TWI843297B - Motor - Google Patents

Abstract

A motor includes a housing, a bearing, a fixed ring, a stator assembly, and a rotor assembly. The housing has a first wall portion defining a first annular groove, a second wall portion defining a second annular groove, a third wall portion defining a third annular groove, and an inner flange protruding from the first wall portion. The first annular groove, the second annular groove, and the third annular groove are coaxially arranged and arranged axially, and the second wall portion is provided with an inner thread. The bearing is accommodated in the first annular groove and is bonded and fixed to the first wall portion with an adhesive layer. The fixed ring is accommodated in the second annular groove and is provided with an outer thread matching the inner thread so as to be locked and fixed to the second wall portion. The fixed ring and the inner flange jointly limit the bearing in the axial direction. The stator assembly is accommodated in the third annular groove. The rotor assembly is supported by the bearing and can be driven by the stator assembly to rotate around an axis.

Description

Motor

The present invention relates to an electric motor, in particular an electric motor suitable for a vehicle.

When assembling a bearing, the internal clearance of the bearing must be considered. Usually, when the inner ring and the outer ring are assembled with the other two components, one must be slid in and the other must be pressed in with a tight fit (interference). Alternatively, both the inner ring and the outer ring must be slid in with the other components (no interference). In order to prevent the inner ring or the outer ring from moving with the opposing components in sliding contact, a C-clip or other mechanism is usually used to prevent its axial movement.

NVH stands for Noise, Vibration, Harshness, which stands for noise, vibration, and roughness respectively. It is an indicator used to evaluate the comfort of riding in a vehicle. Therefore, the electric motor (motor) used in the vehicle must reduce the adverse effects of NVH.

The bearings used in existing automotive motors need to withstand large axial forces. When the axial force or temperature change is large enough to cause strain in the motor's housing components of different materials, a gap will be created between the outer ring of the bearing and the housing, causing the outer ring of the bearing to slide relative to the housing. This will cause vibration or relative friction and sliding between the bearing and the housing, resulting in poor NVH or wear of the contact surface.

Therefore, one of the purposes of the present invention is to provide a motor that can solve the above-mentioned problems.

Therefore, in some embodiments of the present invention, the motor includes an outer shell, a bearing, a fixed ring, a stator assembly and a rotor assembly. The outer shell has a first wall portion defining a first annular groove, a second wall portion defining a second annular groove, a third wall portion defining a third annular groove, and an inner flange protruding radially from the end edge of the first wall portion toward the center. The first annular groove, the second annular groove and the third annular groove are coaxially arranged and arranged axially, and the second wall portion is provided with an internal thread. The bearing is accommodated in the first annular groove and is bonded and fixed to the first wall portion with an adhesive layer. The fixed ring is accommodated in the second annular groove and is provided with an external thread matching the internal thread to be locked and fixed to the second wall portion. The stator assembly is accommodated in the third annular groove. The rotor assembly is supported by the bearing and can be driven by the stator assembly to rotate around the axis.

In some embodiments, the bearing is accommodated in the first annular groove in a sliding manner.

In some embodiments, the fixing ring and the inner flange together limit the bearing in the axial direction.

In some embodiments, a plurality of riveting grooves are formed at the connection between the fixing ring and the outer shell.

In some embodiments, the adhesive layer is formed of a colloid having an elongation of at least 50% and a shear strength of at least 3.0 MPa.

In some embodiments, most of the colloid in the adhesive layer is gathered at the chamfer of the outer ring of the bearing.

The present invention has at least the following effects: the outer ring of the bearing is bonded and fixed to the first wall portion by the adhesive layer, which can reduce the gap between the bearing and the first wall portion and provide elastic buffering, which can not only increase the effect of preventing the bearing from moving in the axial direction, but also increase the effect of preventing the outer ring of the bearing from rotating, thereby avoiding the vibration between the bearing and the housing that causes poor NVH or surface wear caused by relative movement.

100: Motor

1: Shell

11: First wall part

111: First ring groove

12: Second wall section

121: Second ring groove

122: Internal thread

13: Third wall section

131: Third ring groove

14: Inner convex edge

2: Bearings

21: Inner Ring

22: Outer Ring

221: Chamfer

3: Fixed ring

31: External thread

32: Riveting groove

4: Stator assembly

5: Rotor assembly

6: Adhesive layer

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG. 1 is a three-dimensional view of an embodiment of the motor of the present invention; FIG. 2 is a three-dimensional exploded view of the embodiment; FIG. 3 is a three-dimensional cross-sectional view of the housing of the embodiment; FIG. 4 is a cross-sectional schematic view of the embodiment; FIG. 5 is a top view of the embodiment, in which a rotor assembly is removed; FIG. 6 is a schematic diagram indicating the bearing size of the embodiment; and FIG. 7 is a schematic diagram illustrating the gap between the chamfer of the bearing and the housing of the embodiment.

Referring to FIG. 1 and FIG. 2 , an embodiment of the motor 100 of the present invention includes a housing 1, a bearing 2, a fixed ring 3, a stator assembly 4 and a rotor assembly 5.

Referring to FIG. 3 , the housing 1 has a first wall portion 11 defining a first annular groove 111, a second wall portion 12 defining a second annular groove 121, a third wall portion 13 defining a third annular groove 131, and an inner convex edge 14 radially extending from the end edge of the first wall portion 11 toward the center. The inner convex edge 14 and the first wall portion 11 jointly define the first annular groove 111. The first annular groove 111, the second annular groove 121 and the third annular groove 131 are coaxially arranged and arranged axially, and the second wall portion 12 is provided with an inner thread 122.

Referring to Fig. 3, Fig. 4 and Fig. 6, the bearing 2 is accommodated in the first annular groove 111 in a sliding assembly manner and is bonded and fixed to the first wall portion 11 by an adhesive layer 6. In this embodiment, the bearing 2 is a four-point contact ball bearing 2 and has an inner ring 21 and an outer ring 22. The adhesive layer 6 is disposed between the surface of the outer ring 22 of the bearing 2 and the first wall portion 11, and most of the adhesive of the adhesive layer 6 is gathered at the chamfer 221 of the outer ring 22 of the bearing 2. The adhesive layer 6 of this embodiment is formed by a Threebond brand, model TB1533 adhesive. The outer ring 22 of the bearing 2 is bonded and fixed to the first wall 11 by the adhesive layer 6. After curing, the adhesive can fill the gap between the bearing 2 and the first wall 11 and provide elastic buffering, which can not only increase the effect of preventing the bearing 2 from moving in the axial direction, but also increase the effect of preventing the outer ring of the bearing 2 from rotating, thereby avoiding the vibration between the bearing 2 and the housing 1, resulting in poor NVH or surface wear caused by relative movement.

Referring to FIGS. 3 to 5 , the fixing ring 3 is accommodated in the second annular groove 121 and is provided with an outer thread 31 that matches the inner thread 122 to be locked and fixed with the second wall portion 12. The fixing ring 3 and the inner flange 14 together limit the bearing 2 in the axial direction. In this embodiment, a plurality of riveting grooves 32 are pressed out at the connection between the fixing ring 3 and the housing 1 with a special rivet. Specifically, the fixing ring 3 is locked to the housing 1 with a specific torque, which enables the fixing ring 3 to effectively press the bearing 2 in the axial direction. Four riveting grooves 32 are distributed on the fixing ring 3 at intervals of 90 degrees. The extrusion force of the riveting grooves 32 is used to increase the resistance of the fixing ring 3 to withdraw, that is, to increase the loosening torque of the fixing ring 3, so that the fixing effect of the fixing ring 3 is more stable.

Referring to Figures 2 and 4, the stator assembly 4 is accommodated in the third annular groove 131. The rotor assembly 5 is supported by the bearing 2 and can be driven by the stator assembly 4 to rotate around the axis. The stator assembly 4 and the rotor assembly 5 can be implemented using existing technology.

The following describes the design parameters for selecting the adhesive for adhesive layer 6.

Referring to Figures 4 and 6, it is known that when the bearing 2 rotates, there is friction between the inner ring 21 and the outer ring 22, and the friction may cause the outer ring 22 of the bearing 2 to be driven to rotate. In this embodiment, the outer ring of the bearing 2 is bonded and fixed to the outer shell 1 (i.e., the bearing seat) with adhesive, and the effective performance contribution area (contact area) of the adhesive is mainly concentrated at the chamfer 221 of the outer ring 22 of the bearing 2. Therefore, the appropriate adhesive can be selected based on the relationship between the size of the chamfer 221 of the outer ring 22 of the bearing 2 and the (transverse) shear strength of the adhesive.

Figure 6 is a schematic diagram of the bearing 2, and indicates the axial length W and radial length X of the chamfer 221 of the bearing outer ring 22, the outer diameter of the bearing outer ring 22 is Y (the outer radius is y), the inner diameter of the bearing outer ring 22 is Z, and the axial thickness of the bearing 2 is L. The dimensions of W, X, Y, Z, and L are in mm.

The circumference of the bearing outer ring 22 is π*Y.

The arc length F of the chamfer 221 of the bearing outer ring 22 (F is always greater than the slope of the right triangle made by X and W). According to the Pisces theorem, the length of the hypotenuse Q can be obtained, and the length of the hypotenuse Q is always greater than the radial length X (vertical side) or the axial length W (base). That is, F>Q>W or X.

The contact area between the chamfer 221 of the bearing outer ring 22 and the colloid is represented by A, and the contact area A is approximately Q*circumference=πQY. Here, the most conservative calculation is A=πWY.

The area of the first wall portion 11 of the housing 1 near the chamfer 221 of the outer ring 22 is represented by H, wherein the radial contact area is X*circumference=πXY, and the axial contact area is approximately equal to πWY , so the total contact area H=π(X+W)*Y.

The shear strength of the colloid is represented by B, and its actual value can be known from the performance data provided by the colloid supplier.

The rotational friction torque of the bearing is represented by C. Generally, the bearing is a standard product and the performance value can be known from the supplier.

Since the shear strength of the colloid is B Mpa=BN/mm ² , the shear force acting on the bearing area is: contact area A mm ² * BN/mm ² =AB N. When the bearing rotates, the anti-torque capacity generated by the colloid is: torque (Nm) = arm (m) * force (N) = (0.001y) * AB = 0.0005ABY (Nm). This anti-torque capacity must be greater than the bearing rotation friction torque. Therefore, the selected colloid performance must meet 0.0005ABY Nm>C Nm.

To explain this in detail in this embodiment, W=0.4mm, X=0.4mm, Y=40mm. A=3.14*0.4*40=50.24mm ² . B=5.8Mpa=5.8N/mm ² . C=0.5Nm (friction torque of bearing at 1000rpm, -40°C). AB=50.24*5.8=291.392 N; 0.0005ABY=0.0005 * 291.392 * 40=5.82784Nm (theoretical maximum value). Therefore, 0.0005ABY(5.82784)Nm>C(0.5)Nm. When the motor is operating at high temperature, the colloid shear strength will remain at about 20%. According to the calculation of the embodiment, the torque resistance capacity = 1.166Nm, which is about twice the bearing torque and is sufficient to resist the torque generated by the bearing rotation.

The following table shows the results of the actual rotation test of this embodiment and the comparison example without glue coating, which proves that the use of adhesive layer 6 can indeed increase the torque required for the rotation of the bearing outer ring 22. Moreover, under high temperature conditions, this embodiment can reduce the torque drop compared to the control group without glue coating. The column rotation torque in the following table refers to the torque required to rotate the experimental shaft.

The bearing 2 of this embodiment is very sensitive to the axial clearance after assembly, so the selected colloid must maintain a high elastic state after curing. And because the motor needs to withstand the maximum axial force P and operate at the maximum temperature rise T℃, the selected colloid must have a sufficiently high elastic deformation (elastic elongation); and when the axial force is applied toward the fixed ring 3 to generate the gap G (see Figure 7), the colloid near the chamfer 221 can still be maintained from being damaged or torn.

In this embodiment, the housing 1 is made of aluminum alloy, and the thickness of the casting is generally at least 2 mm; the cross-sectional area E of the housing 1 adjacent to the bearing 2 is approximately equal to the outer diameter circumference of the outer ring 22 multiplied by the minimum thickness of the aluminum alloy housing, that is, E=2π*Y(mm ² ). Under the action of the maximum axial force P(kN), stress S(Gpa) will be generated. Stress is force divided by area, so S=P/E.

According to Hooke's law, within the proportional limit, the ratio of stress S to strain is a constant. This ratio is called Young's modulus J (Gpa). Strain is stress (Gpa) divided by Young's modulus (Gpa), that is, strain is S/J.

The axial thickness of the housing 1 adjacent to the bearing 2 is L. When subjected to the maximum axial force P, the axial deformation G1 (mm) is the strain multiplied by the axial thickness L (mm), that is, G1 = SL/J.

This embodiment is used for specific explanation, wherein P=10kN. E=2*3.14*40=251.2mm ² . J=71Gpa (Young's modulus of aluminum alloy). L=12mm. Under the maximum axial force P, the outer shell 1 generates a stress S=10/251.2=0.0398Gpa at the adjacent bearing 2. Within the proportional limit, the axial deformation G1=0.0398*12/71=0.00673mm.

Since the thermal expansion coefficient of bearing steel (11.5μm/m℃) is approximately half of the thermal expansion coefficient of aluminum alloy (23.0μm/m℃), if the temperature rises by T℃, the relative deformation of bearing 2 and housing 1 is approximately 11.5*T μm/m. Therefore, when the axial thickness of bearing 2 is L(mm)=0.001L(m), an axial clearance G2=0.0115LT μm will be generated due to a temperature rise of T℃.

To illustrate this embodiment, the motor housing is subjected to a temperature rise from 20°C to 120°C (temperature difference 100°C), the axial thickness L of the bearing is 12mm, and the axial clearance G2=0.0115*L*Tμm=0.0115*12*100*μm=13.8μm=0.0138mm is generated due to the different axial thermal expansion coefficients.

Since the motor needs to operate under the maximum axial force P and the maximum temperature T, when the axial force or temperature change is large enough to cause strain between the bearing outer ring 22 and the outer housing 1, an axial gap G and a radial gap are generated between the bearing chamfer 221 and the outer housing 1, G=G1+G2.

Therefore, the colloid selected must have high elastic elongation. The colloid characteristics of the embodiment need to have an elongation of at least 50%. Under the maximum axial force P and high temperature T, the axial distance w between the bearing chamfer 221 and the outer shell 1 where the colloid can withstand the maximum elongation (see Figure 7, w is less than or equal to W) is the axial length of the colloid before deformation. The maximum elongation of the colloid is G/w. When the axial distance of the colloid before deformation is less than w, its elongation after deformation will exceed the maximum elongation that the colloid can withstand, and the adhesive layer 6 will be gradually destroyed.

This embodiment is specifically described, where W=0.4mm. Axial gap G=0.00673+0.0138=0.02053mm. The maximum elongation of the colloid is 50%=0.02053/w, w=0.04106mm. w accounts for 10.2% of the axial length W, so when the maximum elongation of the colloid is 50%, the colloid with w>0.04106mm will not fail due to the axial force and the gap caused by high temperature.

However, the above is only an example of the implementation of the present invention, and it cannot be used to limit the scope of the implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the patent of the present invention.

100: Motor

1: Shell

11: First wall part

12: Second wall section

122: Internal thread

13: Third wall section

131: Third ring groove

2: Bearings

3: Fixed ring

31: External thread

4: Stator assembly

5: Rotor assembly

6: Adhesive layer

Claims (6)

A motor comprises: a housing having a first wall defining a first annular groove, a second wall defining a second annular groove, a third wall defining a third annular groove, and an inner flange protruding radially from the end edge of the first wall toward the center, the first annular groove, the second annular groove and the third annular groove are coaxially arranged and arranged axially, and the second wall is provided with an inner thread; a bearing, accommodated in the first annular groove and bonded and fixed to the first wall with an adhesive layer; a fixing ring, accommodated in the second annular groove and provided with an outer thread matching the inner thread to be locked and fixed to the second wall; a stator assembly, accommodated in the third annular groove; and A rotor assembly is supported by the bearing and can be driven by the stator assembly to rotate around the axis. An electric motor as described in claim 1, wherein the bearing is accommodated in the first annular groove in a sliding assembly manner. An electric motor as described in claim 1, wherein the fixing ring and the inner flange jointly limit the bearing in the axial direction. An electric motor as described in claim 1, wherein a plurality of riveting grooves are formed at the connection between the fixing ring and the outer shell. The motor as described in claim 1, wherein the adhesive layer is formed of a colloid having an elongation of at least 50% and a shear strength of at least 3.0 MPa. In the motor as described in claim 1, most of the colloid in the adhesive layer is gathered at the chamfer of the outer ring of the bearing.

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