JP4479110B2 - Control device and control method for automatic engine start - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention automatically stops the operation without depending on the driver's key operation when a predetermined condition is satisfied during driving, while not depending on the driver's key operation when the predetermined condition is satisfied during automatic stop. The present invention relates to a control device and a control method for automatically starting an engine (internal combustion engine) having a so-called idle stop function for automatically starting.
[0002]
[Prior art]
When starting the engine, in order to start the engine reliably, by controlling the fuel injection amount etc. so that the torque generated by the engine immediately after the start is temporarily larger than the torque during idle operation, Usually, after the engine is reliably started, the engine torque is gradually reduced to approach the torque during idle operation. By taking such a special control method at the time of start-up, the engine speed temporarily rises to a height of 1000 rpm or more and then gradually decreases to such an extent that engine stall does not occur. Settling to a few (500 to 700 rpm).
[0003]
By the way, in order to reduce emissions of harmful gases such as CO ₂ and NO _x and save fuel (improve fuel consumption), a general passenger car (AT car) with an automatic transmission (AT) has recently been developed. Even in such vehicles, attempts have been made to perform idle stop operation. However, when performing idle stop control in an AT vehicle, the shift operation load of the automatic transmission by the driver during automatic engine start is reduced. Therefore, it is necessary to start the engine automatically in a state where AT is set in the drive range that is the shift range selected by the driver during traveling.
[0004]
In the AT drive range, the crankshaft of the engine is connected to the axle of the drive wheel via a torque converter, planetary gear (planetary gear mechanism) and hydraulic clutch in the AT, and a differential gear (differential gear mechanism). It is in the state that was done. Therefore, a large engine torque that is generated when the engine is reliably started and a large torque that is greater than the axle torque that is generated during creep travel acts on the crankshaft. A so-called starting shock occurs. This starting shock makes the driver uncomfortable.
[0005]
An engine control device described in Japanese Patent Application Laid-Open No. 11-22520 is known as a prior art proposed to solve this problem. In this prior art, 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 as compared with the case where the engine is started by manual key operation. By performing engine torque reduction control, the engine is started while reducing the start shock. According to this prior art, it is possible to suppress a start shock generated when the engine is automatically started in the AT range in the AT vehicle. Therefore, if the engine can always be started reliably by this prior art. The problem of discomfort to the driver should be resolved.
[0006]
[Problems to be solved by the invention]
However, the reason for controlling the torque generated by the engine to be temporarily larger than the torque during idle operation in starting the engine by normal key operation is to ensure that such control starts the engine. Because it is necessary. When the engine is automatically started, the torque is reduced by reducing the fuel injection amount or retarding the ignition timing uniformly in accordance with the above-mentioned prior art for the purpose of reducing the shock. If the engine is started in a state, the value of the torque generated by the engine may be lower than the minimum torque required for starting the engine. In such a case, the engine is automatically started. Will end in failure.
[0007]
If the engine is started when the vehicle is parked, such as when the engine is started by a normal key operation, there will be no major safety problem even if the start fails, but the vehicle runs on the road during idle stop operation. Since the engine is automatically stopped and started even when the vehicle is temporarily stopped, for example, a vehicle that is going to turn right at an intersection with a signal waits for a vehicle on the opposite lane to pass Even when the vehicle stops temporarily at the center of the intersection, the engine stops due to the idle stop function. Therefore, it is necessary to start the engine automatically and complete the right turn by the time the next straight vehicle arrives or the signal changes after the current straight vehicle has passed, but there is no time in this way. If the engine fails to start automatically in the situation, it not only gives the driver a greater discomfort than the starting shock, but it can also cause danger directly or indirectly. .
[0008]
Therefore, according to the present invention, when the engine is automatically started in a state where the AT is set to the drive range, it is possible to reduce the start shock while ensuring the start reliability. It is an object to provide an improved control device and control method for starting.
[0009]
[Means for Solving the Problems]
In the automatic engine start accompanying idle stop operation, priority should be given to ensuring the start-up rather than avoiding the start-up shock from the order of importance. Avoidance is a problem that can be considered after certainty of starting is ensured. From such a viewpoint, the present invention provides a control device and a control method for automatic engine start described in each claim as means for solving the above-mentioned problems.
[0010]
In the invention of the control device and the control method for automatic engine start described in claims 1 and 4, when the engine coolant temperature is lower than a predetermined value, the amount of torque reduction is set according to the degree. We are taking measures to reduce it. For example, even when the engine is sufficiently warmed up, when the engine is automatically started in the AT drive range, the engine torque is reduced by 40% compared to when the key operation is started (that is, the torque reduction rate is reduced). If the cooling water temperature is lower than 70 ° C., the torque reduction rate is changed (suppressed) from 30% to 0%. Ensure certainty.
[0011]
Therefore, when the engine coolant temperature is so low that the starting reliability cannot be ensured, the torque reduction rate is set to zero and the torque reduction control is temporarily stopped to allow the start shock to occur. Startability is ensured.
[0012]
When starting the engine, cranking is started by supplying electric power from the battery to the starter (motor), and fuel injection and ignition are performed after a predetermined amount of time has elapsed and the engine has rotated a predetermined amount. It is normal to start, and when the starter is operating, the battery needs to carry hundreds of amps of current. When the battery deteriorates, the internal resistance increases, the electromotive force (battery voltage) decreases, and even when the battery charge (remaining charge) decreases, the battery voltage drop increases, so the starter As a result of the decrease in the voltage applied to the capacitor, such a large current cannot be passed. In such a case, the rotation speed of the starter also decreases compared to when the battery is fully charged. Since the engine speed is equal to the starter speed for several hundreds of milliseconds after the starter starts operating, in such a case, fuel injection and ignition are started in a state where the engine speed has not yet sufficiently increased. Will do. Therefore, the state where the amount of charge of the battery is small and the electromotive force is low is one of the states where the engine is difficult to start.
[0013]
Under such circumstances, performing control to reduce engine torque in order to reduce engine start shock is inconvenient from the viewpoint that the startability of the engine must first be considered. Is appropriate. Therefore, in the control device and the control method according to the second and fifth aspects of the present invention, when the charge amount of the battery is not more than a predetermined value, the torque reduction rate at the automatic start is reduced. Further, although related to the amount of charge of the battery, the same control is performed because the same problem occurs when the battery voltage is lowered.
[0014]
In addition, when the outside air temperature is low, a certain proportion 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 and burns. However, it is significantly lower than when the outside air temperature is high. This is also one of the states where the engine is difficult to start, and it can be said that it is inappropriate to reduce the engine torque in order to avoid the start shock in such a state. Therefore, in the invention of the control device and the control method according to the third and sixth aspects, the torque reduction rate is reduced when the outside air temperature is a predetermined value or less.
[0015]
In the above description, as vehicle state detection means, engine cooling water temperature detection means, battery charge amount (remaining charge) detection means for supplying power to the starter, battery voltage detection means, or outside air temperature An apparatus and method for providing any one of the detection means and correcting the torque reduction rate when the engine torque is automatically started based on a single signal detected by the detection means. As stated above, when two or more vehicle state detection means are provided, and any one of the detection signals falls below a predetermined value, the engine torque control means corrects the torque reduction rate. The engine torque control means may determine the torque reduction rate by comprehensively considering the signals of a plurality of detection means. It goes without saying.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
In the control device and the control method for automatic start of the engine according to the present invention, when the engine is automatically started in the AT drive range, a reduced torque is generated as compared with the torque at the start by key operation. Before the engine is automatically started with the fuel injection amount reduced or the ignition timing retarded, the vehicle is detected and automatically judged from the detection result. When it is determined that the starting certainty cannot be ensured, the degree of torque reduction is reduced or the torque reduction is stopped. Specifically, the engine torque control means used in the present invention is an idle speed control valve (ISCV) or an electronically controlled throttle valve (a throttle valve that is provided in the intake passage and whose opening is controlled by an electronic controller. ), An intake air amount control, a fuel injection amount control, and an ignition timing control.
[0017]
In a vehicle equipped with an engine in which fuel is injected into an intake pipe by a fuel injection valve such as a so-called port injection type engine, the amount of intake air that is drawn into the cylinder, that is, the flow rate of air is controlled by a throttle valve. 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 amount that increases in accordance with the opening of the throttle valve, thereby increasing the engine torque. Therefore, the engine generates a larger torque as the intake amount increases. To do. Further, even when the intake air amount is kept constant, the generated torque decreases as the fuel injection amount is gradually decreased. If the engine is warming up (cooling water temperature is about 70 ° C or higher), the engine will misfire even if the fuel injection amount is reduced to about 15: 0.6. You can continue to rotate without doing. However, in such an operation state with a lean air-fuel mixture, the engine torque is reduced by about 30% compared to the case of an air-fuel ratio of 15: 1.
[0018]
Further, since the maximum torque can be obtained in a state where the ignition timing is advanced from the compression top dead center to the crank angle by several degrees to several tens of degrees, this crank angle becomes the maximum torque advance value. Therefore, the engine torque tends to decrease as the ignition timing is delayed from the maximum torque advance value.
[0019]
Because the engine has such a property, when starting the engine in the AT drive range, the idle speed control valve and the electronically controlled throttle valve are controlled to the closed side rather than the case of starting by key operation, The engine torque can be reduced by controlling the fuel injection amount in a decreasing direction or by controlling the ignition timing to the lag side, and the shock at the time of automatic start can be kept low.
[0020]
However, even if the engine torque is reduced, at least torque is required to move or rotate pistons, crankshafts, cooling water pumps, alternators (generators), etc. that are stationary by idle stop control. The engine must generate a torque that is greater than the value of this torque required for startup. If the torque generated by the engine falls below this torque value, the engine will misfire and will not start. In the case of a vehicle on which idle stop control is performed, there is a possibility that the vehicle may get stuck at the intersection as described above and cannot start.
[0021]
In an intake pipe injection engine such as a port injection engine, when the temperature of the cooling water is very low as in winter, the temperature of the cooling water rises sufficiently even after a long warm-up operation. Therefore, 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 being vaporized to form a liquid film. As a result, the engine startability deteriorates when the coolant temperature is low such that the engine torque does not reach the target value. In a normal engine control method, the amount of fuel injection is controlled to be increased in consideration of the amount of torque reduction caused by fuel adhering to the inner wall surface of the intake pipe when the coolant temperature is low. . In any case, since the engine startability is poor in such a case, executing the control for reducing the engine torque in order to reduce the start shock in such a state reduces the engine startability. From the viewpoint of securing priority, it can be said that the control is inappropriate.
[0022]
From this point of view, the present invention has proposed the above-described solution. Therefore, the control device and the control method of the present invention will be described in more detail. First, a configuration example of a control system for engine automatic start suitable for carrying out the present invention will be described with reference to FIG. A block 1 shown in FIG. 1 is a determination means for ensuring startability, and a block 2 is a determination means for an automatic start condition. A block 3 represents engine torque control means at the time of automatic engine start. These means 1 to 3 can be configured in a single electronic control unit (ECU) as a whole, but can also be divided into a plurality of parts as required.
[0023]
The determination means 1 for ensuring startability includes a coolant temperature signal output from a coolant temperature detection means 4 such as a temperature sensor that is a vehicle state detection means, and a battery output from the battery voltage detection means 5. A voltage signal, a battery charge amount signal output from the battery charge amount detection means 6, an outside air temperature signal output from the outside air temperature detection means 7 such as a temperature sensor, and the like are input. Based on one or more of these input signals and a map or the like set in the ROM, the determination means 1 calculates a torque reduction rate necessary for ensuring startability during automatic start, and The torque is supplied to the torque control means 3.
[0024]
The automatic start condition determination means 2 generally includes a shift position signal output from a shift position detection means 8 attached to an automatic transmission (AT) and a brake depression amount such as a potentiometer attached to a brake pedal. A brake depression amount signal output from the detection means 9 is input. The determination means 2 determines the conditions for automatic start based on those signals and the map set in the ROM, etc., and when the conditions are established, the determination means 2 automatically proceeds to the engine torque control means 3 as a control signal. Send a start signal. This automatic start condition determination means 2 is the same as that mounted on a conventional vehicle having an idle stop function.
[0025]
When the engine torque control means 3 receives the engine automatic start signal from the automatic start condition determination means 2, the engine torque control means 3 reads the torque reduction rate that can ensure the startability from the determination means 1 to ensure the startability. By determining the engine torque that can be generated and the torque reduction rate for that, and controlling the fuel injection amount, ignition timing, etc., execute torque reduction control with an appropriate reduction rate, or prohibit torque reduction control Thus, in a state where the starting shock is not generated as much as possible, the control that can ensure the starting reliability in the first and first manner is performed.
[0026]
FIG. 2 shows how the determination means 1 for ensuring the startability, the automatic start condition determination means 2 and the engine torque control means 3 operate according to the coolant temperature signal detected by the coolant temperature detection means 4. It is the flowchart which concretely illustrated whether to do. Therefore, this flowchart shows the contents of the control program for the operation of the determination means 1 and 2 and the control means 3. This program has an idle stop function and is repeatedly executed every predetermined short time when an engine that rotationally drives an axle via an automatic transmission (AT) or the like automatically stops in the AT drive range. .
[0027]
In step 201 in FIG. 2, the automatic start condition determination unit 2 determines whether or not the brake stroke (depression amount) is equal to or less than a predetermined value based on a signal from the brake depression amount detection unit 9. In the case of NO, it is an indication of the driver's intention to maintain the vehicle stop, so the determination is repeated with the engine stopped. In the case of YES, since the driver's intention to start a stopped vehicle is expressed, the engine is automatically started even in the AT drive range. For this purpose, first, the routine proceeds to step 202 where the determination means 1 reads the cooling water temperature signal from the detection means 4 and calculates the reduction amount (reduction rate) of the engine torque at the start in accordance with the cooling water temperature in step 203. To the control means 3. In step 204, the control means 3 operates a starter (motor) to automatically start the engine.
[0028]
At this time, the control means 3 performs engine torque reduction control according to the reduction amount (reduction rate) input from the determination means 1 as shown in step 206. As a result, the engine starts reliably while keeping the shock at the start low, and the rotational speed gradually increases. Then, in the next step 207, it is determined whether or not the engine speed has increased to a predetermined value or more. In the case of YES, since the start-up is completed, the process proceeds to step 208 to stop the operation of the starter. However, in the case of NO, the process returns to step 206 to repeat the control and determination.
[0029]
The flowchart of FIG. 3 uses a plurality of vehicle state detection means such as a cooling water temperature detection means 4, a battery voltage detection means 5, a battery charge amount detection means 6, and an outside air temperature detection means 7, and detects them. The control method which performs determination based on the signal which a means detects is illustrated. This embodiment shows a control program in which engine torque reduction control is stopped when even one of the conditions for determining the start certainty is not satisfied. Since the contents shown in this flowchart are clear from the above description, further detailed description is omitted.
[0030]
FIG. 4 shows the reduction rate of the engine torque at the time of automatic start with respect to each of the cooling water temperature, battery voltage, battery charge amount, and outside air temperature detected by each of the detection means 4, 5, 6, and 7 described above. Specifically, the threshold value for changing from 0% to 40% (or vice versa) is illustrated. That is, the respective threshold values for changing the reduction rate are as follows: the cooling water temperature is 90 ° C., the battery voltage is 12 V, the battery charge amount (remaining amount) is 90%, and the outside air temperature is 20 ° C. These threshold values can be used as predetermined values of the determination block in the flowchart shown in FIG. 3, for example. Therefore, FIG. 4 can be set as one map in the ROM of the determination means 1 for ensuring startability.
[0031]
FIG. 5 shows a case where the reduction rate of the engine torque at the time of automatic start is further finely set and is set so that the reduction rate continuously changes within a range of 0% to 40%. 6 shows an example of the contents of a map indicating the reduction rate corresponding to each of the cooling water temperature, the battery voltage, the battery charge amount, and the outside air temperature detected by 6 and 7. This map can also be set in the ROM of the determination means 1 for ensuring startability.
[0032]
FIG. 6 shows, in the form of a time chart, the phenomenon that occurs when the engine torque at the time of starting is reduced by reducing the fuel injection amount even when the starting reliability is not ensured when the engine is automatically started. It is shown. The horizontal axis shows the elapsed time, but 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. Yes.
[0033]
As can be seen from FIG. 6, when engine torque reduction control is performed in such a state that the starting reliability is poor, the engine starts automatically even if the starter is continuously operating. No, auto-start fails.
[0034]
7 and 8 illustrate the effects of the present invention in the form of a time chart in comparison with the prior art that does not perform any torque reduction. FIG. 7 shows a case where the torque is reduced by reducing the fuel injection amount, and FIG. 8 shows a case where the torque is reduced by reducing the intake air amount using an electronically controlled throttle valve. In either case, the solid line indicates the case of the prior art in which torque reduction control is not performed at all in a state where there is no problem in startability due to the high coolant temperature and the like. Since there is no problem with startability, the engine speed increases well, but torque reduction control is not performed, so the acceleration in the front-rear direction increases, which gives the driver discomfort as a start shock .
[0035]
7 and 8 show the case of the present invention, in which the engine torque reduction control is stopped from the beginning at the time of automatic starting when it is determined that the starting reliability is poor because the cooling water temperature is low. Is shown. Therefore, as shown by the longitudinal acceleration, some start shock occurs, but since the reliability of the start is relatively low, the engine speed rises slowly without reducing the torque. Start-up shocks are not so great as to be a problem. Further, since torque is not reduced, there is no problem in starting reliability.
[0036]
The broken lines shown in FIGS. 7 and 8 are also cases where the present invention is implemented, and in this case, an example in which torque reduction control is executed within a range in which the certainty of starting is ensured is shown. By reducing torque during automatic starting, the acceleration in the front-rear direction is remarkably reduced and the problem of starting shock has been solved. Performance has been obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a system configuration for carrying out the present invention.
FIG. 2 is a flow chart illustrating one embodiment of the present invention.
FIG. 3 is a flowchart showing another embodiment of the present invention.
FIG. 4 is a diagram showing 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 finely.
FIG. 6 is a time chart showing a problem of the prior art.
FIG. 7 is a time chart for illustrating the effects of the present invention with respect to the prior art.
FIG. 8 is a time chart for illustrating the effects of the present invention with respect to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Determination means 2 for ensuring startability 2 ... Automatic start condition determination 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 detection means 8 ... shift position detection means 9 ... brake depression amount detection means 10 ... torque sensor

Claims (6)

An automatic transmission that transmits the output of the engine to the axle;
Engine automatic 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 as compared with the start by the key operation of the driver when the engine is automatically started when the automatic transmission is in the drive range by the engine automatic start means;
Cooling water temperature detecting means for detecting the temperature of the cooling water of the engine,
When the cooling water temperature detected by the cooling water temperature detecting means is not more than a predetermined value, the engine torque control means
When the cooling water temperature is larger than a predetermined value and when the engine torque reduction control is not performed at all, the engine rotational speed is lower, the cooling water temperature is larger than the predetermined value, and the engine torque reduction control. An engine automatic control device configured to suppress or stop the reduction of the torque of the engine so as to be higher than the engine speed in the case of performing. An automatic transmission that transmits the output of the engine to the axle;
Engine automatic 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 as compared with the start by the key operation of the driver when the engine is automatically started when the automatic transmission is in the drive range by the engine automatic start means;
Battery state detection means for detecting the amount of charge of the battery or the voltage of the battery,
The engine torque control means, when the charge amount of the battery or the battery voltage detected by the battery state detection means is a predetermined value or less,
When the charge amount of the battery or the voltage of the battery is greater than a predetermined value, and the engine speed is lower than when the engine torque reduction control is not performed at all, the charge amount of the battery or the voltage of the battery is predetermined. The engine torque reduction is suppressed or stopped so as to be higher than the engine speed when the engine torque reduction control is performed. Automatic engine control device. An automatic transmission that transmits the output of the engine to the axle;
Engine automatic 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 as compared with the start by the key operation of the driver when the engine is automatically started when the automatic transmission is in the drive range by the engine automatic start means;
An outside air temperature detecting means for detecting the outside air temperature of the vehicle,
The engine torque control means, when the outside air temperature detected by the outside air temperature detection means is below a predetermined value,
When the outside air temperature is larger than a predetermined value and when the engine torque reduction control is not performed at all, it is lower than the engine speed, and when the outside air temperature is larger than the predetermined value, and the engine torque reduction control. An engine automatic control device configured to suppress or stop the reduction of the torque of the engine so as to be higher than the engine speed in the case of performing. An automatic transmission for transmitting engine output to an axle is provided, and when the engine is automatically started when a predetermined condition is satisfied while the engine is stopped, compared to when starting by a key operation of a driver In an engine automatic start control method for reducing engine torque,
When the engine coolant temperature is below a predetermined value,
When the temperature of the cooling water is greater than a predetermined value, and when the engine speed is lower than when the engine torque reduction control is not performed at all, the temperature of the cooling water is higher than the predetermined value, and the engine An engine automatic control method characterized by suppressing or canceling the reduction of the torque of the engine so as to be higher than the engine speed when performing the torque reduction control . An automatic transmission for transmitting engine output to an axle is provided, and when the engine is automatically started when a predetermined condition is satisfied while the engine is stopped, compared to when starting by a key operation of a driver In an engine automatic start control method for reducing engine torque,
If the battery charge or battery voltage is below a certain value,
The battery charge amount or battery voltage is greater than a predetermined value, and is lower than the engine speed when no engine torque reduction control is performed. The battery charge amount or battery voltage is lower than a predetermined value. An automatic engine control method characterized by suppressing or canceling the reduction of the engine torque so as to be higher than the engine rotation speed in the case of large-scale engine torque reduction control . An automatic transmission for transmitting engine output to an axle is provided, and when the engine is automatically started when a predetermined condition is satisfied while the engine is stopped, compared to when starting by a key operation of a driver In an engine automatic start control method for reducing engine torque,
If the outside temperature of the vehicle is below a certain value,
When the outside air temperature is larger than a predetermined value and when the engine torque reduction control is not performed at all, it is lower than the engine speed, and when the outside air temperature is larger than the predetermined value, and the engine torque reduction control. An engine automatic control method characterized by suppressing or canceling a reduction in the torque of the engine so as to be higher than an engine speed in the case of performing.

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