JP2875724B2 - Hydraulic drive of hydraulic working machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive unit provided in a hydraulic working machine such as a mini excavator and having an air conditioner powered by an engine.

[0002]

2. Description of the Related Art FIG. 3 shows a hydraulic drive device provided in a conventional hydraulic working machine, for example, a mini excavator having a horsepower of 50 hp or less. The hydraulic drive device shown in FIG. 3 includes an engine 1, a variable displacement hydraulic pump driven by the engine 1, that is, main pumps 2, 3, a pilot pump 4 driven in synchronization with the main pumps 2, 3, and Actuators driven by pressure oil discharged from the main pumps 2 and 3, that is, a hydraulic motor 6 such as a swing motor, a hydraulic cylinder 7 such as a boom cylinder, an arm cylinder, and a bucket cylinder, and a pilot pump 4
A control valve 5 for controlling the flow of pressure oil supplied from the main pumps 2 and 3 to actuators such as a hydraulic motor 6 and a hydraulic cylinder 7, and tilting of the main pumps 2 and 3 The tilt control device 10 for controlling the angle, the control lines 8 and 9 for guiding the discharge pressures of the main pumps 2 and 3 to the tilt control device 10 as control pressure, and the tilt angles of the main pumps 2 and 3 are set. A spring 11 for providing a return force in the direction of minimization.

In such a hydraulic drive, the engine 1
To operate the main pumps 2 and 3 and the pilot pump 4
Is driven, the discharge pressures of the main pumps 2 and 3 are supplied as control pressure to the tilt control device 10 via the control pipes 8 and 9. The tilt control device 10 controls the tilt angles of the main pumps 2 and 3 against the force of the spring 11 according to the magnitude of the control pressure. In such a state, when the control valve 5 is switched by operating means such as a pilot operation valve (not shown), the pressure oil of the main pumps 2 and 3 is transmitted through the control valve 5 to the hydraulic motor 6 or the hydraulic cylinder 7.
And a revolving body, a boom, an arm, and a bucket (not shown) are driven by driving these actuators, and a desired excavation operation and the like are performed. These days,
Even with such a mini excavator having a power of 50 horsepower or less, it is demanded to provide an air conditioner such as an air conditioner or a cooler. The air conditioner is operated by operating a switch. The operation of this air conditioner usually requires a few horsepower.

[0004]

In the above-mentioned prior art, there is a problem that the engine 1 for driving the main pumps 2 and 3 and the pilot pump 4 is used as a power source of the air conditioner.

That is, when an actuator such as a hydraulic motor 6 or a hydraulic cylinder 7 is driven to perform an excavation operation or the like while operating an air conditioner of a few horsepower with an engine 1 of 50 horsepower or less, basically the horsepower is reduced. Since there is no allowance, engine stall tends to occur when the load pressure of the actuator increases. When such an engine stall occurs, workability is reduced and driving becomes difficult.

In view of the above, conventionally, in order to prevent the occurrence of engine stall, the cracking pressure at which the control valve 5 is switched is set to be 10 to 2 times smaller than a normal set value in advance.
Countermeasures are taken such as setting the tilt angle of the main pumps 2 and 3 to be smaller by about 0% or setting the tilt angle of the main pumps 2 and 3 to a predetermined angle smaller in advance. However, such an engine stall countermeasure is effective in preventing engine stall in the operating state of the air conditioner. However, in the non-operation state of the air conditioner, it is possible to sufficiently obtain the force and speed of the actuator which should be obtained originally. Since the actuator cannot be used, there is a problem in that the actuator is insufficient in power and speed, and improvement in working efficiency cannot be basically expected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances in the prior art, and has as its object to prevent the occurrence of engine stall when the air conditioner operates, and to provide a sufficient actuator when the air conditioner is not operating. It is an object of the present invention to provide a hydraulic drive device of a hydraulic working machine that can secure force and speed.

[0008]

In order to achieve this object, according to the embodiment shown in FIG. 1, the present invention relates to an engine 1 and a variable displacement hydraulic pump driven by the engine 1, The vehicle includes main pumps 2 and 3, actuators driven by pressure oil discharged from these main pumps 2 and 3, for example, a hydraulic motor 6 and a hydraulic cylinder 7, and an air conditioner using the engine 1 as a power source, for example, an air conditioner 13. At the same time, tilt angle reduction control means for forcibly reducing the tilt angle of the main pumps 2 and 3 in a driven state, for example, an electromagnetically driven tilt control device for controlling the tilt angle of the main pumps 2 and 3 And an electromagnetically driven tilt control device 12 and an air conditioner 13.
And a switch 14 for interlocking the two.

[0009]

According to the present invention having the above-described structure, when the air conditioner 13 is not driven, that is, when the switch 14 is not operated, the electromagnetically driven tilt control device 12 operates in a normal manner in a mini excavator without an air conditioner. It functions in the same way as the tilt control device, so that the tilt angle can be controlled according to the discharge pressure of the main pumps 2 and 3 until a predetermined maximum tilt angle is reached, and the hydraulic motor 6 or the hydraulic cylinder 7 is made sufficiently large. It can be driven by force and fast enough.
When the air conditioner 12 is driven, that is, when the switch 14 is operated, the air conditioner 12 is operated, and the electromagnetically driven tilt control device 12 is operated. Control for reducing the turning angle by a predetermined angle is performed. By reducing the tilt angle, the input torque of the main pumps 2 and 3 is controlled so as not to exceed the output torque of the engine 1 which has been changed so as to decrease with the driving of the air conditioner 13, thereby preventing the occurrence of engine stall. Can be.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a hydraulic drive device for a hydraulic working machine according to the present invention. FIG. 1 is a circuit diagram showing one embodiment of the present invention applied to a mini excavator, and FIG. 2 is a diagram showing characteristics obtained in the embodiment shown in FIG. FIG. 1 showing this embodiment is drawn corresponding to FIG. 3 described above.
Are denoted by the same reference numerals.

That is, even in the embodiment shown in FIG.
An engine 1, a variable displacement hydraulic pump driven by the engine 1, ie, main pumps 2, 3, a pilot pump 4, and an actuator driven by hydraulic oil discharged from the main pumps 2, 3, ie, a swing motor, etc. Hydraulic motor 6, hydraulic cylinders 7 such as a boom cylinder, an arm cylinder, and a bucket cylinder, and a control valve 5 for controlling the flow of hydraulic oil supplied to actuators such as the hydraulic motor 6 and the hydraulic cylinder 7.
Control pipes 8 and 9 for guiding the respective discharge pressures of the main pumps 2 and 3 as control pressures; and a spring 11 for providing a return force in a direction to minimize the tilt angle of the main pumps 2 and 3. I have.

In this embodiment, in particular, an electromagnetically driven tilt control device 12 is provided as a tilt control device for controlling the tilt angle of the main pumps 2, 3 according to the control pressures given by the control lines 8, 9. It is. This electromagnetically driven tilt control device 1
Numeral 2 has a control function equivalent to a tilt control function in a normal tilt control device, that is, a tilt control device provided in a mini shovel without an air conditioner, when not excited.
That is, it has a function of controlling the tilt angle directly depending on the magnitude of the control pressure given by the control lines 8 and 9. At the time of excitation, the control pressure provided by the control lines 8 and 9 is limited to a smaller pressure by the movement of the spool provided therein, and the tilt angle of the main pumps 2 and 3 is reduced by a predetermined angle. Has functions.
The electromagnetically driven tilt control device 12 constitutes a tilt angle reduction control means for forcibly reducing the tilt angle of the main pumps 2 and 3 in a driven state by a predetermined angle.

In this embodiment, an air conditioner, for example, an air conditioner 13 is provided, and a switch 14 for interlocking the air conditioner 13 with an electromagnetically driven tilt control device 12 is provided.
A power supply 15 for the switch 14 is provided.

The operation of this embodiment is as follows.
The operation when the air conditioner 13 is not operated and the switch 14 is not operated is the same as the above-described conventional technology shown in FIG. That is, when the main pumps 2 and 3 and the pilot pump 4 are driven by operating the engine 1, the discharge pressure of the main pumps 2 and 3 is controlled by the electromagnetically driven tilt control device 12 via the control lines 8 and 9. Given as pressure. The electromagnetically driven tilt control device 12 controls the magnitude of the control pressure,
The tilt angle of the main pumps 2, 3 is controlled while resisting the force of the spring 11. That is, the tilt angle is controlled depending on the magnitude of the control pressure provided by the control lines 8 and 9 itself. At this time, the electromagnetically driven tilt control device 12 functions in the same manner as the tilt control function of the tilt control device provided in the mini excavator not provided with the air conditioner, and accordingly, the tilt angle becomes a predetermined maximum tilt angle. Can be controlled.
When the control valve 5 is switched from such a state by operating means such as a pilot operating valve (not shown),
The hydraulic oil of the main pumps 2 and 3 is supplied to the hydraulic motor 6 or the hydraulic cylinder 7 via the control valve 5,
These hydraulic motors 6 or hydraulic cylinders 7 can secure a large force and a speed corresponding to the above-mentioned maximum tilt angle, and a revolving body, a boom, an arm, and a bucket (not shown) in accordance with the operation of these actuators. Is driven, and a desired excavation operation or the like is performed.

The characteristic line 20 of FIG. 2 shows the output torque characteristic of the engine 1 when the air conditioner 13 is not operated as described above. At this time, the input torque characteristic lines of the main pumps 2 and 3 are points A, B and The characteristic is drawn along the line C and is located below the characteristic line 20, and no engine stall occurs.

When the switch 14 is operated,
When the air conditioner 13 is operated, the electromagnetically driven tilt control device 12 is excited, and as described above, the electromagnetically driven tilt control device 12 is given by the control lines 8 and 9 by moving the spool provided therein. The control pressure is limited to a smaller pressure, and the tilt angle of the main pumps 2 and 3 is controlled to decrease by a predetermined angle from the previous tilt angle, for example, a predetermined maximum tilt angle.

The characteristic line 21 in FIG. 2 shows the output characteristic of the engine 1 at this time, and the output is lower than the characteristic line 20 due to the driving of the air conditioner 13. At this time, the input torque characteristic lines of the main pumps 2, 3 are changed to points D, E, F in FIG. It shifts to the form that follows. Accordingly, although the power and speed of the hydraulic motor 6 and the hydraulic cylinder 7 are slightly reduced as compared with the case where the air conditioner 13 is not used, the points D and
E and F are located below the characteristic line 21 of the engine 1, that is, are controlled so as not to exceed the output torque of the engine 1, which has changed so as to decrease with the driving of the air conditioner 13, thereby generating an engine stall. Can be prevented.

As described above, in the present embodiment, it is possible to prevent the occurrence of engine stall during the operation of the air conditioner 13, and
When the air conditioner 13 is not operating, it is possible to secure sufficient hydraulic motor 6 and hydraulic cylinder 7 power and speed,
Work efficiency can be improved.

Although the air conditioner 13 has been described as an air conditioner in the above embodiment, it may be a cooler.

In addition to the configuration of the above-described embodiment, for example, a temperature sensor is provided near the driver's seat, and when the temperature sensor detects a predetermined temperature while the air conditioner 13 is operating, the switch 14 is automatically turned off. While the air conditioner 13 is stopped, the electromagnetically driven tilt control device 12 is de-energized,
The tilt angles of the main pumps 2 and 3 may be controlled to a predetermined maximum tilt angle.

[0021]

According to the present invention having the above-described structure, it is possible to prevent the occurrence of engine stall during the operation of the air conditioner and to secure a sufficient force and speed of the actuator when the air conditioner is not operating. As a result, the working efficiency of the hydraulic working machine provided with the hydraulic drive device can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention applied to a mini excavator.

FIG. 2 is a diagram showing characteristics obtained in the embodiment shown in FIG.

FIG. 3 is a circuit diagram showing an example of a conventional hydraulic drive device of a hydraulic working machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Main pump (variable displacement hydraulic pump) 3 Main pump (variable displacement hydraulic pump) 4 Pilot pump 5 Control valve 6 Hydraulic motor (actuator) 7 Hydraulic cylinder (actuator) 8 Control line 9 Control line 11 Spring 12 Electromagnetic Drive type displacement control device (displacement angle reduction control means) 13 Air conditioner (air conditioner) 14 Switch 15 Power supply

Continued on the front page (72) Koji Nishimura, Inventor 650, Kandamachi, Tsuchiura-shi, Ibaraki Pref. Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (72) Inventor Noboru Toda 269-5 Nishiota, Oda, Yoshida-cho, Nishikanbara-gun, Niigata Prefecture

Claims (2)

(57) [Claims] 1. An engine, a variable displacement hydraulic pump driven by the engine, an actuator driven by pressure oil discharged from the variable displacement hydraulic pump,
A hydraulic drive device for a hydraulic working machine, comprising: an air conditioner powered by the engine; and a tilt angle reduction control means for forcibly reducing a tilt angle of the variable displacement hydraulic pump in a driven state by a predetermined angle. A hydraulic drive device for a hydraulic working machine, further comprising a switch for interlocking the tilt angle reduction control means with the air conditioner. 2. A hydraulic working machine according to claim 1, wherein said tilt angle decrease control means is an electromagnetically driven tilt control device for controlling the tilt angle of said variable displacement hydraulic pump. Drive.