JPH0765323B2 - Shovel loader boom and bucket controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boom and bucket control device for a shovel loader, and more specifically, to automatically adjust a bucket to maintain a horizontal posture when the boom is raised and lowered. The present invention relates to a boom and bucket control device equipped with a self-leveling valve.

(Prior Art) In a shovel loader, as a hydraulic automatic leveling device that automatically tilts the bucket so as to maintain the horizontal attitude of the bucket when the boom is raised, for example, U.S. Pat. FIG. 3 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 which functions to bypass the entire amount of hydraulic oil from the lift cylinder directional control valve 51 to the rod side oil chamber of the lift cylinder 57 when it descends by servo means.

Therefore, when the lift cylinder directional control valve 51 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 diversion valve 55 and then the dump cylinder 58 moves. While sending it to the bottom oil chamber, the remaining oil is returned to the tank 59 via the lift cylinder directional control valve 51 to tilt the bucket in the forward tilt direction according to the lift amount and keep the bucket horizontal. To do. On the other hand, when the lift cylinder directional control valve 51 is switched to the lower side, it is supplied only to the rod-side oil chamber of the lift cylinder 57 via the second position b of the flow dividing valve 55 and not to the dump cylinder 58 side. . That is, the automatic adjusting device disclosed in the U.S. Pat.

Therefore, the applicant of the present invention has proposed a control device (hereinafter referred to as a prior invention) improved so that the bucket can be horizontally adjusted not only when the boom is raised but also when the boom is lowered (Japanese Patent Application No. 62- 327643 specification and drawings). This prior invention is constructed as shown in FIG. 4, and when the lift cylinder directional control valve 10 is switched to the lowered position c,
The hydraulic oil discharged from the hydraulic pump 7 is sent to the rod-side oil chamber of the lift cylinder 4 via the pipe 16, the switching valve 19 of the self-leveling valve 17, and the bypass pipe 25, and the boom descends. The discharge oil of the bottom side oil chamber of the lift cylinder 4 passes through the pipe line 15 and the flow dividing valve of the bottom side circuit.
30 and the flow is diverted at a predetermined ratio here, and the diverted oil on the adjustment outlet side is supplied from the pipe 35 to the check valve 34 and the pipe 28.
The bucket is tilted backward by being sent to the rod-side oil chamber of the dump cylinder 6 via. That is, the bucket is configured to be automatically leveled while descending. The flow dividing valve 30 is of a type in which when one flow stops, the other flow also stops.

(Problems to be Solved by the Invention) In the case of the above-mentioned prior invention, the self-leveling valve 17 sets the pressure in the supply circuit of the hydraulic oil sent from the lift cylinder 4 to the dump cylinder 6 for horizontal adjustment to a set value. Is provided with a relief valve 33, and the control pressure of the relief valve 33 is taken from the supply circuit. However, in the case of a model with a large rated load, the pressure difference generated between the lift cylinder 4 and the dump cylinder 6 under load and without load may be large, and the bucket horizontal adjustment action may not be performed during boom lowering.

That is, in the case of a model having a large rated load, the pressure in the rod-side oil chamber of the dump cylinder 6 increases when the bucket is loaded with soil or the like. When the pressure is higher than the set pressure of the relief valve 33 incorporated in the self-leveling valve 17, the oil discharged from the bottom side oil chamber of the lift cylinder 4 passes through the flow dividing valve 30 and the dump cylinder when the boom descends. As a result of returning to the suction side of the hydraulic pump 7 through the relief valve 33 while flowing into the rod-side oil chamber 6, the horizontal adjustment action is not performed.

In order to avoid such a problem, the set pressure of the relief valve 33 on the self-leveling valve 17 side is set to, for example, the main relief valve 12a incorporated on the control valve 12 side.
If the dump cylinder 6 reaches the stroke end before the lift cylinder 4 when the boom is lowered with no load, the main relief valve 12a will be relieved. The set pressure is reached before the valve 33. This is because the bottom side oil chamber of the lift cylinder 4 that exerts pilot pressure on the relief valve 33 has a piston rod area larger than that of the rod side oil chamber of the lift cylinder 4 that exerts pilot pressure on the main relief valve 12a. This is because the pressure is large and therefore the pressure is low. As a result, the hydraulic oil from the hydraulic pump 7 drains to the tank 8, and the lowering operation of the lift cylinder 4 is stopped.

That is, in the invention of the prior application, there is an upper limit to the setting of the valve opening pressure of the relief valve 33, and as a result, the model with a large rated load must sacrifice the leveling action of the bucket during heavy load. Is.

Therefore, in view of the above problems, the present invention enables horizontal adjustment of the bucket regardless of the load when the boom is lowered, and the lift cylinder lowering operation can be continued without obstacle even after the stroke end of the dump cylinder. It is an object of the present invention to provide a boom control device for an excavator loader that can be used.

(Means for Solving the Problems) The present invention is configured as follows to solve the above problems.

The boom and bucket control device of a shovel loader includes a self-leveling valve downstream of a control valve that includes a directional control valve for a lift cylinder and a directional control valve for a dump cylinder in the form of a series circuit. Then, when the boom is raised or lowered, the hydraulic oil sent from the lift cylinder is split into a regulated flow rate and a surplus flow rate at a predetermined ratio by the flow dividing valve of the self-leveling valve, and the adjusted flow dividing oil is sent to the dump cylinder to cause the bucket to flow. It enables automatic leveling of. Therefore, the self-leveling valve is provided with a relief valve for boom lowering which holds the pressure of the rod-side oil chamber at a set value when the dump cylinder is horizontally adjusted, and this relief valve is provided on the rod side of the lift cylinder. It is configured to be controlled by the pressure of the circuit.

(Operation) According to the above configuration, when the direction switching valve for the lift cylinder is switched to the lower side, the hydraulic oil from the hydraulic pump is sent to the rod side oil chamber of the lift cylinder, and the hydraulic oil of the bottom side oil chamber is also sent. Is partially sent to the rod-side oil chamber of the dump cylinder by the shunt valve, and the rest is returned to the tank. That is, the boom is lowered, and the leveling operation of the bucket is performed in association with the lowering operation. At this time,
Since the relief valve for holding the pressure in the rod side oil chamber of the dump cylinder is controlled by the pressure in the rod side circuit of the lift cylinder, it can be set higher than the pressure in the rod side oil chamber of the dump cylinder. Therefore, even in the heavy load state, the bucket is automatically leveled.

In addition, even if the dump cylinder reaches the stroke end before the lift cylinder when the boom is lowered under no load, the relief valve of the self-leveling valve can be opened before the main relief valve. The descending motion of is continued without any trouble.

(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 an embodiment of the control device of the present invention. The hydraulic fluid pumped up and discharged from the tank 8 by the hydraulic pump 7 is used as a directional switching valve 9 for a dump cylinder, a directional switching valve 10 for a lift cylinder, and an earth auger used for digging work, for example. The flow direction is controlled by a cargo control valve 12 which includes a direct switching valve 11 for attachment as a series circuit. In this embodiment, the directional control valves are arranged in the order of the dump cylinder, the lift cylinder, and the attachment from the upstream side to the downstream side, but the arrangement is not limited to this.

On the other hand, the directional control valve 9 for the dump cylinder is an open center type three-position type, has a forward tilt position c, a neutral position b, and a rear tilt position a, and is connected to the dump cylinder 6 by the pipe lines 13 and 14. It is connected.

Further, the directional control valve 10 for the lift cylinder is an open center type four-position type and has a lift position a, a neutral position b,
It has a descending position c and a float position d, and is connected to the lift cylinder 4 by pipelines 15 and 16.

A self-leveling valve 17 for automatic horizontal adjustment of the bucket 5 is incorporated in a circuit connecting the control valve 12 and the lift cylinder 4 and the dump cylinder 6, which are downstream actuators. In this embodiment, it is carried out both when the boom is raised and when the boom is lowered. For boom raising, the diversion valve 18 and the two switching valves 19, 20 are provided in the rod side circuit of the lift cylinder 4. It is configured to include a pilot operated relief valve 21 and a check valve 22. Also, for lowering the boom, a shunt valve is provided in the bottom side circuit of the lift cylinder 4.
30, a switching valve 31, 32, a pilot operated relief valve 33, and a check valve 34.

The rod-side circuit implemented for raising the boom will be described more specifically. The flow dividing valve 18 has its inlet connected to the rod-side oil chamber of the lift cylinder 4 and its adjustment outlet connected to a pipe 13 communicating with the bottom-side oil chamber of the dump cylinder 6 via a pipe 23. The surplus outlet is incorporated so as to communicate with the directional control valve 10 for the lift cylinder, and the structure is such that when one flow stops, the other flow also stops. 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. Thus the shunt valve 18
The switching valve 19 inserted in parallel to the valve is controlled by the rod-side oil chamber pressure of the dump cylinder 6 acting on the open side via the pilot line 26 and the bottom-side oil chamber pressure of the lift cylinder 4 acting via the pilot line 27. The opening and closing are controlled, and when the both pressures act together or do not act together, they are held in the open position by a spring. Further, the other one switching valve 20 connects the pipe line 14 that connects the rod-side oil chamber of the dump cylinder 6 and the dump cylinder directional switching valve 9 to the surplus outlet side of the diversion valve 18. It is incorporated in the pipe line 28, is always kept in the closed position, and can be switched to the open position by the pressure on the adjusted outlet side of the flow dividing valve 18 acting via the pilot line 29. The lift cylinder 4
The relief valve 21, which controls the maximum pressure in the bottom side oil chamber of the dump cylinder 6 during the ascending operation of the
It is designed to be released when the inflow side pressure acting via 21a, that is, the rod side oil chamber pressure when the lift cylinder 4 moves upward exceeds a set pressure.

Next, the bottom side circuit implemented for boom lowering will be described. Basically, it is the same as the above-described one for rising, and the flow dividing valve 30 has its inlet port communicating with the bottom side oil chamber of the lift cylinder 4 and its adjusting outlet port from the pipe line 35 in which the check valve 34 is inserted. Dump cylinder 6 via paths 28 and 14
Is connected to the rod-side oil chamber and the surplus outlet is connected to the lift cylinder directional control valve 10 so that when one flow stops, the other flow also stops. ing.

Therefore, the relief valve 33 that sets the pressure in the rod-side oil chamber of the dump cylinder 6 when the boom descends has the pressure in the rod-side oil chamber of the lift cylinder 4 acting via the pilot line 33a set to the control valve 12 side. It is designed to be opened when the set pressure of the built-in main relief valve 12a or a set pressure slightly lower than that is reached. Further, the diversion valve 30 is adjusted by the pressure on the surplus outlet side acting through the pilot line 37 and is adjusted to a conduit on the outlet side.
It has a structure that can be switched to a position where 35 is closed.

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. In this way the shunt valve 30
The switching valve 31 inserted in parallel with the bottom side oil chamber pressure of the dump cylinder 6 acting on the opening side via the pilot line 39 and the rod side oil chamber of the lift cylinder 4 acting on the closing side via the pilot line 40. Opening and closing are controlled by the pressure, and when the both pressures act together or do not act together, the spring holds the open position. In addition, another one switching valve 32
Is a shunt valve 18 in the rod side circuit of the lift cylinder 4.
A pipe line connecting the pipe line 23 leading to the adjustment outlet of the bottom pipe and the pipe line 15 leading to the surplus outlet of the flow dividing valve 30 in the bottom side circuit.
It is incorporated in the valve 41, is always held in the closed position, and is switched to the open position by the pressure on the adjusting outlet side of the flow dividing valve 30 acting via the pilot line 42.

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

(When the boom is raised) When the lift cylinder directional control valve 10 is switched to the raised position a, the hydraulic oil discharged from the hydraulic pump 7 reaches the switching valve 31 of the bottom side circuit of the self-leveling valve 17 through the pipe line 15. Since the switching valve 31 is held in the open position by the spring, the hydraulic oil is sent to the bottom side oil chamber of the lift cylinder 4 via the bypass pipe line 38, and the boom 3 rises. At this time, the pressure of the bottom side oil chamber acts on the switching valve 19 in the rod side circuit via the pilot line 27 to switch the switching valve 19 to the closed position, so that the operation sent from the rod side oil chamber of the lift cylinder 4 is performed. Oil shunt valve 18
Then, the flow is divided at a preset ratio to keep the angle of the bucket 5 constant.

Then, the split oil on the adjustment outlet side is sent from the pipe line 23 to the bottom side oil chamber of the dump cylinder 6 via the pipe line 13, 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 conduit 23 on the adjusting outlet side of the diversion valve 18 acts on the switching valve 20 via the pilot line 29 to switch the switching valve 20 to the open position.
The discharged oil sent from the rod-side oil chamber of the dump cylinder 6 merges with the excess oil from the excess outlet of the flow dividing valve 18 via the pipelines 14 and 28, and the pipeline 16 and the lift cylinder direction switching valve 10 are connected. After that, it returns to the tank 8.

When the dump cylinder 6 becomes overspeed due to the weight of the bucket 5 while the boom 3 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 4 The pressure in the oil chamber on the rod side drops to zero, and the pressure drop causes the pilot line
The pressure in 29 disappears and the switching valve 20 is switched to the closed position by the spring to shut off the flow in the pipeline 28, so that 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 in the oil chamber on the bottom side of the dump cylinder 6 is sufficiently increased, and when the pressure is increased, 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
Since the divided oil from the adjusting outlet side of the valve opens the relief valve 21 and returns to the tank 8 due to the pressure increase caused by the blocking of the oil flow in the pipes 23 and 13, the lift cylinder 4 continues the ascending operation. Can be done.

(During boom lowering) When the lift cylinder directional control valve 10 is switched to the lowered position c, the hydraulic fluid discharged from the hydraulic pump 7 reaches the rod side circuit switching valve 19 of the self-leveling valve 17 through the pipe line 16. At this time, since the switching valve 19 is held in the open position by the spring, the working oil is sent to the rod-side oil chamber of the lift cylinder 4 via the bypass conduit 25, and the boom 3 descends. At this time, the pressure in the rod side oil chamber acts on the switching valve 31 in the bottom side circuit via the pilot line 40 to switch the switching valve 31 to the closed position, so that the operation sent out from the bottom side oil chamber of the lift cylinder 4 is performed. The oil enters the flow dividing valve 30 from the pipe line 15 and is divided at a predetermined ratio as in the case of rising. Then, the split oil on the adjustment outlet side is supplied from the pipe 35 through the check valve 34 and the pipes 28, 14 to the rod-side oil chamber of the dump cylinder 6, and the bucket 5 is tilted rearward. That is, the bucket 5 descends and is automatically leveled according to the descending amount.

When the bucket is loaded with earth and sand or the like, the rod-side oil chamber pressure of the dump cylinder 6 becomes a considerably high pressure when the bucket is leveled due to the boom lowering operation, but the set pressure of the relief valve 33 is increased. Is set higher than that, that is, equal to or slightly lower than the main relief valve 12a on the control valve 12 side, the automatic leveling action of the bucket 5 can be performed without any trouble.

On the other hand, when the dump cylinder 6 reaches the stroke end before the lift cylinder 4 when the boom is descending in the no-load state, the hydraulic oil in the bottom side oil chamber of the lift cylinder 4 has no escape, and therefore The rod side pressure rises to the set pressure of the main relief valve 12a. At this time, the relief valve 33 is opened within the range of pressure acting through the pilot line 33a, that is, the pressure set by the main relief valve 12a, and the working oil is on the low pressure side in the tank 8 (actually, the suction side of the hydraulic pump 7). ), The lift cylinder 4 continues the lowering operation. That is, the boom can be lowered without any trouble.

That is, according to this embodiment, the bucket 5 can be automatically leveled both when the boom 3 is raised and when the boom 3 is lowered, and the boom 3 is raised and lowered at that time by the hydraulic pump 7. Since the hydraulic oil of No. 1 can be supplied to the lift cylinder 4 through the bypass pipe lines 25 or 38 without passing through the flow dividing valve 18 or 30, it is possible to raise and lower at the same high speed as in the case without the self-leveling valve 17. .

(When the bucket is tilted forward or backward) When the dump cylinder directional control valve 9 is switched to the forward tilt position c, the hydraulic oil from the hydraulic pump 7 passes through the pipe line 13 to the bottom side oil chamber of the dump cylinder 6. While being supplied, the working oil sent from the rod-side oil chamber is returned to the tank 8 via the pipe line 14 and the dump cylinder direction switching valve 9, and the bucket 5 is tilted forward. When the dump cylinder directional control valve 9 is switched to the rearwardly inclined position a, the flow of the hydraulic oil is opposite to the above, and the bucket 5 is rearwardly inclined. That is, when the dump cylinder directional control valve 9 is independently operated, the dump cylinder 6 is operated without using the self-leveling valve 17.

(When the boom is raised and the bucket is tilted forward) When the dump cylinder directional control valve 9 is switched to the forward tilt position c and the lift cylinder directional control valve 10 is switched to the raised position a, the hydraulic oil from the hydraulic pump 7 is discharged. It is supplied to the bottom side oil chamber of the dump cylinder 6 from the direction switching valve 9 via the pipe 13, and the bucket 5 is tilted forward. Then, the hydraulic oil sent from the rod side oil chamber of the dump cylinder 6 is sent to the dump cylinder directional switching valve 9 via the pipe line 14, and from this, the lift cylinder switching valve 10
Through the line 15 and the self-leveling valve 17 through the same route as in the above-mentioned single operation.
Is sent to the bottom side oil chamber, and the boom 3 rises. At this time, the switching valve 19 of the bypass line 25 in the rod side circuit acts in a direction in which the pressures of the rod side oil chamber of the dump cylinder 6 and the bottom side oil chamber of the lift cylinder 4 are opposite to each other via both pilot lines 26 and 27. However, since both the pressures are balanced with each other, the switching valve 19 is eventually held in the open position by the biasing force of the spring, so that the hydraulic oil sent from the rod-side oil chamber of the lift cylinder 4 is bypassed. From the pipe 25, the pipe 16 and the lift cylinder directional control valve 10 are returned to the tank 8.

(When boom is lowered + bucket is tilted backward) When the dump cylinder direction switching valve 9 is switched to the rearward tilt position a and the lift cylinder direction switching valve 10 is switched to the lower position c, the hydraulic oil from the hydraulic pump 7 is discharged. It is supplied to the rod side oil chamber of the dump cylinder 6 from the direction switching valve 9 through the pipe line 14, and the bucket 5 is tilted backward. Then, the hydraulic oil sent from the bottom side oil chamber of the dump cylinder 6 is sent to the dump cylinder directional switching valve 9 via the pipe line 13, and from this, the lift cylinder switching valve 10
Through the line 16 and the self-leveling valve 17 through the same route as in the above-described single operation.
Is sent to the rod side oil chamber, and the boom 3 descends. At this time, the switching valve 31 of the bypass line 38 in the bottom side circuit acts in a direction in which the pressures of the bottom side oil chamber of the dump cylinder 6 and the rod side oil chamber of the lift cylinder 4 are opposite to each other via the pilot lines 39, 40. However, since both the pressures balance each other, the switching valve 31 is eventually held in the open position by the urging force of the spring, so that the hydraulic oil sent from the bottom side oil chamber of the lift cylinder 4 is bypass pipe. Line 38 to pipe 15 and lift cylinder directional control valve
Return to tank 8 via 10.

In this embodiment, however, the hydraulic oil can be supplied to the dump cylinder 6 prior to the lift cylinder 4 when the boom 3 is moved up and down and the bucket 5 is tilted forward and backward as described above. Therefore, the operating speed is the same as that of the above-mentioned single operation. That is, since the bucket 5 can be dump-operated at the same speed as the single operation even during the simultaneous operation, the soil can be effectively removed from the bucket 5 when the soil is loaded on the truck.

(Effects of the Invention) As described in detail above, according to the present invention, the relief valve that controls the pressure of the rod side oil chamber of the dump cylinder is configured to be controlled by the pressure of the rod side oil chamber of the lift cylinder. , It is possible to set the relief valve set pressure as large as possible within the range of the main relief valve set pressure, which allows the lift cylinder to lift even if the dump cylinder reaches the stroke end before the lift cylinder when the boom is lowered. The lowering operation of the cylinder can be continued, and the bucket can be automatically leveled even under a heavy load condition. Therefore, the present invention is particularly effective in a vehicle having a large rated load.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a boom and bucket control device of the present invention, FIG. 2 is a schematic side view of a shovel loader, FIG. 3 is a hydraulic circuit diagram showing a conventional example, and FIG. It is a hydraulic circuit diagram which shows the control apparatus of invention. 3 …… Boom 4 …… Lift cylinder 5 …… Bucket 6 …… Dump cylinder 7 …… Hydraulic pump 9 …… Dump cylinder directional control valve 10 …… Lift cylinder directional control valve 12 …… Control valve 17 …… Self Leveling valve 18 …… Shunt valve 19 …… Switching valve 30 …… Shunt valve 31 …… Switching valve 33 …… Relief valve

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.
The hydraulic oil sent out from the lift cylinder when the boom is raised or lowered is split into a regulated flow rate and a surplus flow rate by the flow dividing valve of the self-leveling valve at a predetermined ratio, and the adjusted flow dividing oil is sent to the dump cylinder to In a shovel loader of a type capable of automatic horizontal adjustment, a relief valve for lowering a boom, which is provided in the self-leveling valve and holds a pressure in a rod-side oil chamber at a set value during horizontal adjustment of a dump cylinder, is lifted. A boom and bucket control device for a shovel loader configured to be controlled by the pressure of a rod side circuit in a cylinder.