JPH07133620A - Hydraulic drive system for hydraulic work machine - Google Patents

Abstract

(57) [Abstract] [Purpose] A hydraulic drive system for a hydraulic working machine capable of preventing engine stall during operation of an air conditioner and ensuring sufficient actuator force and speed when the air conditioner is not operating. Offer of. [Structure] Engine 1 and variable displacement hydraulic pumps driven by the engine 1, that is, main pumps 2 and 3
And an actuator driven by pressure oil discharged from these main pumps 2, 3, for example, a hydraulic motor 6,
A tilt angle reduction control means that includes a hydraulic cylinder 7 and an air conditioner that uses the engine 1 as a power source, such as an air conditioner 13, and that forcibly decreases the tilt angles of the main pumps 2 and 3 that are in a driven state. Main pumps 2, 3
An electromagnetically driven tilting control device 12 for controlling the tilting angle is provided, and a switch 14 for interlocking the electromagnetically driven tilting control device 12 and the air conditioner 13 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system equipped with a hydraulic working machine such as a mini excavator and having an air conditioner using an engine as a power source.

[0002]

2. Description of the Related Art A conventional hydraulic working machine, for example, a hydraulic drive system provided in a mini excavator having a horsepower of 50 horsepower or less is shown in FIG. The hydraulic drive system shown in FIG. 3 includes an engine 1, a variable displacement hydraulic pump driven by the engine 1, that is, main pumps 2 and 3, and a pilot pump 4 that is driven in synchronization with the main pumps 2 and 3. An actuator 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.
The tilting of the main pumps 2 and 3 and the control valve 5 that controls the flow of pressure oil that is switched by the pilot pressure discharged from the main pumps 2 and 3 to the actuators such as the hydraulic motor 6 and the hydraulic cylinder 7. The tilting control device 10 for controlling the angle, the control conduits 8 and 9 for guiding the respective discharge pressures of the main pumps 2 and 3 to the tilting control device 10 as control pressures, and the tilting angles of the main pumps 2 and 3. And a spring 11 that provides a restoring force in a direction that minimizes it.

In such a hydraulic drive system, the engine 1
To operate the main pumps 2, 3 and the pilot pump 4
When is driven, the discharge pressure of the main pumps 2 and 3 is given to the tilting control device 10 as control pressure via the control pipe lines 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. From this state, when the control valve 5 is switched by operating means such as a pilot operating valve (not shown), the pressure oil of the main pumps 2 and 3 is transferred via the control valve 5 to the hydraulic motor 6 or the hydraulic cylinder 7.
Is supplied to the revolving structure, and a revolving body (not shown), a boom, an arm, or a bucket is driven in accordance with the driving of these actuators, and a desired excavation work or the like is performed. These days
Even such a mini excavator having 50 horsepower or less is required to be equipped with an air conditioner such as an air conditioner or a cooler. In such an excavator equipped with such an air conditioner, the engine 1 is used as a power source and a predetermined power source is provided. The air conditioner is operated by operating the switch. It should be noted that the operation of this air conditioner usually requires a few horsepower.

[0004]

The above-mentioned conventional technique has a problem associated with using the engine 1 for driving the main pumps 2, 3 and the pilot pump 4 as the 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 excavation work while operating an air conditioner of a few horsepower with an engine 1 of 50 horsepower or less, horsepower is basically increased. Since there is no margin, engine stall is likely to occur when the load pressure on the actuator increases. When such an engine stall occurs, workability is deteriorated and driving becomes difficult.

For this reason, conventionally, in order to prevent the occurrence of engine stall, the cracking pressure for switching the control valve 5 is set in advance to 10 to 2 more than the normal set value.
Measures have been taken such as setting the tilt angle of the main pumps 2 and 3 to be small by about 0%, or reducing the tilt angle of the main pumps 2 and 3 by a predetermined angle. However, such an engine stall countermeasure is effective for preventing engine stall in the operating state of the air conditioner, but when the air conditioning system is not operating, it is possible to obtain sufficient actuator force and speed that should be obtained. Since this is not possible, there is a problem that the efficiency of the actuator is insufficient and the speed is insufficient, so that basically improvement in work efficiency cannot be expected.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to prevent the occurrence of engine stall during operation of the air conditioner and to provide sufficient actuator operation when the air conditioner is not in operation. An object of the present invention is to provide a hydraulic drive system for a hydraulic working machine capable of ensuring power and speed.

[0008]

To achieve this object, the present invention will be described with reference to the embodiment shown in FIG. 1. The engine 1 and a variable displacement hydraulic pump driven by the engine 1, that is, It is provided with main pumps 2 and 3, an actuator 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, such as an air conditioner 13. At the same time, a tilt angle reduction control means for forcibly reducing the tilt angle of the main pumps 2, 3 in a driven state, for example, an electromagnetic drive type tilt control device for controlling the tilt angles of the main pumps 2, 3. 12, the electromagnetically driven tilt control device 12 and the air conditioner 13 are provided.
The switch 14 for interlocking with and is provided.

[0009]

According to the present invention having the above-described structure, the electromagnetically driven tilt control device 12 operates normally when the air conditioner 13 is not driven, that is, when the switch 14 is not operated. It functions in the same manner as the tilt control device, and therefore the tilt angle can be controlled according to the discharge pressure of the main pumps 2 and 3 until it reaches a predetermined maximum tilt angle, and the hydraulic motor 6 or the hydraulic cylinder 7 is 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 tilting control device 12 is operated. The electromagnetically driven tilting control device 12 causes the tilting of the main pumps 2, 3. Control is performed to reduce the turning angle by a predetermined angle as compared to that time. Due to this decrease in 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 that is changed so as to become smaller as the air conditioner 13 is driven, and the occurrence of engine stall is prevented. You can

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive system for a hydraulic working machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention applied to a mini excavator, and FIG. 2 is a diagram showing characteristics obtained by the embodiment shown in FIG. FIG. 1 showing the present embodiment is drawn corresponding to FIG. 3 described above.
The same parts as those shown in are indicated by the same reference numerals.

That is, even in the embodiment shown in FIG.
Engine 1, variable displacement hydraulic pump driven by this engine 1, that is, main pumps 2 and 3, pilot pump 4, and actuator driven by pressure oil discharged from main pumps 2 and 3, that is, swing motor, etc. Hydraulic motor 6, a hydraulic cylinder 7 such as a boom cylinder, an arm cylinder, and a bucket cylinder, and a control valve 5 for controlling the flow of pressure oil supplied to actuators such as the hydraulic motor 6 and the hydraulic cylinder 7.
And control lines 8 and 9 for guiding the respective discharge pressures of the main pumps 2 and 3 as control pressures, and a spring 11 that gives a restoring force in a direction that minimizes the tilt angle of the main pumps 2 and 3. There is.

In this embodiment, in particular, an electromagnetic drive type tilting control device 12 is provided as a tilting control device for controlling the tilting angles of the main pumps 2 and 3 in accordance with the control pressure given by the control lines 8 and 9. There is. This electromagnetic drive type tilting control device 1
No. 2 has a control function equivalent to the tilt control function in a normal tilt control device, that is, a tilt control device included in a mini excavator that is not equipped with an air conditioner when not excited.
That is, it has a function of controlling the tilt angle depending on the magnitude of the control pressure given by the control pipes 8 and 9 as it is. Further, at the time of excitation, the control for limiting the control pressure given by the control lines 8, 9 to a smaller pressure by the movement of the spool provided inside and for reducing the tilt angle of the main pumps 2, 3 by a predetermined angle than before. Have a function.
The electromagnetic drive type tilting control device 12 constitutes tilting angle reduction control means for forcibly reducing the tilting angle of the main pumps 2, 3 in the driven state by a predetermined angle.

Further, in this embodiment, an air conditioner, for example, an air conditioner 13 is provided, and a switch 14 for interlocking the air conditioner 13 and the 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 that of the conventional technique shown in FIG. That is, when the engine 1 is operated to drive the main pumps 2 and 3 and the pilot pump 4, the discharge pressure of the main pumps 2 and 3 is controlled by the electromagnetic drive type tilting control device 12 via the control lines 8 and 9. Given as pressure. The electromagnetic drive type tilting control device 12 controls the amount of control pressure according to
The tilt angles of the main pumps 2 and 3 are controlled while resisting the force of the spring 11. That is, the tilt angle is controlled depending on the magnitude of the control pressure given by the control lines 8 and 9. At this time, the electromagnetic drive-type tilting control device 12 functions in the same manner as the tilting control function in the tilting control device included in the mini excavator that is not provided with the air conditioner, and thus the tilting angle up to a predetermined maximum tilting angle. Can be controlled.
From this state, when the control valve 5 is switched by operating means such as a pilot operating valve (not shown),
The pressure 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,
The hydraulic motor 6 or the hydraulic cylinder 7 can secure a large force and speed corresponding to the above-described maximum tilting angle, and a revolving body (not shown), a boom, an arm, or a bucket is accompanied by the operation of these actuators. Is driven, and desired excavation work 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 C, and the characteristic is located below the characteristic line 20, and no engine stall occurs.

When the switch 14 is operated,
As the air conditioner 13 operates, the electromagnetic drive type tilting control device 12 is excited, and as described above, the electromagnetic drive type tilting control device 12 is provided by the control pipe lines 8 and 9 by the movement of the spool provided therein. The control pressure applied to the main pumps 2 and 3 is limited to a smaller pressure, and the tilt angle of the main pumps 2 and 3 is controlled to be smaller than the tilt angle up to that point, for example, a predetermined maximum tilt angle.

The characteristic line 21 of FIG. 2 shows the output characteristic of the engine 1 at this time, and the output is lower than that of 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 and 3 are the points D, E, and F in FIG. 2 due to the forcible tilt angle reduction control of the main pumps 2 and 3 in the electromagnetic drive type tilting control device 12. It shifts to the form according to. Therefore, although the force 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 point D,
E and F are located below the characteristic line 21 of the engine 1, that is, they are controlled so as not to exceed the output torque of the engine 1 which is changed so as to become smaller as the air conditioner 13 is driven. Can be prevented.

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

Although the air conditioner 13 is used as the air conditioner in the above embodiment, it may be a cooler.

In addition to the structure of the above 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 stopping the air conditioner 13, 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]

As described above, according to the present invention, it is possible to prevent the engine from stalling when the air conditioner is operating, and to secure sufficient force and speed of the actuator when the air conditioner is not operating. Therefore, it is possible to improve the work efficiency of the hydraulic working machine provided with the hydraulic drive device, as compared with the related art.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an 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 system for a hydraulic working machine.

[Explanation of symbols]

 1 Engine 2 Main Pump (Variable Capacity Hydraulic Pump) 3 Main Pump (Variable Capacity Hydraulic Pump) 4 Pilot Pump 5 Control Valve 6 Hydraulic Motor (Actuator) 7 Hydraulic Cylinder (Actuator) 8 Control Pipeline 9 Control Pipeline 11 Spring 12 Electromagnetic Drive type tilt control device (tilt angle reduction control means) 13 Air conditioner (air conditioner) 14 Switch 15 Power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Sato, 650 Kintatecho, Tsuchiura City, Ibaraki Prefecture Hitachi Construction Machinery Co., Ltd. Tsuchiura Factory (72) Inventor, Koji Nishimura 650 Kintatecho, Tsuchiura City, Ibaraki Hitachi Construction Machinery Co., Ltd. Ceremony Company Tsuchiura Factory (72) Inventor Noboru Toda 269-5 Nishiota, Yoshida-cho, Nishikanbara-gun, Niigata Prefecture

Claims (2)

[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,
In a hydraulic drive system for a hydraulic working machine including an air conditioner using the engine as a power source, a tilt angle reduction control means for forcibly reducing a tilt angle of the variable displacement hydraulic pump in a driving state by a predetermined angle is provided. A hydraulic drive system for a hydraulic working machine, which is provided with a switch for interlocking the tilt angle reduction control means with the air conditioner. 2. The hydraulic pressure for a hydraulic working machine according to claim 1, wherein the tilt angle reduction control means is an electromagnetic drive type tilt control device for controlling the tilt angle of the variable displacement hydraulic pump. Drive.