JPH03213632A - Rotation frequency control device of pump-driving engine - Google Patents

Abstract

PURPOSE:To prevent a rise of rotation frequency in a no-load operation when a throttle lever is at the maximum position by finding a throttle driving signal responding to an engine output horsepower diagram selected depending on the operation condition, when the pump discharge pressure is less than the pressure in the engine rating rotation condition. CONSTITUTION:In a system in which a working machine such as a hydraulic shovel is being run by feeding the discharge oil of a hydraulic pump driven by an engine 5 to a rotary motor 2 through a direction control valve 3, it is discriminated whether the pump discharge pressure detected by a pressure detecting device 10 is less than the pressure in the engine rating rotation or not, when a throttle control device 9 to control the throttle lever 6 of the engine 5 is controlled by a controller 12. And when it is less than the relevant pressure, the engine output horsepower is calculated, and one of plural engine output horsepower diagrams is selected depending on the resultant calculation. And a throttle driving signal responding to the output horsepower diagram is calculated and output to the throttle control device 9.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is provided in civil engineering and construction machines such as hydraulic excavators and cranes, and is directed to controlling the rotation speed of a pump driving engine that controls the rotation speed of an engine that drives a hydraulic pump. Regarding a control device.

[Conventional technology]

FIG. 3 is a circuit diagram showing the basic circuit configuration of a civil engineering/construction machine, such as a hydraulic excavator, equipped with this type of pump drive engine rotation speed control device.

The circuit shown in FIG. 3 includes a hydraulic pump, for example, a variable displacement hydraulic pump 1, an actuator, for example, a swing motor 2, which is driven by pressure oil discharged from the hydraulic pump 1, and an actuator, such as a swing motor 2, which is supplied from the hydraulic pump 1 to the swing motor 2. a directional control valve 3 that controls the flow of pressure oil; a relief valve 4 that regulates the magnitude of the discharge pressure of the hydraulic pump l; an engine 5 that drives the hydraulic pump 1; and a fuel injection amount of the engine 5, i.e. It is equipped with a throttle lever 6 for controlling the rotation speed.

The relationship between the output horsepower H of the engine 5 and the engine rotational speed N described above is expressed as shown in the characteristic diagram of FIG. In this Figure 4, A is the rated point, Ho is the engine output horsepower at this rating, that is, the rated horsepower, RO is the rated rotation speed, Rm is the rotation speed at no-load high idle, and the throttle lever 6 of the engine 5 is When controlling the injection amount to decrease,
The characteristic of engine output horsepower H gradually changes from the A to Rm line in FIG. 4 to the B to R line and C-+RO line. In addition, Hl indicates the output horsepower when the hydraulic excavator is used for work that flattens the ground, that is, when the load is light and requires relatively small operations such as leveling work, and this output horsepower H, is the output horsepower at the rated rotation. A-+R, which is a characteristic diagram of
It corresponds to the dot located in the middle of the diagram of m.

Further, the relationship between the discharge pressure P and the discharge flow rate Q in the above-mentioned hydraulic pump 1 is expressed as shown in the characteristic diagram of FIG. In this Figure 5, Pmax is the maximum pressure regulated by the relief valve 4, PO is the discharge pressure corresponding to the rated point A in Figure 4 mentioned above, that is, the rated pressure, P is the point D in Figure 4, That is, it is the displacement load pressure corresponding to the output horsepower H1, and Qm is the product of the rotation speed Rm at no-load high idle, which is the maximum rotation speed of the engine 5 shown in FIG. 4, and the displacement volume of the hydraulic pump 1. The maximum discharge flow rate of the hydraulic pump 1 determined by Qo is the discharge flow rate at the rated rotation.

In the circuit configured as described above, when the discharge pressure of the hydraulic pump 1 decreases from the maximum pressure Pmax, the pressure/flow characteristics of the hydraulic pump 1 change along the line H→engine→Qm in FIG. 5. In this case, during H-I, the output horsepower of the engine 5 is approximately the rated horsepower Ho at the rated point A in FIG. 4, and is almost constant. Further, between I→Qm in FIG. 5, the amount of tilting of the hydraulic pump 1 is maximum, and due to the high idle of the engine 5, that is, the increase in the rotational speed in the line A-*Rm in FIG. Discharge flow rate from QO to Qm
increase to.

[Problem to be solved by the invention]

By the way, in the conventional rotation speed control device configured as described above, when the throttle lever 6 shown in FIG. Accordingly, on the characteristic line shown in Fig. 4, the rated point A→
It moves like Rm (rotation speed at high idle with no load). For this reason, there is a problem in that the rotational speed increases above the no-load rated rotational speed RO, resulting in no-load noise. In addition, since the rotational speed changes as the load changes, the discharge flow rate changes during light loads that require fine operations as described above, that is, when performing the rolling work shown in Figure 4, and this causes The drive speed of the motor 2 fluctuates, and the rotation motor 2
There is also the problem that it becomes difficult to perform light-load work that requires control, that is, fine operation. It should be noted that, if pump efficiency is ignored, the output horsepower H at a point is expressed as H1=(Pt-Qt)/450.

In the above description, the hydraulic pump 1 is a variable displacement hydraulic pump, but even if it is a fixed displacement hydraulic pump, the same problem occurs.

The present invention was made in view of the above-mentioned actual situation in the prior art, and its purpose is to prevent the rotation speed from increasing when the slot flap lever is at the maximum position and no load, and to prevent the actuator from increasing when the load is light. An object of the present invention is to provide a rotation speed control device for a pump drive engine that can suppress fluctuations in drive speed due to fluctuations in load.

[Means to solve the problem]

To achieve this object, the present invention provides a rotation speed control device that is installed in a civil engineering/construction machine and controls the rotation speed of an engine that drives a hydraulic pump, including a throttle lever control device that controls the throttle of the engine; A pressure detection device that detects the discharge pressure of the hydraulic pump, and a controller to which the throttle control device and the pressure detection device are connected, and the controller receives a pressure signal output from the pressure detection device. an input unit; a storage unit that stores in advance the discharge flow rate of the hydraulic pump at the rated rotation of the engine, and also stores output horsepower diagrams of the plurality of engines corresponding to differences in engine rotation speed;
It is determined whether the value of the pressure signal input to the input section is below the pressure at the rated rotation of the engine, and if it is below the pressure, the hydraulic pump discharges at the rated rotation of the engine stored in the storage section. calculates the engine output horsepower based on the flow rate and the value of the pressure signal, and selects from the storage section an engine output horsepower diagram in which the output horsepower at the rated rotational speed of the engine is the engine output horsepower obtained by the calculation. , has a configuration including a calculation unit that calculates a throttle drive signal corresponding to the selected engine output horsepower diagram, and an output unit that outputs the throttle drive signal calculated by the calculation unit to the throttle control device. .

[Effect]

Since the present invention is configured as described above, when the throttle lever is at the maximum position and there is no load or when the load is light, the discharge pressure decreases below the maximum pressure Pmax and is detected by the pressure detection device. When the value of the pressure signal becomes less than the pressure at the engine's rated rotation, the calculation section of the controller selects an engine output horsepower diagram that maintains the rated rotation speed, and outputs it from the output section of the controller to the throttle control device. A throttle drive signal corresponding to the above-mentioned engine output horsepower diagram is output, and the throttle is controlled by the throttle control device to maintain the engine speed at the rated speed, and the discharge flow rate of the hydraulic pump also depends on the load on the actuator. Regardless of fluctuations, the flow rate is maintained constant according to the pressure at rated rotation, and fluctuations in the drive speed of the actuator can be suppressed.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a rotation speed control device for a pump-driven engine according to the present invention will be explained based on the drawings.

FIG. 1 is a circuit diagram of a hydraulic circuit including one embodiment of the present invention. The circuit shown in FIG. 1 is installed in, for example, a hydraulic excavator, and similarly to the circuit shown in FIG. 3, a relief valve 4 that regulates the discharge pressure of the hydraulic pump 1, an engine 5 that drives the hydraulic pump 1, and a throttle lever 6 that controls the drive of the engine 5.

One embodiment includes a throttle control device 9 that controls a throttle lever 6 of an engine 5 and includes, for example, a link 7 and a stepping motor 8, and a throttle control device 9 that detects the discharge pressure of the hydraulic pump 1 and outputs a pressure signal Px. A rotation speed detection device 11 consisting of a pressure detection device 10 that outputs an output, a rotation speed detection device 11 that detects the rotation speed of the engine 5, for example, a proximity switch that detects pulses of irregularities on the rotating shaft, a throttle control device 9, and a pressure detection device 11. It includes a detection device 10 and a controller 12 to which the rotation speed detection device 11 is connected.

This controller 12 includes an input section for inputting the pressure signal Px output from the pressure detection device 10 and the rotation speed signal output from the rotation speed detection device 11, and the rated time of the engine 5 shown in FIG. The discharge flow rate Qo of the hydraulic pump 1 corresponding to the pressure Po is stored, and the output horsepower diagrams of the plurality of engines 5 corresponding to the difference in engine rotation speed, that is, the A-+Rm diagram and the B-+R diagram in FIG. 4 are stored.
A memory section stores a large number of output horsepower diagrams set according to differences in engine speed N, such as a 1-line diagram and a C→Ro diagram, and a memory section that stores a number of output horsepower diagrams set according to differences in engine speed N, and the value of the pressure signal Px input to the input section It is determined whether the pressure is below PO at the rated rotation of engine 5, and if the pressure is below PO, the engine 5 stored in the storage unit is
The engine output horsepower H, is calculated based on the discharge flow rate Qo of the hydraulic pump at the rated rotation and the value of the pressure signal Px, and the output horsepower at the rated rotation speed Ro of the engine 5 is the engine output horsepower obtained by the above calculation. An engine output horsepower diagram corresponding to H1' is selected from the above-mentioned storage section, a throttle drive signal corresponding to the selected engine output horsepower diagram is calculated, and the rotation speed detected by the rotation speed detection device 11 is calculated. A calculation unit that determines whether the signal is approximately equal to the rotation speed corresponding to the target throttle drive signal, and if not, performs calculations to correct the throttle drive signal, and a throttle control unit that uses the throttle signal calculated by this calculation unit to perform throttle control. It has an output section for outputting to the device 9.

In this configuration, the rotation speed of the engine 5 is basically controlled by the controller 12 in accordance with the pressure signal px detected by the pressure detection device 10 as shown in FIG.
It is controlled by the processing performed in .

That is, as shown in step S1 in FIG. 2, the pressure signal px from the pressure detection device 10 is first input to the calculation section via the input section of the controller 12. Next, in step S2, the value of the pressure signal Px becomes the rated rotational pressure PO shown in FIG.
It is determined whether the If this determination is not satisfied, it is not a no-load operation and light load work is not intended, so the process moves to step S3, where the process of setting the throttle drive signal to the maximum value is performed, and then the process moves to step S4. The throttle drive signal having the maximum value is output to the stepping motor 8 constituting the throttle control device 9 shown in FIG. As a result, the stepping motor 8 is activated, the link 7 is moved, for example, to the left in FIG. For example, heavy excavation work that is normally carried out becomes possible.

Further, when the determination in step S2 described above is satisfied, it is when the throttle lever 6 is at the maximum position and no load, or when light load work corresponding to the dots in FIG. 4 is performed, and step S5 is performed. Move.

In this step S5, a process is performed to calculate the output horsepower H1' based on the pressure signal Px and the rated flow rate Qo shown in FIG. For example, pump efficiency is not considered.

H1'=(PIXQo)/450<Hl.

Next, the process moves to step S6, and an engine output horsepower diagram in which the output horsepower at the rated rotation speed Ro becomes H1' determined in step S5 is selected based on the memory in the storage section. For example, in FIG. 4, if the intersection D' of the perpendicular line containing the rated rotational speed RO and the horizontal line containing H1' is on the output horsepower diagram B→R1, then this B→R1 diagram is selected. Next, the process moves to step S7, where a throttle drive signal corresponding to the engine output horsepower diagram obtained in step S6 is calculated, and the process moves to step S4, where the throttle drive signal is sent from the output section to configure the throttle control device 9 as described above. It is output to the stepping motor 8.

In the embodiment configured in this way, when the throttle lever 6 is at the maximum position and no load, the characteristic line A shown in FIG.
A B-R, C→RO diagram, etc., which is different from →Rm, is selected, so the engine speed N does not rise above the rated speed, suppressing the generation of no-load noise, and contributing to energy conservation. do.

In addition, when the load is light, the discharge flow rate is controlled by the discharge flow rate QO shown in FIG. High control accuracy of the swing motor 2 can be obtained.

Although the rotation speed detection device 11 described above is provided for feedback, it may not be provided if relatively low control accuracy is sufficient.

In addition, although a variable displacement hydraulic pump is provided as the hydraulic pump in the above example, a fixed displacement hydraulic pump can also be used to achieve similar control as described above over the entire range.

Further, although the present invention has been described using a throttle lever type (conventional type) for simplicity, it can be applied in exactly the same way to a recently developed electromagnetic type electronic governor.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to prevent the engine speed from increasing during no-load conditions when the throttle lever is at the maximum position, and therefore to reduce the occurrence of no-load noise compared to the conventional technology. In addition, it is possible to suppress fluctuations in the drive speed due to fluctuations in the actuator load such as during light loads, and therefore it is possible to ensure higher control accuracy of the actuator than in the past.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a hydraulic circuit including an embodiment of the pump-driven engine rotation speed control device of the present invention, and FIG. 2 is a basic processing procedure in the controller included in the embodiment shown in FIG. FIG. 3 is a circuit diagram showing the basic circuit configuration of a civil engineering/construction machine equipped with a conventional pump-driven engine rotation speed control device, and FIG. 4 shows the circuit shown in FIG. 3 and the engine in this embodiment. A characteristic diagram showing the relationship between rotational speed N and engine output horsepower H, Fig. 3
It is a characteristic diagram showing the relationship between the discharge pressure P and the discharge flow rate Q of the pump in the circuit shown in the figure and the present example. 1... Variable displacement hydraulic pump, 2... Swing motor (actuator), 5... Engine, 6... Throttle lever, 7...・Link, 8...Stepping motor, 9...
... Throttle control device, 10 ... Pressure control device, 12 ... Controller. Fig. 1 Fig. 3 Fig. 4 Fig. L

Claims (1)

[Claims] (1) In a rotational speed control device that is installed in civil engineering and construction machinery and controls the rotational speed of an engine that drives a hydraulic pump, a throttle control device that controls a throttle lever of the engine and a control device that controls the discharge pressure of the hydraulic pump. The controller includes a pressure detection device for detecting the pressure, and a controller to which the throttle control device and the pressure detection device are connected. A memory section that stores the discharge flow rate of the hydraulic pump at the rated rotation and output horsepower diagrams of multiple engines corresponding to differences in engine speed, and a memory section that stores the output horsepower diagram of multiple engines corresponding to differences in engine speed, and a It is determined whether the pressure is below the rated rotation of the engine, and if the pressure is below the pressure, the engine is Calculate the output horsepower, select from the storage unit an engine output horsepower diagram in which the output horsepower at the rated rotational speed of the engine is the engine output horsepower obtained by the calculation, and correspond to the selected engine output horsepower diagram. 1. A rotation speed control device for a pump-driven engine, comprising: a calculation section that calculates a throttle drive signal for the calculation; and an output section that outputs the throttle drive signal calculated by the calculation section to the throttle control device.