JPS6371546A - Controller for engine - Google Patents

Abstract

PURPOSE:To rapidly secure the aimed exhaust purifying function by correcting the engine control quantity in the direction for raising the exhaust temperature, when the fuel composition is that having a small calorific heat, thus accelerating the warming of an exhaust purifier. CONSTITUTION:An engine 1 uses LPG as fuel. A controller 24 sets the ignition timing to the retardation side so as to accelerate the temperature rise of a catalytic device 20 when the temperature of the catalytic device 20 on the basis of the output of a temperature sensor 22 is less than a catalysis activation temperature. When the internal pressure of an LPG cylinder 16 on the basis of the output of a pressure sensor 21 is over a prescribed value, it is judged that the rate of the propane having a small calorific heat is high and the exhaust temperature is low, and the ignition timing is adjusted to a set value on the retardation side. Therefore, the warming of the catalytic device 20 can be accelerated in a short time even with the composition having a low calorific heat.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention aims to promote the FIIm of an engine exhaust system and ensure the desired exhaust purification performance at an early stage. This invention relates to an improvement in an engine control device that appropriately adjusts and controls engine ignition timing, etc.

(Prior Art) Conventionally, as a control device for this type of engine, a catalyst device is provided as an exhaust purification device in the middle of the exhaust system, as disclosed in Japanese Patent Application Laid-open No. 51-77727, and the catalyst device When the temperature of the engine is low, its exhaust purification performance decreases, so the ignition timing of the air-fuel mixture supplied to the engine is controlled to a predetermined value on the retard side depending on the exhaust temperature and engine load to increase the exhaust temperature. A device is known in which the warm-up of the exhaust gas purification device is promoted to ensure the desired exhaust gas purification performance at an early stage.

(Problems to be Solved by the Invention) In addition to gasoline, the types of fuel supplied to the engine include, for example, those using LPG as disclosed in Japanese Utility Model Application Publication No. 56-152855, and alcohol. There are engines that use mixed gasoline, and if an exhaust purification device is installed on an engine that uses these as fuel, the ignition timing of the mixture is controlled to the retard side when the temperature is low. It is preferable to accelerate the machine.

However, in fuels such as LPG, the ratio (composition) of each component in the fuel is not constant during the refining process, and the calorific value of each component during combustion is different. In a device that retards the ignition timing of the air-fuel mixture to a predetermined value when the exhaust gas purification device is at a low temperature, if the ratio of the composition with a high calorific value increases, the exhaust temperature will be high and the exhaust gas purification device will have to warm up. Although it can be terminated early, if the proportion of the composition with a low calorific value increases, the exhaust gas temperature will be low and the warming up speed of the exhaust purification device will be slow, making it difficult to achieve the desired exhaust purification performance. The present invention, which has the disadvantage that it cannot be secured early, was made in view of this point, and its purpose is to detect the composition of the fuel supplied to the engine and to ignite the air-fuel mixture according to changes in the composition. By appropriately controlling engine control variables such as timing, the purpose is to promote warm-up of the exhaust purification device in a short time even when the composition has a low calorific value, and to ensure the desired exhaust purification performance at an early stage.

(Means for Solving the Problems) In order to achieve the above object, the configuration of the present invention is based on an engine equipped with an exhaust purification device W 20 in the exhaust system, as shown in FIG. A composition detection means 23 for detecting the composition of the fuel supplied to the engine and a temperature detection means 22 for detecting the temperature of the exhaust purification device 20 are provided, and the outputs of both the detection means 22 and 23 are received. A correction means 25 is provided for correcting controlled variables such as the ignition timing of the engine so as to increase the exhaust temperature when the exhaust purification device 20 is in an engine operating state with low humidity when the fuel composition has a low calorific value. It is.

(Function) With the above configuration, in the present invention, in an engine operating state where the humidity of the exhaust purification device 2o is low, such as immediately after the engine is started, the ignition timing of the engine is controlled to the retard side, and the exhaust temperature increases. Therefore, warm-up of the exhaust gas purification device 20 is promoted, and the desired exhaust gas purification performance is ensured at an early stage.

At this time, when the fuel composition has a low calorific value, the ignition timing of the engine is corrected by the correcting means 25 to the retard side so as to further increase the exhaust humidity, so that the warm-up speed of the exhaust purification device 20 is adjusted to a value smaller than the calorific value. The result is almost the same as when the fuel composition is high, and the desired exhaust purification performance can be secured at an early stage.

(Embodiments) Hereinafter, embodiments of the present invention will be explained based on the drawings from FIG. 2. FIG. 2 shows an embodiment in which the present invention is applied to an engine using LPG as fuel. In the figure, 1 is an engine, 2 is a combustion chamber whose volume is variable by a piston 4 that is slidably inserted into a cylinder 3 of the engine 1, and 5 is a combustion chamber that is variable in volume.
7 has one end communicating with the atmosphere via the air cleaner 6 and the other end opening into the combustion chamber 2 to supply intake air to the engine 1; 7 has one end opening into the combustion chamber 2 and the other end. is an exhaust passage that is open to the atmosphere and discharges exhaust gas, and an LPG mixer 8 that vaporizes LPG and supplies it to the intake passage 5 is disposed in the middle of the intake passage 5. An intake valve 1 is provided at the opening of the passage 5 to the combustion chamber 2.
0, and an exhaust valve 11 is disposed at the opening of the exhaust passage 7 to the combustion chamber 2. Furthermore, an ignition plug 12 is disposed at the top of the combustion chamber 2 to ignite the air-fuel mixture within the combustion chamber 2, and an igniter 13 is connected to the ignition plug 12 to adjust its ignition timing.

The LPG mixer 8 is connected via an LPG supply passage 15 to an LPG cylinder 16 that liquefies and stores LPG under high pressure. Preheater 1 to preheat
7 and a paper riser 18 that vaporizes the liquefied LPG and reduces the pressure to a predetermined pressure on the downstream side of the pre-heater 17, and a paper riser 18 that vaporizes the liquefied LPG in the LPG cylinder 16 and reduces the pressure to a predetermined pressure.
The air is supplied from the G mixer 8 to the intake passage 5.

Here, the composition of LPG in the LPG cylinder 16 consists of butane and propane as main components, and the ratio thereof varies within a predetermined range during the LPG refining process,
Furthermore, butane has a property of generating a large amount of heat when burned, while propane has a property of generating a small amount of heat.

In addition, a catalyst device 20 as an exhaust purification device that reduces Co, HC, and NOx in the exhaust gas using a platinum-rhodium three-way catalyst or the like is interposed in the middle of the exhaust passage 7 that constitutes the exhaust system. The catalyst device 20 has a characteristic that it exhibits the desired exhaust gas purification performance when the temperature of the catalyst is higher than the relatively high activation temperature.

A pressure sensor 21 for detecting the pressure of liquefied LPG is disposed immediately downstream of the LPG cylinder 16 in the LPG supply passage 15, and a pressure sensor 21 for detecting the pressure of the liquefied LPG is disposed in the catalyst device 20. A temperature centimeter 22 is provided as temperature detection means. Above pressure sensor 2
As shown in FIG.
The pressure sensor detects the proportion of propane in LPG by utilizing the characteristic that the internal pressure P of the LPG cylinder 16 increases as the proportion of propane in the LPG in the PG cylinder 16 increases. LPG cylinder 1 by 21
By detecting the internal pressure of 6, the ratio of butane to propane in LPG is ascertained, and the composition detecting means 23 is configured to detect the composition of LPG to be supplied to the engine 1. The outputs of the pressure sensor 21 and the temperature sensor 22 are input to a controller 24 that includes a CPU, RAM, etc., and the controller 24 controls the ignition timing of the spark plug 12.

Next, the ignition timing control of the spark plug 12 by the controller 24 will be explained based on the flowchart of FIG. 4. First, the engine starts by starting the engine 1, and in step S1, the internal pressure P of the LPG cylinder 16 is determined based on the output from the pressure sensor 21, and this cylinder internal pressure P is determined in a situation where the temperature rise of the catalyst device 20 starts to be significantly delayed. When P<Po is No, it is determined that the ratio of butane, which has a large calorific value, is high and the temperature of the catalyst device 20 is quickly raised. ,
In step S2, the temperature T of the catalyst device 20 is determined based on the output of the temperature sensor 22, and this catalyst temperature T is compared in magnitude with the activation temperature TO of the catalyst. It is determined that there is no need to control the acceleration of the temperature rise of the catalyst device 20, and in step S3, the ignition timing of the spark plug 12 is adjusted to a predetermined value on the retard side for a predetermined period of time after engine startup in order to correspond to idling operation. On the other hand, if the activation temperature is lower than No (T<To), the ignition timing of the spark plug 12 is changed to the retard side where the exhaust temperature becomes higher in step S4 in order to perform control to accelerate the temperature rise of the catalyst device 20. The adjustment is made to the set value A and the process ends. On the other hand, if the internal pressure P of the LPG cylinder 16 is higher than the predetermined value Po (P≧Po) (YES in step S1), the proportion of propane with a small calorific value is high and the exhaust temperature is low. After determining that the temperature is low, in step S5, the temperature T of the catalyst device 20 is compared in magnitude with the activation temperature To, and if YES is determined when T≧TO activation temperature or higher and temperature rise control is not necessary. In this case, the process returns to step S3 and normal control of the ignition timing is performed, while in the case of No, where T<To is less than the activation temperature, the ignition timing is controlled in step S6 in order to perform control to accelerate the temperature rise of the catalyst device 20. The adjustment is made to the set value B (B>A) on the retard side, which is further higher than the set value A on the retard side, and ends.

Therefore, in the operation flow shown in FIG. 4 above, step 8
185.86, pressure sensor 21 and temperature sensor 2
2, when the proportion of propane is high, that is, when the fuel composition has a low calorific value, the spark plug 12 is controlled as an engine control amount so as to increase the exhaust temperature in the engine operating state where the temperature of the catalyst device 20 is low. A correction means 25 is configured to adjust and correct the ignition timing to a set value B that is further on the retard side than when the fuel composition has a large calorific value (when the ratio of butane is high).

Therefore, in the above embodiment, when the temperature T of the catalyst device 20 detected by the temperature sensor 22 is lower than the activation temperature To, the ignition timing of the ignition plug 12 is adjusted to the retard side, and the exhaust temperature increases. Therefore, the temperature rise of the catalyst device 20 is promoted, and the catalyst temperature quickly reaches the activation temperature 1.
0 or more, and the desired exhaust gas purification performance can be secured at an early stage.

At that time, if the internal pressure P of the LPG cylinder 16 is not at the predetermined value PO, the ratio of butane in the LPG is higher than the normal ratio, and the exhaust temperature is sufficiently high, so the ignition timing is set to the retard side. When the temperature T of the catalyst device 20 is adjusted to the set value A, as shown by the solid line in FIG. will be done.

Further, the internal pressure P of the LPG cylinder 16 is a predetermined value P.

In the above case, although the ratio of propane in LPG is higher than the normal ratio and the calorific value of the fuel itself is small, in this case, the ignition timing of the spark plug 12 is retarded by the correction means 25. Since the setting value A on the side is further adjusted to the setting value B on the retard side, the exhaust flow rate becomes almost the same temperature as when the cylinder internal pressure is low, and the temperature T of the catalyst device 2° is at a point in the figure. As shown by the dashed line, it rises quickly, almost in the same way as when the proportion of butane is large. As a result, compared to the conventional case in which the ignition timing retard is always adjusted to the set value A (A<B) when the butane ratio is large, the temperature rise of the catalyst device 20 is lower than that in the conventional case shown by the broken line in the figure. It becomes more noticeable than in the case of temperature rise,
The desired exhaust purification performance can be demonstrated at an early stage.

In the above embodiment, the ignition timing of the air-fuel mixture is used as the engine control variable, and when the propane ratio is high, the ignition timing is adjusted further to the retard side than usual to further increase the exhaust temperature. Alternatively, the idle speed may be used as the engine control amount, and when the propane ratio is high, the idle speed may be further increased to increase the amount of exhaust gas, thereby promoting warm-up of the catalyst device 20. Furthermore, it goes without saying that the temperature of the catalyst device 20 may be detected indirectly using the temperature of the engine 1.

Further, in the above embodiment, the present invention is applied to an engine using LPG as fuel, but it goes without saying that the present invention can be similarly applied to an engine using alcohol-mixed gasoline.

(Effects of the Invention) As explained above, according to the present invention, when the exhaust purification device provided in the exhaust system is at a low temperature and the composition of the fuel supplied to the engine has a low calorific value, the exhaust temperature increases more. Since engine controls such as ignition timing have been corrected in the direction of ignition timing, the exhaust purification device can be warmed up effectively in a short time regardless of changes in fuel composition, and the desired exhaust purification performance can be achieved quickly. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 5 show embodiments of the present invention, FIG. 2 is an overall configuration diagram when applied to an LPG engine, FIG. 3 is a diagram showing LPG cylinder internal pressure characteristics with respect to propane ratio in LPG, and FIG. FIG. 4 is a flowchart showing the operation of the controller, and FIG. 5 is an explanatory diagram of the operation. 1...Engine, 8...LPG mixer, 12...
Spark plug, 16... LPG cylinder, 20... Catalyst device, 21... Pressure sensor, 22 Temperature sensor, 23...
... composition detection means, 24 ... controller, 25 correction means.

Claims (1)

[Claims] (1) In an engine equipped with an exhaust purification device in the exhaust system, a composition detection means for detecting the composition of fuel supplied to the engine, a temperature detection means for detecting the temperature of the exhaust purification device, and a combination of both detection means. The present invention is characterized by comprising a correction means that receives the output and corrects the control amount of the engine so as to increase the exhaust temperature when the exhaust purification device is in an engine operating state where the temperature of the exhaust purification device is low when the fuel composition is low in calorific value. Engine control device.