JPH0142872B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control circuit for an adjuster cylinder provided in a side frame as a tension adjustment and shock absorbing device for a crawler track in a tracked work machine such as a hydraulic excavator or a bulltower. .

(Prior Art) A running body of a crawler-equipped work machine is constructed as shown in FIG. That is, a driven wheel 2 is rotatably attached to one end of the side frame 4, which is a box-shaped structure, via a bearing 6 that can move back and forth, and a driven wheel 2 is attached to the other end by a hydraulic motor (not shown). Drive wheels 3 to be driven are rotatably mounted, and these drive wheels 3
An endless crawler belt 1 is wrapped around the driven wheel 2 and the driven wheel 2, and the crawler belt 1 is supported by a roller 5 attached to a side frame 4.

As shown in FIGS. 3 and 4, between the vertical frame 4a of the side frame 4 and the yoke 7 that supports the bearing 6, there is a hydraulic cylinder 10 for buffering connected to the accumulator 8, and a hydraulic cylinder 10 for the crawler track 1. A cylinder 9 for adjusting tension is connected in series to form an adjuster cylinder 1.
1. That is, the piston rod 9b connected to the piston 9a of the cylinder 9 is brought into contact with the vertical frame 4a of the side frame 4, and a grease chamber B is formed between the piston 9a and the partition plate 12. A piston rod 10b connected to the piston 10a is brought into contact with the yoke 7, a hydraulic oil chamber A is formed between the piston 10a and the partition plate 12, and the hydraulic oil chamber A is connected to the accumulator 8. There is.

In this conventional configuration, after the crawler belt 1 is wound around the driven wheel 2, when grease is press-fitted into the grease chamber B by an appropriate means, the tube of the adjuster cylinder 11, that is, the piston rod 10b moves to the left due to the pressure of the grease. 2, which pushes the yoke 7 supporting the driven wheel 2 outwards, thereby also displacing the driven wheel 2 and tensioning the crawler track 1, the degree of tension being dependent on the amount of grease injected into the grease chamber B. It changes depending on. In addition, if the crawler track 1 gets caught in a rock or the like during running and abnormal tension is generated in the track 1, or if the track 1 receives an impact, the piston rod 1
0b and the piston 10a move to the right, and the hydraulic oil chamber A
Since the oil escapes to the accumulator 8, the abnormal tension in the crawler track 1 is alleviated.

In such an adjuster cylinder, a buffering effect is provided by the pressure absorption effect of the accumulator 8. However, as the pressure absorption effect of the accumulator 8 decreases over time, the oil pressure in the hydraulic oil chamber A decreases. There was a problem in that when an abnormal tension occurs in the crawler track 1, it cannot be absorbed, and the adjuster cylinder 11 and surrounding structures or the vehicle body are damaged.

As a solution to this problem, JP-A-60-
No. 29377 proposed a hydraulic circuit that detects the pressure in grease chamber B or hydraulic oil chamber A and stops the working machine when this pressure is equal to or higher than a predetermined value. If the cylinder 10 reaches the stroke end with the pressure of A being below a predetermined value, the working machine will not stop, so the cylinder 10 will not provide a buffering effect.
Therefore, there is a risk that the adjuster cylinder 11 and the structures around it may be damaged. Therefore, in order to solve such drawbacks, in the conventional device, the stroke of the cylinder 10 is made sufficiently large,
In connection with this, there was a problem in that the storage capacity of the accumulator 8 had to be large.

(Problems to be Solved by the Invention) The present invention has been made in view of these problems, and aims to prevent damage to the adjuster cylinder, etc. caused by the adjuster cylinder reaching its stroke end. An object of the present invention is to provide an adjuster cylinder control circuit for a work machine with a crawler track, which has a structure that allows the following.

(Means for Solving the Problems) The present invention provides a track-equipped work machine in which a hydraulic adjuster cylinder for adjusting and buffering track tension is provided between a yoke that supports a bearing and a side frame. It is characterized by having a means for detecting a stroke end due to track deflection of a star cylinder, and a hydraulic circuit that stops traveling of the working machine when the stroke end is detected by the stroke end detecting means. When the adjuster cylinder reaches the stroke end, the working machine stops running, thereby preventing damage to the adjuster cylinder and the like.

(Embodiment) FIG. 1 shows an embodiment of an adjuster cylinder control circuit according to the present invention, and FIG. 2 shows a mounting structure of a switch valve for detecting the stroke end of an adjuster cylinder in this embodiment. 1st
In the figure, 13 is a pilot hydraulic power source consisting of a hydraulic pump, relief valve, etc. mounted on the work machine;
A traveling hydraulic motor 4 is driven by pressure oil in the main circuit, and is attached to the side frame 4 near the drive wheels. A control valve 15 is inserted into the main circuit to control forward/reverse rotation and stop of the travel hydraulic motor 14, and pilot chambers 15a and 15b are provided on both sides of the control valve. Reference numeral 16 denotes a pilot valve, which consists of a forward pilot valve 16a and a reverse pilot valve 16b. 17a and 17b are shuttle valves for selecting the high pressure side, 18 is a switching valve provided for forced stop of travel, and the pilot chamber 18p is
is connected to the secondary side port of the switch valve 20 that detects the stroke end of the adjuster cylinder 19. The two primary ports of the switching valve 18 are connected to the pilot oil pressure source 13 and the oil tank 21.
The secondary port is connected to the primary port of each of the shuttle valves 17a, 17b, and the other primary port of each shuttle valve 17a, 17b is connected to the forward pilot valve 16a and the reverse pilot valve, respectively. It is connected to each secondary side port of the pilot valve 16b, and each shuttle valve 17
Secondary ports a and 17b are connected to pilot chambers 15a and 15b of the control valve 15, respectively.

FIG. 2 shows the mounting structure of the adjuster cylinder 19 and the mounting structure of the switch valve 20, and the tube 2 of the adjuster cylinder 19.
A rotation prevention mechanism (not shown) in which the head side end plate 23a of No. 3 is fitted into a ring-shaped support tube 22 provided on the vertical frame 4a of the side frame 4, and the other end of the tube 23 is fixed to the side frame 4. It is supported and mounted by a support frame 24 having a diameter. A hydraulic oil chamber A of the adjuster cylinder 19 is filled with hydraulic pressure, and the hydraulic oil chamber A is connected to the accumulator 8. A piston 25 is slidably accommodated in the tube 23 of the adjuster cylinder 19, and a piston rod 26 formed in a hollow space is connected to the piston 25. A piston 27 is slidably disposed within the hollow piston rod 26.
A piston rod 28 is accommodated in the piston 27.
are combined. The piston 27 and the piston rod 28 integral therewith include the piston 2
Crawler tension adjustment fluid supply holes 29a and 29b that communicate with the grease chamber B between 5 and 27 and communicate with each other.
is provided in the axial direction, and a fluid supply port 29c is provided on the side surface of the tip end of the piston rod 28, communicating with the fluid supply hole 29a and having a joint 30 attached thereto.
has been established. The tip of the piston rod 28 is engaged with the yoke 7 that supports the bearing 6 via a detent mechanism, but the details thereof will be omitted. Although the illustration of the hydraulic circuit for the accumulator 8 is omitted, pressure oil can be supplied to the accumulator 8 from the main circuit via a pressure reducing valve (for example, 300
Kg/cm ² is reduced to 103 Kg/cm ² and supplied), and if the oil pressure in the hydraulic oil chamber A exceeds a predetermined value (for example, 175 Kg/cm ² Countermeasures against abnormal pressure are also taken so that the oil in the hydraulic oil chamber A can be discharged.

Next, the mounting structure of the switch valve 20 will be explained. The switch valve 20 is fixed to the side frame 4 via a mounting base 31, and its pilot rod 20a is connected to a stroke end detection rod 33 by a pin 34.
is inserted into the hole 32 provided in the vertical frame 4a and slidably penetrates the end plate 23a of the tube 23 via a seal. The rod 33 is connected to the vertical frame 4a.
A push spring 37 is interposed between the bracket 35 attached to the rod 33 and the spring receiver 36 attached to the rod 33.
The rod 33 is constantly pressed inward to the tube 23, and the tip of the rod 33 protrudes into the tube 23 by, for example, several millimeters. Then, the piston 25 is pushed by the abnormal tension of the crawler track, and when the stroke end is near, the rod 33 is pushed by the piston 25.
This pushes the pilot rod 20a and switches the switch valve 20. Strictly speaking, the stroke end at which the switch valve 20 switches is the case where the piston 25 comes into contact with the end plate 23a, but in the present invention it is used to include the stroke just before the end plate 23a comes into contact.

In this configuration, the impact applied from the crawler track to the adjuster cylinder 19 via the driven wheel 2, bearing 6, and yoke 7 is alleviated by the movement of pressure oil in the hydraulic oil chamber A connected to the accumulator 8 to the accumulator 8. , a buffering effect is achieved. Note that, as in this example, the adjuster cylinder 19 is a double cylinder, and the pressure receiving area of the hydraulic oil chamber A is large, so that a large received pressure can be generated even when the pressure is relatively low. Star cylinder 19
The overall length can be shortened. In addition, if the tension in the crawler track has loosened over the period of use of the working machine, the joint 30, fluid supply port 29
c. Grease chamber B via supply holes 29a and 29b
Track tension can be restored by supplying grease (or pressure oil) to the track.

In the hydraulic circuit shown in FIG. 1, when the forward pilot valve 16a is operated to switch, the forward pilot valve 16a is switched from the lower position to the upper position in the diagram, and the pilot hydraulic power source 13
Pilot pressure oil from the control valve 15 enters the pilot chamber 15a of the control valve 15 via the shuttle valve 17a.
The control valve 15 is switched to the upper position in the figure, and the travel hydraulic motor 14 rotates in the forward direction. On the other hand, the reverse pilot valve 16b
When the switch is operated, the control valve is switched from the lower position in the figure to the upper position, and pilot pressure oil from the pilot hydraulic pressure source 13 is supplied to the pilot chamber 15b of the control valve 15 via the shuttle valve 17b, and the control valve 15 is switched from the lower position in the figure to the upper position. The travel hydraulic motor 14 is switched to the upper position and rotates in the reverse direction.

When the switch valve 20 is in the inoperative position, that is, in the right position in the figure, the pilot chamber 18p of the switching valve 18 communicates with the oil tank 21 via the switch valve 20, so the shuttle valve 17a,
One primary side port of 17b communicates with the oil tank 21 via the switching valve 18. Therefore, by operating the pilot valves 16a and 16b, the control valve 15 is switched as described above.

Here, while the work machine is being moved forward by operating the forward pilot valve 16a,
When the crawler tracks get caught in a foreign object such as a stone and bend, the tracks become abnormally tense, the stroke end detection rod 33 is pushed by the piston 25, and the switch valve 20 is switched from the right position to the left position in Fig. 1. , pilot pressure oil from the pilot hydraulic source 13 is supplied to the pilot chamber 18p of the switching valve 18 through the switch valve 20, and the switching valve 18 is switched from the upper position shown in the drawing to the lower position, and the pilot pressure oil is supplied from the pilot hydraulic pressure source 13 to the pilot chamber 18p of the switching valve 18. Switching valve 18, shuttle valve 17a,
Pilot pressure oil is supplied to the pilot chambers 15a, 15b on both sides of the control valve 15 through the control valve 17b, the control valve 15 is brought to the neutral position, the traveling hydraulic motor 14 is stopped, and the working machine is also stopped. Here, since the abnormal tension in the crawler belt is caused by running, the abnormal tension also disappears by stopping running. When the abnormal tension disappears, the force pressing the piston rod 28 of the adjuster cylinder 19 decreases, the piston 25 moves away from the rod 33, the switch valve 20 returns to the right position, and the switching valve 18 returns to the upper position shown. By operating the pilot valves 16a and 16b, the hydraulic motor 14 can be rotated in the forward or reverse direction. Here, if the abnormal tension is caused by a foreign object being caught, the abnormal tension will occur again as the machine moves forward, but in this case, by moving the working machine backward, the stuck foreign object can be removed from the crawler track.

In this way, when the adjuster cylinder 19 reaches the stroke end, the switching valve 18 is switched, and the pilot chambers 15a,
Since hydraulic pressure is applied to the control valve 15b to bring the control valve 15 to the neutral position and the work machine is stopped, it is possible to prevent the travel from continuing with the adjuster cylinder 19 contracted to the end of its stroke. Damage to the star cylinder and surrounding structures is prevented, and damage to the vehicle body is also prevented.

In the above embodiment, the pilot hydraulic pressure is applied to the pilot chambers 15a and 15b on both sides of the control valve 15 when the switch valve 20 is operated.
In the pipes 37a and 37b connected to the pipes a and 15b,
When the switch valve 20 is not in operation, the pilot chambers 15a and 15b are communicated with the respective secondary ports of the forward pilot valves 16a and 16b, and when the switch valve 20 is in operation, the pilot chambers 15a and 15b are connected to the respective secondary ports of the forward pilot valves 16a and 16b.
Even if switching valves are provided for communicating the ports a and 15b with the oil tank 21, the same effects as in the embodiment described above can be achieved.

Further, in the above embodiment, the stroke end detection rod 33 controls the switch valve 20.
Although the configuration is such that the movement of the rod 33 is directly switched, it is also possible to convert the movement of the rod 33 into a hydraulic or electric signal to switch the switching valve 18 or the like. Furthermore, the stroke end may be detected by, for example, connecting a stroke end detection rod to the piston rod 26 and detecting the stroke end from the amount of movement of the rod.

(Effects of the Invention) As described above, the control circuit for the adjuster cylinder of the present invention includes a stroke end detection means for the adjuster cylinder, and a hydraulic pressure for stopping the working machine when the stroke end is detected by the detection means. Since it is equipped with a circuit, it is prevented from continuing to drive with the adjuster cylinder contracted to the end of its stroke, which prevents damage to the adjuster cylinder and the surrounding structures, and also prevents damage to the vehicle body. .

In addition, since it is prevented from continuing to run with the adjuster cylinder contracted to the end of its stroke, it is possible to effectively utilize the entire stroke of the adjuster cylinder to provide a buffering effect, and therefore, it is not possible to continue driving with the adjuster cylinder contracted to the end of its stroke. There is no need to provide an extra stroke, a more compact adjuster cylinder can be achieved, and the accumulator can also be made more compact. Therefore, it is most suitable for application to equipment such as large working machines, which require miniaturization due to the equipment of the adjuster cylinder. In particular, further miniaturization can be achieved by combining the double cylinder as shown in the embodiment with the present invention.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of the adjuster cylinder control circuit according to the present invention, FIG. 2 is a cross-sectional view showing the mounting structure of the adjuster cylinder and the switch valve for stroke end detection in this embodiment, and FIG. The figure is a side view of a traveling body illustrating a conventional adjuster cylinder, and FIG. 4 is a sectional view showing details of the conventional adjuster cylinder.

Claims (1)

[Claims] 1 A driven wheel is attached to one end of the side frame via a bearing that is movable in the front and back direction, a crawler belt is hung around the driven wheel, and a track tension adjustment and buffering mechanism is installed between the yoke that supports the bearing and the side frame. In a work machine with a track provided with a hydraulic adjuster cylinder, there is provided a means for detecting a stroke end due to deflection of the track of the adjuster cylinder, and a means for detecting a stroke end when the stroke end is detected by the stroke end detecting means. 1. An adjuster cylinder control circuit for a crawler-equipped work machine, comprising a hydraulic circuit for stopping the adjuster cylinder.