JPH0745744B2 - Hydraulic drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic drive system for a construction machine such as a hydraulic excavator, and in particular, a hydraulic pump dedicated to turning is provided separately from a hydraulic pump that drives a plurality of front actuators. The present invention relates to a hydraulic drive system for a construction machine equipped with the same.

[Conventional technology]

Conventionally, in a hydraulic drive system for a construction machine such as a hydraulic excavator, a plurality of actuators for the front and two actuators for traveling
It is known that two hydraulic pumps are used to drive one hydraulic motor, and a separate hydraulic pump dedicated to turning is provided to drive the turning motor. This is generally a three-pump system. It is called.

Generally speaking, this hydraulic drive system is connected to the first and second hydraulic pumps and the third hydraulic pump, and to the first and second hydraulic pumps via their respective directional control valves. A plurality of front hydraulic cylinders driven by oil discharged from the pump, a hydraulic motor for turning which is connected to a third hydraulic pump via a directional switching valve, and is driven by oil discharged from the hydraulic pump. Is equipped with. Generally, a traveling hydraulic motor is connected to the first and second hydraulic pumps, and the traveling hydraulic motor is also driven by the oil discharged from the first and second hydraulic pumps. Has become.

By the way, in this type of hydraulic drive device, the discharge flow rate of the third hydraulic pump dedicated to turning is adjusted so that the supply flow rate of the hydraulic actuator matches the required flow rate as much as possible while effectively utilizing the discharge flow rate of the hydraulic pump. It is devised to supply oil to the front hydraulic cylinder within a range that does not affect the turning operation and does not affect the turning operation. For example, in Japanese Utility Model Laid-Open No. 51-77491, the second directional control valve for booms (FIG. 2) or the second directional control valve for arms (FIG. 4) is arranged in tandem downstream of the directional control valve for turning. ) Is connected and the discharge oil from the third pump is preferentially supplied to the swing motor when the turning direction switching valve is operated, but when the turning direction switching valve is not operated Disclosed is a configuration in which the discharge oil of the third pump can be supplied to a boom cylinder or an arm cylinder, and acceleration or high load operation of these cylinders is achieved.

[Problems to be solved by the invention]

However, in all of the conventional hydraulic drive devices, the discharge oil of the third hydraulic pump is used for other hydraulic actuators only by devising the valve structure and connection method of the directional control valve. Has a structure in which the application to the hydraulic actuator is uniquely determined, and when the discharge oil of the third pump is to be supplied to a different hydraulic actuator or is to be supplied by a different connection method, the direction switching is performed. Reconnection of valves or piping had to be done.

For example, in Japanese Utility Model Publication No. 51-77491, the second
In the circuit shown in the figure, the discharge oil from the third pump cannot be supplied to the parts other than the boom cylinder except for the swing motor. You must change the piping connections as shown in. Even when supplying to the same boom cylinder, the pressure oil at the time of starting the swing motor is supplied to the boom cylinder without relief, or the swing pressure and boom raising pressure are made the same, and the performance of the combined swing and boom raising operation is improved. If more complex movements are desired, the valve connections must be rearranged from tandem to parallel. Furthermore, in order to be able to supply both the boom cylinder and the arm cylinder, the valve connection must be rearranged, and even in this case, the valve connection method is one such as tandem or parallel. It could only be adopted, and it was not possible to perform diverse complex actions.

Therefore, an object of the present invention is to increase the effective use of the discharge oil of the third hydraulic pump by adding a simple circuit, and to perform various complex operations using the discharge oil. It is to provide a hydraulic drive device.

[Means for solving problems]

The above object is to connect the third hydraulic pump to a hydraulic circuit portion, which supplies pressure oil to the bottom side of a plurality of front hydraulic cylinders, on the downstream side of the front directional control valve via an auxiliary pipeline. , Solenoid valves are respectively connected to these auxiliary pipelines and the downstream side of the auxiliary pipeline connection point between the third hydraulic pump and the hydraulic motor for turning, and these solenoid valves are connected,
The present invention is achieved by a hydraulic drive device characterized in that control is performed according to an operation signal instructing an extension operation of a front hydraulic cylinder and an operation signal of a turning hydraulic motor.

[Action]

When the operation signal of the swing motor is output, the solenoid valve connected to the downstream side of the auxiliary pipeline connection point between the third hydraulic pump and the swing hydraulic motor is opened, and the other solenoid valves are closed. . Thereby, the oil discharged from the third hydraulic pump is supplied only to the turning hydraulic motor, and the turning hydraulic motor is independently driven as usual.

When the operation signal for the swing hydraulic motor is not output and the operation signal for instructing the extension operation of any of the front hydraulic cylinders is output, the solenoid valve corresponding to the swing hydraulic motor is closed and the other solenoid valves are closed. Any hydraulic cylinder corresponding to can be opened. As a result, in addition to the oil discharged from the first and second hydraulic pumps, the oil discharged from the third hydraulic pump is supplied to the bottom side of the hydraulic cylinder with the solenoid valve opened, increasing the extension operation. High speed or high load operation becomes possible.

When the operation signal for the swing hydraulic motor and the operation signal for instructing the extension operation of the boom hydraulic cylinder of the front hydraulic cylinders are output, the solenoid valve and boom hydraulic cylinder corresponding to the swing hydraulic motor are output. The corresponding solenoid valve can be opened. As a result, the third hydraulic pump is connected in parallel to the swing hydraulic motor and the boom hydraulic cylinder, and excess pressure oil at the time of starting the swing hydraulic motor is supplied to the boom hydraulic cylinder without relief. , The swing pressure and the boom raising pressure are made the same to improve the performance of the combined movement of the swing and the boom raising.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. This embodiment is an example in which the present invention is applied to a backhoe type hydraulic excavator.

FIG. 1 shows a hydraulic circuit of a hydraulic drive system of this embodiment together with a control system thereof. In the figure, reference numerals 1, 2, and 3 denote first to third rotational drives driven by a common prime mover 4, respectively. There are three hydraulic pumps.

The hydraulic drive system includes the first to third hydraulic pumps 1, 2,
3, the boom hydraulic cylinder 5 and the arm hydraulic cylinder 6 driven by the discharge oil from the first and second hydraulic pumps 1 and 2, and the discharge oil from the second hydraulic pump 2 A bucket hydraulic cylinder 7 and a turning hydraulic motor 8 driven by the oil discharged from the third hydraulic pump 3. The first hydraulic pump 1 is the first
Boom direction switching valve 9 and first arm direction switching valve
The second hydraulic pump 2 is connected to the boom hydraulic cylinder 5 and the arm hydraulic cylinder 6 via 10 respectively.
It is connected to the boom hydraulic cylinder 5, the arm hydraulic cylinder 6 and the bucket hydraulic cylinder 7 via the second boom direction switching valve 11, the second arm direction switching valve 12 and the bucket direction switching valve 13, respectively. , The third hydraulic pump 3
Is connected to the turning hydraulic motor 8 via a turning direction switching valve 14.

The boom hydraulic cylinder 5, the arm hydraulic cylinder 6, and the bucket hydraulic cylinder 7 are the boom 1 that constitutes the front mechanism in a backhoe type hydraulic excavator.
5, the arm 16 and the bucket 17 are mounted as shown in FIG. 2, and the boom is raised, the arm is lowered or pulled, and the bucket is pulled or raised by the extension operation. The turning hydraulic motor 8 is mounted inside the turning base 18,
The swivel base 18 is swung.

Although not shown in FIG. 1, the traveling hydraulic motors for driving the traveling device 19 of the hydraulic excavator are connected to the first and second hydraulic pumps 1 and 2 via directional switching valves, respectively. There is.

The third hydraulic pump 3 also comprises, according to the invention, a hydraulic cylinder 5 downstream of the front directional control valves 9-13.
To a hydraulic circuit portion for supplying pressure oil to the bottom side, for example, the second boom direction switching valve 11 and the boom hydraulic cylinder 5.
Main pipe line 20 connecting the bottom side of the second arm, the main pipe line 21 connecting the second arm direction switching valve 12 and the bottom side of the arm hydraulic cylinder 6, and the bucket direction switching valve 13 and the bucket hydraulic cylinder 7. To the main conduit 22 that connects the bottom side of
They are connected via auxiliary pipes 23, 24 and 25, respectively. Electromagnetic proportional valves 26, 27, 28 are provided in these auxiliary pipelines 23, 24, 25, and electromagnetic valves are provided downstream of the auxiliary pipeline connection point 29 between the third hydraulic pump 3 and the hydraulic motor 8 for turning. A proportional valve 30 is provided.

The control device for the hydraulic drive device is provided with an arithmetic unit 31, which inputs the operation signals output from the operating levers 32 and 33, and which receives the directional control valves 9 to 13 for the front and the directional control valve 14 for the turning. Also, command signals are output to the solenoid proportional valves 26 to 28 and 30. The operation levers 32 and 33 are respectively moved in two directions orthogonal to each other, and an operation signal for turning and a boom operation signal are output by operating the operation lever 32 in each direction, and an arm is operated by operating the operation lever 33 in each direction. And a bucket operation signal are output.

As shown in FIG. 3, the computing unit 31 receives the operation signals from the operation levers 32 and 33, switches, selects, and outputs the multiplexer 34, and the operation signal output through the multiplexer 34 as a digital signal. A / D converter to convert to 35
A RAM 36 for temporarily storing these signals and the like, a ROM 37 for storing a control program for executing a processing procedure described later, and a central processing unit for processing operation signals in accordance with the control program stored in the ROM 37. Device or CP
U38, direction switching valves 9-14 and solenoid proportional valves 26-28 and 30
And an output port 39 that amplifies and outputs the output from the CPU 38.

In the ROM 37, in addition to a general control program for controlling the directional control valves 9 to 14 according to the operation signals of the operation levers 32 and 33, electromagnetic proportional valves 26 to 28 and electromagnetic proportional valves 26 to 28 as shown in FIG. A control program for controlling 30 is stored.

Next, the operation of the hydraulic drive device configured as described above will be described in the fourth section.
This will be described with reference to the flowchart shown in the figure.

In the backhoe type hydraulic excavator, the boom 15, the arm 16 and the bucket 17 that form the front mechanism are
The boom raising, arm lowering, and bucket pulling operations corresponding to the extending operations of the respective hydraulic cylinders 5 to 7 are operations generally in the direction in which the required flow rate is large and the load is large. From this, in the arithmetic unit 31,
Regarding the front operation signals output from the operation lever, boom up operation signals, arm down operation signals,
The bucket pulling operation signal and other operation signals, that is, the operation signal for instructing the extension operation of the front hydraulic cylinders 5 to 7 and the other operation signals are processed separately.

That is, first, when the operation levers 32 and 33 are operated, the operation signal outputs an operation signal for instructing a turn (hereinafter abbreviated as an operation signal), a boom raising operation signal (abbreviated as an operation signal), and an arm lowering signal. It is determined whether or not it is one of the operation signals (hereinafter abbreviated as an operation operation) and the bucket pulling operation signal (hereinafter abbreviated as an operation signal) (step S1). If the operation signal is 0, , The solenoid proportional valve 30 is opened, and the other solenoid proportional valves 26 to 28 are closed (step S2). As a result, the front hydraulic cylinders 5-7
Is driven by discharge oil from the first and second hydraulic pumps 1 and 2 as usual.

When the operation signal is one of the above operation signals, different processing is performed depending on which of the operation signals it is. That is, when it is an operation signal,
The solenoid proportional valve 30 is opened and the other solenoid proportional valves 26 to 28 are closed (step S3). As a result, the oil discharged from the third hydraulic pump 3 is supplied to the turning hydraulic motor 8 to perform a single turning operation. In the case of an operation signal, the solenoid proportional valve 30 is closed, the solenoid proportional valve 26 is opened, and the other solenoid proportional valves 2
7,28 are closed (step S4). As a result, in addition to the discharge oil from the first and second hydraulic pumps 1 and 2, the discharge oil from the third hydraulic pump 3 joins and is supplied to the bottom side of the boom hydraulic cylinder 5 to generate hydraulic pressure. It is possible to speed up the extension operation of the cylinder 5 or perform high load operation. Similarly, when the operation signal is or, the solenoid proportional valve 30 is closed,
The solenoid proportional valve 27 or 28 is opened and the other solenoid proportional valves 26,2
8 or 26, 27 are closed (steps S5, S6). As a result, the discharge oil from the third hydraulic pump 3 joins and is supplied to the bottom side of the arm hydraulic cylinder 6 or the bucket hydraulic cylinder 7 as well, so that the extension operation of these hydraulic cylinders or the high load operation can be performed. It will be possible. Also, the third
It is possible to effectively use the discharge oil of the hydraulic pump 3.

When the operation signals are two or more of the above operation signals, it is determined whether or not there are two operation signals (step S7), and when there are two, which combination of operation signals they are. Different processing is performed depending on whether there is. That is, in the case of the operation signal, the solenoid proportional valves 26, 30 are opened and the other solenoid valves 27, 28 are closed (step S8). As a result, the third hydraulic pump 3 is connected in parallel to the swing hydraulic motor 8 and the boom hydraulic cylinder 5, and excess pressure oil at the start of the swing hydraulic motor is supplied to the boom hydraulic cylinder 5 without relief. ,
The discharge oil of the third hydraulic pump 3 can be effectively used. Further, the turning pressure and the boom raising pressure are made the same to improve the performance of the combined action of turning and boom raising.

When the operation signal is or, the solenoid proportional valve 30 is opened and the other solenoid proportional valves 26 to 28 are closed (step S
9, S10). As a result, the combined operation of turning and lowering the arm or pulling the bucket can be performed independently of each other as is conventionally done.

When it is an operation signal, it is first determined whether or not the difference between the operation amounts indicated by the operation signals is a certain value or more (step S11), and if it is less than the certain value, the solenoid proportional valve 26,
27 are proportionally controlled so that their openings are proportional to the manipulated variable of the operation signal.
8,30 are closed (step S12). As a result, the discharge oil of the third hydraulic pump 3 joins and is supplied to the bottom sides of the boom hydraulic cylinder 5 and the arm hydraulic cylinder 6 at a flow rate distributed according to the ratio of the operation amounts of the operation signals. The combined operation of raising the boom and lowering the arm adapted to the ratio of the operation amount indicated by the operation signal can be performed by using the oil discharged from the third hydraulic pump 3.

If the difference in the operation amount of the operation signal is a certain value or more,
The solenoid proportional valve 26 is opened, and the other solenoid proportional valves 27, 28, 30 are closed (step S13). As a result, the discharge oil of the third hydraulic pump 3 joins and is supplied to only the bottom side of the boom hydraulic cylinder 5. The reason for doing this is as follows.

The backhoe type hydraulic excavator has a pile operation in which the bucket 17 is pulled toward the main body side and piled up after the earth and sand excavation. At this time, in order to pull the bucket 17 toward the main body side, the arm 16 is lowered while raising the boom 15, but the load pressure for boom raising at this time is extremely large, while the load pressure for lowering the boom is smaller than that. Therefore, in order to avoid that the oil discharged from the hydraulic pump is supplied only to the arm hydraulic cylinder with a light load and the boom cannot be raised, the operation amount of the boom operation lever is maximized and the operation amount of the arm operation lever is set to the maximum. A small amount. In such a combined operation, it is desired to supply as much pressure oil as possible to the boom hydraulic cylinder to quickly pull the bucket. Therefore, when the difference between the operation amounts of the operation signals is equal to or greater than a certain value, it is determined that this composite operation is performed, and as described above, the discharge oil of the third hydraulic pump 3 is supplied only to the boom hydraulic cylinder 5. Supply to the bottom side. As a result, the boom can be quickly raised, and the bucket can be pulled toward the main body side in a short time in the pile work to rationalize the work.

When the operation signal is or, the proportional solenoid valves 26, 28 or 27, 28 are proportionally controlled so that their openings are proportional to the manipulated variable of the operation signal or, and the other proportional solenoid valves are closed. (Step S14 or S
15). As a result, on the bottom side of the boom hydraulic cylinder 5 and the bucket hydraulic cylinder 7 or the arm hydraulic cylinder 6 and the bucket hydraulic cylinder 7, the discharge oil of the third hydraulic pump 3 becomes a ratio of the operation signal or the operation amount of. The combined operation of boom raising and bucket pulling or arm lowering and bucket pulling, which is supplied and merged in accordance with the ratio of the operation signal indicated by the operation signal or, is discharged according to the discharge of the third hydraulic pump 3. It can also be done using oil.

In particular, the combined operation of the operation signals is when performing light excavation by lowering the arm and pulling the bucket, and in this work, it is desirable to reliably pull the bucket regardless of fluctuations in the load. According to this embodiment, when the load pressure of the bucket hydraulic cylinder 7 is smaller than the load pressure of the arm hydraulic cylinder 6, the oil discharged from the third hydraulic pump 3 is proportionally distributed to the bucket hydraulic cylinder 7. Is also supplied, it is possible to speed up the light excavation work, and when the load pressure of the bucket hydraulic cylinder 7 is larger,
The pressure oil of the third hydraulic pump 3 is surely supplied to the hydraulic cylinder 7
Is supplied to the hydraulic cylinder 7, it is possible to avoid a situation where the hydraulic cylinder 7 does not move.

When the operation signals are three or more of the above operation signals, it is judged whether or not there are three operation signals (step S16), and when there are three, it is determined by any combination of the operation signals. Different processing is performed depending on whether there is. That is, when it is an operation signal,
The solenoid proportional valves 26, 30 are opened and the other solenoid valves 27, 28 are closed (step S17). As a result, the third hydraulic pump 3
Is connected in parallel to the swing hydraulic motor 8 and the boom hydraulic cylinder 5, and supplies excess pressure oil to the boom hydraulic cylinder 5 without relief when starting the swing hydraulic motor, as described above. Alternatively, a combined operation of turning, boom raising, and arm lowering can be performed while making the turning pressure and the boom raising pressure the same.

When it is an operation signal, the solenoid proportional valve 30 is opened, and the other solenoid proportional valves are closed (step S18). As a result, the oil discharged from the third hydraulic pump 3 is supplied only to the turning hydraulic motor 8, and the turning and the arm and bucket independent independent operations can be performed as usual.

When it is an operation signal, the solenoid proportional valve 26 is opened, and the other solenoid proportional valves are closed (step S19). As a result, the oil discharged from the third hydraulic pump 3 is supplied to the bottom side of the boom hydraulic cylinder 5.

The combined operation of the operation signals includes a horizontal pulling operation in which the boom 16 is raised, the arm 16 is lowered, and the bucket 17 is pulled in order to level the excavation surface. In this work, the load pressure of the boom hydraulic cylinder becomes extremely higher than the load pressure of the arm and bucket hydraulic cylinders. Therefore, as described above, the third hydraulic pump 3
By supplying the discharge oil to the bottom side of the boom hydraulic cylinder 5 only, it is possible to reliably supply the pressure oil to the boom hydraulic cylinder 5 having a large load, and to perform the horizontal pulling work smoothly.

When the operation signals are four of the above operation signals, the solenoid proportional valves 26, 30 are opened and the other solenoid proportional valves are closed (step S20). As a result, the turning hydraulic motor 8 and the boom hydraulic cylinder 5 are connected in parallel to the third hydraulic pump, and the turning operation is performed while the hydraulic motor 8 and the hydraulic cylinder 5 are harmonized in the same relationship as described above. It is possible to perform a combined operation of raising the boom, lowering the arm, and pulling the bucket.

Therefore, as described above, according to this embodiment, the auxiliary pipelines 23 to 25
And, by adding a simple circuit consisting of electrically controlled solenoid proportional valves 26 to 28 and 30, it is possible to expand the effective use of the discharge oil of the third hydraulic pump, and to utilize various kinds of the discharge oil. It is possible to perform the combined operation of.

In the above embodiments, the solenoid proportional valves whose valve opening changes in proportion to the command signal are used as the solenoid valves 26 to 28 and 30, but this may be a simple solenoid opening / closing valve. Although the operation by the proportional control of the solenoid valve in the embodiment described above cannot be obtained, other operations can be obtained. Even in this case, the effective use of the discharge oil of the third hydraulic pump can be achieved as compared with the conventional hydraulic drive device. It is possible to obtain the effect of increasing the number of times and performing various combined operations using the discharged oil.

Further, in the above embodiment, the auxiliary pipelines 23, 24 are connected to the downstream side of the second boom direction switching valve 11 and the second arm direction switching valve 12, but the first boom direction switching valve 9 is connected. It will be clear that it may also be connected downstream of the first arm directional control valve 10.

Further, the solenoid proportional valve 30 is connected upstream of the turning direction switching valve 14, but even if it is connected downstream of the center bypass, the supply of the pressure oil to the turning hydraulic motor 8 is controlled to be cut off as in the above embodiment. be able to.

Furthermore, although the above-described embodiments are embodiments in which the present invention is applied to a backhoe type hydraulic excavator, the present invention can be widely applied to construction machines equipped with other swivel bases and front mechanisms. For example, the present invention can be applied to a loader type hydraulic excavator, in which case the control program shown in the flow chart in FIG. 4 is modified accordingly. In this case, for example, in order to reliably supply the pressure oil to the bucket hydraulic cylinder that requires a large flow rate in the heavy excavation work of raising the arm and raising the bucket (both of which are extension operations in the hydraulic cylinder), refer to FIG. The procedure of step S15 shown may be changed so that the proportional solenoid valve 28 is opened and the other proportional solenoid valves are closed. As a result, the oil discharged from the third hydraulic pump 3 is supplied only to the bucket hydraulic cylinder 7, and heavy excavation unique to a loader type hydraulic excavator can be smoothly performed.

〔The invention's effect〕

As is apparent from the above, according to the hydraulic drive system of the present invention, the effective use of the discharge oil of the third hydraulic pump can be expanded and the discharge oil can be used only by adding the auxiliary pipeline and the electromagnetic valve. It is possible to perform various complex operations.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a hydraulic drive system according to an embodiment of the present invention, FIG. 2 is a side view of a backhoe type hydraulic excavator to which the hydraulic drive system is applied, and FIG. FIG. 4 is a block diagram showing a configuration of an arithmetic unit that constitutes a control device of the hydraulic drive system, and FIG. 4 is a flowchart showing an outline of a control program stored in the arithmetic unit. Explanation of reference numerals 1, 2 ... First and second hydraulic pumps 3 ... Third hydraulic pump 5-7 ... Front hydraulic cylinder 8 ... Turning hydraulic motor 9-14 ... Direction switching valve 23-25 ... Auxiliary pipeline 26 to 28,30 ... Proportional solenoid valve 30 ... Auxiliary line connection point

Claims (2)

[Claims] 1. A first hydraulic pump, a second hydraulic pump, and a third hydraulic pump, which are connected to the first hydraulic pump and the second hydraulic pump via respective direction switching valves, and are driven by oil discharged from these hydraulic pumps. Is connected to a plurality of front hydraulic cylinders and a third hydraulic pump via a directional control valve,
In a hydraulic drive system for a construction machine, comprising: a hydraulic motor for turning driven by oil discharged from the hydraulic pump, a third hydraulic pump is provided on a downstream side of the directional control valve for the front, Is connected to a hydraulic circuit portion for supplying pressure oil to the bottom side of the hydraulic cylinder of the auxiliary cylinder via auxiliary pipes, and the auxiliary pipe connection points between the auxiliary hydraulic pipe and the third hydraulic pump and the hydraulic motor for turning are connected. A solenoid valve is connected to each of the downstream side, and these solenoid valves are configured to be controlled according to an operation signal for instructing an extension operation of a front hydraulic cylinder and an operation signal for a turning hydraulic motor. Characteristic hydraulic drive. 2. The hydraulic drive system according to claim 1, wherein the solenoid valve is a proportional control valve.