JPH0437251Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an exhaust gas recirculation control device for a diesel engine.

(Prior Art) Some exhaust gas recirculation control devices for diesel engines are designed to control the amount of EGR (exhaust gas recirculation) according to the accelerator opening degree. For example, as shown in Japanese Patent Application Laid-Open No. 56-110536, EGR is performed when the accelerator opening is below a set value, but when the accelerator opening exceeds this set value, EGR is cut and the EGR amount is reduced. There is one that has two levels of adjustment.

In addition, when the engine load is low and the accelerator opening is smaller than the first set value, a large amount of EGR is performed, and when the accelerator opening exceeds the first set value and reaches the second set value and the engine is at a medium load, EGR is performed more than at low load. Some systems perform a small amount of EGR, cut off EGR when the engine load is high when the accelerator opening exceeds a second set value, and adjust the EGR amount in three stages depending on the accelerator opening.

(Problem to be solved by the invention) However, in the above-mentioned conventional method, changes in fuel temperature cause changes in the fuel injection amount even at the same accelerator opening, and therefore the fuel injection amount is set according to the accelerator opening. This causes a problem in that the EGR zone is changed, which is unfavorable for engine operation.To elaborate on this point, in a diesel engine, the larger the accelerator opening, the larger the fuel injection amount. Even if this accelerator opening is the same, the viscosity of the fuel changes due to temperature changes, which causes a difference in the amount of fuel leakage, especially in the fuel injection pump, and the actual amount of fuel leakage in the fuel injection pump is higher when the engine is cold than when it is warm. The amount of fuel injected increases. Therefore, the accelerator opening degree for maintaining the same fuel injection amount, that is, for maintaining steady running, is made smaller when the vehicle is cold than when it is warm.

On the other hand, the EGR zone, that is, the accelerator opening setting value when changing the EGR amount, is set in anticipation of the fuel injection amount according to this accelerator opening, taking into consideration engine output, exhaust gas countermeasures, and misfires. It is set optimally.

Therefore, even if the accelerator opening is the same, the actual fuel injection amount will change depending on the temperature, which means that the EGR zone is determined in advance to ensure engine output and take measures to prevent exhaust gases. This will cause an error in the engine operation, which is unfavorable for engine operation.

Therefore, the purpose of this invention is to set the EGR zone according to the accelerator opening.
An object of the present invention is to provide an exhaust gas recirculation control device for a diesel engine that can always perform optimal EGR by compensating for deviations in the EGR zone caused by changes in actual fuel injection amount due to temperature changes.

(Means and actions for solving the problem) In order to achieve the above-mentioned purpose, in the present invention, the set value of the accelerator opening degree for changing the EGR amount is corrected according to the fuel temperature. In other words, the correction is made to correspond to the actual fuel injection amount. Specifically, as shown in Fig. 1, upon receiving the output from the accelerator opening detection means, if the accelerator opening is larger than a predetermined set value of the accelerator opening, the EGR is activated. When the accelerator opening is smaller than the set value, the EGR
Assuming that the exhaust gas recirculation control device for a diesel engine is configured to increase the amount of fuel, the present invention includes a fuel temperature detection means for detecting the temperature of the fuel, and an output from the fuel temperature detection means to detect when the fuel temperature is low. Compared to when the fuel temperature is high,
The present invention is configured to include: a correction means for correcting the set value of the accelerator opening degree in a direction of decreasing it;

With this configuration, changes in the actual fuel injection amount due to changes in fuel temperature can be compensated for,
Optimal EGR can be performed at all times.

(Example) An example of the present invention will be described below based on the attached drawings.

In FIG. 2, 1 is a cylinder (combustion chamber) of a diesel engine in which a fuel injection valve 2 is disposed, 3 is an intake passage, and 4 is an exhaust passage.

An EGR passage 5 is led out from the exhaust passage 4,
This EGR passage 5 is branched into two branch passages 5a and 5b, a first and a second branch passage, in the middle.
a and 5b are each opened to the intake passage 4. A first EGR valve 6 is connected to the first branch passage, and a second EGR valve 7 is connected to the second branch passage 5b.

Each of the EGR valves 6 and 7 is of a negative pressure operating type, which opens when receiving negative pressure.
Two branch passages 9a or 9b, a first and second branch passage, of a negative pressure passage 9 extending from a negative pressure pump 8 are connected to each of these EGR valves 6, 7.
A first solenoid valve 10 is connected to the branch passage 9a, and a second solenoid valve 11 is connected to the second branch passage 9b. Both solenoid valves 10, 11
supply negative pressure to the corresponding EGR valve when turned on or energized, and conversely supply negative pressure to the corresponding EGR valve 6 when turned off or demagnetized, respectively.
Atmospheric pressure is supplied to 7.

Therefore, when the first solenoid valve 10 is turned on, negative pressure is supplied to the first EGR valve 6 and the first EGR valve 6 is opened. Similarly, when the second solenoid valve 11 is turned on, the second EGR valve 7 is opened. As a result, both solenoid valves 1
When both solenoid valves 10 and 11 are closed, EGR is cut off, and when both solenoid valves 10 and 11 are turned on, a large amount of EGR is cut off through the two EGR valves 6 and 7.
is performed and only the first solenoid valve 10 is turned on, a relatively small amount of EGR will be performed. That is, turning on the solenoid valves 10 and 11,
The EGR amount is adjusted in three stages depending on the off state.

Reference numeral 12 in FIG. 2 is a control unit, and this control unit 12 includes a rotation sensor 13 for detecting the engine rotation speed, an accelerator sensor 14 for detecting the accelerator opening, and a fuel injection valve 2 through a pipe 17. A signal from a temperature sensor 16 that detects the temperature of the fuel in the fuel injection pump 15 that supplies the fuel is input. In addition, this control unit 1
2, the signal is output to both the solenoid valves 10 and 11 described above.

Now, next, the above-mentioned control unit 12
EGR control will be explained with reference to the flowchart shown in FIG. 3, but in this example,
As shown in FIG. 5, the EGR zone is set using the engine speed as a parameter in addition to the accelerator opening. In this FIG. 5, the region α is the region where EGR is performed by both EGR valves 6 and 7, the region β is the region where EGR is performed only by the first EGR valve 6, and the other regions are
EGR is now being cut off.

Based on the above, in FIG. 3, engine speed N, accelerator opening θ, and fuel temperature T are sequentially read (steps S1, S2, and S3).

Thereafter, in step S4, the actual accelerator opening degree θ in step S2 is corrected as θ' based on the fuel temperature T. This correction is performed so that the higher the fuel temperature T is, the smaller the actual fuel injection amount is, so the higher the fuel temperature T is, the larger the corrected accelerator opening θ' becomes. In other words, if the EGR zone is set as shown in Figure 5 with the basic condition being that the fuel temperature T is a medium temperature of 40℃, for example, if the fuel temperature is higher than this basic 40℃, the actual fuel injection amount will decrease. In this case, θ' is set as the accelerator opening degree to compensate for this decreased fuel injection amount and obtain the same fuel injection amount corresponding to the accelerator opening degree θ at 40° C. (step S2). Similarly, when the fuel temperature T is lower than the basic 40° C., the corrected accelerator opening θ' is corrected to be smaller than the actual accelerator opening θ.

After the above step S4, in step S5,
The EGR zone is determined based on the basic map shown in FIG. 5, that is, based on the engine speed N and the corrected accelerator opening θ'. In the determination at step S5, if the operating state of the engine is not in both the α and β ranges, step S6 is performed.
The EGR is cut off by turning off both solenoid valves 10 and 11. Further, in the determination at step S5, if it is determined that the operating state of the engine is in the region β, the process proceeds to step S7, where the first solenoid valve 10 is turned on and the second solenoid valve 11 is turned on.
is turned off and a relatively small amount of EGR is performed.
Further, in the determination at step S5, if it is determined that the operating state of the engine is in the region α, the process moves to step S8, and both solenoid valves are
Both 0 and 11 will be turned on and a large amount of EGR will be performed.

With the above control, the EGR zone when the fuel temperature T is lower than the basic state (medium temperature, 40℃) shown in Figure 5 is shown in Figure 4, and the fuel temperature T
When the temperature is higher than that shown in Figure 5,
The EGR zone is shown in Figure 6. As is clear from Figures 4 to 6, the maximum actual accelerator opening for EGR is set as θ ₁ at low temperatures, θ ₂ (= θ = θ') at medium temperatures, and furthermore at high temperatures. Although shown as θ ₃ , as θ ₁ <θ ₂ <θ ₃ , the lower the fuel temperature T, the smaller the actual accelerator opening when EGR is cut off (in the upper limit range of β). Of course, the upper limit range of α is similarly made smaller as the fuel temperature T becomes lower.

In this way, changes in fuel injection amount due to changes in fuel temperature are continuously and variably compensated for, and always in accordance with a predetermined predetermined EGR zone (EGR zone in the basic state shown in Figure 5). In other words, so that the EGR amount corresponds to the fuel injection amount,
EGR will be performed.

Although the embodiment has been described above, when the control unit 12 is configured with a microcomputer,
It may be either digital or analog. In addition, if correction due to fuel temperature changes is to be performed in stages rather than continuously variable, for example, a multi-contact system is used in which the contacts are switched according to the fuel temperature, and each contact has a different resistance value. By connecting the relay in which the resistor is incorporated between the accelerator sensor 16 and the control unit 12,
The control unit 1 converts the output (for example, voltage value) from 6 into a value corresponding to the mutually different resistance values.
2 should be input.

Further, it is preferable to detect the fuel temperature at the fuel injection pump 15, which is the part that causes the largest difference in fuel injection amount depending on the temperature, or at the fuel system path downstream thereof.
It is preferable to detect the temperature at the fuel injection pump 15 part from the viewpoint of ease of installing the temperature sensor.

(Effects of the invention) As is clear from the above, the invention has the following effects:
By compensating for changes in fuel injection amount due to changes in fuel temperature, EGR can always be performed based on a predetermined optimal EGR zone.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2 is an overall system diagram showing an embodiment of the invention, Fig. 3 is a flowchart showing an example of control of the invention, and Figs. 4 to 6 are fuel temperature Graph showing the relationship between accelerator opening and EGR zone. 2... Fuel injection valve, 3... Intake passage, 4... Exhaust passage, 5... EGR passage, 5a, 5b... Branch passage, 6, 7... EGR valve, 8... Negative pressure pump, 9... ... Negative pressure passage, 9a, 9b... Branch passage,
10, 11... Solenoid valve, 12... Control unit, 14... Accelerator sensor, 15... Fuel injection pump, 16... Temperature sensor.

Claims (1)

[Claims for Utility Model Registration] Receiving the output from the accelerator opening detection means, a direction in which the EGR amount is reduced when the accelerator opening is larger than a predetermined set value of the accelerator opening. When the accelerator opening is smaller than the set value, the EGR
An exhaust gas recirculation control device for a diesel engine configured to change the amount in a direction of increasing the amount of fuel, comprising a fuel temperature detection means for detecting the temperature of the fuel, and a signal from the fuel temperature detection means to detect the fuel temperature when the fuel temperature is low. An exhaust gas recirculation control device for a diesel engine, comprising: correction means for correcting the set value of the accelerator opening to be smaller than when the accelerator opening is high.