JP2006300280A - Hydraulic cylinder circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the expansion and contraction of a hydraulic cylinder when a control valve is recovered to a neutral state after its contracting operation while employing a circuit configuration of a neutral block free from a pilot check valve. <P>SOLUTION: First and second expansion cylinders 4, 5 each expanding and contracting a box-type expansion boom are connected in parallel with a hydraulic pump 13 and a tank T through the control valve 19 of the neutral block, and a flow divider 14 and counter balance valves 15, 16 for dividing and collecting flows are mounted at the expansion side of both cylinders 4, 5. A pressure releasing valve 20 switched and operated between a tank position communicated with a tank T and a blocking position is mounted between a contraction-side pressure oil supply pipe conduit 11 and the tank T, and the pressure releasing valve 20 is switched to the tank position for a specific time from a time when the control valve 19 is returned from the cylinder contracting position to the neutral position, thus the contraction-side pressure is released, and the counter balance valves 15, 16 are kept in closed states. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydraulic cylinder circuit in which a plurality of hydraulic cylinders are connected in parallel to a hydraulic pump and a tank and simultaneously expanded and contracted.

  The background art will be described by taking a hydraulic cylinder circuit of a box-type telescopic boom used for a crane, an aerial work vehicle or the like as an example.

  In this type of box-type telescopic boom, as shown in FIG. 2, a basic boom body (fixed boom body) 1 has a plurality of stages of movable boom bodies (explained in the case of two stages for easy understanding) 2 and 3 in a telescope shape. The boom main body is configured by being fitted to the second boom body 2, and the second stage boom body 2 is expanded and contracted by the first expansion cylinder 4, and the third stage boom body 3 is expanded and contracted by the second expansion cylinder 5.

  In this case, as shown in Patent Document 1, a hydraulic cylinder circuit that expands and contracts both telescopic cylinders 4 and 5 simultaneously by the same amount is known.

  This will be described with reference to FIG.

  The expansion side (head side) oil chambers 4a, 5a of the telescopic cylinders 4, 5 are connected to the expansion side pressure oil supply line 8 via the expansion side lines 6, 7, and the contraction side (rod side) oil chambers 4b, 4b. 5b is connected in parallel to the contraction-side pressure oil supply conduit 11 via the contraction-side conduits 9 and 10, and both the expansion-side and contraction-side pressure oil supply conduits 8 and 11 are connected to the hydraulic pump 13 via the control valve 12. And a tank T.

  The control valve 12 is switched from the neutral position A to the extended position B or the reduced position C by the operation of a remote control valve (not shown), and both the expansion cylinders 4 and 5 are simultaneously expanded and contracted by the switching operation of the control valve 12.

  In this case, the cylinder holding pressure is high in the lower first extension cylinder 4 where the load increases, and lower in the second extension cylinder 5 on the upper stage, so that the pump discharge oil flows to the second extension cylinder 5 side on the low pressure side. Many flows and can not be expanded and contracted simultaneously.

  Therefore, in order to ensure this simultaneous expansion and contraction action, a flow divider (dividing and collecting valve) 14 is provided in the extension side pipes 6 and 7.

  Further, counter balance valves 15 and 16 as safety valves are provided on the extension side pipes 6 and 7 so that the both expansion cylinders 4 and 5 are not contracted by a load in a boom extended state.

  The counter balance valves 15 and 16 open when the contraction side pressure (pressure in the contraction side pipes 9 and 10) is introduced as a pilot pressure, and the pilot pressure exceeds a set value.

  In such a hydraulic cylinder circuit, for example, when a drill is attached to the tip of the boom, a push-up force indicated by an arrow A in FIG. 2 acts on the tip of the boom as a reaction force. 5 may grow without permission.

  As a means for preventing the expansion of both the telescopic cylinders 4 and 5, as shown in FIG. 3, the control valve 12 is made to communicate with the neutral return, that is, both the expansion side and contraction side pressure oil supply lines 8 and 11 at the neutral position a. By taking the configuration and providing pilot check valves 17 and 18 on the contraction side conduits 9 and 10, the oil from the contraction side oil chambers 4 b and 5 b of both the expansion cylinders 4 and 5 can be obtained in the neutral state of the control valve. A configuration that prevents outflow (elongation of the cylinders 4 and 5) is employed.

  However, according to this configuration, since expensive pilot check valves 17 and 18 are used, there is a problem that the cost is increased.

  Therefore, as an alternative, a technique using a neutral block control valve 19 as shown in FIG. 4 is known.

In this neutral block system, since both cylinder ports are blocked in the neutral state, it is basically possible to prevent both the telescopic cylinders 4 and 5 from extending. In addition, since the neutral return type pilot check valves 17 and 18 are not required, the cost is low.
Japanese Utility Model Publication No. 7-28184

  However, taking this neutral block circuit configuration causes the following adverse effects.

  That is, there is a case where high pressure is confined in the contraction side (the oil chambers 4b and 5b, the conduits 9 and 10 and the pressure oil supply conduit 11) in a state where the control valve 19 is returned to the neutral state after the cylinder contraction operation.

  In this case, the counter balance valves 15 and 16 are opened by receiving the contraction side pressure as a pilot pressure, and the expansion side oil chambers 4a and 5a of the both expansion cylinders 4 and 5 are connected to each other. It will be in the state connected through.

  In this case, since there is a difference in the holding pressure between the two expansion cylinders 4 and 5, the oil on the extension side moves from the first expansion cylinder 4 on the high pressure side to the second expansion cylinder 5 on the low pressure side. As a result, oil also moves between the contraction-side oil chambers 4b, 5b, so that the second telescopic cylinder 5 (third stage boom body 3) extends and the first telescopic cylinder 4 (second stage boom body 2) extends. Will occur.

  Therefore, the significance of originally taking the circuit configuration of the neutral block to prevent elongation is lost. Moreover, even if the boom total length is constant, the third stage boom body 3 which is thin and low in strength is elongated, which is disadvantageous in terms of crane capacity.

  Therefore, the present invention provides a hydraulic cylinder circuit that can reliably prevent expansion and contraction of the hydraulic cylinder when the control valve is returned to neutral after the reduction operation while taking a circuit configuration of a neutral block that does not use a pilot check valve. It is to provide.

  The invention of claim 1 includes a plurality of hydraulic cylinders and a control valve that blocks the cylinder port in a neutral state, and the hydraulic cylinders are connected in parallel to the hydraulic pump and the tank via the control valves. In the hydraulic cylinder circuit configured to prevent the cylinder contraction operation in the neutral state of the control valve by the counter balance valve that is simultaneously expanded and contracted and operates using the cylinder contraction side pressure as a pilot pressure, A pressure relief valve that switches between a tank position where the compression side pipe line is connected to the tank to release the pressure in the pipe line and a shut-off position that cuts off this communication, and the pressure release valve switching action. Check that the control means to control and the control valve have returned from the cylinder contraction position to the neutral position. Detecting means for detecting and sending to the controller, the control means switches the pressure release valve to the tank position after the neutral return from the contracted position of the control valve, the pressure on the cylinder contraction side, The counter balance valve is configured to be lowered to a pressure that maintains the closed state.

  A second aspect of the present invention is the structure of the first aspect, wherein the plurality of hydraulic cylinders are used as telescopic drive means for simultaneously expanding and contracting the upper and lower movable boom bodies constituting the box-type telescopic boom, A flow divider for dividing flow is provided between the extension side pipe line of the hydraulic cylinder.

  According to a third aspect of the present invention, in the configuration of the first or second aspect, the control means is a pressure at which the pressure of the contraction side pipe line maintains the closed state of the counter balance valve from the neutral return time from the contracted position of the control valve. The pressure relief valve is configured to be switched to the tank position for a time set in advance as the time until the pressure decreases.

  According to a fourth aspect of the present invention, in the configuration of any one of the first to third aspects, an electromagnetic switching valve that is switched by an electric signal from the control means is used as the pressure relief valve.

  According to the present invention, after the neutralization return from the contracted position of the control valve, the pressure on the contraction side is extracted into the tank by the pressure release valve, and the closed state of the counter balance valve is maintained. The oil distribution can be prevented.

  That is, while taking the circuit configuration of the neutral block, it is possible to surely prevent the occurrence of the phenomenon that the hydraulic cylinder expands and contracts when neutral is restored.

  In this case, according to the invention of claim 2, in the hydraulic cylinder circuit of the box-type telescopic boom, it is possible to prevent the phenomenon that the lower cylinder is contracted and the upper cylinder is extended, and the original crane capacity can be secured.

  Further, according to the invention of claim 3, the pressure release operation by the pressure release valve is performed for a preset time (time until the contraction side pressure is reduced to a pressure for holding the counter balance valve in the closed state). Since it is configured, the pressure sensor is unnecessary, compared with a case where the pressure sensor is used to detect the contraction side pressure and the pressure relief valve is switched, which is advantageous in terms of cost.

  On the other hand, according to the invention of claim 4, since the electromagnetic switching valve is used as the pressure release valve, the circuit configuration becomes simpler than the case where the hydraulic pilot type switching valve is used, and the response of switching the pressure release valve. Good quality.

  An embodiment of the present invention will be described with reference to FIG.

  Similar to the conventional hydraulic cylinder circuit shown in FIG. 4, the hydraulic cylinder circuit according to the embodiment includes first and second telescopic cylinders 4 and 5 for extending and retracting the box-type telescopic boom, and a control valve. No. 19 has a neutral block, that is, a configuration in which both cylinder ports are blocked at the neutral position a to prevent oil from flowing.

  In the following embodiment, the same parts as those in the conventional circuit shown in FIG.

  In this hydraulic cylinder circuit, an electromagnetic switching type pressure relief valve 20 is provided between the compression side pressure oil supply pipe 11 and the tank T.

  The pressure release valve 20 is switched from the illustrated shut-off position A to the tank position B communicating with the tank T when a switching command signal is input from the controller 21 as control means.

  On the other hand, a pressure sensor 23 for detecting the reduced pilot pressure of the remote control valve 22 for controlling the control valve 19 is provided, and by this pressure sensor 23, the remote control valve 22, that is, the control valve 19 is operated to the cylinder contraction side, And it is detected that it has been operated from the contraction side to the neutral side and sent to the controller 21.

  The controller 21 is provided with a timer 24. Due to the timing action of the timer 24, the controller 21 switches the pressure relief valve 20 from the controller 21 for a preset time from the time when the control valve 19 is once reduced and then returned to neutral. A signal is sent.

  As a result, the pressure release valve 20 is switched to the tank position B for the set time, and the pressure on the contraction side of both the expansion cylinders 4 and 5 is released to the tank T.

  Here, the set time is determined as a necessary and sufficient time for the contraction side pressure to decrease to the closing pressure of the counter balance valves 15 and 16 according to the working condition of the machine to be applied.

  Therefore, even when a high pressure is trapped on the contraction side at the time of return to neutral, the pressure immediately decreases and the counter balance valves 15 and 16 are held in the closed state. The oil distribution can be prevented.

  That is, while taking the circuit configuration of the neutral block, it is possible to reliably prevent the occurrence of the phenomenon that the expansion and contraction cylinders 4 and 5 expand and contract when returning to neutral.

  Therefore, in the box-type telescopic boom shown in FIG. 2, it is possible to prevent a phenomenon in which the second-stage boom body 2 on the lower stage side is contracted and the third-stage boom body 3 on the upper stage side is extended, which is undesirable in terms of boom strength. The original crane capacity can be secured.

Other embodiments
(1) In the above embodiment, the pressure release action by the pressure release valve 20 is configured to be performed for a set time from the neutral return time after the reduction operation. However, the pressure on the contraction side (for example, the pressure on the contraction side pressure oil supply line 11) ) May be detected by a pressure sensor, and after the return to neutrality, the pressure relief valve 20 may be switched in accordance with the contraction side pressure.

  (2) As the pressure release valve 20, a hydraulic pilot type switching valve is used instead of the electromagnetic switching valve mentioned in the above embodiment, and the pilot pressure from the pilot pressure source is supplied to the pressure release valve 20 by a signal from the controller 21. It may be configured to supply and switch.

  (3) The present invention is particularly suitable for a cylinder circuit for a box-type telescopic boom that simultaneously expands and contracts a plurality of stages of movable boom bodies by the same amount, but widely, a plurality of hydraulic cylinders are connected in parallel to a pump and a tank. It can be applied to a cylinder circuit in which each cylinder is extended and contracted by operating one control valve.

It is a figure which shows the structure of the hydraulic cylinder circuit concerning embodiment of this invention. It is a figure which shows schematic structure of the box-type telescopic boom to which this invention is applied. It is a figure which shows the structure of the conventional hydraulic cylinder circuit which uses the control valve of a neutral return system. It is a figure which shows the structure of the conventional hydraulic cylinder circuit which uses the control valve of a neutral block system.

Explanation of symbols

2 Second stage (lower stage) boom body constituting the box-type telescopic boom 3 Third stage (upper stage side) boom body 4 First telescopic cylinder 5 Second telescopic cylinder 4a, 5a Stretch side oil chamber 4b, 5b Shrink side Oil chamber 6, 7 Stretch side pipe 8 Stretch side pressure oil supply pipe 9,10 Shrink side pipe 11 Shrink side pressure oil supply pipe 13 Hydraulic pump T tank 14 Flow divider (distribution flow valve)
DESCRIPTION OF SYMBOLS 15,16 Counter balance valve 19 Control valve 20 Pressure relief valve 21 Controller as control means 22 Remote control valve 23 Pressure sensor as detection means 24 Timer

Claims (4)

  A plurality of hydraulic cylinders and a control valve that blocks the cylinder port in a neutral state, and the hydraulic cylinders are connected to the hydraulic pump and the tank via the control valves in parallel to be simultaneously expanded and contracted; and In the hydraulic cylinder circuit configured to prevent the cylinder contraction operation in the control valve neutral state by the counter balance valve that operates using the cylinder contraction side pressure as a pilot pressure, the contraction side pipes of the respective hydraulic cylinders are connected to the tank. A pressure relief valve that switches between a tank position for communicating and releasing the pressure in the pipe line and a shut-off position that shuts off this communication; a control means for controlling the switching action of the pressure relief valve; When the control valve returns from the cylinder contraction position to the neutral position, Detecting means for sending to the trawler, and the control means switches the pressure release valve to the tank position after the neutral return from the contracted position of the control valve to change the pressure on the cylinder contraction side of the counter balance valve. A hydraulic cylinder circuit configured to decrease to a pressure that maintains a closed state.   A plurality of hydraulic cylinders are used as expansion / contraction drive means for simultaneously expanding / contracting the movable boom bodies of the upper and lower stages constituting the box-type telescopic boom. 2. The hydraulic cylinder circuit according to claim 1, further comprising a flow divider.   The control means is a pressure release valve for a preset time as a time from when the control valve is reduced to the neutral position from the contracted position until the pressure in the contraction side pipe decreases to a pressure that maintains the closed state of the counter balance valve. 3. The hydraulic cylinder circuit according to claim 1, wherein the hydraulic cylinder circuit is configured to switch to a tank position.   The hydraulic cylinder circuit according to any one of claims 1 to 3, wherein an electromagnetic switching valve that is switched by an electric signal from a control means is used as the pressure release valve.

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