Power transmission shaft for vehicle

Abstract

To provide a power transmission shaft for a vehicle that comprises a structure capable of suppressing NV.SOLUTION: A first small diameter part D is arranged on one side with respect to a contact surface 48a of a flange part 48 that is in contact with a bearing, and a second small diameter part C is arranged on the opposite side to the first small diameter part D from the contact surface 48a of the flange part 48, where the second small diameter part C has a smaller diameter than the first small diameter part D (A<B) and an axial length c equal to or larger than an axial length d of the first small diameter part D (c≥d). A torsional rigidity Ts2 of the second small diameter part C is relatively lower than a torsional rigidity Ts1 of the first small diameter part. In other words, NV can be suppressed by extending the second small diameter part C, which has the relatively low torsional rigidity Ts2, and lowering a torsional rigidity Ts as a power transmission shaft.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a power transmission shaft for a vehicle that suppresses vibration and noise. [Background technology]

[0002] 2. Description of the Related Art A well-known power transmission shaft for a vehicle includes a power transmission section connected to an output shaft that outputs power from a drive device such as an engine or a motor, and a gear section that transmits the power transmitted to the power transmission section to another device via a gear connection.

[0003] Incidentally, in the power transmission shaft for a vehicle, it is important to suppress vibrations and noise (hereinafter referred to as NV) that are generated due to propagation from the drive device, rattles at connection points, etc. Patent Document 1 discloses a technology for suppressing this NV. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-175261 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the NV is suppressed by applying a thrust force to the shaft, but the power transmission shaft has a large torsional rigidity and has a structure in which the NV is likely to occur.

[0006] The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a power transmission shaft for a vehicle having a structure capable of suppressing NV. [Means for solving the problem]

[0007] The gist of the present invention is that (a) a power transmission shaft for a vehicle, having a connecting portion formed at one end for connection to another power transmission member, a gear formed at the other end, a flange portion for transmitting thrust force formed at an intermediate portion supported by a bearing, a first small diameter portion disposed on one side of a contact surface of the flange portion that contacts the bearing, and a second small diameter portion having a diameter smaller than the first small diameter portion disposed on the opposite side of the contact surface of the flange portion, and (b) the second small diameter portion has an axial length equal to or greater than the first small diameter portion. Effect of the Invention

[0008] In such a power transmission shaft for a vehicle, a coupling portion that is coupled to another power transmission member is formed at one end, a gear is formed at the other end, a flange portion that transmits thrust force is formed at an intermediate portion supported by a bearing, a first small diameter portion is disposed on one side of a contact surface of the flange portion that contacts the bearing, and a second small diameter portion having a diameter smaller than that of the first small diameter portion is disposed on the opposite side of the contact surface of the flange portion, wherein the second small diameter portion has an axial length equal to or greater than that of the first small diameter portion. In other words, the NV can be suppressed by extending the second small diameter portion C, which has a relatively low torsional rigidity, to reduce the torsional rigidity of the power transmission shaft. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view specifically showing a portion in the vicinity of a vehicle power transmission shaft according to an embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view showing a further enlarged view of the vicinity of the vehicle power transmission shaft in FIG. 1. [Diagram 3] FIG. 3 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating another embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. [Diagram 5] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. [Figure 6] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. [Figure 8] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. [Figure 9] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. [Figure 11] FIG. 10 is a cross-sectional view of a power transmission shaft for a vehicle corresponding to FIG. 2, illustrating still another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified for the purpose of explanation, and the dimensional ratios, shapes, angles, etc. of each part are not necessarily drawn accurately. EXAMPLES

[0011] 1 is a cross-sectional view specifically showing a portion of a vehicle power transmission shaft according to an embodiment of the present invention, in which the shaft is disposed. The motor generator MG2 disposed on the axis S3 is used alternatively as an electric motor or a generator in a hybrid vehicle, and when functioning as an electric motor, is used as a driving force source for running the vehicle.

[0012] A vehicle power transmission shaft (hereinafter referred to as a gear shaft) 42 is used to transmit power between the motor generator MG2 and a countershaft (not shown) that rotates and drives drive wheels (not shown). The gear shaft 42 is connected by fitting a splined fitting portion 46 formed at one end to a rotor shaft 44 of the motor generator MG2. The splined fitting portion 46 functions as a connecting portion that connects the gear shaft 42 to other power transmission members. The gear shaft 42 is connected by meshing a motor output gear (hereinafter referred to as a gear) 40 formed at the other end with a gear of a countershaft (not shown) that rotates and drives drive wheels. The gear 40 is a helical gear, and generates a thrust force when transmitting power.

[0013] The gear shaft 42 functions as a drive shaft that transmits the power of the motor generator MG2 to the counter shaft to rotate and drive the drive wheels, and also receives the power of the engine and the like from the counter shaft via a power split mechanism (not shown) and the gear 40 to the gear shaft 42. During coasting or the like, reverse input rotation (driven rotation) is transmitted from the drive wheels to the gear shaft 42 from the counter shaft via a differential device (not shown).

[0014] Gear shaft 42 is a cylindrical member, and is supported by case 64 via a pair of bearings 60 and 62 so as to be rotatable about an axis concentric with axis S3. A flange portion 48 for transmitting thrust force to bearing 60 is formed at the middle portion of gear shaft 42. Rotor shaft 44 is also a cylindrical member, and is supported by case 64 via a pair of bearings 66 and 68 so as to be rotatable about an axis concentric with axis S3, i.e., gear shaft 42. A rotor 70 of motor generator MG2 is connected to the axial center portion of rotor shaft 44 so as not to rotate relative to the rotor 70, and the rotation of motor generator MG2 is transmitted to the rotor 70.

[0015] Incidentally, in the power transmission of the gear shaft 42, it is an issue to suppress vibrations and noises, that is, NV, which are generated due to transmission from a driving device such as the motor generator MG2 or the engine, or due to backlash at the connection points. For example, the gear shaft 42 and the rotor shaft 44 are connected to be able to transmit power via a splined engagement portion 46, but the splined engagement portion 46 has engagement backlash (circumferential and radial play) due to runout of the tooth grooves. For this reason, due to relative rotation fluctuations of the gear shaft 42 and the rotor shaft 44 caused by torque fluctuations accompanying engine explosions, etc., the external spline teeth of the gear shaft 42 and the internal spline teeth of the rotor shaft 44 may repeatedly separate and collide with each other, generating rattling noise (tooth rattling noise). In addition, it is assumed that noise generated from the motor generator MG2 or the engine may be transmitted via the gear shaft 42, causing the case 64 to resonate and sympathize, thereby worsening the NV.

[0016] To suppress the above-mentioned NV, it is effective to reduce the torsional rigidity Ts of the gear shaft 42. That is, lowering the torsional rigidity Ts while maintaining the strength and quality as a power transmission shaft is effective in suppressing NV. The torsional rigidity Ts [Nm / rad] of the cylindrical member corresponding to the gear shaft 42 is calculated by the following formula (1). Ts = π / 32 × (D 4 -d 4 ) × G / L ···(1) Here, D is the outer diameter of the shaft, d is the inner diameter of the shaft, G is the transverse elastic modulus of the shaft material, and L is the shaft length. From equation (1), the smaller the shaft diameter is, the lower the torsional rigidity Ts is, and the longer the shaft length is, the lower the torsional rigidity Ts is.

[0017] In the gear shaft 42 of this embodiment, by making the shaft portion on one side from the flange portion 48 have a small diameter and a long structure, the torsional rigidity Ts as a power transmission shaft is suitably reduced to suppress NV. Hereinafter, a specific embodiment will be described with reference to FIG. 2. FIG. 2 is a cross-sectional view showing an enlarged view of the vicinity of the gear shaft 42 in FIG. 1. In FIG. 2, the portion shown on the left side of the paper surface from the contact surface 48a of the flange portion 48 is the second small-diameter portion C with a shaft diameter of diameter A, and the portion shown on the right side of the paper surface from the contact surface 48a of the flange portion 48 is the first small-diameter portion D with a shaft diameter of diameter B. The torsional rigidity Ts2 of the second small-diameter portion C is relatively lower than the torsional rigidity Ts1 of the first small-diameter portion because the shaft diameter is smaller (A < B) when the shaft lengths are the same. The second small-diameter portion C with a smaller diameter (A < B) than the first small-diameter portion D has a shaft length c (c ≧ d) that is equal to or greater than the shaft length d of the first small-diameter portion D, and by extending the second small-diameter portion C with relatively low torsional rigidity Ts2, the torsional rigidity Ts as a power transmission shaft is reduced.

[0018] According to the gear shaft 42 of this embodiment, the second small-diameter portion C with a smaller diameter (A < B) than the first small-diameter portion D has a shaft length c (c ≧ d) that is equal to or greater than the shaft length d of the first small-diameter portion D. That is, by extending the second small-diameter portion C with relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as a power transmission shaft, NV can be suppressed.

Embodiment

[0019] Next, another embodiment of the present invention will be described. In the following description, parts common to the above-described embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

[0020] In FIG. 3, the portion shown on the left side of the paper surface from the contact surface 48a of the flange portion 48 is the first small-diameter portion D with a shaft diameter of diameter B, and the portion shown on the right side of the paper surface from the contact surface 48a of the flange portion 48 is the second small-diameter portion C with a shaft diameter of diameter A. The second small-diameter portion C with a smaller diameter (A < B) than the first small-diameter portion D has a shaft length c (c ≧ d) that is equal to or greater than the shaft length d of the first small-diameter portion D, and by extending the second small-diameter portion C with relatively low torsional rigidity Ts2, the torsional rigidity Ts as a power transmission shaft is reduced.

Embodiment

[0021] In FIG. 4, with respect to Example 1 of FIG. 2, the axial length d of the first small-diameter portion D and the axial length c of the second small-diameter portion C are made the same length (c = d). The second small-diameter portion C having a smaller diameter (A < B) than the first small-diameter portion D has the same axial length c (c = d) as the axial length d of the first small-diameter portion D, and extends the second small-diameter portion C having a relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as the power transmission shaft.

Example

[0022] In FIG. 5, with respect to Example 1 of FIG. 2, the contact partner of the flange portion 48 for transmitting the thrust force is changed from the bearing 60 to the extension portion 44a of the rotor shaft 44. The second small-diameter portion C having a smaller diameter (A < B) than the first small-diameter portion D has an axial length c (c ≧ d) equal to or greater than the axial length d of the first small-diameter portion D, and extends the second small-diameter portion C having a relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as the power transmission shaft.

Example

[0023] FIG. 6 shows an example in which, from Example 1 of FIG. 2, the contact partner of the flange portion 48 for transmitting or receiving the thrust force is changed from the bearing 60 to the case 64. The second small-diameter portion C having a small diameter A (A < B) has a length equal to or greater than the first small-diameter portion D (c ≧ d), and extends the second small-diameter portion C having a relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as the power transmission shaft.

Example

[0024] FIG. 7 shows an example in which the spline fitting (spline fitting portion 46) in Example 1 of FIG. 2 is changed to a spline fitting (spline fitting portion 46a) between the inner spline teeth of the gear shaft 42 and the outer spline teeth of the rotor shaft 44. The spline fitting portion 46a functions as a connecting portion for connecting the gear shaft 42 to another power transmission member. The second small-diameter portion C having a smaller diameter (A < B) than the first small-diameter portion D has an axial length c (c ≧ d) equal to or greater than the axial length d of the first small-diameter portion D, and extends the second small-diameter portion C having a relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as the power transmission shaft.

Example

[0025] Figure 8 shows an embodiment in which the connection between the rotor shaft 44 and the gear shaft 42 in the first embodiment of FIG. 2 is changed from a spline fit (spline fitting portion 46) to a press fit of the gear shaft 42 onto the rotor shaft 44 (press fit portion 46b). The press fit portion 46b functions as a connecting portion for connecting the gear shaft 42 to another power transmission member. The second small diameter portion C having a smaller diameter (A < B) than the first small diameter portion D has a shaft length c (c ≧ d) equal to or greater than the shaft length d of the first small diameter portion D, and by extending the second small diameter portion C having a relatively low torsional rigidity Ts2, the torsional rigidity Ts as a power transmission shaft is reduced.

Embodiment

[0026] Figure 9 shows an embodiment in which the connection between the rotor shaft 44 and the gear shaft 42 in the first embodiment of FIG. 2 is changed from a spline fit (spline fitting portion 46) to an adhesion or welding between the rotor shaft 44 and the gear shaft 42 (adhesion / welding portion 46c). The adhesion / welding portion 46c functions as a connecting portion for connecting the gear shaft 42 to another power transmission member. The second small diameter portion C having a smaller diameter (A < B) than the first small diameter portion D has a shaft length c (c ≧ d) equal to or greater than the shaft length d of the first small diameter portion D, and by extending the second small diameter portion C having a relatively low torsional rigidity Ts2, the torsional rigidity Ts as a power transmission shaft is reduced.

Embodiment

[0027] Figure 10 shows an embodiment in which the connection between the rotor shaft 44 and the gear shaft 42 in the first embodiment of FIG. 2 is changed from a spline fit (spline fitting portion 46) to an adhesion or welding between the tip of the rotor shaft 44 and the tip of the gear shaft 42 (adhesion / welding portion 46d). The adhesion / welding portion 46d functions as a connecting portion for connecting the gear shaft 42 to another power transmission member. The second small diameter portion C having a smaller diameter (A < B) than the first small diameter portion D has a shaft length c (c ≧ d) equal to or greater than the shaft length d of the first small diameter portion D, and by extending the second small diameter portion C having a relatively low torsional rigidity Ts2, the torsional rigidity Ts as a power transmission shaft is reduced.

Embodiment

[0028] FIG. 11 shows an embodiment in which the connection between the rotor shaft 44 and the gear shaft 42 in the first embodiment of FIG. 2 is changed from a spline fit (spline fitting portion 46) to a gear connection between the drive gear 44b of the rotor shaft 44 and the transmission gear 42b of the gear shaft 42. The transmission gear 42b functions as a connecting portion for connecting the gear shaft 42 to another power transmission member. The second small-diameter portion C having a smaller diameter (A < B) than the first small-diameter portion D has a shaft length c (c ≧ d) equal to or greater than the shaft length d of the first small-diameter portion D, and extends the second small-diameter portion C having a relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as a power transmission shaft.

[0029] According to the gear shaft 42 of the second to eleventh embodiments, the second small-diameter portion C having a smaller diameter (A < B) than the first small-diameter portion D has a shaft length c (c ≧ d) equal to or greater than the shaft length d of the first small-diameter portion D. That is, by extending the second small-diameter portion C having a relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as a power transmission shaft, NV can be suppressed.

[0030] Thus, according to the gear shaft 42 of the present embodiment, the second small-diameter portion C having a smaller diameter (A < B) than the first small-diameter portion D has a shaft length c (c ≧ d) equal to or greater than the shaft length d of the first small-diameter portion D. That is, by extending the second small-diameter portion C having a relatively low torsional rigidity Ts2 to reduce the torsional rigidity Ts as a power transmission shaft, NV can be suppressed.

[0031] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, these are merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0032] 40: Gear (motor output gear) 42: Gear shaft (vehicle power transmission shaft) 46: Spline fitting portion 48: Flange portion 48a: Contact surface C: Second small-diameter portion D: First small-diameter portion

Claims

[Claim 1] A power transmission shaft for a vehicle, the shaft having a coupling portion formed at one end thereof for coupling to another power transmission member, a gear formed at the other end thereof, a flange portion for transmitting thrust force formed at an intermediate portion supported by a bearing, a first small diameter portion disposed on one side of a contact surface of the flange portion that contacts the bearing, and a second small diameter portion having a diameter smaller than that of the first small diameter portion disposed on the opposite side of the contact surface of the flange portion, 13. A power transmission shaft for a vehicle, wherein the second small diameter portion has an axial length equal to or greater than that of the first small diameter portion.

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