JP2002242724A - Control device and control method for automatic engine start - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure certainty for starting while reducing a starting shock in an engine carrying out idle stop control. SOLUTION: In an idle stop engine, since an automatic start is carried out in a state of a crankshaft and an axle connected via an automatic transmission, the starting shock is generated, but if a reduction control of engine torque is carried out during the automatic start to prevent this, the certainty for starting drops and a probability of failure of the automatic start rises. In the control device and control method, a cooling water temperature, a battery voltage, a charge amount, an outside air temperature or the like are detected, and the reduction of a fuel injection quantity or the reduction control of torque by a retard of an ignition timing are carried out within a range of securing the certainty for starting. Accordingly, if the certainty for starting is not secured, the certainty for starting is given preference over the prevention of the starting shock by stopping the reduction control of torque or reducing a reduction rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically stopping driving without depending on a key operation of a driver when a predetermined condition is satisfied during driving, and a driver when the predetermined condition is satisfied during automatic stopping. The present invention relates to a control device and a control method for an automatic start of an engine (internal combustion engine) having a so-called idle stop function for automatically starting without depending on key operations.

[0002]

2. Description of the Related Art When starting an engine, in order to surely start the engine, the fuel injection amount or the like is set so that the torque generated by the engine immediately after the start is temporarily larger than the torque during idling operation. Usually, after the engine is reliably started by controlling, the engine torque is gradually reduced to approach the torque at the time of idling operation. By adopting such a special control method at the time of starting, the engine speed is temporarily set to 1000 rpm.
After the air blows up to a height of at least m, it gradually decreases to such a degree that engine stall does not occur, and settles to the rotational speed (500 to 700 rpm) during idling operation.

Recently, a general passenger car (AT) equipped with an automatic transmission (AT) has been developed for the purpose of reducing the emission of harmful gases such as CO ₂ and NO _X and saving fuel (improving fuel efficiency). Attempts have been made to perform idle stop operation on vehicles such as AT vehicles.
When performing idle stop control in a vehicle, in order to reduce the shift operation load of the automatic transmission by the driver at the time of automatic starting of the engine, an AT is set to a drive range which is a shift range selected by the driver during traveling.
It is necessary to start the engine automatically in a state where is set.

In the drive range of the AT, the crankshaft of the engine is driven by a torque converter, a planetary gear (planetary gear mechanism) and a hydraulic clutch in the AT, and a drive wheel through a differential gear (differential gear mechanism). It is connected to the axle. Therefore, the large engine torque that is generated when the engine is reliably started causes a large torque greater than the axle torque that is generated during creep running to act on the crankshaft. This causes a so-called starting shock. This starting shock gives the driver discomfort.

As a prior art proposed to solve this problem, there is known an engine control device described in Japanese Patent Application Laid-Open No. H11-22520. According to this conventional technique, when the engine is automatically started in a vehicle that performs an idle stop operation, the fuel injection amount is reduced or the ignition timing is retarded compared to a case where the engine is started by manual key operation. By performing the engine torque reduction control, the engine is started while the starting shock is reduced. According to this prior art, AT
Since the starting shock that occurs when the engine is automatically started while the drive range is maintained in the car can be reduced, if the engine is always started reliably by this conventional technique, it may cause discomfort to the driver. Should also be resolved.

[0006]

However, the reason for controlling the torque generated by the engine to be temporarily larger than the torque at the time of the idling operation when the engine is started by a normal key operation is that such control is performed. Is necessary to reliably start the engine. When the engine is started automatically, the torque is reduced by uniformly reducing the fuel injection amount or retarding the ignition timing in accordance with the above-described conventional technology with the aim of reducing the shock. If the engine is started in this state, the value of the torque generated by the engine may be lower than the minimum torque required at the time of starting the engine, and in such a case, the engine is automatically started. Will fail.

[0007] As in the case of starting the engine while the vehicle is parked, as in the case of starting the engine by normal key operation, even if the start fails, there is no major safety problem. The engine is automatically stopped and started even when the vehicle is temporarily stopped when traveling on a road.For example, a vehicle trying to make a right turn at an intersection with a traffic light passes through a straight ahead vehicle in the oncoming lane. Even if you stop temporarily at the center of the intersection to wait for the engine, the engine will be stopped by the idle stop function. Therefore, it is necessary to start the engine automatically and complete a right turn by the time the next straight-ahead vehicle arrives or the signal changes, after the straight-ahead vehicle has passed, but there is no time in this way If the engine fails to start automatically in the situation, it could not only cause the driver greater discomfort than a starting shock, but it could also directly or indirectly cause danger. .

Accordingly, the present invention is intended to reduce the starting shock while ensuring the starting reliability when the engine is automatically started in the state where the AT is set to the drive range. It is an object to provide an improved control device and control method for automatic starting of an engine.

[0009]

In the automatic start of the engine accompanying the idling stop operation, priority is given to ensuring the start of the engine rather than avoiding the start shock in terms of importance. Avoiding the starting shock is a problem that can be considered after the starting reliability is ensured. From this perspective,
The present invention provides, as means for solving the above problems, a control device and a control method for automatic starting of an engine described in the claims.

In the control device and control method for automatically starting the engine according to the first and fourth aspects, when the temperature of the cooling water of the engine is lower than a predetermined value, the torque of the engine is reduced in accordance with the degree. Measures have been taken to reduce the reduction. For example, even when the engine is sufficiently warmed up, when automatically starting the engine in the AT drive range, the engine torque is reduced by 40% compared to the time of starting by key operation (that is, the torque reduction rate is reduced). If the cooling water temperature is low and is 70 ° C. or less,
By changing (suppressing) the torque reduction rate from 30% to 0%, the reliability of starting is ensured.

Therefore, when the cooling water temperature of the engine is so low that the certainty of starting cannot be ensured, the torque reduction rate is set to zero and the torque reduction control is temporarily stopped.
Even if a start shock is allowed, the startability is ensured.

When the engine is started, cranking is started by supplying electric power from a battery to a starter (motor), and after a lapse of several hundred milliseconds and the engine has rotated a predetermined amount, fuel injection is started. When the starter is activated, the battery needs to carry a large current of several hundred amps. When the battery deteriorates, the internal resistance increases and the electromotive force (battery voltage) decreases, and even when the battery charge (remaining charge) decreases, the battery voltage drops significantly. As a result, it becomes impossible to flow such a large current. In such a case, the rotation speed of the starter is also lower than when the battery is fully charged. During a few hundred milliseconds after the starter starts operating, the engine speed is equal to the starter speed. In such a case, fuel injection and ignition are started in a state where the engine speed has not yet risen sufficiently. Will do. Therefore,
The state where the charge amount of the battery is small and the electromotive force is low is one of the states where the engine is difficult to start.

In such a situation, performing control to reduce the engine torque in order to reduce the engine starting shock is necessary from the viewpoint that the engine startability must be ensured first. Inappropriate to look at. Therefore, in the invention of the control device and the control method according to the second and fifth aspects, when the charge amount of the battery is equal to or less than a predetermined value, the torque reduction rate at the time of automatic start is reduced. Further, although related to the amount of charge of the battery, a similar problem occurs when the battery voltage is low. Therefore, similar control is performed.

When the outside air temperature is low, a certain portion of the fuel injected from the fuel injection valve into the intake pipe adheres to the inner wall surface of the intake pipe, so that it is immediately vaporized and flows into the cylinder. The burning rate is significantly lower than when the outside air temperature is high. This is also one of the states in which the engine is difficult to start, and in such a state, it is inappropriate to reduce the engine torque in order to avoid a start shock. Therefore, Claims 3 and 6
In the invention of the control device and the control method described in
When the outside air temperature is equal to or lower than a predetermined value, the torque reduction rate is reduced.

In the above description, as the vehicle state detecting means, means for detecting the temperature of the cooling water of the engine, means for detecting the amount of charge (remaining charge) of the battery for supplying power to the starter, means for detecting the battery voltage, Alternatively, a device in which any of the outside air temperature detection means is provided, and the engine torque control means corrects and controls the torque reduction rate at the time of automatic starting of the engine based on a single signal detected by those detection means. And a method are described, but two or more of these vehicle state detection means are provided, and when any one of the detection signals becomes a predetermined value or less,
The control means for the engine torque may be set so as to correct and control the reduction rate of the torque, or the control means for the engine torque may determine the reduction rate of the torque in consideration of the signals of the plurality of detection means. Needless to say, this may be done.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the control apparatus and control method for automatically starting an engine according to the present invention, when the engine is automatically started in the AT drive range, the torque is reduced as compared with the torque at the time of starting by key operation. Before the engine is automatically started with the fuel injection amount reduced or the ignition timing retarded so that the generated torque is generated, the state where the vehicle is placed is detected and the detection is performed. When it is determined automatically from the results that it is not possible to ensure the reliability of starting, the degree of torque reduction is reduced or the torque reduction is stopped. The control means of the engine torque used in the present invention is, specifically, an idle speed control valve (ISCV) or an electronically controlled throttle valve (a throttle valve provided in an intake passage and having an opening controlled by an electronic control device). ), Controls the amount of fuel injection, controls the amount of fuel injection, and controls the ignition timing.

In a vehicle equipped with an engine such as a so-called port injection type engine in which fuel is injected into an intake pipe by a fuel injection valve, the amount of intake air taken into a cylinder by a throttle valve, that is, the flow rate of air Is controlled, and an amount of fuel proportional to the intake amount is injected from the fuel injection valve into the intake port. The mass ratio of air to fuel (ie, air-fuel ratio) is about 15: 1. Therefore, the fuel injection amount also increases so as to follow the intake air amount that increases in accordance with the opening degree of the throttle valve, thereby increasing the engine torque. As the intake air amount increases, the engine generates a larger torque. I do. Even when the intake air amount is kept constant, the generated torque decreases as the fuel injection amount is gradually reduced. If the engine has been warmed up (the temperature of the cooling water is about 70 ° C. or higher), the engine will misfire even if the fuel injection amount is reduced to about 15: 0.6 by mass of air and fuel. You can continue to rotate without doing. However, in the operating state using such a lean mixture, the engine torque is reduced by about 30% as compared with the case of the air-fuel ratio of 15: 1.

Further, since the maximum torque is obtained in a state where the ignition timing is advanced from several degrees to several tens degrees from the compression top dead center to the crank angle, this crank angle becomes the maximum torque advance value. Therefore, the more the ignition timing is delayed from the maximum torque advance value, the more the engine torque tends to be reduced.

Since the engine has such properties,
When starting the engine in the AT drive range, the idle speed control valve or the electronically controlled throttle valve is controlled to the closed side, or the fuel injection amount is controlled to be reduced as compared with the case of starting by key operation. By controlling the ignition timing to the delay side, the engine torque can be reduced, and the shock at the time of automatic start can be suppressed low.

However, even if the engine torque is reduced, at least a torque for moving or rotating the piston, crankshaft, cooling water pump, alternator (generator), etc., which are stationary by the idle stop control, is necessary. Therefore, a torque larger than the value of the torque required for starting must be generated by the engine. If the torque generated by the engine falls below this value, the engine will misfire and will not start. In the case of a vehicle on which the idle stop control is performed, there is a possibility that the vehicle may get stuck in an intersection and cannot start, as described above.

In the case of an intake pipe injection engine such as a port injection engine, when the temperature of the cooling water is extremely low, as in winter, the temperature of the cooling water can be maintained even after a long warm-up operation. Since the fuel does not rise sufficiently, a considerable portion of the fuel injected from the fuel injection valve into the intake pipe adheres to the inner wall surface of the intake pipe without vaporizing to form a liquid film. As a result, when the coolant temperature is low, such as when the engine torque does not reach the target value, the startability of the engine deteriorates. In a normal engine control method, the fuel injection amount is controlled so as to increase and correct the fuel injection amount in consideration of the decrease amount of the torque caused by the fuel adhering to the inner wall surface of the intake pipe when the coolant temperature is low. . In any case, since the startability of the engine is poor in such a case, executing the control to reduce the engine torque in order to reduce the start shock in such a state will reduce the startability of the engine. From the viewpoint of securing priority, it can be said that the control is inappropriate.

From such a viewpoint, the present invention has proposed the above-mentioned solution. Therefore, the control device and control method of the present invention will be described in more detail. First,
A configuration example of a control system for automatic starting of an engine suitable for carrying out the present invention will be described with reference to FIG.
Block 1 shown in FIG. 1 is a determination unit for securing startability, and block 2 is a determination unit for automatic start conditions. Block 3 shows control means of the engine torque at the time of automatic engine start. These means 1-3
Can be configured in a single electronic control unit (ECU) as a whole, but can be divided into a plurality of parts as necessary.

The judging means 1 for securing startability includes:
A cooling water temperature signal output by a cooling water temperature detecting means 4 such as a temperature sensor as a vehicle state detecting means, a battery voltage signal output by a battery voltage detecting means 5, and a battery charge amount detecting means 6 output. A battery charge signal and an outside air temperature detecting means 7 also like a temperature sensor
Is output. The judging means 1 calculates a torque reduction rate required to secure startability at the time of automatic starting based on one or more of those input signals and a map or the like set in a ROM. The torque is supplied to the control means 3.

The automatic start condition determining means 2 includes a shift position signal output from a shift position detecting means 8 generally provided in an automatic transmission (AT), and a brake signal such as a potentiometer attached to a brake pedal. The brake depression amount signal output by the depression amount detection means 9 is input. The judging means 2 judges conditions for performing automatic starting based on these signals and a map or the like set in the ROM. Send start signal. The automatic start condition determination means 2 is the same as that mounted on a vehicle having a conventional idle stop function.

When the engine torque control means 3 receives an automatic engine start signal from the automatic start condition determination means 2, the engine torque control means 3 reads the torque reduction rate capable of ensuring the startability from the determination means 1 and secures the startability. By determining the engine torque that can be performed and the reduction rate of the torque for that, and controlling the fuel injection amount, the ignition timing, and the like, the torque reduction control with the appropriate reduction rate is performed, or the torque reduction is performed. The control is prohibited, and the control that can ensure the reliability of the start is performed primarily in a state where the start shock is not generated as much as possible.

FIG. 2 shows which of the judging means 1 for ensuring the startability, the judging means 2 for the automatic starting condition, and the engine torque control means 3 based on the cooling water temperature signal detected by the cooling water temperature detecting means 4. 7 is a flowchart specifically illustrating how the operation is performed. Therefore, this flowchart shows the contents of a control program for operating the determination means 1 and 2 and the control means 3. This program has an idle stop function, and when an engine that rotationally drives an axle via an automatic transmission (AT) or the like automatically stops in an AT drive range,
It is repeatedly executed every predetermined short time.

In step 201 of FIG. 2, the automatic starting condition determining means 2 includes a brake depression amount detecting means 9.
, It is determined whether or not the brake stroke (the amount of depression) is equal to or less than a predetermined value. In the case of NO, it means that the driver wants to keep the vehicle stopped. Therefore, the determination is repeated while the engine is stopped.
If YES, it means that the driver wants to start the stopped vehicle, so the engine is automatically started even in the AT drive range. For this purpose, first, the process proceeds to step 202, where the judging means 1 reads the temperature signal of the cooling water from the detecting means 4, and
In step (1), the amount of reduction (reduction rate) of the engine torque at the start according to the cooling water temperature is calculated and input to the control means 3. The control means 3 operates the starter (motor) in step 204 to automatically start the engine.

At this time, the control means 3 controls the reduction of the engine torque in accordance with the reduction amount (reduction rate) input from the determination means 1, as shown as step 206.
As a result, the engine is reliably started while the start-up shock is kept low, and the rotation speed gradually increases. Then, it is determined in the next step 207 whether or not the engine speed has increased to a predetermined value or more. In the case of YES, the start has been completed, so the operation proceeds to step 208 to stop the operation of the starter.
Returning to step 06, control and determination are repeated.

The flowchart of FIG. 3 is based on a plurality of vehicle state detecting means such as a cooling water temperature detecting means 4, a battery voltage detecting means 5, a battery charge detecting means 6, and an outside air temperature detecting means 7. An example of a control method for making a determination based on signals detected by those detection means is shown.
This embodiment shows a control program for stopping the engine torque reduction control when at least one condition for determining the reliability of the start is not satisfied. Since the contents shown in this flowchart are clear from the above description, further detailed description will be omitted.

FIG. 4 shows each of the aforementioned detecting means 4, 5, 6, 7
For each of the cooling water temperature, the battery voltage, the battery charge amount, and the outside air temperature detected by the above, the reduction rate of the engine torque at the time of automatic start is specifically 0% to 40%.
FIG. 7 illustrates a threshold value for changing to (or in the opposite direction). That is, the respective thresholds for changing the reduction rate are as follows: the cooling water temperature is 90 ° C.,
2V, the battery charge (remaining amount) is 90%, and the outside air temperature is 20 ° C. These thresholds can be used, for example, as predetermined values of the determination block in the flowchart shown in FIG. Therefore, FIG. 4 can be set as one map in the ROM of the determination means 1 for ensuring the startability.

FIG. 5 shows the above-described detection means 4 when the reduction rate of the engine torque at the time of automatic start is set to be more finely set so as to continuously change within the range of 0% to 40%. , 5, 6, and 7 illustrate examples of the contents of a map indicating a reduction rate corresponding to each of the cooling water temperature, the battery voltage, the battery charge amount, and the outside air temperature, which are detected. This map can also be set in the ROM of the determination means 1 for ensuring startability.

FIG. 6 is a time chart showing a phenomenon that occurs when the engine torque is reduced by reducing the fuel injection amount when the engine is automatically started, although the reliability of the start is not ensured. It is shown in the form of The horizontal axis shows the elapsed time, while the vertical axis shows the engine speed, the acceleration in the front-rear direction, the fuel injection amount reduced from the start by key operation, and the starter operation signal in order from the top. I have.

As is apparent from FIG. 6, when the engine torque reduction control is performed in such a state that the starting reliability is poor, even if the starter is continuously operated,
The engine will not start automatically and the automatic start will fail.

FIGS. 7 and 8 show the operation and effect of the present invention in comparison with the prior art in which the torque is not reduced at all.
This is illustrated in the form of a time chart. FIG. 7 shows the case where the torque is reduced by reducing the fuel injection amount, and FIG. 8 shows the case where the torque is reduced by reducing the intake amount using an electronically controlled throttle valve. In each case, the solid line shows the case of the related art in which the torque reduction control is not performed at all in a state where there is no problem in the startability due to a high cooling water temperature and the like. Since there is no problem in startability, the engine speed is good, but the acceleration in the front-rear direction is large because the torque reduction control is not performed, which gives the driver discomfort as a start shock. .

The dashed line shown in FIGS. 7 and 8 is a case according to the present invention, and it is determined that the reliability of the start is poor because the temperature of the cooling water is low. The example which stopped was shown. Therefore,
Although some starting shocks occur as indicated by the acceleration in the front-rear direction, the engine rotation speed rises slowly even without reducing the torque because the certainty of starting is relatively low. Also doesn't get big enough to be a problem. Further, since the torque is not reduced, there is no problem in the reliability of the start.

The broken lines shown in FIGS. 7 and 8 are also examples in which the present invention is implemented, and in this case, show an example in which the torque reduction control is executed within a range in which the starting reliability is secured.
By reducing the torque at the time of automatic starting, the acceleration in the front-rear direction has become extremely small, and the problem of starting shock has been resolved. Performance has been obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration for implementing the present invention.

FIG. 2 is a flowchart illustrating one embodiment of the present invention.

FIG. 3 is a flowchart showing another embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a threshold value for torque reduction control determined for each detected signal.

FIG. 5 is a diagram showing an example in which threshold values are set continuously and finely.

FIG. 6 is a time chart showing a problem of the related art.

FIG. 7 is a time chart showing the operation and effect of the present invention with respect to a conventional technique.

FIG. 8 is a time chart showing the operation and effect of the present invention with respect to the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Judgment means for ensuring startability 2 ... Automatic start condition judgment means 3 ... Engine torque control means 4 ... Cooling water temperature detection means 5 ... Battery voltage detection means 6 ... Battery charge amount detection means 7 ... Outside air Temperature detecting means 8 ... Shift position detecting means 9 ... Brake depression amount detecting means 10 ... Torque sensor

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F02D 41/04 330 F02D 41/04 330N 41/06 330 41/06 330B F-term (Reference) 3G093 AA01 BA02 BA09 BA21 CA01 DA05 DA12 DB09 DB11 DB15 DB19 EA05 EA13 EC01 FA04 FA08 FB02 3G301 HA01 JA04 KA01 LB01 LC01 MA11 NA08 NC02 ND04 ND07 NE06 PA10Z PE08Z PF05Z PF07Z PF16Z PG01Z

Claims (6)

[Claims] An automatic transmission for transmitting an output of an engine to an axle; an automatic engine start control means for automatically starting the engine when a predetermined condition is satisfied while the engine is stopped; An engine torque control unit configured to reduce a torque of the engine when starting the engine automatically when the automatic transmission is in a drive range by a start unit, compared with a start by a key operation of a driver; and cooling the engine. Cooling water temperature detecting means for detecting the temperature of the water, the engine torque control means, when the cooling water temperature detected by the cooling water temperature detecting means is a predetermined value or less,
An automatic engine control device configured to suppress or stop reduction of the engine torque. 2. An automatic transmission for transmitting the output of an engine to an axle; an automatic engine start control means for automatically starting the engine when a predetermined condition is satisfied while the engine is stopped; Engine torque control means for reducing the torque of the engine when starting the engine automatically when the automatic transmission is in a drive range by a starting means, compared to starting the engine by a key operation of a driver; Alternatively, there is provided a battery state detecting means for detecting a voltage of the battery, wherein the engine torque control means is provided when the charge amount of the battery or the voltage of the battery detected by the battery state detecting means is equal to or less than a predetermined value. , Configured to suppress or halt the reduction in engine torque. Automatic engine control apparatus characterized by there. 3. An automatic transmission for transmitting an output of an engine to an axle; an automatic engine start control means for automatically starting the engine when a predetermined condition is satisfied while the engine is stopped; Engine torque control means for reducing the torque of the engine when starting the engine automatically when the automatic transmission is in a drive range by a starting means, compared with starting the engine by a key operation of a driver; The engine torque control means suppresses a decrease in torque of the engine when the outside air temperature detected by the outside air temperature detection means is equal to or lower than a predetermined value. Or an automatic engine control device configured to stop the engine. 4. An automatic transmission for transmitting an output of an engine to an axle is provided. When a predetermined condition is satisfied while the engine is stopped and the engine is automatically started, a key operation by a driver is performed. In the engine automatic start control method for reducing the torque of the engine as compared to the time of starting, when the temperature of the cooling water of the engine is equal to or lower than a predetermined value,
An automatic engine control method, characterized in that a reduction in the torque of the engine is suppressed or stopped. 5. An automatic transmission for transmitting the output of an engine to an axle is provided. When a predetermined condition is satisfied while the engine is stopped and the engine is automatically started, a key operation by a driver is performed. In the automatic engine start control method for reducing the engine torque as compared to the time of starting according to (1), when the charge amount of the battery or the voltage of the battery is equal to or lower than a predetermined value, the reduction of the engine torque is suppressed or stopped. An automatic engine control method characterized in that: 6. An automatic transmission for transmitting the output of the engine to the axle is provided, and when a predetermined condition is satisfied while the engine is stopped and the engine is automatically started, a key operation by a driver is performed. An automatic engine start control method for reducing the torque of an engine as compared to the time of starting according to (1), wherein when the outside air temperature of the vehicle is equal to or lower than a predetermined value, the reduction of the engine torque is suppressed or stopped. Engine automatic control method.