JP2002293172A - Control system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular control system that clears severer emission regulation and permits an operation with appreciable fuel economy. SOLUTION: The control system for a vehicle where an output side of an internal combustion engine with a controllable engine load is connected with a continuously variable transmission capable of controlling output speed of the internal combustion engine comprises an exhaust purifying means disposed in an exhaust system for the internal combustion engine to purify exhaust and consume fuel for the exhaust purification, an optimal operating point computing means for computing as an optimal operating point an operating point with a minimal total fuel consumption where a fuel quantity consumed by the exhaust purifying catalyst is added to a fuel quantity consumed by the internal combustion engine for requested output, and an operation controlling means for controlling the engine load of the internal combustion engine and controlling the transmission ratio of the continuously variable transmission so that the operating state of the internal combustion engine becomes an operating state at the optimal operating point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a vehicle having a drive mechanism in which a continuously variable transmission is connected to the output side of an internal combustion engine such as a diesel engine. The present invention relates to a control device for controlling the output of an internal combustion engine so as to reduce the amount of pollutants.

[0002]

2. Description of the Related Art Internal combustion engines, such as diesel engines,
Since power is output by burning fuel, exhaust gas is inevitably generated. From the viewpoint of preserving the global environment, it is required to purify exhaust gas generated from an internal combustion engine as much as possible. An example of a pollutant contained in the exhaust gas of an internal combustion engine is nitrogen oxide (NOx), and it is required to reduce the emission.

[0003] NOx is easily generated when the combustion condition of the fuel is relatively high temperature and in an oxidizing atmosphere. Therefore, the ratio of the air and the fuel of the air-fuel mixture of the air-fuel mixture burned in the internal combustion engine, that is, the air-fuel ratio is determined by the stoichiometric air-fuel ratio (14). .5) is likely to occur when the value is larger than the theoretical air-fuel ratio (16 to 17). Therefore, in order to reduce the amount of NOx emission, the air-fuel ratio may be made smaller or larger than this value. However, when the air-fuel ratio is lowered, the fuel supply amount increases, and the fuel efficiency deteriorates. In addition, if it is increased, the combustion becomes unstable depending on the degree, and the fuel efficiency deteriorates. As described above, the fuel efficiency characteristic and the NOx emission characteristic are in a contradictory relationship, and when one characteristic is improved, the other characteristic is deteriorated.

Conventionally, attention has been paid to the fact that by connecting a continuously variable transmission to the output side of an internal combustion engine, the rotational speed of the internal combustion engine can be controlled arbitrarily to some extent, and attempts have been made to achieve both fuel economy characteristics and NOx emission characteristics. Have been. One example is described in JP-A-4-255541. The apparatus described in this publication obtains the fuel consumption characteristics and NOx emission characteristics for each of an operating state where the air-fuel ratio is stoichiometric or richer and a lean operating state where the air-fuel ratio is larger than the stoichiometric air-fuel ratio. In addition, the fuel consumption characteristic and the NOx emission characteristic are evaluated for the driving state in which the output based on the driving state and the required driving amount is obtained, and the driving state in which these two characteristics are compatible is selected.

[0005]

According to the control device described in the above-mentioned publication, either the lean operation or the stoichiometric air-fuel ratio operation (stoichiometric operation) is performed on the equal output line corresponding to the actual output. It is possible to evaluate whether or not the consumption rate and the NOx emission rate are more compatible with each other, and select an operation state with a good evaluation. However, such a configuration provides a basis for selecting either the lean operation or the stoichiometric operation on the equal output line, but does not determine the optimal operation state. That is, when the fuel consumption rate and the emission amount of nitrogen oxide have characteristics that change with respect to the engine speed and the engine torque, the optimum operating point that minimizes both the fuel consumption rate and the emission amount of nitrogen oxide is determined. It cannot meet practical requirements.

[0006] Recently, emission control of environmental pollutants such as NOx has tended to become more and more strict, and as described in the above-mentioned publications, changing the operating state or the combustion state requires the following. It is becoming more difficult to meet the latest emission regulations. In order to meet such strict NOx emission regulations, the fuel consumption characteristics and N
Attempts have been made to control the operating state of the vehicle so as to achieve both Ox emission characteristics and to purify the exhaust of the internal combustion engine using a catalyst.

[0007] As the catalyst, a NOx storage reduction type catalyst is known. This catalyst is, for example, a type of NO in exhaust gas generated when the internal combustion engine is operated in a lean state having a large air-fuel ratio.
x is absorbed as nitrate nitrogen, and with the amount of absorption increased to a predetermined amount, the reaction atmosphere with the catalyst is changed to a reducing atmosphere, thereby reducing the stored nitrate nitrogen to form nitrogen gas. Release. Further, in this case, since nascent oxygen (active oxygen) is generated, soot attached to the catalyst can be oxidized.

When this type of catalyst is used, it is necessary to temporarily change the atmosphere to a reducing atmosphere when the amount of stored NOx has increased to some extent. As a method of controlling the reducing atmosphere, there are known a method of supplying a reducing agent such as fuel or ammonia into exhaust gas and a method of increasing an amount of fuel supplied to an internal combustion engine to lower an air-fuel ratio. Fuel is usually used as a reducing agent because it is undesirable for ammonia to be emitted from the vehicle. Therefore, when the NOx storage reduction catalyst described above is used, fuel is consumed to reduce and release the stored NOx.

As described above, when the NOx storage-reduction catalyst is used, the fuel burned in the internal combustion engine and the fuel for purifying NOx are consumed. Conventionally, only the former fuel consumption is used. However, since only control taking into account the above is performed, there is room for further improvement in terms of improving fuel efficiency. Further, the apparatus described in the above publication gives a basis for selecting either lean operation or stoichiometric operation on an equal output line, but is consumed to remove pollutants in exhaust gas such as NOx. Since the optimum operation state is not determined in consideration of the amount of fuel, the use of the above-described NOx storage reduction catalyst may not always provide the optimum fuel efficiency.

The present invention has been made in view of the above technical problems, and has as its object to provide a control device capable of reducing the amount of pollutants in exhaust gas without deteriorating fuel efficiency. It is assumed that.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of summing an amount of fuel consumed for running a vehicle and an amount of fuel consumed for purifying exhaust gas. A control device characterized in that the internal combustion engine is configured to operate at an operating point at which the so-called combined fuel consumption and the amount of pollutants in the exhaust are minimized. . Another feature of the present invention resides in that the internal combustion engine is operated at an operating point where both the fuel consumption and the amount of pollutants generated in the internal combustion engine are minimized on the equal output line of the internal combustion engine. .

More specifically, the invention of claim 1 controls a vehicle in which a continuously variable transmission capable of controlling the output rotation speed of the internal combustion engine is connected to the output side of the internal combustion engine capable of controlling the engine load. An exhaust purification device disposed in an exhaust system of the internal combustion engine for purifying exhaust gas and consuming fuel for purification of the exhaust gas; and a fuel consumed by the internal combustion engine for performing required output. Optimum operating point calculating means for obtaining, as an optimum operating point, an operating point at which the total fuel consumption obtained by adding the amount of fuel consumed by the exhaust gas purification catalyst to the amount is the optimum operating point; and A control device comprising: an operation control unit that controls an engine load of the internal combustion engine so as to be in an operation state and controls a speed ratio of the continuously variable transmission.

Therefore, according to the first aspect of the present invention, the fuel is burned by driving the internal combustion engine, and the fuel is consumed when the exhaust gas is purified by the exhaust gas purifying means. The total fuel consumption is the sum of the fuel consumption, which is the sum of the combustion in these internal combustion engines and the consumption in the exhaust gas purification means, and the total fuel consumption associated with performing the required output is the minimum. An operating point is required. For example, the fuel consumption when the internal combustion engine is operated for a predetermined time at a predetermined output and the fuel required to reduce a predetermined pollutant in exhaust gas discharged during the predetermined time to a regulation value. An operating point at which the total fuel consumption obtained by adding the consumption amount to the required output is minimized with respect to the required output is determined.

[0014] Then, so as to operate at the operating point,
A control amount such as a fuel supply amount or an intake air amount of the internal combustion engine and an output rotation speed of the internal combustion engine by changing the continuously variable transmission are controlled. As a result, the exhaust gas is purified by the exhaust gas purifying means, so that it is possible to clear a stricter regulation value regarding exhaust gas and at the same time prevent deterioration of fuel efficiency.

According to a second aspect of the present invention, in the first aspect, the optimum operating point calculating means determines the optimum operating point according to an exhaust gas temperature of the internal combustion engine, and the operating point at which the total fuel consumption is the minimum. Operating point changing means for setting the operating point at which the combined fuel consumption is the minimum to an operating point on a high load and low rotational speed side or an operating point on a low load and high rotational speed side. It is a control device characterized by the following.

Therefore, according to the second aspect of the present invention, depending on the temperature of the exhaust gas, the operating point of the internal combustion engine is higher than the operating point at which the total fuel consumption is minimized or at the low engine speed or low load. The operating point changed to the higher rotation speed side is selected. For example, when the exhaust gas temperature is low, the operating point on the high load / low rotational speed side can be selected, and the control amount of the internal combustion engine and the operation of the continuously variable transmission are set so that the operating state at that operating point is achieved. The gear ratio is controlled. As a result, the catalyst bed temperature of the exhaust gas purification means increases, and the activity of the exhaust gas purification means is maintained.
Alternatively, it can promote its activity. In particular, in a diesel engine, since the operation is performed in a state where the excess air ratio is low, the effect of increasing the exhaust gas temperature is enhanced.

On the contrary, when the exhaust gas temperature is low, the operating point on the low load / high rotational speed side can be selected, and the control amount of the internal combustion engine and the operating state at that operating point are selected. The speed ratio of the continuously variable transmission is controlled. As a result, operation with a reduced amount of specific pollutants in the exhaust gas becomes possible.

Further, the invention according to claim 3 is a control apparatus for a vehicle, wherein a continuously variable transmission capable of controlling an output rotation speed of the internal combustion engine is connected to an output side of the internal combustion engine capable of controlling an engine load. An exhaust purifying means disposed in an exhaust system of the internal combustion engine for purifying the exhaust gas and consuming fuel for purifying the exhaust; and a torque meeting a demand when the exhaust purifying means is not functioning effectively. And instructs the internal combustion engine of an operation state in which the amount of pollutants in the exhaust gas is low in preference to fuel efficiency, and when the exhaust gas purifying means is functioning effectively, a torque corresponding to the request is output. A control device, comprising: operating state instructing means for instructing the internal combustion engine of an operating state in which fuel consumption is low in priority to the amount of pollutants output and emitted by the internal combustion engine.

Therefore, in the third aspect of the present invention, the fuel is burned by driving the internal combustion engine, and the fuel is consumed when the exhaust gas is purified by the exhaust gas purifying means. When the exhaust gas purifying means is not functioning effectively, the internal combustion engine is operated in a state in which the amount of pollutants in the exhaust gas is reduced in preference to a reduction in fuel consumption. On the other hand, when the exhaust gas purifying means is functioning effectively, even if the amount of pollutants emitted by the internal combustion engine may relatively increase, an operation state in which fuel consumption is reduced is selected, An instruction to drive the internal combustion engine in the operating state is output. In that case,
The pollutants are removed by the exhaust gas purifying means functioning effectively, so that the amount of pollutants emitted from the vehicle is reduced. As a result, the generation of the pollutant itself is suppressed, or the pollutant is removed by the exhaust gas purifying means, so that the vehicle can conform to stricter exhaust gas regulations.

Still further, the invention according to claim 4 is the invention according to claim 3.
When the operating state indicating means is not functioning effectively, the ratio between the change rate of fuel consumption in the direction along the equal output line of the internal combustion engine and the change rate of pollutants in the exhaust gas. The point on the line connecting the operating points equal to each other is set as the target operating point, and when the exhaust gas purifying means is effectively functioning, the amount of fuel consumed by the internal combustion engine to perform the required output is Means for instructing the operating state of the internal combustion engine as a target operating point with an operating point set based on an operating point at which the total fuel consumption obtained by adding the fuel amount consumed by the exhaust gas purifying means is the minimum. It is a control device to perform.

Therefore, according to the fourth aspect of the present invention, in a state where the exhaust gas purifying means does not function effectively because the temperature of the exhaust gas purifying means is lower than the activation temperature or the like, it is difficult to remove pollutants by the exhaust gas purifying means, and at the same time, the exhaust gas is exhausted. Since no fuel is consumed by the purification means, a point on the line connecting the operating points where the rate of change in fuel consumption in the direction along the equal power line of the internal combustion engine is equal to the rate of change in pollutants generated in the internal combustion engine Is selected as the target operating point. That is, the internal combustion engine is operated at an operating point at which both the amount of fuel consumed by combustion in the internal combustion engine and the amount of pollutants generated in the internal combustion engine are minimized. On the other hand, when the temperature of the exhaust gas purifying means is functioning effectively, the exhaust gas purifying means removes pollutants with the consumption of fuel. The operating point set based on the operating point at which the total fuel consumption with the fuel consumption of the minimum is the smallest is set as the target operating point. As a result, it is possible to reduce both fuel consumption and the amount of pollutants emitted from the vehicle regardless of whether the exhaust gas purifying means is active or inactive.

According to a fifth aspect of the present invention, a continuously variable transmission capable of controlling the output speed of the internal combustion engine is connected to the output side of the internal combustion engine capable of controlling the engine load. And the control point of the internal combustion engine is controlled by the continuously variable transmission so that the internal combustion engine is operated at the operating point. The operating point is set so that the ratio between the change rate of the fuel consumption and the change rate of the generation amount of the predetermined pollutant in the exhaust gas when the operating state is changed while maintaining the constant is equal for a plurality of outputs of the internal combustion engine. Target operating point setting means for setting as an operating point; and operating instruction means for outputting an operating instruction so that the operating state of the internal combustion engine becomes an operating state at the target operating point for a required output. It is a control device according to claim is.

According to the fifth aspect of the present invention, the change rate of the fuel consumption when the load and the rotation speed of the internal combustion engine are changed while the output is kept constant, and the change rate of the generation amount of pollutants in the internal combustion engine are determined. A ratio is determined, and an operating point at which the ratio is equal for a plurality of outputs is set as a target operating point, and the operating state of the internal combustion engine is controlled so that the operation at the target operating point for the required output is performed. Is done.
As a result, fuel consumption and the amount of pollutants emitted from the vehicle are reduced.

According to a sixth aspect of the present invention, a continuously variable transmission capable of controlling the output speed of the internal combustion engine is connected to the output side of the internal combustion engine capable of controlling the engine load. And an operating point of the internal combustion engine is determined by the number of the internal combustion engine, and the continuously variable transmission controls the output speed of the internal combustion engine so that the internal combustion engine is operated at the operating point. In a low output state in which the output state is such that the amount of predetermined pollutants generated is equal to or less than a predetermined reference value, the operating point of the internal combustion engine at which the amount of the predetermined pollutants in the exhaust gas becomes substantially constant for each output Operating point setting means for setting an operating state of the internal combustion engine to an operating state at the target operating point for a required output. When A control device which is characterized in that it comprises.

Therefore, according to the invention of claim 6, when the internal combustion engine is operated at a low output, that is, in a low output state in which the generation amount of a predetermined pollutant is equal to or less than a predetermined value, the required output changes. In this case, the operating point is set so that the amount of the pollutants generated is the same as before, that is, constant, and the operation of the internal combustion engine at that operating point is executed. In this case, the degree of deterioration of fuel efficiency is small. As a result, it is possible to perform operation with low emission of pollutants and good fuel economy.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described based on specific examples. The internal combustion engine targeted by the present invention is a power unit that outputs power by burning fuel such as a diesel engine or a gasoline engine, and is mounted on a vehicle as an example and is mainly used as a power source for traveling. It is an internal combustion engine. FIG. 2 schematically shows an example in which a direct-injection diesel engine (hereinafter simply referred to as an engine) 1 is used as a power source of a vehicle. This engine 1 is an internal combustion engine of a type that directly injects fuel into a cylinder (cylinder). In order to enable high-pressure fuel injection,
A common rail type electronically controlled fuel injection system 2 is provided. The electronic control fuel injection system 2 may have a known structure.

The engine 1 shown in FIG. 2 is provided with an exhaust turbine type supercharger, that is, a turbocharger 3. An intake pipe 6 having an air cleaner 5 interposed is connected to an intake port of the compressor 4, and an intake manifold 8 is connected to a discharge port of the compressor 4 via an intercooler 7 for lowering intake air temperature.
Is connected.

An exhaust manifold 9 connected to each cylinder is connected to an inlet of a turbine 10 in the turbocharger 3. Further, a catalytic converter 11 having an exhaust purification catalyst is connected to an outlet of the turbine 10. An air-fuel ratio sensor 12 and a pressure sensor 13 for detecting the pressure of exhaust gas flowing into the catalytic converter 11 are arranged upstream of the catalytic converter 11. Further, a temperature sensor 14 for detecting a catalyst temperature is provided.

Here, the exhaust purification catalyst will be described. In the example shown in FIG. 2, a NOx storage reduction type catalyst is used. This has the function of storing NOx, one of the pollutants in exhaust gas, in the form of nitrate nitrogen in an oxidizing atmosphere, and reducing the stored nitrate nitrogen in a reducing atmosphere to release it as nitrogen gas. Have. Also,
Since active oxygen is generated during storage and reduction of NOx,
It has a function of oxidizing and removing soot (PM) adhering to the surface by the active oxygen and oxygen in the exhaust gas. Therefore, it is necessary to change the atmosphere of the exhaust purification catalyst between an oxidizing atmosphere and a reducing atmosphere at predetermined time intervals. This is executed by switching to the rich air-fuel ratio that has been increased. The control for enriching the air-fuel ratio in order to release nitrogen from the exhaust purification catalyst may be temporary, and such a temporary enrichment of the air-fuel ratio is referred to as "rich spike".

Further, the engine 1 shown in FIG. 2 is provided with an exhaust gas recirculation device in order to reduce NOx in exhaust gas. That is, EGR for cooling the exhaust gas to be recirculated
An EG that performs control of the cooler 15 and execution / stop of recirculation and control for maintaining a constant recirculation rate (EGR rate).
The exhaust manifold 9 and the intake manifold 8 are connected via an R valve 16.

The output side of the engine 1 is provided with a continuously variable transmission (C
VT) 17 are connected. This continuously variable transmission 17
The point is that the transmission is capable of continuously changing the gear ratio, and a belt-type continuously variable transmission and a traction (toroidal) continuously variable transmission are employed.

An engine electronic control unit (E) for electrically controlling the fuel injection amount and its injection timing, execution / stop of exhaust gas recirculation, opening of a throttle valve (not shown) and the like in the engine 1 described above. -ECU) 18;
A transmission electronic control unit (T-
(ECU) 19. These electronic control devices 18 and 19 are mainly configured by a microcomputer, and include a required output amount and a vehicle speed, an engine coolant temperature, an oil temperature of the continuously variable transmission 17, an oil temperature of the continuously variable transmission 17, which are expressed by an accelerator opening, and the like. , 13, 14 based on the detection signals, etc.
The throttle opening and the fuel injection amount (that is, the engine load), the speed ratio in the continuously variable transmission 17 (that is, the engine speed), and the like are controlled.

In the above-described engine 1, fuel is injected into each cylinder and burned, and mechanical energy generated thereby is output as driving force. Therefore, the amount of fuel consumed is controlled to be as small as possible within a range satisfying the required output amount. In addition, pollutants such as NOx generated by the combustion of fuel in the cylinder are generated by the catalytic converter 11.
Before the storage amount is saturated, the amount of fuel in the exhaust gas is increased to create a reducing atmosphere, and nitrate nitrogen stored in the catalyst is reduced and released as nitrogen gas. In other words, fuel is consumed by increasing the supply amount of fuel for purifying the exhaust gas. As described above, fuel is consumed for driving the engine 1 and fuel is consumed for purifying the exhaust gas, in other words, reducing the emission amount of the air pollutants from the vehicle.

Therefore, the amount of fuel consumed per unit of output is the sum of the amount of fuel consumed for driving the engine 1 and the amount of fuel consumed for purifying the exhaust gas. The control device according to the present invention controls the engine 1 and the continuously variable transmission 17 so that the total fuel consumption is minimized.
Control. More specifically, the intake air amount and / or the fuel injection amount of engine 1 is controlled so as to have a torque corresponding to the required output amount, and the required output is controlled so as to achieve the required output with the minimum fuel consumption. The gear ratio of the step transmission 17, that is, the engine speed is controlled.

The operating point of the engine 1 at which the total fuel consumption is minimized is given as follows. That is, pollutants emitted from the vehicle together with the exhaust gas, for example, N
The emission control value of Ox is determined as the emission amount when the traveling mode is determined based on the vehicle speed, the duration thereof, and the like, and the vehicle is driven according to the traveling mode. Therefore, the total fuel consumption in the traveling mode, that is, the mode fuel consumption (g) F is expressed by the following equation 1.

(Equation 1)

Here, pi is the output of engine 1 (k
W), ti is the duration (h) of the output pi during mode driving, tidl is the duration (h) of idling, si
Is the fuel consumption rate SFC (g / kW) on the
h), sidl is the fuel efficiency in idling condition (g /
h) and ni are the NOx emissions (g
/ KWh), nidl is the NOx emission amount (g / h) in the idling state, and k is the ratio of the necessary fuel amount at the time of the above-described rich spike to make the exhaust purification catalyst a reducing atmosphere and the NOx amount reduced at that time ( Rich spike fuel amount / NO
x) and Nt are target NOx emissions (predetermined NOx emissions below regulatory values).

Since the idling fuel consumption (tidl * sidl), the idling NOx emission (tidl * nidl), and the target NOx emission Nt are constant values that are not related to the driving state, the expression 1 is It can be rewritten as in Equation 2 below.

(Equation 2)

In equation (2), pi is determined according to the engine 1 mounted on the vehicle, and a predetermined output pi
The running time ti at is determined by the running mode in which emission control values for pollutants such as NOx are determined. FIG. 3 is a diagram showing an example of the traveling mode. Therefore, in order to minimize the mode fuel consumption amount F, it is necessary to control the operating state of the engine 1 so that (si + k * ni) on the right side of Equation 2 is minimized. That is, the operating point at which the sum of the fuel efficiency on the iso-output line corresponding to the required output and the value obtained by converting the NOx emission amount on the iso-output line into fuel is minimized, and the engine 1 The load and the rotation speed may be controlled so as to operate at a point.

Incidentally, since the output of the engine 1 is the product of the torque and the rotation speed, the equal output line is expressed as shown in FIG. 1 using the torque and the engine rotation speed as parameters. If the fuel efficiency SFC is superimposed on this diagram, it is as shown by a thin solid line. The NOx emissions are as shown by the broken lines. The fuel efficiency SFC and NOx emissions are
These are indicated by lines (contour lines) connecting points having the same value, and the value becomes smaller on the center side of each contour line. As is known from FIG. 1, the contour line indicating the NOx emission amount is on the low torque side (low load side) with respect to the contour line of the fuel efficiency SFC.
Therefore, when the fuel consumption for obtaining a predetermined output is suppressed, the generation amount of NOx increases, and the fuel consumption amount required for removing NOx increases. That is, fuel efficiency and NOx
There is a conflicting relationship with emissions.

Therefore, the above (si + k * ni) corresponding to the total fuel efficiency is represented by a thick solid line in FIG. The line connecting the minimum values of the combined fuel consumption rates is the optimum fuel consumption line with the lowest fuel consumption in a state where the storage and reduction of NOx can be executed sufficiently and sufficiently. Since the minimum controllable engine speed is determined, the optimal fuel consumption line is a straight line at the minimum engine speed.

In the control device according to the present invention, at least in a steady running state, the optimum operation determined as the intersection between the equal output line corresponding to the required output amount represented by the accelerator opening and the above-described optimum fuel consumption line is obtained. The engine 1 and the continuously variable transmission 17 are controlled so that the engine 1 is driven at this point. Except for the target engine speed Net, the manner of control is the same as conventionally known control using a continuously variable transmission. One example is shown in FIG.

In FIG. 4, first, a target driving force Fd is obtained based on the accelerator opening Acc and the vehicle speed V (block B1). Here, the accelerator opening Acc is control data obtained by electrically processing the depression amount of an accelerator pedal (not shown), and is used as a parameter indicating a request for acceleration or deceleration, that is, a request for driving force. Have been. Therefore, a signal of a drive request for cruise control for maintaining the vehicle speed constant is sent to the accelerator opening A
It can be adopted as a parameter instead of cc. The same applies to the vehicle speed. The rotation speed of another appropriate rotating member having a one-to-one relationship with the vehicle speed V can be adopted instead of the vehicle speed V.

The determination of the target driving force Fd based on the accelerator opening Acc and the vehicle speed V is performed based on a map prepared in advance. Specifically, the relationship between the vehicle speed V and the driving force Fd is determined in advance as a map using the accelerator opening Acc as a parameter. In that case, the driving force Fd is determined so as to reflect the characteristics of the target vehicle. Then, the target driving force Fd is obtained based on the map.

The target driving force Fd obtained in block B1
A target output P is obtained based on the current vehicle speed V (block B2). That is, the target output P is the product of the target driving force Fd and the vehicle speed V.

In order to control the gear ratio, the target output P
Is determined (Block B3). As described above, in the steady running state, control is performed in accordance with the optimal fuel consumption line. Therefore, the operating state when the target output P is reached is the operating state at the operating point on the optimal fuel consumption line. That is, when the target output P is reached, the engine 1
Is controlled to a state based on the optimum fuel efficiency line, and therefore, the target engine speed Net uses a target engine speed table (diagram) in which the output and the speed are determined based on the optimum fuel efficiency line shown in FIG. Is required.

Based on the target engine speed Net and the detected actual engine speed Ne, the speed change control means controls the speed ratio so that the actual engine speed becomes the target engine speed (block B4). This transmission control means is specifically the transmission electronic control unit 19 shown in FIG. 2 described above.

On the other hand, in order to control the engine 1, a target engine torque To is obtained based on the target output P and the current engine speed Ne (block B5). This is performed, for example, by dividing the target output P by the current engine speed Ne. The equation shown in FIG. 4 is obtained by performing a process for aligning the units.
Therefore, the angular speed of the output shaft of the engine 1 can be adopted instead of the engine speed Ne.

The engine torque control means controls the engine 1 so as to attain the target engine torque To thus obtained (block B6). Specifically, the engine electronic control unit (E-ECU) 1 shown in FIG.
8 controls the fuel injection amount or the opening of an electronic throttle valve (not shown).

The operating state of the engine 1, that is, the operating point, which is set by controlling the output torque and the rotational speed in this manner is an operating point on the optimal fuel efficiency line corresponding to the required output amount. Therefore, the engine 1 is operated in a state where both the fuel efficiency and the amount of NOx emission are minimized, and the amount of the pollutant NOx in the exhaust gas can be reduced to the target value by the catalytic converter 11. In other words, stricter emission regulations for pollutants in exhaust such as NOx can be cleared, and fuel economy can be improved.

The functional means of the block B3 in FIG. 4 for obtaining the target engine speed Net in accordance with the required output from the map based on the optimum fuel efficiency line shown in FIG.
Corresponds to an optimal operating point calculating means in the invention of claim 1,
Also, the functional means of the shift control means of block B4 and the engine torque control means of block B6 in FIG.
It corresponds to the operation control means in the invention of claim 1.

When the exhaust gas of the engine 1 is subjected to the so-called post-treatment by the catalytic converter 11, the temperature of the catalyst must be maintained at the activation temperature or higher in order for the catalytic converter 11 to function as expected. . Then, the temperature of the catalyst is increased or maintained by the heat of the exhaust gas and the heat generated by the reaction of the catalyst. Therefore, when the temperature of the exhaust gas generated from the engine 1 is low, the temperature of the catalyst in the catalytic converter 11 may decrease. In this case, if the engine 1 is operated at the operating point on the optimal fuel efficiency line shown in FIG. 1, the activity of the exhaust purification catalyst may decrease, and the amount of pollutants emitted from the vehicle may increase.

In order to avoid such inconvenience, in an area where the engine exhaust temperature is low, the operating point of the engine 1 is set to an operating point deviating from the above-mentioned operating point on the optimal fuel efficiency line. FIG. 5 is a flowchart for explaining an example of the control. First, it is determined whether or not the engine exhaust temperature is in a low region (step S1). The determination may be made based on a temperature detected by, for example, a temperature sensor or a cooling water temperature sensor provided in an exhaust system of the engine 1, or may be estimated based on a load history such as a throttle opening or a fuel injection amount. May be done.

If a negative determination is made in step S1, the exhaust gas temperature is not particularly low.
The operating point of the engine 1 is set to an operating point on the optimal fuel efficiency line shown in FIG. 1 (step S2). That is, the speed ratio of the continuously variable transmission 17 is controlled so that the engine speed is determined based on the optimum fuel efficiency line.

On the other hand, if a positive determination is made in step S1, the operating point of the engine 1 is set to an operating point different from the operating point on the optimal fuel efficiency line shown in FIG. 1 (step S3). As an example, when the engine speed is equal to or less than a predetermined value, the engine 1 is operated at an operating point that is shifted to a high load / low rotational speed side with respect to an operating point on the optimal fuel consumption line. The operating point is shown as a thick solid line A in FIG.

The operating point is changed from the operating point on the optimal fuel economy line to a solid line A.
By changing to the above operating point, the temperature of the exhaust gas from the engine 1 increases, and as a result, the exhaust purification catalyst receives heat from the exhaust gas, and the catalyst bed temperature increases to maintain its activity or reduce the activity. Can be promoted. In particular, in a diesel engine, since the operation is performed in a region where the excess air ratio is low by increasing the fuel supply amount (fuel injection amount), the effect of increasing the exhaust gas temperature is enhanced. Therefore, the operating time in a state where the activity of the exhaust gas purification catalyst is low is shortened. Therefore, even if the operating point is changed to a high load and a low rotational speed side, the total amount of pollutants discharged together with the exhaust gas from the vehicle is reduced. Can be reduced.

Another example in which the operating point is changed is that, when the engine speed is equal to or less than a predetermined value, the operating point is shifted to the low load / high speed side with respect to the operating point on the optimal fuel consumption line. Is an example in which the engine 1 is operated. The operating point is shown as a thick solid line B in FIG.

The operating point is changed from the operating point on the optimal fuel efficiency line to a solid line B.
By changing to the upper operating point, although the fuel consumption is reduced, the operating point approaches the operating point at which the NOx emission is minimized. Therefore, even if the function of removing the NOx in the exhaust purification catalyst is reduced, the NOx is generated in the engine 1. Since the amount of NOx itself is small,
The amount of NOx emitted from the vehicle can be reduced as a whole.

The control for changing to the operating point on the solid line A in FIG. 6 is opposite to the control for changing to the operating point on the solid line B, but the fuel consumption rate, NOx emission characteristics, and exhaust temperature characteristics are controlled. Since the characteristics and the like of the NOx purifying catalyst differ for each engine or vehicle, any advantageous operating point change may be performed for each engine 1 or each vehicle. Therefore, the functional means of step S3 shown in FIG. 5 corresponds to the optimum operating point changing means in the invention of claim 2.

When the above-described catalytic converter 11 is not functioning or in a vehicle without the catalytic converter 11, no fuel is consumed for purifying the exhaust gas.
The operating point on the optimum fuel efficiency line shown in FIG. 6 is not always the operating point at which the fuel efficiency and the NOx emission amount become optimal. In that case, the fuel efficiency SFC is small and the NOx
The engine 1 is controlled by selecting an operating point where the amount of pollutants generated is small. Hereinafter, an example of the control will be described.

Engine 1 Isopower Line and Fuel Efficiency SFC
FIG. 7 is a graph showing the NOx emission amount using the output torque and the engine speed as parameters. On the other hand, the fuel consumption amount F and the NOx emission amount N when the vehicle travels in the predetermined traveling mode are expressed by Expression 3.

(Equation 3)

Therefore, in order to find a combination of (si, ni) that satisfies the target NOx emission amount and minimizes the fuel consumption F, s for a predetermined output pi is determined.
FIG. 8 shows the relationship between i and ni. That is, (dsi / dl) and (dni
/ Dl), and the ratio (dsi / dni) (ie, the rate of change in fuel efficiency / the rate of change in NOx) is determined.

In the case where the NOx emission amount is reduced from the predetermined operation state and is adjusted to the target value, moving the point on the iso-output line having the smallest (dsi / dni) minimizes the deterioration of fuel efficiency. If this idea is repeated on each iso-output line to achieve the target NOx emission,
The line at which the fuel efficiency is optimal with respect to the Ox target value is a line connecting points at which the value of (dsi / dni) is equal in each of the equal output lines. This is shown as (equal dSFC / dNOx line) in FIG.

The frequency of each output in the mode (ti * pi
However, the situation is the same even when considering (2). That is, when the in-mode frequency (ti * pi) of each output is considered, as shown in FIG. 9, the frequency is mapped in both directions of the fuel consumption axis and the NOx axis, and the relationship between the fuel consumption and NOx is similar. Becomes Therefore, the value of “fuel consumption change rate / NOx change rate” does not change.

The above (equal dSFC / dNOx line) is shown in FIG.
As shown in FIG. 7, a plurality of lines can be drawn, and which of them is the optimum fuel consumption line depends on the NOx target value, the running mode and the engine. Therefore, when actually controlling the vehicle, the optimal fuel consumption line is experimentally obtained, and the data is stored in the electronic control device 18 as, for example, a map value, which is stored in, for example, the block shown in FIG. A target engine speed is obtained by utilizing the information in B3. The lower limit of the target value that can be dealt with is the NOx emission amount on the NOx optimum line (the line connecting the points where the NOx emission amount on the equal output line is the minimum).

Therefore, in the control device according to the present invention,
Fuel consumption can be minimized while maintaining the amount of NOx generated in the engine 1 at the target value. Therefore, even if there is no removal means such as a catalyst for removing pollutants such as NOx generated in the engine 1, or even if the removal means is not functioning effectively,
It is possible to obtain a vehicle that satisfies the regulation value regarding exhaust gas, and at the same time, obtain a vehicle that is excellent in fuel efficiency.

As described above, the optimal fuel consumption line shown in FIG.
This can be adopted when the catalytic converter 11 mounted on the vehicle is not functioning effectively. Therefore, in a vehicle equipped with the catalytic converter 11, the optimal fuel efficiency line shown in FIG. 7 and the optimal fuel efficiency line shown in FIG. Solid line A with this changed
And a fuel consumption line (operation line) indicated by a solid line B, and these fuel consumption lines are switched between when the catalytic converter 11 as the exhaust gas purifying means is functioning effectively and when it is not functioning effectively. For example, it is used in the block B3, and the engine speed can be controlled to a speed at which fuel efficiency is improved according to each situation.

For example, as shown in FIG. 10, first, it is determined whether or not the catalyst is not activated (step S11). This can be determined based on the catalyst temperature as an example. If the catalyst temperature is equal to or higher than the activation temperature and the catalyst is already in the active state and a negative determination is made in step S11, the exhaust gas can be purified by the catalyst.
An operating point of the engine 1 determined based on FIG. 6 is set (step S12). On the other hand, when the catalyst temperature is lower than the activation temperature and the catalyst does not show the activity, and the determination is affirmative in step S11, the exhaust gas cannot be purified by the catalyst. An operating point of the engine 1 determined based on FIG. 7 is set in order to give priority to reducing the NOx amount generated in step S13 (step S13).

In this case, in the control using the optimum fuel consumption line shown in FIG.
The control is to reduce the amount of Ox. In the control using the optimum fuel consumption line shown in FIG. 6 or the solid lines A and B based on the optimum fuel consumption line, the fuel consumption is controlled in preference to the amount of NOx generated in the engine 1. Therefore, these optimal fuel efficiency lines or the solid lines A and B are switched and used, and the functional means of the blocks B3 and B4 for instructing the operating state (specifically, the number of revolutions) of the engine 1 based on the lines or the step S11 described above. , S12 correspond to the operating state indicating means in claims 3 and 4.

In a vehicle not provided with an exhaust gas purifying means such as the catalytic converter 11, the engine 1 is controlled to operate at the operating point on the optimum fuel efficiency line shown in FIG. Specifically, the control is performed by using the map based on the optimal fuel consumption line to obtain the target engine speed in the block B3 described above, and to set the gear ratio of the continuously variable transmission 17 so as to achieve the target engine speed. Is controlled by controlling Therefore, the functional means of the block B3 configured to perform such control corresponds to the target operating point setting means in claim 5.

As shown in FIG. 7, the minimum point of fuel efficiency is on the high load side, whereas the minimum point of NOx emission is on the low load side. The operating point or the optimal fuel efficiency line at which the fuel efficiency is minimized is located between these minimum points. The optimal fuel efficiency line or engine operating line connecting the points where the fuel efficiency for each output is minimized is the NOx in the low load / low speed region, in other words, the NOx diagram in which the output torque and the speed are parameters. In a region on the low rotation speed side and on the high load side (high torque side) from the minimum point of the emission amount, a curve approximating the NOx line, for example, connecting points having the same NOx emission amount is obtained. Therefore, in at least a part of this region, the engine 1
May be a point on the engine operating line set along the NOx line.

FIG. 11 shows an example of the engine operating line thus obtained. When the target operating point of the engine 1 is set on the engine operating line shown in FIG.
Although the amount of Ox emission does not increase, the fuel efficiency is higher than the operating point on the optimum fuel efficiency line in FIG. 7 described above. However, the degree of deterioration of the fuel efficiency is slight, and practically causes no problem.

When controlling the engine 1 based on the engine operating line shown in FIG. 11, the control may be executed in the same manner as the control in each of the above-described specific examples. That is, a map of the target engine speed based on the engine operation line shown in FIG. 11 is prepared, and the target engine speed may be obtained in block B3 in FIG. Therefore, FIG.
The functional means of the block B3 using the engine operation line corresponds to the target operating point setting means in claim 6, and the block for controlling the gear ratio so that the target engine speed obtained in the block B3 is obtained. The shift control means of B4 corresponds to the driving instruction means of claim 6.

In the above example, an example was described in which NOx was used as a pollutant in the exhaust gas. However, the present invention is not limited to the above-described specific examples, and the emission amount of substances other than NOx is reduced. The present invention can also be applied to a control device for reducing power consumption. Although not specifically described in the above specific example, FIG.
7 and FIG. 11 show characteristic lines when other NOx reduction control such as EGR is executed.
Further, in the above specific example, the air-fuel ratio is reduced to supply the fuel to the catalyst which is the exhaust gas purifying means.
Alternatively, the fuel may be directly added to the exhaust gas and supplied to the catalyst.

[0074]

As described above, according to the first aspect of the present invention, the total fuel consumption of the fuel including the combustion in the internal combustion engine and the consumption in the exhaust gas purifying means is reduced to the required output. On the other hand, a minimum operating point of the internal combustion engine is required. For example, the fuel consumption when the internal combustion engine is operated for a predetermined time at a predetermined output and the fuel required to reduce a predetermined pollutant in exhaust gas discharged during the predetermined time to a regulation value. An operating point at which the total fuel consumption obtained by adding the consumption amount to the required output is minimized with respect to the required output is determined. Then, the control amount such as the fuel supply amount or the intake air amount of the internal combustion engine and the output rotation speed of the internal combustion engine by changing the continuously variable transmission are controlled so that the operation at the operating point is performed. By purifying the exhaust gas by the purifying means, it is possible to clear the stricter regulation value regarding exhaust gas, and at the same time, it is possible to prevent deterioration of fuel efficiency.

According to the invention of claim 2, according to claim 1,
According to the temperature of the exhaust gas,
Since the operating point of the internal combustion engine is changed to the high load / low rotational speed side or the low load / high rotational speed side with respect to the operating point at which the total fuel consumption is minimized, for example, when the exhaust gas temperature is low, Therefore, the operating point on the high load / low rotational speed side is selected, and as a result, the catalyst bed temperature of the exhaust gas purifying means is increased, and the activity of the exhaust gas purifying means can be maintained or its activity can be promoted. In particular, in a diesel engine, since the operation is performed in a state where the excess air ratio is low, the effect of increasing the exhaust gas temperature is enhanced. Conversely, when the exhaust gas temperature is low, an operating point on the low load / high rotational speed side is selected, and accordingly, an operation can be performed in which the amount of a specific pollutant in the exhaust gas is reduced.

Further, according to the third aspect of the present invention, when the exhaust gas purifying means is not functioning effectively, the internal combustion engine is operated in a state where the amount of pollutants in the exhaust gas is reduced in preference to a reduction in fuel consumption. On the contrary, when the exhaust gas purifying means is functioning effectively, even if the amount of pollutants emitted by the internal combustion engine may be relatively increased, the fuel consumption may be reduced. Since the internal combustion engine is operated, the amount of pollutants in the exhaust gas can be reduced, the fuel efficiency can be improved, and the vehicle can be compliant with stricter exhaust gas regulations.

Further, according to the invention of claim 4, when the exhaust gas purifying means does not function effectively, the change rate of the fuel consumption in the direction along the equal output line of the internal combustion engine and the change of the pollutant generated in the internal combustion engine. When a point on the line connecting the operating points having the same ratio with the ratio is selected as the target operating point, and the exhaust gas purifying means functions effectively with respect to the target operating point, the fuel consumption in the internal combustion engine and the exhaust gas purifying means The operating point set based on the operating point that minimizes the fuel consumption with the fuel consumption of the vehicle is set as the target operating point. And the amount discharged from the fuel cell can be reduced.

According to the fifth aspect of the present invention, the change rate of the fuel consumption and the change in the amount of pollutants generated in the internal combustion engine when the load and the rotation speed of the internal combustion engine are changed while the output is kept constant. An operating point at which the ratio becomes equal for a plurality of outputs is set as a target operating point, and operation of the internal combustion engine is performed at the target operating point for the required output. Since the state is controlled, both fuel consumption and the amount of pollutants emitted from the vehicle can be reduced.

Further, according to the invention of claim 6, when the internal combustion engine is operated at a low output, that is, in a low output state in which the generation amount of a predetermined pollutant is equal to or less than a predetermined value, the request is made. If the output changes, the operating point is set so that the amount of the pollutants generated is the same as before, that is, constant, and the internal combustion engine is operated at that operating point. The operation can be performed with less fuel consumption and good fuel economy.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an optimum fuel consumption line obtained by adding a fuel consumption rate on an equal output line and a fuel consumption amount corresponding to a NOx emission amount.

FIG. 2 is a diagram schematically illustrating an example of a power system of a vehicle equipped with an internal combustion engine as an object of the present invention.

FIG. 3 is a diagram showing an example of a traveling mode.

FIG. 4 is a block diagram showing a control example in which an engine speed and an engine torque are individually controlled using a continuously variable transmission.

FIG. 5 is a flowchart illustrating an example of control for changing an operating point based on exhaust gas temperature.

FIG. 6 is a diagram illustrating an example of an optimal fuel consumption line (engine operation line) changed based on exhaust gas temperature.

FIG. 7 is a diagram illustrating an example of an optimal fuel consumption line when an exhaust purification catalyst is not used.

FIG. 8 shows fuel efficiency si, NOx emission amount ni, dsi / dl, dni / dl, dsi / dn along a predetermined equal output line.
FIG. 3 is a diagram showing i.

FIG. 9 is a diagram showing an example in which dsi / dni for a predetermined output is mapped according to a predetermined traveling mode.

FIG. 10 is a flowchart for explaining a control example of changing an operating point before and after activation of an exhaust purification catalyst.

FIG. 11 is a diagram showing an example of an engine operation line approximated to an equal NOx line in a low output region.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 11 ... Catalytic converter, 17 ... Continuously variable transmission, 18 ... Engine electronic control unit, 19 ... Transmission electronic control unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 9/02 F02D 9/02 N 29/00 29/00 H 41/04 360 41/04 360G 360D 360E 380 380G 380D 380E F-term (reference) 3D041 AA19 AA26 AC02 AC03 AC19 AC20 AD02 AD10 AD14 AD51 AE04 AE07 AE31 3G065 AA01 CA00 DA04 EA08 EA09 EA11 EA12 GA08 GA09 GA10 GA11 GA46 3A09 AAB AACA CB DA01 DA02 DA04 DB06 DB07 DB08 DB10 EA01 EA07 EA16 EA18 EA30 EA31 EA32 EA34 EA39 FA12 FA13 FA14 FA16 FB10 FB11 FB12 HA36 HA39 HB03 HB05 HB06 3G093 AA06 AB00 AB01 BA19 BA20 CA06 CA07 DA05 DA03 DA03 DA03 DA03 HA02 HA04 HA11 HA13 JA02 JA25 KA08 KA09 KA24 KA25 LA03 LB11 MA11 NC02 PD11Z PD12Z PE01Z PE 08Z PF01Z PF03Z

Claims (6)

[Claims] 1. A control device for a vehicle in which a continuously variable transmission capable of controlling an output rotation speed of the internal combustion engine is connected to an output side of the internal combustion engine capable of controlling an engine load, the control device being disposed in an exhaust system of the internal combustion engine. Exhaust gas purifying means for purifying exhaust gas and consuming fuel for purifying the exhaust gas; and a fuel amount consumed by the exhaust gas purifying catalyst to an amount of fuel consumed by the internal combustion engine to perform a required output. Optimum operating point calculation means for determining the operating point at which the total fuel consumption is the minimum as the optimum operating point, and the operating state of the internal combustion engine is set to the operating state at the optimal operating point. A control device for a vehicle, comprising: an operation control unit that controls an engine load and controls a speed ratio of the continuously variable transmission. 2. The system according to claim 1, wherein said optimum operating point calculating means changes said optimum operating point to an operating point having a minimum total fuel consumption according to an exhaust gas temperature of said internal combustion engine. 2. The vehicle according to claim 1, further comprising an operating point changing means for setting an operating point on a high load and low rotational speed side or an operating point on a low load and high rotational speed side with respect to the operating point. Control device. 3. A control device for a vehicle in which a continuously variable transmission capable of controlling an output rotation speed of the internal combustion engine is connected to an output side of the internal combustion engine capable of controlling an engine load, the control device being disposed in an exhaust system of the internal combustion engine. Exhaust purification means for purifying exhaust gas and consuming fuel for purifying the exhaust; and when the exhaust purification means is not functioning effectively, outputs a torque corresponding to the demand and gives priority to fuel efficiency. The internal combustion engine is instructed to operate in a state in which the amount of pollutants in the exhaust gas is small, and when the exhaust gas purifying means is functioning effectively, a torque corresponding to the request is output and the internal combustion engine emits And a driving state instructing means for instructing the internal combustion engine of a driving state with low fuel consumption prior to the amount of pollutants to be controlled. 4. The operating state indicating means, when the exhaust gas purifying means is not functioning effectively, changes a fuel consumption rate in a direction along an equal output line of the internal combustion engine and a change in exhaust pollutants. When the point on the line connecting the operating points having the same ratio with the ratio is set as the target operating point, and when the exhaust gas purifying means is functioning effectively, the internal combustion engine is consumed to perform the required output. Means for instructing the operating state of the internal combustion engine with a target operating point set based on an operating point at which the total fuel consumption obtained by adding the amount of fuel consumed by the exhaust gas purification means to the amount of fuel consumed by the exhaust gas purifying means is the minimum. The control device for a vehicle according to claim 3, wherein: 5. A continuously variable transmission capable of controlling an output rotation speed of the internal combustion engine is connected to an output side of the internal combustion engine capable of controlling an engine load, and operating the internal combustion engine based on the engine load and the output rotation speed. A control device for controlling the output speed of the internal combustion engine by the continuously variable transmission such that the internal combustion engine is operated at the operating point. A target operating point in which the operating point at which the ratio between the change rate of the fuel consumption and the change rate of the generation amount of the predetermined pollutant in the exhaust gas when the fuel consumption is changed becomes equal for a plurality of outputs of the internal combustion engine is set as the target operating point. Point setting means, and operation instruction means for outputting an operation instruction so that an operation state of the internal combustion engine is an operation state at the target operation point for a required output. Both of the control device. 6. A continuously variable transmission capable of controlling an output rotation speed of the internal combustion engine is connected to an output side of the internal combustion engine capable of controlling an engine load, and operating the internal combustion engine based on the engine load and the output rotation speed. A control device for a vehicle, wherein the output speed of the internal combustion engine is controlled by the continuously variable transmission so that the internal combustion engine is operated at the operating point. In a low output state in which the generation amount of the exhaust gas is equal to or less than a predetermined reference value, the operating point of the internal combustion engine at which the amount of the predetermined pollutant in the exhaust becomes substantially constant for each output is set as the target operating point Target operating point setting means; and operating instruction means for outputting an operating instruction so that the operating state of the internal combustion engine becomes an operating state at the target operating point for a required output. To be Both of the control device.