Abstract:
A track roller bogie is pivotally supported by a pin assembly, in which a spacer for receiving a thrust load is abolished and the thrust load is supported by outer rings of the pin assembly themselves. It makes possible to assemble a pin assembly easier and to elongate a service life of the track bogie.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a pin assembly, and more particularly to a pin assembly for pivoting a track roller bogie (hereinafter, refer simply to a bogie) of a track-type drive system.  
         [0003]     2. Description of the Prior Art  
         [0004]     The track-type drive system corresponds to a system driving a vehicle by driving a track connecting links having track shoes in an annular shape by pins by means of a sprocket. The drive system mentioned above has a larger ground contact area in comparison with a drive system employing wheels, and is mainly used in a vehicle driving on a rough ground, a snow ground, a weak ground, a battlefield, a civil work field and the like.  
         [0005]     A typical track-type drive system is shown in  FIG. 1 . An idler  2  is pivoted to one end of a track frame  1  swingably attached to a vehicle body, and a sprocket  3  is pivoted to the vehicle body in a direction of another end. A bogie  4  provided with a track roller  5  is mounted to a lower side of the track frame  1 . In general, the track roller or the bogie provided with the track roller is mounted to the track frame in accordance with one type that a position of the track roller is fixed, or another type that the track roller is mounted so as to vertically swing.  FIG. 1  shows a bogie of the latter type that the track roller is mounted so as to freely swing. A crawler belt  6  is wound around a periphery of the idler  2 , the track roller  5  and the sprocket  3 . In accordance with this type, since the track roller  5  can follow to a vertical motion of the crawler belt  6 , it is possible to more stably ground the vehicle.  
         [0006]      FIG. 4  shows a structure cited from U.S. Pat. No. 6,607,256, and shows details in the periphery of the pivotally supported portion of the bogie  4  to the track frame  1  in the swing-type bogie as shown in  FIG. 1 . The bogie  4  in these drawings is constituted by a first bogie link  8  and a second bogie link  23 . First, another end of the first bogie link  8  is bifurcated, and the bifurcated portions are respectively pivoted to the track frame  1  by pins  14 . A second bogie link  23  is rotatably mounted to one end of the first bogie link  8 , and the track roller  5  is mounted to an end portion of the second bogie link so as to freely roll.  
         [0007]     Viewing the pivotally supported portion of the first bogie link  8  to the track frame  1  in detail, a pair of left and right brackets  7  and  7  are arranged on an underside of the track frame  1 , and an opening portion is provided in each of the brackets. A first ring  9  and a third ring  11  are fixed respectively to inner peripheries of the opening portions in a pair of left and right brackets. The pins  14  are fixed to inner peripheral portions of the first ring  9  and the third ring  11 . A second ring  10  is annularly provided between the first ring  9  and the third ring  11  in such a manner as to freely rotate with respect to the pin  14 . Another end of the first bogie link is bifurcated in correspondence to a pair of left and right brackets  7  and  7 , and an outer periphery of the second ring  10  is fixed to an opening portion existing in the branch portion.  
         [0008]     In this case, it is necessary to lubricate a rotating portion between the second ring  10  and the pin  14 , and a slide contact portion among the first, second and third rings by using a lubricant, however, is sealed from an outer portion for the purpose of preventing the lubricant from leaking to the external portion and the purpose of insuring the rotating portion and the slide contact portion against soil grains such as sands, silts and the like.  FIG. 5  is an enlarged view around the rotating portion and the slide surface between the second ring  10  and the third ring  11 . For the purpose of the sealing mentioned above, annular recess portions are provided in positions opposing to contact surfaces of the respective rings, and a pair of left and right face seals  15  and  15  are inserted thereto. The face seals  15  and  15  are pressure contacted by O-rings  16  and  16  so as to prevent a lubricating oil supplied via a lubricant passage  17  from flowing out to an outer portion of the pivotally supported portion together with the O-rings  16  and  16 , and prevent the soil grains from making an intrusion into the rotating portion and the sliding surface from the outer portion.  
         [0009]     Further, spacers  13  formed as a ring having a rectangular cross sectional shape are slidably arranged in inner sides of the face seals  15  and  15  in a radial direction so as to be slidable with respect to each of the second ring  10 , the third ring  11  and the pin  14  in a contact state therewith. The spacer  13  is provided for the purpose of transmitting a load in a thrust direction generated in the case that a drive surface is unevenly brought into contact with the track shoe with keeping a level difference in a lateral direction (a lateral direction in  FIG. 4 ) of the track shoe, between the first ring  9  and the second ring  10 .  
         [0010]     The sealing and lubricating functions required in the contact portion among the first, second and third rings are achieved by the structure of the pivotally supported portion mentioned above, however, since the contact portion requires totally ten parts comprising a pair of face seals, a pair of O-rings and the spacers, it is troublesome to assemble them. Further, in the spacer, it is necessary to lubricate all the outer peripheral surface thereof, however, since the cross sectional shape is rectangular, the lubricating oil is hard to smoothly circulate around the outer surface, so that there is a problem that a service life of the parts is shortened due to seizure or the like. In other words, since a labyrinth is formed in the portion to be lubricated, there is a problem that a lack of lubrication may be generated. Further, in order to solve the problem, there can be considered a method of improving a lubricating property by making the spacer by a porous material such as a porous cast iron or the like, however, in this case, there is a problem that a manufacturing cost is increased.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention is made by taking the circumstances mentioned above into consideration, and an object of the present invention is to provide a pin assembly which can more easily assemble a pivotally supported portion and solves the problem of the lack of lubrication caused by the rectangular spacer, and a track-type drive system which employs the pin assembly.  
         [0012]     In order to achieve the object mentioned above, in accordance with the present invention, there is provided a pin assembly for a bogie of a track-type drive system, comprising: 
        a pin having a lubricant charging hole and a lubricant delivering hole delivering the lubricant from the lubricant charging hole to an outer peripheral portion in an inner portion thereof;     a first ring having a contact surface with the pin in one end so as to be firmly attached to the pin and having an outer diameter D 1 ;     a second ring brought into contact with another end side of the first ring in an axial direction of the pin so as to be rotatably pivoted to the pin and having an outer diameter D 2 ; and     a third ring brought into contact with another end side of the second ring in an axial direction of the pin so as to be firmly attached to the pin and having an outer diameter D 3 ,     wherein a part of a ring end surface contacted among the first, second and third rings has an annular recess portion, and the annular recess portion consists of a sealing means between rings for sealing therebetween, and the outer diameters D 1 , D 2  and D 3  have a relation D 1 &lt;D 2 &lt;D 3 .        
 
         [0018]     Further, in accordance with the present invention, there is provided a pin assembly, wherein the slide portion among the first ring, the second ring and the third ring is constituted by a slide contact surface with which each of the rings is directly contacted, and a seal surface of the sealing means in correspondence to each of the slide contact surfaces, and the slide contact surface and the seal surface form a substantially one flat plane in a radial direction.  
         [0019]     In accordance with another invention, there is provided a track-type drive system comprising: 
        a bogie having a track frame, an idler, a sprocket, a carrier roller and a track roller and pivoted to the track frame; and     a crawler belt wound around them,     wherein the bogie is pivoted to the track frame by the above pin assembly.        
 
         [0023]     In accordance with the other invention, there is provided a track-type drive system comprising: 
        a bogie having a track frame, an idler, a sprocket, a carrier roller and a track roller and pivoted to the track frame; and     a crawler belt wound around them,     wherein the bogie is constituted by a first bogie link pivoted to the track frame, and a second bogie link pivoted to the first bogie link and to which the track roller is mounted, and     wherein the second bogie link is pivoted to the first bogie link by the above pin assembly.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a view showing a general track-type drive system;  
         [0029]      FIG. 2  is a cross sectional view of a pin assembly in accordance with the present invention;  
         [0030]      FIG. 3  is a schematic view of an assembly of a pivotally supported portion of the bogie in accordance with the present invention;  
         [0031]      FIG. 4  is a cross sectional view of a conventional bogie; and  
         [0032]      FIG. 5  is an enlarged view of a part of a conventional pivotally supported portion of the bogie. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]     A description will be given of a particular embodiment of a pin assembly in accordance with the present invention, and a pivoting structure using the same.  
         [0034]      FIG. 2  shows a cross sectional view of a pin assembly in accordance with the present invention, and  FIG. 3  shows a schematic view of an assembly of a pivotally supported portion of the bogie of a track-type drive system achieved by the pin assembly.  
         [0035]     A pin  14  is made of a carbon steel, and has a concentric cylindrical hole open in a left side of the pin  14  in  FIG. 2 . A right side of the hole is formed as an opening having a small diameter, and is closed by a detachable lid. A left side of the pin  14  is pressure inserted to a first ring  9  closing one end (a left side) of the opening so as to form a contact surface  24  with the pin  14 , and strikes a right side of the contact surface  24 . The cylindrical hole within the pin  14  strikes the contact surface  24 , thereby forming the lubricant charging portion  19 , and a lubricant such as a lubricating oil, a grease or the like is charged from a small-diameter opening arranged in a right side of the pin  14 .  
         [0036]     A second ring  10  is rotatably pivoted to the pin  14  in adjacent to a right side of the first ring  9 . Since the first ring  9  is fixed to the pin  14 , a slide portion  21  is formed between both the elements in accordance with a rotation of the second ring  10 . The slide portion  21  is constituted by three parts. First, a slide contact portion  26  in which the first ring  9  is directly brought into contact with the second ring  10  is provided in a portion closest to a inner diameter side of the slide portion  21  in a radial direction. The slide contact portion  26  forms one flat surface in a radial direction. Since the first ring  9  and the second ring  10  are manufactured by the same material (for example, a chrome molybdenum steel), a surface hardening treatment such as a carburizing and quenching or the like is applied to a portion forming the slide contact surface  26  for the purpose of preventing a seizure. Further, the lubricant is supplied from the lubricant charging portion  19  mentioned above via the lubricant delivering hole  18  and the lubricant passage  17 .  
         [0037]     A sealing means having a sealing surface  28  for sealing the lubricant is provided in an outer diameter side of the slide contact surface  26 . The sealing means is constituted by a pair of right and left face seals  15  and  15  and O-rings  16  and  16 . These are clamped by annular recess portions provided in portions corresponding to the first ring and the second ring, and the face seals  15  and  15  are opposed to each other so as to form a contact surface corresponding to the sealing surface  28 . The sealing surface  28  is placed on substantially the same plane as the slide contact surface  26 .  
         [0038]     An outer peripheral surface in which the first ring  9  and the second ring  10  are opposed to each other by an interval about 1 mm is formed in an outermost side of the slide portion  21 . A pressing force of the O-ring is set small such that a force is transmitted mainly by the slide contact surface  26  in the case that a load is applied in a thrust direction in the slide portion  21 . In the prior art mentioned above, the spacer receiving the load in the thrust direction is interposed, however, in the present invention, the load in the thrust direction is transmitted directly by the slide contact surface  26  between the rings. In other words, as the constituting parts interposed between the rings, there is only provided with a sealing means constituted by a pair of O-rings and face seals.  
         [0039]     The third ring  11  is pressure inserted to the pin  14  in the same manner as the first ring  9 . A slide portion  22  between both the rings has the same structure as that of the slide portion  21  mentioned above, and has only a sealing means  30  constituted by a pair of O-rings  16  and  16  and face seals  15  and  15 , and a sealing surface  29  formed by the sealing means and a slide contact surface  27  between both the rings are positioned on the same flat plane.  
         [0040]     Further, the first ring  9 , the second ring  10  and the third ring  11  have respective diameters D 1 , D 2  and D 3 , and have a relation D 1 &lt;D 2 &lt;D 3 . In accordance with the structure mentioned above, it is possible to easily fit to a member pivoting the pin assembly  20  and a pivotally supported member.  
         [0041]     The pin assembly  20  having the structure mentioned above is especially exposed to a great load in both the radial and thrust directions, and is preferably used in the pivoting apparatus of the bogie having the track roller of the track-type drive system in which a lot of dusts exist in the environment where the system is used.  FIG. 3  is a schematic view of a structure in the case of being applied to the pivoting apparatus of the bogie.  
         [0042]     The bogie is constituted by a track roller (not shown in  FIG. 3 ), a first bogie link  8  pivoted to the track frame  1 , and a second bogie link  23  pivoted to the first bogie link  8  and corresponding to a pedestal of the track roller. The pin assembly  20  is used for pivoting the first bogie link  8  to the track frame  1  and pivoting the second bogie link  23  to the first bogie link  8 . Details are as follows.  
         [0043]     The track frame  1  is swingably attached to both side portions of a vehicle (not shown). A bracket  7  having an inverted U-shaped cross sectional shape is protruded from right and left sides of a lower portion of the track frame  1 . An opening for the pin assembly  20  is provided in the bracket  7 . One end of the first bogie link  8  is fitted and inserted to the bracket  7  from a lower side. The first bogie link  8  has an inverted L-shaped side elevational shape, and is structured such that one end is pivoted by the bracket  7  and another end is pivoted by the second bogie link  23 . Accordingly, openings for the pin assembly  20  are provided in one end and another end.  
         [0044]     The pin assembly  20  is integrally pressure inserted to the opening of the bracket  7  from an outer direction of the first bogie link  8 . The first link  9  and the third link  11  correspond to the opening of the bracket  7 , and the second cylinder  10  corresponds to the opening in one end of the first bogie link  8 . Inner diameters of the respective openings are set such diameters as to be interference fitted to the outer diameters D 1 , D 2  and D 3  of the rings. As a result, the first ring  9  and the third ring  11  are fitted to the bracket  7 , and the second ring  10  is fitted to the first bogie link  8 .  
         [0045]     The second bogie link  23  pivotally supports the track roller in one end and another end, and has an opening for the pin assembly  20  in a center portion therebetween. In  FIG. 3 , there is illustrated only a plate in a side portion of the second bogie link. In the same manner as the pivotally supported portion mentioned above, the pin assembly  20  is pressure inserted to the opening in another end of the link from an outer side of the first bogie link  8 . In accordance with the pressure insertion, the first link  9  and the third link  11  of the pin assembly  20  are firmly attached to the first bogie link  8 , and the second link is firmly fitted to the second bogie link  23 .  
         [0046]     In accordance with the present invention, since the contact portions between the first ring and the second ring and between the second ring and the third ring are each constituted by substantially one flat plane in the radial direction of the pin assembly, the lubricant easily circulates around the contact portions and the obstacle in lubrication is hard to be generated. Further, since only the sealing means is interposed in the slide portion while abolishing the spacer, and the ring and the pin are structured as the integral pin assembly, it is possible to easily assemble the pin assembly itself and assemble the pivotally supported portion.  
         [0047]     The description mentioned above is given only of the specific embodiments in accordance with the present invention, and the present invention is not limited to the embodiments. The other aspects of the present invention which those skilled in the art can carry out by studying the drawings, the specification and the claims are included in the technical scope of the present invention.