JP2006046182A - Control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent thermal deterioration of a catalyst for exhaust emission control without deteriorating fuel economy and exhaust emission. <P>SOLUTION: A control device for a vehicle transmitting engine output to wheels via a continuously variable transmission 2 and including a catalyst device for exhaust emission control in an exhaust gas passage, is provided with an operation condition detection means 10 detecting an operation condition of an engine 1, an operation domain determination means 4 determining an operation domain based on the operation condition, and a catalyst protection means 4 performing catalyst protection control changing transmission ratio of the continuously variable transmission 2 to move out of a high exhaust temperature operation domain without changing engine output. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to control of a vehicle including an exhaust purification catalyst and a continuously variable transmission, and more particularly to control for maintaining the purification performance of the exhaust purification catalyst.

  When the engine is operated in a high load state, the heat generation amount of the engine increases and the exhaust temperature rises. Along with this, the temperature of the exhaust purification catalyst provided in the exhaust passage also rises.

  When the temperature of the catalyst increases, the catalyst metal that is supported is thermally deteriorated, so that there is a problem that the life of the catalyst device is shortened if the operation at a high temperature is continued.

  Therefore, in order to protect the catalyst, a method (catalyst protection control) is known in which the fuel injection amount is increased to lower the exhaust temperature when the temperature of the catalyst rises to such an extent that thermal degradation occurs.

  However, there is a problem that the purification efficiency of the catalyst is lowered by increasing the fuel injection amount.

In Patent Document 1, in order to reduce the above-described reduction in exhaust purification efficiency and deterioration in fuel consumption, the amount of fuel increased during catalyst protection control is not set to a constant value, but the temperature of the catalyst device or the like during a high load operation state is disclosed. , And a technique for increasing the fuel injection amount with an increase value corresponding to the detected value is described.
JP 2002-047971 A

  However, the method described in Patent Document 1 also increases the fuel injection amount in order to lower the exhaust temperature, so that the exhaust components are inevitably deteriorated during the catalyst protection control as compared with the normal operation.

  Therefore, an object of the present invention is to perform catalyst protection without deteriorating exhaust components.

  The vehicle control device according to the present invention transmits an engine output to a wheel via a continuously variable transmission, and detects an operation state of the engine in a vehicle control device having a catalyst device for exhaust gas purification in an exhaust passage. When the state detection unit, the operation region determination unit that determines the operation region based on the operation state, and the operation region determination unit determine that the operation region is the high exhaust temperature operation region, so as to be out of the high exhaust temperature operation region And catalyst protection means for performing catalyst protection control for changing the gear ratio of the continuously variable transmission so that the engine output does not change.

  According to the present invention, the exhaust temperature can be lowered and the catalyst temperature can be lowered without increasing the fuel injection amount, so that deterioration of exhaust components and fuel consumption can be prevented for catalyst protection.

  In addition, since the gear ratio is changed so that the engine output does not change, torque shock or the like does not occur at the start of the catalyst protection control, and the vehicle can travel while maintaining the vehicle speed before the start of the catalyst protection control even during the catalyst protection control. it can. Therefore, the driver does not feel uncomfortable for protecting the catalyst.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram of a system to which this embodiment is applied.

  Reference numeral 1 denotes an engine, and 2 denotes a continuously variable automatic transmission (hereinafter referred to as CVT) which is connected to the engine 1 and transmits the output of the engine 1 to a wheel (not shown) via a propeller shaft 11 or the like.

  5 is an intake passage for supplying intake air to the engine 1, 6 is a branch of an intake manifold that distributes the intake air flowing through the intake passage 5 to each cylinder, 7 is an exhaust manifold that joins the exhaust of each cylinder of the engine 1, and 8 is This is an exhaust passage through which the exhaust gas merged in the exhaust manifold 7 flows.

  Each branch 6 of the intake manifold is provided with an injector 9 for injecting fuel into the branch 6. Each injector 9 is connected to a fuel pump (not shown), and is opened according to a signal from a control unit 4 described later. The valve time is controlled. Note that the present embodiment can be applied even if the injector 9 is a so-called direct injection engine in which fuel is directly injected into the combustion chamber of each cylinder.

  The exhaust passage 8 is provided with a catalyst 3 for purifying HC, CO, NOx components and the like in the exhaust gas.

  Reference numeral 4 denotes a control unit (hereinafter referred to as C / U) as an operation region detection means, a catalyst protection means, and a fuel injection amount calculation means, and an acceleration request detection that detects the accelerator opening in addition to the detection value of the exhaust temperature sensor 10. The detected value of the accelerator opening sensor 14 as means, the crank angle sensor 13 for detecting the engine speed as the operating state detecting means, the brake pedal force sensor 15 for detecting the depression amount of the brake pedal, and the intake detected by an air flow meter (not shown) The amount of air is read. Based on these read values, the required output and fuel injection amount are calculated, the temperature of the catalyst 3 is estimated, and the operating region is determined.

  Reference numeral 12 denotes a control unit (hereinafter referred to as AT-C / U) that controls the shifting of the CVT 2 and controls the CVT 2 based on the operating state of the engine 1 calculated by the C / U 4.

  In the configuration as described above, when the engine 1 is operated in a high load state, the heat generation amount increases and the exhaust gas temperature rises, and accordingly, the catalyst 3 also becomes high temperature. Since the catalyst metal carried by the catalyst 3 is thermally deteriorated at a high temperature, the catalyst protection for keeping the temperature of the catalyst 3 at a temperature at which the catalyst 3 does not deteriorate by lowering the exhaust temperature to prevent the catalyst 3 from being deteriorated. Take control.

  Conventionally, the exhaust temperature is lowered by increasing the fuel injection amount. However, in this embodiment, the speed ratio of the CVT 2 is changed as described later, specifically, the speed ratio is increased to increase the engine speed. By lowering, the exhaust temperature is lowered without increasing the fuel injection amount.

  Here, the protection control of the catalyst 3 will be described with reference to the flowchart of FIG. 2 executed by the C / U 4 and the AT-C / U 12. Hereinafter, it demonstrates according to each step of a flowchart.

  In step S1, it is determined whether or not the operation area is area A.

  The above determination is performed using an operation region map shown in FIG. FIG. 3 is a map in which the vertical axis represents the engine torque and the horizontal axis represents the engine speed, and the operation region in which the exhaust temperature is high enough to cause thermal degradation of the catalyst 3 is the region A, and the exhaust temperature is lower than that. Let the operating region be region B.

  Therefore, the region is determined from the torque obtained from the detected values of the crank angle sensor 13, the accelerator opening sensor 14, the air flow meter, and the like and the engine speed.

  Note that the broken lines P in FIG. 3 are equal output lines. That is, even if the engine torque and the number of revolutions change, if the change moves on the same broken line P, the engine output does not change. In this embodiment, since CVT2 is used as the transmission, it is possible to change the transmission ratio so as to move on the output line.

  If it is not the region A in the determination in step S1, the process returns and the determination in step S1 is repeated.

  If it is in the region A, the process proceeds to step S2, and the time Δt until the temperature of the catalyst 3 reaches the allowable temperature Tmax set as the upper limit temperature that does not cause thermal degradation is calculated.

  Specifically, the temperature T and the temperature change rate ΔT of the catalyst 3 corresponding to the exhaust temperature are obtained in advance by experiments or the like, and the following equation (1) is obtained using the current temperature T, the allowable temperature Tmax, and the temperature change rate ΔT. ).

Δt = (Tmax−T) / ΔT (1)
When Δt is calculated in step S2, the process proceeds to step S3, and a time tx until the change of the transmission ratio of CVT2 is started is calculated.

  Specifically, the time required for changing the transmission ratio of the CVT 2 is obtained in advance by experiments or the like, and the time required for changing the transmission ratio is subtracted from the time Δt until reaching the allowable temperature calculated in step S2. Ask for.

  That is, the time tx until the change of the gear ratio is started is a time during which the normal operation can be continued after entering the region A that is the operation region of the high exhaust temperature.

  In step S4, it is determined whether or not the time t after entering the region A is longer than Δt obtained above. If it is shorter, the process returns to step S1. If it is longer, the process proceeds to step S5, and catalyst protection control is started.

  By making this determination, when the vehicle enters the region A but immediately returns to the region B, the protection control is not performed, and it is possible to prevent the unnecessary change of the gear ratio from being performed.

  In step S6, based on the detection value of the accelerator opening sensor 14, it is determined whether or not the accelerator opening change allowance ΔTVO is greater than a predetermined value X set in advance. Predetermined value X sets a change allowance that is recognized that the driver is requesting acceleration. That is, the value does not include the accelerator opening change for maintaining the vehicle speed with respect to the change in the slope of the road surface.

  If it is larger, the process proceeds to step S11, and the protection control for increasing the fuel injection amount is performed in the same manner as in the conventional case while maintaining the region A. This is because, when the increase in the accelerator opening increases, that is, when the driver is requesting acceleration, if the gear ratio of CVT2 is increased to reduce the engine speed, the response to the acceleration request is increased. This is because the fuel injection amount of the conventional fuel injection amount is kept in the high exhaust temperature region A so as to lower the exhaust temperature without lowering the engine speed, giving priority to satisfying the acceleration request. Increase the dose.

  If it is smaller, the process proceeds to step S7, and the operation region is moved to the region B along the iso-output line P by changing the transmission ratio of CVT2. Thereby, exhaust gas temperature can be lowered | hung and the temperature of the catalyst 3 can be lowered | hung. Moreover, since the output maintains the output before the change of the gear ratio while reducing the engine speed, the vehicle can travel while maintaining the vehicle speed before the start of the protection control.

  If protection control is executed in steps S11 and S7, the process proceeds to step S8, and it is determined whether or not the required output has changed during the transition from area A to area B. The required output can be obtained from detection values of the crank angle sensor 13, the accelerator opening sensor 14, the brake pedal force sensor 15, and the like. Note that this determination is different from the step S6 of determining whether or not there is an acceleration request, and also determines the deceleration request.

  If the requested output has not changed, the process returns to step S6.

  If the requested output has changed, the process proceeds to step S9, and it is determined whether or not the new requested output can be satisfied in the region B.

  If not satisfied, the process returns to step S6.

  If it can be satisfied, the process proceeds to step S10, moves to a position where the required output in the region B is satisfied, and ends the catalyst protection control.

  As described above, the catalyst protection control is performed without increasing the fuel injection amount except when there is an acceleration request, so that it is possible to prevent the deterioration of fuel consumption and the exhaust component during the protection control.

  A change in the temperature of the catalyst 3 and a change in the engine speed when the control is performed according to the above flow will be described with reference to the time chart of FIG.

  While traveling at the engine speed N0, the vehicle enters the region A from the region B at t0. Therefore, a time Δt until the allowable temperature Tmax is reached in step S2 is calculated, and a time tx until the change of the gear ratio is calculated (steps S1 to S3).

  At the time (t1) when tx has elapsed since entering the region A, protection control, that is, the change of the transmission ratio of the CVT 2 is started (steps S4 and S5). Note that the gear ratio is not changed when the vehicle moves out of the region A before tx elapses.

  By changing the speed from t1 to t2, the operation area moves from the area A to the area B (step S7). At this time, the engine speed gradually decreases from N0 to N, and accordingly, the temperature increase of the catalyst 3 also becomes moderate. Therefore, when the shift is completed at t2, the temperature of the catalyst 3 is lower than the allowable temperature Tmax.

  When there is no change in the required output between t1 and t2 or when there is a change, but the newly requested operation area is the area A, the protection control is continued, and the required output is changed to the area B. The protection control is terminated (steps S8 to S10).

  If the driver's acceleration request is detected after the start of the protection control, the gear ratio is not changed or is interrupted and returned to the region A, and the protection control is performed by increasing the fuel injection amount (steps S6 and S11).

  As described above, in the present embodiment, the following effects can be obtained.

  The engine output is transmitted to the wheels via the CVT 2 and the vehicle control device having the catalyst 3 in the exhaust passage 8 determines the operation region based on the operation state such as the engine speed, and the high exhaust temperature operation region (region A ), The catalyst protection control is performed to change the gear ratio of the CVT 2 so as to be out of the high exhaust temperature operation region (region A), so that the exhaust temperature is decreased without increasing the fuel injection amount. Thus, the temperature of the catalyst 3 can be lowered. Thereby, it can prevent that an exhaust component and a fuel consumption deteriorate for catalyst protection.

  In addition, since the gear ratio is changed so that the engine output does not change, torque shock or the like does not occur at the start of the catalyst protection control, and the vehicle can travel while maintaining the vehicle speed before the start of the catalyst protection control even during the catalyst protection control. it can. Therefore, the driver does not feel uncomfortable for protecting the catalyst.

  Since a predetermined waiting time is provided from when it is determined that the high exhaust temperature operation region (region A) is determined until the change of the gear ratio is started, the high exhaust temperature operation region (region A) is caused by a transient change in the operation region. In such a situation that the vehicle enters the low exhaust temperature operation region (region B) immediately after entering, the unnecessary shift can be avoided.

  When an acceleration request is detected during the catalyst protection control, the catalyst protection control by changing the transmission ratio of the CVT 2 is interrupted, and the acceleration request is satisfied while the high exhaust temperature operation region (region A) is satisfied. Since the exhaust gas temperature is lowered by increasing the injection amount, operability such as acceleration is not sacrificed for catalyst protection.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

  The present invention can be applied to deterioration prevention control of an engine exhaust gas purification catalyst.

It is the schematic of the system of this embodiment. It is a flowchart of the catalyst protection control of this embodiment. It is a driving | operation area | region map. It is a time chart of a catalyst temperature at the time of performing catalyst protection control, and an engine speed.

Explanation of symbols

1 engine 2 continuously variable transmission (CVT)
3 Catalyst 4 Control unit (C / U)
5 Intake passage 6 Intake manifold 7 Exhaust manifold 8 Exhaust passage 9 Injector 11 Propeller shaft 12 Transmission controller (AT-C / U)
13 Crank angle sensor 14 Accelerator opening sensor 15 Brake pedal force sensor

Claims (3)

In a vehicle control device that transmits engine output to wheels via a continuously variable transmission and has a catalyst device for exhaust gas purification in an exhaust passage,
An operating state detecting means for detecting the operating state of the engine;
Driving region determination means for determining a driving region based on the driving state;
When the operation region determination means determines that it is in the high exhaust temperature operation region, catalyst protection control is performed to change the speed ratio of the continuously variable transmission so that the engine output does not change and the engine output does not change. And a catalyst protection means for performing control of the vehicle.   2. The vehicle control device according to claim 1, wherein the catalyst protection unit provides a predetermined waiting time from when it is determined to be in the high exhaust temperature operation region until the change of the gear ratio is started. An acceleration request detecting means for detecting an acceleration request;
A fuel injection amount calculating means for calculating a fuel injection amount according to the acceleration request and a fuel injection amount necessary for lowering the exhaust temperature, and
3. The fuel injection amount according to claim 1, wherein when the acceleration request is detected during the catalyst protection control, the catalyst protection control is interrupted, and the fuel injection amount is set such that the exhaust temperature can be lowered while satisfying the acceleration request. The vehicle control device described.

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