JPH0238078Y2 - - 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 that automatically lowers the engine speed when all work implement levers are set to neutral.

FIG. 2 shows a schematic configuration of the conventional auto-deceleration mechanism, including switching valves a, b, and c that switch and control actuators for swing, arm, boom, bucket, and travel. ,d,e
When all of the The engine is designed to rotate 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 neutral, and a small amount of pressure oil will be drawn 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.

Furthermore, when there are many actuators, many detectors are required to detect the neutral state of each actuator, which complicates the detection mechanism and poses problems in reliability and maintainability.

Means and actions for solving the problem The invention was made in consideration of the above,
A pressure switch installed on the input side of the variable displacement hydraulic pump control device is connected to the switching drive part of the deceleration mechanism installed in the engine's fuel control system, and the operating pressure of the control device is lowered to reduce the discharge amount of the hydraulic pump. When it gets low, a deceleration mechanism is activated by a pressure switch.

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 66 such as a swash plate is controlled by a control device 7. The control device 7 controls the pressure from the first discharge path 8a of the control pump 3, a variable torque control valve 9, and a cut-off valve 1 on the way.
0 and the pressure from 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 loose spring device 14 are connected by a link 16, and the middle part of this link 16 is connected to the base end of the loose spring device 14. 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. Reference numeral 20 denotes an electromagnetic force acting portion of the electromagnetic switching valve 19, and the switching valve 19 is turned on by being energized.

On the other hand, the above neutral control valve 11
A pressure switch 21 is connected to the discharge passage 8b that connects the hydraulic pressure chamber 7a of the control device 7 and the hydraulic pressure chamber 7a of the control device 7. An electromagnetic action section 20 of the valve 19 is connected to a controller 22 . 23 is a manual switch.

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 output pressure of the neutral control valve 11 becomes low, the pressure switch 21 is turned ON, energizing the electromagnetic force action section 20 of the electromagnetic switching valve 19, which turns ON, and pressure oil is supplied to the deceleration cylinder 15 from the control pump 3. is supplied, the control lever 12 is returned to the deceleration position against the loose spring device 14, the engine 1 is brought into the deceleration state, and the rotational speed is 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 through 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.

Also, turn on and off the manual switch 23.
By doing this, you can arbitrarily select between auto-deceleration and auto-deceleration. In addition, by incorporating a timer in the controller 22 in the electric circuit to delay the deceleration ON signal and respond immediately to the OFF signal, the engine rotation when the switching valve of the work equipment passes through neutral during actual work You can eliminate down.

Effects of the invention According to the invention, the variable displacement main pump 2
Since the deceleration mechanism is turned ON and OFF by fluctuations in the hydraulic pressure of the control device 7 that controls the deceleration mechanism, there is no mechanical operation in the mechanism that turns the deceleration mechanism ON and OFF, and only one pressure switch 21 is required. It can be made extremely simple, and reliability and durability can be improved.

In addition, even when the switching valve is operated slightly and the actuator is slightly operated, the deceleration operation is performed.
Loss in the rotation system during light work can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 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, and 21 is a pressure switch.

Claims (1)

[Scope of utility model registration request] 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 fully rotating state to the deceleration position, and also controls the control members of the control device 7 of the variable displacement hydraulic pump. A pressure switch 21 is provided in the hydraulic circuit connected to the side hydraulic chamber, and the pressure switch 21 is turned on when the pressure in the hydraulic circuit falls below a predetermined pressure.
An engine control device for a machine equipped with a variable displacement hydraulic pump, characterized in that 1 is connected to a switching drive section of the deceleration mechanism.