JPH0825990A - Power transmission device for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To absorb and alleviate a load applied from a position forward of a body, upon the arrival of the load at an output shaft for transmitting the driving force of an engine, regarding the power transmission device of a four- wheel drive vehicle having a structure where the output shaft is extended forward along the body. CONSTITUTION:Bearing holding sections 28 and 29 are respectively provided beneath the front case 10 and the rear case 11 of a power transmission device 1, and the second output shaft 8 to transmit a driving force to front wheels is supported on bearings 15 and 16 held on the sections 28 and 29, so as to be freely rotatable. In addition, a wall surrounding both of the sections 28 and 29 is formed as low strength sections 30 and 31 having smaller thickness than other sections. Also, projections 42 and 43 for connecting and bridging the two cases 10 and 11 are provided immediately above the sections 30 and 31 for strengthening the cases 10 and 11. Thus, constitution is so made that the sections 30 and 31 are broken, when a load from a position forward of a body pushes back the holding sections 28 and 29 via the second output shaft 8.

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 a driving force of an engine is provided on a front wheel side so as to extend forward of a vehicle body. The present invention 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 front and rear wheels is disclosed in, for example, Japanese Patent Laid-Open No. 63-83462. As described above, the output shaft (first output shaft) that outputs the driving force of the engine to the rear wheel side and the output shaft (second output shaft) that outputs the driving force of the engine to the front wheel side are arranged in parallel. A structure is known in which a chain is wound around a sprocket mounted on each of the output shafts and then housed in a transfer casing formed by joining a front case and a rear case to each other. Each output shaft is supported by the supporting portion of the casing, of which the first output shaft penetrates the casing and the front end portion is directly connected to the engine through the transmission, while the rear end portion is the rear wheel. And a second output shaft that extends through the front case and extends toward the front of the vehicle body where the front wheels are disposed. With such a configuration, the first output shaft receives the 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. The driving force of the engine is also output to the front wheels.

Thus, when a load is applied from the front of the vehicle when the second output shaft is provided so as to extend toward the front of the vehicle body, the load reaches the second output shaft and pushes it backward. As a result, the power transmission device receives the load from the output shaft and tilts rearward or shifts its position to come into contact with other equipment and devices arranged behind, which may damage the equipment or shock the occupant. It causes inconvenience such as feeling.

Therefore, there has been conventionally known a technique for constructing the second output shaft so that the intermediate portion is bent by a load of a predetermined value or more. According to this, since the load applied to the second output shaft is absorbed and relieved by the bending of the output shaft,
The load applied to the power transmission device is reduced, and adverse effects on the equipment behind and shocks are avoided.

[0005]

However, in the above technique, the structure of the second output shaft becomes complicated, and the floor of the vehicle body is installed high so as to obtain a space that does not hinder the bending of the output shaft. Therefore, there is a problem that the vehicle height becomes high.

An object of the present invention is to solve the above problems in 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 so as to extend forward of a vehicle body. An object of the present invention is 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, the power transmission device for a four-wheel drive vehicle according to the present invention is characterized in that it is configured as follows in order to address the above problems.

First, the invention according to claim 1 of the present application (hereinafter referred to as "first invention") is a first output shaft that extends rearward of a vehicle body and outputs a driving force of an engine to a rear wheel side, and the first output shaft. A second output shaft that is arranged in parallel with the output shaft and extends toward the front of the vehicle body and outputs the driving force of the engine to the front wheel side, and a support portion that accommodates these two output shafts and that supports the second output shaft are provided. A power transmission device for a four-wheel drive vehicle having a casing, wherein a periphery of the second output shaft support portion in the casing is broken by a load from the second output shaft rearward by a predetermined value or more. Is a low-strength portion whose strength is relatively low, and 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. It is characterized by

On the other hand, the invention according to claim 2 of the present application (hereinafter referred to as the "second invention") is the same as the first invention, except that the casing comprises a front case and a rear case joined to the case, and the reinforcing portion is provided. Comprises a rearwardly projecting first projecting portion provided on the front case, and a second projecting portion provided on the rear case and projecting forward and facing the first projecting portion. .

The invention according to claim 3 of the present application (hereinafter referred to as the "third invention") is the same as the second invention, except that the first protrusion and the second protrusion are continuous when the front case and the rear case are joined together. And a bolt fitted into the hole, the hole in one of the projecting portions penetrates through the inner and outer surfaces of the case, and the first projecting portion or the second projecting portion. At least one of the protrusions is provided with a side hole that connects the hole in the protrusion and the internal space of the casing formed when the front case and the rear case are joined together.

Further, the invention according to claim 4 of the present application (hereinafter referred to as "the fourth invention") is the same as the second invention or the third invention, wherein the outer periphery of the low-strength portion is a tubular portion. A part of the outer peripheral surface of the tubular portion is formed in a flat shape.

[0012]

According to the present invention having the above-mentioned structure, the following effects can be obtained.

First, according to the first aspect of the invention, the casing is provided with a support portion that extends toward the front of the vehicle body and supports the second output shaft that outputs the driving force of the engine to the front wheel side. Since the periphery of the portion is a low-strength portion having a relatively low strength so as to be broken by a load of a predetermined value or more rearward from the second output shaft, the second output shaft from the front of the vehicle When a load equal to or more than a predetermined value is applied to the output shaft and the output shaft is pushed backward, 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 supporting portion is separated from the power transmission device, so that a load of a predetermined value or more is not applied to the power transmission device, and the second output shaft or the support portion comes into contact with the equipment arranged behind the power transmission device. Adverse effects and shocks are avoided.

Further, since the reinforcing portion which reinforces 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. Inclination and bending of the low-strength portion are effectively prevented, 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 reliably disengaged, and there is no inconvenience that a wide range of members disengage and come into contact with the equipment arranged behind.

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

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

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

It should be noted that the aforementioned publication discloses that ribs are provided so as to project on at least one of the facing surfaces of the front case and the rear case, and the tips thereof are butted against each other. It is provided for the purpose of heightening and preventing noise due to vibration, and is based on a technical idea different from the technical idea of the present invention.

Further, according to the fourth aspect of the invention, since 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, the low-strength portion is the first portion. A part of the two output shafts is distributed in a straight line around the supporting portion. Therefore, since a corner is formed at the boundary between this linear portion and another 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, breakage easily occurs from this point, and the breakage of the low-strength portion is ensured.

[0020]

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

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

As shown in the enlarged view of FIG. 2, the casing 6 is joined to each other at the joining surface to form a storage space for storing various power transmission members therein.
It consists of 0 and a rear case 11. Of these, the transmission 4
The front case 10 which is connected to the casing 6 and constitutes the front surface of the casing 6 is formed in a shape which is slightly bulged forward from the joining surface, and a through hole for the first output shaft 5 is provided in the upper portion thereof and the lower portion thereof is provided. A tubular portion 12 that further projects toward the front of the vehicle body is formed on the front surface of the vehicle, and a through hole for the second output shaft 8 is provided on the front surface of the tubular portion 12. This tubular portion 12
Has a substantially cylindrical shape, but its upper surface is formed in a D-shaped cross section as 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 in a shape that slightly bulges rearward from the joint surface, and a through hole for the first output shaft 5 is provided in the upper portion thereof,
The lower part thereof is a vertical wall surface that does not have the cylindrical portion as described above and extends in the vertical direction. The first output shaft 5 is located above the casing 6 via bearings 13 and 14 held in the cases 10 and 11, respectively, and the second output shaft 8 is located below the casing 6 in the front case 10.
The cylindrical portion 12 and the rear case 11 are rotatably supported by bearings 15 and 16 held on the vertical wall surfaces of the rear portion 11 and the rear portion 11, respectively.

Of these two output shafts 5, 8, a drive side sprocket 17 is splined to the first output shaft 5,
A driven side 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 both 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 the portion covered by the tubular portion 12.

The power distribution means 20 includes an outer cylinder 21 splined to the boss portion of the driven sprocket 18,
Inner cylinder 22 splined to the outer periphery of the second output shaft 8
And a driven-side sprocket 18 and an outer cylinder 21, the outer cylinder 21 and the inner cylinder 22, and a viscous coupling having a plurality of outer plates and inner plates that are provided so as to face each other on the peripheral surfaces of the outer cylinder 21 and the inner cylinder 22, respectively. The driving force corresponding to the rotation difference generated between the second output shaft 8 and the inner cylinder 22 is
It is adapted to be transmitted to the output shaft 8.

That is, when the outer cylinder 21 is rotationally driven by transmitting the driving force of the first output shaft 5 to the driven sprocket 18 via the chain 19, the outer cylinder 21 and the inner cylinder 22 are separated from each other. Due to the viscosity of the silicone oil enclosed in the inner cylinder 22, 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, and as a result, the inner cylinder 22 and the second output shaft 8 is rotationally driven, and the driving force of the engine is output to the front wheel side via the sliding yoke 9. The larger the rotational 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 a hollow shaft, and an opening 23 serving as a passage for lubricating oil, which will be described later, is formed at the rear end of the second output shaft 8, and the opening 23 and the driven sprocket 18 are supported. A first communication hole 24 that communicates with the section is provided in the shaft wall. Further, in the front part of the opening 23,
A cap 25 is attached to prevent the lubricating oil from flowing out to the installation portion of the sliding yoke 9.

On the other hand, a holding portion 26 of the bearing 13 for supporting the front portion of the first output shaft 5 is provided on the inner wall surface of the upper portion of the front case 10, and an inner wall surface of the cylindrical portion 12 formed at the lower portion is provided on the inner wall surface thereof. Bearing 1 for supporting the front part of the second output shaft 8
5, the holding portions 28 of the bearings 14 for supporting the rear portion of the first output shaft 5 are formed on the upper inner wall surface of the rear case 11, and the second output portion is formed on the lower inner wall surface. Bearing 16 for supporting the rear end of the shaft 8
The holding portions 29 are formed respectively. Of these four bearing holders 26, 27, 28, 29, the thickness of the vertical wall surface located around the holders 28, 29 of the bearings 15, 16 supporting the front and rear of the second output shaft 8 has a thickness of the front case, respectively. 10 and the rear case 11 are formed to be small, and the surface strength thereof is set to be low strength portions 30 and 31 set to be 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.
In addition, the low-strength portion 30 of the front case 10 is distributed in a substantially ring shape with the reinforcing rib 32 formed in a substantially ring shape along the shape of the holding portion 29.
It is formed between the bearing holding portion 28 and the rim portion 33 of the tubular portion 12, and the outer periphery thereof is continuous with the rim portion 33, and as a result, the outer peripheral shape is the cross-sectional shape of the tubular portion 12. They are distributed in the same D shape (see FIG. 5).

Further, as shown in FIG. 3, the rear case 11
A first guide groove 34 and a second guide groove 35 of the lubricating oil scraped up by the chain 19 are formed on the inner wall surface of the bearing holding portion 27 for supporting the first output shaft 5. That is, the first rib 36 having a predetermined height extending from the side surface portion of the upper bearing holding portion 27 toward the upper surface portion of the lower bearing holding portion 29, and the rear case 11 while maintaining a predetermined distance from the first rib 36. The first guide groove 34 is formed by the second rib 37 having a predetermined height extending from the side surface of the bearing holding portion 29 toward the upper surface of the bearing holding portion 29, and the second rib 37 and the second rib 37 are formed. The second guide groove 35 is formed by the third rib 38 provided obliquely below.

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 formed.
The flow velocity of the lubricating oil introduced into the cylinder is increased as the groove width decreases. In addition, a concave groove 39 extending toward the center of the bearing holding portion 29 is formed in the lower portion of the first guide groove 34, and a semi-arcuate projecting piece that covers the lower end portion of the concave groove 39 is formed. 40 is provided to project toward the opening 23 of the second output shaft 8. On the other hand, the second rib 37
A notch is provided in the lower part of the groove to form a communication passage 41 between the first guide groove 34 and the second guide groove 35, whereby the lubricating oil that has flowed into the second guide groove 35 passes through the communication passage 41. It is introduced into the groove 39. Then, these first guide grooves 34,
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, the lubricating oil in the casing 6 is transferred to the rotary sliding portion of the driven sprocket 18. A supply route forcibly supplied is configured.

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, its driving force is transmitted to the rear wheel side via the rear wheel drive thrust shaft 7. At the same time as being output, a part of the driving force is transmitted to the power distribution means 20 composed of the above-mentioned viscous coupling through the driving side sprocket 17, the chain 19 and the driven side sprocket 18. Then, 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 through the sliding yoke 9 and the front wheel driving thrust shaft. Will be output to the front wheels.

At this time, the lubricating oil in the casing 6 scraped up by driving the chain 19 flows into the upper openings of the first guide groove 34 and the second guide groove 35, and these guide grooves 34 , 35, down to the groove 39 and guided to the center of the lower bearing holding portion 29. Then, the flow of the lubricating oil is converted into the axial direction of the second output shaft 8 by the protrusion 40, so that the lubricating oil is guided into the opening 23 of the second output shaft 8, and the shaft of the output shaft 8 is further guided. It is supplied to the rotary sliding portion of the driven side sprocket 18 via the first communication hole 24 provided in the wall. Therefore, the rotary sliding portion of the driven sprocket 18 is constantly lubricated while the vehicle is traveling.

In addition to the above-mentioned structure, the inner walls of the front case 10 and the rear case 11 of the power transmission device 1 according to this embodiment are provided on the inner wall surfaces of the substantially central portions thereof toward the storage space surrounded by the cases 10 and 11, respectively. Protruding part 4
2, 43 are formed. As shown in the enlarged views of FIGS. 2 and 3, the protrusions 42 and 43 are formed in a substantially symmetrical shape and have protrusion ribs 42a and 43a extending in the vertical direction of the front case 10 and the rear case 11, respectively. ,
The ribs 42a and 43a are formed with bosses 42b and 43b having a substantially circular bulge in the middle of the ribs 42a and 43a.
The lower ends of a and 43a are the upper ends of the low-strength parts 30 and 31,
In other words, it is set at substantially the same height as the upper portion of the rim portion 33 of the tubular portion 12 and the upper portion of the reinforcing rib 32, and
When the front case 10 and the rear case 11 are joined to each other at the joint surface to form the casing 6, the protrusions 42 and 43 are arranged so that the tip portions of the protrusions 42 and 43 are in contact with each other and 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 together, as shown in FIG. 2, both projecting portions 42 and 43 are continuous and both cases 10 and 11 are internally bridged. As a result, it is reinforced against the load acting in the front-back direction of the vehicle body.

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 in the center portion of b, and a through hole 45 that reaches the rear surface of the case 11 is provided in the center portion of the boss 43b on the rear case 11 side. When the casing 6 is configured, the screw hole 44 and the through hole 45 are continuous to form one screw hole for fitting a bolt. The projecting portions 42 and 43 are fastened by the bolts 46 screwed into the screw holes for fitting the bolts, and as a result, the internal bridge structure is made stronger. 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 so that the outer peripheral surface of the casing communicates with the through hole 45 formed therein. Or through the second communication hole 47 and the screw hole for fitting the bolt. That is, the front case 10 and the rear case 11 are joined to each other and the power transmission device 1 is connected.
After assembling, by supplying the lubricating oil from the rear surface opening portion 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 bolts 4 screwed together after the lubricating oil is injected.
Since it is blocked by 6, the lubricating oil in the casing 6 does not leak outside.

As described above, the low-strength portions 30 and 31 having the surface strength lower than those of the other portions are provided around the bearing holding portions 28 and 29 for supporting the front and rear of the second output shaft 8, and The low-strength portion 3 above the low-strength portions 30 and 31
By forming the protrusions 42 and 43 that internally bridge the front case 10 and the rear case 11 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 that pushes the output shaft 8 backward is applied to the second output shaft 8 via the front wheel drive thrust shaft and the sliding yoke 9, this Since the bearing 16 is pushed rearward by the flange portion 49 formed on the second output shaft 8 and the holding portion 29 is further pushed backward by the bearing 16, the power transmission device 1 is not connected to the transmission 4. It leans toward the rear of the vehicle body around the connection portion as a fulcrum, bends, or otherwise comes into contact with the equipment and equipment arranged behind and damages it. Further, the power transmission device 1 disengages from the connection portion with the transmission 4 and moves rearward, or the central portion of the casing 6 breaks to separate a wide range of members rearward,
Similarly, the equipment behind will be adversely affected.

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 exerted from the second output shaft 8 is higher than that of other portions. Since the low-strength portion 31 having a low strength is provided, the low-strength portion 31 is broken when the bearing holding portion 29 is pressed backward as shown in FIG. 4, and as a result, the bearing holding portion 29 is broken. 29
Is separated from the power transmission device 1 and the load applied to the power transmission device 1 is absorbed. Therefore,
There is no fear that the rearward inclination or bending of the power transmission device 1 or the rearward movement of the power transmission device 1 is avoided and the equipment behind is damaged.

Moreover, at this time, since the member disengaged from the power transmission device 1 is the member arranged at the lowermost portion of the device 1, there is little equipment installed behind the lowermost portion,
Further, since only a limited range of members around the bearing holding portion 29 are separated, a wide range of members are not separated and moved backward, and as a result, the bearing holding portion 29 and the like are separated and moved backward. However, the risk of damaging other equipment is reduced.

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

Further, a rim portion 33 and a reinforcing rib 32 of the tubular portion 12 are arranged 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 projecting portions 42 and 43 forming the internal bridge structure reinforced by fastening 46 form the reinforcing portion, the power transmitting apparatus 1 is prevented from tilting backward or bending when a load is applied. At the same time, the low strength portions 30 and 31 are effectively broken by the difference in surface strength between the reinforcing portion and the low strength portions 30 and 31. This ensures that only the members within a limited range around the bearing holding portions 28 and 29 are disengaged.

Further, 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 tubular portion 12 having a D-shaped cross section, and the upper portion is linear and the like. Are distributed in a ring shape, two corners 30a, 30a are formed at the intersections.
As a result, the load applied to the low-strength portion 30 is not evenly distributed and is concentrated on the corner portion 30a, and the low-strength portion 30 is easily broken from the corner portion 30a as a starting point. The breakage of the low-strength portion 30 becomes reliable.

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

[0043]

As described above, according to the present invention, in the power transmission device of the four-wheel drive vehicle having the structure in which the output shaft for outputting the driving force of the engine is provided so as to extend toward the front of the vehicle body,
A low-strength portion having a relatively low strength so that the periphery of the support portion that supports the output shaft in the casing of the power transmission device is broken by a load from the output shaft to the rear of a predetermined value or more. Therefore, when a load of a predetermined value or more is applied to the output shaft from the front of the vehicle and the output shaft is pressed rearward, the low strength portion is broken by the load. As a result, the output shaft or the support portion is separated from the power transmission device to absorb the load, and therefore the power transmission device is tilted rearward or the like to come into contact with another device or equipment arranged behind, Inconveniences such as damage to this are avoided.

Further, since the 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, it is arranged at the rear of the power transmission device when receiving a load. Is prevented and the low strength portion is effectively fractured due to the difference in strength between the reinforcing portion and the low strength portion. As a result, only the minimum part around the output shaft or the support part is reliably separated, and there is no adverse effect such that a wide range of members are separated and come into contact with the equipment arranged behind. .

On the other hand, when the front case and the rear case which are joined to each other are provided with the projecting portions so that the projecting portions are in contact with each other, the front case and the rear case are connected by the bridge structure. The casing formed by joining the two cases is reinforced against the load from the front of the vehicle. Further, when the both projecting portions are fastened with bolts, the reinforcement of the casing can be further strengthened, and when the projecting portion is formed with a side hole that communicates the internal space of the casing with the bolt fitting hole, Since the protruding portion provided as the reinforcing portion can be used for injecting the lubricating oil, it is not necessary to separately provide the lubricating oil inlet.

Furthermore, when the outer periphery of the low-strength portion is formed into a tubular portion and a part of the outer peripheral surface of the tubular portion is formed into a flat surface, corners are formed in the distribution of the low-strength portion. As a result of the load acting on the low-strength portion not being evenly distributed and being concentrated on the corner portion, the low-strength portion is easily fractured starting from this point, and the fracture is ensured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing 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 portion of a front case used in the power transmission device.

[Explanation of symbols]

 8 2nd 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 Corner part 42,43 Projection part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ishimura Grammar 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (4)

[Claims] 1. A first output shaft extending rearward of a vehicle body for outputting a driving force of an engine to a rear wheel side, the first output shaft being arranged in parallel with the first output shaft, extending forward of the vehicle body, and driving force of the engine 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 accommodates these two output shafts and that is provided with a support portion that supports the second output shaft. The second output shaft support portion has a low strength portion with a relatively low strength so that the periphery of the second output shaft support portion is broken by a load from the second output shaft rearward at a predetermined value or more. 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 in. 2. The casing comprises a front case and a rear case joined to the case, and the reinforcing portion is provided with a first protruding portion protruding rearward provided on the front case and a front portion provided on the rear case. The power transmission device for a four-wheel drive vehicle according to claim 1, wherein the power transmission device comprises a second protrusion that protrudes toward the first protrusion and is in contact with the first protrusion. 3. The first projecting portion and the second projecting portion each have a hole that is continuous when the front case and the rear case are joined, and are fastened by a bolt fitted into the hole, The hole in one of the protruding portions penetrates through the inner and outer surfaces of the case, and is formed in at least one of the first protruding portion and the second protruding portion when the hole in the protruding portion is joined to the front case and the rear case. 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. 4. The low-strength portion has an outer periphery which is a tubular portion, and a part of an outer peripheral surface of the tubular portion is formed in a flat shape. A power transmission device for a four-wheel drive vehicle according to claim 2.