JPH0340217B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an exhaust purification device for a diesel engine. (Prior art) Conventionally, in diesel engines, particulate matter (particle components, mainly C,
Due to the demand for reduction of HC), a filter (adsorption member) is provided in the exhaust passage, but this has the problem of complicating the structure and increasing cost. Therefore, as shown in Japanese Utility Model Application Publication No. 54-58512, for example, an intake throttle valve and an electric heater are provided in the intake passage from the upstream side, and the opening and closing of the intake throttle valve is controlled to efficiently heat the intake air with the electric heater. , to improve engine combustibility and to improve particulate matter (especially
It has been proposed to reduce HC). (The problem that the invention aims to solve) However, in diesel engines as well, it is not only necessary to efficiently heat the intake air to improve engine combustibility and reduce particulate matter (particularly HC). There is also a demand for reducing _NOx by controlling reflux. The present invention has been made in view of these points, and includes:
Exhaust purification for diesel engines that performs intake air heating control and exhaust recirculation control using two intake throttle valves and intake throttle valve control means, and efficiently reduces particulate matter during intake air heating and _NOx during exhaust recirculation. The purpose is to provide a device. (Means for Solving the Problems) In order to achieve the above-mentioned objects, the present invention provides temperature detection means for detecting engine temperature, rotation speed detection means for detecting engine rotation speed, and load detection means for detecting engine load. a detection means, an electric heater for heating intake air disposed in the intake passage, an exhaust gas recirculation passage connecting the intake passage and the exhaust passage, and a downstream end opening of the exhaust gas recirculation passage and an upstream side of the electric heater. an intake throttle valve provided, and the temperature detection means,
Activating the electric heater in an operating range in which the engine temperature is below a predetermined value, the engine speed is below a predetermined rotation speed, and the engine load is below a predetermined load while the engine is operating in response to the outputs of the rotation speed detection means and the load detection means; an intake throttle valve control means for controlling opening and closing of the intake throttle valve based on a control map that increases the opening degree of the intake throttle valve as the engine speed increases; The configuration uses different control maps for the exhaust gas recirculation and exhaust gas recirculation. (Function) The electric heater is operated by the intake throttle valve control means in an operating range where the engine temperature is below a predetermined value, the engine speed is below a predetermined rotation speed, and the engine load is below a predetermined load while the engine is running; The opening and closing of the intake throttle valve is controlled based on a control map that increases the opening degree of the intake throttle valve at least as the engine speed increases. In that case, the intake throttle valve control means uses different control maps when heating the intake air and when recirculating the exhaust gas. For example, during intake air heating, it is controlled by the engine speed and engine load (for example, accelerator opening) (see Fig. 3), and when exhaust gas is recirculated, it is controlled by the engine speed (see Fig. 4). (Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In the exhaust purification device for an indirect injection type four-cylinder diesel engine shown in FIG. 1, 1 is a diesel engine, and a glow plug 4 is arranged in a combustion chamber 3 (specifically, a swirl chamber) of each cylinder 2. . Reference numeral 5 denotes an intake passage, which includes a main intake passage 6 and a passage 4 branching from the main intake passage 6 and communicating with the combustion chamber 3 of each cylinder 2.
The main intake passage 6 has a first air heater 8 as an electric heater for heating the intake air.
However, each branch intake passage 7 is provided with a second air heater 9, respectively. The first and second air heaters 8 and 9 can be controlled independently, and after the engine has completely exploded, the first air heater 8 is connected in series with the glow plug 4 and serves as a dropping resistor during afterglow. The energization is controlled simultaneously with the glow plug 4. Afterglow occurs when, for example, the temperature of the engine cooling water is below 30℃, the engine load (hereinafter referred to as mean effective pressure Pe) is below 0Kg/ ^cm2 ,
Also, when the engine speed is 2000 rpm or less, approximately 6V is applied to the glow plug 4 to prevent misfire. Reference numeral 10 denotes an intake throttle valve, whose opening and closing are controlled by a diaphragm device 11. In the diaphragm device 11, the casing 11a is the diaphragm 1.
1b is divided into a first chamber 11c and a second chamber 11d, and a spring 11e is compressed in the first chamber 11c, and a negative pressure control solenoid valve 1
2 is connected to the negative pressure passage 13.
Further, the diaphragm 11b is linked to the intake throttle valve 10 via a link mechanism 11f extending toward the second chamber 11d. Therefore, the intake throttle valve 10 is
For example, the intake negative pressure is controlled to increase the heating efficiency of the first and second air heaters 8 and 9 in a region where the engine cooling water temperature is 30 to 60°C, the engine load is 1 kg/cm ² or less, and the engine rotation speed is 2000 rpm or less. . 14 is an exhaust gas recirculation passage (hereinafter referred to as EGR passage)
The exhaust passage 15 is connected to the intake passage 5 downstream of the intake throttle valve 10. A blocking wall 1 having a large diameter hole 16 and a small diameter hole 17 is located in the middle of the EGR passage 14.
8 are provided, and first and second exhaust recirculation valves 19 and 20 open and close both holes 16 and 17 of the closing wall 18.
(hereinafter referred to as the EGR valve) is installed. Each EGR
The valves 19, 20 have casings 19a, 20a connected to the first chamber 19 by diaphragms 19b, 20b.
The first chambers 19c, 20c are divided into springs 19e, 20c and second chambers 19d, 20d.
20e is compressed and negative pressure control solenoid valves 21 and 22 are interposed in the negative pressure passages 23 and 24.
are connected, and the second of diaphragms 19b and 20b
A valve body 19g that opens and closes the holes 16 and 17 via rods 19f and 20f on the chamber 19d and 20d sides,
20g are connected. The first and second EGR valves 19 and 20, together with the intake throttle valve 10, operate at an engine cooling water temperature of, for example, 60 to 60°C.
Control is performed as follows in the range of 100°C, engine speed of 900 to 3000 rpm, 1st to 4th speeds (for 5th speed cars), and engine load of 6 kg/cm ² or less. () When the engine load is 5 to 6 kg/cm ² ...
The first EGR valve 19 is closed, the second EGR valve 20 is open, and the intake throttle valve 10 is fully open. () When the engine load is 4.5 to 5 Kg/cm ² ...
The first EGR valve 19 is open, the second EGR valve 20 is closed, and the intake throttle valve 10 is fully open. () When the engine load is 0 to 4.5Kg/ ^cm2 ...
With the first EGR valve 19 open and the second EGR valve 20 closed, the opening degree of the intake throttle valve 10 is controlled. () If the engine load is 0Kg/ ^cm2 or less...
The first EGR valve 19 is closed, the second EGR valve 20 is closed, and the intake throttle valve 10 is opened at a constant degree. Reference numerals 25 and 26 indicate an intake pressure sensor and an intake air temperature sensor, respectively, which are arranged in the intake passage 5 downstream of the intake throttle valve 10 to detect intake pressure and intake air temperature; 27, a water temperature sensor which is provided in the engine 1 and which detects the cooling water temperature; A shift switch 28 detects the shift position of a shift lever (not shown). 29 is a control unit that controls the operation of the engine 1, which controls the glow plug 4, the first and second glow plugs.
Air heaters 8, 9, negative pressure control solenoid valve 1
2, 21, 22, intake pressure sensor 25, intake temperature sensor 26, water temperature sensor 27, and shift switch 2
8 are electrically linked. As shown in FIG. 2, this control unit 29 inputs an ignition switch signal and an intake air temperature signal to a preheating control means 101, determines whether or not preheating is in progress, and controls the air heater according to the result. Means 102
and the intake throttle valve control means 103 respectively control the second air heater 9 and the intake throttle valve 10. The control is performed according to a rotation signal, a load signal, and a water temperature signal input to each control means 102 and 103. Further, in the intake air heating control and exhaust gas recirculation control after completion of preheating, the opening degree of the intake throttle valve 10 is controlled by the intake throttle valve control means 103 according to each of the above-mentioned signals. Although not shown, the fuel injection pump is also controlled by the control unit 29, and its contents are as follows. () Engine cooling water temperature 30℃ or less, engine load 0Kg/cm ² or less, engine rotation speed 2000rpm or less,
In addition, when the intake air temperature is below 10°C, the advance angle is controlled according to the engine cooling water temperature, engine speed, and intake air temperature. () Engine cooling water temperature 30~60℃ and 60~100℃
In each range of °C, engine speed 900~3000rpm,
When the intake temperature is 10℃ or higher, 1st to 4th gears (for 5th gear cars), and the engine load is 6kg/ ^cm2 or lower, the advance angle is controlled according to the engine load and engine speed. () In the areas () and () above, the advance angle is controlled according to the engine speed. Next, the control operation of the control unit 29 will be explained with reference to FIGS. 3 to 5. First, in step S1, a water temperature signal is input from the water temperature sensor 27 to the control unit 29, and in step S2, the engine coolant temperature T is set to 60°C and 100°C.
It is determined whether or not it is between the two, and if YES, the process moves to step S3. At step S3, the rotation signal is input to the control unit 29, and the rotation signal is input to the control unit 29.
In S4, it is determined whether the engine speed N is between 900rpm and 3000rpm, and if YES, the step
Migrate to S5. Shift switch 2 at step S5
A shift switch signal is input from 8, and the step
In S6, it is determined whether the shift lever is in the 1st to 4th gears, and if YES, the process moves to step S7.
The load signal is input in step S7, and the load signal is input in step S8.
It is determined whether the engine load Pe is within the range of 0 to 6 kg/cm ² or not. If YES, the process moves to step S9, and thereafter, exhaust gas recirculation control is performed in steps S9 to S13. On the other hand, if NO in steps S2, S4, S6, or S8, the step is not in the exhaust recirculation control region.
In S14 to S18, it is determined whether or not the intake air heating region is reached. That is, in step S14, it is determined whether the engine coolant temperature T is within the range of 30 to 60°C,
If YES, the process moves to step S15. In step S15, a rotation signal is input, and in step S16, it is determined whether the engine rotation speed is 2000 rpm or less, and if YES, the process moves to step S17. In step S17, a load signal (for example, an accelerator opening signal) is input, and in step S18, it is determined whether the engine load Pe is 1 Kg/cm ² or less, and if YES, it is determined that the engine is in the intake air heating region. Then, intake air heating control is performed in steps S19 to S22. Incidentally, in the case of NO in steps S14, S16, and S18, the process returns to step S1. In the exhaust gas recirculation control, the first and second EGR valves 19 and 20 are selectively operated in step S9, a rotation signal is input in step S10, and a load signal is input in step S11. Thereby, the step
At S12, map 1 shown in Fig. 3 is displayed depending on the engine speed and engine load (accelerator opening).
Read the map value from (exhaust recirculation control map),
Depending on the value, the first chamber 11 of the diaphragm device 11
The opening degree of the intake throttle valve 10 is controlled by controlling the negative pressure supplied to the intake throttle valve 10 (step S13). In addition, the intake air heating control turns on the second air heater 9 in step S19.
Then, in step S20, a rotation signal is input, and the fourth engine rotation speed is determined based on the engine rotation speed corresponding to the rotation signal.
Map 2 (intake (intake air heating control map) shown in the figure)
This is done by reading the map value (step S21), and controlling the negative pressure supplied to the first chamber 11c of the diaphragm device 11 according to the value to control the opening degree of the intake throttle valve 10 (step S22). . Furthermore, Figs. 3 and 4 show the magnitude of negative pressure in relation to the relationship between engine speed and accelerator opening. Based on Fig. 3, the higher the engine speed, the more the accelerator opening The smaller the degree, the more negative pressure (the first chamber 11 of the diaphragm device 11
The negative pressure inside the exhaust valve 10c is controlled to increase, thereby increasing the opening degree of the intake throttle valve 10. Furthermore, based on FIG. 4, the negative pressure is controlled to increase as the engine speed increases, and the opening of the intake throttle valve 10 also increases, regardless of the accelerator opening. Next, the exhaust gas recirculation region (hereinafter referred to as the EGR region),
A case will be described in which the intake air heating region (hereinafter referred to as the heater operation region) is set as shown in the following table and the two regions overlap.

【table】

[Table] In the simplified flowchart shown in FIG. 6, in step S31, operating signals such as the ignition switch signal, intake temperature signal, rotation signal, load signal, water temperature signal, and 5th speed switch signal are input, In step S32, it is determined whether or not the EGR region is reached. If YES, in step S33, the first or second EGR valve 19,
20 is selectively turned ON, and in step S34, a map value is read from map 1 in FIG. . On the other hand, if NO in step S32, the step
Proceeding to step S36, it is determined whether or not the heater is in the operating range, and if YES, the process proceeds to step S37.
If NO, the process returns to step S31. Step S37
Then, the second air heater 9 is turned on, and in step S38, the map value is read from map 2 in Fig. 4, that is, the intake air heating control map, and the steps are performed according to the value.
Perform intake throttle valve control in S39, then step
Return to S31. In addition, when the exhaust recirculation region and the intake air heating region overlap, priority is given to exhaust recirculation control because _NO It is from. (Effects of the Invention) Since the present invention is configured as described above, the intake throttle valve and its control device can be used in common for intake air heating control and exhaust gas recirculation control, and the structure is simplified, and the intake air heating control can be performed in accordance with requests. Or exhaust recirculation control can be performed, so particulate, _NO
can be efficiently reduced. During engine operation, in the operating range where the engine temperature is below a predetermined value, the engine speed is below a predetermined rotation speed, and the engine load is below a predetermined load, the electric heater is activated because the engine heat output is low and the combustion temperature is low. Map control of the air throttle valve improves combustibility and reduces HC emissions. At that time, the intake throttle valve is controlled to open and close based on a control map that increases the opening degree of the intake throttle valve as the engine speed increases, so that the engine speed changes approximately to the amount of intake air per unit time. Since the ratio is proportional, the intake air heating efficiency can be increased.

[Brief explanation of drawings]

The drawings illustrate embodiments of the invention.
The figure is a schematic diagram of the exhaust purification system for a diesel engine, Figure 2 is the overall diagram of the same, Figures 3 and 4 are
The figures show maps for exhaust gas recirculation control and intake air heating control, respectively. Fig. 5 is a flowchart showing the processing flow of the control unit. Fig. 6 is a flowchart showing a modified example of the processing flow of the control unit. . 1... Diesel engine, 3... Combustion chamber, 4
...Glow plug, 5...Intake passage, 9...Second
Air heater (electric heater), 29...control unit, 103...intake throttle valve control means.

Claims (1)

[Claims] 1. Temperature detection means for detecting engine temperature, rotation speed detection means for detecting engine speed, load detection means for detecting engine load, electric heater for heating intake air disposed in an intake passage, and an exhaust gas recirculation passage connecting the passage and the exhaust passage, an intake throttle valve disposed at the downstream end opening of the exhaust gas recirculation passage and upstream of the electric heater, the temperature detection means, the rotation speed detection means, and the load detection means. In response to the output of the means, the electric heater is actuated to at least increase the engine speed in an operating range where the engine temperature is below a predetermined value, the engine speed is below a predetermined speed, and the engine load is below a predetermined load while the engine is running. and an intake throttle valve control means for controlling the opening and closing of the intake throttle valve based on a control map that increases the opening degree of the intake throttle valve, and the intake throttle valve control means is different between when the intake air is heated and when the exhaust gas is recirculated. A diesel engine exhaust purification device characterized by using a control map.