Heat shield structure of vehicle propeller shaft

Abstract

To provide a heat shield structure of a vehicle propeller shaft which takes measures for improving strength, including downsizing of a heat shield member and prevention of cracks, and maintains conventional heat shield and cooling functions.SOLUTION: A heat shield member 42 is supported through a bearing 44 by a tip of a connecting shaft 18 in a manner that enables relative rotation therebetween and is fixed by an elastic member 50 located between the heat shield member 42 and a fixing part 48 of a steering gear box 46 located at the opposite side of an exhaust pipe (a heat source) 30 with respect to the center axis C2 of the connecting shaft 18. Further, in the heat shield member 42, a length along the center axis C2 of the connection shaft 18 of a shield side 42a facing the exhaust pipe 30 is formed longer than a length along the center axis C2 of the connecting shaft 18 at an opening side 42b. In the structure, a joint part 10a is covered at the shielding side 42a and shielded from radiation heat of the exhaust pipe 30 and the opening side 42b is open to be exposed to outside air. Thus, the joint part 10a is cooled.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a heat insulation structure for a vehicle propeller shaft, which has a heat insulation member for suppressing a temperature rise in the vehicle propeller shaft. [Background technology]

[0002] A heat-shielding structure for a vehicle propeller shaft is known, which includes a vehicle propeller shaft extending in the front-rear direction of the vehicle and a heat-shielding member disposed radially outside the vehicle propeller shaft. For example, the heat-shielding structure for a vehicle propeller shaft described in Patent Document 1 is such a structure. In the heat-shielding structure for a vehicle propeller shaft described in Patent Document 1, a heat-shielding member is provided between the joint portion of the vehicle propeller shaft and the exhaust pipe in order to protect the joint portion of the vehicle propeller shaft from radiant heat from an exhaust pipe provided near the vehicle propeller shaft. As a result, the radiant heat from the exhaust pipe is blocked or reflected by the heat-shielding member, thereby suppressing a temperature rise in the joint portion of the vehicle propeller shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-206132 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the heat-shielding structure for a vehicle propeller shaft described in Patent Document 1, the heat-shielding member longitudinally covers a joint portion of the vehicle propeller shaft connected to a connecting shaft protruding from a transfer, and is attached in a cantilever shape with a base end fastened to the transfer and a tip end as a free end so as to be located at the joint portion of the vehicle propeller shaft and in the vicinity of the joint portion. Therefore, there is a problem that the heat-shielding member is large because it needs to be extended from the base end to the joint portion that requires heat-shielding protection, including the length of the connecting member, and furthermore, because the heat-shielding member has a cantilever structure, stress is concentrated at the base end, making the base end prone to cracking.

[0005] The present invention has been made against the background of the above circumstances, and its object is to provide a heat-shielding structure for a vehicle propeller shaft which reduces the size of the heat-shielding member and improves its strength, including preventing the occurrence of cracks, while maintaining the conventional heat-shielding and cooling functions. [Means for solving the problem]

[0006] The gist of the present invention is a heat-shielding structure for a vehicle propeller shaft, including: (a) a propeller shaft extending in a fore-and-aft direction and connected via a joint portion to the end of a connecting shaft protruding from a vehicle transfer; and a cylindrical heat-shielding member that shields the joint portion of the propeller shaft from radiation of a heat source, (b) the cylindrical heat-shielding member is supported via a bearing at the end of the connecting shaft so as to be rotatable relative to the heat source, and is connected via an elastic member to a steering gear box located on the opposite side of the central axis of the connecting shaft from the heat source, and (c) the length of the cylindrical heat-shielding member along the central axis of the connecting shaft on the heat source side is longer than the length along the central axis of the connecting shaft on the opposite side of the heat source. Effect of the Invention

[0007] According to the heat insulation structure for a vehicle propeller shaft of the present invention, the cylindrical heat insulation member is supported via a bearing at the tip portion of the connecting shaft so as to be rotatable relative to the heat source, and is connected via an elastic member to a steering gear box located on the opposite side of the central axis of the connecting shaft from the heat source, and the length of the cylindrical heat insulation member along the central axis of the connecting shaft on the heat source side is longer than the length along the central axis of the connecting shaft on the opposite side of the heat source from the central axis of the connecting shaft. As a result, the cylindrical heat insulation member is supported at the tip portion of the connecting shaft via the bearing, and is fixed via an elastic member to the steering gear box located on the opposite side of the central axis of the connecting shaft from the heat source so as not to be rotatable relative to the heat source, thereby eliminating a cantilever structure when fastening the heat insulation member to the transfer, and making it possible to reduce the size of the heat insulation member and improve its strength, including preventing the occurrence of cracks. Furthermore, the cylindrical heat shielding member is formed such that the length along the central axis of the connecting shaft on the heat source side is longer than the length along the central axis of the connecting shaft on the opposite side to the heat source, so that the joint part is covered by the shielding side against the radiant heat of the heat source, while the opposite side to the heat source is opened and exposed to the outside air, thereby cooling the joint part, thereby maintaining the conventional heat shielding and cooling functions. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a main part of a heat insulating structure for a vehicle propeller shaft according to a conventional example. [Diagram 2] 1 is a diagram illustrating a main portion of a heat insulating structure for a vehicle propeller shaft to which the present invention is applied; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. EXAMPLES

[0010] Fig. 1 is an enlarged view for explaining a main part of a heat shielding structure 20 for a vehicle propeller shaft 10 (hereinafter referred to as the propeller shaft 10) according to a conventional example, where (a) in Fig. 1 is a perspective view and (b) in Fig. 1 is a side view of (a) in Fig. 1 as viewed from the left side of the paper, i.e., the left side of a vehicle 14. The propeller shaft 10 is a power transmission shaft provided in a vehicle 14 for transmitting power output from an engine (not shown) as a power source to driving wheels (not shown). The propeller shaft 10 is disposed, for example, between a transmission mechanism including a gearbox (not shown) connected to the power source, and a differential mechanism including a vehicle differential gear device (not shown) connected to the axles of the driving wheels. For example, if the vehicle 14 is a four-wheel drive vehicle, the power output from the engine is transmitted to a secondary drive wheel, such as a rear wheel (not shown), via a transfer 16, which transmits a portion of the power transmitted from the power source to a primary drive wheel among the drive wheels, to a secondary drive wheel among the drive wheels, the propeller shaft 10, and a power distribution device (not shown).

[0011] 1(b), the dashed dotted line roughly indicates an exhaust pipe 30, which is a heat source attached to, for example, an engine (not shown). The exhaust pipe 30 is disposed so as to pass near the propeller shaft 10, for example, above the vehicle at a predetermined distance from the propeller shaft 10, and extend in a direction intersecting the vehicle front-rear direction of the propeller shaft 10. High-temperature combustion gas output from the engine is discharged through the exhaust pipe 30.

[0012] As shown in FIG. 1(b), the connecting shaft 18 is provided so as to protrude from the transfer 16 toward the rear of the vehicle, and has a base end 18a formed in a tapered shape whose diameter dimension decreases as it extends from the transfer 16 toward the rear of the vehicle, and a cylindrical portion 18b continuous with the base end 18a.

[0013] The propeller shaft 10 is provided in the rear direction of the vehicle from the transfer 16 via a connecting shaft 18. A heat shield 22 formed to extend in the fore-and-aft direction of the vehicle is disposed radially outside the connecting shaft 18 and the propeller shaft 10. A heat shield structure 20 for the propeller shaft 10 includes the propeller shaft 10 and the heat shield 22.

[0014] The propeller shaft 10 includes a joint portion 10a connected to the tip end of the connecting shaft 18, and a main shaft 10b. The joint portion 10a is, for example, a universal joint that can transmit rotation regardless of the intersecting angle with the central axis C1 of the main shaft 10b. Fig. 1(b) shows a state in which the central axis C2 of the connecting shaft 18 and the central axis C1 of the main shaft 10b are concentric.

[0015] The heat shield 22 is formed so as to extend in the vehicle front-rear direction along the connecting shaft 18 and the propeller shaft 10, and is formed in a semi-cylindrical shape with a semicircular cross section and half of the circumferential direction being open. The heat shield 22 is formed, for example, by pressing a metal plate material, and is formed in a semi-cylindrical shape. The heat shield 22 is disposed concentrically with the central axis C2 of the connecting shaft 18. The heat shield 22 is disposed so as to extend in the vehicle front-rear direction from the transfer 16, and covers the outer periphery of the connecting shaft 18 and the joint portion 10a of the propeller shaft 10, specifically, the outer periphery of the upper half of the circumferential direction of the connecting shaft 18 and the joint portion 10a. The heat shield 22 includes a large diameter portion 22a with a constant diameter dimension provided at the front of the vehicle, a small diameter portion 22b with a constant diameter dimension smaller than the large diameter portion 22a provided at the rear of the vehicle, and a tapered inclined portion 22c provided between the large diameter portion 22a and the small diameter portion 22b, whose diameter dimension changes smoothly and continuously.

[0016] The heat shield 22 is attached integrally to the transfer 16 via, for example, a pair of mounting brackets 22d. The mounting brackets 22d are made of, for example, a metal plate, and are provided so as to protrude from the base end side of the heat shield 22 by pressing, welding, or the like. A fastening portion 22e of the mounting brackets 22d and the transfer 16 are fastened to each other by a mounting bolt 24.

[0017] The heat shield 22 is disposed radially between the exhaust pipe 30 and the joint portion 10a of the propeller shaft 10, as shown in FIG. 1B, for example. The heat shield 22 is a heat insulator for insulating the joint portion 10a from radiant heat from the exhaust pipe 30. The heat shield 22 is formed in a semi-cylindrical shape to block or reflect the radiant heat from the exhaust pipe 30, thereby suppressing a temperature rise in the joint portion 10a caused by the exhaust pipe 30, for example. Furthermore, for example, when the vehicle is traveling, the joint portion 10a of the propeller shaft is exposed to the outside air by the portion of the joint portion 10a that is not covered by the heat shield 22, i.e., the opening portion of the heat shield 22, and thus the joint portion 10a is cooled.

[0018] Incidentally, in the heat shield structure 20 for the propeller shaft 10 of the conventional example, the heat shield 22 longitudinally covers the connecting shaft 18 protruding from the transfer and the propeller shaft 10, and is disposed between them and the exhaust pipe 30 provided in the vicinity thereof, so that the fastening portion 22e of the heat shield 22, which is the base end, is fastened to the transfer 16, and the tip end side is attached in a cantilever shape as a free end. Therefore, the heat shield 22 becomes large in order to extend the shield from the fastening portion 22e to the joint portion 10a that requires heat shield protection, and further, because the heat shield 22 is supported by a cantilever structure, stress is concentrated at the fastening portion 22e, which makes the fastening portion 22e prone to cracking.

[0019] Fig. 2 is an enlarged view for explaining a main part of the heat shield structure 40 for the propeller shaft 10 to which the present invention is applied, and like Fig. 1 showing the conventional example, Fig. 2(a) is a perspective view and Fig. 2(b) is a side view. Note that parts common to the above-mentioned conventional example are given the same reference numerals and their explanations are omitted.

[0020] 2(b), the heat shield 42 is formed in a cylindrical shape with a diameter A so as to be disposed radially outside the columnar portion 18b of the connecting shaft 18 and the joint portion 10a of the propeller shaft 10 and extend in the front-rear direction of the vehicle 14. Furthermore, the heat shield 42 is formed so that a heat source side (hereinafter referred to as a shielding side) 42a of the cylindrical heat shield 42 facing the exhaust pipe 30 covers the joint portion 10a in the front-rear direction, and a side (hereinafter referred to as an opening side) 42b opposite to the shielding side 42a with respect to the central axis C2 of the connecting shaft 18 does not cover the joint portion 10a. That is, as shown in FIG. 2(b), the heat-shielding member 42 has a shape of a cylinder of diameter A with the rear end tilted perpendicular to the page, and the length (generator length) of the shielding side 42a along the central axis C2 of the connecting shaft 18 is longer than the length (generator length) of the opening side 42b along the central axis C2 of the connecting shaft 18.

[0021] The heat shield 42 is supported by a bearing 44 on the joint portion 10a side of the longitudinal center of the cylindrical portion 18b of the connecting shaft 18, i.e., the tip of the connecting shaft 18, so as to be relatively rotatable but immovable in the axial direction. The bearing 44 is press-fitted to the outer circumferential surface of the tip of the connecting shaft 18 and the inner circumferential surface of the heat shield 42 so as to be relatively immovable in the axial direction. Furthermore, the opening side 42b of the heat shield 22 on the side opposite to the shielding side 42a with respect to the central axis C2 of the connecting shaft 18 and the fixed portion 48 of the steering gearbox 46 arranged near the connecting shaft 18 are connected by an elastic member 50 by vulcanization adhesion, so that the heat shield 22 is fixed so as not to be relatively rotatable. The elastic member is preferably a cushioning material such as rubber. In this embodiment, the fixed portion 48 of the gearbox 46 is formed integrally with the gearbox 46, but a separate bracket for fixing may be prepared.

[0022] The heat shield 42 is supported in the radial and axial directions via the bearings 44 and is fixed non-rotatably via the elastic member 50, which, compared to the heat shield 22 of the conventional example, eliminates the need for a bracket to fasten to the transfer 16 and eliminates the need to extend from the transfer 16 to the joint portion 10a, including the length of the connecting shaft 18, thereby enabling a reduction in size. In addition to the improvement in strength that accompanies the reduction in size, there are also effects such as the elimination of the cantilever structure and the change in shape from a semi-cylinder to a cylinder, and the heat shield 42 achieves an improvement in strength, including the prevention of cracks.

[0023] In the heat-shielding structure 40 for the propeller shaft 10 of the present embodiment, the radiant heat of the exhaust pipe 30 is blocked or reflected by the shielding side 42a of the heat-shielding member 42, so that, for example, a temperature rise in the joint portion 10a of the propeller shaft 10 caused by the exhaust pipe 30 is suppressed. Furthermore, for example, when the vehicle is traveling, the joint portion 10a is exposed to the outside air by the portion of the joint portion 10a that is not covered by the heat-shielding member 42, i.e., the opening side of the heat-shielding member 42, and thus the joint portion 10a is cooled.

[0024] Thus, according to the heat shielding structure 40 of the propeller shaft 10 of this embodiment, the heat shielding member 42 is supported on the tip of the connecting shaft 18 via the bearing 44 so as to be relatively rotatable, and is fixed by the elastic member 50 between the fixing portion 48 of the steering gear box 46 located on the opposite side of the exhaust pipe (heat source) 30 with respect to the central axis C2 of the connecting shaft 18, eliminating a cantilever structure when fastening the heat shielding member 42 to the transfer 16, realizing a reduction in size of the heat shielding member 42 and an improvement in strength including prevention of crack generation. Furthermore, the length of the shielding side 42a of the heat shielding member 42 facing the exhaust pipe 30 along the central axis C2 of the connecting shaft 18 is longer than the length of the opening side 42b of the heat shielding member 42 along the central axis C2 of the connecting shaft 18, so that the joint portion 10a is covered by the shielding side 42a against the radiant heat of the exhaust pipe 30, while the opening side 42b is open and exposed to the outside air, thereby cooling the joint portion 10a. Thus, the conventional heat shielding and cooling functions are maintained.

[0025] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the present invention is not limited to this embodiment and may be embodied in other forms.

[0026] In this embodiment, the heat shield 22 and the fixed portion 48 of the steering gear box 46 are connected by the elastic member 50, but the connection destination does not necessarily have to be the steering gear box 46. Another unit or mechanism disposed in the vicinity of the heat shield 22 may be suitably used as the connection destination of the elastic member 50.

[0027] The above describes the embodiments of the present invention in detail with reference to the drawings. However, the above is merely one embodiment, and although other examples are not given, the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention. [Explanation of symbols]

[0028] 10: Propeller shaft (vehicle propeller shaft) 10a: Joint portion 10b: Main shaft 14: Vehicle 16: Transfer 18: Connecting shaft 40: Heat shielding structure of propeller shaft 10 42: Heat shielding member 42a: Shielding side 42b: Opening side 44: Bearing 46: Steering gear box 50: Elastic member

Claims

[Claim 1] A heat insulating structure for a vehicle propeller shaft, comprising: a propeller shaft extending in a front-rear direction and connected via a joint portion to a tip end of a connecting shaft protruding from a transfer case of a vehicle; and a cylindrical heat insulating member that shields the joint portion of the propeller shaft from radiation of a heat source, the cylindrical heat shield is supported via a bearing at a tip end of the connecting shaft so as to be relatively rotatable, and is connected via an elastic member to a steering gear box located on an opposite side of the central axis of the connecting shaft from the heat source; The length of the cylindrical heat shield member on the heat source side along the central axis of the connecting shaft is longer than the length of the cylindrical heat shield member on the heat source side along the central axis of the connecting shaft on the opposite side to the heat source with respect to the central axis of the connecting shaft. A heat insulating structure for a vehicle propeller shaft.

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