JPS6365776B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to construction machines such as power shovels.

For example, as shown in FIG. 1, a power shovel includes a truck 2a, 2b driven by left and right hydraulic motors 1a, 1b, an upper rotating body 4 rotated by a hydraulic motor 3, and a rotating upper body 4. A boom 6 is pivotally attached to the boom 6 and is tilted by a boom cylinder 5, and an arm 8 is pivotably attached to the boom 6 and is pivoted by an arm cylinder 7.
A bucket cylinder 9 is pivotally connected to the arm 8.
It is equipped with a bucket 10 driven by. The main work of this power shovel is excavation work and crane work. This excavation work is
It consists of four operations: digging, lifting rotation, earth removal, and lowering rotation. The lifting and turning operation is an operation of lifting the bucket 10 from the excavation position onto the loading platform of a dump truck (not shown) that is stopped near the power shovel. 4 can be represented by the operation of rotating the hydraulic motor 3.
At this time, from the viewpoint of work efficiency, there is a demand that the boom 6 be raised quickly to the height of the loading platform of the dump truck, and from the viewpoint of safety, the upper revolving body 4 should be started slowly to avoid shock. That is, under the condition that the load pressure on the hydraulic motor 3 side is larger than the load pressure on the boom cylinder 5 side due to the large inertia of the upper revolving structure 4, a large amount of fluid is supplied to the boom cylinder 5, and the hydraulic motor There is a request to supply a small amount of fluid to 3. Further, the crane work described above involves hooking an extremely large heavy object (not shown) onto the tip of the bucket 10 and rotating at a slow speed while adjusting its height. This can be represented by an operation in which the upper revolving body 4 is rotated by the hydraulic motor 3. At this time, there is a demand for accurate speed control of the boom cylinder 5 and hydraulic motor 3, regardless of the magnitude of their loads, in order to easily align the heavy objects and from a safety standpoint. That is, under the condition that the load pressure on the boom cylinder 5 side is larger than the load pressure on the hydraulic motor 3 side that rotates at a very slow speed due to a heavy object, the hydraulic motor 3
There is a desire to ensure safety by accurately controlling the speeds of both the hydraulic motor 3 and the boom cylinder 5, without causing the speed of the boom cylinder 5 to become abnormally high due to the influence of the load pressure on the boom cylinder 5 side.

This invention was made in response to the above request.
In a construction machine such as a power shovel in which a boom is pivotally connected to a revolving structure, a first flow rate directional control valve with a load pressure sensing port that controls a hydraulic motor that rotates the revolving structure is connected to a variable pump via a pressure reducing type pressure compensation valve. A second flow rate directional control valve with a load pressure sensing port for controlling a boom cylinder that tilts the boom is connected to a line branching from between the variable pump and the pressure reducing type pressure compensation valve; , the maximum pressure between the fluid pressure in the spring chamber of the pressure reducing type pressure compensating valve and the fluid pressure in the load pressure sensing port of the second flow direction control valve is selected by the shuttle valve and transmitted to the spring chamber of the switching valve; , a line branching from between the variable pump and the reducing pressure compensating valve is connected to a pilot chamber of the switching valve;
When the pressing force generated by the fluid pressure acting on the pilot chamber is greater than the sum of the pressing force generated by the fluid pressure acting on the spring chamber and the spring force, the switching valve controls the variable pump. When the discharge rate control section is connected to the main line for fluid supply, and the pressing force of the pilot chamber is smaller than the sum of the pressing force of the fluid acting on the spring chamber and the spring force, the discharge rate control section of the variable pump By connecting it to the tank line for fluid discharge, if (load pressure on the hydraulic motor side) > (load pressure on the boom cylinder side), a large amount of fluid can be supplied to the boom cylinder. The hydraulic motor can operate at a slow speed when starting up and with accurate speed control during steady state, improving work efficiency and safety. ) < (load pressure on the boom cylinder side), the hydraulic motor and boom cylinder can each be accurately controlled in speed without being affected by other load pressures, improving work efficiency and safety. Furthermore, the variable pump does not discharge wasteful fluid and provides a new construction machine such as a power shovel without power loss.

EMBODIMENT OF THE INVENTION Hereinafter, this invention will be described in detail with reference to an embodiment of a power shovel shown in the drawings.

In FIG. 2, 21 is a boom pivotally connected to the revolving structure 22, 23 is an arm pivotally connected to the boom 21, 24 is a bucket pivotally connected to the arm 23,
25 is a boom cylinder that tilts the boom 21; 26 is an arm cylinder that swings the arm 23; 27 is a bucket cylinder that drives the bucket 24; 28 is a hydraulic motor that rotates the revolving body 22; 29 and 30 are Hydraulic motor for left and right travel,
Numerals 31 and 32 are valve units that control fluid to actuators such as the boom cylinders, and 33 is a pump unit that supplies fluid to the valve units 31 and 32.

The valve unit 31 includes a pressure reducing type pressure compensating valve 36.
, first flow rate directional control valves 37a, 37b, and second flow rate directional control valves 38a, 38b.

The first and second flow rate directional control valves 37a, 37
b, 38a, and 38b each have the functions of a directional control valve and a flow rate control valve, and furthermore, as shown in FIG. 3, they detect the pressure behind the flow rate adjustment section (not shown) via the feedback passage 41 at the switching position. Equipped with a load pressure sensing port d that can be used.

A first flow direction control valve 37 is connected to the secondary port 45 of the pressure reducing type pressure compensation valve 36 via a line 46.
The pump ports a and 37b are connected in parallel, and a main line 47 connected to the primary port 40 of the pressure reducing pressure compensation valve 36 is connected to each of the second flow rate directional control valves 38a and 38b via a line 48. Pump ports are connected in parallel.

The spring chamber of the pressure reducing type pressure compensation valve 36 includes a first
The maximum pressure among the detected pressures of each load pressure sensing port d of the flow direction control valves 37a and 37b is set to the shuttle valve 5.
0 is selected and transmitted, and the pressure compensation valve 36 is actuated to compensate for the pressure of the first flow direction control valve 37a or 37b having the maximum load pressure. I try to set it to a constant value that corresponds to the force.

On the other hand, the maximum pressure among the detected pressures of the load pressure sensing ports d and d of the second flow rate directional control valves 38a and 38b is selected by the shuttle valve 51 and transmitted to the port at one end of the shuttle valve 52. The pressure in the spring chamber of the pressure reducing type pressure compensating valve 36 is transmitted to the port at the other end of the valve 52, and the maximum pressure selected by the shuttle valve 52 is transferred from the central port to the line 5.
3 to the pump unit 33. In addition, the first and second flow rate directional control valves 37a, 37
b; When 38a and 38b are all in the neutral position, via the vent line 54 that passes through the vent passage 42 and load pressure sensing port d provided respectively,
The spring chamber of the pressure reducing type pressure compensating valve 36 and ports at both ends of the shuttle valve 52 communicate with the tank 55.

Each load port of the first flow direction control valve 37a is connected to the right travel hydraulic motor 30 via lines 61 and 62, respectively, and the first flow direction control valve 37b
Each load port is connected to the swing hydraulic motor 28 via lines 63 and 64, respectively. Further, each load port of the second flow rate directional control valve 38a is connected to the arm cylinder 26 via lines 65 and 66, respectively. A flow rate regulating valve 67 with a check, which serves as a meter-out restriction, is provided in the middle of the line 66. The line 65 communicates with the tank 55 via a check valve 68, and the line 66 communicates with the tank 55 via a relief valve 69. Each load port of the second flow rate directional control valve 38b is connected to the boom cylinder 25 via lines 70 and 71, respectively. A check valve 72 is provided in the middle of the line 70. The line 70 is connected to the tank 55 via a check valve 73, and the line 71
is communicated with the tank 55 via a relief valve 74.

On the other hand, the pump unit 33 includes two variable pumps 80a and 80b driven by an engine 79.
and the switching valves 81a and 81b, and the constant horsepower control valve 82d,
82b.

In order to match the discharge flow rate and discharge pressure of the variable pump 80a with the requirements of the flow rate directional control valve having the maximum load pressure, a shuttle is connected to the spring chamber of the switching valve 81a via a line 53 with a throttle 85 installed in the middle. While connecting the central port of the valve 52, the pressure of the main line 47 between the variable pump 80a and the pressure reducing type pressure compensating valve 36 is transmitted to the pilot chamber of the switching valve 81a to operate the switching valve 81a. That's what I do. The fluid pressure corresponding to the spring force of the spring 94 of this switching valve 81a is greater than the fluid pressure corresponding to the spring force of the spring 49 of the pressure reducing type pressure compensating valve 36. In addition, a main line 47 is connected to the pilot chamber of the constant horsepower control valve 82a.
and transmits a pressure signal to the constant horsepower control valve 82.
A feedback signal from the swash plate indicating the discharge amount of the variable pump 80a is transmitted to the constant horsepower control valve 82a via a signal transmission path 86 such as a link mechanism.
The variable pump 80a is operated so that the required horsepower, that is, the product of the discharge flow rate and the discharge pressure, is below a certain level. The constant horsepower control valve 82a
The port m of the switching valve 81a and the port Y of the switching valve 81a are connected to the main line 47, and the constant horsepower control valve 82a is connected to the main line 47.
The port l of the constant horsepower control valve 82a is connected to the tank 87, and the port n of the constant horsepower control valve 82a is connected to the port X of the switching valve 81a.
Port Z of the switching valve 81a is communicated with a discharge amount control section 88 consisting of a swash plate control cylinder of the variable pump 80a. Port n and port X are connected to the discharge amount control section 88 via a line 92 with a check valve 91 in the middle, and the fluid from the constant horsepower control valve 82a is connected to the switching valve 81a. This line 9 regardless of position
2 so that it can be directly supplied to the discharge amount control section 88. The spring chamber of the switching valve 81a is connected to the tank 9 via the pilot relief valve 93.
It is connected to 5.

The switching valve 81b and constant horsepower control valve 82b on the variable pump 80b side are connected in exactly the same way as the switching valve 81a and constant horsepower control valve 82a on the variable pump 80a side.

The power shovel with the above configuration operates as follows.

This power shovel is now in the state shown in FIGS. 2 and 3. In this state, both the first and second flow direction control valves 37b and 38b are switched to the symbol position _S1 , and the hydraulic motor 28 moves the rotating structure 22. At the same time, the boom cylinder 25 is extended and the boom 21 is raised to carry out the above-mentioned lifting and turning of the excavation work.

At this time, due to the large inertia of the rotating body 22,
At startup, the pressure in the load line 63 of the first flow rate directional control valve 37b, that is, the pressure in its load pressure sensing port d, becomes higher than the load line 70, that is, the pressure in its load pressure sensing port d, of the second flow rate directional control valve 38b. There is. The pressure at the load pressure sensing port d of the first flow rate directional control valve 37b, which is the maximum pressure, is selected by the shuttle valve 50 and
6 and the shuttle valve 52.
is selected and transmitted to the pump unit 33.

The pump unit 33 operates as described later to control the fluid so that the pressure in the main line 47 becomes a set pressure higher than the maximum pressure by a pressure corresponding to the spring force of the spring 94 of the switching valve 81a. Trying to spit it out.

On the other hand, since the load pressure of the second flow direction control valve 38b is lower than the load pressure of the first flow direction control valve 37b, the fluid in the main line 47 flows through the line 48 and the second flow direction control valve 38b. A large amount flows into the boom cylinder 25, causing the boom 21 to rise rapidly. During that time, the pressure in the main line 47 is affected by the large amount of fluid flowing into the boom cylinder 25 and becomes below the set pressure.
The pressure reducing type pressure compensation valve 36 is the first flow direction control valve 37
b cannot be pressure compensated, the flow rate supplied to the first flow direction control valve 37b and the hydraulic motor 28 decreases, the hydraulic motor 28 starts slowly, and the rotating body 22 starts smoothly and without shock. . After that, when the boom 21 finishes rising to a predetermined position, the second flow direction control valve 38b is placed in the neutral position to cut off the fluid supplied to the boom cylinder 25, and the pressure in the main line 47 corresponds to the maximum load pressure. The set pressure is reached, and the first flow rate directional control valve 37b is pressure-compensated by the pressure reducing type pressure compensation valve 36 to flow fluid at a flow rate proportional to the opening degree of the flow rate adjustment section, thereby controlling the proportional speed of the hydraulic motor 28. Let's do it.

Therefore, in this lifting and turning operation, the boom 21 is raised quickly at the time of startup, and at the same time, the rotating structure 22 is operated slowly and without shock.
After that, the rotating body 22 is connected to the first flow direction control valve 37b.
Since proportional speed control can be performed more accurately, work efficiency is excellent and safety is achieved.

Next, a heavy object (not shown) is hooked onto the bucket 24, and the first and second flow direction control valves 37b, 38 are
b is located at symbol position _S1 , and while the height of the boom 21 is adjusted by the boom cylinder 25, the swinging body 22 is rotated at a slow speed by the hydraulic motor 28 to perform crane work.

At this time, due to the heavy load, the pressure at the load pressure sensing port d of the second flow rate directional control valve 38b is higher than the pressure at the load pressure sensing port d of the first flow rate directional control valve 37b.

The load pressure of the second flow rate directional control valve 38b, which is the maximum pressure, is selected by the shuttle valves 51 and 52 and transmitted to the pump unit 33, which operates as described later to connect the main line 47 and The fluid is discharged so that the pressure in the line 48 becomes a set pressure higher than the maximum pressure by a pressure corresponding to the spring force of the spring 94 of the switching valve 81a.

Therefore, the differential pressure before and after the flow rate adjustment part of the second flow direction control valve 38b is caused by the spring 9 of the switching valve 81a.
In other words, the second flow rate directional control valve 38b is pressure-compensated, flows a flow rate proportional to the opening degree, and accurately controls the speed of the boom cylinder 25 regardless of the magnitude of the load. can.

On the other hand, the load pressure of the first flow rate directional control valve 37b selected by the shuttle valve 50 is transmitted to the spring chamber of the pressure reducing type pressure compensating valve 36. The spring force of the spring 49 corresponds to the differential pressure before and after the flow rate adjustment section of the first flow direction control valve 37b.
The flow direction control valve 37b is pressure compensated. Then,
The first flow direction control valve 37b accurately controls the proportional speed of the swing hydraulic motor 28 regardless of the magnitude of the load.

Therefore, in this crane work, both the first and second flow rate directional control valves 37b and 38b are pressure compensated, so that the boom cylinder 25 and the swing hydraulic motor 28 are not affected by other load pressures. Since the speed is accurately controlled without any movement, alignment is accurate, easy, and safe.

During the above operation, the pump unit 33 operates as follows.

The constant horsepower control valve 82d uses a feedback signal indicating the flow rate transmitted from the swash plate of the variable pump 80a via the signal transmission path 86, and a pressure signal from the main line 47 transmitted to the pilot chamber.
When the required horsepower of the variable pump 80d is less than the set horsepower, the switching valve 81 is located at symbol position _V2 .
The port X of a is communicated with the tank 87, and the variable pump 8
On the other hand, when the required horsepower of the variable pump 80a is about to exceed the set horsepower, the fluid in the main line 47 is controlled by the constant horsepower control valve 82a at the symbol position _V1 . The switching valve 81a is guided directly through the check valve 91 and the line 92 to the discharge amount control unit 88 regardless of the symbol position of the switching valve 81a to reduce the discharge amount of the variable pump 80a so that the required horsepower of the variable pump 80a is equal to or higher than the set horsepower. I try not to become Therefore, the engine 79 is not overloaded and the engine does not stall.

On the other hand, the constant horsepower control valve 82a is at the symbol position.
When the differential pressure between the maximum load pressure transmitted to the spring chamber of the switching valve 81a and the fluid pressure of the main line 47 becomes equal to or higher than the pressure corresponding to the spring force of the spring 94 of the spring chamber _in the state of being located at V2, The switching valve 81a is located at the symbol position V ₁ and the main line 47
The fluid is guided to the discharge amount control unit 88 through ports Y and Z of the switching valve 81a to reduce the discharge amount of the variable pump 80a and lower the pressure in the main line 47, and also to reduce the pressure in the main line 47 and the maximum load pressure. When the differential pressure between the switching valve 81a and the
_V2 , the discharge amount control section 88 is connected to the switching valve 81.
a and the tank 87 via the constant horsepower control valve 82a.
The discharge amount of the variable pump 80a is increased, and the pressure of the main line 47 is increased.

Therefore, this pump unit 33 uses the constant horsepower control valve 82a to suppress the required horsepower of the variable pump to below the set horsepower, and uses the switching valve 81a to match the discharge flow rate and discharge pressure of the variable pump 80a to the maximum load, thereby eliminating waste. Since no fluid is discharged, there is no power loss and there is an energy saving effect. In other words, the heat balance is improved and the fuel consumption of the engine 79 is saved.

Although the constant horsepower control valve 82a is used in the above embodiment, the port X of the switching valve 81a may be directly connected to the tank 87 without using this.

Further, in the above embodiments, a power shovel has been described, but the present invention is not limited to this, and includes, for example, stationary cranes, cargo handling machines, and the like.

As is clear from the above description, a construction machine such as a power shovel of the present invention has a boom pivotally attached to a rotating structure, and the load pressure sensing port controls the hydraulic motor that turns the rotating structure. A first flow rate directional control valve with a load pressure sensing port is connected to the variable pump via a pressure reducing type pressure compensation valve to compensate for pressure, and a second flow rate directional control valve with a load pressure sensing port is connected to the variable pump to control the boom cylinder that tilts the boom. It is connected to a line branching from between the variable pump and the pressure reduction type pressure compensation valve, and between the fluid pressure in the spring chamber of the pressure reduction type pressure compensation valve and the fluid pressure in the load pressure sensing port of the second flow rate directional control valve. The maximum pressure of is selected by a shuttle valve and transmitted to the spring chamber of the switching valve, while a line branching from between the variable pump and the pressure reducing type pressure compensating valve is connected to the pilot chamber of the switching valve, When the pressing force generated by the fluid pressure acting on the pilot chamber is greater than the sum of the pressing force generated by the fluid pressure acting on the spring chamber and the spring force, the switching valve controls the variable pump. When the discharge rate control section is connected to the main line for fluid supply, and the pressing force of the pilot chamber is smaller than the sum of the pressing force of the fluid acting on the spring chamber and the spring force, the discharge rate control section of the variable pump is connected to the tank line for fluid discharge, so if the load pressure on the hydraulic motor side is higher than the load pressure on the boom cylinder side, such as when lifting and turning, the boom cylinder can be quickly activated at startup. , the hydraulic motor can be operated without shock, resulting in excellent work efficiency and safety.On the other hand, when the load pressure on the hydraulic motor side is lower than the load pressure on the boom cylinder side, such as when working with a crane, the hydraulic motor boom cylinder,
The pressure-compensated first and second flow rate directional control valves allow accurate speed control without being affected by other load pressures, resulting in excellent work efficiency and safety.Moreover, the variable pump discharges wasted fluid. It has various advantages such as energy saving effect because there is no need to do anything.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a power shovel, Fig. 2 is a front view showing a part of a construction machine such as a power shovel according to an embodiment of the present invention as a circuit diagram, and Fig. 3 is a partially enlarged view of Fig. 2. It is. 21... Boom, 22... Swivel body, 25... Boom cylinder, 28... Hydraulic motor, 36... Pressure reducing type pressure compensation valve, 37a, 37b... First flow rate directional control valve, 38a, 38b... Second flow rate directional control valve, 52...Shuttle valve, 80a, 80b...Variable pump, 81a, 81b...Switching valve.

Claims (1)

[Claims] 1 In a construction machine such as a power shovel in which a boom 21 is pivotally connected to a revolving structure 22, the first flow rate directional control valve 37b with a load pressure sensing port that controls the hydraulic motor 28 that rotates the revolving structure 22 is replaced with a pressure reducing type pressure compensation valve. A second flow rate directional control valve 38b with a load pressure sensing port is connected to the variable pump 80a via the variable pump 80a for pressure compensation, and controls the boom cylinder 25 for tilting the boom 21.
It is connected to a line 48 branching from between the pressure reducing type pressure compensating valve 36 and the fluid pressure in the spring chamber of the reducing type pressure compensating valve 36 and the second flow rate directional control valve 3.
The maximum pressure among the fluid pressure of the load pressure sensing port 8b is selected by the shuttle valve 52, and the switching valve 81a is selected.
On the other hand, a line branching from between the variable pump 80a and the pressure reducing type pressure compensating valve 36 is connected to the pilot chamber of the switching valve 81a, and the switching valve 81a is connected to the pilot chamber of the switching valve 81a. When the pressing force generated by the fluid pressure acting on the spring chamber is larger than the sum of the pressing force generated by the fluid pressure acting on the spring chamber and the spring force, the discharge amount control section 88 of the variable pump 80a is turned off to supply fluid. When the pressing force of the pilot chamber is smaller than the sum of the pressing force of the fluid acting on the spring chamber and the spring force, the discharge amount control section 88 of the variable pump 80a is connected to the main line 47 for fluid discharge. A construction machine such as a power shovel, characterized in that it is connected to a tank line.