JPH1089305A - Controlling method for hydraulic machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controlling method for a hydraulic machine which can be operated with low feel consumption and low noise without damaging operability. SOLUTION: In the controlling method for a hydraulic machine changing discharge flow rate of a hydraulic pump 2 driven by an engine by controlling the tilting angle of the hydraulic pump 2 and the engine speed of an engine 1 and operating a hydraulic actuator connected with the hydraulic pump 2 according to the operation of an operating lever 5, the engine speed of an engine 1, pump load pressure of the hydraulic pump 2 and manipulated variable of the operating lever 5 are detected, engine output horsepower, target discharge flow rate and target pump absorption horsepower are calculated by a controller 13 from the engine speed, pump load pressure and manipulated variable detected, these engine output horsepower and target pump absorption horsepower calculated are c<: mpared, and target discharge flow rate is secured by controlling the tilting and revolving angle of the hydraulic pump when target pump absorption horsepower is engine output horsepower or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a hydraulic machine, and more particularly, to control of an engine speed and a pump tilt angle.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing a method of controlling a pump discharge flow rate in a conventional technique.

Generally speaking, the hydraulic pump discharge flow rate Qd
Is q: pump discharge capacity (pump discharge flow rate per rotation (c
c / rev)) N: At engine speed (rpm),

## EQU1 ## Qd = q.N (l / min)

[0004] The discharge capacity (cc / rev) of a hydraulic pump is controlled by the pump tilt angle. In the prior art, the engine speed in the operating state is operated at a fixed set speed determined by the throttle lever.

When the engine speed is constant, the pump discharge flow rate (l / min) is determined only by the pump tilt angle in accordance with Equation 1. When the operation lever of the operation device is tilted from the neutral state to the operation state to increase the operation amount, the pump tilt angle is proportionally increased in accordance with the lever operation amount.

When the lever operation amount is in a neutral state from 0 to a dead zone, the pump tilt angle is set so as not to change. When the lever operation amount becomes equal to or larger than the lever operation amount corresponding to the maximum tilt angle, the maximum discharge flow rate is uniformly determined by the set rotation speed at that time.

The control of the pump tilt angle is always controlled only by the operation lever angle, and is the same control. Therefore, the pump discharge flow rate differs between when the engine speed is high and when it is low. As shown in FIG. 9, the pump discharge flow rate is smaller at a low rotational speed than at a high rotational speed.

[0008] The operator changes the pump discharge flow rate by changing the set number of revolutions according to the work condition. As a result, the desired operability can be changed. However, as described above, the engine speed is a constant set speed set by the throttle lever, and the engine speed does not vary depending on the lever operation amount.

FIG. 10 shows the interrelationship between the engine speed, the pump tilt angle and the pump discharge flow rate when the lever is operated from the low speed engine operating state.

When the lever operation amount is in the neutral state, the engine speed is a constant low-speed operation, and the pump tilt angle is also a constant small tilt angle. Therefore, the pump discharge flow rate is a constant small flow rate Qa. When the operation lever is activated, the engine speed is switched from the low speed operation state to the set speed operation in a step response, the engine is operated at a constant set speed, and fluctuates according to the fluctuation of the lever operation amount. do not do. On the other hand, the pump tilt angle increases in proportion to the lever operation amount. Therefore, the pump discharge flow rate is varied only by the pump tilt angle.

FIG. 11 is a graph showing a PQ characteristic which is a relationship between the load pressure of the hydraulic pump limited by the engine horsepower and the discharge flow rate. The discharge flow rate on the vertical axis indicates the maximum discharge flow rate that can be discharged with respect to the load pressure.

Here, the absorption horsepower of the hydraulic pump is Lp: pump absorption horsepower P: pump load pressure q: pump discharge capacity N: engine speed ηp: hydraulic pump total efficiency

Lp = P · q · N / ηp, and when the engine speed N is constant, the pump absorption horsepower Lp varies depending on the pump load pressure P and the pump discharge capacity q.

On the other hand, the maximum output horsepower that can be output from the engine is a fixed value determined from the initially set rotational speed. Therefore, the pump absorption horsepower is controlled so as to follow a predetermined PQ characteristic so that the fluctuating pump absorption horsepower does not exceed the engine output horsepower.

The PQ characteristic is usually set so that the engine output horsepower has a margin in consideration of a sudden increase in pump load pressure and the like.

[0015]

In the prior art,
As described above, the engine is operated at a constant set speed. The set number of revolutions is a relatively high number of revolutions so as to cope with a case where an operation requiring a large horsepower is performed. Therefore, when performing a fine operation work requiring only a small horsepower, the engine is operated at a higher rotational speed than necessary. For this reason, in addition to the problem in terms of fuel economy, the prior art has a problem in terms of noisy engine noise and noise. Also, if the throttle lever is set to a medium speed or lower during working conditions requiring high horsepower, the output horsepower of the engine is limited by the set speed, and based on the set speed. The pump discharge flow rate is reduced according to the PQ characteristics. That is, there is a problem that operability is impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances in the prior art, and has as its object to provide a method of controlling a hydraulic machine that has low fuel consumption and low noise without impairing operability.

[0017]

In order to achieve the above object, the present invention is directed to a hydraulic pump driven by the engine by controlling a tilt angle of the hydraulic pump and a rotation speed of the engine. Change the discharge flow rate,
In a control method of a hydraulic machine that operates a hydraulic actuator connected to the hydraulic pump in response to operation of an operation lever, an engine speed of the engine, a pump load pressure of the hydraulic pump, and an operation amount of the operation lever are detected. Then, the engine output horsepower, the target discharge flow rate, and the target pump absorption horsepower are calculated from the detected engine speed, the pump load pressure, and the operation amount, and the calculated engine output horsepower and the target pump absorption horsepower are compared. When the target pump absorption horsepower is equal to or less than the engine output horsepower, the target discharge flow rate is secured by controlling the tilt angle of the hydraulic pump.

According to a second aspect of the present invention, the engine speed of the engine, the pump load pressure of the hydraulic pump, and the operation amount of the operation lever are detected, and the detected engine speed, pump load pressure, operation amount, and the like are detected. Calculate the engine output horsepower, the target discharge flow rate, and the target pump absorption horsepower, compare the calculated engine output horsepower with the target pump absorption horsepower, and if the target pump absorption horsepower exceeds the engine output horsepower, The target discharge flow rate is ensured by controlling the rotation speed of the engine.

According to a third aspect of the present invention, the discharge flow rate of the hydraulic pump driven by the engine is changed by controlling the tilt angle of the hydraulic pump and the number of revolutions of the engine, and In a control method of a hydraulic machine that operates a hydraulic actuator connected to a hydraulic pump, an engine speed of the engine, a pump load pressure of the hydraulic pump, and an operation amount of the operation lever are detected, and the detected engine speed is detected. The engine output horsepower, the target discharge flow rate, and the target pump absorption horsepower are calculated from the pump load pressure and the operation amount, and the calculated engine output horsepower and the target pump absorption horsepower are compared. When the engine output horsepower or less, the target discharge flow rate is ensured by controlling only the tilt angle of the hydraulic pump, If serial target pump absorption horsepower exceeds the engine output horsepower is to ensure by controlling the rotational speed of the engine the target discharge flow rate.

According to a fourth aspect of the present invention, the engine speed is reduced to a low-speed operation speed after a predetermined delay time has elapsed from the time when all of the operating devices are in the neutral state. .

According to a fifth aspect of the present invention, the engine is operated at the set rotational speed when a set rotational speed operation is instructed at a constant set rotational speed set by the throttle lever.

According to a sixth aspect of the present invention, when the target pump absorption horsepower exceeds the maximum output horsepower of the engine, the rotation speed of the engine is maintained at the rotation speed that becomes the maximum output horsepower, and the pump tilt angle is reduced. By controlling, the target pump absorption horsepower does not exceed the maximum output horsepower of the engine.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing a control device according to an embodiment of the present invention. FIG. 1 shows a case of a hydraulic excavator.

In this embodiment, an engine 1 as a power source, a plurality of variable displacement hydraulic pumps 2 (hereinafter referred to as hydraulic pumps) driven by the engine 1, and a pressure discharged by the hydraulic pump 2 A plurality of throttled switching valves 3 for controlling the direction and flow rate of oil and a plurality of hydraulic actuators 4 driven by pressure oil guided by the throttled switching valves 3 are provided. The engine 1 is provided with a rotation speed detection unit 9 for detecting the rotation speed of the engine 1 and an engine rotation control unit 10 for controlling the engine rotation speed. The rotation speed detector 9 outputs a signal corresponding to the rotation speed of the engine 1 at all times.

The hydraulic pump 2 is provided with a pump tilt controller 11 for controlling the pump discharge flow rate and a load pressure detector 12 for detecting the pump load pressure. The pump displacement control unit 11 controls the pump discharge flow rate of the hydraulic pump 2 by changing the displacement angle. The load pressure detector 12 constantly outputs a signal corresponding to the pump load pressure.

A plurality of operating devices 5 are provided as transmission means for the operator to operate. The operation device 5 outputs an operation signal corresponding to an operation amount that varies according to a lever operation angle. The throttle lever 6 is provided so that the operator can set a desired engine speed within a range from the lowest speed to the highest speed of the engine 1. The mode switch 7 is provided for setting the number of rotations to a fixed number in advance. In this embodiment, the throttle lever 6 and the mode switch 7 are used as the engine speed setting means, but at least one of them may be provided. Further, a shift operation in which the engine speed and the pump tilt angle are controlled in correlation with the fluctuating operation amount of the operation device 5 and the fluctuating pump load pressure are set, and the speed is set by the throttle lever 6 or the mode switch 7. A changeover switch 8 is provided as a means for selecting any one of a set rotation speed operation for setting a fixed set rotation speed.

An operation signal output from the operation device 5,
A controller 13 is provided for processing a signal output from the throttle lever 6, a signal output from the mode switch 7, the changeover switch 8, the load pressure detection unit 12, and a signal output from the rotation speed detection unit 9. .

The controller 13 outputs a signal for controlling the switching valve 3 with a throttle, a signal for controlling the pump tilt control unit 11, and a signal for controlling the engine rotation control unit 10.

FIG. 2 is a diagram showing the internal structure of the controller 13.

Inside the controller 13, a signal from the operating device 5, a signal from the throttle lever 6, a signal from the mode switch 7, a signal from the changeover switch 8, a signal from the pump load pressure detector 12 And an A / D converter 13a for converting a signal from the rotation detector 9 from an analog signal to a digital signal.

An engine horsepower calculator 13b which receives a signal corresponding to the signal of the rotation detector 9 from the A / D converter 13a and calculates the engine output horsepower at that time.
Is provided. Further, the pump load pressure detecting unit 12
, A target pump absorption horsepower calculation for calculating a target discharge flow rate and a target pump absorption horsepower by receiving a signal corresponding to a signal from the controller, a signal corresponding to a signal of the rotation detecting unit 9 and a signal corresponding to a signal from the operation device 5. A portion 13c is provided. In addition, a storage circuit unit 13d for storing a lever processing procedure of the operating device 5, a delay time counting procedure, and the like is provided. The A / D converter 13a, the engine horsepower calculator 13b, the target pump absorption horsepower calculator 1
3c and a control circuit unit 13e that performs a comparison operation process by receiving signals from the storage circuit unit 13d, and the control circuit unit 13
An output control circuit unit 13f that receives a signal from e and controls output to the switching valve with throttle 3, the pump displacement control unit 11, and the engine control unit 10 is provided. still,
The calculation processing performed in the target pump absorption horsepower calculation unit 13c, the engine horsepower calculation unit 13b, and the control circuit unit 13e is set in advance in the control circuit unit 13e as a map, and is selected as needed from the map. You may.

Next, a control method of the present invention using the above-described apparatus will be described with reference to FIGS. 3 and 4 are flowcharts showing one embodiment of the control method of the present invention.

FIG. 5 is a diagram showing the relationship between the target discharge flow rate, the pump tilt angle, and the engine speed with respect to the lever operation amount.

FIGS. 6 and 7 show the relationship between the load pressure of the hydraulic pump and the discharge flow rate of the hydraulic pump.

When a signal for performing a shift operation is not output from the changeover switch 8 regardless of the state of the operation lever, the engine speed set by the throttle lever 6 and the engine speed set by the mode switch 7 A signal for driving the engine 1 at the smaller number of revolutions (hereinafter referred to as a set number of revolutions) is sent from the controller 13 to the engine revolution controller 1.
Output to 0. This control flow corresponds to the flows A to H in FIGS. Incidentally, the set number of revolutions may be a number of revolutions determined by only one of the throttle lever 6 and the mode switch 7.

When a signal for performing a shift operation is output from the changeover switch 8, a signal corresponding to an operation amount of an operation lever from the operating device 5 and a signal for performing a shift operation from the changeover switch 8 are transmitted to the controller 13. Is input to Also, the pump load pressure from the load pressure detector 12
The engine speed is provided from the rotation detecting section 9 to the controller 13.

In this state, the controller 13
Then, a target discharge flow rate as shown by a solid line in FIG. 5 is determined in advance from the relationship between the set rotation speed and the lever operation amount of the operation device 5. Further, a target pump absorption horsepower is determined based on the target discharge flow rate. This control flow corresponds to the flow of AB in FIGS.

In FIG. 5, the hydraulic actuator 4
In the neutral state where does not operate, the minimum discharge flow rate Qa is uniform. The minimum flow rate Qa is always maintained at a constant value by correcting the pump tilt angle in accordance with the fluctuation of the engine speed. When the lever operation is activated, the pump discharge flow rate increases proportionally as the lever operation amount of the operation device 5 increases. The maximum discharge flow rate Qc is a value calculated from the set rotation speed and the maximum tilt angle. When the lever operation amount is equal to or more than the operation amount reaching the maximum flow rate, the maximum discharge flow rate Qc is uniform. Since the maximum discharge flow rate Qc is determined by the set number of revolutions set based on the operator's will, there is no operability against the operator's will.

Here, the target discharge flow rate Qd is Qd: target discharge flow rate (l / min) Qa: minimum discharge flow rate Qc: maximum discharge flow rate R: operation amount determined by the operation lever Rmin: operation amount in the neutral state Rmax: maximum inclination In the operation amount at the turning angle,

## EQU3 ## R ≦ Rmin → Qd = Qa R ≧ Rmax → Qd = Qc Qd = (Qc−Qa) (R−Rmin) / (Rmax−Rmi)
n) + Qa.

In the operation region corresponding to the discharge flow rate from the minimum flow rate Qa to Qb in FIG. 5, the target pump absorption horsepower is compared with the engine output horsepower at the low speed operation speed (see FIG. 3C). As a result, when the target pump absorption horsepower is equal to or less than the engine output horsepower, the target discharge flow rate is ensured only by the pump tilt control. Then, the engine speed is maintained at the low-speed operation speed (see D in FIG. 3). The discharge flow rate Qb is a value determined by the maximum pump tilt angle and the low-speed operation speed.

Here, the target discharge flow rate, engine output horsepower and target pump absorption horsepower are Qd: target discharge flow rate (l / min) Lp: target pump absorption horsepower Le: engine output horsepower P: pump load pressure q: pump discharge capacity ( Pump discharge flow rate per rotation determined by the pump tilt angle (cc / rev)) N: engine speed ηp: total pump efficiency Te: engine output torque (at a performance value predetermined by the engine speed,

## EQU4 ## Qd = q.N (l / min) Le = Te.NLp = P.q.N / ηp

In the embodiment of the present invention, the pump absorption horsepower calculation section 13c in the controller 13 calculates the target pump absorption horsepower Lp from the target discharge flow rate Qd and the pump load pressure P according to the above equation (4). At the same time, the engine output horsepower Le is calculated according to Equation 4. The controller 13 constantly compares the engine output horsepower with the target pump absorption horsepower.

In Qb, the pump displacement is at the maximum displacement angle and the target pump absorption horsepower is very close to the engine output horsepower (here, the engine output horsepower is 90%).
%. )It is in. In the flow rate range from Qb to Qc, the pump tilt angle is always at the maximum tilt angle. When the lever operation amount exceeds Qb, the engine rotation speed gradually increases from the low-speed operation rotation speed to the rotation speed at which the pump discharge flow rate according to the lever operation amount can be discharged. At this time, if the target pump absorption horsepower is equal to or less than the engine maximum output horsepower, the pump discharge flow rate gradually increases in accordance with a predetermined target discharge flow rate characteristic. This control flow is represented by A in FIGS. 3 and 4.
~ J.

At this time, the maximum value Qc of the pump discharge flow rate is a pump discharge flow rate determined from the set rotation speed which is a rotation speed determined based on the operator's will. Operability contrary to the will of the user is prevented.

In contrast to the prior art in which the lever operation is constantly driven at the set rotation speed in the operating state, the present invention outputs the engine output horsepower corresponding to the pump absorption horsepower that varies according to the lever operation amount and the pump load pressure. This improves fuel economy. Also, in contrast to the prior art which has always had a loud engine noise, the present invention makes it possible to reduce noise by operating the engine at an engine speed corresponding to the pump absorption horsepower.

The above-described control of the pump tilt and the engine speed is a control state when the pump load pressure is relatively low.

Referring to FIG. 6, the control of the tilting of the pump and the engine speed when the pump load pressure is relatively large will be described.

In FIG. 6, point A indicates that the target discharge flow rate is QA.
Where the pump load pressure is PA. The target discharge flow rate QA is a flow rate that can be discharged even at the engine output horsepower at a low speed operation speed if the pump load pressure is low. However, since the pump load pressure PA is large, the target pump absorption horsepower becomes larger than the engine output horsepower at the low speed operation speed, so that the target discharge flow rate QA cannot be discharged at the low speed operation speed.

In this state, the controller 1
The engine output horsepower required to discharge the target discharge flow rate is calculated by 3. The engine speed NA is calculated from the engine output horsepower, and a signal for setting the engine speed NA is output from the controller 13 to the engine speed control unit 10. At the same time, the controller 13 outputs a signal to the pump displacement control unit 11 for correcting displacement due to the change of the engine speed to NA. As a result, the target discharge flow rate QA at the pump load pressure PA can be discharged.

Next, at the point that the pump load pressure is PB and the target discharge flow rate is QB, if the pump load pressure PB is low, the rotation at which the target discharge flow rate QB between the low-speed operation speed and the set speed can be discharged. Set to a number. However, since the pump load pressure PB is large, the pump absorption horsepower calculated by the pump load pressure PB and the target discharge flow rate QB becomes larger than the maximum value of the engine output horsepower calculated from the set rotation speed.

In this state, the controller 1
The engine output horsepower required to discharge the target discharge flow rate is calculated by 3. The engine speed NB is calculated from the engine output horsepower, and a signal for setting the engine speed NB is output from the controller 13 to the engine speed controller 10. At the same time, the controller 13 outputs a signal to the pump displacement control unit 11 for correcting displacement due to the change of the engine speed to NB. As a result, the target discharge flow rate QB at the pump load pressure PB can be discharged.

In this case, the engine speed NB is controlled to a speed higher than a set speed set based on the operator's will. However, the pump discharge flow rate that affects the operability does not exceed the target discharge flow rate determined from the set number of revolutions, so that operability contrary to the operator's will does not occur.

In the prior art, since the engine is operated at a constant engine speed determined by the set engine speed, the engine output horsepower is determined by the constant engine speed. However, in this case, irrespective of the set speed, the pump absorption horsepower exceeding the engine output horsepower calculated by the set speed is made possible by allowing the speed to fluctuate in the range from the low speed operation speed to the maximum engine speed. On the other hand, it has become possible to secure the target discharge flow rate. That is, operability can be improved. The preset rotation speed in the present case is not for limiting the engine rotation speed but for limiting the pump discharge flow rate.

FIG. 7 is a diagram showing the control when the pump absorption horsepower calculated by the pump load pressure Pc and the target discharge flow rate Qc is equal to or more than the maximum output horsepower of the engine 1. In this case, the signal output from the controller 13 to the engine rotation control unit 10 is a signal indicating the number of revolutions at which the engine 1 has the maximum output horsepower. The engine output horsepower is maximized, but the pump absorption horsepower is higher than the engine output horsepower. At this time, the controller 13
The pump tilt angle is calculated to obtain the pump absorption horsepower corresponding to the engine output horsepower, and the pump discharge flow rate is calculated as Qc
From the pump displacement control unit 11
(See the flow of A to K in FIGS. 3 and 4).

Therefore, in the prior art, only the engine output horsepower determined by the set number of revolutions could be output, but in this case, the pump absorption horsepower that exceeds the engine maximum output horsepower by outputting the engine maximum output horsepower is output. Thus, a discharge flow rate closer to the target discharge flow rate can be secured. That is, it is possible to efficiently output the engine horsepower and improve the operability.

An operator who does not intend to output an engine output horsepower equal to or larger than the engine output horsepower determined by the engine speed on the smaller side of the throttle lever 6 or the mode switch 7 is required to use the changeover switch 8. , The upper limit of the engine rotation speed can be set to the set rotation speed, or it can be set to always operate at the set rotation speed.

FIG. 8 shows the relationship between the engine speed control and the pump tilt control when the lever is operated to return the operating lever from the operating state to the neutral state.

When the engine is operated at a speed higher than the low speed operation speed and an operation is performed such that the lever operation amount decreases or decreases from a held state toward a neutral state, In the range from when the lever operation amount decreases to the neutral state, the engine speed is maintained at the engine speed immediately before the lever operation amount decreases. The control of the pump discharge flow rate in this range is controlled only by the pump tilt angle to secure the target discharge flow rate.

In the operating state where the engine speed is equal to or higher than the low-speed operation speed, the controller 13 counts the elapsed time from the point a where all the operating levers are returned to the neutral state. The engine speed does not decrease until the elapsed time exceeds a predetermined delay time, and is maintained at the engine speed at that time (see the flow of G to EA in FIGS. 3 and 4).

The count of the elapsed time is cleared when the lever operation is again performed before the delay time elapses. Up to the point b, the engine speed is maintained, and the pump discharge flow rate is controlled to the target discharge flow rate only by the pump tilt control. When the lever operation (point b to point c) is performed again so as to exceed the engine output horsepower, the engine speed (point f to point g) increases to secure the target discharge flow rate.

If the lever operation is not performed such that at least one of the operation levers is activated by the time elapsed from the point d at which all the operation levers have returned to the neutral state until the delay time has elapsed, the low-speed rotation is performed. A signal to reduce the number is output from the controller 13 to the engine speed control unit 10. At the same time, a signal for securing the target discharge flow rate is output to the pump displacement control unit 11. The elapsed time count is cleared when it reaches a value corresponding to the delay time (see the flow of G to EF in FIGS. 3 and 4).

Accordingly, it is possible to prevent the engine speed from fluctuating up and down frequently when a lever operation in which the operation amount of the operation lever fluctuates up and down frequently is performed. That is, deterioration of fuel efficiency can be prevented. Further, as a point different from the prior art, the pump discharge flow rate is controlled by changing the pump tilt angle control in response to the change in the engine speed control, thereby preventing operability from being impaired. It should be noted that the engine 1
An operator who is not willing to change the engine sound can cancel the function by switching the changeover switch 8.

[0064]

Since the present invention is constructed as described above, the following effects can be obtained. The invention of claim 1 detects the engine speed of the engine, the pump load pressure of the hydraulic pump, and the operation amount of the operating lever, and determines the engine output horsepower from the detected engine speed, the pump load pressure, and the operation amount. A target discharge flow rate and a target pump absorption horsepower are calculated, and the calculated engine output horsepower and the target pump absorption horsepower are compared. If the target pump absorption horsepower is equal to or less than the engine output horsepower, the target discharge flow rate is calculated by the hydraulic pressure. Control the tilt angle of the pump. For this reason, when performing the fine operation work requiring only a small horsepower, the engine can be operated at an unnecessarily high rotation speed, and the fuel efficiency can be improved and the noise can be reduced.

According to a second aspect of the present invention, the engine speed of the engine, the pump load pressure of the hydraulic pump, and the operation amount of the operating lever are detected, and the engine speed, the pump load pressure, and the operation amount are detected. Output horsepower, target discharge flow rate, and target pump absorption horsepower are calculated, and the calculated engine output horsepower and target pump absorption horsepower are compared. If the target pump absorption horsepower exceeds the engine output horsepower, the target discharge flow rate is calculated. To control the number of revolutions of the engine. For this reason, the engine can be operated at an engine speed corresponding to the pump absorption horsepower required in the work. That is, it is possible to improve fuel efficiency and reduce noise without impairing operability.

The third aspect of the present invention provides the first and second aspects.
The present invention has the features of the present invention. Therefore, fuel efficiency can be improved and noise can be reduced without impairing operability.

According to a fourth aspect of the present invention, the engine speed is reduced to a low-speed operation speed after a predetermined delay time has elapsed from the time when all of the operation levers are in the neutral state. Thus, when the operation is interrupted for a relatively long time, the engine speed can be set to the low-speed operation speed to improve the fuel efficiency. Also, when the lever operation is performed such that all the operation levers are in the neutral state, and it is a short pause for a relatively short time,
By providing the delay time, it is possible to prevent the engine speed from fluctuating frequently in response to an operation in which the lever operation fluctuates frequently. That is, it is possible to prevent deterioration of fuel efficiency.

According to a fifth aspect of the present invention, a set speed operation is performed in which the set speed is set by the throttle lever.
For this reason, in a case where there is a danger that the operator may misunderstand the engine speed as a constant speed and operate the lever suddenly, there is a danger that the setting speed set by the throttle lever by the changeover switch is set. Danger can be avoided by instructing the rotation speed operation to set the rotation speed.

The invention according to claim 6 reduces the pump tilt angle when the target absorption horsepower exceeds the maximum output horsepower of the engine. Therefore, it is possible to prevent the engine speed from decreasing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of the inside of a controller according to the embodiment of the present invention.

FIG. 3 is a flowchart of a control device according to the embodiment of the present invention.

FIG. 4 is a flowchart of the control device following * in FIG. 3;

FIG. 5 is a diagram illustrating a relationship between a discharge flow rate of a hydraulic pump, a pump tilt angle, and an engine speed with respect to a lever operation amount according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a load pressure of the hydraulic pump and a discharge flow rate of the hydraulic pump according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between a load pressure of the hydraulic pump and a discharge flow rate of the hydraulic pump according to the embodiment of the present invention.

FIG. 8 is a diagram illustrating a relationship between a pump tilt angle and an engine speed with respect to a lever operation amount according to the embodiment of the present invention.

FIG. 9 is a diagram showing a method of controlling a pump discharge flow rate according to the related art.

FIG. 10 is a diagram showing a relationship between an engine speed and a pump tilt angle corresponding to a lever operation amount in the related art.

FIG. 11 is a diagram showing PQ characteristics in a conventional technique.

[Explanation of symbols]

1: Engine 2: Hydraulic pump
4: Hydraulic actuator 5: Operation lever 6: Throttle lever

Claims (6)

[Claims] The present invention controls a tilt angle of a hydraulic pump and a rotation speed of an engine to change a discharge flow rate of the hydraulic pump driven by the engine, and is connected to the hydraulic pump according to an operation of an operation lever. In the method for controlling a hydraulic machine that operates a hydraulic actuator, an engine speed of the engine, a pump load pressure of the hydraulic pump, and an operation amount of the operation lever are detected, and the detected engine speed, pump load pressure, From the amount of operation,
The engine output horsepower, the target discharge flow rate, and the target pump absorption horsepower are calculated, and the calculated engine output horsepower and the target pump absorption horsepower are compared. If the target pump absorption horsepower is equal to or less than the engine output horsepower, the target discharge is calculated. A method for controlling a hydraulic machine, wherein a flow rate is secured by controlling a tilt angle of the hydraulic pump. 2. A discharge flow rate of the hydraulic pump driven by the engine is changed by controlling a tilt angle of the hydraulic pump and a rotation speed of the engine, and the hydraulic pump is connected to the hydraulic pump in accordance with an operation of an operation lever. In the method for controlling a hydraulic machine that operates a hydraulic actuator, an engine speed of the engine, a pump load pressure of the hydraulic pump, and an operation amount of the operation lever are detected, and the detected engine speed, pump load pressure, From the amount of operation,
The engine output horsepower, the target discharge flow rate, and the target pump absorption horsepower are calculated, and the calculated engine output horsepower and the target pump absorption horsepower are compared. If the target pump absorption horsepower exceeds the engine output horsepower, the target discharge A method for controlling a hydraulic machine, wherein a flow rate is secured by controlling a rotation speed of the engine. 3. The discharge flow rate of the hydraulic pump driven by the engine is changed by controlling the tilt angle of the hydraulic pump and the number of revolutions of the engine, and connected to the hydraulic pump in accordance with the operation of an operation lever. In the method for controlling a hydraulic machine that operates a hydraulic actuator, an engine speed of the engine, a pump load pressure of the hydraulic pump, and an operation amount of the operation lever are detected, and the detected engine speed, pump load pressure, From the amount of operation,
The engine output horsepower, the target discharge flow rate, and the target pump absorption horsepower are calculated, and the calculated engine output horsepower and the target pump absorption horsepower are compared. If the target pump absorption horsepower is equal to or less than the engine output horsepower, the target discharge is calculated. When the flow rate is secured by controlling only the tilt angle of the hydraulic pump, and when the target pump absorption horsepower exceeds the engine output horsepower, the target discharge flow rate is secured by controlling the engine speed. A method for controlling a hydraulic machine. 4. The system according to claim 2, wherein the engine speed is reduced to a low-speed operation speed after a predetermined delay time has elapsed from the time when all of the operation levers are in the neutral state. Or the control method of the hydraulic machine according to claim 3. 5. The engine according to claim 1, wherein the engine is always operated at the set speed when a set speed operation commanded to a set speed set by a throttle lever is instructed. The control method for a hydraulic machine according to claim 3. 6. When the target pump absorption horsepower exceeds the maximum output horsepower of the engine, the rotation speed of the engine is maintained at the rotation speed that becomes the maximum output horsepower, and the tilt angle of the hydraulic pump is controlled. 4. The control method for a hydraulic machine according to claim 2, wherein the target pump absorption horsepower does not exceed the maximum output horsepower of the engine.