JP2002039112A - Hydraulic device for construction work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic device for a construction work machine capable of improving construction work efficiency and preventing overheat. SOLUTION: This hydraulic device of the construction work machine is provided with a hydraulic motor 2 for construction work rotating and driving a construction work device 56 and a hydraulic motor 4 for elevating and lowering the construction work device 56. A hydraulic pump is provided with double variable displacement pumps P1, P2 and a fixed displacement type pump P3, hydraulic fluid is supplied to the hydraulic motor 2 for construction work from the variable displacement type pump P1 on one side and the fixed displacement type pump P3, and hydraulic fluid is supplied to the hydraulic motor 4 for elevation through a flow control valve 42 from the variable displacement type pump P2 on the other side. Double variable displacement type pumps P1, P2 are swash plate type plunger pumps and use a swash plate in common.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic device of a construction machine for supplying hydraulic oil from a hydraulic pump driven by an internal combustion engine to a construction hydraulic motor and a lifting hydraulic motor.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a hydraulic pump is driven by an internal combustion engine 1 mounted on a construction machine, and hydraulic oil from the hydraulic pump is supplied to a construction hydraulic motor 2 and a lifting hydraulic motor. 4 and supply. The hydraulic pump is 2
Variable displacement pumps P1 and P2 and constant displacement pump P3
And

As shown in FIG. 4, the two variable displacement pumps P1 and P2 are swash plate type plunger pumps and have a structure in which the swash plate 12 is shared. The swash plate 12 receives the acting force of the spring 14 and the cylinder 16 facing each other,
The inclination angle of the swash plate 12 is configured to be variable.

A main shaft 18 passes through the center of the swash plate 12, and the main shaft 18 is connected so as to be driven to rotate by the internal combustion engine 1. Housings 20, 2 are provided on both sides of the swash plate 12.
2 are arranged, and the housings 20 and 22 are
It is constituted so that it may rotate in one.

A plurality of pistons 24 to 27 are slidably inserted in the housings 20 and 22 in parallel with the main shaft 18, and rods 28 to 31 integrated with the pistons 24 to 27.
Is configured to contact the swash plate 12.
As the main shaft 18 rotates, the housings 20 and 22 rotate, and the rods 28 to 31 move while contacting the swash plate 12. This causes the pistons 24 to 27 to reciprocate,
It is configured to discharge the pressurized hydraulic oil.

[0006] A constant displacement pump P3 is connected to the main shaft 18, and both variable displacement pumps P1 and P2 and the constant displacement pump P3 are configured as a unit. Used as common parts in construction machines such as hydraulic excavators. One variable displacement pump P1
Is connected to the construction hydraulic motor 2 via a switching valve 32 and to a hydraulic tank 36 via a relief valve 34. The switching valve 32 supplies a working oil to the construction hydraulic motor 2 from the variable displacement pump P1 and rotates the construction hydraulic motor 2 in the normal rotation position 32a.
And a reverse rotation position 32c for supplying hydraulic oil from the variable displacement pump P1 to the hydraulic motor 2 for construction and for reverse rotation.

The other variable displacement pump P2 also has a switching valve 3
8 and is connected to the hydraulic tank 36 via a relief valve 40. The switching valve 38 has a forward rotation position 38a, a stop position 38b for interrupting connection with the construction hydraulic motor 2, and a reverse rotation position 38c, similarly to the switching valve 32 described above.

[0008] A gear pump is used as the constant displacement pump P3.
2. It is connected to the lifting hydraulic motor 4 via the switching valve 44 and to the hydraulic tank 36 via the relief valve 46. The switching valve 44 also has an up position 44a, a stop position 44b, and a down position 44c.

The flow control valve 42 is a constant displacement pump P
A variable throttle 48 for reducing the amount of hydraulic oil supplied from 3 to the switching valve 44, and a relief valve 50 for connecting the hydraulic pump 36 to the fixed displacement pump P <b> 3 side of the variable throttle 48. The relief valve 50 operates by detecting the pressure upstream and downstream of the variable throttle 48.

In the hydraulic motor 2 for construction, a tool 56 such as an auger drill or a stirring blade is rotated via a speed reducer 54. A drive mechanism 58 is constituted by the construction hydraulic motor 2 and the reduction gear 54, and a lifting mechanism 60 driven by the lifting hydraulic motor 4 raises and lowers the drive mechanism 58 along a reader (not shown) of the construction machine. It is configured as follows.

In the hydraulic device of the construction machine configured as described above, the pumps P1, P2, and P3 are driven by the internal combustion engine 1. When the switching valves 32, 38 are switched to the forward rotation positions 32a, 38a, respectively, the operating oil discharged from both the variable displacement pumps P1, P2 is switched to the switching valves 32, 3
8 to the construction hydraulic motor 2. Therefore,
The construction hydraulic motor 2 is rotated, and the application tool 56 such as an auger drill or a stirring blade is rotated via the speed reducer 54.

When the switching valve 44 is switched to the lowered position 44c, the hydraulic oil discharged from the constant displacement pump P3 is supplied to the lifting hydraulic motor 4 via the flow control valve 42 and the switching valve 44. . Therefore, the application tool 56 is lowered and pushed into the ground, and excavation is performed.

When the load of the lifting hydraulic motor 4 increases,
The discharge pressure from the constant displacement pump P3 increases. The increased discharge pressure is introduced into the cylinder 16, the inclination angle of the swash plate 12 decreases, and the amount of hydraulic oil discharged from both the variable displacement pumps P1 and P2 decreases. When the load of the construction hydraulic motor 2 increases, the two variable displacement pumps P1, P2
The discharge pressure discharged from is increased. The inclination angle of the swash plate 12 is reduced by the action of this pressure, and the amount of hydraulic oil discharged from both the variable displacement pumps P1 and P2 is reduced.
Thus, the output horsepower of the internal combustion engine is controlled to be substantially constant.

The total amount of hydraulic oil discharged from both variable displacement pumps P1 and P2 is indicated by a thick solid line in FIG. 5 when the hydraulic oil pressure discharged from constant displacement pump P3 is almost zero. Along such a pump horsepower control line, the pressure varies with the load pressure of the variable displacement pumps P1 and P2. Further, FIG. 5 shows a case where the hydraulic oil pressure discharged from the constant displacement pump P3 is the maximum pressure, with a thin solid line. The pump horsepower control line of the two variable displacement pumps P1 and P2 merges between the thick solid line and the thin solid line as indicated by the arrow due to the load pressure of the constant displacement pump P3.

On the other hand, since the rotation speed of the internal combustion engine 1 is substantially constant, a constant displacement hydraulic oil is discharged from the constant displacement pump P3. The lifting hydraulic motor 4 is controlled at a low flow rate by controlling the amount of flow into the lifting hydraulic motor 4 by a flow control valve 42, and therefore, most of the hydraulic oil discharged from the constant displacement pump P3 is a relief valve. It is returned to the hydraulic tank 36 via 50.

[0016]

However, in such a conventional apparatus, when the load of the constant displacement pump P3 is large, the discharge amount from both the variable displacement pumps P1 and P2 is greatly reduced, and the working tool 56 The number of rotations is insufficient,
There was a problem that construction efficiency was reduced. Also,
Most of the pressure oil from the constant displacement pump P3 is supplied to the flow control valve 42.
, The energy efficiency is low and the internal combustion engine 1 may be overheated.

An object of the present invention is to provide a hydraulic device for a construction machine in which construction efficiency is improved and overheating is prevented.

[0018]

In order to achieve the above object, the present invention takes the following means to solve the problem. That is, hydraulic fluid from a hydraulic pump driven by an internal combustion engine of a construction machine having a drive mechanism that rotationally drives a tool by a construction hydraulic motor and a lifting mechanism that raises and lowers the drive mechanism by a lifting hydraulic motor. In a hydraulic device of a construction machine that supplies the construction hydraulic motor and the lifting hydraulic motor, the hydraulic pump includes a double variable displacement pump and a constant displacement pump, and one of the variable displacement pump and And a hydraulic pump for supplying hydraulic fluid to the construction hydraulic motor from a constant displacement pump, and supplying hydraulic fluid to the lifting hydraulic motor from the other variable displacement pump via a flow control valve. That is the hydraulic system.

The two variable displacement pumps may be swash plate type plunger pumps and may share the swash plate. Further, the discharge amount of the constant displacement pump may be smaller than the maximum discharge amount of the variable displacement pump.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the same members as those of the above-described conventional hydraulic device are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, the construction hydraulic motor 2 is connected so that hydraulic oil is supplied from one variable displacement pump P1 via a switching valve 32, and the constant displacement pump P3 Is connected so that the hydraulic oil is supplied from the switching valve 44 via a switching valve 44. The switching valve 32 has a forward rotation position 32.
a, a stop position 32b, and a reverse rotation position 32c.
4 also has a forward rotation position 44a, a stop position 44b, and a reverse rotation position 44c.
It has.

The lifting hydraulic motor 4 is connected so that hydraulic oil is supplied from the other variable displacement pump P2 via the switching valve 38. Variable displacement pump P2
A flow control valve 42 is disposed between the control valve 38 and the switching valve 38. The switching valve 38 includes an ascending position 38a, a stopping position 38b,
A lowering position 38c is provided.

Next, the operation of the hydraulic device of the construction machine according to this embodiment will be described. The internal combustion engine 1 drives both the variable displacement pumps P1 and P2 and the constant displacement pump P3. First, the switching valves 32 and 44 are moved to the normal rotation positions 32a and 44a.
, Hydraulic oil is supplied from one of the variable displacement pumps P1 and the constant displacement pump P3 to the construction hydraulic motor 2 via the switching valves 32 and 44. Thus, the application tool 56 is rotationally driven via the speed reducer 54. When the switching valve 38 is switched to the lower position 38a, the hydraulic oil is supplied from the other variable displacement pump P2 to the hydraulic motor 4 for raising and lowering.
Supplied to Thereby, the application tool 56 descends.

As shown by a thick solid line and a thin solid line in FIG.
Due to the discharge pressure from the other variable displacement pump P2, the pump control line of the merge of the one variable displacement pump P1 and the constant displacement pump P3 shifts as shown by the arrow. While the discharge pressure of the other variable displacement pump P2 is constant, the discharge amount of the merge of the one variable displacement pump P1 and the constant displacement pump P3 is changed by the one variable displacement pump P1. Since the discharge amount from the pump P3 does not change, even if the pressure increases, that is, even if the load increases, the drop in the discharge amount is small, and the decrease in the number of revolutions of the application tool 56 is also small. Is also small. In particular, when the application tool 56 is a stirring blade, a change in the number of revolutions greatly affects the construction quality, but a change in the number of revolutions due to a change in load is small, and the change in quality can be suppressed.

As shown by a thin broken line in FIG. 2, the discharge amount of the other variable displacement pump P2 is
Shift by pressure of 3. Therefore, even when the supply to the lifting hydraulic motor 4 is controlled by the flow control valve 42, the discharge amount of the variable displacement pump P2 is reduced, the amount of hydraulic oil returned to the hydraulic tank 36 is small, and energy efficiency is reduced. Thus, overheating of the internal combustion engine 1 can be prevented.

The present invention is not limited to such an embodiment at all, and can be implemented in various modes without departing from the gist of the present invention.

[0027]

As described in detail above, in the hydraulic device of the construction machine of the present invention, even if the load increases, the drop in the discharge amount is small and the decrease in the number of revolutions of the tool is small. Is also small. Further, the amount of hydraulic oil returned to the hydraulic tank is small, energy efficiency is improved, and overheating of the internal combustion engine can be prevented.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic device of a construction machine as one embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a discharge amount and a discharge pressure of each pump of the embodiment.

FIG. 3 is a hydraulic circuit diagram of a hydraulic device of a conventional construction machine.

FIG. 4 is a schematic configuration diagram of a double variable displacement pump.

FIG. 5 is a graph showing a relationship between a discharge amount and a discharge pressure of each conventional pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Construction hydraulic motor 4 ... Elevating hydraulic motor 12 ... Swash plate 18 ... Spindle 32, 38, 44 ... Switching valve 34, 40, 46 ... Relief valve 42 ... Flow control valve 48 ... Variable throttle 50 ... Relief valve 54 ... Reducer 56 ... Tool 58 ... Drive mechanism 60 ... Elevating mechanism P1 ... Variable displacement pump P2 ... Variable displacement pump P3 ... Constant displacement pump

Continued on front page F-term (reference) 2D003 AA01 AB05 BA05 BB02 CA04 CA09 3H089 AA27 BB01 CC08 DA02 DA03 DA08 DA13 DB03 DB12 DB47 DB49 JJ01

Claims (3)

[Claims] 1. A hydraulic pump driven by an internal combustion engine of a construction machine having a drive mechanism for rotating and driving an application tool by a hydraulic motor for construction, and a lifting mechanism for raising and lowering the drive mechanism by a hydraulic motor for elevation. In a hydraulic device for a construction machine that supplies hydraulic oil to the construction hydraulic motor and the lifting hydraulic motor, the hydraulic pump includes a double variable displacement pump and a constant displacement pump, A hydraulic oil is supplied to the construction hydraulic motor from a pump and the constant displacement pump, and hydraulic fluid is supplied to the lifting hydraulic motor from the other variable displacement pump via a flow control valve. Hydraulic equipment for construction machines. 2. The hydraulic device for a construction machine according to claim 1, wherein the two variable displacement pumps are swash plate type plunger pumps and share a swash plate. 3. The hydraulic device for a construction machine according to claim 1, wherein a discharge amount of the constant displacement pump is smaller than a maximum discharge amount of the variable displacement pump.