JPH037592Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an engine control device for machines such as construction machines equipped with a variable displacement hydraulic pump.

BACKGROUND TECHNOLOGY It is desirable that the rotational speed of an engine that drives a variable displacement hydraulic pump (hereinafter simply referred to as variable pump) be controlled according to the discharge pressure of the variable pump. The speed control is such that the speed is controlled at low speed when not working, and at full speed when working.

This is uneconomical because the engine remains in a full rotation state even in a non-operating state during work, that is, a state in which all the switching valves that control each actuator are set to neutral during work.

For this reason, a so-called auto-deceleration mechanism has been known in which the engine speed is automatically reduced when all work implement levers are set to neutral.

FIG. 3 shows a schematic configuration of the conventional auto-deceleration mechanism. For example, the switching valves a, b, and c control switching actuators for swing, arm, boom, bucket, and traveling actuators. ,d,
When all of e become neutral, the solenoid valve g is energized via the control device f to switch it.
Pressure oil from the control pump i is supplied to the deceleration cylinder h, so that the fuel system of the engine j, which is in a full rotation state, is rotated at a low speed regardless of the position of the fuel adjustment lever k.

Problems to be Solved by the Invention In the engine control system using the conventional auto-deceleration device described above, the auto-deceleration mechanism does not operate unless all the switching valves of each actuator are in neutral, so the engine cannot be rotated at full speed. If you try to make small adjustments to the actuator during operation, the auto deceleration mechanism will not operate because the switching valve is not in neutral, and a small amount of pressure oil will be taken out from the pump while it is still in full rotation, resulting in loss in the rotation system. This was a very common cause of worsening fuel efficiency.

In addition, when there are many actuators, many detectors are required to detect the neutral state of each actuator, making the detection mechanism complicated and reducing reliability.
There were problems with maintainability.

Means and Effects for Solving the Problems The present invention has been developed in view of the above-mentioned problems, and it links the drive section of the deceleration mechanism provided in the fuel control system of the engine to the operation section of the control device of the variable displacement hydraulic pump. The control device operates the deceleration mechanism to reduce engine rotation when the discharge amount of the variable displacement hydraulic pump becomes less than a predetermined amount.

Example An embodiment of the present invention will be described based on FIG.

The engine 1 drives the main pump 2 and the control pump 3, and the discharge path 4 of the main pump 2 has switching valves 5a, 5b for the first, second, and third working machines.
5c are connected in parallel. The main pump 2 is a variable displacement pump, and a displacement control member 6 such as a swash plate is controlled by a control device 7. The control device 7 is a first control device of the control pump 3.
pressure from the discharge passage 8a, a variable torque control valve 9 on the way, and a cut-off valve 10.
It is operated by the pressure difference between the pressure from the second discharge passage 8b and the second discharge passage 8b in which the neutral control valve 11 is interposed.

In the figure, 12 is a control lever that controls the engine control governor 13 of the engine 1, and one end of a loose spring device 14 is connected to the tip of this control lever. The engine 1 stops when the control lever 12 is in the stop position, rotates at low speed when the control lever 12 is in the deceleration position, and rotates at full speed when the control lever 12 is in the full position. Reference numeral 15 denotes a deceleration cylinder loosely connected to the middle part of the control lever 12. The base end of this deceleration cylinder 15 and the base end of the loop spring device 14 are connected by a link 16, and the middle part of this link 16 is connected to the fuel It is connected to a control lever 17.

The hydraulic chamber 18 of the deceleration cylinder 15 is connected to the discharge path of the control pump 3 via an electromagnetic switching valve 19. The electromagnetic force acting portion 20 of the electromagnetic switching valve 19 is connected to a limit switch 22 which is turned on and off by the movement of the operating piston 30 of the control device 7.

The limit switch 22 has a switch lever 23
This switch lever 23 is connected to the control piston 21 via a rod 24, and when the control piston 21 moves in the direction of increasing the discharge amount (leftward in the figure), the limit switch 2
2 is turned OFF, and turned ON when moving in the direction of decreasing discharge amount (rightward in the figure). Further, the electromagnetic switching valve 19 is turned ON when the electromagnetic force acting portion 20 thereof is energized to supply pressure oil to the hydraulic chamber 18 of the decel cylinder 15, and is turned OFF when the energization is cut off. There is.

In the above configuration, the fuel control lever 1
By setting the control lever 7 to the full position, the control lever 12 becomes the full position and the engine 1 is rotated at full speed.

In this state, the switching valve 5a for each work machine,
When 5b, 5c are set to neutral, the switching valves 5a, 5b,
Since the flow rate of the drain circuit 25 from 5c becomes large, the differential pressure between the total pressure of the jet sensor 26 installed in this drain circuit 25 and the static pressure becomes maximum, and this differential pressure causes the spool of the neutral control valve 11 to 27 is moved to the left against the spring 28, and its output port 29 is throttled. As a result, the control hydraulic pressure supplied to this neutral control valve 11 via the variable torque control valve 9 and the cut-off valve 10 is reduced in pressure and output from the output port 29, and the control hydraulic pressure acting on the control device 7 is lowered. . Therefore, the actuating piston 30 of the control device 7, which is controlled by the output pressure of the neutral control valve 11 and the pressure of the control pressure oil from the control pump 3, moves to the right and displaces the displacement control member of the main pump 2. 6 in the direction of decreasing the discharge amount.

When the actuating piston 30 of the control device 7 moves to the right, the limit switch 22 turns on, the electromagnetic switching valve 19 turns on, pressure oil from the control pump 3 is supplied to the deceleration cylinder 15, and the control lever 12 is moved to the loose spring device. 14 and returns to the deceleration position, the engine 1 enters the deceleration state and the rotational speed is automatically reduced.

Furthermore, when one of the switching valves 5a, 5b, 5c is slightly operated, a small amount of hydraulic oil is supplied to the actuator via the switching valve. Due to the large amount of drain oil, an operation similar to the above operation is performed, and the engine 1 enters a deceleration state.

In the above embodiment, by interposing a changeover switch 31 as shown in FIG. 2 in the electric circuit connecting the limit switch 22 and the electromagnetic changeover valve 19, it is possible to arbitrarily select between no auto-deceleration and with auto-deceleration. In addition, a control 32 is inserted in the above electric circuit to activate auto-deceleration (ON).
The OFF signal may be delayed, and the release (OFF) signal may be responded to immediately to eliminate engine rotation down when the switching valve of the work equipment passes through neutral during actual work.

Furthermore, since the variable displacement pump has a structure in which the discharge amount is minimized during high load (relief), the deceleration mechanism is activated when the control device 7 operates to decrease the discharge amount as in the above embodiment. Then,
Since the deceleration mechanism will operate even in the relief state of the highest load, it is necessary to prevent the deceleration operation from occurring in this relief state.

For this reason, as shown in FIG. 2, the inlet circuit 33 of the neutral control valve 11 is provided with a pressure switch 34 that turns off when the inlet circuit 33 becomes below a predetermined pressure.
is installed in the electric circuit connecting the limit switch 22 and the electromagnetic switching valve 19.

According to such a configuration, during relief, no deceleration operation is performed and the engine 1 is rotated at full speed.

In each of the embodiments described above, the limit switch 22 may be directly turned on and off by the operating piston 30 of the control device 7 or the rod 30a connected thereto, or by the displacement control member 6 of the pump 2.

Effects of the invention According to the invention, a variable displacement main pump 1
By making the automatic deceleration operation in conjunction with the control device 7 of Its structure is simpler than that, and its reliability and maintainability are improved.

Furthermore, as described above, according to the present invention, the deceleration operation is performed even when the actuator is slightly operated by slightly operating the switching valve, and it is possible to reduce loss in the rotation system during light work.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing main parts of another embodiment, and FIG. 3 is an explanatory diagram showing a conventional auto-deceleration mechanism. 1 is an engine, 2 is a main pump, 3 is a control pump, 7 is a control device, 15 is a deceleration cylinder, 1
8 is a hydraulic chamber, 9 is an electromagnetic switching valve, 20 is an electromagnetic action section, 22 is a limit switch, and 30 is an operating piston.

Claims (1)

[Claims for Utility Model Registration] A machine equipped with a variable displacement hydraulic pump, in which the fuel control system of the engine 1 that drives the variable displacement hydraulic pump is provided with a deceleration mechanism that returns the fuel control system in a full rotation state to the deceleration position. In the engine control device, the deceleration mechanism is composed of a deceleration cylinder and a piston that fits into the deceleration cylinder and moves by hydraulic pressure acting on a hydraulic chamber to move the fuel control system to the deceleration position. An on/off switching valve is installed in the piping connected to the hydraulic chamber of this deceleration mechanism, and the control device for the variable displacement hydraulic pump has an operating part that controls the discharge amount of the variable displacement hydraulic pump. 1. An engine control device for a machine equipped with a variable displacement hydraulic pump, characterized in that an operating section detecting means for detecting operation in the decreasing direction is provided, and the operating section detecting means is linked to the operating section of the switching valve.