JP3354014B2 - Power transmission device for four-wheel drive vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device for a four-wheel drive vehicle, and more particularly to a four-wheel drive vehicle having a structure in which an output shaft for outputting the driving force of an engine is provided to the front wheel side and extending forward of the vehicle body. It relates to a power transmission device.

[0002]

2. Description of the Related Art A power transmission device for a four-wheel drive vehicle configured to output the driving force of an engine to both a front wheel side and a rear wheel side is disclosed in, for example, JP-A-63-83462. As shown, an output shaft (first output shaft) for outputting the driving force of the engine to the rear wheel side and an output shaft (second output shaft) for outputting the driving force of the engine to the front wheel side are arranged in parallel. There is known a structure in which a chain is wound around a sprocket mounted on each of output shafts, and these are housed in a transfer casing formed by mutually joining a front case and a rear case. Each of the output shafts is supported by a support portion of the casing. The first output shaft penetrates the casing and has a front end directly connected to the engine via a transmission, while a rear end has a rear wheel. The second output shaft extends through the front case and extends forward of the vehicle body where the front wheels are disposed. With such a configuration, the first output shaft receives driving force directly from the engine and outputs the driving force to the rear wheel side, and the driving force is transmitted to the second output shaft via the sprocket and the chain. Thus, the driving force of the engine is also output to the front wheels.

As described above, when a load is applied from the front of the vehicle when the second output shaft is provided so as to extend to the front of the vehicle body, the load reaches the second output shaft and presses it backward, As a result, the power transmission device receives the load from the output shaft, leans rearward or shifts in position, abuts against other equipment disposed behind, and damages the device, or causes the occupant to shock. Inconvenience such as feeling is caused.

Therefore, a technique has been conventionally known in which the second output shaft is configured so that the intermediate portion is bent by a load greater than a predetermined value. According to this, since the load applied to the second output shaft is absorbed and reduced by the bending of the output shaft,
The load applied to the power transmission device is reduced, thereby avoiding adverse effects and shock on the equipment behind.

[0005]

However, in the above technique, the structure of the second output shaft is complicated, and the floor of the vehicle body is installed high so that a space that does not obstruct the bending of the output shaft is obtained. As a result, there arises a problem that the vehicle height is increased.

An object of the present invention is to address the above-mentioned problem in a power transmission device of a four-wheel drive vehicle having a structure in which an output shaft for outputting a driving force of an engine is provided extending forward of the vehicle body. It is an object of the present invention to provide a power transmission device for a four-wheel drive vehicle that can effectively reduce the load applied from the front of the vehicle with a simple configuration.

[0007]

That is, a power transmission device for a four-wheel drive vehicle according to the present invention is characterized in that it is configured as follows to cope with the above problem.

First, an invention according to claim 1 of the present application (hereinafter, referred to as a "first invention") includes a first output shaft that extends rearward of a vehicle body and outputs a driving force of an engine to a rear wheel side; A second output shaft is disposed in parallel with the output shaft, extends forward of the vehicle body and outputs the driving force of the engine to the front wheels, and a supporting portion that houses the two output shafts and supports the second output shaft is provided. A power transmission device for a four-wheel drive vehicle, comprising: a casing having a casing having a predetermined output value, wherein a periphery of a second output shaft supporting portion of the casing is broken by a load rearward from the second output shaft by a predetermined value or more. And a reinforcing portion for reinforcing the casing is provided between the low-strength portion and the installation portion of the first output shaft in the casing. It is characterized by the following.

On the other hand, the invention according to claim 2 of the present application (hereinafter referred to as "the second invention") is characterized in that, in the first invention, the casing comprises a front case and a rear case joined to the case. Comprises a first protruding portion provided on the front case and protruding rearward, and a second protruding portion provided on the rear case protruding forward and in contact with the first protruding portion. .

The invention according to claim 3 of the present application (hereinafter referred to as "third invention") is characterized in that, in the second invention, the first projection and the second projection are continuous when the front case and the rear case are joined. Holes formed in the case, the holes in one of the protrusions penetrate the inner and outer surfaces of the case, and the first protrusion or the second protrusion At least one of the protruding portions is provided with a side hole communicating the hole in the protruding portion and the internal space of the casing formed when the front case and the rear case are joined.

Further, the invention according to claim 4 of the present application (hereinafter referred to as "fourth invention") is characterized in that in any one of the second invention and the third invention, the outer periphery of the low-strength portion is a cylindrical portion. A part of the outer peripheral surface of the cylindrical portion is formed in a flat shape.

[0012]

According to the present invention, the following effects can be obtained according to the present invention.

According to the first aspect of the invention, the casing is provided with a support portion that extends to the front of the vehicle body and supports the second output shaft for outputting the driving force of the engine to the front wheels. Since the periphery of the portion is a low-strength portion whose strength is relatively reduced so as to be broken by a load of a predetermined value or more rearward from the second output shaft, the second output shaft is provided from the front of the vehicle. When the output shaft is pressed rearward due to a load equal to or more than a predetermined value, the low-strength portion around the support portion supporting the output shaft receives the load and breaks. As a result, the second output shaft or the support portion is separated from the power transmission device, so that a load equal to or greater than a predetermined value is not applied to the power transmission device, and the second output shaft or the support portion comes into contact with equipment disposed behind. Adverse effects and shocks are avoided.

Further, since a reinforcing portion for reinforcing the casing is provided between the low-strength portion of the casing and the installation portion of the first output shaft, the rear portion of the power transmission device when receiving a load is provided. And the low strength portion is effectively broken due to the difference in strength between the reinforcing portion and the low strength portion. As a result, only the second output shaft or the support portion is surely detached, and there is no inconvenience that a wide range of members detach and come into contact with equipment disposed behind.

On the other hand, according to the second invention, the casing is formed by joining a front case and a rear case, and the reinforcing portions are provided on both cases, one protruding rearward and the other protruding forward. Since the first and second projecting portions are in contact with each other, the front case and the rear case have a continuous structure bridged by both projecting portions, whereby the casing is reinforced. .

According to the third aspect of the present invention, holes are formed in the first protrusion and the second protrusion, respectively, and these two holes are continuously used for bolt fitting when the front case and the rear case are joined. A bolt is formed and fitted into the hole, so that the protrusions are fastened after being brought into contact with each other as described above, so that the reinforcement of the casing is further strengthened.

The hole formed in one of the protrusions penetrates the inner and outer surfaces of the case, and communicates the internal space of the casing formed when the front case and the rear case are joined to the hole for bolt fitting. Since the side hole is provided in at least one of the first protrusion and the second protrusion, the outside of the casing and the internal space are communicated with each other through the bolt fitting hole and the side hole. As a result, after joining the two cases, lubricating oil is injected from the outside of the casing into the inside of the casing through the communication hole,
After that, the communication hole can be closed by fitting a bolt, so that the protrusion provided as a reinforcing portion can be used for lubricating oil injection, and it is necessary to separately provide a new lubricating oil injection port. Disappears.

In the above-mentioned publication, it is disclosed that at least one of the front surface and the rear case is provided with a rib protruding from the opposing surface and the ends thereof are abutted. This is provided for the purpose of preventing noise due to vibration by increasing the height, and is based on a technical idea different from the technical idea of the present invention.

Further, according to the fourth aspect, the outer periphery of the low-strength portion is a tubular portion, and a part of the outer peripheral surface of the tubular portion is formed in a flat shape. A part is linearly distributed around the support portion of the two output shafts. Therefore, since a corner is formed at the boundary between the linear portion and the other portion, the load applied from the second output shaft concentrates on the corner without being evenly distributed to the low-strength portion. As a result, rupture is likely to occur from this point as a starting point, and rupture of the low-strength portion is assured.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a power transmission device 1 for a four-wheel drive vehicle in this embodiment includes a clutch mechanism 2 and a transmission mechanism 3 for a manual vehicle, or a torque converter 2 and a transmission mechanism 3 for an AT vehicle. A first output shaft 5 connected to a rear portion of the transmission 4 and extending rearward of the vehicle body provided in the transmission 4 penetrates a casing 6 of the power transmission device 1 from a front surface to a rear surface, and has a rear end portion. Is connected to a rear wheel driving thrust shaft 7 so that a driving force of an engine (not shown) is output to the rear wheel side. The power transmission device 1 includes the first output shaft 5.
And a second output shaft 8 extending in front of the casing 6 from the front surface of the casing 6, and a sliding yoke 9 connected to a front-wheel drive thrust shaft (not shown) is provided at a front end of the second output shaft 8. I have.

The casing 6, as shown in an enlarged manner in FIG. 2, is a front case 1 in which a housing space for housing various power transmitting members is formed by being joined to each other at joint surfaces.
0 and the rear case 11. The transmission 4
And a front case 10 forming a front surface of the casing 6 is formed into a shape slightly bulging forward from the joint surface, and a through-hole of the first output shaft 5 is provided at an upper portion thereof and a lower portion thereof is provided at a lower portion thereof. Is formed with a cylindrical portion 12 further projecting toward the front of the vehicle body, and a through hole for the second output shaft 8 is provided on the front surface of the cylindrical portion 12. This cylindrical portion 12
Has a substantially cylindrical shape, but its upper surface is formed in a D-shaped cross section which is a plane extending in the horizontal direction (see FIG. 5). On the other hand, the rear case 11 forming the rear surface of the casing 6 is
It is formed into a shape slightly bulging backward from the joint surface, and a through-hole of the first output shaft 5 is provided on the upper part thereof,
The lower portion is not formed with the above-described tubular portion, and is formed as a vertical wall surface extending in the vertical direction. The first output shaft 5 is provided at the upper part of the casing 6 via bearings 13 and 14 held by the two cases 10 and 11, respectively, and the second output shaft 8 is provided at the lower part of the casing 6 by the front case 10.
Are rotatably supported via bearings 15 and 16 held on the vertical wall surface of the cylindrical portion 12 and the rear case 11, respectively.

A driving sprocket 17 is spline-coupled to the first output shaft 5 of the two output shafts 5, 8,
A driven sprocket 18 is rotatably provided on the second output shaft 8 with respect to the output shaft 8, and a chain 19 is wound around the sprockets 17, 18. A power distribution means 20 for transmitting the driving force of the driven sprocket 18 to the second output shaft 8 is provided in a portion covered by the cylindrical portion 12.

The power distribution means 20 includes an outer cylinder 21 spline-coupled to the boss of the driven sprocket 18,
Inner cylinder 22 spline-coupled to the outer periphery of second output shaft 8
And a viscous coupling having a plurality of outer plates and inner plates protruding from the outer cylinder 21 and the inner cylinder 22 so as to face each other. The driven sprocket 18 and the outer cylinder 21 include: The driving force corresponding to the rotation difference generated between the second output shaft 8 and the inner cylinder 22 is changed to a second driving force.
The power is transmitted to the output shaft 8.

That is, when the driving force of the first output shaft 5 is transmitted to the driven sprocket 18 via the chain 19 and the outer cylinder 21 is driven to rotate, the gap between the outer cylinder 21 and the inner cylinder 22 is increased. The rotational force of the outer plate protruding from the outer cylinder 21 is transmitted to the inner plate protruding from the inner cylinder 22 due to the viscosity of the silicone oil sealed in the inner cylinder 22. As a result, the inner cylinder 22 and the second output shaft 8 is driven to rotate, and the driving force of the engine is output to the front wheels through the sliding yoke 9. The larger the rotation difference between the output side composed of the driven sprocket 18 and the input side composed of the second output shaft 8, the larger the driving force is transmitted.

The second output shaft 8 is formed as a hollow shaft, and at the rear end thereof, an opening 23 serving as a passage for lubricating oil, which will be described later, is formed, and the opening 23 and the driven sprocket 18 are supported. A first communication hole 24 that communicates with the portion is provided in the shaft wall. Also, in the front part of the opening 23,
A cap 25 that prevents the lubricating oil from flowing to the installation portion of the sliding yoke 9 is attached.

On the other hand, a holding portion 26 of a bearing 13 for supporting a front portion of the first output shaft 5 is provided on an upper inner wall surface of the front case 10 and an inner wall surface of the cylindrical portion 12 formed on a lower portion. Bearing 1 for supporting the front part of the second output shaft 8
5, a holding portion 27 of the bearing 14 for supporting the rear portion of the first output shaft 5 is provided on the upper inner wall surface of the rear case 11, and a second output member is provided on the lower inner wall surface. Bearing 16 for supporting the rear end of shaft 8
Are formed respectively. Of the four bearing holding portions 26, 27, 28, 29, the thickness of the vertical wall surface located around the holding portions 28, 29 of the bearings 15, 16 supporting the front and rear of the second output shaft 8, respectively, is 10 and the rear case 11 are formed as small strength portions 30 and 31 whose surface strength is set lower than the surface strength of other portions.

Here, the low-strength portion 31 of the rear case 11 includes the bearing holding portion 29 and the bearing 16.
Or, while being distributed in a substantially ring shape between the reinforcing ribs 32 formed in a substantially ring shape along the shape of the holding portion 29, the low strength portion 30 in the front case 10 is
It is formed between the bearing holding portion 28 and the rim portion 33 of the tubular portion 12, and its outer periphery is continuous with the rim portion 33. As a result, the outer peripheral shape is the same as the cross-sectional shape of the tubular portion 12. They are distributed in the same D-shape (see FIG. 5).

Also, as shown in FIG.
On the inner wall surface, a first guide groove 34 and a second guide groove 35 for lubricating oil which are scraped up by the chain 19 are formed beside the bearing holding portion 27 for supporting the first output shaft 5. That is, a first rib 36 having a predetermined height extending from the side surface of the upper bearing holding portion 27 toward the upper surface of the lower bearing holding portion 29, and the rear case 11 while maintaining a predetermined distance from the first rib 36. A first guide groove 34 is formed by a second rib 37 having a predetermined height extending from a side surface portion of the bearing member 29 toward the upper surface portion of the bearing holding portion 29, and the second rib 37 and the second rib 37 are formed. A second guide groove 35 is formed by the third rib 38 provided diagonally below the second guide groove 35.

Here, the installation interval between the first rib 36 and the second rib 37 is set so as to become smaller toward the lower bearing holding portion 29, whereby the first guide groove 34 is provided.
The flow rate of the lubricating oil introduced into the groove increases as the groove width decreases. A groove 39 extending toward the center of the bearing holding portion 29 is formed at a lower portion of the first guide groove 34, and a semi-circular projecting piece that covers a lower end of the groove 39. Reference numeral 40 protrudes toward the opening 23 of the second output shaft 8. On the other hand, the second rib 37
A notch is provided at a lower portion of the first guide groove 34 to form a communication passage 41 between the first guide groove 34 and the second guide groove 35, so that the lubricating oil flowing into the second guide groove 35 passes through the communication passage 41 through the communication passage 41. It is introduced into the concave groove 39. Then, these first guide grooves 34,
The lubricating oil in the casing 6 is supplied to the rotation sliding portion of the driven sprocket 18 by the second guide groove 35, the concave groove 39, the projecting piece 40, the opening 23 of the second output shaft 8, and the first communication hole 24. A supply path is forcibly supplied.

In the configuration described above, when the first output shaft 5 of the transmission 4 is rotationally driven by the rotation of the engine while the vehicle is running, the driving force is transmitted to the rear wheels via the rear wheel driving thrust shaft 7. At the same time, a part of the driving force is transmitted to the power distribution means 20 including the viscous coupling via the driving sprocket 17, the chain 19 and the driven sprocket 18. And the power distribution means 20
The driving force corresponding to the load acting on the front wheels is transmitted to the second output shaft 8 by the power distribution action of the above, and the transmitted driving force is transmitted from the second output shaft 8 via the sliding yoke 9 and the front wheel driving thrust shaft. Output to the front wheels.

At this time, the lubricating oil in the casing 6 raked up by driving the chain 19 flows into the upper openings of the first guide groove 34 and the second guide groove 35, and the guide groove 34 , 35 to the concave groove 39 and guided to the center of the lower bearing holding portion 29. Then, the lubricating oil is guided into the opening 23 of the second output shaft 8 by the flow of the lubricating oil being converted by the protruding piece 40 in the axial direction of the second output shaft 8. The power is supplied to the rotary sliding portion of the driven sprocket 18 through the first communication hole 24 provided in the wall. Therefore, the rotational sliding portion of the driven sprocket 18 is always lubricated during running of the vehicle.

In addition to the above configuration, the inner wall surfaces of the front case 10 and the rear case 11 of the power transmission device 1 according to this embodiment are provided substantially toward the storage space surrounded by the cases 10 and 11, respectively. Projecting part 4 that projects
2, 43 are formed. As shown in FIGS. 2 and 3 in an enlarged manner, each of the protrusions 42 and 43 is formed in a substantially symmetrical shape, and has protrusion ribs 42 a and 43 a extending in the vertical direction of the front case 10 and the rear case 11. ,
The bosses 42b, 43b bulged in a substantially circular shape in the middle of the ribs 42a, 43a.
a, 43a are the upper ends of the low-strength portions 30, 31;
In other words, it is set at substantially the same height position as the upper part of the rim part 33 of the tubular part 12 and the upper part of the reinforcing rib 32, and
When the front case 10 and the rear case 11 are joined to each other on the joint surface to form the casing 6, the projecting portions 42 and 43 are provided with the ribs 42 a and 43 a and the ribs 42 a and 43 a so that the tips thereof are in contact with each other. The dimensions of the bosses 42b and 43b are set. Therefore, when the casing 6 is configured, in other words, when the front case 10 and the rear case 11 are joined, as shown in FIG. 2, the two projecting portions 42, 43 are continuous and the two cases 10, 11 are internally bridged. As a result, the vehicle is reinforced against a load acting in the vehicle longitudinal direction.

Further, the boss 42 on the front case 10 side
A screw hole 44 that does not reach the front surface of the case 10 is provided at the center of the case b, and a through hole 45 that reaches the rear surface of the case 11 is provided at the center of the boss 43b on the rear case 11 side. When the casing 6 is formed, the screw hole 44 and the through hole 45 are continuous to form one screw hole for bolt fitting. The projections 42 and 43 are fastened by bolts 46 screwed into the screw holes for bolt fitting. As a result, the internal bridge structure is further strengthened. Also, the boss 43b on the rear case 11 side
A second communication hole 47 is provided at a predetermined position on the peripheral wall of the casing 6 for communicating the outer peripheral surface thereof with the through hole 45 formed therein. Or through a screw hole for bolt fitting and a second communication hole 47. That is, the front case 10 and the rear case 11 are joined to each other to
After assembling, by supplying the lubricating oil from the rear opening of the through hole 45 before the bolt fitting, the lubricating oil can be injected into the storage space in the casing 6 through the second communication hole 47, The conventional installation of the lubricating oil inlet 48 as shown in FIG. 3 can be omitted. The through hole 45 and the second communication hole 47 are provided with bolts 4 to be screwed after lubricating oil is injected.
6, the lubricating oil in the casing 6 does not leak to the outside.

As described above, the low strength parts 30, 31 having lower surface strength than other parts are provided around the bearing holding parts 28, 29 for supporting the front and rear of the second output shaft 8, respectively. The low-strength portion 3 above the low-strength portions 30 and 31
By forming the protruding portions 42 and 43 for bridging the front case 10 and the rear case 11 inside at positions close to 0 and 31, the following effects can be obtained.

That is, when a load is applied from the front of the vehicle, and as a result, a load is applied to the second output shaft 8 via the front wheel driving thrust shaft and the sliding yoke 9 to push the output shaft 8 rearward, The bearing 16 is pressed rearward by the flange portion 49 formed on the second output shaft 8, and the holding portion 29 is pressed rearward by the bearing 16, so that the power transmission device 1 is connected to the transmission 4. It leans or bends to the rear of the vehicle body with the vicinity of the connection portion as a fulcrum, and comes into contact with equipment disposed behind and damages the equipment. Further, the power transmission device 1 is disengaged from the connection portion with the transmission 4 and moves rearward, or a central portion of the casing 6 is broken and a wide range of members is detached rearward,
Similarly, there will be adverse effects on the equipment behind.

However, in the power transmission device 1 for a four-wheel drive vehicle according to this embodiment, the surface strength around the bearing holding portion 29 which receives the rearward load applied from the second output shaft 8 is higher than that of other portions. As shown in FIG. 4, when the bearing holding portion 29 is pressed backward, the low-strength portion 31 is broken, and as a result, the bearing holding portion 31 is broken. 29
Is removed from the power transmission device 1 and the load applied to the power transmission device 1 is absorbed. Therefore,
The rearward inclination or bending of the power transmission device 1 or the rearward movement thereof is avoided, and there is no risk of damaging the equipment behind.

Further, at this time, since the member that is detached from the power transmission device 1 is the member disposed at the lowermost portion of the device 1, there are few devices installed behind the lowermost portion, and
Also, since only a limited range of members around the bearing holding portion 29 are detached, members over a wide area do not detach and move rearward. As a result, the bearing holding portion 29 etc. detaches and moves backward. Even so, the risk of damaging other equipment and the like is reduced.

On the other hand, the low strength portion 3 is also provided on the front case 10.
0, the bearing 1 on the front case 10 side by a load pressing the second output shaft 8 rearward.
When the bearing 5 and the bearing holding portion 28 are pulled backward, the low-strength portion 30 is broken, and as a result,
The rearward movement of the second output shaft 8 is performed smoothly, and the load applied to the power transmission device 1 is reliably absorbed and reduced.

Further, a rim portion 33 and a reinforcing rib 32 of the tubular portion 12 are provided around the low strength portions 30 and 31, respectively, and a bolt is provided above the rim portion 33 and the reinforcing rib 32. Since the protruding portions 42 and 43 forming the internal bridge structure strengthened by the fastening of 46 intervene to form the reinforcing portion, the power transmission device 1 is prevented from tilting or bending backward when receiving a load. In addition, the low-strength portions 30, 31 are effectively broken by the difference in surface strength between the reinforcing portion and the low-strength portions 30, 31. This ensures that only members within a limited range around the bearing holding portions 28 and 29 are detached.

As shown in FIG. 5, the outer periphery of the low-strength portion 30 of the front case 10 is continuous with the rim portion 33 of the cylindrical portion 12 having a D-shaped cross section. Are distributed in a ring shape, so that two corners 30a, 30a are formed at the intersections.
As a result, the load applied to the low-strength portion 30 is concentrated on the corner 30a without being evenly dispersed, and the low-strength portion 30 is easily broken starting from the corner 30a. The breakage of the low-strength portion 30 is ensured.

When the distribution of the low-strength portions 30 is D-shaped as described above, the number of generated corner portions is reduced, and as a result, the concentration of the load is increased, which is preferable. Also,
A low-strength portion having such a corner may be provided on the rear case 11 side.

[0043]

As described above, according to the present invention, there is provided a power transmission device for a four-wheel drive vehicle having a structure in which an output shaft for outputting a driving force of an engine is provided extending forward of a vehicle body.
A low-strength portion whose strength is relatively reduced so that the periphery of the support portion supporting the output shaft in the casing of the power transmission device is broken by a load of a predetermined value or more rearward from the output shaft. Therefore, when a load equal to or more than a predetermined value is applied to the output shaft from the front of the vehicle and is pressed rearward, the low-strength portion is broken by the load. As a result, the output shaft or the supporting portion is detached from the power transmission device and the load is absorbed, so that the power transmission device leans rearward or the like and comes into contact with other equipment and devices arranged behind, Inconveniences such as damaging this can be avoided.

Further, since a reinforcing portion for reinforcing the casing is provided between the low-strength portion of the casing and the installation portion of the other output shaft, the casing is provided rearward of the power transmission device when receiving a load. Of the low-strength portion is effectively prevented by the difference in strength between the reinforcing portion and the low-strength portion. As a result, only the minimum portion around the output shaft or the support portion is reliably detached, and there is no adverse effect such that a wide range of members detach and come into contact with the equipment disposed behind. .

On the other hand, when the front case and the rear case which are joined to each other are provided with protrusions so that the two protrusions are brought into contact with each other, the front case and the rear case are connected to each other by a continuous bridge structure. And the casing formed by joining the two cases is reinforced against a load from the front of the vehicle. Further, when the two protrusions are fastened by bolts, the reinforcement of the casing can be further strengthened, and a side hole communicating the internal space of the casing and the bolt fitting hole is formed in the protrusion. In addition, the protrusion provided as the reinforcing portion can be used for lubricating oil injection, and there is no need to separately provide a lubricating oil injection port.

Further, when the outer periphery of the low-strength portion is a cylindrical portion and a part of the outer peripheral surface of the cylindrical portion is formed in a flat shape, a corner portion is formed in the distribution of the low-strength portion. As a result, the load acting on the low-strength portion is not uniformly distributed but concentrated on the corner portion, so that the low-strength portion easily breaks from this point as a starting point, and the breakage is ensured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a power transmission device for a four-wheel drive vehicle according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the power transmission device.

FIG. 3 is a schematic front view of a rear case used in the power transmission device.

FIG. 4 is an explanatory diagram showing an effect of the power transmission device.

FIG. 5 is a schematic front view of a lower part of a front case used in the power transmission device.

[Explanation of symbols]

 8 Second output shaft 10 Front case 11 Rear case 12 Cylindrical part 15, 16 Bearing 28, 29 Bearing holding part 30, 31, Low strength part 30a Square part 42, 43 Projecting part

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ishimura grammar 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-7-246850 (JP, A) JP-A-63 JP-A-120962 (JP, A) JP-A-63-83462 (JP, A) JP-A-4-175559 (JP, A) JP-A-6-22652 (JP, U) JP-A-61-185618 (JP, U) (62) 163658 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60K 17/344 F16H 57/02-57/04 F16D 9/00

Claims (4)

(57) [Claims] 1. A first output shaft extending rearward of a vehicle body and outputting an engine driving force to a rear wheel side, and disposed in parallel with the first output shaft, extending forward of the vehicle body and driving an engine driving force to a front wheel side. A power transmission device for a four-wheel drive vehicle, comprising: a second output shaft that outputs the output shaft; and a casing that houses the two output shafts and is provided with a support portion that supports the second output shaft. And a casing having a relatively low strength so that the periphery of the second output shaft support portion is broken by a load of a predetermined value or more rearward from the second output shaft. A power transmission device for a four-wheel drive vehicle, wherein a reinforcing portion for reinforcing the casing is provided between the low strength portion and the installation portion of the first output shaft. 2. The casing comprises a front case and a rear case joined to the case. The reinforcing portion has a first protruding portion provided on the front case and protruding rearward, and a reinforcing member provided on the rear case and having a front portion. The power transmission device for a four-wheel drive vehicle according to claim 1, further comprising a second protruding portion protruding from the first protruding portion and being in contact with the first protruding portion. 3. The first projection and the second projection each have a continuous hole when the front case and the rear case are joined, and are fastened by bolts fitted into the holes. A hole in one of the protrusions penetrates the inner and outer surfaces of the case, and is formed in at least one of the first protrusion and the second protrusion when the hole in the protrusion and the front case and the rear case are joined. The power transmission device for a four-wheel drive vehicle according to claim 2, further comprising a side hole that communicates with an internal space of the casing to be formed. 4. The method according to claim 2, wherein an outer periphery of the low-strength portion is a tubular portion, and a part of an outer peripheral surface of the tubular portion is formed in a flat shape. 4. A power transmission device for a four-wheel drive vehicle according to claim 1.