JP2548318Y2 - Double acting hydraulic cylinder - Google Patents

Description

[Detailed description of the invention] a. Purpose of the Invention (Industrial Application Field) The present invention relates to a double-acting hydraulic cylinder used for, for example, performing a telescopic operation of a multi-stage telescopic boom, and further, a hydraulic oil passage is formed in a piston rod thereof. The present invention relates to a double-acting hydraulic cylinder.

(Prior Art) A multi-stage telescopic boom, which is configured by telescopically inserting a distal end boom into a base end boom pivotally attached to a vehicle body, for example, is attached to a crane truck or an aerial work vehicle. I have. The expansion and contraction operation of the multistage telescopic boom is performed by a double-acting hydraulic cylinder incorporated therein.

Here, the tip of the piston rod of such a double-acting hydraulic cylinder faces inward from both radially outwards of the piston rod about an axis orthogonal to the axis of the piston rod. A rod end member having a pair of clevis pin holes is attached as described above, and a similar pin hole is also formed in a side portion of the cylinder tube.
For this reason, for example, insert the clevis pins attached to the inside of both sides of the base end of the base end boom into the clevis pin holes, and insert the clevis pins into the pin holes on the side of the cylinder tube inside the side of the tip boom. By inserting the attached pin, the hydraulic cylinder can be installed in the multi-stage telescopic boom.

In the double-acting hydraulic cylinder as described above, two hydraulic oil ports are provided at the tip of the piston rod, and one of the two hydraulic oil ports is provided inside the piston rod by the hydraulic cylinder. And an oil passage connecting the other to the rod-side oil chamber. By using such a double-acting hydraulic cylinder, an oil feed pipe for supplying hydraulic oil to the hydraulic cylinder in the multi-stage telescopic boom can be facilitated.

Here, when the multistage telescopic boom is contracted, that is, when the hydraulic cylinder is contracted, the pushing force due to the weight of the tip boom or the tip load of the tip boom (lifting load or the weight of the worktable) is applied to the cylinder tube, and the hydraulic pressure is reduced. There is a possibility that the reduction operation speed of the cylinder may become uncontrollable. For this reason, a counterbalance valve is mounted on the oil supply pipe or the like to enable stable control of the expansion and contraction of the boom.

Japanese Unexamined Utility Model Publication No. 1-137989 has proposed a counterbalance valve integrated with the rod tip member. In this structure, between two bottoms of the pair of clevis pin holes in the rod end member, two oil passage holes connected to the two hydraulic oil ports in the axial direction of the piston rod and opened at the end of the rod end member. And a bolt is attached to the outside of the distal end surface of the rod distal end member so as to connect the counter balance valve to these two oil passage holes.

(Problems to be Solved by the Invention) However, in such a case where the counterbalance valve is externally attached to the rod tip member, the joint surface between the tip surface of the rod tip member and the counterbalance valve is not reliably sealed. Thus, there is a problem that a part of the hydraulic oil flowing between the oil passage hole and the counterbalance valve may leak from the joint surface to the outside. Conversely, air may enter from the joint surface and enter the hydraulic oil. The seal is apt to be weakened by a change in hydraulic pressure, vibration, or the like accompanying the operation of the hydraulic cylinder.

Furthermore, when a problem such as hydraulic oil leakage occurs in the counterbalance valve mechanism itself, it is necessary to remove the counterbalance valve from the rod tip member, replace the internal spool, disassemble and assemble, and it takes time for maintenance. There was a problem.

The present invention has been made in view of such circumstances, and an object thereof is to provide a double-acting hydraulic cylinder that can eliminate the above-described hydraulic oil leakage and that is easy to maintain. And

B. Configuration of the Invention (Means for Solving the Problems) In order to achieve the above-mentioned object, a double-acting hydraulic cylinder according to the present invention includes a piston rod having a rod tip member fixed to a tip end thereof, and a piston rod having the same. A double-acting hydraulic cylinder comprising: a piston attached to the base end of the cylinder; and a cylinder tube into which the piston is fitted and whose internal space is divided into a bottom oil chamber and a rod oil chamber. Are provided with two hydraulic oil ports. Inside the piston rod, an oil passage connecting one of the hydraulic oil ports to the bottom oil chamber and the other to the rod oil chamber is formed, and further inside the rod tip member. A counterbalance valve mechanism connected to the two hydraulic oil ports is built in. The counter balance mechanism has a spool hole and a spool disposed slidably in the spool hole and attachable from the outside through an insertion port.

In particular, in the double-acting hydraulic cylinder according to the present invention, a pair of clevis pin holes drilled inward from both radially outer sides of the piston rod around an axis perpendicular to the axis of the piston rod, The counter balance mechanism is provided on the outer surface of the rod tip member, and the counter balance mechanism is disposed in the rod tip member between the bottom surfaces of the pair of clevis pin holes. Are opened in the direction of the axis.

(Operation) In such a double-acting hydraulic cylinder, since the rod tip member itself is used as a valve body for the counterbalance valve mechanism, there is no concern about leakage of hydraulic oil. Further, the tip of the rod can be made more compact than before.

Furthermore, the insertion port of the spool constituting the counterbalance valve mechanism is opened in the axial direction of the piston rod from the outer surface of the distal end of the rod distal member, even in a state where the rod distal member remains attached to the piston rod. It is possible to disassemble and assemble the counterbalance valve mechanism and replace the spool without the boom or the like becoming a hindrance, and it is possible to provide a double-acting hydraulic cylinder that is easy to maintain.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 2, a double-acting hydraulic cylinder (hereinafter simply referred to as a hydraulic cylinder) 1 according to the present invention includes a piston rod 2, a piston 3 attached to a base end of the piston rod 2, A cylinder tube 4 is divided into a bottom side oil chamber 4a and a rod side oil chamber 4b by a piston 3.

The piston rod 2 includes an outer pipe 21 and the outer pipe 21.
And an inner pipe 22 whose base end penetrates and opens from the inner wall side of the outer pipe 21 to the outer wall side. The distal end of the space between the inner wall of the outer pipe 21 and the outer wall of the inner pipe 22 is a first hydraulic oil port 21a, and the space is bored in the piston 3 so as to penetrate between both piston surfaces. A first rod internal oil passage 21b is formed through the through hole 3a and connected to the bottom oil chamber 4a. The tip of the inside of the inner pipe 22 is a second hydraulic oil port 22a, and the space forms a second rod internal oil passage 22b connected to the rod-side oil chamber 4b. Therefore, the hydraulic cylinder 1 is extended by supplying hydraulic oil to the first hydraulic oil port 21a, and contracts by supplying hydraulic oil to the second hydraulic oil port 22a.

By the way, the hydraulic cylinder 1 is mounted in a multi-stage telescopic boom 10 mounted on a vehicle body of an aerial work vehicle, for example, as shown in the figure.

The multi-stage telescopic boom 10 includes a base end boom 11 pivotally mounted on a swivel 15 mounted on a vehicle body so as to be rotatable.
And a distal end boom 12 which is telescopically fitted into the proximal end boom 11. At the end of the end boom 12, a worktable 16 for boarding a worker is attached.

On the distal end side of the piston rod 2 of the hydraulic cylinder 1 is attached to the proximal end of a proximal end boom 11, and the cylinder tube 4 is attached to the distal end boom 12. Therefore, the multi-stage telescopic boom 10 performs telescopic operation in accordance with the telescopic operation of the hydraulic cylinder 1.

The attachment of the distal end of the piston rod 2 to the proximal end of the proximal boom 11 is performed via a rod distal member 100 shown in detail in FIGS. 1A (plan view) and 1B (side view). Will be

The rod tip member 100 is attached to the tip of the piston rod 2 by welding or the like. Further, as shown in FIG.1A, on both side surfaces of the distal end portion of the rod distal member 100,
A pair of clevis pin holes 101 are formed so as to extend inward from both outer sides in the radial direction of the piston rod 2 around an axis 2b orthogonal to the axis 2a of the piston rod 2. The base end boom 11 is inserted into these clevis pin holes 101, 101.
The piston rod 2 is fixed to the base end boom 11 by inserting a clevis pin (not shown) attached so as to protrude inside the base end of the base rod.

The cylinder tube 4 is attached to the tip boom 12 by the pin holes 4c provided at the rod-side end of the cylinder tube 4 in the same manner as the pair of clevis pin holes 101, 101.
This is performed by inserting a pin (not shown) attached so as to protrude inside the base end of the distal end boom 12 into 4c.

Further, between the bottoms 101a, 101a of the clevis pin holes 101, 101 in the rod tip member 100, a counterbalance valve mechanism 1 having the rod tip member 100 as a valve body.
Ten are arranged.

The counterbalance valve mechanism 110 is configured to operate the first hydraulic oil port 22a in accordance with the level of the operating oil pressure in the second valve oil passage 122 connecting the second hydraulic oil port 22a and the second inflow / outlet port 122a opening to the outside. A sequence valve 111 that opens and closes the first valve oil passage 121 that connects the first inlet 21a and the first inflow / outlet 121a that opens to the outside, and a bypass oil passage 121b of the first valve oil passage 121 according to the flow direction of hydraulic oil. Check valve 1 that opens and closes
It consists of 12 and.

In the counterbalance valve mechanism 110, when the operating oil flows from the first inlet / outlet 121a into the first operating oil port 21a (that is, the bottom side oil chamber 4a), the sequence valve 111 is turned left by the urging force of the spring 111a. The check valve 112 is opened to permit the above-mentioned inflow through the bypass oil passage 121b while the check valve 112 is opened to allow the inflow through the bypass oil passage 121b. . Conversely, from the second inflow / outlet 122a to the second hydraulic oil port 22a
When the operating oil flows into the rod-side oil chamber 4b, the operating oil pressure is increased until the force for moving the sequence valve 111 to the right generated by the operating oil pressure becomes equal to the urging force of the spring 111a. When the right power becomes larger than the urging force (that is, when the back pressure becomes excessive), the sequence valve 111 is turned on (ie, when the back pressure is generated in the rod-side oil chamber 4b). The valve moves to the right to open the valve, and the hydraulic oil in the bottom oil chamber 4a flows out to the outside via the first valve oil passage 121. At this time, the check valve 112 is in a closed state. Such operation of the counterbalance valve mechanism 110 enables the multistage telescopic boom 10 to be smoothly extended and extended.

As described above, the counterbalance valve mechanism 110
Since the rod tip member 100 itself is used as a valve body, the possibility of hydraulic oil leakage from the first and second hydraulic oil ports 21a, 22a to the first and second inflow / outflow ports 121a, 122a is extremely low. It can be said that there are few. For this reason, the maintenance of the peripheral portion of the rod tip member 100 and thus the hydraulic cylinder 1 can be made free.

C. As described above, the use of the double-acting hydraulic cylinder of the present invention not only allows the piston rod to be pin-connected to the boom or the like via the rod tip member, but also includes a counterbalance valve mechanism in the rod tip member. However, since the rod end member is built in as a valve body, the risk of hydraulic oil leakage can be extremely reduced compared to the conventional counterbalance valve externally mounted. It is effective for maintenance free. Furthermore, not only can the piston rod distal end be made compact, but also the insertion port of the spool constituting the counterbalance valve mechanism opens from the outer surface of the distal end of the rod distal member in the axial direction of the piston rod. Even in a state where the tip member is still attached to the piston rod, the boom or the like does not hinder the disassembly and assembly of the counterbalance valve mechanism and the replacement of the spool can be easily performed.

[Brief description of the drawings]

1A and 1B are a plan view and a side view of a rod tip member of a double-acting hydraulic cylinder according to the present invention, and FIG. 2 shows a mounting state of the double-acting hydraulic cylinder to a multi-stage telescopic boom. FIG. DESCRIPTION OF SYMBOLS 1 ... Double-acting hydraulic cylinder 2 ... Piston rod, 3 ... Piston 4 ... Cylinder tube, 4a ... Bottom side oil chamber 4b ... Rod side oil chamber 21a ... 1st hydraulic oil port 22a ... 2nd hydraulic oil port 100 ... Rod tip Member 101: Clevis pin hole 110: Counter balance valve mechanism 121a: First inflow / outlet 122a: Second inflow / outlet

Claims (1)

(57) [Scope of request for utility model registration] 1. A piston rod having a rod end member fixedly attached to a distal end thereof, a piston attached to a base end of the piston rod, and an internal space into which the piston is fitted to form a bottom side oil chamber and a rod side. A cylinder tube divided into an oil chamber, wherein the rod tip member is provided with two hydraulic oil ports, and inside the piston rod, one of the hydraulic oil ports is provided in the bottom oil chamber, An oil passage connecting the other end to the rod-side oil chamber is formed, and the rod tip member is disposed therein so as to be slidable in the spool hole and slidably in the spool hole and attachable from the outside through an insertion port. A counterbalance valve mechanism connected to the two hydraulic oil ports, and the piston rod is provided on an outer surface of the rod tip member. A pair of clevis pin holes drilled inward from radially outer sides of the piston rod around an axis perpendicular to the axis of the clevis pin, and a bottom face of the pair of clevis pin holes. Wherein the counterbalance valve mechanism is disposed in the rod tip member, and the insertion opening of the spool is opened in the outer surface of the rod tip member in the axial direction of the piston rod. Double acting hydraulic cylinder.