JP2963008B2 - Track tension adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hydraulic excavator,
The present invention relates to a crawler belt tension adjusting device used for a tracked vehicle such as a hydraulic crane and a bulldozer.

[0002]

2. Description of the Related Art Construction machines such as hydraulic shovels used for construction work for excavating earth and sand and crawler cranes for carrying materials to high places are generally used for traveling on unterrained road surfaces. It has an undercarriage with crawler tracks.

FIG. 5 to FIG. 9 show a hydraulic excavator as an example of a tracked vehicle according to the prior art.

In the drawing, reference numeral 1 denotes a large-sized hydraulic shovel as a tracked vehicle. The hydraulic shovel 1 includes a lower traveling body 2 and an upper revolving body 3 provided on the lower traveling body 2 so as to be capable of turning.
And a working device 4 provided on the front side of the upper swing body 3 so as to be able to move up and down.

[0005] Here, the upper revolving superstructure 3 includes a cab 3A,
It has a machine room 3B provided behind the operator cab 3A and a counterweight 3C provided behind the machine room 3B.

[0006] The working device 4 includes a boom 4A mounted on the front side of the upper swing body 3 so as to be able to move up and down, and the boom 4A.
A arm 4B attached to the tip of the arm A so as to be able to move up and down, and a bucket 4 attached to the tip of the arm 4B so as to be rotatable.
C for excavation work and the like by supplying and discharging working pressure oil to the boom cylinder 4D, the arm cylinder 4E, the bucket cylinder 4F, and the like.

[0007] Reference numeral 5 denotes a track frame constituting a frame of the lower traveling unit 2, and a center frame 6 for supporting the upper revolving unit 3 is disposed at the center of the track frame 5.

Reference numeral 7 denotes a pair of side frames (only one is shown) which are provided on both left and right sides of the center frame 6 and extend in the front-rear direction.
And an upper plate 7 made of a long plate material as shown in FIG.
A, the bottom plate 7B and the left and right side plates 7C, 7C are formed as a rectangular cylinder extending in the front-rear direction by welding or the like. The earth and sand discharge hole 8 is formed in the upper plate 7A at a position near an upper roller 17 described later.

Reference numerals 9 and 10 denote reinforcing partition plates disposed inside the side frame 7 so as to face each other. The partition plate 9 reinforces the side frame 7 and reinforces the side frame 7.
An idler bracket portion 11 for accommodating an idler 15 described later is formed on the distal end side of the bracket. An opening 9 </ b> A into which a tension adjusting cylinder 21 described later is inserted is formed at the center of the partition plate 9.

Reference numerals 12 and 12 denote guide plates located inside the idler bracket portion 11 and protruding inward from the respective side plates 7C of the side frame 7, and the respective guide plates 12 are arranged at predetermined intervals upward and downward. And a pair of left and right upper guide plates 12A, 12A and lower guide plates 12B, 12B. Each of the guide plates 12A, 12B extends along the side frame 7. Here, each upper guide plate 12A is firmly supported in a box structure between an upper plate 7A and each side plate 7C of the side frame 7 by a pair of reinforcing plates 13A, 13A, and each lower guide plate 12B is a pair of reinforcing plates 13A. Reinforcement plate 13
B and 13B form a box structure between the bottom plate 7B of the side frame 7 and each side plate 7C and are firmly supported.

Reference numeral 14 denotes a sprocket as a driving wheel provided on the rear end side of each side frame 7, and the sprocket 14 is rotationally driven by a traveling motor (both not shown) mounted via a speed reducer. .

Reference numeral 15 denotes an idler, which is located on the front end side of each side frame 7 and is rotatably provided in the idler bracket portion 11, as an idler. The shaft 15A is provided integrally. A crawler belt 16 is wound between the idler 15 and the sprocket 14, and the crawler belt 16 is driven by a running motor, so that the sprocket 1
An endless track is formed between the idler 4 and the idler 15, the orbital operation is performed, and the excavator 1 travels.

Are upper rollers disposed on the upper side of the side frame 7, and 18, 18, ... are lower rollers disposed on the lower side of the side frame 7, respectively.
The upper roller 17 and the lower roller 18 guide the crawler belt 16 above and below the side frame 7.

Reference numeral 19 denotes a yoke provided in the idler bracket portion 11 of each side frame 7;
9 has a fitting recess 19A into which a distal end of a hydraulic chamber side rod 30 to be described later is fitted, and a bifurcated distal end of the yoke 19 has an idler shaft 1 of an idler 15.
Idler bearings 20, 20 for rotatably supporting 5A are fixed.

Here, as shown by a chain line in FIG. 7, each idler bearing 20 has an upper guide plate 12A, 12A and a lower guide plate 12B of each guide plate 12 provided in the idler bracket portion 11 of the side frame 7. , 12B are slidably engaged. Accordingly, the idler 15 can be slidably displaced in the front-rear direction of the side frame 7 along each guide plate 12 while being rotatably supported by each idler bearing 20.

Reference numeral 21 denotes a cylinder for adjusting the tension of the crawler belt 16 disposed in the idler bracket portion 11 of each side frame 7. The cylinder 21 for adjusting the tension is a cylinder tube 22, a grease chamber side piston 23 described later, A hydraulic chamber-side piston 25, a grease chamber-side rod 27, a hydraulic chamber-side rod 30, and the like are roughly configured. The tension adjusting cylinder 21 is inserted into an opening 9 </ b> A formed in the partition plate 9 of the side frame 7.

Reference numeral 22 denotes a cylinder tube of a tension adjusting cylinder 21. Inside the cylinder tube 22, a first cylinder portion 22A and a second cylinder portion 2 are arranged as shown in FIG.
2B are formed. Here, the first cylinder unit 2
A grease chamber-side piston 23 is slidably inserted into 2A to define a grease chamber 24, and the grease chamber 24 is filled with grease via a grease nipple (not shown). The hydraulic chamber side piston 25 having a plurality of seal members 25A, 25A,.
Are slidably inserted to define a hydraulic chamber 26, and a hydraulic oil supply / discharge port 22C is opened in the hydraulic chamber 26.

Reference numeral 27 denotes a grease chamber side rod having a base end fixed to a grease chamber side piston 23 defining a grease chamber 24, and the distal end side of the grease chamber side rod 27 has a side frame as shown in FIG. 7 is in contact with the partition plate 10.

Reference numeral 28 denotes a grease chamber side rod cover that closes the first cylinder portion 22A of the cylinder tube 22. The grease chamber side rod cover 28 has a large diameter flange portion 28.
A and a small-diameter boss 28B, and a rod insertion hole 28C is formed at the center. The grease chamber side rod cover 28 is attached to the cylinder tube 22 via a plurality of bolts 29, 29,... To close the first cylinder portion 22A and cover the outer peripheral surface of the grease chamber side rod 27. Etc. are protected.

Reference numeral 30 denotes a hydraulic chamber side rod having a base end fixed to a hydraulic chamber side piston 25 defining a hydraulic chamber 26;
The other end of the hydraulic chamber side rod 30 is connected to the cylinder tube 22.
And fitted into a fitting recess 19A formed on the base end side of the yoke 19 as shown in FIG.

Reference numeral 31 denotes a hydraulic chamber side rod cover for closing the second cylinder portion 22B of the cylinder tube 22. The hydraulic chamber side rod cover 31 comprises a large diameter flange portion 31A and a small diameter boss portion 31B. A rod insertion hole 31C is formed at the center. The hydraulic chamber side rod cover 31 is attached to the cylinder tube 22 via a plurality of bolts 32, 32,.
B is closed, and the outer peripheral surface of the hydraulic chamber side rod 30 is covered to protect it from earth and sand.

Reference numeral 33 denotes a dust seal disposed on the inner peripheral side of the hydraulic chamber side rod cover 31.
The soil and the like are prevented from entering the hydraulic chamber 26 through the gap between the hydraulic chamber side rod 30 and the hydraulic chamber side rod cover 31.

Numeral 34 denotes an accumulator as a gas spring, and the accumulator 34 is an intermediate free piston 3.
4A, the upper gas chamber 34B and the lower oil storage chamber 34C
And is defined. The lower oil storage chamber 34C is connected to the hydraulic chamber 2 of the cylinder tube 22 through the pressure oil supply / discharge port 22C.
6 and a check valve 35 and a relief valve 36
Is connected to a hydraulic pump 37 and a relief valve 38.

The pressure in the hydraulic chamber 26 is maintained at a value set by the accumulator 34, and the length of the rod 30 protruding from the cylinder tube 22 of the hydraulic chamber side rod 30 is set according to the pressure in the hydraulic chamber 26. You. When the tension of the crawler belt 16 is initially adjusted, the grease chamber 24 is filled with grease via a grease nipple or the like, and the filling amount is appropriately changed to adjust the projection length of the grease chamber side rod 27. By changing the distance between the sprocket 14 and the idler 15 shown in FIG.

When the tension of the crawler belt 16 is adjusted by the crawler belt tension adjusting device according to the prior art configured as described above, the grease is filled into the grease chamber 24 of the cylinder tube 22 through the grease nipple. By operating the hydraulic pump 37 to supply pressure oil into the hydraulic chamber 26 of the cylinder tube 22, the pressure in the hydraulic chamber 26 is set to a value set by the accumulator 34 (hereinafter, referred to as a set pressure). Accordingly, the hydraulic chamber side rod 30 projects from the cylinder tube 22 according to the set pressure in the hydraulic chamber 26 and presses the yoke 19. As a result, each of the guide plates 12 in the idler bracket 11
, The idler 15 moves forward of the side frame 7 to increase the distance between the sprocket 14 and the crawler belt 16 so that the crawler belt 16 has a predetermined tension.
The state wound between the idler 4 and the idler 15 is obtained.

Here, when the hydraulic excavator 1 having the crawler belt 16 whose tension has been adjusted travels or the like, the external force in the direction of arrow F is constantly applied to the hydraulic chamber side rod 30 via the idler 15 as shown in FIG. Is working. Then, as the external force increases and decreases, the hydraulic chamber side rod 30 expands and contracts from the cylinder tube 22, the projecting length of the hydraulic chamber side rod 30 changes, and the tension of the crawler belt 16 decreases.
4 is adjusted according to the pressure.

As described above, the crawler belt tension adjusting device changes the interval between the sprocket 14 and the idler 15 as needed by repeatedly moving the hydraulic chamber side rod 30 forward and backward (extend and contract) with respect to the cylinder tube 22. Then, the crawler belt 16 operates so as to always keep the crawler belt 16 in tension when the hydraulic excavator 1 is running.

[0028]

In the prior art described above, when the earth and sand G adhere to the crawler belt 16 as shown in FIG.
6 traverses on an endless track together with the upper roller 17, and peels off from the crawler belt 16 to cause side frames 7.
Falls on the upper plate 7A. Here, the earth and sand discharge hole 8 is formed in a position near the upper roller 17 in the upper plate 7A, and the separated earth and sand G accumulate below the upper roller 17 to hinder the smooth rotation of the upper roller 17. Many of the exfoliated earth and sand G
Through the earth and sand discharge hole 8, it falls below the side frame 7.

However, the tension adjusting cylinder 21 is not shown in FIG.
As shown in FIG. 7, since the soil G is disposed in the side frame 7 in the vicinity of the upper roller 17, the soil G dropped through the earth and sand discharge hole 8 of the side frame 7 accumulates on the upper side of the tension adjusting cylinder 21. Would.

Most of the sediment G deposited on the upper surface of the tension adjusting cylinder 21 is dropped by the vibration of the hydraulic excavator 1 during running or working, and is discharged to the outside. As a result, the hydraulic chamber side rod 30 advances and retreats with respect to the cylinder tube 22, so that the hydraulic chamber side rod 30 and the hydraulic chamber side rod cover 31 enter the gap H between the hydraulic chamber side rod 30 and the hydraulic chamber side rod cover 31, for example, as shown in FIG. When the earth and sand G enters, the earth and sand G falls along the gap H, and is not discharged to the outside.
Will stay in the lower part.

As described above, with the soil G remaining in the gap H between the hydraulic chamber side rod 30 and the hydraulic chamber side rod cover 31, the hydraulic chamber side rod 30 is
When the forward and backward movements are repeated, the earth and sand G move (or roll) in the axial direction together with the hydraulic chamber side rod 30 while adhering to the outer peripheral surface of the hydraulic chamber side rod 30, thereby causing the hydraulic chamber side rod 30 and There is a problem that the dust seal 33 and the like of the hydraulic chamber side rod cover 31 are damaged.

Further, the dust seal 33 is formed by the earth and sand G.
Is damaged, the sediment G penetrates into the hydraulic chamber 26 of the cylinder tube 22 and damages the seal member 25A of the cylinder tube 22 and the hydraulic chamber-side piston 25. There is a problem that a leakage accident or the like occurs, and the time and cost required for repair and replacement of these parts are greatly increased.

The present invention has been made in view of the above-described problems of the prior art, and can reliably prevent soil and the like from staying between a rod and a rod cover constituting a tension adjusting cylinder, and can provide a tension adjusting cylinder. It is an object of the present invention to provide a crawler belt tension adjusting device capable of compensating the smooth operation of the crawler belt for a long period of time and stably and reliably performing the tension adjustment on the crawler belt.

[0034]

In order to solve the above-mentioned problems, a crawler belt tension adjusting device according to the present invention is rotatably provided on a side frame of a truck frame, and has a crawler belt wound around a driving wheel. And a tension adjusting cylinder located in the side frame and disposed between the idler wheel and the side frame.

The first aspect of the present invention is characterized in that the tension adjusting cylinder slides through a tube provided with a rod cover on the distal end side thereof through a sealing member. A piston which is inserted into the tube so as to define a hydraulic chamber in the tube, and a rod which is integrated with the piston on the base end side and projects from the tube via a rod cover on the distal end side. A rod cover extends in the axial direction of the rod , and
The surface side covers a predetermined arc range and the lower side is a notch
In providing the arcuate protrusion became.

Further, as in the invention described in claim 2,
It is preferable that the arc-shaped protrusion has an axial dimension longer than a maximum stroke of the rod.

[0037]

According to the first aspect of the present invention, even if earth and sand from the outside falls into the side frame and accumulates on the upper surface of the tension adjusting cylinder, it is possible to prevent the earth and sand from entering the rod cover. This can be prevented by the arc-shaped protrusion. Also, even if the earth and sand at this time intrudes into the gap between the arc-shaped protrusion and the outer peripheral surface of the rod, the earth and sand will still remain in the arc-shaped gap between the arc-shaped protrusion and the outer peripheral surface of the rod. , It reaches the lower outer peripheral surface of the rod that is not covered by the arc-shaped protrusion, and can be discharged to the outside without staying in the gap.

According to the second aspect of the present invention, the lower outer peripheral surface of the rod that is not covered by the arc-shaped projection is exposed to the outside with an axial dimension longer than the maximum stroke of the rod. In the state where the earth and sand adhere to the outer peripheral surface of the rod on the distal end side of the protrusion, for example, even when the rod is reduced and displaced toward the tube with its maximum stroke, the earth and sand at this time remains between the outer peripheral surface of the rod and the rod cover. There is no intrusion, and the rod can be reliably discharged from the lower outer peripheral surface to the outside.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those in the prior art shown in FIGS. 5 to 9 are denoted by the same reference numerals, and description thereof will be omitted.

In the drawing, reference numeral 41 denotes a tension adjusting cylinder according to the present embodiment. The tension adjusting cylinder 41 has a cylinder tube 22 and a grease chamber side piston 23 substantially in the same manner as the tension adjusting cylinder 21 described in the prior art. , The grease chamber side rod 27, the hydraulic chamber side piston 25, the hydraulic chamber side rod 30, etc., but differ from the prior art in the configuration of the hydraulic chamber side rod cover 42.

Reference numeral 42 denotes a hydraulic chamber side rod cover according to the present embodiment. The hydraulic chamber side rod cover 42 has a large diameter flange portion 42A and a small diameter boss similarly to the hydraulic chamber side rod cover 31 according to the prior art. And a rod insertion hole 42C is formed at the center, but an arc-shaped portion covering the upper surface side of the hydraulic chamber side rod 30 over a predetermined arc range is provided at the distal end side of the boss portion 42B. The protrusion 42D is provided integrally.

Here, the lower side of the arc-shaped projection 42D is
As shown in FIG. 3, a notch 42 </ b> E cut out with a dimension L smaller than the diameter dimension of the hydraulic chamber side rod 30,
The notch 42E exposes the lower outer peripheral surface of the hydraulic chamber side rod 30 to the outside. The axial dimension of the arc-shaped projection 42D is, as shown in FIG. 2, a dimension S ′ (S ′> S) larger than the maximum stroke S of the hydraulic chamber side piston 25 in the hydraulic chamber 26. Is set to

The crawler belt tension adjusting device according to the present embodiment has the above-described configuration, and its basic operation is not particularly different from that of the prior art.

However, according to this embodiment, the upper outer peripheral surface of the hydraulic chamber side rod 30 protruding from the cylinder tube 22 is covered by the arc-shaped projecting portion 42D provided on the distal end side of the hydraulic chamber side rod cover 42. , Arc-shaped protrusion 42
D provided in the hydraulic chamber side rod 30
Since the lower outer peripheral surface is configured to be exposed to the outside, as shown in FIG. 2, even if the earth and sand G that has fallen into the side frame 7 through the earth and sand discharge hole 8 accumulates on the upper surface of the tension adjusting cylinder 41, The arc-shaped projecting portion 42D can prevent the earth and sand G from entering between the hydraulic chamber side rod 30 and the hydraulic chamber side rod cover 42.

Even if the earth and sand G at this time enters the gap H between the hydraulic chamber side rod 30 and the arc-shaped projection 42D as shown in FIG. Gap H
When it falls along the notch 42E, it is discharged to the outside when it reaches the notch 42E. As described above, the earth and sand G is transferred to the hydraulic chamber side rod 30.
And the hydraulic chamber side rod cover 42 can be reliably prevented from stagnating, and the smooth operation of the tension adjusting cylinder 41 can be compensated for a long time.

Further, since the axial dimension of the arc-shaped projection 42D is set to a dimension S 'larger than the maximum stroke S of the hydraulic chamber side piston 25 in the hydraulic chamber 26, the tip side of the arc-shaped projection 42D is set. In the state where the earth and sand G adhere to the upper outer peripheral surface of the hydraulic chamber side rod 30, even when the hydraulic chamber side rod 30 is reduced and displaced toward the cylinder tube 22 with the maximum stroke S of the hydraulic chamber side piston 25, The earth and sand G is dropped along the gap H between the hydraulic chamber side rod 30 and the arc-shaped projection 42D without entering between the hydraulic chamber side rod 30 and the hydraulic chamber side rod cover 42,
It can be discharged from the notch 42E to the outside.

As described above, the dirt G deposited on the upper surface of the tension adjusting cylinder 41 can be reliably prevented from entering between the hydraulic chamber side rod 30 and the hydraulic chamber side rod cover 42. Of the cylinder tube 22 and the seal members 25A of the hydraulic chamber side piston 25 due to the intrusion of the earth and sand G into the hydraulic chamber 26 of the tension adjusting cylinder 41. The tension adjusting cylinder 41
Can be compensated for a long time, and the tension of the crawler belt 16 can be stably adjusted.

Next, FIG. 4 shows a second embodiment according to the present invention. In this embodiment, the same components as those in the first embodiment shown in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted.

In the drawing, reference numeral 51 denotes a two-stage cylinder as a tension adjusting cylinder according to the present embodiment. The two-stage cylinder 51 defines a cylinder tube 52 and a hydraulic chamber 53 in the cylinder tube 52. Hydraulic chamber side piston 54
A hollow rod 55 whose base end is provided integrally with the hydraulic chamber side piston 54 and whose distal end projects from the cylinder tube 52; and a grease chamber side piston 57 which defines a grease chamber 56 in the hollow rod 55. The gland chamber side piston 57 is provided integrally with a base end side, and a small-diameter solid rod 58 protruding from the hollow rod 55 at the front end side.

The hydraulic chamber 53 is formed at a position corresponding to the insertion hole 59A of the partition plate 59 provided in the side frame 7 through a supply / discharge port 60 formed in the bottom of the cylinder tube 52, as will be described later. Pressure oil is supplied and discharged. The yoke 19 is in contact with the distal end of the solid rod 58. Reference numeral 61 denotes a grease supply / discharge passage formed in the axial direction of the solid rod 58. The grease supply / discharge passage 61 allows the grease chamber 56 to communicate with the outside.

Reference numeral 62 denotes a rod cover into which the hollow rod 55 is slidably inserted to cover the cylinder tube 52. A hollow rod 55 is provided at the distal end of the rod cover 62.
Arc-shaped projecting portion 62 that covers the upper outer peripheral surface of the
A is provided. Here, the lower side of the arc-shaped protruding portion 62A becomes a cutout portion 62B cut out with a size smaller than the diameter of the hollow rod 55, and this cutout portion 62B
Thereby, the lower outer peripheral surface of the hollow rod 55 is exposed to the outside. The axial dimension S ′ of the arc-shaped projection 62A is set to be larger than the maximum stroke S of the hydraulic chamber side piston 54 (S ′> S).

Reference numeral 63 denotes an accumulator as a gas spring, and the accumulator 63 is an intermediate free piston 6.
3A, the upper gas chamber 63B and the lower oil storage chamber 63C
And is defined. The lower oil storage chamber 63C communicates with the hydraulic chamber 53 of the two-stage cylinder 51 via a supply / discharge port 60, and is connected to a hydraulic pump 64 via a check valve 65.

In the crawler belt tension adjusting device according to the present embodiment configured as described above, an external force in the axial direction acts on the solid rod 58 via the yoke 19 while the grease chamber 56 is filled with grease. Then, the grease chamber side piston 57
An axial force acts on the hydraulic chamber side piston 54 via the grease filled in the grease chamber 56. Then, according to the difference between the axial force acting on the hydraulic chamber side piston 54 and the pressure (oil pressure) in the hydraulic chamber 53, the pressure oil is supplied to the supply / discharge port 6.
0 through the hydraulic chamber 53 and the oil storage chamber 63C of the hydraulic accumulator 63 through the hollow rod 5.
5 repeatedly moves forward and backward with respect to the cylinder tube 52,
The distance between the sprocket 14 and the idler 15 is changed at any time, and the crawler belt 16 operates so as to always keep the track under tension.

As described above, when the hollow rod 55 repeatedly moves forward and backward with respect to the cylinder tube 52, for example, as shown in FIG.
Even if the sediment G that has fallen through the inner surface accumulates on the upper surface of the two-stage cylinder 51, the intrusion of the sediment G between the hollow rod 55 and the rod cover 62 can be prevented by the arc-shaped protrusion 62A.

Even if the earth and sand G at this time enters the gap between the hollow rod 55 and the arc-shaped projection 62A, the earth and sand G will remain in the same manner as in the first embodiment. 55
Along the gap between the arc-shaped protrusion 62A and the arc-shaped protrusion 62A, and is discharged to the outside through the notch 62B. Therefore, the sediment G can be reliably prevented from staying between the hollow rod 55 and the rod cover 62, and the smooth operation of the two-stage cylinder 51 can be compensated for a long time.

The other constructions, functions and effects of this embodiment are the same as those of the first embodiment.

In each of the above embodiments, an example in which the present invention is applied to a lower traveling body of a large hydraulic excavator has been described. However, the present invention is not limited to this. For example, a tracked vehicle having a crawler track such as a crawler crane or a bulldozer. Can be widely applied to the undercarriage.

[0058]

As described in detail above, according to the first aspect of the present invention, the rod projecting from the tube is provided on the rod cover provided on the tube of the tension adjusting cylinder disposed between the idler wheel and the side frame. Over the specified arc range
By providing the arc-shaped protrusions is lower becomes notch covers I, even gravel or the like is deposited on the upper surface of the tension adjusting cylinder, the earth and sand arcuate projecting from entering the rod cover Can be prevented by the part.

Also, should the earth and sand deposited on the upper surface of the tension adjusting cylinder intrude between the outer peripheral surface of the rod and the arc-shaped protrusion, the earth and sand will be removed from the outer periphery of the rod by the arc-shaped protrusion. When falling along the arc-shaped gap between the surface and
When reaching the notch not covered by the arc-shaped protrusion, it is discharged to the outside, so that it is possible to reliably prevent soil and the like from staying between the rod and the rod cover.

According to the second aspect of the present invention, the lower outer peripheral surface of the rod that is not covered with the arc-shaped projection is exposed to the outside with an axial dimension longer than the maximum stroke of the rod. In the state where earth and sand adhere to the outer peripheral surface of the rod at the distal end side of the protruding portion, for example, even when the rod is reduced to the tube side with its maximum stroke, the earth and sand at this time remains between the outer peripheral surface of the rod and the rod cover. Without dropping along the arc-shaped gap between the arc-shaped projection and the outer peripheral surface of the rod, and can be reliably discharged from the lower outer peripheral surface of the rod to the outside.

Accordingly, it is possible to reliably prevent the tension adjusting cylinder from being damaged by earth and sand entering between the rod and the rod cover or into the hydraulic chamber of the tension adjusting cylinder. The smooth operation of the adjusting cylinder can be compensated for a long time, and the tension adjustment for the crawler belt can be stably performed for a long time.

[Brief description of the drawings]

FIG. 1 is a partially broken external view showing a side frame and the like of a lower traveling body equipped with a crawler belt tension adjusting device according to a first embodiment of the present invention.

2 is a partially broken external view showing a tension adjusting cylinder in FIG. 1 in an enlarged manner.

FIG. 3 is a sectional view taken in the direction of arrows III-III in FIG. 2;

FIG. 4 is a longitudinal sectional view showing a main part of a crawler belt tension adjusting device according to a second embodiment of the present invention.

FIG. 5 is an external view showing a hydraulic excavator equipped with a crawler belt tension adjusting device according to the related art.

FIG. 6 is a partially broken external view showing a side frame and the like of a lower traveling body equipped with a crawler belt tension adjusting device according to a conventional technique.

7 is a sectional view taken in the direction of arrows VII-VII in FIG. 6;

FIG. 8 is a partially broken external view showing the tension adjusting cylinder in FIG. 6 in an enlarged manner.

FIG. 9 is a sectional view taken in the direction of arrows IX-IX in FIG. 8;

[Explanation of symbols]

 Reference Signs List 5 track frame 7 side frame 14 sprocket (drive wheel) 15 idler (idle wheel) 16 crawler track 22, 52 cylinder tube (tube) 25, 54 hydraulic chamber side piston (piston) 26, 53 hydraulic chamber 30 hydraulic chamber side rod (rod) 41) Tension adjusting cylinder 42 Hydraulic chamber side rod cover (rod cover) 42D, 62A Arc-shaped protrusion 51 Two-stage cylinder (tension adjusting cylinder) 55 Hollow rod (rod) 62 Rod cover

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 55/088 B62D 55/30

Claims (2)

(57) [Claims] 1. An idler wheel rotatably provided on a side frame of a truck frame and having a crawler belt wound around a drive wheel, and an idler wheel located in the side frame and between the idler wheel and the side frame. In the crawler belt tension adjusting device comprising a tension adjusting cylinder disposed in the tube, the tension adjusting cylinder is slidable through a tube provided with a rod cover on the distal end side and a seal member in the tube. A rod that is inserted and fitted to define a hydraulic chamber in the tube, and a rod whose base end is integrated with the piston and whose distal end projects from the tube via a rod cover; The rod extends in the axial direction of the rod, and the upper surface of the rod extends over a predetermined arc range.
Track tensioning device characterized by providing the arcuate protrusions is lower it becomes notch covering Te. 2. The crawler belt tensioning device according to claim 1, wherein the arc-shaped projection has an axial dimension longer than a maximum stroke of the rod.