Abstract:
An axle housing assembly has a stable strength against a drive repulsive force and is superior in dimensional precision and maintenance. The axle housing assembly for a vehicle includes: a differential housing for receiving a differential gear; a pair of axle tubes mounted integrally on the right and left sides of the differential housing for receiving respective drive axles; and an axle bracket mounted integrally on at least one of the axil tubes for receiving a repulsive force. In the axle housing assembly, the interconnection between the differential housing and the axle tube and the interconnection between the axle tube and the axle bracket for receiving the repulsive force are performed by bolts, respectfully.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an axle housing assembly for an industrial vehicle such as a forklift or the like. 
     DESCRIPTION OF THE RELATED ART 
     In a forklift, usually, front wheels are drive wheels, and a front axle for transmitting a drive force to the front wheels and a differential gear are received in the axle housing. Such an axle housing is conventionally, in general, composed of a differential housing for receiving a differential gear, and axle tubes coupled by welding, respectively, to the right and left opening portions of the differential housing for receiving a front axle. 
     Also, a type in which the axle housing is separated from an engine portion in order to suppress transmission of vibrations from the engine portion (including a transmission) becomes popular. In such a separation type axle housing, in order to resist the drive repulsive force generated during a starting operation, a braking operation or the like, a proximal portion of a ring portion of an axle bracket is fitted to be fixed to each of axle tubes by welding. The axle brackets are fixed to a base frame by bolts. (refer to the Japanese Patent No. 2,689,819) 
     As described above, in the conventional axle housing assembly, the integral formation is carried out by welding between the differential housing and the axle tubes and between the axle tubes and the axle brackets. 
     However, the welded portion is likely to receive an adverse affect such as a fatigue or the like by the drive repulsive force and there is a problem that non-uniformity in welding quality is likely to occur due to an ability of an individual welding worker. 
     Also, in the case where the axle housing assembly is assembled into the base frame, it is necessary to align through holes for bolt fastening formed in the axle brackets and the base frame, respectively, and a high dimensional precision is required. However, in the case where the differential housing, the axle tubes and axle brackets are integrally formed by welding, a welding strain or the like would occur. As a result, in order to ensure a desired dimensional precision, a high welding ability or technique is required. For this reason, the conventional axle housing assembly has been costly. 
     Furthermore, in the conventional structure, in the case where one of the structural components is broken down or damaged, it is difficult to replace the damaged component only. It is therefore necessary to replace the overall axle housing assembly, resulting in defects in maintenance property. 
     SUMMARY OF THE INVENTION 
     In view of the above-noted defects, an object of the present invention is to provide an axle housing assembly that has a stable strength against the drive repulsive force and is excellent in a dimensional precision and maintenance property in low cost. 
     In order to attain the above-mentioned object, according to the present invention, there is provided an axle housing assembly comprising a differential housing for receiving a differential gear, first and second axle tubes mounted integrally on both sides of the differential housing for receiving respective drive axles, a first axle bracket fixed to a frame of the vehicle and mounted on the first axle tube for receiving a repulsive force, first and second bolt means for fixing the first and second axle tubes, respectively, to the differential housing and a third bolt means for fixing the first axle bracket to the first axle tube. 
     In such a structure, since the coupling between the respective components may be performed by the bolt means, there is no problem that degradation in dimensional precision would occur due to the welding strain or the like. Also, in case of the bolt fastening, the product quality may be kept constant and the replacement of the components may be facilitated. 
     In the case where the repulsive force receiving axle bracket is fixed to the first axle tube by bolts, it is preferable that the bracket mounting portion is formed integrally with an outer circumferential surface of the axle tube, and the axle bracket for receiving the repulsive force is mounted on the bracket mounting portion by the bolt means without coupling with the first axle tube. In this case, it is possible to remove the axle bracket away from the axle tube simply by removing the bolt means without removing the overall axle housing assembly away from the base frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is an exploded perspective view showing the embodiment of an axle housing assembly according to the present invention; 
     FIG. 2 is a vertical sectional view showing a main portion in the axle housing assembly shown in FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention will now be described in detail with reference to FIGS. 1 and 2. In a forklift structured in accordance with the present invention in conjunction with FIG. 1, an axle housing assembly  10  is provided with a differential housing  12  for receiving a differential gear (not shown) and axle tubes  14  and  16  extending on the right and left sides of this differential housing  12 . The axle brackets  18  and  20  are mounted on the axle tubes  14  and  16  and fastened to side members  24  and  26  of a base frame  22  by bolts so that the axle housing assembly  10  is supported to the base frame  22 . Also, in this embodiment, since the axle housing assembly  10  is of a type in which it is separated away from an engine portion (not shown), in order to resist a drive repulsive force, one axle bracket (axle bracket on the left side of the traveling direction of the vehicle in the embodiment shown)  18  is fixed to the axle tube  14 . 
     A differential housing  12  has a central opening portion  28 . A differential carrier  30  for supporting the differential gear and a carrier cover  32  are mounted at the central opening portion  28 . Also, circular opening portions  34  are formed on the respective right and left side surfaces of the differential housing  12 . A front axle (not shown) which is a drive axle connected to the differential gear within the differential housing  12  extends sideways from the opening portions  34 . A boss  36  is formed around a circumferential edge of each opening portion  34 . A plurality of screw holes  38  are formed in the boss  36  for coupling the axle tubes  14  and  16  as described later. 
     The front axles are coaxially disposed in the interior of axle tubes  14  and  16 . The proximal end portions of the axle tubes  14  and  16  are fitted in the corresponding opening portions  34  in the differential housing  12  in a shrink fit manner. Flanges  40  project from the respective outer circumferential surfaces of the axle tubes  14  and  16  at positions away from the proximal ends at a predetermined distance. A plurality of through holes  42  corresponding to the screw holes  38  of the bosses  36  are formed in the flanges  40 . 
     In the case where such axle tubes  14  and  16  are coupled with the differential housing  12 , the respective proximal end portions of the axle tubes  14  and  16  are inserted into the corresponding opening portions  34  of the differential housing  12 , the through holes  42  of the respective flanges  40  are aligned with the corresponding screw holes  38  of the bosses  36  and the axle tubes  14  and  16  are pressed to be inserted until the respective flanges  40  come into contact with the bosses  36 . Then, the bolts  44   a  and the bolts  44   b  are caused to pass through the corresponding through holes  42  and to threadedly engage with the screw holes  38  so that the axle tubes  14  and  16  are fixed to the differential housing  12 . 
     Also, a bracket mounting portion  46  is formed integrally with the outer circumferential surface of one axle tube  14  for mounting the axle bracket  18 . The bracket mounting portion  46  has a portion extending forward of a vehicle and a portion extending rearward of the vehicle and these portions have through holes  48  which extend in the vertical direction. 
     The axle bracket  18  for receiving the repulsive force to be mounted on this bracket mounting portion  46  has a thick portion  50  to be disposed on the upper surface of the bracket mounting portion  46 . As best shown in FIG. 2, screw holes  52  extending from the lower surface of the thick portion  50  upwardly are formed in the thick portion  50 . These screw holes  52  are aligned with the through holes  48  under the condition that the axle bracket  18  is suitably disposed to the bracket mounting portion  46 . Accordingly, the bolts  54  are caused to pass through the through holes  48  from below and fastened to the screw holes  52  so that the axle bracket  18  is fixed to the axle tube  14  and the differential housing  12 , the axle tubes  14  and  16  and the axle bracket  18  form an integral structure. On the other hand, as is understood from FIG. 1, an arcuate circumferential edge portion of the axle bracket  18  is overlapped with a front edge portion of the side member  24  of the base frame  22  and fixed in place by a plurality of bolts  56  and nuts  58 . 
     The axle housing assembly  10  is mainly subjected to the repulsive force in the rotational direction about the front axle at the time of start or brake. However, as described above, since the axle bracket  18  fixed to the base frame  22  is fixed integrally with the axle tube  14  by bolts  54 , it is possible to sufficiently receive the above-described repulsive force at this portion. 
     Incidentally, the other axle bracket  20  is of a conventionally well-known type having a ring portion  60  rotatably engaged with the axle tube  16  for supporting the axle tube  16 . 
     In the axle housing assembly  10  having the above-described structure, the interconnection between the differential housing  12  and the axle tubes  14  and  16  and the interconnection between the axle tube  14  and the axle bracket  18  for receiving the reactive force are assembled by coupling by the bolts  44   a,    44   b  and  54 , respectively. Accordingly, the welding work may be dispensed with when the axle housing assembly  10  is manufactured. Accordingly, it is possible to ensure the quality of the products at substantially the same level irrespective of the worker. Also, since there is no welding strain or the like between the components, the dimensional precision of the completed axle housing assembly  10  as a whole is high. Accordingly, it is possible to readily assemble the axle housing assembly  10  into the base frame  22 . 
     Also, due to the coupling by bolts, it is easy to individually dismount the differential housing  12 , the axle tubes  14  and  16  and the axle brackets  18  and  20 . The maintenance property such as a replacement may therefore be kept well. In particular, in the embodiment shown, since the axle bracket  18  is not of a type which is engaged with the axle tube  14 , it is unnecessary to insert and remove it along the axis of the axle tube  14  in attachment or detachment. For example, in the case where the axle brackets  18  are to be replaced, if the bolts  54  and the bolt/nuts  56  and  58  are removed, it is possible to remove the axle bracket  18  only and it is unnecessary to remove the axle housing assembly  10  as a whole away from the base frame  22 . 
     As described above, the preferred embodiment of the present invention has been explained in detail. It is to be understood that the present invention is not limited thereto or thereby. For example, in the above-described embodiment, only one of the axle brackets is fixed to the axle tube and the other axle bracket is rotatable relative to the axle tube. However, it is possible to take a structure in which the other axle bracket is fixed to be unrotatable relative to the axle tube by bolts. Also, the present invention may be applied to industrial vehicles other than the forklift, for example, a shovel loader or the like. 
     As described above, the axle housing assembly according to the present invention takes a structure for performing the interconnections between the respective components by bolts. It is therefore possible to manufacture the products with ease and in a less costly manner. After the completion of the products, it is possible to obtain the product quality which is stable with high dimensional precision. This contributes to the prevention of the non-uniformity of the vehicle performance. 
     Also, since the dismounting is easy, it is sufficient only to replace the components to be displaced. The maintenance property is enhanced considerably in comparison with that of the prior art.