JPH0335859Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention has a function that automatically reduces the engine rotation speed when the engine is running at high speed without load and can select between two stages, and also automatically changes to high speed when the engine is under load. This invention relates to the engine rotation control of a hydraulic excavator that returns to its original position, and can also be applied to bulldozers, wheel loaders, and other construction machines that convert engine horsepower to hydraulic pressure and are driven by this hydraulic pressure.

[Conventional technology]

The conventional mechanism turns the hydraulic cylinder ON and OFF by detecting the pressure of the main hydraulic pump for the work equipment, and when this pressure becomes high, the pilot switching valve in the circuit is switched by the pump pressure, and the hydraulic cylinder circuit is switched to the tank. This device is connected to a port and returns the governor control lever using a spring force contained in a cylinder, and is described in, for example, Japanese Utility Model Application No. 58-156136 to 1987-156140.

[Problem that the invention attempts to solve]

In the case of the above-mentioned conventional technology, when the spool of the control valve is pulled to a certain extent and the actuator such as the cylinder starts to move, pressure is generated in the pump and then the cylinder moves and restarts the engine rotation. As the speed increases, there is a change in speed. Furthermore, if the control valve spool is changed rapidly, the full load will be applied when the engine rotation has not sufficiently started up, which may cause engine drop.

[Means for solving problems]

Focusing on the opening timing of the spool, which supplies oil to the actuator after the spool of the control valve has moved a few mm, it electrically detects that the spool has made a slight stroke, and turns off the hydraulic cylinder before the actuator moves. The engine rotation is then restored, thus eliminating engine drop even when a sudden load is applied.

In addition, the pressure entering the cylinder is controlled by a solenoid valve.
The cylinder stroke is controlled in stages, and the lower rotational speed during no-load is selected in two stages.

[Effect]

A switch detects the movement of the switching lever connected to the control valve spool, and when the engine is in a no-load state, it reduces its rotation speed, and when the engine is loaded, oil flows to the actuator side, causing the switch to operate before the load is applied to the engine. Quickly return the rotation to its initial setting. In addition, the rotation speed to be lowered is selected in two stages using a changeover switch, thereby reducing fuel consumption and noise during no-load conditions.

〔Example〕

1 to 3, reference numeral 1 indicates an engine mounted on a hydraulic excavator (not shown), and reference numeral 2 indicates an accelerator lever for setting the rotation speed of the engine 1. In FIG.
Hydraulic pumps 3, 4, and 5 are connected to the engine 1 via an engine output shaft 1A. Of these, the pressure oil discharged from the hydraulic pumps 3 and 4 passes through the switching valves 6 and 7 and is connected to a traveling motor and a boom (not shown).
It is now supplied to hydraulic cylinders that move arms, buckets, etc. Pump 5 is a pilot pump similarly driven by engine 1 and has a dedicated circuit, and is always maintained at a constant pressure by a relief valve 8 provided on this circuit. A switching lever 9 for operating the switching valves 6, 7 is connected via a rod 10 to a spool of the switching valve 6, 7 with a pin. A cam 11 is provided near the middle of each rod 10, and a roller 12 is connected to a roller support rod 13 so as to be in contact with the cam 11.
The movement of the switching lever 9 is transmitted to the roller support rod 13 using a cam 11 and a roller 12.
Furthermore, this roller support rod 13 is interlocked with a switch 14 to generate an ON-OFF electric signal.

Therefore, by moving either of the switching levers 9, the cam 12 also moves, and the cam 12 moves the roller 12 and the roller support rod 13 to the right in the figure, turning off the load switch 14. The electrical signal output from the load switch 14 passes through the changeover switch 15 and operates the solenoid valves 6 and 17. If the changeover switch 15 is at the contact point shown, the solenoid valve 17 is moved, and if the changeover switch is changed to the contact point 15A, the solenoid valve 16 is moved. On the other hand, the accelerator lever 2 that sets the rotation speed of the engine 1 is attached to the bracket 1 which is pin-coupled to the engine 1 and 19B via the accelerator wire 18.
9 and provided on the bracket 19
Bracket 2 pin-coupled to A and engine 1
It is connected to a spring 22 connected to a boss 21A provided at 1. A connecting rod 20 having an elongated hole at one end is connected with a pin to the boss 19A of the bracket 19 and the boss 21A of the bracket 21. A lever 23A is pin-coupled via a rod 24.

Therefore, when the accelerator lever 2 is moved to the left, the bracket 19 is pulled by the accelerator wire 18 and moves around the pin joint 19B, and the boss 19A on the bracket 19 also moves in the same way. As a result, the bracket 21 moves around the pin joint 21B via the spring 22 connected to the boss 19A and the boss 21A, and at the same time, the control lever 2 of the injection pump 23 moves via the rod 24.
3A moves and has the effect of increasing the rotation speed of the engine 1. Further, there are hydraulic cylinders 25 and 26 on the upper part of the bracket 21, which are driven by pressure oil from the hydraulic pump 5 via electromagnetic valves 16 and 17. The hydraulic cylinders 25 and 26 have different strokes, and in the figure, the hydraulic cylinder 26 has a larger stroke than the hydraulic cylinder 25. The operation will be explained step by step below.

Figure 1 shows the engine stopped, Figure 2 shows the hydraulic excavator operating with the engine near its maximum speed and the switching lever operated, and Figure 3 shows the switching lever operating from the state shown in Figure 2. This is a neutral, no-load state. When the accelerator lever 2 is fully operated, the engine 1 is near its maximum rotation, and the hydraulic excavator is operating, one of the switching levers 9 is operated. FIG. 2 shows a state in which the switching lever 9A is being operated. Since the switching lever 9A is moved, the load switch 14 is turned OFF and the solenoid valve 16,
17 does not move, and the pressure oil from the pilot pump 5 returns to the tank through the relief valve 8.

FIG. 3 shows a case where the switching lever 9A is returned to neutral from this state and the movement of the hydraulic excavator is stopped. At this time, the engine 1 is in the state of maximum rotation without load, but since the changeover lever 9 is in the neutral position, the load switch 14 is turned on, and since the changeover switch 15 is in the position shown, the solenoid valve 17 is switched, and the pilot pump 5 is turned on. The pressure oil passes through the solenoid valve 17 and moves the hydraulic cylinder 25. The piston 25A of the hydraulic cylinder 25 is moved by pressure oil, and the piston 25A is moved by pressure oil.
A comes into contact with the bracket 21 and further moves the bracket 21 by the stroke of the hydraulic cylinder 25, so the control lever 23A of the injection pump 23 also moves in the direction of decreasing the rotational speed.

The control lever 23 is activated by the movement of the hydraulic cylinder 25.
A is forcibly returned, but since one end of the connecting rod 20 is an elongated hole, the connecting rod 20 moves and the spring 22 is also expanded, but the rotation center 2A of the accelerator lever 2 is normally Since the accelerator lever 2 is fixed, if the friction force is made larger than the extension force of the spring 22, even if the control lever 23A is forcibly returned and the engine 1 is rotated at a low speed,
The accelerator lever 2 will maintain its initial set position. In this state, if one of the switching levers 9 is operated next, the load switch 14 is turned off, the solenoid valve 17 is closed, and the circuit of the hydraulic cylinder 25 is connected to the tank line. Further, the hydraulic cylinder 25 has a spring 25B on the piston side, so that the piston 25A is forcibly returned, and the oil in the hydraulic cylinder 25 returns to the tank. When the piston 25A returns, the pressing force on the bracket 21 disappears, and the spring force of the spring 22, which has been expanded due to the pressing force of the hydraulic cylinder 25, causes the control lever 23A to be pulled, and the rotation speed of the engine 1 is automatically adjusted to the accelerator lever. It will rise to the point set in step 2.

On the other hand, when the changeover switch 15 is set to the 15A position, the solenoid valve 16 operates instead of the solenoid valve 17.
Pressure oil from the pilot pump 5 is supplied to the hydraulic cylinder 26. As mentioned above, the stroke of the hydraulic cylinder 26 is larger than that of the hydraulic cylinder 25, so when the bracket 21 shown in FIG. This will lead to a further decline.

As described above, the movement of the changeover lever 9 is detected by the load switch 14, and when the engine is in an unloaded state, the rotational speed is reduced, and the rotational speed to be reduced can be selected in two stages by the changeover switch 15. This can contribute to reducing fuel consumption and noise during no-load conditions.

[Effect of idea]

With this invention, when the engine is in a high speed range and under no load, the governor control lever of the injection pump can be forcibly returned to the low speed side and the engine can be driven to a low speed, reducing fuel consumption during no load. It also has the effect of lowering the noise level. Furthermore, the number of rotations to be lowered is divided into two stages, which the driver can arbitrarily select.

If there is only one stage, it will only work when the engine speed is set to a high speed range, for example 2000rpm→
It ranges from 1400 to 1500rpm, and the medium speed range (1400 to 1500rpm)
When used for finishing work etc. with the rotation speed set at around 1500rpm, the rotation did not decrease, but with this invention,
The two-stage selector switch reduces engine speed not only when the engine is full, but also in the medium speed range (e.g.
1500rpm→1000rpm), which is very effective.

[Brief explanation of the drawing]

Figures 1 to 3 show an example of the hydraulic circuit used in the speed regulating mechanism of the hydraulic excavator of the present invention. Figure 1 shows the engine in a stopped state, and Figure 2 shows the hydraulic excavator in operation near the maximum engine speed. Fig. 3 shows a state in which the switching lever is in the neutral position near the maximum engine speed. FIG. 4 shows the hydraulic circuit of the conventional device. 1...Engine, 2...Accelerator lever, 3,
4, 5...Hydraulic pump, 6,7...Switching valve, 14
...Load switch, 15...Changing switch, 1
6, 17... Solenoid valve, 23A... Injection pump control lever, 25, 26... Hydraulic cylinder.

Claims (1)

[Scope of utility model registration request] A load switch that detects the movement of a switching valve of a hydraulic excavator, two hydraulic cylinders with different strokes for reducing engine rotation, two solenoid valves that switch between the two hydraulic cylinders, and the two solenoid valves. and a hydraulic circuit for engine rotation control that drives the hydraulic cylinder independently from the hydraulic circuit of the hydraulic cylinder for driving the work equipment, and the load switch and the solenoid valve are operated when the engine is not loaded. , a hydraulic cylinder is operated to reduce engine rotation, and one of the two hydraulic cylinders is selectively operated by operating the changeover switch, so that two types of low-speed rotation can be selected. A hydraulic excavator speed regulating mechanism.