JPS60153473A - Exhaust purifier for engine - Google Patents

Abstract

PURPOSE:To minimize deterioration of exhaust purification performance due to aging of catalyst by increasing the catalyst temperature promoted through lag angle control in accordance to aging of catalyst. CONSTITUTION:A control unit 20 comprised of a microcomputer will read the accumulated travel distance through an accumulated travel meter 26 when the opening of throttle valve 16 is lower than 80 deg., and if it is within predetermined range corresponding with that when the catalyst has aged considerably, the specified catalyst temperature is increased with the increase of accumulated travel distance to maintain constant at the level higher than predetermined level. When the temperature of catalyst 19 detected through a sensor 28 is below said specified level, additional lag angle time is calculated to correct the basic injection timing to be determined by the engine rotation and load to the lag angle side and to repeat said operation. Consequently, catalyst warming can be promoted effectively to minimize deterioration of exhaust purification performance of catalyst.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention purifies exhaust gas from an automobile engine by passing it through a catalytic converter to reduce harmful components contained therein. This invention relates to an engine exhaust purification device.

(Prior art) The exhaust gas of a gasoline engine is -carbon oxide <co>
, hydrocarbons (HC), nitrogen oxides (N.

In order to reduce as much as possible the harmful components in the exhaust gas emitted into the atmosphere, in cars equipped with gasoline engines, the intake air of the engine must be Various efforts have been made to purify exhaust gas, including improvements to various parts of the fuel supply system, fuel supply system, ignition system, exhaust system, etc.

To purify such exhaust gas, a purification measure that installs a catalytic converter in the exhaust system is widely used. A catalytic converter consists of a container containing a catalyst obtained by granulating or plate-forming various metals and metal oxides such as platinum, vanadium, and manganese, and exhaust gas passes through this catalyst. As a result, harmful components in exhaust gas are reduced.

In exhaust gas purification using a catalytic converter, in order for the catalyst to exert a purifying effect on exhaust gas, the temperature of the catalyst is required to be equal to or higher than a predetermined value.

For this reason, for example, after starting the engine from a sufficiently cooled state, the temperature of the catalyst in the catalytic converter is quickly raised to a predetermined value or higher in order to shorten the time during which exhaust gas purification by the catalytic converter is not performed properly. In other words, it is necessary to accelerate catalyst warm-up. The temperature of the catalyst is normally raised by the heat of exhaust gas from the engine, but increasing the temperature of the exhaust gas has been considered for the purpose of promoting warm-up of the catalyst. For example,
Publication No. 18771 states that during a specific period during the engine warm-up process, advance control of the engine's ignition timing is temporarily stopped to promote catalyst warm-up. It is described that the advance control of the ignition timing is performed based on the temperature of the exhaust gas or the temperature of the catalyst.

Generally, when the engine's ignition timing is delayed, the temperature of the exhaust gas rises to -, but as mentioned above,
In the case of the description in the publication, the catalyst warm-up is promoted by increasing the temperature of the engine by temporarily stopping advance control of the ignition timing of the engine.

In this way, after the engine starts, the temperature of the catalyst in the catalytic converter can be quickly brought to a predetermined value or higher, and a state can be established in which exhaust gas purification by the catalytic converter can be performed normally. As the catalyst is used, its characteristics gradually deteriorate over time, and as the catalyst deteriorates over time, it becomes inconvenient for exhaust gas purification by the catalytic converter. This deterioration of the catalyst over time manifests itself in a decline in its exhaust purification performance,
For example, as shown in Fig. 1, in a characteristic diagram in which the horizontal axis shows the catalyst temperature C and the vertical axis shows the sliding 4-gas purification rate k, in the case of a new catalyst, the solid line a As shown in Figure 2, the exhaust gas purification rate k takes a constant value that increases rapidly as the temperature rises, whereas in the case of a catalyst that has deteriorated over time, it is 1, and as shown by the broken line, the The increase in exhaust purification rate due to increase in catalyst temperature is slower than that with new catalysts, and
The new catalyst does not reach the fixed exhaust gas purification rate after rising, but stops at a lower exhaust purification rate.

Therefore, in the case of a catalyst that has deteriorated over time, it is necessary to use a new catalyst to sufficiently promote the exhaust purification effect and to quickly achieve a state in which the catalytic converter can purify the exhaust gas and properly purify the exhaust gas. This brings with it the inconvenience of not being able to do it anymore.

(Object of the Invention) In view of the above, the present invention purifies engine exhaust gas by passing it through a catalytic converter.
The warm-up of the catalyst in the catalytic converter is promoted by increasing the exhaust gas temperature by performing retard control that retards the engine ignition timing from the normal timing. An engine exhaust purification device that effectively promotes catalyst warm-up even if the catalyst deteriorates over time, and allows the catalytic converter to properly purify the exhaust at a relatively early stage. The purpose is to provide

(Structure of the Invention) An engine exhaust purification device according to the present invention includes a catalyst disposed in an exhaust passage for passing engine exhaust gas;
A temperature detecting means for detecting the temperature of the catalyst, a total operating time detecting means for detecting the total operating time of the engine, and delaying the ignition timing of the engine when the catalyst temperature detected by the temperature detecting means is below a predetermined temperature value. ignition timing control means that performs ignition timing control on the side, and temperature value correction means that increases the above-mentioned predetermined temperature value as the total operating time detected by the total operating time detection means increases at least within a predetermined range. Prepared and configured.

With this configuration, the retard control that delays the engine's ignition timing for the purpose of promoting catalyst warm-up of the catalytic converter corresponds to the total operating time of the engine. This is done to obtain a catalyst temperature that corresponds to the degree of deterioration of the catalyst over time, and therefore, the catalyst temperature, which is promoted to increase by retard control, is increased in accordance with the progress of deterioration of the catalyst over time. Therefore, even if the catalyst deteriorates over time, a state in which the catalytic converter can appropriately purify the exhaust gas can be achieved relatively quickly.

(Example) Hereinafter, an example of the present invention will be described with reference to FIG. 2 and subsequent figures of the drawings.

FIG. 2 shows an example of the engine exhaust purification device according to the present invention, together with a portion of the engine to which the device is applied.

Here, the engine body 1 includes a cylinder block 3 having a part of a cylinder containing a piston 2, and a cylinder head 6 disposed on the cylinder block 3 to which an intake valve 4 and an exhaust valve 5 are attached. A combustion chamber 7 is formed surrounded by a part of the cylinder of the cylinder block 3, a piston head part of the piston 2 therein, and four parts in the cylinder head 6 corresponding thereto. . A spark plug 8 is mounted on the cylinder head 6 with its gap portion facing the combustion chamber 7, and an intake boat 9 and an exhaust boat 10 communicating with the combustion chamber 7 are formed. The intake manifold 11 is connected to the intake boat 9, and
An exhaust manifold 12 is connected to the exhaust port 10.

Inside the intake boat 9 and intake manifold 11, there is an arrow A.
As shown, an intake passage 131 is formed for supplying intake air drawn through an air cleaner (not shown) to the combustion chamber 7 via the intake valve 4.

In this intake passage 13i, an air flow sensor 4 for detecting the intake air flow rate is arranged with an output part 14a, an intake negative pressure sensor 5 for detecting the engine load is attached, and a throttle valve 16 and a fuel injection A valve 17 is arranged.

Furthermore, an exhaust passage 13e is formed in the exhaust port 10 and the exhaust manifold 12 to exhaust combustion gas from the combustion chamber 7 via the exhaust valve 5.

In an example of the engine exhaust purification device according to the present invention applied to such an engine, a catalytic converter 8 is disposed in an exhaust passage 13e provided to the engine body, and the exhaust gas in the exhaust passage 13e is The gas is led to the catalytic converter 8, communicates with the catalyst 19 therein, and is discharged.
A catalyst temperature sensor 28 is attached to detect the temperature of 9. Further, a control unit 20 for controlling the operations of the spark plug 8 and fuel injection valve 17 described above is installed. Spark plaque 8 is ignition coil 2
The primary current Ci is supplied from the control unit 2o to the primary side of the ignition coil 270.
A high voltage pulse P is generated on the secondary side due to the interruption of this primary current Ci.
i is obtained and this high voltage pulse Pi is supplied to the spark plug 8. Then, depending on the high voltage pulse P i,
A spark flies between the gaps of the spark plugs 8, and the air-fuel mixture in the combustion chamber 7 is ignited. In addition, the fuel injection valve 17
is, for example, an electromagnetic control valve, and the control Uniso i.2
An injection control pulse Q is supplied from 0, and fuel is injected into the intake passage 131 during a period corresponding to the pulse width of the injection control pulse Q.

The control unit 20 receives an air flow rate detection signal Sa from the output section 14a of the air flow sensor 14, which detects the intake air flow rate in the intake passage 13i.

A signal Ss that detects the throttle opening obtained in connection with the throttle valve 16, a load detection signal Sr that detects the engine load from the intake negative pressure sensor 15, and a rotor 24 that rotates in conjunction with the crankshaft 23. from the crank angle reference signal generator 25 installed in connection with the
A crank angle reference pulse pc obtained at a predetermined time before the piston 2 reaches the compression top dead center is supplied, and the cumulative mileage obtained in connection with the cumulative mileage meter 26 of a car equipped with this engine is calculated. A travel distance signal Stm indicating the temperature of the catalyst 19 is also supplied from the catalyst temperature sensor 28, and a rotation speed detection signal Sn indicating the engine rotation speed is also supplied from the input terminal 21. Then, in the control unit 20, an injection control pulse Q is formed based on these various signals, and supply control of the primary current Ci flowing to the primary side of the ignition coil 27 is performed.

In such a configuration, when the engine is started with the entire engine sufficiently cooled and enters the warm-up process, when the engine is started, the catalyst comparator 18 is also in a cooled state and the temperature of the catalyst 19 is low. The temperature is lower than the predetermined temperature required for the catalyst 19 to exert its exhaust gas purifying effect, that is, the operating temperature, and the catalyst in the catalytic converter 18 enters a warm-up process. In this state, the control unit) 2
0 has a predetermined pulse width based on the contents of the air flow rate detection signal Sa, load detection signal Sr, rotation speed detection signal Sn, etc. By controlling the cut-off timing of the primary current Ci supplied to the primary side of the engine 27, retard control is performed to delay the ignition timing to promote catalyst warm-up. This retard control is performed until the temperature of the catalyst 19 of the catalytic converter 18 reaches a predetermined temperature higher than the operating temperature, and the temperature of the catalyst 19 becomes the temperature detection signal Sc. The value of the predetermined temperature is increased as the deterioration of the catalyst 19 progresses over time. Note that the amount of retardation in such retard control is expressed as a retardation time, which is the time from the generation point of the crank angle reference pulse Pc supplied from the crank angle reference signal generator 25 to the control unit 20. In each unit operation process of the engine, the primary current CI supplied to the primary side of the ignition coil 27 is cut off when the crank angle reference pulse Pc is generated 411 retardation time has elapsed, and the ignition timing is adjusted. Retard angle control is performed with the lag side being the lag side.

The deterioration of the catalyst 19 of the catalytic converter 18 over time progresses as the total operating time of the engine increases, so the degree of deterioration of the catalyst 19 over time can be equivalently detected based on the total operating time of the engine. Furthermore, since an increase in the total operating time of an engine is usually accompanied by an increase in the cumulative mileage of a vehicle equipped with the engine, in this example, the total operating time of the engine is supplied to the control unit 20. Detection is performed based on the cumulative travel distance obtained by adding the travel distance signal Stm. Therefore, the value of the above-mentioned predetermined temperature, which regulates the state in which the retard control is performed, which is the third step in promoting catalyst warm-up, is increased by the control unit 20 as the cumulative mileage increases. In addition, increasing the predetermined temperature of the catalyst 19 that regulates the state in which retard control is performed to retard the ignition timing from the normal timing means that the temperature of the catalyst 19 whose rise is promoted by the retard control is increased.
The temperature of the catalyst 19 is increased as the deterioration of the catalyst 19 progresses over time.
Catalyst warm-up is effectively promoted, and exhaust gas purification in the catalytic converter 18 is properly performed within a relatively short time after the engine is started. however,
If the catalyst 19 deteriorates significantly over time, the catalyst 19
The reason why the above-mentioned predetermined temperature value is increased as the cumulative mileage increases is that the catalyst 19 has significantly deteriorated over time. If the cumulative travel distance exceeds a predetermined value of 4, the above-mentioned predetermined temperature value cannot be increased any further.

The control unit 20 that operates as described above, for example,
It is configured using a microcomputer, and in such a case, the central processing unit of the microcomputer <c
An example of a program for retarding the ignition timing of the engine executed by the engine will be described with reference to the flowchart in FIG.

After the start, decision 30 determines whether the throttle opening degree α obtained based on the signal Ss sent in connection with the throttle valve 16 is, for example, greater than 80°, that is, Determine whether the engine is in a high load operating state. If the throttle opening degree α is 80 degrees or less, it is determined that the state is such that retard control should be performed to delay the ignition timing to promote catalyst warm-up as necessary, and the process proceeds to process 31, where the mileage signal is Read the cumulative travel route ML into Stm. Then, in process 32, the accumulated mileage read in process 31 is calculated as follows: For example, as shown in FIG. In the range where the mileage is less than the predetermined value Lx, the value increases from Tel to 'rcz as the cumulative mileage increases, and after that, when the cumulative mileage exceeds the predetermined value Lx, Tc increases. A preset relationship, which is constant at , is compared with a data table in which it is assumed that there is a problem, and a specified catalyst temperature value Tc corresponding to the cumulative mileage at that time is read.

In this case, the predetermined value Lx of the cumulative mileage corresponds to a case where the deterioration of the catalyst 19 over time has progressed significantly.

Here, the specified catalyst temperature value Tc that is read increases as the cumulative mileage increases within a range of a predetermined value Lx or less, that is, as the total operating time of the engine increases below a predetermined value. It will become more expensive.

Next, in process 33, the temperature T of the catalyst 19 is measured using the temperature detection signal Sc, and in the subsequent decision 34,
It is determined whether the temperature T of the catalyst 19 measured in process 33 exceeds the specified pre-six medium temperature value Tc read in process 32. As a result, if the temperature T of the catalyst 19 is equal to or lower than the specified catalyst temperature value Tc, it is determined that retard control is required to retard the ignition timing to promote catalyst warm-up, and the process proceeds to step 35. An additional retard time IGr that takes a positive value for such retard control is calculated.

Next, in process 36, the engine rotation speed Ne obtained based on the rotation speed detection signal Sn and the engine load Le obtained based on the load detection signal Sr are determined, for example, as shown in FIG. The basic retard time IGo, which is determined from the value of the engine speed Ne and the value of the engine load Le, is compared with the hail map, and the engine speed Ne at that time is determined.
and the basic retard time IGo corresponding to the engine load Le. This basic retard time ■Go is supposed to determine the regular ignition timing. Then, in process 37, process 3
The final retard time IC is calculated by adding the additional retard time lGr calculated in step 5.

7 After the final retard time IG is obtained, it is determined in decision 38 whether or not the crank angle reference pulse Pc from the rank angle reference signal generator 25 has arrived, and whether or not the crank angle reference pulse Pc has arrived. If not, wait for its arrival, and when the crank angle reference pulse Pc arrives, the digital controller 3
At step 9, it is determined whether the final retard time rc is 0 or not. If the final retard time IG is not 0, proceed to process 40, reduce the final retard time IG by ΔIG, and return to decision 39.
It is determined whether the final retard time IG is O or not. This loop of proceeding from decision 39 to process 40 and returning to decision 39 again is repeated until decision 39 determines that the final retard time IG is 0. Here, the above ΔIG is calculated from process 40 to decision 39
The time corresponding to the time required for one round of returning to step 40 and proceeding to process 40 again is selected.

When the final retard time TG is determined to be O in decision 39, that is, when the final retard time IG has elapsed after the arrival of the crank angle reference pulse Pc, the process proceeds to process 8 and 41, and in process 41, the ignition is The primary current C1 supplied to the primary side of the coil 27 is cut off,
Go back. By interrupting the primary current C4 to the ignition coil 27, a high voltage pulse Pi is obtained on the secondary side of the ignition coil 27, and this high voltage pulse Pi is supplied to the spark plug 8, and the air-fuel mixture in the combustion chamber 7 is ignited. be done.

In this way, the ignition timing is controlled so that ignition in the combustion chamber 7 is performed when the final retard time IG has elapsed after the generation of the crank angle reference pulse Pc. In this case, the final retard time IG is larger than the basic retard time IGo because the addition retard time IGr takes a positive value, and therefore the ignition timing is greater than the basic retard time IGo.
Therefore, the ignition timing is delayed from the regular timing determined by the ignition timing, and the ignition timing is retarded, thereby increasing the temperature of the exhaust gas.

On the other hand, if the result of decision 30 is that the throttle opening degree α is greater than 80 degrees, that is, the engine is in a high load operating state, and as a result of decision 34, process 33 If the measured temperature T of the catalyst 19 exceeds the specified catalyst temperature value Tc read in process 32, that is, the temperature of the catalyst 19 exceeds the operating temperature of the catalyst 19 at that time in a state of deterioration over time. If this is the case, the process proceeds to process 42 in order to prevent the retardation control that retards the ignition timing.
In process 42, the additional retard time IGr is set to 0. next,
In process 43, a preset upper limit value Tm of the temperature of catalyst 19 is read, and in decision 44, the temperature of catalyst 1 at that time is read out.
9 is lower than the upper limit value Tm of the temperature of the catalyst 19 read in process 43. As a result of the determination in decision 44, if the temperature T of the catalyst 19 is lower than the upper limit value Tm, the process proceeds to process 36, and thereafter proceeds in a two-part flow. In this case, since the acceleration/retardation time IGr is O, the final retardation time IG calculated in process 37 is equal to the basic retardation time IGo, and therefore, the ignition timing is determined by the occurrence of the crank angle reference pulse Pc. This is the regular 0 time when the basic retard time IGo has elapsed. Further, as a result of the determination in decision 44, if the temperature T of the catalyst 19 is equal to or higher than the upper limit value Tm, advance control is performed to advance the ignition timing from the normal timing in order to lower the temperature of the exhaust gas. , in process 45, the additional retard time IGr is assumed to take a negative value, and in process 36
, and the flow continues as described above. In this case, since the addition/retardation time IGr is assumed to take a negative value,
The final retard time IG calculated in process 37 is smaller than the basic retard time IGo, so the ignition timing is earlier than the regular ignition timing determined by the basic retard time IGo, and advance control is performed. It turns out.

In this way, when the temperature 'r of the catalyst 19 is below the specified catalyst temperature value Tc, retard control is performed to delay the ignition timing to promote catalyst warm-up, and this specified catalyst temperature value Since Tc is set higher as the total operating time of the engine increases within a predetermined range, and thus as the aging of the catalyst 19 progresses, the temperature of the catalyst 19, which is promoted to rise by the retardation control, becomes higher than that of the catalyst 119. As deterioration progresses over time, the catalyst temperature is increased, and even if the deterioration of the catalyst 19 progresses over time, warm-up of the catalyst can be effectively promoted to ensure that the catalytic converter 18 can properly purify the exhaust gas. be exposed.

In the above example, the specified catalyst temperature 4fiTC is increased as the cumulative mileage increases because the cumulative mileage increases to a predetermined value Lx that corresponds to a case where the deterioration over time of the catalyst 19 has significantly progressed. Although the following restrictions apply, this restriction is not always necessary.

(Effects of the Invention) As is clear from the above description, according to the engine exhaust purification device according to the present invention, retard control is performed to delay the ignition timing of the engine for the purpose of catalyst warm-up from the normal timing. The predetermined value for the catalyst temperature that regulates the state in which this occurs is increased as the catalyst deteriorates over time;
Since the catalyst temperature, which is promoted to rise by the retard control, increases as the catalyst deteriorates over time, catalyst warm-up can be effectively promoted even if the catalyst deteriorates over time. Therefore, it is possible to minimize the deterioration of the exhaust gas purification performance of the catalyst, and for example, the catalytic converter can perform appropriate exhaust gas purification within a short time after the engine is started. Furthermore, since retard control that delays the engine's ignition timing from the normal timing is not performed unnecessarily, deterioration in fuel efficiency can be minimized.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram used to explain the deterioration of the catalyst over time;
The figure is a schematic configuration diagram showing an example of the engine exhaust purification device according to the present invention together with a part of the engine to which the device is applied, and FIG. 3 is an operating program of a microcomputer in an example of the control unit used in the example of FIG. FIGS. 4 and 5 are characteristic diagrams for explaining the operation according to the flowchart in FIG. 3. In the figure, 1 is the engine body, 7 is the combustion chamber, and 8 is the spark
Plug, 13e is exhaust passage, 18 is catalyst 3 Patent applicant: Toyo Kogyo Co., Ltd. 4

Claims (1)

[Claims] a catalyst interposed in an exhaust passage to allow engine exhaust gas to pass through; a temperature detection means for detecting the temperature of the catalyst;
Total operating time detection means for detecting the total operating time of the engine; and ignition control for retarding the ignition timing of the engine when the catalyst temperature detected by the temperature detection means is below a predetermined temperature value. An engine exhaust gas comprising: a timing control means; and a temperature value correction means for increasing the predetermined temperature value as the total operating time detected by the total operating time detecting means increases at least within a predetermined range. Purification device.