JP2000080941A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent engine stalling while executing isochronous control. SOLUTION: This engine controller performs isochronous control for maintaining an engine at a set rotational speed NT lower than a specified load rate, suspends the isochronous control when an engine load rate reaches the specified load rate or higher, and performs tilt control for increasing a fuel injection quantity at a specified rate according to a drop NR in the engine rotation with respect to the set rotation NT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an engine control device, and more particularly to an engine control device suitable for an industrial engine.

[0002]

2. Description of the Related Art The following two types of control methods for an industrial diesel engine having an electronic governor applied to various industrial equipment such as a hydraulic shovel are generally used.

As shown in FIG. 6, one is called regulation control (or droop control).
This is because, for example, when the engine speed is set by the driver during the no-load operation (idle operation) of the engine before the use of the industrial equipment, the engine speed is reduced according to the increase in the load on the equipment during the use of the industrial equipment. Control. This control is performed when the accelerator pedal is fixed in a diesel engine with a mechanical governor.
It is similar to the situation where the engine speed decreases as the engine load increases.

The other is called isochronous control. This control is such that when the engine speed is set by the driver, the engine speed is kept constant at the set speed irrespective of the fluctuation of the load on the equipment. In particular, in a generator, the power generation frequency changes due to a change in the number of revolutions. Therefore, this control is effective for industrial equipment that does not like such a change in the number of revolutions. In this control, the fuel injection amount is increased in accordance with an increase in the engine load (engine torque), so that the engine speed is kept constant.

[0005]

In controlling an industrial engine, engine stall due to overload must be sufficiently considered.

That is, when a hydraulic shovel is taken as an example of the industrial equipment, the hydraulic pump is directly driven by the engine, and the shovel is driven by the hydraulic pressure generated thereby.
At this time, lift heavy objects during excavator work,
When digging into hard ground, an excessively large load may be suddenly applied. At this time, if the required load is allowed as it is, the engine may stall exceeding the maximum load generated by the engine.

As shown in FIG. 6, in both the regulation control and the isochronous control, an engine stall occurs near the intersection of the engine maximum torque curve and the control line.

In order to prevent this, in the conventional regulation control, the degree of approach to the engine stall limit is grasped by monitoring the fall of the engine speed from the set engine speed, and when approaching the engine stop limit, the discharge side of the hydraulic pump is controlled. To reduce the load on the hydraulic pump so as not to overload the engine.

However, the regulation control is not suitable for industrial equipment such as the above-described generator which reluctates rotation speed change. In addition, during idling operation while the equipment is stopped, the engine rotation speed becomes the highest and the vibration noise is reduced. Has the disadvantage that the That is, if a constant load (rated torque) is to be obtained by the regulation control, the number of revolutions in the no-load operation must be higher than that in the load operation, and the vibration noise increases.

On the other hand, the isochronous control does not have such a disadvantage, but instead has a problem that it is difficult to avoid the engine stall because the engine speed is constant irrespective of the load. .

That is, in the hydraulic industrial equipment, an electronic control unit for hydraulic control, that is, a hydraulic controller is provided independently of an electronic control unit for engine control (hereinafter referred to as an engine ECU), and the hydraulic controller controls a hydraulic cylinder and the like. It is supposed to. Then, the hydraulic controller receives the signal of the set rotation speed set by the driver from the engine ECU, compares the signal with the pump rotation speed (= engine rotation speed), and when the pump rotation speed falls by a predetermined rotation speed from the set rotation speed. , It is determined that the engine is at the engine stall limit, and the above-described pump relief is executed.

In this sense, in the regulation control, the engine speed drops as the load increases, so that the hydraulic controller can easily prevent pump relief and engine stall. However, since the isochronous control is basically a constant engine speed, the engine stall limit cannot be determined.
Cannot perform pump relief. If this is to be done, the control system of the hydraulic controller itself must be changed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an engine control device capable of reliably preventing engine stall while executing isochronous control.

[0014]

An engine control device according to the present invention performs isochronous control for maintaining an engine at a set rotation speed below a predetermined load ratio, and when the engine load ratio exceeds the load ratio, The above-mentioned isochronous control is stopped, and a tilt control for increasing the fuel injection amount at a predetermined rate in accordance with the fall of the engine speed with respect to the set number of revolutions is performed.

According to this, the engine can be isochronously controlled up to the load factor. When the load ratio becomes equal to or higher than the above-mentioned load ratio, the isochronous control is stopped, and the control is shifted to the inclination control. Therefore, a decrease in engine speed is allowed, and pump relief and engine stall prevention by the hydraulic controller can be performed easily and reliably.

Here, a hydraulic pump driven by the engine, a relief valve provided on the discharge side of the hydraulic pump, and opening of the relief valve when the drop of the engine rotation exceeds a predetermined number of rotations. Preferably, it is combined with a hydraulic controller.

[0017]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 5 is a block diagram of an engine / hydraulic control system to which the present invention is applied. The system applies here to a hydraulic excavator. The portion surrounded by the chain line A constitutes the engine control device, and the portion surrounded by the chain line B constitutes the hydraulic control device. In the engine control device A, the diesel engine 2 having the electronic governor 1 is controlled. The engine 2 has a hydraulic control device B
Is directly driven.

In the hydraulic control device B, the hydraulic pressure P _P generated by the hydraulic pump 3 is sent to a hydraulic cylinder 5 after passing through a relief valve 4 provided on the discharge side. The hydraulic cylinder 5 substantially operates or drives the shovel. Relief valve 4 is opened and closed controlled on the basis of the relief signal S _R transmitted from the hydraulic controller 6 as a hydraulic control electronic control unit. At the time of the opening operation, the oil discharged from the hydraulic pump 3 is relieved, and at the time of the closing operation, the oil is passed toward the hydraulic cylinder 5.
Although the hydraulic control device B also has a control system that controls the operation of the hydraulic cylinder 5, the description is omitted here because it is not directly related to the present invention.

In the engine control unit A, an electronic control unit for engine control (hereinafter referred to as engine ECU) 7
Is provided, whereby the electronic governor 1 is operated, and the fuel injection amount Q of the engine 2 is controlled. As will be described in detail later, the engine ECU 7 determines the throttle sensor value sent from the throttle sensor 8 and
Based on the mode command signal sent from the hydraulic controller 6, the set rotation speed _NT is determined.
_The target rack position _XT is determined based on _T, and a signal corresponding to the target rack position XT is output to the electronic governor 1 to control the fuel injection amount Q. The engine ECU 7, commensurate from engine speed sensor 9 provided in the engine 2, together with a signal commensurate with the engine rotational speed N _E is transmitted from the rack sensor 10 provided in the electronic governor 1, the actual rack position X _R Is sent. Among these signals, a signal indicating the set rotation speed _NT is transmitted from the engine ECU 7 to the hydraulic controller 6.

Next, control contents of the present system will be described.

FIG. 1 is a two-dimensional map showing the contents of the fuel injection control of the engine 2. The horizontal axis represents the engine speed _NE .
The vertical axis represents the engine load (engine torque). In such an engine control device, the engine 2 is controlled to a predetermined load factor, here a set rotational speed _NT up to a 90% load factor.
When the load ratio becomes equal to or higher than the load ratio, the isochronous control is stopped, and the inclination control is performed to increase the fuel injection amount at a predetermined rate in accordance with the drop of the engine rotation with respect to the set rotation speed _NT . ing.

[0023] That is, ECU 7 sets a set rotation speed N _T by the method described below, during the execution of the isochronous control, a feedback control is intended to adjust the engine speed N _E to the set rotational speed N _T. Specifically, compared with the actual engine speed N _E is the set rotational speed N _T, the target rack position X _T is determined. The electronic governor 1 is feedback controlled so that the actual rack position X _R to the target rack position X _T is equal.

In FIG. 1, when the engine speed is constant, the fuel injection amount Q gradually increases as the engine load increases. The torque curve shown by the solid line is the maximum load line at which the engine load or the fuel injection amount Q becomes maximum for each engine speed. On the other hand, the torque curve shown by the broken line is a 90% load line in which the engine load or the fuel injection amount Q becomes 90% of the maximum value for each engine speed. In other words, the 90% load line is a series of points where the ratio of the actual load to the maximum load, that is, the load factor is 90%.

[0025] Now, the required load for the hydraulic pump 3 is increased when the load on the hydraulic cylinder 5 is increased, because it will Ochiyo the rotational speed N _E of the directly coupled engine 2 in this,
The engine ECU 7 counteracts this with the fuel injection amount Q
Increasing the, Komu combined engine speed N _E to the set rotational speed N _T. That is, to perform the isochronous control to along the rotational speed constant line L _C FIG. However, up to even 90% load point P effect such isochronous control, ECU 7 After a further executes tilt control be along the inclined load line L _I to break point of the load point P.

[0026] That is, as shown in FIG. 2, by which stops the isochronous control, the engine rotational speed N _E is as drops from the setting rotational speed N _T as the increase of the load.
Therefore ECU7, for each drop of 1 rpm, continue adding the fuel injection amount Qi which is set in advance in the fuel injection quantity Q _P 90% load point P, the target rack position X this sum as a target fuel injection amount Q _T Determine _T. Accordingly, at a position where a 90% load point than P, it is possible to engine control, such as along the inclined load line L _I, also it is fuel injection amount Qi is set such that said.

The details will be described later, since the fall in the engine rotational speed N _E is allowed as will facilitate the determination of engine stall limit, pump relief so can be easily and reliably.

Here, a method of setting the set rotation speed _NT will be described. First, a signal of a value corresponding to the operation amount of the lever or the like by the driver is used as the throttle sensor value as the throttle sensor 8.
From the ECU 7. This throttle sensor value is 0
Take a value of ~ 100%. Next, the driver switches the mode switch 1
When 1 is selected, a switch signal is sent to the hydraulic controller 6, and a mode command signal is sent from the hydraulic controller 6 to the ECU 7. The ECU 7 determines the set rotation speed _NT from both the throttle sensor value and the mode command signal.

Here, the mode is for designating the upper limit value or the set width of the set rotational speed _NT . In the mode switch 11, a plurality of upper limit values can be arbitrarily selected. It is assumed that 2000 rpm is selected as the upper limit and the throttle sensor value is 50%. Idle speed 1200
Assuming rpm, the ECU 7 determines the set number of revolutions _NT as follows.

N _T = (2000−1200) × 50/100 + 1200 = 1600 rpm Next, specific control contents of the engine ECU 7 and the hydraulic controller 6 will be described.

FIG. 3 shows the control contents of the engine ECU 7. This control is repeatedly executed at predetermined control times.
First, the engine ECU 7 reads the throttle sensor value from the throttle sensor 8 and the mode from the hydraulic controller 6 in step 31. Then, at step 32, the set rotational speed _NT is determined. In step 33, it calculates the fuel injection quantity Q _P at 90% load point P when the engine speed N _E and the set rotation speed N _T, the fuel injection quantity map which is stored in advance. In step 34, it reads the current engine speed N _E and the current and target fuel injection amount Q _T.

[0032] Then, in step 35, compares the fuel injection quantity Q _P current target fuel injection amount Q _T 90% load point. Q
Proceed to the _T <Q _P If the step 36 to execute the isochronous control. If Q _T ≧ Q _{P, the} routine proceeds to step 37, where the rotational difference Nf between the current engine rotational speed N _E and the set rotational speed _NT is Nf =
To calculate the N _T -N _E. Thereafter, in step 38, the target fuel injection amount Q _T is calculated by the equation Q _T = Nf × Qi + Q _P.

FIG. 4 shows the control contents of the hydraulic controller 6. This control is also repeatedly executed at predetermined control times.
First, the hydraulic controller 6 determines in step 41 that the engine EC
The set rotational speed _NT is read from U7. Next, step 42
In, it reads the pump rotational speed N _P of the current hydraulic pump 3. Since the hydraulic pump 3 and the engine 2 is connected directly, pump speed N _P is equal to the engine speed N _E. Next, at step 43, calculates the value of N _T -N _P, (in this case N _PR = 20 rpm) set the value in advance, predetermined rotational speed N _PR is compared with. Proceeds to step 44 when the N _T -Np> N _PR,
The relief valve 4 is opened. When the N _T -Np ≦ N _PR proceeds to step 45, the relief valve 4 is closing operation.

According to this, in a region where the engine load is 90% load or more, the engine rotational speed N _E is the set rotational speed N _T
On the other hand, at the moment when N _PR = 20 rpm, the pump relief is executed, and the load on the engine 2 is reduced. This makes it possible to effectively and reliably prevent engine stall due to overload.

In particular, the control flow of the hydraulic controller 6 shown in FIG. 4 is the same as the conventional one. That is for the hydraulic controller 6 Regulation control, small value N _PR was relatively large value when the regulation control (20Rp
m) is set again. When combined with the engine ECU7 performing this hydraulic controller 6 isochronous control only, since the engine rotational speed is always constant, without having to determine the N _T -Np> N _PR hydraulic controller 6 side, the pump relief is not executed indefinitely. Therefore, a situation of overload immediately stalling may occur.

The present device stops the isochronous control just before the engine stall limit and allows the engine speed to drop. Therefore, even when combined with the hydraulic controller 6, the set value N
Stall prevention can be reliably performed only by changing the _PR . In addition, since the isochronous control is performed in the normal use area, the advantages of the isochronous control such as low vibration noise are suitable for industrial equipment that does not want to change the rotation speed.

In this apparatus, the isochronous control and the inclination control are separated at a 90% load factor. However, the value of the load factor is not limited to 90% and can be arbitrarily changed. However, in view of the gist of the present invention, it is preferable to perform the isochronous control up to the highest possible load ratio before the engine stall limit.
Also, the predetermined rotation speed N _PR is not limited to 20 rpm, but it is necessary to set the rotation speed before shifting to the tilt control and before reaching 100% load factor (point F in FIG. 2). The hydraulic pump need not necessarily be directly connected to the engine. The method of setting the set rotation speed _NT is not limited to the above method.

Various other embodiments of the present invention are conceivable. The present invention can be applied not only to hydraulic excavators but also to any industrial equipment, and can also be applied to gasoline engines.

[0039]

In summary, according to the present invention, an excellent effect of preventing engine stall while executing isochronous control is exhibited.

[Brief description of the drawings]

FIG. 1 is a map illustrating control contents of an engine control device according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a flowchart showing control contents of an engine ECU.

FIG. 4 is a flowchart showing control contents of a hydraulic controller.

FIG. 5 is a block diagram of an engine / hydraulic control system to which the present invention is applied.

FIG. 6 is a map illustrating control contents of regulation control and isochronous control.

[Explanation of symbols]

2 Engine 3 Hydraulic pump 4 Relief valve 6 Hydraulic controller 7 Engine ECU A Engine control device N _R Predetermined rotation speed _NT Set rotation speed

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2D003 AA01 AB06 BB01 CA02 DA04 DB04 DB05 DC02 3G060 AA08 AB01 AC08 CA01 CB07 DA02 GA03 3G093 AA08 AA14 BA05 CA05 DA01 DA06 DA10 DB00 DB22 EA05 FA10 3G301 HA02 HA28 JA31 KA04 NC03 MA03 PA11A PB04A PE01A PG00A

Claims (2)

[Claims] An isochronous control for maintaining an engine at a set speed below a predetermined load factor is performed. When the engine load factor becomes equal to or more than the load factor, the isochronous control is stopped, and the engine for the set speed is stopped. An engine control device for performing a tilt control for increasing a fuel injection amount at a predetermined rate according to a decrease in rotation. 2. A hydraulic pump driven by the engine, a relief valve provided on a discharge side of the hydraulic pump, and a hydraulic pressure for opening the relief valve when a drop in the engine rotation exceeds a predetermined number of revolutions. The engine control device according to claim 1, wherein the engine control device is combined with a controller.