JPS6224036Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is based on the exhaust gas recirculation (hereinafter referred to as
(EGR) control device.

Conventionally, EGR control for diesel engines involves converting the position of the fuel injection pump's injection amount control lever or the amount of change in ventilate negative pressure in the intake passage into an electrical signal, or converting negative pressure into negative pressure with certain characteristics. etc. are detected as the engine load, and the EGR amount is controlled by controlling the EGR control valve in accordance with the detected signal (see, for example, Japanese Patent Laid-Open No. 53-90519).

However, with this load detection method, the error between the actual engine load, that is, the fuel injection amount, and the detected value of the engine load is extremely large, and it is difficult to say that good EGR control is necessarily performed.

The present invention was developed in view of the conventional situation, and focuses on the fact that the engine exhaust temperature has a close correspondence with the engine torque, that is, the load, and performs EGR control using the engine exhaust temperature as one of the load detection signals. The present invention provides an EGR control device for a diesel engine.

The present invention will be explained in detail below based on illustrated embodiments.

In FIG. 1 showing one embodiment, an EGR passage 4 connecting an intake passage 2 and an exhaust passage 3 of an engine 1 has a
An EGR control valve 5 is interposed. The control valve 5 is connected to and operated by an air actuator 6, and a pressure chamber 6a of the actuator 6 is communicated with a vacuum pump 8 via a solenoid valve 7.

The solenoid valve 7 has a controller 9 connected to a battery.
It is connected to the output terminal of and controlled to open and close. The controller 9 receives detection signals from a temperature sensor 10 disposed in the exhaust passage 3 to detect the exhaust gas temperature, a rotation speed sensor 11 to detect the engine rotation speed, and a cooling water temperature sensor 12 to detect the engine cooling water temperature. A control signal is output based on these signals.

Here, the torque characteristic with respect to the rotational speed of the engine is shown in FIG. 2 using the exhaust temperature as a parameter. For example, the engine rotation speed ranges from N ₁ (for example, 1000 rpm) to N ₂ in which EGR is performed.
(e.g. 2800rpm) and the exhaust temperature T (e.g. 400rpm)
℃) or less, the area becomes as shown by diagonal lines in FIG. That is, EGR is stopped in a low engine speed region where EGR produces exhaust odor and deteriorates combustion performance, and in a high exhaust temperature region where the amount of NOx generated is relatively small and a drop in output becomes a problem. Although not shown, EGR is unconditionally stopped when the cooling water temperature is below a set value, such as when it is cold.

In this case, the coolant temperature detected by the coolant temperature sensor 12 exceeds the set value, and the temperature sensor 10 and rotation speed sensor 11 detect the exhaust temperature and engine rotation speed shown in the shaded area, respectively. At this time, a valve opening signal is transmitted from the controller 9 to the solenoid valve 7. As a result, the vacuum negative pressure generated by the vacuum pump 8 is introduced into the pressure chamber 6a of the air actuator 6 via the opened solenoid valve 7.
EGR control valve 5 is opened to perform EGR.

Next, as shown in the shaded area in Figure 3, when EGR is stopped when the engine torque is below the set value _T0 in the engine speed range _N1 to _N2 , the exhaust temperature remains constant at the engine speed. Taking advantage of the fact that when engine torque increases in proportion to engine torque, and when engine torque is constant, it increases in proportion to engine rotational speed, the following procedure is performed.

First, by correcting the engine torque T ₀ by the engine rotation speed, the exhaust temperature corresponding to the engine torque T ₀ is set to t ₀
This is stored in the controller 9 in advance. For example, the exhaust temperature ti is determined by the temperature sensor 10.
is detected and the engine rotation speed Ni (N ₁ ≦Ni≦N ₂ ) is detected by the rotation speed sensor 11, the controller 9 corrects the exhaust gas temperature ti to set the corrected exhaust gas temperature.
Calculate ti′=ti・N ₀ /Ni. For example, as shown in Figure 4, when ti′≦to, the solenoid valve 7 is opened to perform EGR, and when ti′>to, EGR is stopped. It may be configured as follows.

In this way, since the exhaust temperature faithfully reflects the actual operating condition of the engine, highly accurate load detection can be performed, including correction for injection timing errors and variations in combustion performance from engine to engine. enables highly accurate EGR control.

Furthermore, it is possible to detect loads with high accuracy in response to differences in atmospheric conditions (mainly atmospheric temperature, but also humidity), and therefore, it is possible to detect loads with high accuracy in response to differences in atmospheric conditions (mainly atmospheric temperature, but also humidity). Ideal EGR control can be performed in response to differences in conditions in low-temperature regions and usage periods (summer, winter, etc.).

As explained above, according to the present invention, the load condition of the engine can be accurately determined by detecting the exhaust temperature, and this characteristic includes injection timing errors,
Since it includes corrections for variations in combustion performance between engines and differences in engine usage environments such as atmospheric conditions, there is no need to make adjustments for each engine, and moreover, highly accurate EGR control can be performed.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
Fig. 2 is an engine torque characteristic diagram showing an example of the EGR-controlled operating range in the same embodiment, Fig. 3 is an engine torque characteristic diagram showing another example of the EGR-controlled operating range according to the present invention, and Fig. 4 is an engine torque characteristic diagram showing an example of the EGR-controlled operating range according to the present invention. FIG. 4 is an engine torque characteristic diagram obtained by correcting the exhaust gas temperature in FIG. 3; 1... Engine, 2... Intake passage, 3... Exhaust passage, 4... EGR passage, 5... EGR control valve, 6...
...Air actuator, 6a...Pressure chamber, 7...
Solenoid valve, 8... Vacuum pump, 9... Controller, 10... Temperature sensor, 11... Rotation speed sensor, 12... Cooling water temperature sensor.

Claims (1)

[Scope of utility model registration request] The exhaust passage and the intake passage are connected by an exhaust recirculation passage equipped with an exhaust recirculation control valve, and a temperature sensor is provided to detect the exhaust temperature, and the exhaust temperature detected by the temperature sensor is used as one load detection signal. An exhaust recirculation control device for a diesel engine, characterized in that the exhaust recirculation control device for a diesel engine is provided with a valve control means for controlling the exhaust recirculation control valve and thereby controlling the amount of exhaust recirculation.