JPH0410412Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a hydraulic cylinder used in construction machinery, etc.

(b) Prior Art and Problems to be Solved Conventionally, in this type of hydraulic cylinder, in order to buffer the impact at the sliding end of the piston, as shown in FIGS. 4 and 5, the outer side of the piston 1 is A buffer protrusion 7 is provided that protrudes from the end and fits into the buffer hole 5 opening at the center of the end surface of the cylinder 3 (the bottom surface of the cylinder or the inner surface of the cylinder head) with an appropriate gap. It is provided so as to communicate with the low pressure oil passage 9 and to perform buffering by constricting the buffer hole 5 at the sliding end. At the moment this buffering occurs, the low pressure circuit is throttled and the oil pressure suddenly increases. That is, cylinder 3
A high pressure chamber 1 is formed between the bottom of the piston 1 and the piston 1.
When the piston 1 moves to the left due to the hydraulic pressure applied to the piston 1 and the buffer protrusion 7 begins to fit into the buffer hole 5, the buffer hole 5 is narrowed and the cylinder head 11
The oil pressure in the low pressure chamber 13 formed between the piston 1 and the piston 1 increases rapidly. In recent years, as the performance of hydraulic pumps has improved, there has been a trend to increase the normal pressure of the hydraulic cylinder to improve performance, and for this reason, the oil pressure in the low pressure chamber 13 during the aforementioned buffering at the sliding end has become even higher. As a result, the other strength of the cylinder,
There was a risk that this would have a negative effect on the lifespan of the oil seal.

(e) Means and effects for solving the problem The present invention provides a sub-cylinder connected to the end of the main cylinder, which has an inner diameter larger than the main cylinder, and near the boundary between the main cylinder and the sub-cylinder, A sub-piston having two outer diameter portions that fit into the respective inner diameters is provided, and a main piston is provided that is slidably fitted into the main cylinder and presses the sub-piston at the sliding end to cause the sub-piston to slide; protruding from the outer end of the main piston and passing through the secondary piston;
A buffer protrusion that fits into the buffer hole opening at the center of the end face of the sub-cylinder with an appropriate gap is provided, and this buffer hole is provided in communication with the low-pressure oil passage. By pressing and sliding the piston and fitting the buffer protrusion into the buffer hole, the hydraulic pressure generated in the buffer chamber formed between the end face of the sub-cylinder and the sub-piston is reduced. That is, since the end area of the secondary piston (integrated with the main piston) is larger than the end area of the main piston, the hydraulic pressure generated in the said chamber by the secondary piston is lower than the oil pressure generated by the main piston. It is something.

(d) Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIGS. 1 to 3, the hydraulic cylinder device 21 is constructed as follows. That is,
A main piston 25 is slidably fitted into the main cylinder 23. The main piston 25 is constructed as follows. A cylindrical buffer protrusion 33, a first ring 35, a locking ring 37, and a second ring 3 are provided between the step 29 provided on the piston rod 27 and the notch groove 31 at the end.
9 are arranged in parallel. The locking ring 37 is divided into two parts,
a first ring 35 by a plurality of screws 41, respectively;
It is fixed integrally with the second ring 39, and the cutout groove 3
It is locked at 1. A friction ring 43 and a seal ring 45 are engaged with the outer peripheries of the first ring 35 and the second ring 39. A high pressure chamber 49 communicating with a high pressure oil passage 47 is formed between the main piston 25 and the bottom 46 of the main cylinder 23, and a low pressure chamber 51 is formed on the opposite side. The high pressure oil passage 47 communicates with the oil tank via an operating valve and a hydraulic pump. A sub-cylinder 53 having an inner diameter larger than the inner diameter of the main cylinder 23 is integrally connected to the other end of the main cylinder 23, and the main cylinder 23 and the sub-cylinder 53 are connected together.
A sub-piston 63 is provided in the vicinity of the boundary between the main piston 25 and the main piston 25. It slides under pressure from the main piston 25. A buffer protrusion 33 protruding from the end surface of the first ring 35 is provided on the inner diameter part of the sub-piston 63 so as to be able to pass through it with a large gap. cylinder head 69 engaged by screw 65 through seal ring 67;
An annular wall 71 is provided which abuts on the inner end surface of the holder, and a cutout groove 73 is formed therein. cylinder head 69
A buffer chamber 75 is formed between the auxiliary cylinder 53 and the auxiliary piston 63. The piston rod 27 slidably passes through the inner diameter of the cylinder head 69 via a dust seal 77, a friction ring 79, and a seal ring 81, and a tip of a buffer protrusion 33 with a gentle conical outer periphery is provided on the inner surface. A buffer hole 83 is formed into which the buffer hole 83 can be freely inserted with an appropriate gap, and the buffer hole 83 is connected to a control valve via a low pressure oil passage 85.
It communicates with the oil pump and oil tank. A communication hole 87 is opened at the boundary between the main cylinder 23 and the sub-cylinder 53, and communicates with a chamber 89 formed between the outer circumference of the sub-piston 63 and the inner diameter of the sub-cylinder 53, and communicates with the atmosphere or the upper surface of the oil tank. is connected to.

In the above embodiment, the high pressure oil passage 47 in FIG.
When pressurized oil is sent from the main piston 25 to the high pressure chamber 49, the main piston 25 moves to the left in the figure, and the hydraulic cylinder device 21 extends. The oil in the low pressure chamber 51 passes through the inner diameter part of the sub piston 63 and flows from the buffer hole 83 to the low pressure oil passage 8.
It is discharged at 5. At this time, the sub-piston 63 is urged rightward in FIG. 1 by the hydraulic pressure generated by being throttled by the low-pressure oil passage 85. Main piston 25
moves to the left, and as shown in FIG.
The main piston 25 contacts the sub-piston 63. When the main piston 25 further moves to the left, the sub-piston 33 is pushed by the main piston 25 and moves to the left, and the tip of the buffer protrusion 33 moves to the buffer hole 8.
3, the oil flow flowing into the low pressure oil passage 85 is restricted by the gap between the outer periphery of the buffer protrusion 33 and the buffer hole 83, and as the conical outer periphery of the buffer protrusion 33 enters, , the main piston 2 is further narrowed down.
5 is buffered. Sub piston 6
3 begins to move under pressure from the main piston 25, the pressure in the low pressure chamber 75 is equal to the load obtained by subtracting the load in the opposite direction applied to the piston rod 27 from the hydraulic load in the high pressure chamber 49 applied to the main piston 25. Piston rod 2 from the area of piston 63
7 is added to the area obtained by subtracting the cross-sectional area of piston rod 2. Therefore, as in the past, the piston rod 2 is
Compared to the hydraulic pressure applied to the area obtained by subtracting the cross-sectional area of 7,
The pressure will be much lower and therefore the impact pressure due to the damping will also be much lower. Note that when the oil pressure is switched and pressure oil is sent to the low pressure oil passage 85, the pressure oil flows from the buffer hole 83 to the low pressure chamber 75.
The main piston 2 along with the sub piston 63
5 moves to the right in FIG. 3 and the main piston 25 is in the position shown in FIG. 2, after which only the main piston 25 moves further to the right and returns to the position shown in FIG.

(e) Effects of the invention Since the present invention has the configuration as described in the claims, it is possible to buffer the impact at the sliding end of the piston, and also to reduce the hydraulic pressure generated during damping. This makes it possible to reduce the strength of the cylinder, reduce weight, and extend the life of oil seals, etc.

Note that Figures 4 and 5 show conventional examples.
The same reference numerals as those shown in FIGS. 1 to 3 represent the same components.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of one embodiment of the present invention;
Figure 3 is a side sectional view of the main parts in other postures,
FIG. 4 is a side sectional view of the main part of the conventional example, and FIG. 5 is a side sectional view of the same main part in another posture. 23...Main cylinder, 25...Main piston,
33...Buffer protrusion, 53...Sub-cylinder, 5
9, 61...Outer diameter part, 63...Sub-piston, 83
...Buffer hole, 85...Low pressure oil passage.

Claims (1)

[Scope of utility model registration request] A sub-cylinder 53 having an inner diameter larger than that of the main cylinder 23 is connected to the end of the main cylinder 23, and near the boundary between the main cylinder 23 and the sub-cylinder 53, there are two cylinders that fit into the respective inner diameters. A main piston 25 is provided which is slidably fitted into the main cylinder 23 and presses the sub piston 63 at a sliding end to cause the sub piston 63 to slide. A buffer protrusion 33 is provided that protrudes from the outer end of the main piston 25, passes through the sub-piston 63, and fits into a buffer hole 83 opening at the center of the end surface of the sub-cylinder 53 with an appropriate gap, A hydraulic cylinder characterized in that the buffer hole 83 is provided in communication with a low pressure oil passage 85.