JPH0749665B2 - Shovel loader boom lifting control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boom lift control device for a shovel loader, and more particularly to a self-leveling valve for automatically holding a bucket in a horizontal position when the boom is lifted. The present invention relates to a control device including.

(Prior Art) In a conventional shovel loader, the most common automatic leveling device that automatically tilts the bucket so as to maintain the horizontal position when the boom is raised and lowered is a mechanical type that uses a parallel link mechanism. Linkage devices are known. Since this linkage device includes a problem that the lifting mechanism part becomes large or large, a hydraulic automatic leveling device, specifically, a self-leveling valve adjusting device has been proposed as a solution to the problem. The method is disclosed in, for example, US Pat. No. 4,561,342 and the drawings. FIG. 6 is a circuit diagram of the hydraulic automatic leveling device disclosed in this U.S. Pat.

This includes a directional control valve 51 for lift cylinders, a directional control valve 52 for dump cylinders, and a directional control valve 53 for other attachments.
A self-leveling valve 56 including a shunt valve 55 with a servo is installed downstream of a control valve 54 including three directional control valves in the form of a series circuit. The shunt valve with a servo 55 is a lift cylinder. The first position a which functions to divert the oil discharged from the rod side oil chamber when the 57 is raised
And a second position b that functions to bypass the entire amount of hydraulic oil from the lift cylinder directional control valve 52 to the rod side oil chamber of the lift cylinder 57 when it descends by servo means.

That is, when the lift cylinder switching valve 52 is switched to the rising side, a part of the oil discharged from the rod-side oil chamber of the lift cylinder 57 passes through the first position a of the shunt valve 55 and reaches the bottom of the bucket cylinder 58. While the oil is sent to the side oil chamber, the remaining oil is returned to the tank 59 through the lift cylinder directional control valve 52 to tilt the bucket in the forward tilt direction in accordance with the lift amount and hold the bucket in a horizontal state. In addition, when the lift cylinder directional control valve 52 is switched to the lower side, the lift cylinder passes through the second position b of the flow dividing valve 55.
The oil is supplied to the oil chamber on the rod side of 57.

(Problems to be Solved by the Invention) In the system using the servo-type diversion valve 55 described above,
Since the same diversion valve 55 has two functions of the diversion function and the bypass function by switching between the position a and the second position b, the descending speed when the bucket descends becomes slow. I have a problem. That is, when the bucket is lowered, the flow rate of the working oil sent from the lift cylinder directional control valve 52 is limited by the “throttle” action of the flow dividing valve 55, so that the working speed of the lift cylinder 57 decreases. , The work efficiency will deteriorate.

In view of the above problems, it is an object of the present invention to increase the descending speed of the boom.

(Means for Solving Problems) According to the present invention for solving the above problems, a self-leveling valve is provided downstream of a control valve including a lift cylinder directional control valve and a dump cylinder directional control valve in the form of a series circuit. This self-leveling valve diversion valve diverts the oil discharged from the rod-side oil chamber of the lift cylinder into a regulated flow rate and a surplus flow rate at a predetermined ratio, and sends the regulated diversion oil to the bottom side of the dump cylinder. In a boom raising / lowering control device capable of automatically leveling a bucket, the inlet side of the diversion valve and the adjusting outlet side are connected by a bypass pipe, and a switching valve for opening and closing is provided in the bypass pipe. The gist is that the switching valve is held in the open position when the lift cylinder is lowered and is switched to the closed position when the lift cylinder is raised. To do.

(Operation) When the lift cylinder directional control valve is operated to the raised position, hydraulic oil from the hydraulic pump is sent to the bottom side oil chamber of the lift cylinder, and the bypass line switching valve is correspondingly moved to the closed position. Switching is activated. Therefore, the oil discharged from the rod-side oil chamber is sent to the bottom-side oil chamber of the dump cylinder at an adjusted flow rate preset by the flow dividing valve, and the surplus oil is returned to the tank. As a result, the bucket is tilted in the forward tilt direction by the amount corresponding to the amount of lift, and is held in the horizontal position.

On the other hand, when the lift cylinder directional control valve is operated to the lower side, the bypass line switching valve is held in the open position,
The hydraulic oil from the hydraulic pump is supplied to the rod side oil chamber of the lift cylinder through this bypass line. Therefore, the lowering speed of the lift cylinder in this case is not affected by the "throttle" of the shunt valve of the self-leveling valve at all, and thus is higher than in the conventional case.

(Example) Hereinafter, the Example of this invention is concretely described based on drawing. FIG. 2 shows an outline of the shovel loader, and the vehicle body 1
The boom 3 whose base end is supported by the pillar 2 to be pivotable up and down is moved up and down by the lift cylinder 4, and the bucket 5 attached to the tip of the boom 3 is moved by the dump cylinder 6. It is designed to be tilted in the front-back direction.

FIG. 1 shows a first embodiment of the control device of the present invention. The hydraulic oil pumped up from the tank 8 by the hydraulic pump 7 and discharged is used for a lift cylinder directional control valve 9, a dump cylinder directional control valve 10, for example, an attachment directional control such as an earth auger used for digging work. The flow direction is controlled by a control valve 12 including the valve 11 as a series circuit. This control valve 12
A self-leveling valve 13 is incorporated in a circuit connecting the lift cylinder 4 and the dump cylinder 6, which is a downstream actuator thereof. More specifically, the lift cylinder directional control valve 9 is an open center type four-position type, has an ascending position c, a neutral position b, a descending position a, and a float position d, and is provided with pipelines 14 and 15 for the lift cylinder. 4 is connected. Further, the dump cylinder directional control valve 10 is an open center type three-position type, has a forward tilted position a, a neutral position b, and a rearward tilted position c.
It is connected to the dump cylinder 6 by 7.

Therefore, the self-leveling valve 13 for automatically adjusting the level of the bucket 5 is the same as the diversion valve 18 in this embodiment.
It is configured to include two switching valves 19 and 20, a relief valve 21, and a check valve 22. The flow dividing valve 18 has its inflow port connected to the rod-side oil chamber of the lift cylinder 4, its adjusting outflow port connected to the pipe line 16 communicating with the bottom side oil chamber of the dump cylinder 6 via the pipe line 23, and The excess outlet is incorporated so as to communicate with the tank 8 via the lift cylinder directional control valve 9. The check valve 22 is inserted into the conduit 23, and the relief valve 21 keeps the set pressure. Further, the flow dividing valve 18 has a structure that can be switched to a position where the conduit 23 on the adjusting outlet side is closed by the pressure on the excessive outlet side acting through the pilot line 24.

Then, the inlet side and the surplus outlet side of the flow dividing valve 18 are connected by a bypass pipe 25, and the one switching valve 19 is inserted in the bypass pipe 25. This switching valve 19 is always held in the open position by a spring, and the pressure of the pipe line 15 acts on the open side via the pilot line 26, and the lift cylinder 4 acting via the pilot line 27 acts. It can be switched to the closed position by the pressure of the bottom side oil chamber. Further, the other one switching valve 20 is a pipe line 17 connecting the rod-side oil chamber of the dump cylinder 6 and the lift cylinder directional switching valve 9.
And a built-in conduit 28 that connects the excess flow outlet side of the flow dividing valve 18, is always held in the closed position, and is adjusted by the pressure on the adjusting flow outlet side of the flow dividing valve 18 acting via the pilot line 29. It can be switched to the open position.

The present embodiment is configured as described above, and its operation will be described below.

(When the boom is raised) When the lift cylinder direction switching valve 9 is switched to the raised position c, the hydraulic oil discharged from the hydraulic pump 7 is sent to the bottom side oil chamber of the lift cylinder 4 via the pipe line 14, and the boom 3 is moved. Be raised. At this time, the pressure in the bottom side oil chamber acts on the switching valve 19 of the bypass line 25 via the pilot line 27 to switch the switching valve 19 to the closed position, so that the oil discharged from the rod side oil chamber of the lift cylinder 4 is discharged. Enters the shunt valve 18 in the self-leveling valve 13 and is shunted at a preset ratio to keep the angle of the bucket 5 constant.

Then, the divided oil on the adjustment outlet side reaches the pipe line 16 from the pipe line 23, but at this time, one end of the pipe line 16 is blocked because the dump cylinder directional control valve 10 is in the neutral position and is blocked. It is sent to the bottom side oil chamber of the cylinder 6, and the bucket 6 is tilted forward. That is, the bucket 5 is automatically adjusted so as to maintain the horizontal posture in response to the rise of the boom 3.
At this time, the pressure in the pipe line 23 through which the split oil on the adjustment outlet side passes acts on the switching valve 20 via the pilot line 29, so that the switching valve 20 is switched to the open position. On the other hand, the split oil from the surplus outlet passes through the pipe line 15, returns to the tank 8 via the lift cylinder direction switching valve 9. Further, the oil in the rod-side oil chamber of the dump cylinder 6 is discharged through the pipe line 17, but one end of the pipe line 17 is blocked by the dump cylinder directional control valve 10 at the neutral position b. Therefore, the pipe 28 reaches the pipe 15 via the switching valve 20 which is switched to the open position as described above, and from there, the lift cylinder directional switching valve 9 is reached.
Return to tank 8 via.

If the dump cylinder 6 becomes overspeed due to the weight of the bucket 5 while the boom 5 is being raised, if the bottom side oil chamber of the dump cylinder 6 is about to cause a negative pressure state, the lift cylinder Since the pressure in the rod-side oil chamber of No. 4 drops to 0 and the pressure drop causes the pressure in the pilot line 29 to disappear, the switching valve 20 is switched to the closed position by the spring and shuts off the flow in the pipeline 28.
The discharge of oil from the rod-side oil chamber of the lift cylinder 4 is blocked. Therefore, the operation of the dump cylinder 6 is temporarily stopped until the pressure of the bottom side oil chamber of the dump cylinder 6 sufficiently rises, and when the pressure rises, the original operation is resumed.

If the dump cylinder 6 reaches the stroke end while the lift cylinder 4 is being lifted, the flow dividing valve 18
The split oil from the adjusting outlet side of the above returns to the tank 8 through the relief valve 21 as the oil flow in the pipes 23 and 16 is blocked.

(During boom lowering) When the lift cylinder direction switching valve 9 is switched to the lowered position a, the hydraulic oil discharged from the hydraulic pump 7 reaches the switching valve 19 of the self-leveling valve 13 via the pipe line 15. At this time, since the pressure in the pilot line 27 is 0, the same switching valve 19 passes through the spring and pilot line 26,
Since it receives the internal pressure and is held in the open position, the working oil is sent to the rod-side oil chamber of the lift cylinder 4 through the bypass conduit 25, and the boom 3 descends. On the other hand, the oil discharged from the bottom oil chamber of the lift cylinder 4 passes through the pipe line 14, returns to the tank 8 via the lift cylinder direction switching valve 9. That is,
When the bucket 5 descends, the hydraulic oil from the hydraulic pump 7 is sent to the rod-side oil chamber of the lift cylinder 4 via the bypass line 25, so that a high descending speed equivalent to the case without the self-leveling valve 13 is obtained. be able to.

In short, according to this embodiment, the bucket 5 can be automatically leveled by the self-leveling valve 13 when the boom is raised, and when the boom is raised and lowered, the bucket 5 is not passed through the diversion valve 18 but is passed through the bypass line 25. Since it is sent to the lift cylinder 4, it is possible to move up and down at the same high speed as when there is no self-leveling valve 13.

Next, another embodiment of the present invention will be described with reference to FIG. The above-described embodiment is an example in which the automatic leveling is performed only when the boom is raised, but the embodiment shown in FIG. 3 is such that the automatic leveling is performed not only when the boom is raised but also when the boom is lowered. is there. That is, in addition to the configuration shown in the above-described embodiment, the self-leveling valve 13 includes a diversion valve 30, two switching valves 31, 32, a relief valve 33, and a check valve 34 in the bottom side circuit of the lift cylinder 4. It is configured to include. Then, the flow dividing valve 30 has its inlet connected to the bottom-side oil chamber of the lift cylinder 4 by the pipe 35, and its adjusting outlet connected to the pipe 28 via the pipe 36 in which the check valve 34 is inserted. Further, the surplus outlet communicates with the pipe line 14 on the lift cylinder direction switching valve 9 side. In addition, pipeline
The relief valve 33 for keeping the pressure in 36 at the set pressure is
It is provided in a pipeline 43 connecting the pipeline 36 and the suction pipeline 7a of the hydraulic pump 7. Further, the flow dividing valve 30 has a structure that can be switched to a position where the conduit 36 on the adjusting outlet side is closed by the pressure on the excessive outlet side acting through the pilot line 37.

Then, the inlet side and the surplus outlet side of the flow dividing valve 30 are connected by a bypass pipe 38, and the one switching valve 31 is inserted in the bypass pipe 38. This switching valve 31 is always held in the open position by a spring, and the pressure of the pipe line 14 acts on the open side via the pilot line 39, and the pressure of the lift cylinder 4 acting via the pilot line 40. It can be switched to the closed position by the pressure of the rod side oil chamber. Further, the other one switching valve 32 includes a conduit 23 on the adjusting outlet side of the diversion valve 18 in the rod side circuit of the lift cylinder 4 and a conduit 14 on the adjusting outlet side of the diversion valve 30 in the bottom circuit. Is provided in a pipe line 41 for connecting the valve, is always held in a closed position, and can be switched to an open position by the pressure on the side of the adjusted outlet of the flow dividing valve 30 acting via the pilot line.

This embodiment is configured as described above. Therefore, when the lift cylinder directional control valve 9 is switched to the raised position c in order to raise the boom 3, the hydraulic oil discharged from the hydraulic pump 7 is supplied to the pipe line 14. And reaches the switching valve 31 of the bottom side circuit in the self-leveling valve 13. At this time, since the pressure in the pilot line 40 is 0, the switching valve 30 receives the pressure in the pipeline 14 via the spring and the pilot line 39, and is held in the open position, so that the hydraulic oil flows from the bypass pipeline 38. It is sent to the bottom side oil chamber of the lift cylinder 4 through the pipe line 35, and the boom 3 rises.

At this time, the pressure of the bottom side oil chamber passes through the pilot line 27 and the switching valve 19 of the bypass line 25 in the rod side circuit.
To switch the switching valve 19 to the closed position, the oil discharged from the rod-side oil chamber of the lift cylinder 4 enters the flow dividing valve 18 of the self-leveling valve 13 and is divided at a predetermined ratio, and thereafter the above-mentioned The bucket 5 is automatically leveled in the same manner as in the embodiment. At this time, the oil in the rod-side oil chamber of the lift cylinder 4 has a medium pressure for operating the bucket cylinder 6, and this acts in the direction of closing the switching valve 31 through the pilot line 40. Since the switching valve 31 receives not only the spring force in the opening direction but also the high pressure on the bottom side of the lift cylinder 4 through the pilot line 39, the switching valve 31 is held at the opening position.

On the other hand, when the lift cylinder direction switching valve 9 is switched to the lowered position a in order to lower the boom 3, the hydraulic fluid discharged from the hydraulic pump 7 passes through the same route as in the above-described embodiment, and the lift cylinder 4 is moved. Sent to the oil chamber on the rod side of the boom 3
However, the oil discharged from the bottom side oil chamber of the lift cylinder 4 passes through the pipe line 35, and the flow dividing valve 30 of the bottom side circuit 30
In the same manner as when going up, the split oil is split at a predetermined ratio in the same way as when rising, and the split oil on the adjustment outlet side is sent from the pipe line 36 to the rod side oil chamber of the dump cylinder 6 via the check valve 34 and the pipe line 17, and the bucket 5 Is tilted backwards. That is, the bucket 5 is automatically leveled while descending. The split oil on the excess outlet side passes through the pipe line 14, passes through the lift cylinder directional control valve 9, and returns to the tank 8. At this time, the switching valve
The pressure on the bottom side of the lift cylinder 4 acts on the 30 through the pilot line 27 in the closing direction, but at this time, the rod side oil chamber pressure higher than that acts on the opening direction through the pilot line 40. The switching valve 30 is held in the open position.

As described above, according to the embodiment shown in FIG.
It is possible to perform automatic leveling both when ascending and descending, and when the boom 3 is raised or lowered at that time, the hydraulic oil sent from the hydraulic pump 7 to the lift cylinder 4 is used to bypass the bypass pipe 38 or 25. Since it passes through, it can be performed at a high speed equivalent to the case without the self-leveling valve 13.

Next, still another embodiment of the present invention will be described with reference to FIG.

In this embodiment, a part of the internal circuit of the self-leveling valve 13 in the embodiment shown in FIG. 3 is modified. As shown in the drawing, the conduit for the switching valve 20 connected to the conduit 17 leading to the rod-side oil chamber of the dump cylinder 6.
One end of 28 is connected to the outlet side of the relief valve 33 of the bottom side circuit in the lift cylinder 4, and also the switching valve 32 connected to the pipe line 16 leading to the bottom side oil chamber of the dump cylinder 6.
One end of a pipeline 41 for use in connection with the outlet side of the relief valve 21 of the rod side circuit in the lift cylinder 4,
The other structure is completely the same as that of the embodiment shown in FIG.

Therefore, according to the embodiment shown in FIG. 4, when the boom 3 is moved up and down and the bucket 5 is tilted forward and backward at the same time, only when "ascending / backward leaning" and "downward / forward leaning" are simultaneously operated. Of course, the automatic leveling can be canceled even at the time of simultaneous operation of "up / forward tilt" and "down / back tilt".

That is, when the "lifting / forward leaning" is simultaneously performed, that is, when the lift cylinder directional control valve 9 is moved to the raised position c and the dump cylinder directional control valve 10 is moved to the forward leaning position a, the lift cylinder 4 is moved. The oil discharged from the rod-side oil chamber is divided by the flow dividing valve 18 at a predetermined ratio, but the divided oil on one adjustment outlet side reaches the pipe 16 via the pipe 23 and the surplus of the other. The split oil on the outlet side is sent from the pipe 15 through the lift cylinder directional control valve 9 to the dump cylinder directional control valve 10, and then reaches the pipe 16. As a result, both split oils merge in the pipe 16. Then, it is sent to the bottom side oil chamber of the dump cylinder 6. In other words, the total amount of oil discharged from the rod-side oil chamber of the lift cylinder 4 is the dump cylinder 6.
Since it is sent to the bottom side oil chamber, the dump cylinder 6 operates with a stroke larger than that during automatic horizontal adjustment, and the bucket 5 can be tilted forward.

Further, when the "downward / backward tilt" simultaneous operation is performed, that is, when the lift cylinder direction switching valve 9 is operated to the down position a and the dump cylinder direction switching valve 10 is operated to the rearward tilt position c, the oil flow direction is changed. Is just the opposite of the above, and the operation itself is the same as when "up / forward leaning". That is, the entire amount of oil discharged from the bottom side oil chamber of the lift cylinder 4 is sent to the rod side oil chamber of the dump cylinder 6, so the dump cylinder 6 operates with a stroke larger than that during automatic leveling, and the bucket 5 You can lean back.

Then, the ascending / descending speed of the boom 3 during the above-described operation is
The hydraulic oil from the hydraulic pump 7 is the bypass line 38 or 25.
Since it is sent to the lift cylinder 4 through, it becomes a high speed that is not affected by the self-leveling valve 13.
Further, the automatic leveling action of the bucket 5 and the ascending / descending speed of the boom 3 during the ascending / descending operation of independently operating the normal lift cylinder directional control valve 9 are the same as those in the above-described embodiment.

In each of the embodiments shown in FIGS. 1, 3, and 4, the oil is routed through the relief valves 21 and 33 to the suction side of the hydraulic pump or the return side to the tank 8. ,
As shown in FIG. 5, this may be changed to a hydraulic circuit for sending to the pump port of the third attachment direction switching valve 11 of the control valve 12. With such a hydraulic circuit, it becomes possible to operate the actuator of the attachment, for example, the hydraulic motor for rotating the earth auger, at the time of simultaneous operation.

(Effects of the Invention) As described in detail above, according to the present invention, in the boom up / down control device for a shovel loader, not only the work of raising the boom but also the work of lowering the boom can be performed at the same high speed as when there is no self-leveling valve. Since it can be performed, it is very useful for improving work efficiency.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a boom raising / lowering control device of the present invention, FIG. 2 is a schematic side view of a shovel loader, and FIG.
FIG. 4 is a hydraulic circuit diagram showing another embodiment of the present invention, FIG. 4 is a hydraulic circuit diagram showing yet another embodiment of the present invention, and FIG. 5 is a modification example of an oil return circuit via a relief valve. The hydraulic circuit diagram shown in FIG. 6 is a hydraulic circuit diagram showing a conventional example. 3 ... Boom, 4 ... Lift cylinder 5 ... Bucket, 6 ... Dump cylinder 7 ... Hydraulic pump 9 ... Lift cylinder directional control valve 10 ... Dump cylinder directional control valve 12 ... Control valve 13 ... … Self-leveling valve 18 …… Shunt valve, 19 …… Switching valve 25 …… Bypass line, 30 …… Shunt valve 31 …… Switching valve, 38 …… Bypass line

Claims (1)

[Claims] 1. A self-leveling valve is provided downstream of a control valve including a directional control valve for a lift cylinder and a directional control valve for a dump cylinder in the form of a series circuit, and a shunt valve of the self-leveling valve is provided on a rod side of the lift cylinder. In the boom lifting control device capable of automatically leveling the bucket by dividing the oil discharged from the oil chamber into an adjusted flow rate and a surplus flow rate at a predetermined ratio and sending the adjusted divided oil to the bottom side of the dump cylinder, While connecting the inlet side of the flow dividing valve and the adjusting outlet side by a bypass pipe line, a switching valve for opening and closing is provided in this bypass pipe line,
A boom raising / lowering control device for a shovel loader, wherein the switching valve is held in an open position when the lift cylinder is lowered and is switched to a closed position when the lift cylinder is raised.