JPH09126150A - Hydraulic pump control device for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control corresponding to a variation in the atmospheric pressure with the use of an economical device without using expensive electric control so as to set a torque of a hydraulic pump in a construction machine. SOLUTION: A pressure at 1atm. is charged in a bell-like container which is expandable and contractible under the atmospheric pressure, having a stationary one end 14a and the other end 14b made into contact with the opened side 13a of a pressure reducing valve 13 in which a spool is displaced in response to expansion and contraction of the container 14 so as to change a secondary pressure. That is, when the atmospheric pressure lowers, the container 14 expands so that the secondary pressure of the pressure reducing valve 13 becomes higher so as to energize a regulator 11. Accordingly, the set torque of the hydraulic pump 11 is lowered, thereby it is possible to reduce a load to an engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic pump control device for a construction machine, and more particularly to a hydraulic pump control device that responds to changes in atmospheric pressure.

[0002]

2. Description of the Related Art There is known a construction machine such as a hydraulic excavator that electrically sets a torque of a hydraulic pump by engine speed sensing control, but requires an expensive device. In recent years, a device that adjusts the set torque of a hydraulic pump without performing electrical control has also been used.

When no electrical control is performed,
In order to deal with overload due to the response delay of the hydraulic pump, the set torque of the hydraulic pump is set slightly lower than the rated output shaft torque of the engine.

[0004]

Conventionally, a hydraulic pump control device for a construction machine of this type has a low set torque of the hydraulic pump with respect to the rated output shaft torque of the engine, but it is used in places with low atmospheric pressure, such as in highlands. In this case, the output of the engine itself decreases and it is easy to stall, so it is necessary to set the set torque even lower. However, if the set torque of the hydraulic pump is set too low, the operating efficiency on general flat ground will deteriorate.

Therefore, there arises a technical problem to be solved in order to control the hydraulic pump in response to the change in atmospheric pressure by an inexpensive device without using expensive electric control. Aims to solve this problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above object, and is provided with a bellows-shaped hermetically sealed container whose inside is hermetically sealed at 1 atm and is expandable and contractable under atmospheric pressure. The expansion pressure of the pressure reducing valve is adjustable by expansion and contraction of the hermetically sealed container, and the secondary pressure of the pressure reducing valve is applied to the regulator of the hydraulic pump. An air pump adjusted to 1 atm is provided, the discharge pressure of the air pump is introduced into the bottom port of the single rod double acting cylinder, and the atmospheric pressure is introduced into the top port of the double acting cylinder. Provided is a hydraulic pump control device for a construction machine in which the secondary pressure of a pressure reducing valve is adjustable by expansion and contraction of the double-acting cylinder type rod, and the secondary pressure of the pressure reducing valve is applied to a regulator of the hydraulic pump. Thing .

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a hydraulic pump control device according to a first aspect of the present invention, wherein the hydraulic pump 10 is a regulator 1.
The tilt angle is changed by 1 and the discharge amount of oil supplied from the hydraulic pump 10 to the circuit is controlled. The signal pressure to the regulator 11 is input from the hydraulic pressure source 12 via the pressure reducing valve 13.

On the other hand, reference numeral 14 is a bellows-shaped hermetic container, the inside of which is hermetically sealed at 1 atm and is expandable and contractable under atmospheric pressure. One end 14 of the sealed container 14
While fixing a, the other end 14b of the sealed container 14 is brought into contact with the open side 13a of the pressure reducing valve 13.

Here, FIG. 2 shows the relationship between the engine speed and the output shaft torque, and the output shaft torque becomes maximum at the rated point T. Normally, in order to prevent overload due to the response delay of the hydraulic pump 10, the regulator 11 is initially set so that the set torque of the hydraulic pump 10 is a point A slightly lower than the rated point T, and the pressure reducing valve at this time is set. Thirteen
The state of is the initial state.

Thus, when the hydraulic pump 10 is operating and the atmospheric pressure is 1 atm, the sealed container 14 is shown in FIG.
, The pressure reducing valve 13 maintains the initial state, the regulator 11 does not change, and the hydraulic pump 10
The set torque of is the same as point A described above.

[0011] Now, in high altitudes where the atmospheric pressure is lower than 1 atm, the pressure inside the sealed container 14 causes the sealed container 14 to expand and expand, and the spool of the pressure reducing valve 13 is pressed to the open side. Therefore, as the sealed container 14 extends, the pressure reducing valve 1
The opening area of 3 changes, the secondary pressure gradually increases, and the signal pressure acting on the regulator 11 from the hydraulic power source 12 increases. That is, the set torque of the hydraulic pump 10 becomes a point B lower than the point A on the graph of FIG. 2, and the engine load is reduced and the engine stall is prevented in a place where the atmospheric pressure is low.

When the atmospheric pressure returns to 1 atm again, the pressure around the sealed container 14 causes the sealed container 14 to move.
Is pressed and contracted, the pressure reducing valve 13 returns to the initial state, and the regulator 11 returns to the initial setting. That is, the set torque of the hydraulic pump 10 returns to the first point A.

As described above, the set torque of the hydraulic pump 10 rises and falls according to the change of the atmospheric pressure, so that the set torque of the hydraulic pump does not become too low with respect to the rated output shaft torque of the engine, and it can be maintained on a level ground. It is possible to prevent a decrease in the operating efficiency of.

FIG. 3 shows a hydraulic pump control device according to a second aspect of the present invention. The same components as those in FIG. In the figure, reference numeral 15 is an air pump, which is adjusted by a pressure control valve 16 so that the discharge pressure is always 1 atm.

Reference numeral 17 denotes a single rod type double acting cylinder, which introduces the discharge pressure of the air pump 15 into a port 17a on the bottom side of the double acting cylinder 17 and at the top side of the double acting cylinder 17. Atmospheric pressure is introduced into the port 17b. The rod 17c of the double-acting cylinder 17 is a spring 17
The rod 1 is urged toward the bottom by d.
The tip of 7c is brought into contact with the open side 13a of the pressure reducing valve 13.

When the hydraulic pump 10 is operating and the atmospheric pressure is 1 atm, the rod 17c of the double-acting cylinder 17 is in a depressed state, and the pressure reducing valve 13 maintains the initial state. As a result, the regulator 11 does not change, and the set torque of the hydraulic pump 10 remains at the point A described above.

Now, in a place where atmospheric pressure such as high altitude is lower than 1 atm, the port 17a on the bottom side of the double-acting cylinder 17 is used.
Becomes higher than the port 17b on the top side, and the spring 17d
The rod 17c projects against the pressing force of, and the spool of the pressure reducing valve 13 is pressed toward the open side. Therefore, the rod 17
With the protrusion of c, the opening area of the pressure reducing valve 13 changes and the secondary pressure gradually increases.
The signal pressure acting on 1 increases. That is, as described above, the set torque of the hydraulic pump 10 becomes a point B lower than the point A on the graph of FIG. 2, and the engine load is reduced in a place where the atmospheric pressure is low to prevent engine stall.

When the atmospheric pressure returns to 1 atm again, the bottom side port 17a of the double-acting cylinder 17 becomes the same pressure as the top side port 17b, and the rod 17c is urged by the spring 17d. The pressure reducing valve 13 is returned to its initial state by being pushed into the regulator 11
Returns to default settings. That is, the set torque of the hydraulic pump 10 returns to the first point A.

Although not shown in the drawings, the double-acting cylinder 17 should not be limited to a single rod type, but may be a double rod type. Therefore, the present invention can be variously modified without departing from the spirit of the present invention, and it is a matter of course that the present invention covers the modifications.

[0020]

As described above, according to the present invention, the secondary pressure of the pressure reducing valve can be adjusted according to the change of the atmospheric pressure, and the set torque is increased or decreased by controlling the regulator of the hydraulic pump. The set torque of the hydraulic pump is not made too low with respect to the rated output shaft torque, and the operating efficiency on a level ground can be improved.

Further, the cost of the hydraulic pump can be reduced because the hydraulic pump is controlled in response to the change of the atmospheric pressure by the inexpensive device without using the expensive electric control.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the invention according to claim 1 and showing a hydraulic pump control device for a construction machine.

FIG. 2 is a graph showing the relationship between engine speed and output shaft torque.

FIG. 3 is a circuit diagram showing an embodiment of the invention according to claim 2 and showing a hydraulic pump control device for a construction machine.

[Explanation of symbols]

 10 Hydraulic Pump 11 Regulator 12 Hydraulic Source 13 Pressure Reducing Valve 14 Sealed Container 15 Air Pump 16 Pressure Control Valve 17 Double Acting Cylinder 17a Bottom Port 17b Top Port 17c Rod 17d Spring

Claims (2)

[Claims] 1. A bellows-shaped sealed container whose inside is sealed at 1 atm and is expandable and contractable under atmospheric pressure, and the secondary pressure of a pressure reducing valve can be adjusted by expanding and contracting the sealed container. A hydraulic pump control device for a construction machine, wherein the secondary pressure of a pressure reducing valve is applied to a regulator of a hydraulic pump. 2. An air pump whose discharge pressure is constantly adjusted to 1 atm is provided, and the discharge pressure of the air pump is introduced into the bottom side port of the single rod type double acting cylinder, and the top side of the double acting cylinder is also provided. Introducing atmospheric pressure to the port,
A hydraulic pump control for a construction machine, characterized in that the secondary pressure of the pressure reducing valve can be adjusted by expanding and contracting the double-acting cylinder type rod, and the secondary pressure of the pressure reducing valve acts on the regulator of the hydraulic pump. apparatus.