JPS6312248B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting exhaust gas recirculation flow rate in an engine.

EGR, which recirculates a portion of engine exhaust gas into the intake system to reduce nitrogen oxides in the exhaust gas
system has been realized. This EGR system is equipped with a flow rate control valve in the exhaust gas recirculation path and controls the flow rate of recirculated exhaust gas by controlling the opening degree of this valve. Particulates in the exhaust gas accumulate in the circulation path, especially near the control valve, and the flow rate decreases relative to the amount of movement of the control valve.Therefore, the amount of movement of the control valve is further increased to reduce the exhaust gas flow rate. It is desirable to perform control such as compensation.

However, since the recirculated exhaust gas is at a high temperature, it is difficult to directly detect this flow rate.Therefore, Japanese Patent Application Laid-Open No. 54-39732 proposes a system that indirectly detects the EGR rate from various engine parameters. It is proposed in the official gazette. In this one, EGR
The difference between the intake pipe pressure P _B when performing EGR and the intake pipe negative pressure P _BO when EGR is not performed, which is determined by the rotational speed N and air amount Q at this time, P _B −P _BO is P _B The EGR rate is calculated by dividing by
In order to find the intake pipe negative pressure P _BO when not performing, it is necessary to detect the rotation speed N and air amount Q.
In particular, the air amount sensor is expensive and requires installation space, so providing it specially poses a practical problem. For this reason, it is possible to share the air quantity sensor used in the fuel injection control device, but this is not possible with speed density type models that do not use an air quantity sensor, and a special expensive air quantity sensor is required. There is a problem that requires it. In addition, in this conventional system, in order to find the intake pipe negative pressure P _BO when the above-mentioned EGR is not performed, P _BO =
The arithmetic expression aQ/N _{+b (a and b are constants) is memorized and P BO is} calculated using this arithmetic expression. It is difficult to obtain accurately, and for this reason
There is also the problem that the detection accuracy of the EGR rate decreases.

[Means for solving problems]

The method for detecting the flow rate of exhaust gas recirculation in an engine according to the present invention is based on two of the engine parameters of intake pipe negative pressure, engine speed, and throttle opening in the operating state of an engine that does not perform exhaust gas recirculation. other 1 corresponding to the value
The values of the three engine parameters are set and stored in the storage means in advance, and the three engine parameters are detected when the engine is actually operated with exhaust gas recirculation, and the values of the three engine parameters detected are The data in the storage means is read in correspondence with the two engine parameters, the read data is compared with the other detected parameter, and the exhaust gas recirculation flow rate is detected based on the difference. This is what I did.

[Effect]

In this invention, the three parameters of the engine are intake pipe negative pressure, rotation speed, and throttle opening, and even if two of these three engine parameters are the same with and without EGR, Since one other engine parameter has a different value and the difference corresponds to the EGR amount, the detected values of the above two engine parameters were stored in the storage means in correspondence with this detected value.
The value of the other parameter when EGR is not performed is read out, this value is compared with the detected value of the other parameter, and the EGR amount is detected based on the difference. Here, the value stored in the storage means is the value of one other parameter when EGR is not performed, so just by reading this value, the accurate parameter value can be obtained without the need for conventional calculations. The EGR amount can be determined accurately and quickly. Also, since the EGR amount is detected from the throttle opening, rotation speed, and intake pipe negative pressure, an air amount sensor is not required. It is inexpensive and can be put to practical use with a simple configuration.

An embodiment of the present invention shown in the drawings will be described below. That is, in FIG. 1, 1 is the engine, 2
A throttle valve 3 is provided which is manually operated in the intake pipe of this engine. 4 is the above engine 1
This exhaust pipe and the intake pipe 2 are connected by an exhaust gas recirculation passage 5,
An exhaust gas recirculation control valve (EGR valve) 6 is interposed in the recirculation passage 5. The EGR valve 6 has its valve stroke controlled in accordance with a control amount from a control unit (not shown) to control the exhaust gas recirculation flow rate. 7 is a rotation signal generator that generates a rotation signal with a frequency corresponding to the rotation speed of the engine 1; 8 is a rotation speed detection circuit that generates a DC voltage output proportional to the rotation signal frequency;
9 is a throttle opening detector which generates a DC voltage output proportional to the opening of the throttle valve 13; 10;
11 is a negative pressure detector which has a pressure sensitive part 10a that is sensitive to the intake negative pressure and generates a DC voltage corresponding to the intake negative pressure; 11 determines the output level of the rotation speed detection circuit 8 and determines the engine rotation speed N. A rotation level discriminator 12 generates an output when the rotation speed matches the set rotation speed _N1 (actually within a predetermined level range), and 12 discriminates the output level of the throttle opening detector 9 and determines the throttle opening. A throttle opening level discriminator 13 generates an output when θ matches the set opening θ ₁ (actually within a predetermined level range); negative pressure storage means for setting and storing the intake negative pressure P ₁ as a voltage value when the rotation speed N and the throttle opening θ are respectively the set rotation speed N ₁ and the set throttle opening θ ₁ during operation; 14 is a gate circuit for reading the output of the negative pressure storage means 13 when outputs are generated from both the level discriminators 11 and 12; 15 is the output of the negative pressure storage means 13 that has passed through the gate circuit 14 and the negative pressure; A deviation detector 16 detects a deviation from the output of the detector 10, a level detector 16 detects and stores whether the output level of this deviation detector is above or below a set value, and 17 detects a deviation from the output of the detector 10. It is a driven alarm.

Figure 2 shows the characteristics of the intake pipe negative pressure P with respect to the rotation speed N when the throttle opening θ is kept constant at the set value θ _1. The solid line shows the characteristics in the engine operating state without exhaust gas recirculation. The dashed line shows the characteristics under engine operating conditions with exhaust gas recirculation at a predetermined flow rate. In Fig. 2, when the engine is operating without exhaust gas recirculation, the intake pipe negative pressure P at the set throttle opening θ ₁ and the set rotational speed N ₁ is P ₁ ; ₁ is preset and stored in the negative pressure storage means 13 as a voltage value.

Now, the engine 1 takes in fuel along with air from the intake pipe 2, and after combustion, exhaust gas is discharged to the exhaust pipe 4. A part of this exhaust gas is returned to the intake pipe 2 through the passage 5. The recirculated exhaust gas flow rate is controlled by the EGR valve 6. On the other hand, the rotation signal generator 7 generates a rotation signal with a frequency proportional to the rotation speed of the engine 1, and this rotation signal is converted by the rotation speed detection circuit 11 into a DC voltage proportional to the rotation speed. Further, the throttle opening detector 9 generates a DC voltage proportional to the opening of the throttle valve 3. The level of each of these DC voltages is discriminated by level discriminators 11 and 12, and when the rotation speed N and the throttle opening θ match the set rotation speed N ₁ and the throttle opening θ ₁ (when they are within a predetermined level range) ) produces output. When outputs are generated from both level discriminators 11 and 12, that is, when the rotational speed N is N1 and the throttle opening θ is _θ1 , the gate circuit 14 reads out the memory output _P1 of the memory means 13 and uses it as a deviation detector _. 15 to input.
The deviation detector 15 compares the memory output given from the gate circuit 14 and the negative pressure output from the intake negative pressure detector 10, and generates an output corresponding to the difference. Here, the negative pressure downstream of the throttle valve 3 in the intake pipe 2 is as follows:
In the case where this is not done, as shown in FIG. 2, even if the throttle opening degree θ ₁ is the same, the characteristic with respect to the rotational speed N decreases from a solid line characteristic to a broken line characteristic. This is understood from the fact that the direct airflow (negative pressure) downstream of the throttle valve is reduced by the recirculated exhaust gas. Furthermore, the deviation of the broken line characteristic from the solid line characteristic increases as the recirculated exhaust gas flow rate increases. Therefore, the output of the deviation detector 15 is the rotation speed N ₁ and the throttle opening θ ₁
If the intake negative pressure at the time is P ₁ ′, then the difference (P ₁ − _{P 1} ′) with respect to the negative pressure P ₁ under the same conditions N ₁ θ ₁ without exhaust gas recirculation is output. Indicates the value (magnitude) corresponding to the recirculated exhaust gas flow rate.

The output of this deviation detector 15 is sent to a level detector 16.
By determining whether or not the recirculated exhaust gas flow rate has fallen below a predetermined level, it is possible to detect that the recirculated exhaust gas flow rate has fallen below a permissible range, and activate the alarm device 17 to issue a warning to the driver. be able to.

In the above embodiment, when the set rotational speed N ₁ and the set throttle opening θ ₁ are extremely 1.
We have explained how the EGR flow rate is detected from the deviation of the intake negative pressure when EGR is present or not under the operating conditions of the previous section. is stored three-dimensionally in digital memory (ROM),
The EGR flow rate can also be detected in a wide range of operating ranges by sequentially reading each stored data and comparing it with the intake negative pressure when EGR is present and when EGR is present. Further, the present invention is not limited to storing the intake negative pressure among the three parameters of rotation speed, throttle opening degree, and intake negative pressure in the storage means, and any parameter can be stored. Further, since these engine parameters are normally required for an electronic fuel injection control device, if these various sensors are shared, it can be realized without making the device particularly complicated.

As described above, according to the present invention, by changing the exhaust gas recirculation flow rate, the intake negative pressure, engine speed,
Among the three engine parameters of throttle opening, we focused on the fact that even if the conditions for these two engine parameters are the same, there are differences in the values of other parameters, and we detect the exhaust gas recirculation flow rate based on that difference. Therefore, there is no need to directly detect the flow rate of high-temperature exhaust gas, and detection with excellent durability can be achieved. In addition, since the above three parameters are throttle opening, rotation speed, and intake pipe negative pressure, it can be configured inexpensively and compactly without requiring a large and expensive air amount sensor, and the above three parameters when EGR is not performed. Since the other parameter values are stored as they are in the storage means, simply by reading them, the other parameter values mentioned above when EGR is not performed can be determined accurately and quickly. Therefore, the exhaust gas recirculation amount can be detected. can be performed quickly with accurate and simple calculations.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining the operation of FIG. In the figure, 8 is a rotation speed detection circuit, 9 is a throttle opening detector, 10 is a negative pressure detector, 11 and 12 are level discriminators, 13 is a negative pressure storage means, 14 is a gate circuit, and 15 is a deviation detector It is.

Claims (1)

[Claims] 1 Among engine parameters such as intake pipe negative pressure, engine speed, and throttle opening in the operating condition of an engine that does not perform exhaust gas recirculation, part 2
Corresponding to the value of one engine parameter, the value of another engine parameter is set and stored in advance in the storage means, and the above three engine parameters are detected when the engine is actually operated with exhaust gas recirculation. Then, data in the storage means is read corresponding to the two engine parameters out of the three detected engine parameters, and the read data is compared with the other detected parameter. An engine exhaust gas recirculation flow rate detection method that detects the exhaust gas recirculation flow rate based on the difference.