CN117966844A - Control unit for an excavator - Google Patents

Abstract

A control unit for an excavator is configured to: detecting the action of the excavator handle; confirming that the excavator sequentially performs excavating, loading and unloading actions based on the detected handle actions; upon confirming initiation of the return stroke action based on the detected handle action, decreasing the engine speed relative to the original engine speed along an equal power curve and increasing the engine torque to maintain the engine output power substantially equal to the demand power set for the return stroke action while increasing the displacement of the hydraulic pump; after the return stroke action passes a preset deceleration period or when the return stroke action is confirmed to be completed based on the detected handle action, the engine speed is increased to the original speed, and the displacement of the hydraulic pump is restored to the displacement which is matched with the original speed of the engine.

Description

Control unit for an excavator

Technical Field

The present application relates to a control unit for an excavator, which is capable of reducing fuel consumption by controlling the operation of an excavator engine.

Background

The excavator generally drives a hydraulic pump through a diesel engine, hydraulic oil output by the hydraulic pump is distributed to each executive component (a hydraulic cylinder, a rotary motor, a walking motor and the like) through a hydraulic system, and the motion of a working device, the rotary motion of a rotary platform, the walking motion of the whole machine and the like are realized by each executive component. The working device mainly comprises main components such as a movable arm, a bucket rod, a bucket and the like, wherein the main components are hinged with each other, and swing around a hinge point under the action of a hydraulic cylinder to finish work.

The fuel consumption in the duty cycle is an important indicator for evaluating the performance of an excavator. Excavator fuel consumption depends on the one hand on whether the operation of the crew is reasonable or not, and on the other hand, also on the more important hand, on the manufacturer's design. In the design of the excavator, the oil consumption can be reduced by optimizing the design of hardware, and the oil consumption can be further reduced on the level of the original hardware by improving software.

Disclosure of Invention

An object of the present application is to provide an excavator control scheme capable of reducing fuel consumption by controlling an operation speed of an excavator engine during an excavating work.

In order to achieve the object, the present application provides in one aspect a control unit for an excavator, the excavator comprising an engine, a hydraulic pump driven by the engine and an actuator supplied with hydraulic oil by the hydraulic pump, the control unit being configured to be able to control at least an excavating work of the excavator, the excavating work comprising excavating, loading, unloading, and returning actions performed in sequence, the control unit being further configured to perform engine speed control in the excavating work:

detecting the action of the excavator handle;

confirming that the excavator sequentially performs excavating, loading and unloading actions based on the detected handle actions;

Upon confirming initiation of the return stroke action based on the detected handle action, decreasing the engine speed relative to the original engine speed along an equal power curve and increasing the engine torque to maintain the engine output power substantially equal to the demand power set for the return stroke action while increasing the displacement of the hydraulic pump;

After the return stroke action passes a preset deceleration period or when the return stroke action is confirmed to be completed based on the detected handle action, the engine speed is increased to the original speed, and the displacement of the hydraulic pump is restored to the displacement which is matched with the original speed of the engine.

In one embodiment of the present application, the engine rotation speed control performed by the control unit in the excavation work is independent of the control of each operation in the excavation work.

In one embodiment of the application, the deceleration period is about 5 seconds.

In one embodiment of the present application, the control unit controls the reduction value of the engine speed with respect to the original speed in the range of 200 to 300rpm in the return operation.

In one embodiment of the application, during engine deceleration, the displacement of the hydraulic pump is increased to maintain the hydraulic pump output flow substantially equal to the hydraulic pump demand flow in the return stroke.

In one embodiment of the application, the control unit constrains the upper limit of the reduced value of the engine speed relative to the original speed with the highest limit value of the hydraulic pump displacement during the engine deceleration.

In one embodiment of the application, the control unit sets the engine speed to be reduced by a reduced value relative to the original speed during the engine speed reduction, and allows the output flow rate of the hydraulic pump at the reduced engine speed to be lower than the hydraulic pump demand flow rate in the return stroke operation for a set period of time.

In one embodiment of the application, the control unit allows the maximum output flow of the hydraulic pump to be less than 10% of the demanded flow of the hydraulic pump in the return stroke operation at the reduced engine speed during the engine deceleration, and the period of time is at most 5 seconds, preferably 2 to 3 seconds.

In one embodiment of the present application, the control means controls the engine speed to be in the range of 1300 to 1500rpm and the engine torque to be in the range of 250 to 320Nm during the return operation.

The present application provides in another aspect an excavator comprising an engine, a hydraulic pump driven by the engine, an actuator supplied with hydraulic oil by the hydraulic pump, and a control unit of the present application configured to control at least an excavating work of the excavator and to perform engine speed control during the excavating work.

According to the excavator control scheme, through improvement of software, the rotation speed of the engine is reduced in the return stroke (returning to the excavating process) of the excavating work of the excavator, so that the oil consumption of the engine is reduced and the fuel efficiency is improved in the period. The control scheme of the application can be realized by means of software only, and the transformation of hardware is not required.

Drawings

The application may be further understood by reading the following detailed description with reference to the accompanying drawings, in which:

FIGS. 1-4 are graphs used to explain the excavator control scheme of the present application;

FIG. 5 is an exemplary flow chart for implementing an excavator control scheme in accordance with the present application.

Detailed Description

The present application relates generally to a control scheme for an excavator, the excavation work process of which typically includes repeatedly performed work cycles, each work cycle typically including sequentially performing excavation, loading, unloading, and return (i.e., the process of unloading and returning to the next excavation). The application aims to reduce the oil consumption in the working process of the excavator.

The excavator includes an engine that drives a hydraulic pump to supply hydraulic oil to each actuator through a hydraulic system, a hydraulic pump, and various actuators.

First, the present application examines an engine universal characteristic map of an excavator. The engine of the present application related to an excavator is typically a diesel engine, and has a general characteristic diagram schematically shown in fig. 1. In the universal characteristic diagram, the horizontal axis represents the engine speed n, the vertical axis represents the engine torque T, each curve indicated by a dot-dash line in the diagram is an equal power curve of the engine, the number in the curve is a power value (kW), and each curve represents the engine speed and torque corresponding to the power. Generally, for the same power, the higher the engine speed, the smaller the torque, the lower the engine speed, and the greater the torque.

Statistics show that the operating point (in terms of rotation speed + torque) in each operating cycle of the engine is located substantially within the conventional excavating operating region indicated by the inclined frame a in fig. 1, wherein the operating point of the return stroke (return to the process of excavating) is located substantially within the return stroke operating region indicated by the hatched region A1 below the excavating operating region a. When the return operation area A1 is examined, the power of the engine required in the return operation is lower than the power of the working point in the working of digging, loading and unloading. The operating point of the return operating region A1 in the conventional art is typically a high engine speed, low torque point.

The graph shown in fig. 2 is obtained by adding an engine fuel consumption curve to the engine universal characteristic graph shown in fig. 1. In the graph shown in fig. 2, fuel consumption curves of the respective operating points indicated by solid contour lines are added. The numbers in each fuel consumption represent engine fuel consumption (g/kWh). Generally, for a certain rotational speed value, the smaller the torque, the higher the fuel consumption. It can be seen that the fuel consumption of the backhaul work area A1 is high in the conventional technology, and is basically the highest fuel consumption area in the whole excavation work area a. In particular, in the lowest torque range (e.g., 100-200 Nm), engine fuel consumption is high.

Based on this recognition, the present application proposes to shift the return operating region A1 along the equal power region to the region shown in fig. 3, in which the engine speed is reduced and the torque is increased. In this way, the torque at the operating point in the return operating region A1 increases, so that the engine fuel consumption decreases. And, the bottom (torque lowest) of the return operating region A1 is made higher than the lowest torque section as much as possible.

In the above example, in the return operation region A1, the engine speed is controlled to be substantially in the range of 1300 to 1500rpm, and the engine torque is controlled to be substantially in the range of 250 to 320 Nm. It is to be noted that the engine speed range and the torque range differ depending on the general characteristic curve of the engine, and therefore the engine torque and the speed range of the return operating region A1 thereof may be specifically set for a specific engine.

Further, as shown in the graph of fig. 4, assuming that the engine is operated at a set required power in the return operation of the excavator in a conventional technology, the return operation point B of the engine is shifted to a new return operation point B1 (located in the shifted return operation region A1) along the equal power curve of the required power, and the rotation speed is reduced by an amount of Δn. In order to obtain a significant fuel consumption reduction effect, Δn may be set in a range of, for example, 200 to 300 rpm. The oil consumption of the original return operating point B is between 110 and 120g/kWh, and the oil consumption of the new return operating point B1 is between 105 and 110g/kWh, so that the oil consumption in the return of the excavator can be reduced. Since the new backhaul operating point is moved along the equipower curve relative to the original backhaul operating point, the power output by the engine remains unchanged during the backhaul so that the excavator can achieve the intended action in the backhaul.

Further, in order to avoid affecting the return operation of the excavator due to the return operating point shift, it is also desirable to keep the pump output flow Q unchanged during the return. Specifically, the hydraulic pump is a variable displacement pump, and the relationship between the pump displacement Vg and the pump output flow rate Q is expressed as:

Vg＝Q/n

After the engine speed n at the new return operating point is reduced, the pump displacement Vg needs to be controlled to increase to maintain the pump output flow Q substantially unchanged, i.e., at the pump output flow demanded by each actuator involved in the excavation work. The pump displacement Vg may be adjusted by a variable mechanism of the pump. For a swash plate type pump, the change of the pump displacement Vg can be realized by adjusting the angle of the swash plate through a variable mechanism.

It is noted that the pump displacement Vg is typically set to a maximum limit value. Therefore, the maximum limit value of the pump displacement Vg constitutes a limit to the rotation speed reduction value Δn. That is, maintaining the pump output flow rate Q substantially constant with a decrease in rotational speed does not cause the pump displacement Vg to increase beyond the maximum limit of the pump displacement Vg. Alternatively, a reduction Δn may be provided, the pump being unable to maintain the required pump output flow for a short period of time at the set reduction, i.e. the maximum output flow of the pump at the rotational speed after this reduction is slightly less than the required pump output flow, e.g. within 10%, and the period of time is set to be only a few seconds, e.g. 2-3 seconds, up to 5 seconds.

On the other hand, the engine torque T required for each actuator involved in the excavation work can be expressed as:

T＝P*Vg*/2π

Where P is the pump output pressure. As the pump displacement Vg increases, the demanded engine torque T increases synchronously. Thus, the engine power delivered by the pump can be maintained unchanged.

In summary, by actively reducing the engine speed (in conjunction with increasing the pump displacement) and increasing the engine torque during the return stroke of the excavator, it is achieved that the oil consumption is maintained to be reduced during the return stroke of the excavator, while the return stroke action of the excavator is not affected.

The excavator may be set at a fixed engine original (normal) rotational speed during the excavating work. The engine drives the hydraulic pump to execute the actions of digging, loading and unloading at the original rotating speed. Meanwhile, the displacement of the hydraulic pump is set at a displacement adapted to the original rotational speed of the engine for the excavating, loading or unloading action, so that the output flow rate of the hydraulic pump is equal to the pump demand flow rate in the excavating, loading or unloading action.

When the excavator sequentially completes excavation, loading and unloading and is ready for return stroke, the rotation speed of the engine can be temporarily reduced, and the pump displacement can be increased. After the engine speed is reduced by a settable deceleration period, or after the return action is completed, the engine speed can be controlled to return to the original engine speed, and the pump displacement can be adjusted to the displacement which is required in the excavating, loading and unloading actions and is adapted to the original engine speed.

In order to implement the above-described concept of the present application, a control unit for an excavator is proposed. The control unit is configured to be able to perform excavation work of an excavator as well as other excavator work (such as land leveling, etc.). For the excavation work, the control unit may control the excavation action of the excavator on the one hand, and perform the engine speed control independently of the control of the excavation action on the other hand. One engine speed control routine that the control unit may perform during an excavation operation is schematically illustrated in fig. 5.

As shown in fig. 5, in step S1, the control unit starts an engine speed control flow in the excavation work. The engine speed control routine may be started based on the start of the excavation work of the excavator.

Next, in step S2, the control unit detects the operation of the excavator handle.

Next, in step S3, the control unit determines whether the excavator is performing an excavating action based on the detected handle action. If the judgment result is negative, the flow returns to the step S2; if the determination is yes, the flow goes to step S4.

In step S4, the control unit determines whether the excavator is performing a loading operation for a period of time (for example, several seconds) based on the handle operation determination. If the judgment result is negative, the flow returns to the step S2; if the determination is yes, the flow goes to step S5.

In step S5, the control unit determines whether the excavator is performing a discharging action for a period of time (for example, several seconds) based on the handle action determination. If the judgment result is negative, the flow returns to the step S2; if the determination is yes, the flow goes to step S6.

In step S6, the control unit determines whether the excavator is performing a return stroke action (return excavation) for a period of time (for example, several seconds) based on the handle action determination. If the judgment result is negative, the flow returns to the step S2; if the determination is yes, the flow goes to step S7.

In step S7, the control unit decreases the engine speed and controls the pump displacement to keep the pump output flow substantially unchanged so as to be substantially equal to the demanded pump flow or only slightly lower than the demanded pump flow for a period of time to meet the excavator return action requirement.

Next, in step S8, the control unit determines whether the engine speed reduction is to be ended. The condition for ending the engine speed reduction is that the return stroke action is judged to be completed or the engine speed reduction time reaches a preset speed reduction period based on the detected handle action. If the judgment result is negative, the flow returns to the step S7; if the determination is yes, the flow goes to step S9.

In step S9, the control unit engine resumes the original rotation speed and the displacement of the hydraulic pump adapted to the original rotation speed. It is to be noted that, in the case where the return stroke operation is judged to be completed based on the detected handle operation to restore the original rotation speed of the engine, the adaptive displacement of the hydraulic pump at this time is set so that the pump output flow rate satisfies the flow rate required for the next excavation; in the case where the engine speed reduction time reaches a preset deceleration period to recover the original engine speed, the adaptive displacement of the hydraulic pump is set such that the pump output flow rate satisfies the flow rate required to complete the return stroke.

After step S9 is completed, the flow returns to step S2.

The control unit performs the return-stage engine speed reduction control and the corresponding pump output flow control with reference to the foregoing description.

It is to be noted that the engine speed control in the excavation work performed by the control unit is based only on the action signal from the handgrip, and that only the engine deceleration and the pump displacement increase are performed in the engine speed control. The flow of the engine speed control is parallel to and decoupled from the action control of the excavator excavation work, so that the engine speed control does not substantially interfere with the excavator excavation work, particularly the excavation, loading and unloading actions. In the return operation, if the engine speed is reduced to a pump flow rate that causes the maximum output flow rate of the pump to fall short of the demand as described above, but this occurs only for a short period of time in the return operation, there is no effect at all on the excavating, loading and unloading operations of the excavator.

Furthermore, since the engine speed control in the excavation work performed by the control unit is based solely on the action signal from the handgrip, no additional signal, such as a sensor signal, is required to confirm the authenticity of each action, the control scheme is simple.

The application also relates to an excavator comprising such a control unit.

Those skilled in the art, with the present inventive concept, may make various adaptations of the control unit for specific applications.

According to the excavator control scheme, through improvement of software, the rotation speed of the engine is reduced in the return stroke (returning to the excavating process) of the excavating work of the excavator, so that the oil consumption of the engine is reduced and the fuel efficiency is improved in the period.

In the field of excavators, various attempts to reduce fuel consumption during excavation have been made, and in general, attention has been paid to high-power operations such as excavation, loading and unloading, and there is no attention paid to fuel consumption during low-power operations such as return (return to excavation) of the excavator. The application focuses on the scheme of reducing the engine rotation speed and the oil consumption in the return stroke of the excavator for the first time, and obtains unexpected beneficial technical effects.

The control scheme of the application can be realized by means of software only, and the application does not need to be matched with the transformation of hardware, so that the control scheme can be implemented on a new excavator or an existing excavator (only software is required to be updated), and the hardware cost is not increased.

Although the application is described herein with reference to specific embodiments, the scope of the application is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims (10)

1. A control unit for an excavator, the excavator comprising an engine, a hydraulic pump driven by the engine and an actuator supplied with hydraulic oil by the hydraulic pump, the control unit being configured to be able to control at least an excavating work of the excavator, the excavating work comprising excavating, loading, unloading, return actions performed in sequence, the control unit being further configured to perform engine speed control in the excavating work:

detecting the action of the excavator handle;

confirming that the excavator sequentially performs excavating, loading and unloading actions based on the detected handle actions;

Upon confirming initiation of the return stroke action based on the detected handle action, decreasing the engine speed relative to the original engine speed along an equal power curve and increasing the engine torque to maintain the engine output power substantially equal to the demand power set for the return stroke action while increasing the displacement of the hydraulic pump;

After the return stroke action passes a preset deceleration period or when the return stroke action is confirmed to be completed based on the detected handle action, the engine speed is increased to the original speed, and the displacement of the hydraulic pump is restored to the displacement which is matched with the original speed of the engine.

2. The control unit for an excavator according to claim 1, wherein the engine speed control performed by the control unit in the excavating work is independent with respect to the control of each action in the excavating work.

3. The control unit for an excavator of claim 1 or claim 2, wherein the deceleration period is about 5 seconds.

4. A control unit for an excavator according to any one of claims 1 to 3, wherein in the return action the control unit controls the reduction (Δn) of the engine speed relative to the original speed to be in the range 200 to 300 rpm.

5. The control unit for an excavator of any one of claims 1 to 4, wherein during an engine deceleration the displacement of the hydraulic pump is increased to maintain the hydraulic pump output flow substantially equal to the hydraulic pump demand flow in a return stroke.

6. The control unit for an excavator according to any one of claims 1 to 5, wherein the control unit constrains the upper limit of the reduced value of the engine speed relative to the original speed with the highest limit value of the hydraulic pump displacement during the engine deceleration.

7. The control unit for an excavator according to claim 6, wherein the control unit sets the engine speed to be reduced by a reduced value with respect to the original speed during the engine speed reduction, and allows the output flow rate of the hydraulic pump at the reduced engine speed to be lower than the hydraulic pump demand flow rate in the return stroke operation for a set period of time.

8. The control unit for an excavator according to claim 7, wherein the control unit allows the maximum output flow of the hydraulic pump to be less than 10% of the demanded flow of the hydraulic pump in the return stroke operation at a reduced engine speed during the engine down-speed, and the period of time is at most 5 seconds, preferably 2-3 seconds.

9. The control unit for an excavator according to any one of claims 1 to 8, wherein in the return operation the control unit controls the engine speed to be in the range 1300 to 1500rpm and the engine torque to be in the range 250 to 320 Nm.

10. An excavator comprising an engine, a hydraulic pump driven by the engine, an actuator supplied with hydraulic oil by the hydraulic pump, and a control unit as claimed in any one of claims 1-9, the control unit being configured to control at least an excavating work of the excavator and to perform engine speed control during the excavating work.