Electric Compressor

Abstract

This electric compressor comprises a housing for a motor that is a motive power source for a compressor unit, a rotor that rotates within the motor housing, a coil spring that urges the rotor in the direction of a rotational axis, a bearing that is interposed between the motor housing and the motor and that has an inner race supported on the rotor and an outer race abutted against an abutting part of the motor housing due to the urging of the coil spring, and a stopper that prevents the rotor from being displaced beyond a prescribed limit displacement amount against the urging of the coil spring and that allows displacement of the rotor short of the limit displacement amount, the length of the deformed coil spring being equal to or greater than the contact height when the rotor has been displaced to the limit displacement amount.

Description

[Technical field]

[0001] The present disclosure relates to an electric compressor. [Background technology]

[0002] Conventionally, as a technique in this field, a turbocharger described in the following Patent Document 1 is known. In this turbocharger, a bearing is interposed between a rotor and a housing, and the rotor is supported by the bearing. The turbocharger also includes a spring for applying pressure to the bearing in the axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 63-009428 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of rotary machine, when a bearing is interposed between the rotor and the housing, if the rotor is displaced in the axial direction due to vibration, the inner ring of the rotor and the outer ring of the housing may be misaligned in the axial direction. This may cause the bearing to disassemble. In view of this problem, the present disclosure describes an electric compressor that reduces the possibility of the bearing disassembly due to vibration. [Means for solving the problem]

[0005] An electric compressor according to one aspect of the present disclosure comprises a housing for a motor which is a power source for a compressor section, a rotor which rotates within the housing about a predetermined rotational axis, a pressure spring which urges the rotor in the direction of the rotational axis, a rolling bearing interposed between the housing and the motor and having an inner ring held by the rotor, and an outer ring which is abutted in the direction of the rotational axis against a predetermined abutment portion of the housing by the urging of the pressure spring, and a stopper which prohibits the rotor from being displaced beyond a predetermined limit displacement amount against the urging of the pressure spring, while allowing displacement of the rotor not exceeding the limit displacement amount, and when the rotor is displaced to the limit displacement amount, the length of the pressure spring after deformation is greater than or equal to the solid height. Effect of the Invention

[0006] According to the electric compressor of the present disclosure, the possibility of bearing disassembly due to vibration can be reduced. [Brief description of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view that illustrates a schematic diagram of an electric compressor according to an embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view showing an example of the vicinity of a bearing of the electric compressor shown in FIG. 1. [Diagram 3] 4 is a cross-sectional view showing a retainer, a stopper, and a coil spring in a limit displacement state. FIG. [Figure 4] 1A is a cross-sectional view showing the positional relationship between the rotor, bearings, etc. in the initial state, and FIG. [Diagram 5] 13(a) to 13(c) are cross-sectional views showing modified examples of the stopper. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An electric compressor according to one aspect of the present disclosure comprises a housing for a motor which is a power source for a compressor section, a rotor which rotates within the housing about a predetermined rotational axis, a pressure spring which urges the rotor in the direction of the rotational axis, a rolling bearing interposed between the housing and the motor and having an inner ring held by the rotor, and an outer ring which is abutted in the direction of the rotational axis against a predetermined abutment portion of the housing by the urging of the pressure spring, and a stopper which prohibits the rotor from being displaced beyond a predetermined limit displacement amount against the urging of the pressure spring, while allowing displacement of the rotor not exceeding the limit displacement amount, and when the rotor is displaced to the limit displacement amount, the length of the pressure spring after deformation is greater than or equal to the solid height.

[0009] In the electric compressor of the present disclosure, when the length of the pressure spring after deformation when the rotor is displaced to the limit displacement amount is L, the free length of the pressure spring is L0, and the solid height of the pressure spring is Lc, 20%≦(L0-L) / (L0-Lc)≦80% is satisfied.

[0010] The limit displacement may be smaller than the minimum amount of misalignment at which balls fall out when the inner and outer rings of the rolling bearing are misaligned relative to one another in the direction of the rotation axis. The rolling bearing may be an angular contact ball bearing installed in a direction that supports the thrust force of the pressure spring in the biasing direction. In the electric compressor of the present disclosure, when the rotor is displaced up to the limit displacement, the pressure spring after deformation may maintain an elastic repulsive force.

[0011] The stopper may be provided on the housing, and the displaced rotor may directly or indirectly interfere with the stopper. The stopper may be a retaining ring fitted into a groove extending in the circumferential direction on the inner peripheral surface of the housing. The stopper may be provided directly or indirectly on the rotor, and may be displaced together with the rotor to interfere with the housing.

[0012] Hereinafter, an electric compressor 1 according to an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a cross-sectional view that shows a schematic diagram of the electric compressor 1 according to the present embodiment. Note that, since the features related to the description may be exaggerated in each drawing, the dimensional ratios of the respective parts do not necessarily match between the drawings.

[0013] The electric compressor 1 is mounted on, for example, a vehicle, an aircraft, etc. For example, when the electric compressor 1 is mounted on a vehicle as a part of a two-stage turbocharger, the electric compressor 1 is used to compress air in the front stage of a turbocharger (not shown) and supply the compressed air to the turbocharger. In the following description, when the terms "axial direction", "radial direction", and "circumferential direction" are simply used, they mean the axial direction, radial direction, and circumferential direction of the rotation of an impeller 3 described below. Furthermore, when the terms "front", "rear", and the like are used in the following description, the side of a compressor section 2 described below (left side in FIG. 1) is the front side in the axial direction, and the side of a motor 5 (right side in FIG. 1) is the rear side.

[0014] The electric compressor 1 includes a compressor section 2 that compresses air. The compressor section 2 has an impeller 3 that rotates around a rotation axis H, and an impeller housing 11 that houses the impeller 3. The electric compressor 1 also includes a motor 5 as a power source for rotating the impeller 3. The electric compressor 1 also includes a housing 7 that houses the impeller 3 and the motor 5. As described above, the housing 7 includes the impeller housing 11 that houses the impeller 3, and the motor housing 13 that houses the motor 5. Note that the impeller housing 11 and the motor housing 13 may each be composed of multiple parts, and the parts that make up each housing and how they are combined can be designed freely.

[0015] The impeller housing 11 and the motor housing 13 are connected in the direction of the rotation axis H. A rotor 15 extending from inside the impeller housing 11 to inside the motor housing 13 exists on the rotation axis H. The impeller 3 is provided at the front end of the rotor 15, and the rotor 15 is rotated by the driving force of the motor 5. The motor 5 is composed of a coil 5a provided in the motor housing 13 and a magnet 5b provided on the rotor 15.

[0016] The impeller housing 11 has a diffuser 17 provided facing the outer periphery of the outlet of the impeller 3. The impeller housing 11 also has a scroll 19 provided on the outer periphery of the diffuser 17. The impeller housing 11 also has an intake port 21 that opens to the outside at a position axially facing the inlet of the impeller 3, and a discharge port 23 that is the outlet of the scroll 19.

[0017] When power is supplied to the motor 5, the rotor 15 rotates, causing the impeller 3 to rotate within the impeller housing 11. As a result, outside air is drawn into the impeller 3 in the axial direction through the air intake 21, and is discharged radially outward from the impeller outlet. The air from the impeller outlet flows into the diffuser 17, and is compressed through the diffuser 17 and the scroll 19. This compressed air is supplied to a turbocharger (not shown) through a discharge port 23.

[0018] Next, a bearing structure of the rotor 15 will be described. The electric compressor 1 has two bearings 27, 29 (rolling bearings) that support the rotor 15. The bearings 27, 29 are arranged on either side of the motor 5 in the axial direction, and are interposed between the outer circumferential surface of the rotor 15 and the inner circumferential surface of the motor housing 13. In the axial direction, the bearing 27 is located between the motor 5 and the impeller 3, and the bearing 29 is located at the rear end of the rotor 15.

[0019] The inner ring 27a of the bearing 27 is fitted to the outer circumferential surface of the rotor 15 by an interference fit. In this embodiment, the inner ring 27a is fitted to the small diameter portion 31 provided on the rotor 15. With this configuration, the inner ring 27a is prevented from moving in the axial direction relative to the rotor 15. On the other hand, the outer ring 27b of the bearing 27 is fitted to the inner circumferential surface of the motor housing 13 by a clearance fit. And, an abutment portion 13a (abutment portion) is provided at the front end of the inner circumferential surface of the motor housing 13. The abutment portion 13a protrudes radially inward from the inner circumferential surface of the motor housing 13, and the front end surface of the outer ring 27b abuts against the abutment portion 13a in the axial direction. With this configuration, the outer ring 27b can slide in the axial direction relative to the inner circumferential surface of the motor housing 13, but the abutment portion 13a restricts the outer ring 27b from moving forward.

[0020] In order to prevent creep of the outer ring 27b, the bearing 27 may be installed in the motor housing 13 via an O-ring. That is, as shown in FIG. 2, an O-ring 30 extending in the circumferential direction may be sandwiched between the outer peripheral surface of the outer ring 27b and the inner peripheral surface of the motor housing 13.

[0021] As shown in FIG. 1, the inner ring 29a of the bearing 29 is fitted to the outer circumferential surface of the rotor 15 by an interference fit. Furthermore, the inner ring 29a is fitted into a small diameter portion 32 provided at the rear end of the rotor 15, and the front end surface of the inner ring 29a abuts against a step of the small diameter portion 32. With this configuration, the inner ring 29a is prevented from moving in the axial direction relative to the rotor 15. Meanwhile, the outer ring 29b of the bearing 29 is fitted to the inner circumferential surface of the motor housing 13 by a clearance fit, so that the outer ring 29b can slide in the axial direction relative to the inner circumferential surface of the motor housing 13. Note that the bearing 29 may be installed in the motor housing 13 via an O-ring, similar to the bearing 27.

[0022] In addition, angular ball bearings are used for the bearings 27 and 29 so that they can function as both radial bearings and thrust bearings. The bearing 27 is installed in a direction that supports the forward thrust force of the rotor 15 (thrust force in the direction from the motor 5 to the impeller 3). That is, when the inner ring 27a of the bearing 27 receives a forward thrust force from the rotor 15, the thrust force is transmitted to the outer ring 27b via the balls 27c. The bearing 29 is installed in a direction that supports the rearward thrust force of the rotor 15 (thrust force in the direction from the impeller 3 to the motor 5). That is, when the inner ring 29a of the bearing 29 receives a rearward thrust force from the rotor 15, the thrust force is transmitted to the outer ring 29b via the balls 29c.

[0023] In the space behind the rotor 15 within the motor housing 13, a compression coil spring 35 (pressure spring) that expands and contracts in the axial direction and a retainer 37 that is biased forward by the coil spring 35 are disposed to pressurize the rotor 15. The retainer 37 is disk-shaped and has a protruding ridge 37a that protrudes forward along the front edge. The front end surface of the protruding ridge 37a abuts against the rear end surface of the outer ring 29b of the bearing 29. With this structure, the outer ring 29b of the bearing 29 is biased forward via the retainer 37 by the biasing force of the coil spring 35.

[0024] According to the bearing structure described above, when the outer ring 29b is pushed forward via the retainer 37 by the urging force of the coil spring 35, the inner ring 29a is pushed forward via the balls 29c. Then, the rotor 15 is pushed forward because the inner ring 29a is tightly fitted into the rotor 15. Then, the inner ring 27a of the bearing 27 is pushed forward because the inner ring 27a of the bearing 27 is tightly fitted into the rotor 15. Then, when the inner ring 27a is pushed forward, the outer ring 27b is pushed forward via the balls 27c, and the outer ring 27b is pressed against the abutment portion 13a of the motor housing 13. In this way, the rotor 15, the bearings 27, 29, and the retainer 37 are abutted against the abutment portion 13a by the urging force of the coil spring 35 and positioned as shown in FIG. The state in FIG. 1 in which rotor 15, bearings 27, 29, and retainer 37 are positioned in this manner is referred to as the "initial state", and the position of each component in the initial state is referred to as the "initial position".

[0025] Furthermore, the rotor 15 is capable of displacing rearward from the initial position against the bias of the coil spring 35. To regulate the amount of displacement of the rotor 15 to a predetermined amount or less, a stopper 41 is provided with a gap behind the retainer 37. The stopper 41 prohibits the rotor 15 from displacing beyond a predetermined limit displacement amount Q, while allowing displacement of the rotor 15 that does not exceed this limit displacement amount Q. The limit displacement amount Q corresponds to the amount of the axial gap between the rear end face of the retainer 37 and the stopper 41 in the initial state.

[0026] The stopper 41 is made of a snap ring. Specifically, a groove 42 extending in the circumferential direction is formed on the inner peripheral surface of the motor housing 13. The stopper 41 is a C-shaped snap ring having a shape in which a part of a ring is cut out. When assembling the electric compressor 1, the diameter of the stopper 41 is compressed, inserted into the inside of the motor housing 13, and fitted into the groove 42, so that the stopper 41 is installed. Since the radial width of the stopper 41 is wider than the depth of the groove 42, the inner peripheral side part of the stopper 41 protrudes inward from the inner peripheral surface of the motor housing 13. With this configuration, when the rotor 15 is displaced to the limit displacement amount Q, the stopper 41 interferes with the retainer 37, and the rotor 15 is prevented from moving further backward. By configuring the stopper 41 with the snap ring as described above, the assembly and disassembly of the part of the stopper 41 becomes easy.

[0027] Here, in applications where the electric compressor 1 is mounted on a vehicle or an aircraft, an impact load may be applied to the electric compressor 1 during operation. In this case, an axial inertial force is generated in the rotor 15 due to the axial component of the vibration caused by the impact load. According to the above-mentioned bearing structure, the forward inertial force is supported by the abutting portion 13a of the motor housing 13, and the rotor 15 does not displace from the initial position. On the other hand, when a rearward inertial force acts, the inertial force is supported by the coil spring 35, and the coil spring 35 is compressed, displacing the rotor 15 rearward from the initial position. In this way, when the electric compressor 1 vibrates, the rotor 15 displaces in the axial direction, but the amount of displacement is limited to the limit displacement amount Q or less.

[0028] Next, the setting of the aforementioned limit displacement amount Q will be described with reference to Fig. 3. Fig. 3 is a cross-sectional view showing the retainer 37, stopper 41, and coil spring 35 in the limit displacement state, and components other than those necessary for the description are omitted. In addition, in Fig. 3, the retainer 37 in the initial state is shown by a two-dot chain line. Hereinafter, the state in which the rotor 15 is displaced by the limit displacement amount Q (i.e., the state in which the retainer 37 abuts against the stopper 41) will be referred to as the "limit displacement state," and the position of the rotor 15 in the limit displacement state will be referred to as the "limit displacement position."

[0029] As described above, the limit displacement amount Q corresponds to the amount of the axial gap between the rear end face of the retainer 37 and the stopper 41 in the initial state, so the limit displacement amount Q can be appropriately set by appropriately setting the arrangement of the stopper 41. The arrangement of the stopper 41 is set so as to satisfy all of the following conditions C1 to C4.

[0030] [Condition C1] The length L of the coil spring 35 in the limit displacement state is equal to or greater than the solid height of the coil spring 35. In other words, the coil spring 35 in the limit displacement state still has the capacity to be further compressed in the axial direction. If the stopper 41 did not exist, the retainer 37 would be able to further compress the coil spring 35 from the limit displacement state and displace it rearward.

[0031] Here, if the usage state of the coil spring 35 is designed in accordance with Section 6.1 of JIS B 2704-1:2018, the length L1 of the coil spring 35 during usage satisfies the following formula (1). 20%≦(L0-L1) / (L0-Lc)≦80% …(1) Therefore, in this case, as an example of a range that satisfies condition C1, the length L of the coil spring 35 in the limit displacement state is set within a range that satisfies the following formula (2), that is, the arrangement of the stopper 41 is set so as to satisfy the following formula (2). 20%≦(L0-L) / (L0-Lc)≦80% …(2) In the formulas (1) and (2), L0 is the free length of the coil spring 35, and Lc is the solid height of the coil spring 35.

[0032] The "solid height" of the coil spring 35 in the above condition C1 may be determined by a prior test. When a commercially available general-purpose product is used as the coil spring 35, the "solid height" in the above condition C1 may be determined based on the specifications of the general-purpose product. The "solid height" in the above condition C1 refers to the "solid height" defined in JIS B 2704-1:2018.

[0033] [Condition C2] The limit displacement amount Q is smaller than the minimum deviation amount (hereinafter referred to as α) that causes the bearing 27 to come off when the inner ring 27a and the outer ring 27b of the bearing 27 are relatively deviated in the axial direction. In other words, even if the inner ring 27a and the outer ring 27b of the bearing 27 are misaligned relative to each other in the axial direction, if the amount of misalignment is smaller than α, the bearing 27 will not come off. The minimum amount of misalignment α between the inner ring 27a and the outer ring 27b that causes the bearing 27 to come off may be found by a prior test.

[0034] [Condition C3] The coil spring 35 in the limit displacement state maintains its elastic repulsive force. That is, the deformation state of the coil spring 35 in the limit displacement state is within the elastic deformation range, and if the rotor 15 moves forward, the coil spring 35 elastically returns to its original state. Between the initial state and the limit displacement state, the coil spring 35 elastically deforms reversibly. The range of the "state in which the elastic repulsive force is maintained" in the above condition C3 may be determined by a prior test. In addition, when a commercially available general-purpose product is used as the coil spring 35, the range of the "state in which the elastic repulsive force is maintained" in the above condition C3 may be determined based on the specifications of the general-purpose product.

[0035] [Condition C4] When the rotor 15 thermally expands in the axial direction relative to the motor housing 13, an axial gap remains between the rear end face of the retainer 37 and the stopper 41 in the initial state. The rotor 15 and the motor housing 13 each thermally expand in the axial direction due to heat generated during operation of the electric compressor 1. At this time, when the rotor 15 expands more in the axial direction than the motor housing 13, this difference in thermal expansion is absorbed by the contraction of the coil spring 35. According to condition C4, even when the axial thermal expansion of the rotor 15 relative to the motor housing 13 reaches a maximum, an axial gap still remains between the rear end face of the retainer 37 and the stopper 41.

[0036] Next, a description will be given of the operation and effect of the electric compressor 1. In the electric compressor 1, the stopper 41 is provided in such a position as to satisfy the above conditions C1 to C4.

[0037] The effect of satisfying condition C2 is as follows. Fig. 4(a) shows the positional relationship of the rotor 15, bearings 27, 29, etc. in the initial state, and Fig. 4(b) shows the positional relationship of the rotor 15, bearings 27, 29, etc. in the limit displacement state. In Fig. 4, parts other than those necessary for explanation are omitted. During operation of the electric compressor 1, the outer ring 27b of the bearing 27 may be tightly fitted into the motor housing 13 due to differences in thermal expansion of each part, etc. Alternatively, when an O-ring 30 (see Fig. 2) is present between the outer ring 27b and the motor housing 13, the frictional force of the O-ring 30 may prevent the outer ring 27b and the motor housing 13 from sliding smoothly in the axial direction.

[0038] In this state, if a backward inertial force acts on the rotor 15 and the rotor 15 is displaced by the limit displacement amount Q, as shown in Fig. 4(b), the rotor 15, the bearing 29, and the inner ring 27a of the bearing 27 are displaced backward, while the outer ring 27b is fixed to the motor housing 13 and cannot follow the above displacement. As a result, the inner ring 27a is displaced axially backward relative to the outer ring 27b, that is, the inner ring 27a and the outer ring 27b are misaligned in the axial direction. The amount of this displacement is the maximum limit displacement amount Q, as shown in Fig. 4(b).

[0039] Here, due to the nature of angular contact ball bearings, if the axial misalignment between inner ring 27a and outer ring 27b becomes equal to or greater than α, there is a high possibility that balls will come off and bearing 27 will come apart. In contrast, in electric compressor 1, limit displacement Q is smaller than α by satisfying condition C2 above, so that the displacement of rotor 15 during operation is kept smaller than α, and as a result, the axial misalignment between inner ring 27a and outer ring 27b is prevented from becoming equal to or greater than α. Therefore, bearing 27 is prevented from coming apart during operation.

[0040] Here, if we consider a case where condition C1 is not satisfied, the coil spring 35 is compressed to the solid height before the retainer 37 interferes with the stopper 41. In that case, the coil spring 35 cannot be further compressed, and further rearward displacement of the retainer 37 is prohibited. Therefore, if condition C1 is not satisfied, the retainer 37 does not interfere with the stopper 41, and the stopper 41 has no function. In contrast, in the electric compressor 1, if condition C1 is satisfied, when the rotor 15 displaces rearward during operation, the stopper 41 prevents the rotor 15 from displacing rearward before the coil spring 35 reaches the solid height.

[0041] Furthermore, when the above-mentioned formula (2) in condition C1 is not satisfied (particularly when (L0-L) / (L0-Lc) exceeds 80%), the length L1 of the coil spring 35 deviates from the range of the above-mentioned formula (1) before the retainer 37 interferes with the stopper 41, which is undesirable. In contrast, when the formula (2) is satisfied in the electric compressor 1, when the rotor 15 is displaced rearward during operation, the stopper 41 prevents the rotor 15 from displacing rearward before the length L1 of the coil spring 35 deviates from the range of the formula (1). Therefore, the deformation amount of the coil spring 35 can be suppressed within the range in accordance with Section 6.1 of JIS B 2704-1:2018.

[0042] Furthermore, by satisfying condition C3, it is possible to prevent the coil spring 35 from being deformed beyond the elastic deformation region even when the rotor 15 is displaced by the limit displacement amount Q. As a result, it is possible to prevent the coil spring 35 from being damaged, such as by remaining irreversible deformation. Furthermore, by satisfying condition C4, it is possible to absorb the difference in axial thermal expansion between the rotor 15 and the motor housing 13 that thermally expand during operation, by the gap between the rear end face of the retainer 37 and the stopper 41.

[0043] In order to suppress the amount of axial misalignment between the inner ring 27a and the outer ring 27b of the bearing 27 during operation, instead of providing the stopper 41, it is possible to configure the coil spring 35 to have a higher spring rigidity. However, this configuration requires highly accurate management of the set dimensions of the coil spring 35, which may increase the manufacturing cost of the electric compressor 1. In addition, if the spring rigidity of the coil spring 35 is increased, the reaction force of the coil spring 35 generated by dimensional changes due to thermal expansion or the like increases. This increases friction between the balls 27c, the inner ring 27a, and the outer ring 27b of the bearing 27, which increases thermal deterioration of the grease, shortening the life of the bearing 27. Similarly, the life of the bearing 29 is also shortened. In contrast, the electric compressor 1 avoids the above problems.

[0044] The present disclosure can be implemented in various forms including the above-described embodiment and various modifications and improvements based on the knowledge of those skilled in the art. In addition, it is possible to configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of each embodiment may be used in appropriate combination.

[0045] For example, the configuration of electric compressor 1 including stopper 41 is particularly necessary and suitable for electric compressors mounted on vehicles or aircraft that are subject to random vibration and shock. Also, the configuration of electric compressor 1 including stopper 41 can be applied as a measure against earthquake vibrations not only to electric compressors mounted on vehicles or aircraft but also to stationary electric compressors. Also, in the above-mentioned embodiment, bearings 27, 29 are angular ball bearings, but bearings 27, 29 are not limited to this and may be deep groove bearings.

[0046] 5(a) to (c) are cross-sectional views showing modified examples near the retainer 37. In FIG. 5, the retainer 37 in the initial state and its vicinity are shown, and parts other than those necessary for the explanation are omitted. The stopper for restricting the displacement of the rotor 15 is not limited to the stopper 41 which is a retaining ring, and may be any stopper provided in the motor housing 13 with which the displaced rotor 15 directly or indirectly interferes. For example, instead of the stopper 41, a ring-shaped stopper 45 may be provided behind the retainer 37 along the inner peripheral surface of the motor housing 13 as shown in FIG. 5(a). Also, a step-shaped stopper 46 that interferes with the retainer 37 behind the retainer 37 may be provided on the inner peripheral surface of the motor housing 13 as shown in FIG. 5(b). Also, the stoppers 41, 45, and 46 interfere with the retainer 37 (i.e., with which the rotor 15 indirectly interferes), but the stopper may be configured so that the rotor 15 directly interferes with it.

[0047] The stopper for restricting the displacement of the rotor 15 may be provided directly or indirectly on the rotor 15 and may be displaced together with the rotor 15 to interfere with the motor housing 13. As an example of this, as shown in FIG. 5(c), a stopper 47 protruding rearward may be provided on the rear surface side of the retainer 37. The stopper 47 is accommodated in the hollow space of the coil spring 35, and the rear end surface of the stopper 47 faces the inner wall surface 13d of the motor housing 13 with a gap corresponding to the limit displacement amount Q. The stopper is not limited to a stopper provided on the retainer 37 (i.e., a stopper provided indirectly on the rotor 15), and a stopper provided directly on the rotor 15 may interfere with the inner wall of the motor housing 13, etc. [Explanation of symbols]

[0048] 1 Electric compressor 2 Compressor section 5 Motor 13 Motor housing 13a Abutment part (Abutment part) 15 Rotor 27 Bearings (rolling bearings) 27a Inner Circle 27b Outer ring 35 Coil spring (pressurized spring) 41,45,46,47 Stopper H Rotation axis Q Limit Displacement

Claims

1. A housing for a motor that is the power source for the compressor section; a rotor that rotates within the housing about a predetermined rotation axis; a pressure spring that biases the rotor forward along the direction of the rotation axis; a rolling bearing interposed between the housing and the motor, the rolling bearing including an inner ring held by the rotor and an outer ring abutted against a predetermined abutment portion of the housing in the direction of the rotation axis by the bias of the pressure spring; a stopper that prohibits the rotor from being displaced beyond a predetermined limit displacement amount against the bias of the pressure spring and allows the rotor to be displaced not exceeding the limit displacement amount, the rolling bearing has functions of both a radial bearing and a thrust bearing, is disposed on the front side of the pressure spring with the motor interposed therebetween, and is disposed in a direction to support the forward thrust force of the rotor, The outer ring is abutted against the abutment portion at the front side, When the rotor is displaced to the limit displacement amount, the length of the pressure spring after deformation is equal to or greater than a solid height, The limiting displacement amount is smaller than a minimum amount of misalignment at which ball separation occurs when the inner ring and the outer ring of the rolling bearing are misaligned relatively in the direction of the rotation axis.

2. When the length of the pressure spring after deformation when the rotor is displaced to the limit displacement amount is L, the free length of the pressure spring is L0, and the solid height of the pressure spring is Lc, 20%≦(L0-L) / (L0-Lc)≦80% 2. The electric compressor according to claim 1, wherein the following is satisfied.

3. 3. The electric compressor according to claim 1, wherein the rolling bearing is an angular contact ball bearing.

4. 4. The electric compressor according to claim 1, wherein when the rotor is displaced to the limit displacement amount, the pressure spring after deformation maintains an elastic repulsive force.

5. 5. The electric compressor according to claim 1, wherein the stopper is provided on the housing, and the displaced rotor directly or indirectly interferes with the stopper.

6. 6. The electric compressor according to claim 5, wherein the stopper is a retaining ring fitted into a groove extending in a circumferential direction on an inner peripheral surface of the housing.

7. 5. The electric compressor according to claim 1, wherein the stopper is provided directly or indirectly on the rotor, and displaces together with the rotor to interfere with the housing.

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