JP2007084331A - Boom derricking hydraulic circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent instantaneous reduction in a piston rod generated when rocking a boom downward from a stopping-holding state and a hunting phenomenon of the boom caused by this instantaneous reduction. <P>SOLUTION: A resistance valve 2 composed of a check valve 3 and a control valve 4 is arranged on a pipe 206 for connecting a directional selector valve 202 to a piston rod side oil chamber 104b. Supply of a hydraulic fluid to the piston rod side oil chamber 104b is started after allowing a return of the hydraulic fluid to the directional selector valve 202 from a cylinder bottom side oil chamber 104a by setting cracking pressure P3 of the control valve 4 higher than cracking pressure P2 of a control valve 207 constituting a part of a counterbalance valve 204 or specifying a structure of the control valve 4 so that response time of opening operation of the control valve 4 becomes longer than response time of opening operation of the control valve 207. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a boom hoisting hydraulic circuit including a counter balance valve.

  An example of a mobile crane provided with a boom driven by a double-acting hydraulic cylinder is shown in FIG.

The mobile crane 100 shown in FIG. 6 is roughly composed of a vehicle unit 101, a swinging trunk 102, and a boom 103. In FIG. 6, the double-acting state is achieved with the outrigger 105 of the vehicle unit 101 grounded to ensure balance. The state is shown in which the piston rod 104c of the hydraulic cylinder 104 is protruded to cause the boom 103 to reach the swing limit, and the boom 103 having a telescopic structure is extended to the maximum extent.
The base of the boom 103 that suspends a heavy object is pivotally attached to the revolving barrel 102, and the boom 103 is raised and lowered by controlling the expansion / contraction operation of the double-acting hydraulic cylinder 104.

  Here, FIG. 7 shows a general configuration example of a boom raising and lowering hydraulic circuit for driving the double-acting hydraulic cylinder 104 that raises and lowers the boom 103.

  The main part of the boom raising and lowering hydraulic circuit 200 shown in FIG. 7 selectively selects the hydraulic oil sent from the hydraulic pump 201 with respect to the cylinder bottom side oil chamber 104a or the piston rod side oil chamber 104b of the double acting hydraulic cylinder 104. And a counter balance valve 204 provided on a pipe line 203 connecting the direction switching valve 202 and the cylinder bottom side oil chamber 104a.

  Specifically, the counter balance valve 204 is provided on the pipe 203 and a check valve 205 for prohibiting the return of hydraulic oil from the cylinder bottom side oil chamber 104a to the direction switching valve 202, and in parallel with the check valve 205. And a spring offset type control valve 207 that is controlled to open and close by using the pressure of the hydraulic oil in the pipe 206 connecting the direction switching valve 202 and the piston rod side oil chamber 104b as a pilot pressure.

  Reference numeral 208 in FIG. 7 is a main relief valve for regulating the maximum pressure of hydraulic oil supplied to the double-acting hydraulic cylinder 104, and reference numeral 209 is hydraulic oil supplied to the piston rod side oil chamber 104b. It is a port relief valve for restricting the maximum pressure.

When the shuttle valve 210 is provided between the pipe line 203 and the pipe line 206, the pressure in the pipe line to which the hydraulic oil is supplied at that time, that is, when the piston rod 104 c protrudes to cause the boom 103 is caused. When the pressure of the hydraulic oil in the pipe line 203 or the boom 103 is swung downward by retracting the piston rod 104 c, the pressure of the hydraulic oil in the pipe line 206 is changed via the shuttle valve 210. The hydraulic oil is fed back to the compensation valve 211 and supplied to the double-acting hydraulic cylinder 104 at a pressure corresponding to the external load acting on the double-acting hydraulic cylinder 104.
Reference numeral 212 denotes a tank for collecting hydraulic oil and circulating it to the hydraulic pump 201.

  In the above configuration, when the direction switching valve 202 is shifted to the left side from the neutral position shown in FIG. 7, the hydraulic oil sent from the hydraulic pump 201 passes through the direction switching valve 202, the pipe line 203, and the check valve 205 to the cylinder. The piston rod 104c is supplied to the bottom side oil chamber 104a and the boom 103 shown in FIG. 6 is raised, and the hydraulic oil accumulated in the piston rod side oil chamber 104b is passed through the pipe 206 and the direction switching valve 202. Are discharged and collected in the tank 212.

When the boom 103 is stopped and held at a desired angle, the direction switching valve 202 is returned to the neutral position shown in FIG. As a result, the hydraulic oil delivered from the hydraulic pump 201 passes through the direction switching valve 202 and is collected in the tank 212, and the pipe lines 203 and 206 are connected to the tank via the throttle valve built in the direction switching valve 202. 211 is connected.
In this state, the hydraulic oil is not supplied to any of the pipe lines 203 and 206, so the pressure of the hydraulic oil in the pipe line 206 does not increase, the control valve 207 is kept in a completely closed state, and at the same time, the cylinder bottom Since the return of the hydraulic oil from the side oil chamber 104a to the direction switching valve 202 is prohibited by the check valve 205, the piston rod 104c is fixed at the current position and the posture of the boom 103 is maintained.

  On the other hand, when swinging downward from the state in which the boom 103 is stopped and held, the direction switching valve 202 is shifted from the neutral position shown in FIG. 7 to the right side. As a result, the hydraulic oil delivered from the hydraulic pump 201 is immediately supplied to the piston rod side oil chamber 104b via the direction switching valve 202 and the pipe line 206, but the pressure of the hydraulic oil in the pipe line 206 is controlled by the control valve 207. Of the cylinder bottom side oil chamber 104a until it reaches a cracking pressure (pilot input pressure required to open the control valve 207 to such an extent that a certain amount of hydraulic oil flows in the control valve 207). Since the oil is not discharged, as a result, the hydraulic oil in the cylinder bottom side oil chamber 104a is slightly compressed by the inflow of the hydraulic oil into the piston rod side oil chamber 104b, and the piston rod 104c is degenerated. Such a phenomenon occurs.

  In particular, as shown in FIG. 6, in a state where the piston rod 104c is protruded greatly and the boom 103 is raised to the vicinity of the swing limit, the volume of the cylinder bottom side oil chamber 104a is increased, so that it is compressed. There is a problem that the absolute amount of hydraulic oil increases and the amount of degeneration of the piston rod 104c increases.

  When supply of hydraulic oil to the piston rod side oil chamber 104b is started under such circumstances, the piston rod 104c is instantaneously retracted, and first, the tip of the boom 103 is determined from the relationship between the span length of the boom 103 and the inertial mass. The center part of the boom 103 is bent in a convex state in such a way as to leave the current position in the current position, and the tip of the boom 103 descends behind this, and further, the tip of the boom 103 jumps up by this reaction. Arise.

When the pressure of the hydraulic oil in the pipe line 206 reaches the opening operation start pressure of the control valve 207 (pilot input pressure required to start the opening operation of the control valve 207), When the control valve 207 constituting the part gradually opens and this pressure reaches the cracking pressure of the control valve 207, the hydraulic oil in the cylinder bottom side oil chamber 104a is substantially allowed to be discharged, and the piston rod 104c is smoothly moved. The state in which the boom 103 can be degenerated, that is, a state in which the counterbalance is effective, is set to the above-described lowering and jumping-up operations of the boom 103 for a while after the hydraulic oil discharge in the cylinder bottom side oil chamber 104a is permitted. Since the hunting phenomenon continues repeatedly, there is a problem that the operation feeling of the boom 103 deteriorates.
Also, in the case where the work is performed with the boom 103 approaching a building or the like, when the central portion of the boom 103 is first bent downward, the belly of the boom 103 becomes a building. There is also the possibility of being hit.

8 shows an operation amount f1 of the direction switching valve 202 when the direction switching valve 202 is shifted from the neutral position shown in FIG. 7 to the right side with the boom 103 raised as shown in FIG. It is the diagram which showed the relationship between the pressure f2 of the inside hydraulic fluid, and the moving speed f3 of the piston rod 104c.
However, the speed indicated by f3 in FIG. 8 represents the moving speed in the contracting direction of the piston rod 104c in the positive direction of the vertical axis in the diagram.

  First, when the switching of the direction switching valve 202 is started by manually operating a remote control lever provided in the cabin of the vehicle unit 101, the direction switching valve 202 is gradually opened according to the operation amount f1 of the direction switching valve 202, The hydraulic oil sent from the hydraulic pump 201 starts to be supplied to the piston rod side oil chamber 104b via the direction switching valve 202 and the pipe line 206, and the output of the hydraulic oil sent from the direction switching valve 202 increases substantially linearly. To do.

As described above, until the control valve 207 starts to open, the hydraulic oil is sent into the piston rod side oil chamber 104b while compressing the hydraulic oil in the cylinder bottom side oil chamber 104a. The hydraulic oil pressure f2 rises with a steep slope as shown in FIG.
At this time, the piston rod 104c is momentarily retracted due to the compression of the hydraulic oil in the cylinder bottom side oil chamber 104a, and the central portion of the boom 103 is temporarily protruded downward so that the tip of the boom 103 remains at the current position. In this state, the boom 103 is bent so that the tip of the boom 103 is swung later (approximately a section at a speed f3 in FIG. 8), and further, the reaction causes the phenomenon that the tip of the boom 103 jumps up (see FIG. 8). (B section in FIG. 8 at the speed f3).

When the hydraulic oil pressure reaches the opening operation start pressure P1 of the control valve 207 while the hydraulic oil pressure f2 in the pipe line 206 increases in this manner, a control that constitutes a part of the counter balance valve 204 is performed. When the valve 207 is gradually opened and the pressure of the hydraulic oil reaches the cracking pressure P2 of the control valve 207, substantial discharge of the hydraulic oil in the cylinder bottom side oil chamber 104a is permitted, and the piston rod 104c is made smooth. The boom 103 can be degenerated and starts swinging downward (section c at the speed f3 in FIG. 8).
However, since the hunting phenomenon that occurs when the switching of the direction switching valve 202 is started does not immediately converge, the moving speed f3 of the piston rod 104c increases while vibrating at the hunting cycle as shown in FIG. Therefore, the feeling of operation of raising and lowering the boom 103 is deteriorated (section c at speed f3 in FIG. 8).

  As a technique for preventing an instantaneous degeneration of the piston rod that occurs when the boom is swung downward from the state in which the boom is stopped and held, an activation control device disclosed in Patent Document 1 is already known.

However, this activation control device adjusts the pilot pressure of the electromagnetic proportional relief valve provided in the pipe line connecting the direction switching valve and the piston rod side oil chamber in proportion to the operation of the remote control lever in the cabin. The pressure of the working oil in the pipe line, that is, the pressure of the working oil in the piston rod side oil chamber is gradually increased to slowly degenerate the piston rod.
In addition, since it is necessary to operate the electromagnetic proportional relief valve, electrical control is required, which may increase the failure factor of the entire apparatus.

Japanese Utility Model Publication No. 5-19604 (paragraph number 0017)

  Therefore, an object of the present invention is that no electrical control is required, and the cylinder bottom side oil is generated by the downturning operation pressure generated in the piston rod side oil chamber when the boom is swung downward from the state where the boom is stopped and held. It is an object of the present invention to provide a boom raising and lowering hydraulic circuit capable of preventing instantaneous degeneration of a piston rod due to compression of hydraulic oil in a chamber and boom hunting phenomenon associated therewith.

The boom raising and lowering hydraulic circuit of the present invention includes a direction switching valve that selectively supplies hydraulic oil to a cylinder bottom side oil chamber and a piston rod side oil chamber of a double acting hydraulic cylinder that raises and lowers the boom,
A check valve provided on a pipe line connecting the direction switching valve and the cylinder bottom side oil chamber, and prohibiting return of hydraulic oil from the cylinder bottom side oil chamber to the direction switching valve, and in parallel with the check valve And a boom raising and lowering hydraulic circuit comprising a counterbalance valve provided with a control valve that is controlled to open and close using the pressure of hydraulic oil in a pipe line connecting the direction switching valve and the piston rod side oil chamber as a pilot pressure. In order to achieve the above-mentioned problem, in particular,
At least the pilot pressure reaches the cracking pressure of the control valve at a position closer to the piston rod side oil chamber than the detection position of the pilot pressure on a pipe line connecting the direction switching valve and the piston rod side oil chamber. In the meantime, a resistance valve for prohibiting hydraulic oil from entering the piston rod side oil chamber from the direction switching valve is provided.

When the boom is caused in the above configuration, as in the prior art, a pipe line connecting the direction switching valve and the cylinder bottom side oil chamber, and a check valve constituting a part of the counter balance valve on the pipe line, The hydraulic oil is supplied to the cylinder bottom side oil chamber of the double-acting hydraulic cylinder via the and the piston rod of the double-acting hydraulic cylinder protrudes to cause a boom.
When the direction switching valve is returned to the neutral position when the boom is raised to a desired angle, the supply of hydraulic oil to the cylinder bottom side oil chamber is stopped. In this state, the pressure of the hydraulic fluid in the pipe line connecting the direction switching valve and the piston rod side oil chamber does not increase, and no substantial pilot pressure acts on the control valve constituting a part of the counter balance valve. The control valve is kept in a completely closed state, and at the same time, the return of hydraulic oil from the cylinder bottom side oil chamber to the direction switching valve is also prohibited by the check valve that forms part of the counter balance valve. The piston rod of the hydraulic cylinder is fixed at the current position without contracting, and the posture of the boom is maintained.
Further, when the boom is swung downward, hydraulic oil is supplied to a pipe line connecting the direction switching valve and the piston rod side oil chamber. As a result, the pressure of the hydraulic fluid in the pipe connecting the direction switching valve and the piston rod side oil chamber gradually increases, but the direction switching valve and the piston rod side oil chamber are connected to each other from the direction switching valve. Since the resistance valve for prohibiting the hydraulic oil from entering the piston rod side oil chamber is provided, the hydraulic oil is not immediately sent to the piston rod side oil chamber. Accordingly, the pressure of the hydraulic oil in the pipe line further increases, and when this pressure reaches the opening start pressure of the control valve that constitutes a part of the counter balance valve, the control valve gradually increases using this pressure as a pilot pressure. When the pressure starts to reach the cracking pressure of the control valve, the return of the hydraulic oil from the cylinder bottom side oil chamber to the direction switching valve is substantially allowed. When the pressure of the hydraulic oil in the pipe connecting the direction switching valve and the piston rod side oil chamber further increases, a resistance valve that prohibits the hydraulic oil from entering the piston rod side oil chamber from the direction switching valve Gradually opens and hydraulic fluid is supplied to the piston rod side oil chamber via a pipe line connecting the direction switching valve and the piston rod side oil chamber. The operation for swinging toward is smoothly started.
Also, the hydraulic oil in the cylinder bottom side oil chamber is inadvertently compressed by the pressure of the hydraulic oil fed into the piston rod side oil chamber at the start of the switching operation for swinging the boom downward, and the piston rod is The problem of momentary degeneration is solved, and the boom feeling when the boom is swung downward from the state where the boom is stopped and held, and the hunting phenomenon at the tip of the boom are prevented.

  More specifically, the aforementioned resistance valve is provided in parallel with a check valve that prohibits the entry of hydraulic oil from the direction switching valve into the piston rod side oil chamber, and the pilot pressure (direction switching valve and It can be constituted by a control valve that is controlled to be opened and closed by the pressure of hydraulic oil in the pipe line connecting the piston rod side oil chambers. By design, the cracking pressure of the control valve that forms part of the resistance valve is set higher than the cracking pressure of the control valve that forms part of the counterbalance valve.

  When such a configuration is applied, when the pressure of the hydraulic oil in the pipe line connecting the direction switching valve and the piston rod side oil chamber reaches the cracking pressure of the control valve constituting a part of the counter balance valve, the cylinder The hydraulic oil is allowed to return from the bottom oil chamber to the direction switching valve, and when this pressure reaches the cracking pressure of the control valve that forms part of the resistance valve, the hydraulic oil to the piston rod side oil chamber Will be started.

  Alternatively, a resistance valve is configured by a check valve that prohibits the hydraulic oil from entering the piston rod side oil chamber from the direction switching valve and a control valve provided in parallel with the check valve, and a part of the resistance valve is configured. The response time of the opening operation of the control valve may be designed to be longer than the response time of the opening operation of the control valve constituting a part of the counter balance valve.

  Specifically, the control valve that constitutes a part of the resistance valve is a spool type, the outer periphery of the spool is superposed on the sealing part of the casing, and the throttle that functions as a throttle valve is provided on the tip of the spool. By using a configuration in which the inside of the spool is used as a damper chamber, and the valve opening operation of the control valve is delayed until the amount of hydraulic oil that escapes from the damper chamber through the throttle reaches the above-described polymerization amount, The response time of the opening operation of a part of the control valve can be increased.

  The hydraulic circuit for boom raising / lowering of the present invention operates from the cylinder bottom side oil chamber to the direction switching valve when the boom of the double-acting hydraulic cylinder for raising and lowering the boom is retracted to swing the boom downward. Since the supply of hydraulic oil to the piston rod side oil chamber is started after allowing the oil to return, the piston rod side oil chamber is moved to the piston rod side oil chamber at the start of the switching operation for swinging the boom downward. The problem that the hydraulic oil in the cylinder bottom side oil chamber is inadvertently compressed by the pressure of the hydraulic oil fed in and the piston rod is momentarily retracted is solved. As a result, the boom is bent and the boom hunting phenomenon when the boom is swung downward from the state where the boom is stopped and held is prevented, and inadvertent contact between the nearby building and the boom is prevented, and the boom Operation feeling is also improved.

  Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an outline of a configuration of a boom hoisting hydraulic circuit 1 according to an embodiment to which the present invention is applied.

  The main part of the boom hoisting hydraulic circuit 1 selectively switches the direction of supplying hydraulic oil sent from the hydraulic pump 201 to the cylinder bottom side oil chamber 104a or the piston rod side oil chamber 104b of the double acting hydraulic cylinder 104. A valve 202, a counter balance valve 204 provided on a conduit 203 connecting the direction switching valve 202 and the cylinder bottom side oil chamber 104a, and a conduit 206 connecting the direction switching valve 202 and the piston rod side oil chamber 104b. It is comprised by the resistance valve 2 provided on the top.

  The counter balance valve 204 is provided on the pipe line 203 to allow the hydraulic oil to be supplied from the direction switching valve 202 to the cylinder bottom side oil chamber 104a, and to supply the hydraulic oil from the cylinder bottom side oil chamber 104a to the direction switching valve 202. A check valve 205 that prohibits return and an opening / closing control that is provided in parallel with the check valve 205 and that uses the hydraulic oil pressure in the pipe 206 that connects the direction switching valve 202 and the piston rod side oil chamber 104b as a pilot pressure. And a spring offset type control valve 207.

  The configuration of the boom 103 driven by the double-acting hydraulic cylinder 104 is the same as that of the conventional example described with reference to FIG. 6, and the double-acting hydraulic cylinder 104, the hydraulic pump 201, the direction switching valve 202, the pipe line 203, the conventional hydraulic circuit for raising and lowering the boom as described with reference to FIG. 7 regarding the configurations and functions of the pipe 206, the main relief valve 208, the port relief valve 209, the shuttle valve 210, the pressure compensation valve 211, and the tank 212. Since it is the same as 200, only the common reference numerals in FIG.

  As shown in FIG. 1, the resistance valve 2 controls a control valve 207 constituting a part of the counter balance valve 204 on a pipe line 206 that connects the direction switching valve 202 and the piston rod side oil chamber 104 b. It is provided at a position closer to the piston rod side oil chamber 104b than a position for taking out the pilot pressure (hereinafter referred to as a pilot pressure detection position P).

Specifically, the resistance valve 2 allows the return of hydraulic oil from the piston rod side oil chamber 104b to the direction switching valve 202 and prohibits the hydraulic oil from entering the piston rod side oil chamber 104b from the direction switching valve 202. And a spring offset control valve 4 that is provided in parallel with the check valve 3 and is controlled to open and close using the hydraulic oil pressure in the pipe 206 at the detection position P as a pilot pressure.
A throttle valve 5 provided in parallel with the check valve 3 and the control valve 4 in FIG. 1 protects the double-acting hydraulic cylinder 104 by coping with the expansion or contraction of the hydraulic oil caused by a temperature change or the like. Further, as shown in FIG. 2, a check valve 6 for preventing cavitation may be provided in parallel with these. The throttle valve 5 and the check valve 6 are not essential components of the resistance valve 2.

The function required for the resistance valve 2 is the pressure of the hydraulic oil in the pipe 206 at the pilot pressure detection position P, that is, the pilot used for opening / closing control of the control valve 207 constituting a part of the counter balance valve 204. The direction until the pressure reaches the cracking pressure P2 of the control valve 207 (the pilot input pressure required to open the control valve 207 to such an extent that a certain amount of hydraulic fluid flows in the control valve 207). This is to prohibit entry of hydraulic oil from the switching valve 202 into the piston rod side oil chamber 104b.
Specifically, this function is the control of the cracking pressure P3 of the control valve 4 (the pilot input pressure required to open the control valve 4 to such an extent that a certain amount of hydraulic oil flows through the control valve 4). The configuration of the control valve 4 is set to be higher than the cracking pressure P2 of the control valve 207, or the response time of the opening operation of the control valve 4 to the same pilot pressure is longer than the response time of the opening operation of the control valve 207. It can be realized by specifying the above or by combining these configurations.

  First, the operation of the boom hoisting hydraulic circuit 1 when a configuration in which the cracking pressure P3 of the control valve 4 is set higher than the cracking pressure P2 of the control valve 207 will be described with reference to the diagram of FIG.

3 shows the operation amount f1 of the direction switching valve 202 when the direction switching valve 202 is shifted from the neutral position shown in FIG. 1 to the right side with the boom 103 raised as shown in FIG. The hydraulic oil pressure f2 in the pipe line 206a between 202 and the resistance valve 2, the hydraulic oil pressure f4 in the pipe line 206b between the resistance valve 2 and the piston rod side oil chamber 104b, and the movement of the piston rod 104c It is the diagram which showed the relationship of the speed f3.
However, the speed indicated by f3 in FIG. 3 represents the moving speed in the contracting direction of the piston rod 104c in the positive direction of the vertical axis in the diagram.

  As shown in FIG. 1, the return of the hydraulic oil in the cylinder bottom side oil chamber 104 b is prohibited by the counter balance valve 204, and the direction switching valve 202 is moved from the neutral position in FIG. Is shifted to the right side, the direction switching valve 202 is gradually opened in accordance with the operation amount f1 of the direction switching valve 202, and the hydraulic oil sent from the hydraulic pump 201 starts to be supplied to the pipe line 206a via the direction switching valve 202. .

  As a result, the pressure of the hydraulic oil in the pipe line 206a increases substantially linearly, but entry of the hydraulic oil from the direction switching valve 202 to the piston rod side oil chamber 104b is prohibited between the pipe line 206a and the pipe line 206b. Since the resistance valve 2 is provided, this hydraulic oil is immediately fed into the piston rod side oil chamber 104b at least until the pressure of the hydraulic oil in the pipe line 206a reaches the cracking pressure P3 of the control valve 4. It will never be. Accordingly, at this stage, the pressure of the hydraulic oil in the piston rod side oil chamber 104b does not increase (section A in FIG. 3).

  Until the control valve 4 constituting a part of the resistance valve 2 starts to open, the hydraulic oil is sent to the pipeline 206a in a state where the pipeline 206a is sealed by the resistance valve 2, so that the pipeline The hydraulic oil pressure f2 in 206a rises with a steep slope as shown in FIG. 3 (section A in FIG. 3).

  And while the pressure f2 of the hydraulic oil in the pipe line 206a increases in this way, the pressure f2 of the hydraulic oil in the pipe line 206a starts the opening operation start pressure of the control valve 207 (the control valve 207 starts the opening operation). When the pilot input pressure (P1 required for the control) P1 is reached, the control valve 207 constituting a part of the counter balance valve 204 starts gradually opening (section B in FIG. 3).

  Next, when the pressure f2 of the hydraulic oil in the pipe line 206a reaches the cracking pressure P2 of the control valve 207, the hydraulic oil in the cylinder bottom side oil chamber 104a is substantially allowed to be discharged, and the piston rod 104c is externally loaded. Then, the piston rod 104c starts to degenerate smoothly due to its own weight (section C in FIG. 3).

  Further, when the pressure f2 of the hydraulic oil in the pipe line 206a reaches the cracking pressure P3 (P3> P2) of the control valve 4 constituting a part of the resistance valve 2, the direction switching valve 202 moves to the piston rod side oil chamber 104b. The control valve 4 that prohibits the entry of the hydraulic oil gradually opens and operates to the piston rod side oil chamber 104b via the pipelines 206a and 206b connecting the direction switching valve 202 and the piston rod side oil chamber 104b. The supply of oil is started, and the retracting operation of the piston rod 104c of the double-acting hydraulic cylinder 104, that is, the operation for swinging the boom 103 downward is continued smoothly (section D in FIG. 3).

More precisely, the contraction operation of the piston rod 104c is started, as shown in FIG. 3, when the pressure f2 of the hydraulic oil in the pipe line 206a is a part of the counter balance valve 204. This is the time when the cracking pressure P2 is reached.
At this stage, the control valve 4 constituting a part of the resistance valve 2 is not opened, but a strong external force is acting on the piston rod 104c that supports the long boom 103. Even when the hydraulic oil is not supplied, when the control valve 207 constituting a part of the counter balance valve 204 starts to open and the discharge of the hydraulic oil from the cylinder bottom side oil chamber 104a starts to be permitted, the piston rod 104c The contraction operation is started at the minute speed f3, and the tip of the boom 103 starts to descend at the minute moving speed (section C in FIG. 3).
At this time, since the control valve 207 is slowly opened, at least immediately after the hydraulic oil pressure f2 in the pipe line 206a reaches the cracking pressure P2 of the control valve 207, the control valve 207 moves to the piston rod 104c. A strong back pressure is applied, and even if a heavy object is suspended by the boom 103, the piston rod 104c does not degenerate instantaneously (section C in FIG. 3). ).

  Thereafter, when the pressure f2 of the hydraulic oil in the pipe line 206a reaches the cracking pressure P3 of the control valve 4 constituting a part of the resistance valve 2, the pipe line 206a connecting the direction switching valve 202 and the piston rod side oil chamber 104b. , 206b is started to supply the hydraulic oil to the piston rod side oil chamber 104b, and the pressure f4 of the hydraulic oil in the pipe line 206b, that is, the pressure f4 of the hydraulic oil in the piston rod side oil chamber 104b gradually increases. As described above, a strong back pressure is still applied from the control valve 207 to the piston rod 104c at this stage, so that in addition to the load from the boom 103, the pipes 206a, Even if the pressure of the hydraulic oil supplied via 206b starts to act in an overlapping manner, the piston rod 104c does not degenerate instantaneously, and Moving speed f3 degeneracy direction Tonroddo 104c would smoothly increase the street, exponential rise, shown in Figure 3 (section D in FIG. 3).

As described above, since it is necessary to allow the hydraulic oil to be discharged from the cylinder bottom side oil chamber 104a and then to start supplying the hydraulic oil to the piston rod side oil chamber 104b, a part of the resistance valve 2 is configured. Although it is an essential requirement that the cracking pressure P3 of the control valve 4 be set higher than the cracking pressure P2 of the control valve 207 constituting a part of the counter balance valve 204, the control constituting a part of the counter balance valve 204 is required. As shown in FIG. 4, the valve 207 is configured to change the movement stroke of the spool substantially linearly in accordance with the increase of the pilot pressure, and to increase the opening area exponentially in accordance with the movement stroke. Therefore, a period during which it is guaranteed that a sufficient back pressure is applied from the control valve 207 to the piston rod 104c, that is, the piston rod 104c is applied to the piston rod 104c. Within the time inadvertently piston rod 104c even if the load fluctuation occurs to is guaranteed not to degenerate, it is desirable to start the supply of the operating oil to the piston rod side oil chamber 104b.
For this reason, in this embodiment, as shown in FIG. 4, the opening area of the control valve 207 is small, and the control is performed at a relatively low rate of increase according to the increase in the pressure of the hydraulic oil in the conduit 206a. The cracking pressure P3 of the control valve 4 is set within a pilot pressure range in which the opening area of the valve 207 increases.

  Thereby, it becomes possible to completely prevent the unnatural degeneration of the piston rod 104c at the time when the pressure of the hydraulic oil from the pipe line 206b starts to act on the piston rod 104c in addition to the load from the boom 103. (Transition process from section C to section D in FIG. 3).

  As described above, after allowing the hydraulic oil to be discharged from the cylinder bottom side oil chamber 104a, the supply of the hydraulic oil to the piston rod side oil chamber 104b is started and the hydraulic oil in the cylinder bottom side oil chamber 104a is started. In addition to preventing compression, the supply of hydraulic oil to the piston rod side oil chamber 104b is started within a period in which sufficient back pressure is applied from the control valve 207 to the piston rod 104c, and the piston accompanying the load fluctuation By preventing unnatural degeneration of the rod 104c, it is possible to reliably prevent the bending of the boom 103 and the hunting phenomenon at the tip of the boom 103 that occur at the start of the switching operation for swinging the boom 103 downward. As shown in FIG. 3, the moving speed f3 of the piston rod 104c in the retracting direction can be increased smoothly with an exponential rise. That (C in FIG. 3, D section).

  Next, it is a part of the resistance valve so that the response time of the opening operation of the control valve constituting a part of the resistance valve is longer than the response time of the opening operation of the control valve constituting a part of the counter balance valve. An embodiment that achieves the same object by specifying the configuration of the control valve will be briefly described.

  Since the configuration of the boom hoisting hydraulic circuit 1 is the same as that of FIG. 1, description of the circuit is omitted, and the configuration of the resistance valve 2 ′ used in place of the resistance valve 2 of FIG. This will be described with reference to FIG.

  As shown in FIG. 5, the resistance valve 2 ′ allows the hydraulic oil to return from the piston rod side oil chamber 104 b to the direction switching valve 202 and allows the hydraulic oil to flow from the direction switching valve 202 to the piston rod side oil chamber 104 b. A check valve 3 ′ that prohibits entry and a control valve 4 ′ that is provided in parallel with the check valve 3 ′ and that is controlled to open and close using the hydraulic oil pressure in the pipeline 206a (detection position P) as a pilot pressure. The

  As described above, the throttle valve 5 'provided in parallel with these is not an essential component. Further, since the structure of the check valve 3 'is already known, a detailed description thereof will be omitted.

  As shown in FIG. 5, the main part of the control valve 4 ′ constituting a part of the resistance valve 2 ′ includes a spool 9 in which the outer periphery of the tip is superposed on the sealing part 8 of the casing 7, and an internal fit in the spool 9 The small-diameter piston 10 and the spool 9 are closed between the spool 9 and the small-diameter piston 10 against the pressure of the hydraulic oil supplied from the direction switching valve 202 (from left to right in FIG. 5). And the oil passages 13 and 14 that cross the blind hole 12 formed in the center of the front end surface of the spool 9 and pass through the inside of the front end of the spool 9 in the radial direction. In addition, the throttle portion 15 is provided in communication with the inner space 16 of the spool 9 functioning as a damper chamber and the blind hole 12.

  When the resistance valve 2 ′ having such a configuration is used instead of the resistance valve 2 of FIG. 1, the counter balance valve 204 is used to return the hydraulic oil in the cylinder bottom side oil chamber 104b as shown in FIG. When the direction switching valve 202 is shifted from the neutral position in FIG. 1 to the right side while keeping the state that caused the boom 103 to be prohibited, the direction switching valve 202 gradually increases according to the operation amount of the direction switching valve 202 as described above. The hydraulic oil sent from the hydraulic pump 201 starts to be supplied to the pipe line 206a via the direction switching valve 202.

  This hydraulic oil enters the port 17 of the control valve 4 ′ constituting a part of the resistance valve 2 ′. However, at the initial stage when the supply of the hydraulic oil starts, the pressure of the hydraulic oil in the internal space 16 is increased. Since the pressure of the hydraulic oil in the port 17 is equal and the force by which the hydraulic oil in the port 17 presses the front end surface of the spool 9 is smaller than the urging force of the spring 11, the spool 9 does not move.

  When the pressure of the hydraulic oil in the port 17 rises and exceeds the biasing force of the spring 11, the pressure receiving area of the hydraulic oil in the internal space 16 of the spool 9 is smaller than the pressure receiving area of the hydraulic oil on the port 17 side (spool 9), the hydraulic oil pressure in the internal space 16 exceeds the pressure of the hydraulic oil on the port 17 side, and the hydraulic oil in the internal space 16 flows out to the port 17 side. Moves in the valve opening direction (direction from right to left in FIG. 5).

As described above, in the configuration example shown in FIG. 5, in order for the spool 9 to move in the opening direction beyond the polymerization amount S, the hydraulic oil in the internal space 16 is equivalent to the volume of the polymerization amount S. Therefore, it is necessary to pass through the throttle portion 15 and discharge to the port 17 side.
Therefore, if the polymerization amount S, the hole diameter of the throttle portion 15, the pressure receiving area on the port 17 side and the pressure receiving area on the small diameter piston 10 side, and the spring constant of the spring 11 are appropriately set, a part of the counter balance valve 204 is configured. Even if the valve opening pressure of the control valve 4 ′ is set lower than the opening operation start pressure of the control valve 207, the response time required for the opening operation of the control valve 4 ′ is larger than the response time required for the opening operation of the control valve 207. Can be long.

  Therefore, as a result, similar to the case of the first embodiment, the control valve 207 constituting a part of the counter balance valve 204 is opened in advance to discharge the hydraulic oil from the cylinder bottom side oil chamber 104a. It is possible to start supplying the hydraulic oil to the piston rod side oil chamber 104b after allowing it, and this causes the operation in the cylinder bottom side oil chamber 104a that occurs when the boom 103 is swung downward. Oil compression can be prevented, and inadvertent bending of the boom 103 and hunting phenomenon at the tip of the boom 103 can be reliably prevented.

  Further, when such a configuration is applied, the volume of the internal space 16 of the spool 9 functioning as a damper chamber and the amount of polymerization S between the outer peripheral portion of the spool 9 and the sealing portion 8 of the casing 7 are various conditions. By designing appropriately and optimizing the response time required for the opening operation of the control valve 4 ′, in the same manner as described above, within a period in which sufficient back pressure is applied from the control valve 207 to the piston rod 104c. It is possible to start the supply of hydraulic oil to the piston rod side oil chamber 104b to prevent unnatural degeneration of the piston rod 104c due to load fluctuation.

  In this embodiment, the response time of the control valve 207 is based on the point in time when hydraulic fluid having a pressure corresponding to the opening operation start pressure P1 of the control valve 207 constituting a part of the counter balance valve 204 starts to be supplied to the pipe line 206a. In the above description, the response time of the control valve 4 ′ is delayed. However, it is not always necessary that the control valve 207 and the control valve 4 ′ are simultaneously opened or started for the opening operation. 5 can be applied in combination with the timing adjustment using the setting of the cracking pressure of the control valve 4 and the cracking pressure of the control valve 207 described in the above, and the operation in the pipe 206a is finally performed. The oil pressure, that is, the pilot pressure used for opening / closing control of the control valve 207 constituting a part of the counter balance valve 204 reaches the cracking pressure of the control valve 207. During in, if even prohibiting the entry of hydraulic fluid from the directional control valve 202 to the piston rod side oil chamber 104b, regardless the configuration of the hardware.

  In the first embodiment and the second embodiment, an example in which the boom 103 is driven by one double-acting hydraulic cylinder has been described. However, even when the boom 103 is driven by two or more double-acting hydraulic cylinders, Similar technical means can be applied.

It is a circuit diagram showing the composition of the hydraulic circuit for boom raising and lowering of one embodiment to which the present invention is applied. It is the structural example which provided the check valve for preventing cavitation in addition to the resistance valve of the hydraulic circuit for boom raising and lowering of the embodiment. The operation amount f1 of the direction switching valve when operating in the direction of tilting the boom, the pressure f2 of hydraulic oil in the pipe line between the direction switching valve and the resistance valve, and the pipe between the resistance valve and the piston rod side oil chamber It is the diagram which showed the relationship between the pressure f4 of the hydraulic fluid in a path | route, and the moving speed f3 of the piston rod in the degeneracy direction. It is the diagram which showed the relationship between the pilot pressure which acts on the control valve which comprises some counter balance valves, the movement stroke of a spool, and opening area. FIG. 4 is a cross-sectional view showing an embodiment in which the response time of the opening operation of the control valve is adjusted to take the timing of discharging the hydraulic oil from the cylinder bottom side oil chamber and supplying the hydraulic oil to the piston rod side oil chamber. is there. It is the figure which simplified and showed an example of the mobile crane provided with the boom driven with a double acting hydraulic cylinder. It is the figure which showed the general structural example of the hydraulic circuit for boom raising / lowering for controlling the expansion-contraction operation | movement of the double acting hydraulic cylinder which raises / lowers a boom (conventional example). A diagram showing, in time series, the relationship between the operation amount f1 of the direction switching valve when operating in the direction of tilting the boom, the pressure f2 of the hydraulic oil in the piston rod side oil chamber, and the moving speed f3 of the piston rod in the retracting direction. (Conventional example).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Boom raising / lowering hydraulic circuit 2 Resistance valve 2 'Resistance valve 3 Check valve 3' Check valve 4 Control valve 4 'Control valve 5 Throttle valve 6' Throttle valve 6 Check valve 7 Casing 8 Sealing part 9 Spool 10 Small diameter piston 11 Spring 12 Blind holes 13, 14 Oil passage 15 Restriction section 16 Internal space (damper chamber)
17, 18 Port 100 Mobile crane 101 Vehicle section 102 Revolving barrel 103 Boom 104 Double acting hydraulic cylinder 104a Cylinder bottom side oil chamber 104b Piston rod side oil chamber 104c Piston rod 105 Outrigger 200 Boom raising / lowering hydraulic circuit (conventional example)
201 Hydraulic pump 202 Direction switching valve 203 Pipe line 204 connecting the direction switching valve and the cylinder bottom side oil chamber Counter balance valve 205 Check valve 206 constituting a part of the counter balance valve Connecting the direction switching valve and the piston rod side oil chamber Pipe line 206a A pipe line 206b between the direction switching valve and the resistance valve A pipe line 207 between the resistance valve and the piston rod side oil chamber A control valve 208 constituting a part of the counterbalance valve A main relief valve 209 A port relief valve 210 Shuttle valve 211 Pressure compensation valve 212 Tank P Pilot pressure detection position P1 Opening operation start pressure P2 Cracking pressure P3 of the control valve constituting a part of the counter balance valve Cracking pressure f1 of the control valve constituting a part of the resistance valve Valve operation amount f2 Actuation in the pipeline between the direction switching valve and the resistance valve Pressure S polymerization amount of the hydraulic fluid in the line between the pressure f3 piston traveling speed f4 resistance valve rod and the piston rod side oil chamber

Claims (3)

A direction switching valve that selectively supplies hydraulic oil to the cylinder bottom side oil chamber and the piston rod side oil chamber of the double acting hydraulic cylinder that raises and lowers the boom;
A check valve provided on a pipe line connecting the direction switching valve and the cylinder bottom side oil chamber, and prohibiting return of hydraulic oil from the cylinder bottom side oil chamber to the direction switching valve, and in parallel with the check valve And a boom raising and lowering hydraulic circuit comprising a counterbalance valve provided with a control valve that is controlled to open and close using the pressure of hydraulic oil in a pipe line connecting the direction switching valve and the piston rod side oil chamber as a pilot pressure. Because
At least the pilot pressure reaches the cracking pressure of the control valve at a position closer to the piston rod side oil chamber than the detection position of the pilot pressure on a pipe line connecting the direction switching valve and the piston rod side oil chamber. A boom raising / lowering hydraulic circuit comprising a resistance valve that prohibits the hydraulic oil from entering the piston rod side oil chamber from the direction switching valve until the time until.   The resistance valve includes a check valve that prohibits the hydraulic oil from entering the piston rod side oil chamber from the direction switching valve, and a control valve that is provided in parallel with the check valve and controlled to be opened and closed by the pilot pressure. 2. The boom hoisting hydraulic circuit according to claim 1, wherein a cracking pressure of the control valve is set higher than a cracking pressure of the control valve.   The resistance valve includes a check valve that prohibits the hydraulic oil from entering the piston rod side oil chamber from the direction switching valve, and a control valve that is provided in parallel with the check valve and controlled to be opened and closed by the pilot pressure. 2. The boom hoisting hydraulic circuit according to claim 1, wherein a response time of the opening operation of the control valve is longer than a response time of the opening operation of the control valve.

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