JP2002317471A - Oil pressure control circuit for hydraulic shovel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an overload of an engine due to increase of the output of a hydraulic pump, and to improve the upward slope traveling ability in the case of singly operating traveling of a vehicle without performing a combined operation. SOLUTION: The input torque from the engine 30 to four hydraulic pumps 32-35 is set at 1/4 in the normal standard input torque condition, and in order to increase to 1/2 to switch the torque condition to a high input torque condition when singly operating the traveling of a vehicle, shuttle valves 47 and 48 are connected to a pilot valve 46 and pilot valves 44 and 45, and the highest pressure is taken out by pressure sensors 49 and 50. Pressure signals from the pressure sensors 49 and 50 are taken into a controller 51. When an output level H of the pressure sensor 49 and an output level L of the pressure sensor 50 are detected, pressure is supplied from a booster pump 56 to increased output ports 52a-55a provided in regulators 52-55 of each hydraulic shovel 32-35 to increase the input torque from the engine 30 to the hydraulic pumps 32-35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control circuit of a hydraulic shovel, and more particularly to a hydraulic control circuit of a hydraulic shovel having a power shift function for increasing an input torque to a hydraulic pump of an engine during running of a vehicle. It is.

[0002]

2. Description of the Related Art A hydraulic excavator is a kind of construction machine for performing operations such as excavation of earth and sand, and the schematic configuration shown in, for example, FIG. In FIG. 1, reference numeral 1 denotes a lower traveling body, and 2 denotes an upper revolving superstructure.
The lower traveling body 1 has left and right crawler-type traveling means 3, and the left and right traveling means 3 respectively drive the driving wheels 3a by hydraulic motors, so that the vehicle travels. The upper revolving unit 2 is capable of turning with respect to the lower traveling unit 1.

[0003] The upper swing body 2 is provided with an operator cab 4 for an operator to board and operate the machine, and a work machine 5 for performing operations such as excavation of earth and sand. The work machine 5 includes a boom 6 connected to the upper revolving unit 2 so as to be capable of raising and lowering, an arm 7 connected to the tip of the boom 6 so as to be vertically rotatable, and a bucket 8 connected to the tip of the arm 7. The boom 6, the arm 7, and the bucket 8 are configured to be driven by a boom cylinder 6a, an arm cylinder 7a, and a bucket cylinder 8a, respectively. Further, a building 9 in which an engine, a hydraulic pump, and the like are provided is installed at a position rearward of a mounting portion of the operator cab 4 and the working machine 5.

[0004] The hydraulic excavator is almost entirely hydraulically driven. That is, the left and right traveling means are driven by a traveling hydraulic motor, the turning device is driven by a turning hydraulic motor, and each mechanism constituting the work machine 5 is driven by a hydraulic cylinder. In order to control the driving of the hydraulic actuator including the hydraulic motor and the hydraulic cylinder, the hydraulic shovel is provided with a hydraulic control circuit as shown in FIG.

In the figure, reference numeral 11 denotes an engine,
From the engine 11, four hydraulic pumps 13 to 16 are driven via a transmission 12. The hydraulic pumps 13 to 16 are of variable displacement type, and the discharge oil from each of the hydraulic pumps 13 to 16 is supplied to a control valve unit 17 to 20 respectively.
Is connected to each hydraulic actuator described above.
The directional control valves constituting each of the control valve units 17 to 20 are of a hydraulic pilot type, and each hydraulic actuator is operated by supplying a pilot pressure to these directional control valves by operating an operation lever. That is, the illustrated operating levers 21 and 22 are used for driving and turning the work machine 5, and include pilot valves 23 and 24 (specifically, the operating levers 21 and 22 are tilted left and right and back and forth. Accordingly, different hydraulic actuators are operated, and therefore, two sets of pilot valves are provided respectively).
The operation levers 25 and 26 are left and right operation levers for traveling, and a pilot valve 27 is also connected thereto.

Here, various hydraulic actuators are configured to be driven by the four hydraulic pumps 13 to 16 in order to perform a combined operation. For example, when excavating earth and sand, the ground is cut by the bucket 8 by operating the boom 6 and the arm 7, and immediately after that, the bucket 8 is operated while moving the arm 7. When the excavated earth and sand is loaded on the dump truck, a combined operation of turning and the working machine 5 is also performed. Further, among the hydraulic actuators, a large load acts on the boom cylinder 6a for driving the boom 6 and the arm cylinder 7a for driving the arm 7, so that the two hydraulic pumps may be combined.

The reason why a plurality of hydraulic pumps are connected to one engine 11 and each hydraulic pump is provided with a control valve unit in which a plurality of directional control valves are unitized for the above reasons. is there. Where 1
The number of hydraulic pumps connected to one engine is usually
Four or three hydraulic pumps are connected, but the number is not limited to these.

Since the four hydraulic pumps 13 to 16 are simultaneously operated, the total input torque of the hydraulic pumps 13 to 16 by the engine 11 is set so as not to exceed the rated torque of the engine 11. This is because, if the output state exceeds the rated torque of the engine 11, the engine 11 is overloaded and may be damaged. In other words, four hydraulic pumps 13 to 16 are assigned 1/4 of the total input torque from the engine 11, which is the standard input torque.

[0009]

By the way, pressure oil from one hydraulic pump is supplied to each of the traveling hydraulic motors for traveling the vehicle. Therefore, when the vehicle runs, only one half of the output of the engine 11 can be used. However, when the vehicle is traveling, the upper revolving superstructure 2 is not turned and the work implement 5 is not operated. That is, when the vehicle runs, substantially no other operations are performed in a complex manner. Of course, it is set such that the vehicle can run with the standard input torque to each pump. However, when the hydraulic excavator climbs a hill, the load may be large and the output may be insufficient. Therefore, the hill-climbing speed may be slow, and in a severe case, the hill may not be able to climb.

The present invention has been made in view of the above points, and an object of the present invention is to increase the output of a hydraulic pump only when a vehicle is operated alone, without performing a combined operation. An object of the present invention is to prevent engine overload and improve the ability to climb a hill.

[0011]

In order to achieve the above-mentioned object, the present invention comprises a left and right traveling hydraulic motor, a swing motor for an upper swing body, and a hydraulic cylinder for driving a front working machine. An engine, at least three or more variable displacement hydraulic pumps driven by the engine to supply pressure oil to each of the hydraulic actuators, and a plurality of direction switching valves respectively connected to the hydraulic pumps And a control valve unit in which one of the three or more control valve units is provided with one of the three or more control valve units for controlling the drive of one of the right and left traveling hydraulic motors. The first traveling direction switching valve is provided, and the other traveling control valve unit has the other traveling hydraulic motor. A second traveling directional control valve for driving control is provided for, on the pilot valve to operate the left and right travel hydraulic motors operating pilot valve and other hydraulic actuator of each provided the pressure detecting means,
When pressure is generated on the pilot valve side for operating the traveling hydraulic motor and no pressure is generated on the pilot valve side for operating other hydraulic actuators, when the pressure detecting means detects that The feature is that the output torque of each hydraulic pump is increased.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The overall configuration of the hydraulic excavator is not particularly different from that shown in FIG. 3, and therefore, the same or equivalent components will be described using the same reference numerals, and specific illustration and description thereof will be omitted. I do.

First, FIG. 1 shows a schematic configuration of a hydraulic control circuit of a hydraulic shovel. In the figure, reference numeral 30 denotes an engine. The engine 30 can drive four hydraulic pumps 32 to 35 via a transmission 31. The hydraulic pumps 32 to 35 are connected to control valve units 36 to 39, respectively, and each of the control valve units 36 to 39 is configured by unitizing a plurality of direction switching valves.

A number of hydraulic actuators provided on the hydraulic excavator are provided with these control valve units 36 to 3.
The pressure oil is supplied via one or two directional control valves constituting 9 and each is driven.
Each directional control valve is switched by a hydraulic pilot system, and the directional control valve is switched by operating an operation lever provided in the cab 4.

Usually, two operation levers 4 are used to control the operation of the work implement 5 and perform a turning operation.
0 and 41 are provided. In addition, operation levers 42 and 43 for traveling are provided. Here, the operation lever 4
Numerals 0 and 41 can be tilted left and right and back and forth, thereby operating four types of hydraulic actuators: a boom hydraulic cylinder 6a, an arm hydraulic cylinder 7a, a bucket hydraulic cylinder 8a, and a turning hydraulic motor. Control is performed. Reference numerals 44, 45, and 46 denote pilot valves. When one of the operation levers is operated, a pilot pressure is output from the corresponding pilot valve, and the directional switching valve is switched by the pilot pressure. Will operate.

The illustrated control valve unit 36
39, one directional switching valve 38a constituting the control valve unit 38 controls one of the left and right traveling hydraulic motors, and one directional switching valve 39a constituting the control valve unit 39.
Controls the other traveling hydraulic motor. Therefore, the hydraulic pilot pipes of these directional control valves 38a and 39a are connected to the pilot valve 46 on which the operation levers 42 and 43 are mounted. Therefore, during traveling, the hydraulic oil from the two hydraulic pumps 34 and 35 is supplied to the left and right traveling hydraulic motors.

When the operator runs the vehicle, the operating levers 42 and 43 are gripped and operated, so that the operating levers 40 and 41 for operating the working machine and turning are not operated. That is, when the vehicle travels, only the two hydraulic pumps 34 and 35 are driven, and the other two hydraulic pumps 32 and 33 are kept stopped. Therefore, the entire output of the engine 30 is allocated to the hydraulic pumps 34 and 35 only during traveling. That is, the torque input from the engine 30 to the hydraulic pumps 34 and 35 is increased from 標準, which is the standard input torque state, to １ ／, and the state is switched to the high input torque state. For this purpose, first, a mechanism for detecting that the vehicle is traveling and that no composite operation other than traveling has been performed,
A mechanism for increasing horsepower on the hydraulic pump based on a detection signal from the detection mechanism is provided.

First, at the time of traveling, the operation levers 42, 43
Is operated, and the operation levers 40 and 41 are not operated. Therefore, a pilot signal is output from the pilot valve 46, but no pilot signal is output from the pilot valves 44 and 45. Therefore, pilot valve 4
A shuttle valve 47 is connected to all the pilot pipes from 6 and a shuttle valve 48 is connected to all the pilot pipes from the pilot valves 44 and 45 so as to extract the highest pressure. The output side of the shuttle valves 47 and 48 respectively has a pressure sensor 4
9, 50 are connected. Furthermore, these pressure sensors 4
The pressure signals from 9 and 50 are configured to be taken into the controller 51.

With the above configuration, it is possible to detect whether or not the vehicle is running. That is, in order for the vehicle to travel, at least one of the direction switching valves 38a and 39a must be switched. That is, the pilot pressure must be output from the pilot valve 46. This pilot pressure is generated by the shuttle valve 4
8 through the pressure sensor 50. When the vehicle is running, the work implement 5 is not operated and the upper swing body 2 is not turned. Therefore, the operation levers 40, 4
Since 1 is not operated, no pilot pressure is generated in the pilot valves 44 and 45. Therefore, the pressure sensor 49
Is H and the output level of the pressure sensor 50 is L, it is detected that the vehicle is currently running and that no operation other than running is being performed. On the other hand, when the output level of the pressure sensor 50 is H, regardless of whether the output level of the pressure sensor 49 is H or L, the work implement 5 is operating or the turning operation is performed. Will be done. And both pressure sensors 49,
If both the output levels of H are H, regardless of whether or not the vehicle is running, it means that at least the work implement is operating or the turning operation is being performed.

As described above, the output level of the pressure sensor 49 for detecting the operation state of the pilot valve 46 is H, and the output level of the pressure sensor 50 for detecting the operation state of the pilot valves 44 and 45 is L. If this is the case, it is clear that the traveling alone operation is being performed. Therefore, the output signals of the pressure sensors 49 and 50 are taken into the controller 51. When the controller 51 determines that the traveling independent operation is performed, the four hydraulic pressures connected to the engine 30 are determined. Of the pumps 32 to 35, two hydraulic pumps (specifically, the hydraulic pumps 34, 3
5) Since only the drive is performed, the input torque of these hydraulic pumps is maintained within the rated torque range of the engine 30 even if the input torque is increased, that is, the input torque is changed from ４ to １ ／. Thus, the engine 30 is not overloaded.

Therefore, horsepower ports 52a to 55a are provided in the regulators 52 to 55 of the hydraulic pumps 32 to 35, and the booster pumps 5 are connected to the horsepower ports 52a to 55a.
6 are connected and provided. Therefore, when the pressure oil from the pressure boosting pump 56 is supplied to the horsepower boosting ports 52a to 55a, the tilt angles of the hydraulic pumps 32 to 35 increase, and the engine 3
0 can increase the input torque to the hydraulic pumps 32 to 35.

Intensifier pump 56 and regulators 52-5
An electromagnetic switching valve 57 is provided in a flow path between the horsepower increase ports 52a to 55a of the fifth solenoid valve 5. The electromagnetic switching valve 57 is controlled to open and close based on a signal from the controller 51. In, the electromagnetic switching valve 57 is kept in the closed state, and the pressure from the pressure increasing pump 56 is not guided to the regulators 52 to 55. Among the signals from the pressure sensors 49 and 50 input to the controller 51, the output level from the pressure sensor 49 becomes H, and the pressure sensor 5
When the output level from 0 is low, the solenoid on-off valve 57 opens based on the signal from the controller 51, and the horsepower ports 52a to 52g of the regulators 52 to 55 are opened.
Pressure is led to 55a. As a result, the hydraulic pumps 32 to
35 is in a high input torque state, and each of the hydraulic pumps 32-3
5 is 1/1 of the total input torque by the engine 30 respectively.
2 can be driven.

At this time, since the vehicle is in the traveling only operation state, the hydraulic pumps 34 and 35 are actually in the high load operation state, but the hydraulic pumps 32 and 33 are maintained in the no load operation state. Therefore, the output of the engine 30 does not exceed the rated torque. The relationship between the input torque of the pump, the discharge flow rate of the pump, and the discharge pressure (so-called PQ characteristic) in this state is as shown in FIG. In FIG. (A), the pump input torque T ₁ is the hydraulic pump is a maximum value of the standard input torque state, when operating the hydraulic pump in the high input torque state, the input torque is increased to T _2. As a result, in the PQ characteristic shown in FIG.
The standard input torque state, the pump discharge pressure is P _1, the pump delivery rate Q is decreased. That is, when the vehicle is traveling, when climbing a hill, when the load on the traveling hydraulic motor is small, that is, when the inclination angle of the hill is small, the discharge pressure of the hydraulic pump supplied to the traveling hydraulic motor becomes P
_{In a} state where the slope can be sufficiently climbed even if it is ₁ or less, there is no particular problem even when the hydraulic pump is in the standard torque state. However, the greater the inclination angle of the slope, the running load acting on the hydraulic motor is increased for the required discharge pressure from the hydraulic pump exceeds P _1, in the standard torque state, rapidly climbing speed decreases.

However, at the time of the traveling alone operation, the operation is automatically detected, and the shift control is performed so that the power of the hydraulic pump is increased. As a result, until the discharge pressure is P ₂ required from the hydraulic pump, since the discharge flow rate of the travel hydraulic cylinder does not change, the climbing speed does not decrease. Also, when the discharge pressure of the hydraulic pump exceeds P _2, the supply flow rate Q is reduced, but the running speed is reduced, the degree of slowdown small. Therefore, the climbing ability is significantly improved.

In addition, while the vehicle is running, the operation lever 4
When 0 and 41 are operated, the signal level from the pressure sensor 48 becomes H, so that the electromagnetic switching valve 57 is immediately switched to the closed state. As a result, the assignment of the total output torque of the engine 30 is returned to 1/4 for each of the hydraulic pumps 32 to 35, so that the engine 30 is not overloaded and its protection is achieved.

[0026]

As described above, according to the present invention, the output of the hydraulic pump is increased only when the vehicle is operated alone without the combined operation, thereby preventing the engine from being overloaded and improving the climbing ability. This has the effect of causing

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a hydraulic control circuit of a hydraulic shovel showing an embodiment of the present invention.

FIG. 2 is a diagram showing PQ characteristics of a hydraulic pump in a standard input torque state and a high input torque state.

FIG. 3 is an overall configuration diagram of a general hydraulic excavator.

FIG. 4 is a configuration diagram of a hydraulic control circuit of a conventional hydraulic shovel.

[Explanation of symbols]

 Reference Signs List 30 engine 32 to 35 hydraulic pump 36 to 39 control valve unit 38a, 39a directional switching valve for traveling 40 to 43 operating lever 44 to 46 pilot valve 47, 48 shuttle valve 52 to 55 regulator 49, 50 pressure sensor 51 controller 52a to 55a Boosting power port 56 Booster pump 57 Solenoid switching valve

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2D003 AA01 AB01 AB05 AC06 BA02 BB03 CA05 DA03 DB02 3H089 AA10 AA16 AA35 AA60 AA81 BB30 CC09 CC11 DA03 DA13 DB43 EE31 FF02 FF05 FF07 FF09 GG02 JJ02

Claims (2)

[Claims] A hydraulic motor for traveling on the left and right sides, a swing motor for an upper swing body, and a hydraulic cylinder for driving a front work machine are provided. At least three or more variable displacement hydraulic pumps driven by the engine;
In a hydraulic shovel connected to each of the hydraulic pumps and having a control valve unit in which a plurality of directional control valves are unitized, one of the three or more provided control valve units may have a left or right control valve unit. A first traveling direction switching valve for driving control of one traveling hydraulic motor is provided, and a second traveling direction for driving control of the other traveling hydraulic motor is provided in another control valve unit. A switching valve is provided, and pressure detection means are provided for each of the pilot valve for operating the left and right hydraulic motors for driving and the pilot valve for operating other hydraulic actuators, and pressure is generated on the pilot valve side for operating the hydraulic motor for traveling. However, pressure is generated on the pilot valve side for operating other hydraulic actuators. When detected by said pressure detecting means that no, the horsepower increasing means, the hydraulic control circuit of a hydraulic excavator, characterized in that it has a configuration to increase the output torque of the respective hydraulic pumps. 2. The horsepower increasing means includes a regulator for controlling a tilt angle of each of the hydraulic pumps, a pump for supplying a signal pressure to the regulator, and an electromagnetic on-off valve interposed between the pump and the regulator. 2. The hydraulic control circuit for a hydraulic shovel according to claim 1, wherein: