Abstract:
A crawler-type vehicle undercarriage including a track frame, an idler, a sprocket, a crawler encompassing the idler, track rollers, and the sprocket and the idler, the sprocket and the track frame located to line up in a straight line comprising the crawler-type vehicle undercarriage comprising (i) an idler avoided from pivoting upwardly or downwardly relative to the track frame, (ii) a first arm pivotally mounted at the bottom of the track frame, and (iii) a second arm pivotally connected to end portion of the first arm. The track roller unit adjacent the sprocket is preferably pivoted about a pivot center of the first arm positioned at the bottom of the track frame and toward the idler relative to a pivot center of the second arm. The track roller travel improves a flexibility of the track roller to the crawler, and work in a high tractive force is carried out with the track rollers providing unchangeable real contact areas to the ground.

Description:
TECHNICAL FIELD 
     This invention relates generally to an undercarriage of a crawler-type vehicle having multiple track roller bogie unit, more particularly to a hard bottom undercarriage of the crawler-type vehicle which includes a multiple track roller bogie unit, a track frame pivotally mounted on both side of a vehicle body, an idler rotationally mounted to front portion of the track frame so as to provide longitudinal movement thereon only, and a sprocket located to either sides of the vehicle, and further the idler, the sprocket and the track frame are substantially constructed to lined up in straight line. 
     BACKGROUND ART 
     It is desirable that the track roller disposed most adjacent the idler and the sprocket are respectively required to maintain a proper and good contact with a crawler even when the vehicle is passed over relatively rough terrain. Various methods have been tried to provide so as to achieve these objects. For example, In FIG. 9 is disclosed Japanese patent application No.1998-46233, published patent No. 1999-227643. The track frames  1  resiliently mounted to a pivot shaft  9  fixed to either sides of the vehicle body (not shown), an idler  2  is rotationally mounted at one end portion of the track frame  1  (generally front portion of the vehicle). A sprocket  3  positioned just behind the other end portion of track frame  1  is rotationally mounted adjacent the pivot shaft  9  fixed to either sides of the vehicle body so as to transfer motor drive power to the crawler through transmission and final drive (not shown). Multiple track roller units including track roller  21 ,  22 ,  23  are independently moved up and down under the track frame  1  positioned between the idler  2  and the sprocket  3 . The crawler  6  encompasses the idler  2 , the sprocket and the multiple track rollers  21 ,  22 ,  23 . These track rollers  21 ,  22  are rotationally supported at a lower end portion of arms  4 ,  5  which are mounted at a pin  7  in opposite direction, positioned apart from each other at the bottom of the track frame  1  and pivoted respectively, independently about it. A single pivotal track roller  23  is rotationally supported at lower end portion of an arm  24 , which is mounted relative to a pin as pivotal point G 1  positioned at the front portion of the track frame  1 . When the vehicle is passing over relatively rough terrain, and some portions of the crawler hang down, these track roller units have advantages, because the double bogie track roller units  10   a,    10   b,    10   c,  being in engagement with the track rollers  21 ,  22  and the single track roller  23  also go down and keep proper contacts with the surface of the track shoes, thereby guiding the crawler for a good and quick travel and preventing the flanges of any of track rollers from moving onto the surfaces of the crawler. 
     However, above-mentioned undercarriage has disadvantages as follows: 
     Since the bogie track roller units are designed to be mounted in very small space under the track frame  1 , each arms  4 ,  5  supporting the track rollers  21 ,  22  are respectively limited in length so as to avoid from contacting with the next track rollers on both sides thereof. Therefore, the stroke of travel of the arms  4 ,  5  are limited. The case may be occurred that when the vehicle is passing over relatively rough terrain, the crawler below adjacent the idler or the sprocket tends to deflect downwardly due to its weight and separate the track roller  21 ,  22  therefrom. It could be understood that insufficient arms in length travel up and down for a small amount of the track roller travel, resulting in the track rollers not to provide a quick and proper contact with the deflecting portion thereof and in any of the track rollers moving up potentially the surfaces of the track link. 
     Moreover, when the vehicle goes up a bump, the envelopment along the bump by the crawler is relatively small, because the strokes of the track rollers are not enough. As a result, the track rollers  21 ,  22  are unable to fully support the vehicle weight. Therefore, when the vehicle has been through the bump and the body of the vehicle goes down, heavy load shock occurs to the track  6 , track roller  21 , 22  and other elements of the vehicle. Such a load shock leads to diminish the durability of the vehicle elements and provide a bad ride of operation. 
     In other prior art, for example, Japanese patent application No. 1981-177262, published patent No. 1982-107964 is shown in FIG.  11 . The first arms  61 ,  71  are respectively pivoted about the pin  63 ,  73  (pivot point) positioned at front and rear portion of a track frame  51 . Idlers  52   a  and  52   b  are respectively rotationally mounted at a first member of the first arms  61 ,  71 . The second arms  62 ,  72  are respectively rotationally mounted at a second member of the first arms  61 ,  71 . The track rollers  64 ,  64  and  74 ,  74  are rotationally supported to both end portions of the second arms  62 ,  72 . The stop portions  65 ,  75  are respectively formed on a outer and upper end portions of the first arms  61 ,  71 , while the stop members  66 ,  76  are respectively formed on a front and rear portion of the track frame  51 . The stop portions  65 ,  75  are respectively positioned to contact with the stop members  66 ,  76  upon upward pivoting of the first arms  61 ,  71  to limit such pivoting. 
     While upper portion of the first arm  54  is pivoted about the pins  58  which are located under the track frame  51  and between the track rollers  64 ,  64  and  74 ,  74 , the other portion thereof is pivotally connected to substantially a central portion of the second arm  55 . At either end portions of the second arm  55  are rotationally supported the track rollers  55 ,  57 . The sprocket  53  is rotationally mounted at either sides of the vehicle body and positioned substantially above the rear idler  52   b.  The crawler  56  encompasses the idlers  52   a,    52   b  the sprocket  53  and the track rollers  57 ,  64 ,  74 . It will be seen that this track roller unit has the advantages that a total amount of travel combined an amount of the first arm  54  travel with an amount of the second arm  55  travel provide a quick and proper contact to the rail surfaces of the crawler  56  even when the vehicle is passing over relatively rough terrain. 
     However, when the idlers  52   a,    52   b  are respectively moved up and down in response of the action of the first arms  61 ,  71 , an actual contact area between the track shoe  56  and ground tends to vary. Variation of the actual contact area causes the track rollers to prevent from serving completely as load bearing member. Accordingly, a trouble occurs that resulting frequent slip of the track shoe leads to provide a low tractive force of the vehicle. And also, when the vehicle is traveling backward and goes up a bump, as shown in FIG. 12, the rear idler  52   b  is urged to push downward by track shoe weight the adjacent above thereof, thereby the track rollers  74 , 74  associated with the first arm  71  tends to be prevented from reaching to its lowest position. 
     An amount of the track roller travel most adjacent the front and rear idlers  52   a,    52   b  depend on running condition of the vehicle and balanced condition to the both idlers. Accordingly, the track rollers may be impossible to reaching to its lowest position as described already, result in providing improper contact to the rail surfaces of the track link. 
     It is strongly desirable that a great amount of the bogy track roller travel improves a flexibility of the track roller unit without being affected by the travel conditions, the balanced relation to the idlers and the like. And it is also desired that the work in a high tractive force is carried out with the track rollers provided with an unchangeable contact area to the ground. 
     The present invention is directed to overcoming the shortcomings of the prior attempt at improving adaptability to the track shoe, and securing stable contact areas. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the present invention to provide in the crawler-type vehicle undercarriage having an idler, the sprocket and the track frame located substantially in a straight line, a multiple bogie track roller unit with which a great amount of the bogy track roller travel improves a flexibility of the track roller unit to the crawler without being affected by the travel conditions, the balanced relation to the idlers and the like, and work with a high tractive force is carried out with the track roller provided an invariable contact areas to the ground. 
     It is a still further object of the present invention to provide the crawler-type vehicle comprising an undercarriage which includes the idler, the sprocket and the track frame that includes a first arm pivotally mounted at the bottom of the track frame, a second arm pivotally connected to end portion of the first arm, a track roller unit including a first arm pivotally mounted at the bottom of the track frame, a second arm pivotally connected to end portion of the first arm, and track rollers supported to the either end portion of the second arm. 
     It is a still further object of the present invention to provide in a crawler-type vehicle comprising an undercarriage which includes an idler, the sprocket and the track frame located substantially in a straight line that a first arm pivotally mounted at the bottom of the track frame, the track roller unit most adjacent the sprocket is pivoted about a pivot center of the first arm positioned at the bottom of the track frame, toward the idler relative to a pivot center of the second arm. 
     It is a still further object of the present invention to provide in a crawler-type vehicle comprising an undercarriage which includes an idler, the sprocket and the track frame located substantially in a straight line that track roller units most adjacent the sprocket and the idler are respectively pivoted about the pivot center of the first arm positioned at the bottom of the track frame and toward the central portion of the track frame relative to the pivot center of the second arm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference may be had to the accompanying drawings in which; 
     FIG. 1 is a side view of a crawler-type vehicle; 
     FIG. 2 is a side view of the crawler and a multiple bogie track roller unit of a crawler-type vehicle undercarriage combination; 
     FIG. 3 is a partial side view of the track roller unit of FIG. 2; 
     FIG. 4 is a sectional view taken along with the line  1 — 1  of FIG. 2; 
     FIG. 5 is a sectional view taken along with the line  2 — 2  of FIG. 2; 
     FIG. 6 is a side view of the action of the present invention when the vehicle is passing over relatively rough terrain; 
     FIG. 7 is the crawler-type vehicle incorporating another inventive multiple bogie track roller units of a crawler-type vehicle undercarriage; 
     FIG. 8 is the crawler-type vehicle incorporating another inventive multiple bogie track roller units of a crawler-type vehicle undercarriage; 
     FIG. 9 is a side view of the crawler-type vehicle undercarriage of the first prior art; 
     FIG. 10 is a side view of the action of the first prior art; 
     FIG. 11 is a side view of the crawler-type vehicle undercarriage of the second prior art; and 
     FIG. 12 is a side view of the action of the second prior art. 
     It is to be understood that drawing are not intended as a definition of the invention, but are provided for purpose of illustration only. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and more particularly to FIGS. 1-9, preferred embodiment is shown. Numeral  10  and  40  in FIGS. 1 and 2 refer to a multiple track roller bogie unit and single track roller of the crawler-type vehicle, according to the teachings of the present invention. Showing generally in FIG. 1 is the crawler-type vehicle such as bulldozer including multiple bogie track roller units of the undercarriage. Referring to FIG. 2, a yoke  8  positioned at a front-end portion of the track frame recoils the idler  2  to slide thereon in forward and rearward direction by means of a recoil spring (not shown). The undercarriage includes the track frame  1  disposed at either sides of a vehicle body (not shown), an idler  2  which serves to guide the track rollers and mounted rotationally to the yolk  8  at a front portion of the track frame  1 , a sprocket  3  which serves to convert power from the engine into motion of the track and multiple track roller bogie unit  10  having respectively two track rollers  11 ,  12  positioning pivotally at under the track frame  1 , and single track roller unit  40  supporting track roller  43  adjacent the idler  2 . 
     The sprocket  3  is rotationally mounted on both sides of the vehicle body adjacent the rear end portion of the track frame  1 . The double bogie track roller units  10  of the undercarriage are pivotally mounted under the track frame  1  between the idler  2  and the sprocket  3 . The crawler  6  encompassed the idler  2 , the sprocket  3 , and a plurality of the track rollers  11 ,  12 ,  43 . 
     In FIG. 3, the double bogie track roller unit  10  deposited at the bottom of the track frame  1  most adjacent the sprocket  3  is illustrated in detail (Seen from the right side of the vehicle, differing from FIG.  2 ). While the first portion of the first arm  31  is pivoted about a first pin  33 , the second portion thereof is pivotally connected to a pivot portion located intermediate of the both end of a second arm  32  by means of a second pin  35 . The track rollers  11 ,  12  are respectively and pivotally supported at the both end portions of the second arm  32 . All of first pins  33  at which the first arm  31  is connected to the track frame  1  are deposited at the position between the second pin  35  and the idler  2 , or toward middle portion of the track frame  1 . 
     A resilient elements  44 ,  45  are respectively fixed to the upper portion of the first arm  31  and the bottom of the of the track frame  1 , and positioned to contact each other, upon pivoting of the first arm  31  to limit such pivoting. With such a situation, the resilient elements absorb a heavy load shock occurred to the track rollers  11 ,  12  when the vehicle is passing over relatively rough terrain. 
     The arm  41  is pivoted about a pin  42  most adjacent the idler  2  at the bottom of the track frame  1 . The track roller  43  is pivotally supported at the end portion of the arm  41 . And also, the resilient element  46 ,  47  are respectively fixed on the upper end portion of the arm  41  and the track frame  1 , and positioned to contact each other upon pivoting upwardly of the arm  41  to limit such pivoting. 
     In this embodiment, there are provided that two more sets of the double bogie track roller units  10 , 10  mounted between the double bogie track roller units  10  adjacent the sprocket  3  and the single track roller unit  40  adjacent the idler  2 . With regard to this middle double bogie track roller unit  10 , the positions of the pin  33  relative to the pin  35  may be the same as shown in the FIG.  3 . Likewise, the same is true if that may be opposite as shown in the FIG.  3 . 
     Referring to FIGS. 4,  5 , the double bogie track roller unit  10  will be described in detail. The extending downward plates  9 ,  9  are attached at the bottom portion of the track frame  1 , and outboard and inboard sides thereof. The end portion of the first arm  31  is pivotally mounted between the outboard and inboard plates of the track frame  1  by means of a pair of the first pins  33 . The section of the first arm  31  is formed an inverted U configuration at the end portion thereof. The support member pairs  37 ,  37  are respectively formed to the point portion of the outboard and inboard portion of the inverted chapter U shape of the track frame  1  to extend downwardly therefrom. 
     Similarly, the second arm  32  has laterally a pair of arm members  34 ,  34  which are respectively and pivotally interposed between the support member pairs  37 ,  37 . The arm members  34 ,  34  are pivotally connected to end portion of the first arms  31 ,  31  at their approximately middle portion by the second pins  35 ,  35 . Furthermore, the track rollers  11 ,  12  are pivotally supported at both ends of the second arm  32 , namely between a pair of arm members  34 ,  34 . A pair of brackets  36 ,  36  with a cross section formed L of shape, providing for acting as a guide means are respectively secured to the inside of the support member pairs  37 ,  37 .so that one horizontal portion thereof is positioned outwardly, and other vertical portion thereof is respectively positioned along either side of each endless link chain  6  with them faced in opposite direction each other. The facing vertical portion of the bracket pairs  36 ,  36  is designed to define respectively an angled surface to enable to contact with the inboard end of the track link  48 , actually being positioned to bear against the angle rail portion of the crawler  6  and avoid it from moving laterally. 
     INDUSTRIAL APPLICATION 
     A double bogie track roller unit  10  is utilized with the exception of the track roller  43  adjacent the idler  2 . While the first arm  31  is pivoted about the first pin  33  (Large Bogie Structure), the central pivot portion of the second arm  32  is rotationally connected to the end portion the first arm  31  by means of the second pin  35  (Small Bogie Structure). The resulting amount of the track roller travel is combined with amount L 1  of the first arm travel with an amount L 2  of the second arm travel as illustrated in FIG.  3 . Accordingly, a total amount of the track rollers  11 ,  12  exceeds that of the prior art without affecting the balanced relation to the idle  2  as set forth in the prior art, thereby causing the track rollers  11 , 12  to allow he occurrence of great variation in deflection and to act as guide therefore. A seen in FIG. 6, even when the crawler  6  adjacent and below of the sprocket  3  drops down due to the track weight and a distance between the crawler  6  and tack rollers  11 ,  12  results when the vehicle is traveling backward and goes up a bump, the track rollers  11 ,  12  tend to follow the rail surfaces  49 ,  49  of the track link  48  so as to be in quick and proper contact therewith. 
     Since the idler  2  and the sprocket  3  avoid respectively moving upwardly and downwardly relative to the track frame  1 , what we call a hard idler or a hard sprocket, a real contact area between the crawler  6  and ground is maintained unchanged. In such a case, the track rollers  11 ,  12  tend to follow the track  6  so as to come into quick and proper contact therewith even when the vehicle is passed relatively over a bump. This leads to prevent the flanges of the track rollers from running on the rail surfaces  49 ,  49  of the track link  48  and derailment, and to becoming comfortable to ride in for operator. Since the crawler  6  envelops largely a bump, track rollers  11 ,  12  provide respectively for fully bearing against the vehicle weight. This leads to prevent the shock from occurring just after the vehicle is passed over the bump, result in improving the durability of the vehicle and becoming comfortable to ride in for operator. The unchangeable real contact area between the crawler  6  and ground causes the vehicle to drive in a high tractive force without occurring shoe slip. 
     Since the track rollers  11 ,  12  most adjacent the sprocket  3  is positioned between the sprocket and the first pin  33 , thereby enabling to quickly follow a large deflection of the crawler  6  occurred adjacent below the sprocket  3 . In FIG. 6, it will be seen that when the vehicle is passed over rough terrain in rearward direction, the turning force of the sprocket  3  tends to provide a large deflection of the crawler  6 . With such a situation, the track rollers  11 ,  12  most adjacent below the sprocket  3  provide for following a large deflection of the crawler  6  to be a quick and good contact with the rail surfaces  49 ,  49  thereof, thereby enabling to correct the lateral movement thereof and to causes the track rollers to follow to provide a quick and proper contact with the rail surfaces  49 ,  49  of the track link  48 . 
     A single track roller  43  deposited most adjacent below the idler  2  is mounted pivotally at the end portion of the arm  41  which travels up and down relative to the track frame  1  about the pin  42 . (Large Bogie Structure) Its travel amount is relatively smaller than that of the double bogie track roller because it swings only about arm  41 . It is understood that, differing from the sprocket  3 , the idler  2 , which serves as a guide means for crawler  6  and is not a driving means, is urged to properly recoil against the crawler  6  so that it can maintains good contact with ground and track rollers  11 ,  12  are still in guiding engagement with the crawler. Therefore, the deflection of the crawler  6  within a short distance from the idler  2  is relatively small, and the track roller with swinging motion by the arm  41  (Large Bogie Structure) secures a quick and proper contact therewith. 
     Regarding another embodiment shown in FIG. 7, the same is true if this track roller  43  is replaced with the double bogie track roller unit  10  as set forth. The first pin  33  being pivot point of the first arm  31  is preferably mounted on the track frame  1  so that it is positioned toward rearward relative to the pin  35  of the second arm  32 , or longitudinally toward central portion of the track frame  1 . This causes the track roller to allow following the crawler  6  so as to be in a quick and proper contact therewith and compensating a great amount of the track deflection occurred adjacent the idler  2  when the vehicle passes forwardly over the rough terrain. Accordingly, the following track rollers enable to succeed in following the crawler  6  just after the preceding track rollers. 
     Regarding another embodiment shown in FIG. 8, the same is true if the first pin  33  being pivot point of the first arm  31  of the double bogie track roller unit  10  is pivotally mounted at the position between the pin  35  of the second arm  32  and the sprocket  3 . Accordingly, a great amounts of the double bogie track roller unit travel provides for ensuring to quickly and properly follow the crawler  6  so as to be in a good contact therewith and compensating a great amount of the track deflection occurred adjacent below the sprocket  3  as set forth. This leads to prevent a heavy load shock from occurring just after the vehicle is passed over the bump or derailment of the crawler, result in improving the durability of the vehicle and becoming comfortable to ride in for operator. The unchangeable contact area between the crawler  6  and ground causes the vehicle to drive in a high attractive force without occurring shoe slip. 
     As is evident from the foregoing description, certain aspects of the present invention are not limited to the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications will occur to those skilled in the art. It is accordingly intended that the claims shall cover all such modifications and applications that do not depart from the spirit and scope of the invention.