present in prior art or correlation technique.

Therefore, a purpose of the present utility model is, a kind of permanent magnet DC motor is proposed.

Another purpose of the present utility model is, proposes a kind of food processor.

In view of this, according to a purpose of the present utility model, there is provided a kind of permanent magnet DC motor, for food preparation Machine, including：Rotor assembly, it includes rotating shaft and commutator, and commutator is set in rotating shaft, and commutator includes at least one commutation Piece；And carbon brush, carbon brush are strip, it includes the first carbon brush and the second carbon brush, and the two is symmetrically distributed in the both sides of commutator, one The first end face of carbon brush is connected with power supply, and the second end face of a carbon brush and at least one commutator segment are inconsistent；Second end face edge The full-size of the length direction of rotating shaft is its thickness a, and second end face is it along the full-size in the direction perpendicular with thickness Width b, the thickness a and width b of carbon brush ratio a/b are more than or equal to 1.7.

Permanent magnet DC motor provided by the utility model, the first carbon brush and the second carbon brush are symmetrically distributed in the two of commutator Side, motor is set to complete commutation action.By improving carbon brush thickness, the thickness a and width b of carbon brush ratio is made to be more than or equal to 1.7, can allowing carbon brush, the thickness of carbon brush is bigger, and width is smaller in the case of equal sectional area, enters for different commutators After the corresponding adjustment of row, a carbon brush is at most simultaneously inconsistent with four commutator segments, now, two only among this four commutator segments It is invalid that commutator segment is short-circuited, and the contact chip number of carbon brush and commutator is effectively reduced, and obtains the winding in rotor assembly Make full use of, significantly reduce the generation of invalid winding, reduce electric current and lost caused by invalid winding, improve motor Reliability of service life, improve electric efficiency.

In addition, the permanent magnet DC motor in above-mentioned technical proposal provided by the utility model, can also have as follows Additional technical feature：

In the above-mentioned technical solutions, it is preferable that the thickness a and width b of carbon brush ratio a/b span be 1.7≤ a/b≤2.5。

In the technical scheme, given the upper limit of the thickness a and width b of carbon brush ratio.Due to carbon brush thickness a by Height dimension to commutator limits, and further to increase the thickness a of carbon brush just needs to increase the height of commutator, works as commutator When too high, the overall longitudinal size of motor can be increased, cause space waste, improve production cost., can by giving the higher limit In the range of the size of commutator is maintained at into a relatively optimization, it can both meet the needs for reducing carbon brush width, and fully The space of motor is make use of, contributes to control cost.

In any of the above-described technical scheme, it is preferable that commutator is groove type reverser.

In the technical scheme, commutator employs groove type reverser, on the one hand, groove type reverser is opens up line embedding groove institute The longitudinal size of occupancy is smaller, and the space of carbon brush can be set just accordingly to increase, and helps to increase the thickness of carbon brush, can more meet A/b is more than or equal to 1.7 requirement.On the other hand, exposed outside different from the winding of hook commutator, groove type reverser will be around In the line embedding groove of group embedment commutator segment, winding corresponding to adjacent two commutator segment can be isolated from each other, and the appropriate line footpath that increases will not also go out The situation of existing adjacent winding contact short circuit, so as to increase the power of permanent magnet DC motor so that permanent magnet DC motor is working When can meet simultaneously output high pulling torque and high-revolving performance requirement, and without too increase commutator diameter, meet Security under high rotating speed needs.

In any of the above-described technical scheme, it is preferable that commutator also includes at least one insulation division, and an insulation division is located at Between two commutator segments；The width c of insulation division, the width d of commutator segment and carbon brush width b meet d≤b≤2d+c.

In the technical scheme, at least one insulation division of commutator can effectively prevent from changing between two commutator segments To being connected to each other between piece during hypotelorism, conducting produces short circuit, both ensure that the normal work of permanent magnet DC motor, and had avoided again Cause fire, improve the security that permanent magnet DC motor uses.The width c of insulation division, the width d of commutator segment and carbon brush Width b meets d≤b≤2d+c, and the higher limit ensure that a carbon brush at most completely attaches to two commutator segments simultaneously, contribute to Reduce the quantity of invalid winding；It is only relative with the time that a commutator segment is in contact long that the lower limit avoids carbon brush, so as to Improve commutating speed, it is ensured that electric efficiency.

In any of the above-described technical scheme, it is preferable that the width c of insulation division is more than or equal to 0.5mm.

In the technical scheme, the width for limiting insulation division is more than or equal to 0.5mm, it is ensured that between adjacent commutator segment There is the electrical distance more than or equal to 0.5mm, can effectively prevent contact short circuit between adjacent commutator segment, improve the reliable of motor Property.

In any of the above-described technical scheme, it is preferable that the span of the diameter of commutator is 28mm to 45mm, commutator segment Quantity be 48.

In the technical scheme, after carbon brush narrows, it can correspondingly increase commutation in the case where not increasing invalid winding The piece number of device；In addition employing the distance between groove type reverser, adjacent two commutator segment can be reduced, in the diameter of commutator Meet the piece number that commutator is can further improve in the case of security needs, safety of the commutator in a diameter of 28mm to 45mm 48 commutator segments can be achieved under size so that the pressure drop between commutator segment reduces, and then makes between conductive component and commutator Electric discharge pressure difference reduce, discharge current reduces therewith, so as to electric spark caused by reducing permanent magnet DC motor operation, that is, keeps away Exempt from permanent magnet DC motor and commutation deterioration occurred, and then improve the security that permanent magnet DC motor uses.

In any of the above-described technical scheme, it is preferable that the width b of carbon brush span is 2.5mm to 6mm.

In the technical scheme, the width b of carbon brush span is defined.The higher limit ensure that a carbon brush is most Completely attached to simultaneously with two commutator segments, help to reduce the quantity of invalid winding；The lower limit avoid carbon brush only with one The time that commutator segment is in contact is relatively long, so as to improve commutating speed, it is ensured that electric efficiency.

In any of the above-described technical scheme, it is preferable that the ratio of the resistivity of the first carbon brush and the resistivity of the second carbon brush Less than or equal to 0.9, wherein, the commutation spark of the second carbon brush is better than the commutation spark of the first carbon brush.

In the technical scheme, one in the first carbon brush and the second carbon brush is connected with motor positive pole, another and motor Negative pole is connected, because the positive and negative electrode pressure drop of permanent magnet DC motor differs greatly, therefore the commutation spark of both positive and negative polarity and wear rate There is very big difference.When the commutation spark of the second carbon brush is stronger, by reducing the resistivity ratio of the first carbon brush and the second carbon brush, Improve the resistivity of the second carbon brush and/or reduce the resistivity of the first carbon brush, help to reduce the current of commutation of the second carbon brush, So as to reduce the discharge spark to commutate every time, reduce the electric abrasion of commutator and the second carbon brush, make the mill of the second carbon brush Loss rate is suitable with the first carbon brush, effectively extends the service life of motor.

To sum up, the utility model provides a kind of AC permanent magnet machine, coordinates the structure of groove type reverser, carbon brush can be allowed to exist In the case of equal section of product, the thickness of carbon brush is bigger, and width is smaller, makes commutator segment number increase corresponding to carbon brush, and then reduce Electric spark caused by permanent magnet DC motor operation.

According to another purpose of the present utility model, there is provided a kind of food processor, including：Any technical side as described above Permanent magnet DC motor described in case.

Food processor provided by the utility model, including the permanent magnet DC motor described in any of the above-described technical scheme, because This has whole beneficial effects of the permanent magnet DC motor, will not be repeated here.

In any of the above-described technical scheme, it is preferable that food processor is at least one of：Wall-breaking machine, mixer, material Reason machine, soy bean milk making machine and juice extractor.

In the technical scheme, food processor is at least one of：Wall-breaking machine, mixer, cooking machine, soy bean milk making machine and Juice extractor, wherein, the cell membrane of food could be smashed, make food, it is necessary to motor has larger power by especially wall-breaking machine Become extremely fine and smooth, therefore the cross-sectional area of carbon brush is often larger, and the power of motor will produce larger fire once increasing Flower, causes potential safety hazard.Permanent magnet DC motor provided by the utility model is applied in wall-breaking machine, by the thickness for improving carbon brush A and width b ratio simultaneously increases the piece number of commutator, both the winding in rotor assembly can be made to be fully used, and effectively dropped The low generation of invalid winding, reduces electric current and is lost caused by invalid winding, ensure that permanent magnet DC motor larger Power under, larger spark will not be produced, improve the security used.

Additional aspect and advantage of the present utility model will become obvious in following description section, or new by this practicality The practice of type is recognized.

Brief description of the drawings

Of the present utility model above-mentioned and/or additional aspect and advantage will in the description from combination accompanying drawings below to embodiment Become obvious and be readily appreciated that, wherein：

Fig. 1 shows the rotor assembly of one embodiment offer of the present utility model and the assembling front view of carbon brush；

Fig. 2 shows the rotor assembly of one embodiment offer of the present utility model and the assembling plan view of carbon brush；

Fig. 3 shows the commutator top view that one embodiment of the present utility model provides；

Fig. 4 shows the rotor assembly winding diagram that one embodiment of the present utility model provides；

Fig. 5 shows the rotor assembly coiling schematic diagram that one embodiment of the present utility model provides.

Wherein, corresponding relations of the Fig. 1 into Fig. 5 between reference and component names is：

10 rotor assemblies, 12 rotating shafts, 14 commutators, 142 commutator segments, 144 insulation divisions, 16 windings, 20 carbon brush, 22 first carbon Brush, 24 second carbon brush, 30 springs.

Embodiment

In order to be more clearly understood that above-mentioned purpose of the present utility model, feature and advantage, below in conjunction with the accompanying drawings and tool The utility model is further described in detail body embodiment.It should be noted that in the case where not conflicting, this Shen The feature in embodiment and embodiment please can be mutually combined.

Many details are elaborated in the following description in order to fully understand the utility model, still, this practicality New to be different from other modes described here using other to implement, therefore, the scope of protection of the utility model is simultaneously Do not limited by following public specific embodiment.

Referring to Fig. 1 to Fig. 5 descriptions according to the utility model some embodiments permanent magnet DC motor.

As depicted in figs. 1 and 2, the embodiment of the utility model first aspect proposes a kind of permanent magnet DC motor, is used for Food processor, including：Rotor assembly 10, it includes rotating shaft 12 and commutator 14, and commutator 14 is set in rotating shaft 12, commutation Device 14 includes at least one commutator segment 142；And carbon brush 20, carbon brush 20 are strip, it includes the first carbon brush 22 and the second carbon brush 24, The two is symmetrically distributed in the both sides of commutator 14, and the first end face of a carbon brush 20 is connected with power supply, and the second of a carbon brush 20 End face and at least one commutator segment 142 are inconsistent；The full-size of length direction of the second end face along rotating shaft 12 is its thickness a, Second end face is its width b, the thickness a and width b of carbon brush 20 ratio a/b along the full-size in the direction perpendicular with thickness More than or equal to 1.7.

Permanent magnet DC motor provided by the utility model, the first carbon brush 22 and the second carbon brush 24 are symmetrically distributed in commutator 14 Both sides, make motor complete commutation action.By improving the thickness of carbon brush 20, the thickness a and width b of carbon brush 20 ratio is made to be more than Or equal to 1.7, can allowing carbon brush 20, the thickness of carbon brush 20 is bigger, and width is smaller in the case of equal sectional area, for difference Commutator 14 adjust accordingly after, carbon brush 20 is at most simultaneously inconsistent with four commutator segments 142, now, only this four It is invalid that two commutator segments 142 among individual commutator segment 142 are short-circuited, and the contact chip number of carbon brush 20 and commutator 14 obtains effectively Reduce, the winding 16 in rotor assembly 10 is fully used, significantly reduce the generation of invalid winding, reduce electric current Lost caused by invalid winding, improve the reliability of service life of motor, improve electric efficiency.Preferably, carbon brush 20 is side Shape strip, i.e. its first end face and second end face are square.

In one embodiment of the present utility model, it is preferable that the thickness a and width b of carbon brush 20 ratio a/b value Scope is 1.7≤a/b≤2.5.

In this embodiment, given carbon brush 20 thickness a and width b ratio the upper limit.Due to the thickness a of carbon brush 20 Limited by the height dimension of commutator 14, further to increase the thickness a of carbon brush 20 just needs to increase the height of commutator 14, When commutator 14 is too high, the overall longitudinal size of motor can be increased, cause space waste, improve production cost.By given The higher limit, the size of commutator 14 can be maintained in the range of a relatively optimization, can both meet that reduction carbon brush 20 is wide The needs of degree, the space of motor is taken full advantage of again, contributes to control cost.

In one embodiment of the present utility model, it is preferable that commutator 14 is groove type reverser.

In this embodiment, commutator 14 employs groove type reverser, on the one hand, groove type reverser is opens up line embedding groove institute The longitudinal size of occupancy is smaller, and the space of carbon brush 20 can be set just accordingly to increase, and helps to increase the thickness of carbon brush 20, more can Meet the requirement that a/b is more than or equal to 1.7.For example, for same high 10mm groove type reverser and hook commutator, the former Line embedding groove only needs to take 2mm in the height direction, and the hook of the latter need to take 3mm to 4mm, often be filled without enough spaces Divide the thickness for improving carbon brush 20.On the other hand, exposed outside different from the winding 16 of hook commutator, groove type reverser is by winding In the line embedding groove of 16 embedment commutator segments 142, winding 16 corresponding to adjacent two commutator segment 142 can be isolated from each other, and suitably increase line footpath Also be not in the situation of the adjacent contact short circuit of winding 16, so as to increase the power of permanent magnet DC motor so that DC Motor can meet the high pulling torque of output and high-revolving performance requirement simultaneously at work, and without too increasing commutator 14 Diameter, meet the security needs under high rotating speed.

As shown in Figures 2 and 3, in one embodiment of the present utility model, it is preferable that commutator 14 also includes at least one Individual insulation division 144, an insulation division 144 is between two commutator segments 142；Width c, the width of commutator segment 142 of insulation division 144 The width b of degree d and carbon brush 20 meets d≤b≤2d+c.

In this embodiment, at least one insulation division 144 of commutator 14, can be effective between two commutator segments 142 The conducting that prevents from being connected to each other during hypotelorism between commutator segment 142 produces short circuit, both ensure that the normal work of permanent magnet DC motor Make, turn avoid and cause fire, improve the security that permanent magnet DC motor uses.Width c, the commutator segment 142 of insulation division 144 Width d and the width b of carbon brush 20 meet d≤b≤2d+c, the higher limit ensure that a carbon brush 20 at most while be changed with two Completely attached to piece 142, help to reduce the quantity of invalid winding；The lower limit avoid carbon brush 20 only with a commutator segment 142 times being in contact are relatively long, so as to improve commutating speed, it is ensured that electric efficiency.

In one embodiment of the present utility model, it is preferable that the width c of insulation division 144 is more than or equal to 0.5mm.

In this embodiment, the width for limiting insulation division 144 is more than or equal to 0.5mm, it is ensured that adjacent commutator segment 142 Between have electrical distance more than or equal to 0.5mm, can effectively prevent adjacent 142 contact short circuits of commutator segment, improve motor Reliability.

In one embodiment of the present utility model, it is preferable that the span of the diameter of commutator 14 be 28mm extremely 45mm, the quantity of commutator segment 142 is 48.

In this embodiment, after carbon brush 20 narrows, commutation can correspondingly be increased in the case where not increasing invalid winding The piece number of device 14；In addition employing the distance between groove type reverser, adjacent two commutator segment 142 can be reduced, in commutator 14 diameter meets the piece number that commutator 14 is can further improve in the case of security needs, and commutator 14 is in a diameter of 28mm 48 commutator segments 142 can be achieved under to 45mm installation dimensions so that the pressure drop between commutator segment 142 reduces, and then makes to lead Electric discharge pressure difference between electric part and commutator 14 reduces, and discharge current reduces therewith, so as to reduce permanent magnet DC motor fortune Electric spark caused by row, that is, avoid permanent magnet DC motor and commutation deterioration occur, and then improve permanent magnet DC motor use Security.Preferably, a diameter of 36mm of commutator 14.Specifically, as shown in figure 1, passing through the pressure of spring 30 effect the One carbon brush 22 and the second carbon brush 24 effectively contact with commutator 14, as shown in figure 3, by 48 commutator segments 142 respectively marked as 142.1st, 142.2 ..., 142.47,142.48, as shown in figure 4, by the winding 16 being connected with commutator segment 142 respectively marked as 16.1、16.2、……16.47、16.48.As shown in figure 5, arrow meaning is the sense of current, it is assumed that electric current flows from the first carbon brush 22 Enter onto the adjacent commutator segment 142.1 and 142.2 of two panels in contact, then respectively from two to be connected with this two panels commutator segment 142 Group winding 16.1 and 16.2 flows through, by the winding 16.3 of corresponding series connection, 16.4,16.5,16.6,16.7,16.8 ..., 16.41st, 16.42,16.43,16.44,16.45,16.46, then two groups of adjacent Hes of commutator segment 142.47 of opposite side are flowed to afterwards After on 142.48, then flow out to the second carbon brush 24.Winding 16.3 that electric current flows through, 16.4 ... 16.45,16.46 in magnetic field Torque is generated under effect, so as to allow rotor assembly 10 to rotate, and winding 16.1,16.2,16.47 and 16.48 is because by the first carbon Brush 22 and the short circuit of the second carbon brush 24 and form invalid winding.When the first carbon brush 22 and the winding more than 16 of the short circuit of the second carbon brush 24, The invalid winding then formed is more, and motor is efficient can be lower.

In one embodiment of the present utility model, it is preferable that the width b of carbon brush 20 span be 2.5mm extremely 6mm。

In this embodiment, the width b of carbon brush 20 span is defined.The higher limit ensure that a carbon brush 20 most It is more to be completely attached to simultaneously with two commutator segments 142, help to reduce the quantity of invalid winding；The lower limit avoids carbon brush 20 only It is relative with the time that a commutator segment 142 is in contact long, so as to improve commutating speed, it is ensured that electric efficiency.

In one embodiment of the present utility model, it is preferable that the resistivity of the first carbon brush 22 and the electricity of the second carbon brush 24 The ratio of resistance rate is less than or equal to 0.9, wherein, the commutation spark of the second carbon brush 24 is better than the commutation spark of the first carbon brush 22.

In this embodiment, one in the first carbon brush 22 and the second carbon brush 24 is connected with motor positive pole, another and electricity Machine negative pole is connected, because the positive and negative electrode pressure drop of permanent magnet DC motor differs greatly, therefore the commutation spark of both positive and negative polarity and wear rate Also there is very big difference.When the commutation spark of the second carbon brush 24 is stronger, by the electricity for reducing the first carbon brush 22 and the second carbon brush 24 Resistance rate ratio, that is, improve the resistivity of the second carbon brush 24 and/or reduce the resistivity of the first carbon brush 22, help to reduce the second carbon The current of commutation of brush 24, so as to reduce the discharge spark to commutate every time, reduce the electric of commutator 14 and the second carbon brush 24 Abrasion, make the wear rate of the second carbon brush 24 and the first carbon brush 22 suitable, effectively extend the service life of motor.

To sum up, the utility model provides a kind of AC permanent magnet machine, coordinates the structure of groove type reverser, can allow carbon brush 20 In the case of equal section of product, the thickness of carbon brush 20 is bigger, and width is smaller, makes 14 numbers increases of commutator corresponding to carbon brush 20, And then reduce electric spark caused by permanent magnet DC motor operation.

The embodiment of the utility model second aspect proposes a kind of food processor, including：Such as above-mentioned any embodiment Described permanent magnet DC motor.

Food processor provided by the utility model, including the permanent magnet DC motor described in any of the above-described embodiment, therefore Whole beneficial effects with the permanent magnet DC motor, will not be repeated here.

In one embodiment of the present utility model, it is preferable that food processor is at least one of：Wall-breaking machine, stir Mix machine, cooking machine, soy bean milk making machine and juice extractor.

In this embodiment, food processor is at least one of：Wall-breaking machine, mixer, cooking machine, soy bean milk making machine and squeezing Juice machine, wherein, the cell membrane of food could be smashed, become food, it is necessary to motor has larger power by especially wall-breaking machine Extremely exquisiteness, therefore the cross-sectional area of carbon brush 20 is often larger is obtained, and the power of motor will produce larger fire once increasing Flower, causes potential safety hazard.Permanent magnet DC motor provided by the utility model is applied in wall-breaking machine, by the thickness for improving carbon brush 20 Degree a and width b ratio simultaneously increases the piece number of commutator 14, the winding 16 in rotor assembly 10 is fully used, The generation of invalid winding is significantly reduced, reduces electric current and is lost caused by invalid winding, ensure that permanent direct-current electric Machine will not produce larger spark under larger power, improve the security used.

In the utility model, term " multiple " then refers to two or more, is limited unless otherwise clear and definite.Term The term such as " installation ", " connected ", " connection ", " fixation " all should be interpreted broadly, for example, " connection " can be fixedly connected, Can be detachably connected, or be integrally connected；" connected " can be joined directly together, and can also pass through the indirect phase of intermediary Even.For the ordinary skill in the art, it can understand above-mentioned term in the utility model as the case may be Concrete meaning.

In the description of this specification, the description of term " one embodiment ", " some embodiments ", " specific embodiment " etc. Mean that combining specific features, structure, material or feature that the embodiment or example describe is contained in of the present utility model at least one In individual embodiment or example.In this manual, identical embodiment is not necessarily referring to the schematic representation of above-mentioned term Or example.Moreover, specific features, structure, material or the feature of description can be in any one or more embodiments or example In combine in an appropriate manner.

Preferred embodiment of the present utility model is the foregoing is only, is not limited to the utility model, for this For the technical staff in field, the utility model can have various modifications and variations.It is all in the spirit and principles of the utility model Within, any modification, equivalent substitution and improvements made etc., it should be included within the scope of protection of the utility model.

Claims

A kind of 1. permanent magnet DC motor, for food processor, it is characterised in that including：

Rotor assembly, it includes rotating shaft and commutator, and the commutator is set in the rotating shaft, and the commutator is included at least One commutator segment；And

Carbon brush, the carbon brush are strip, and it includes the first carbon brush and the second carbon brush, and the two is symmetrically distributed in the two of the commutator Side, the first end face of a carbon brush are connected with power supply, the second end face of a carbon brush and at least one commutation Piece is inconsistent；

The full-size of length direction of the second end face along the rotating shaft is its thickness a, the second end face along with it is described The full-size in the perpendicular direction of thickness is its width b, and the thickness a and width b of the carbon brush ratio a/b are more than or equal to 1.7。
2. permanent magnet DC motor according to claim 1, it is characterised in that

The thickness a and width b of the carbon brush ratio a/b span are 1.7≤a/b≤2.5.
3. permanent magnet DC motor according to claim 1, it is characterised in that

The commutator is groove type reverser.
4. permanent magnet DC motor according to claim 3, it is characterised in that

The commutator also includes at least one insulation division, and an insulation division is between two commutator segments；

The width c of the insulation division, the width d of the commutator segment and the carbon brush width b meet d≤b≤.
5. permanent magnet DC motor according to claim 4, it is characterised in that

The width c of the insulation division is more than or equal to 0.5mm.
6. the permanent magnet DC motor according to any one of claim 3 to 5, it is characterised in that

The span of the diameter of the commutator is 28mm to 45mm, and the quantity of the commutator segment is 48.
7. permanent magnet DC motor according to claim 6, it is characterised in that

The width b of carbon brush span is 2.5mm to 6mm.
8. permanent magnet DC motor according to any one of claim 1 to 5, it is characterised in that

The ratio of the resistivity of the resistivity of first carbon brush and second carbon brush is less than or equal to 0.9, wherein, described the The commutation spark of two carbon brush is better than the commutation spark of first carbon brush.
A kind of 9. food processor, it is characterised in that including：

Permanent magnet DC motor as any one of claim 1 to 8.
10. food processor according to claim 9, it is characterised in that the food processor is at least one of： Wall-breaking machine, mixer, cooking machine, soy bean milk making machine and juice extractor.