JP3714078B2 - Automatic engine start control device for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicular engine automatic start control device that is applied to an idle stop vehicle that automatically stops an engine during idling of the engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an idle stop vehicle has been developed and proposed in which an engine is automatically stopped during auto idling to suppress fuel consumption and improve fuel efficiency.
In such an idle stop vehicle, the driver's intention to stop is generally determined based on clutch operation information, shift operation information, accelerator operation information, vehicle speed information, etc., and the engine is automatically stopped or automatically restarted (auto start). It is.
[0003]
[Problems to be solved by the invention]
However, in such a conventional idle stop vehicle, if there is a risk of harming the comfort of the vehicle due to the engine stop after the automatic stop of the engine, only a warning sound is issued to alert the driver to the engine restart. Thus, there has been a problem that the engine will not restart unless the driver performs an operation to restart the engine (such as a clutch depression operation).
[0004]
The present invention was devised in view of such a problem, and the vehicle engine automatic start control device is configured to forcibly restart the engine when there is a possibility that the vehicle comfort may be impaired. The purpose is to provide.
[0005]
[Means for Solving the Problems]
BookIn the vehicular engine automatic start control device of the invention, when the engine is automatically stopped, the basic engine start condition for determining the driver's intention to start the vehicle and the pressure of the fuel supplied to the engine fall below a predetermined value. When either one of the forced start conditions for forcibly starting the engine is satisfied, the engine is started.Here, the engine is a direct injection gasoline engine capable of directly injecting fuel into the cylinder, and is configured to inject fuel at a high pressure into the cylinder in the compression stroke at the time of start-up. The engine can be forcibly started before entering a state where it cannot be started, so that the startability of the engine can be ensured and good start response can be maintained.
  Also,By providing such a forced start condition, it is possible to reliably prevent a decrease in vehicle comfort due to engine stoppage.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a vehicle engine automatic start control apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram focusing on its function, and FIGS. 2 and 3A, 3B. Are diagrams for explaining the characteristics, and FIG. 4 is a flowchart for briefly explaining the operation.
[0008]
The vehicle to which the present invention is applied automatically stops the engine when a predetermined condition (automatic stop condition) is satisfied during idling of the engine, and when the predetermined condition (automatic start condition) is satisfied after the engine is automatically stopped. This is a so-called idle stop vehicle having a function of restarting, and as shown in FIG. 1, an engine control means (ECU) 1 is provided with an engine automatic stop means 2 and an engine restart means 3. .
[0009]
The engine restart unit 3 includes a normal restart unit 3a, a forced restart unit 3b, and a forced restart prohibiting unit 3c. These normal restart means 3a, forced restart means 3b, and forced restart prohibiting means 3c include normal restart conditions (or basic start conditions), forced restart conditions (or forced start conditions), and forced restart, respectively. If a start prohibition condition (or a restart prohibition condition) is set and the normal restart condition is satisfied or the forced restart condition is satisfied in a state where the forced restart prohibition condition is not satisfied, the engine Will restart.
[0010]
  For this reason, the ECU 1 includes a vehicle speed sensor 10 for detecting the vehicle speed V of the vehicle, an accelerator sensor 11 for detecting depression of the accelerator pedal, a shift position sensor 12 for detecting a gear position including the neutral of the transmission, and a clutch pedal. A clutch switch 13 that detects the depression of the engine, an engine speed sensor 14 that detects the engine speed Ne, a water temperature sensor 15 that detects the temperature Tw of the cooling water, an air conditioner ECU 16 that controls the operating state of the compressor of the air conditioner, A light switch 17 that detects lighting of a vehicle light, a current sensor 18 that detects an electrical load of the vehicle, a temperature sensor 19a that detects an outside air temperature Ta, an intake air temperature sensor 19b that detects an intake air temperature Tin, and a catalyst Catalyst temperature sensor 19c for detecting temperature Tc and fuel injection pressure Pf That the fuel pressure sensor 20, the brake systemBrake boosterA negative pressure sensor 21 for detecting negative pressure, an ignition key sensor 22 for detecting on / off of the ignition key, and a main switch 23 for turning on / off the entire idle stop function are connected.
[0011]
The main switch 23 is an on / off switch provided on the instrument panel, for example, and can be canceled manually by the driver after the ignition key is turned on, so that the entire idle stop function can be canceled.
Then, the engine automatic stop means 2 and the engine restart means 3 of the ECU 1 set the engine stop control signal and the engine restart signal based on the information from the sensors 10 to 23, and the fuel injection control means 30 and The data is output to the starter 31.
[0012]
Next, the basic logic of automatic engine stop (auto start) and automatic start (auto start) will be described. First, in the ECU 1, whenever the ignition key is turned on, the main switch 23 is always turned on to set an idle stop standby state in which the engine can be automatically stopped and restarted. This idle stop standby state is the most basic condition for performing automatic stop and automatic start, and both the automatic stop condition and the automatic start condition of the engine described below may be the idle stop standby state. It is a premise.
(1) Engine automatic stop condition
Various conditions as described later are set in the engine automatic stop means 2, but in the present embodiment, in particular, the automatic stop basic condition and the automatic stop permission condition can be roughly divided into two, When both of these basic conditions for automatic stop and automatic stop permission condition are satisfied, the engine automatic stop means 2 issues an engine stop signal to the fuel injection control means 30 to stop the engine.
[0013]
  Among these, the automatic stop basic condition is used to determine the driver's intention to stop the vehicle. When all of the following conditions (1) to (4) are satisfied, it is determined that the automatic stop basic condition is satisfied. Yes.
(1) No vehicle speed (Vehicle speed V = 0km / h)
(2) Shift position is neutral
(3) The clutch is fully connected (the feet are released)
(4) Idling state
  The automatic stop permission condition is provided to determine whether the vehicle is in a state that does not impair comfort and safety, and all of the following (1) to (9) are satisfied. In this case, it is determined that the automatic stop permission condition is satisfied.
(1) Elapsed time (10 sec) after the previous restart (auto start): Eliminate discomfort
(2) Completion of warm-up operation (water temperature Tw ≧ predetermined value T₁) ： Ensuring quick startability
(3) Air conditioner compressor non-operation: Ensure air conditioning function
(4) Headlight off: ensuring illuminance
(5) Electric load below specified value: Battery protection
(6)Brake boosterNegative pressure over a predetermined value (differential pressure over the atmospheric pressure over a predetermined value): secure braking force
(7) Preset water temperature T_ThreeBelow or below the intake air temperature prescribed: Avoiding self-ignition and ensuring quick startability
(8) Catalyst temperature not less than a predetermined value (catalyst temperature Tc ≧ predetermined value Tc)₁): Ensuring catalyst activation
(9) Outside air temperature below a predetermined value (outside air temperature Ta ≦ predetermined value Ta₁ ) Heater inactive: Air conditioning function ensured
  The above (1) is for the driver to feel uncomfortable when the engine is automatically stopped immediately after the engine is restarted. Considering the driver's feeling, a predetermined time (for example, 10 seconds) has elapsed since the previous restart. The automatic stop is prohibited.
[0014]
The condition (2) is provided so that the engine can be restarted quickly and reliably at the time of restart. In the case of a direct injection gasoline engine, the condition is provided so that the engine can be quickly started by a compression stroke. Also, (3) is a condition provided mainly to ensure the air conditioning function, and is intended not to automatically stop during operation of the air conditioner compressor. In other words, it is a condition that “the vehicle interior is sufficiently cooled and it is not necessary to operate the air conditioner compressor”.
[0015]
Here, the operating state of the air conditioner compressor can be obtained from an air conditioner ECU 16 (not shown). The air conditioner ECU 16 is connected to a temperature sensor that detects the temperatures upstream and downstream of the evaporator. The air conditioner ECU 16 controls the operation of the compressor based on information from these temperature sensors. . In the ECU 1, based on the temperature information of the evaporator obtained through the air conditioner ECU 16, for example, the refrigerant temperature downstream of the evaporator ≦ predetermined value T_ev1And the refrigerant temperature upstream of the evaporator ≦ predetermined value T_ev2(However, T_ev1<T_ev2), It is determined that the air conditioner compressor does not operate. The operation of the air conditioner compressor may be directly detected, and the engine may not be automatically stopped simply by turning on the air conditioner compressor.
[0016]
(4) is provided to ensure the illuminance of the headlight. That is, when the engine is automatically stopped when the headlight is turned on, the headlight is turned on by the power of the battery. However, when the engine is stopped and the power is taken out from the battery, the illuminance gradually decreases. Therefore, in order to avoid such a situation, the engine is not automatically stopped when the headlight is turned on.
[0017]
(5) is provided for the purpose of protecting the battery and preventing the battery from running out. That is, the ECU 1 calculates the current consumption value (instantaneous maximum current consumption value) I and the battery integrated current consumption value ΣI based on the information from the current sensor 18. For example, the current consumption value I <predetermined value I₁When x5 sec and the battery integrated consumption current value ΣI <predetermined value, it is determined that the electric load is equal to or less than the predetermined value. Note that the battery voltage may be used for this determination.
[0018]
  (6) is a condition provided to ensure braking force. That is, when the differential pressure between the detection information from the negative pressure sensor 21 and the atmospheric pressure is equal to or less than a predetermined value,Brake boosterIt is conceivable that the internal negative pressure becomes insufficient and sufficient braking force cannot be secured after the engine stops. Therefore, considering the safety of the vehicleBrake boosterThe automatic stop is not permitted when the differential pressure between the negative pressure and the atmospheric pressure is equal to or less than a predetermined value.
[0019]
(7) is a condition provided for quick and reliable restart. That is, when the engine coolant temperature exceeds a predetermined temperature or the intake air temperature exceeds a predetermined temperature, it is conceivable that the fuel self-ignites before the spark plug sparks when the engine is started. In particular, at the time of restart, fuel is injected into high-temperature and high-pressure air, and self-ignition tends to occur. Since such self-ignition occurs before the compression top dead center, a torque that reversely rotates the engine may be generated when the engine is started, which causes deterioration of startability. For this reason, the above condition (7) is set, and when the water temperature is high or the intake air temperature is high, it is set not to automatically stop in consideration of the startability at the time of restart.
[0020]
Fig. 2 shows the test results for setting the area where automatic stop is prohibited. The ○, ●, △, and □ shown in the figure indicate the intake air temperature in various driving patterns that are likely to be encountered in general driving. It is a plot of the relationship between water temperature and water temperature.
And from this test result, the water temperature T_ThreeIt was possible to obtain a conclusion that self-ignition at the time of restart can be avoided if it is in the region below and below the predetermined value of the intake air temperature.
[0021]
(8) is a condition provided for the purpose of ensuring the activation of the catalyst, and the catalyst temperature is the activation temperature Tc.₁This is the condition for automatic stop. That is, the catalyst temperature is the activation temperature Tc.₁If the temperature is lower, the next time the engine is started, the catalyst is in an inactive state, and the purification capacity is low or absent.Hazardous substances discharged from the engine are discharged into the atmosphere without being purified by the catalyst. The Rukoto. This condition is provided to prevent such a situation. As a method for detecting the catalyst temperature, measurement using a high temperature sensor or estimation based on the engine temperature may be used. When a high temperature sensor is used, the temperature of the catalyst is measured by being directly attached to the catalyst or in the vicinity of the catalyst. In the case of the estimation based on the engine temperature, the catalyst temperature may be estimated from the engine water temperature or the oil temperature by utilizing the fact that the catalyst temperature after the engine stops has a correlation with the engine water temperature or the oil temperature.
(9) is a condition set for the purpose of ensuring the comfort in the passenger compartment (to ensure the performance of the heater).
[0022]
As described above, only when all of the automatic stop basic conditions (1) to (4) are satisfied and all of the automatic stop permission conditions (1) to (9) are satisfied, the ECU 1 An operation stop signal is output to the fuel injection control means 30 to automatically stop the engine.
(2) Engine restart conditions
Next, the engine restart condition of the present invention will be described. As described above, the engine restart means includes the normal restart means 3a, the forced restart means 3b, and the forced restart prohibiting means 3c.
[0023]
First, the normal restart unit 3a will be described. The normal restart unit 3a is set with the following conditions (1) and (2) as conditions for determining the driver's intention to start the vehicle. When these two conditions are both satisfied, it is determined that the normal restart condition is satisfied.
(1) The shift position is neutral.
(2) The clutch has been depressed a predetermined amount (clutch switch off).
[0024]
  The above (1) is an absolute precondition when the engine is restarted, and is a minimum condition necessary for ensuring the safety of the vehicle. Further, (2) is for determining that the driver has an intention to start when the driver operates the clutch, and reflecting the driver's intention in the control.
  Next, the forced restart means 3b will be described. The following conditions (1) to (10) are set in the forced restart means 3b. Here, the forced restart means 3b forcibly restarts the engine to ensure the safety and comfort of the vehicle even when the driver's intention to start is not determined by the normal restart means 3a. Assuming that the shift position is neutral, if any one of the following conditions (1) to (10) is satisfied, it is determined that the forced start condition is satisfied. The engine is restarted.
(1) Vehicle speed generation: ensuring braking force, ensuring vehicle functions
(2) The water temperature is below the specified value (water temperature Tw ≦ T₂, T₂<T₁) ： Ensuring quick startability
(3) The air conditioner compressor needs to be activated (when the room temperature rises and the air conditioner compressor needs to be activated): Securing the air conditioning function
(4) Headlight on: secure illuminance
(5) Electric load greater than or equal to a predetermined value (maximum instantaneous current consumption value I ≧ predetermined value I₁× 5 sec or battery integrated consumption current value ΣI ≧ predetermined value): Battery protection
(6)Brake boosterNegative pressure below a predetermined value (differential pressure from atmospheric pressure is below a predetermined value): Ensure braking force
(7) Water temperature is above a predetermined value or intake air temperature is above a predetermined value (water temperature Tw ≧ predetermined value T_Three, Intake air temperature Tin ≧ predetermined value): ensuring startability
(8) Catalyst temperature not higher than predetermined (catalyst temperature Tc ≦ predetermined value Tc₁): Ensuring catalyst activation temperature
(9) The outside air temperature is below a predetermined value (Ta ≦ Ta₁) When the heater is activated: Ensure air conditioning
(10) Fuel pressure is below a specified value: ensuring quick startability
  Of these, the condition (1) considers the safety of the vehicle, and regardless of the driver's intention, if the vehicle speed is generated, the engine is started quickly and the brake is depressed.Brake boosterThis is a condition for securing a braking force as a state in which negative pressure is applied.
[0025]
  The conditions (2) to (9) are provided for the same reason as the conditions (2) to (9) in the automatic stop permission condition described above. The condition of (3) is specifically the refrigerant temperature downstream of the evaporator ≧ predetermined value T_ev3(T_ev3> T_ev1) Or the refrigerant temperature upstream of the evaporator> T_ev4(T_ev4> T_ev2). (6)Brake boosterThe predetermined value of the negative pressure is set as a value that can sufficiently secure the braking force when the engine is stopped.
[0026]
In addition, when determining the condition of the catalyst temperature below the predetermined value in (8), as a method for detecting the catalyst temperature, in addition to the method under the automatic stop permission condition, the catalyst temperature after the engine stop correlates with the time after the engine stop is executed. By utilizing the fact, the catalyst temperature may be obtained from the time after the engine is stopped. Specifically, when a predetermined time or more elapses after the engine is stopped, the catalyst temperature Tc becomes a predetermined value Tc.₁ It may be determined that the following has been satisfied, and it may be determined that the forced start condition is satisfied.
[0027]
The condition (10) is particularly effective when the engine is a direct-injection gasoline engine, and is a condition for forcibly starting the engine before it falls into a state where the engine cannot be started by compression stroke injection. It is. In other words, in a normal multipoint injection engine (MPI engine), in the cylinder that first reaches the compression stroke at the start, the air-fuel mixture cannot be sucked, and it is necessary to wait for ignition until the next compression stroke. The internal injection type gasoline engine has an advantage that the engine can be started quickly in about 1/6 rotation of cranking by injecting fuel at a high pressure during the first compression stroke at the time of starting. Therefore, when a cylinder injection gasoline engine is used for the idle stop vehicle, the start response is improved. However, if the fuel pressure decreases at this time, spray formation in the cylinder may be disturbed, or atomization (atomization) of fuel droplets cannot be promoted, and rapid start-up may be hindered.
[0028]
Therefore, as described above, when the fuel pressure falls below a predetermined value based on the information from the fuel pressure sensor 20, the engine is immediately started to hold the fuel pressure above the predetermined value.
Here, FIG. 3 is a graph in which the misfire region is examined using the fuel injection amount and the fuel injection end timing as parameters, (a) is when the fuel pressure is normal fuel pressure, and (b) is when the fuel pressure is lower than the normal fuel pressure. The case of a predetermined value is shown. In FIG. 3A and FIG. 3B, the asterisk marks indicate the optimal fuel injection amount and the optimal fuel injection end timing at the start. And from such a test result, it has confirmed that a misfire area became large as fuel pressure became low. In addition, as shown in FIG. 3B, it can be confirmed that if the fuel pressure can be secured at a predetermined value or more, the optimal fuel injection amount and the optimal fuel injection end timing do not enter the misfire region.
[0029]
Therefore, in the vehicle engine automatic start control device of the present invention, in view of the test results as described above, the engine is restarted when the fuel pressure falls below a predetermined value after the engine is automatically stopped.
Next, the forced restart prohibiting means 3c will be described. The forced restart prohibiting means 3c is provided with the following conditions for prohibiting engine restart (restart prohibiting conditions).
(1) Within a predetermined time after engine stop
This is provided for the purpose of protecting the starter 31. In other words, just before stopping the engine, when the piston of a cylinder comes to just before the top dead center, the top dead center is not exceeded, the crankshaft reverses by a slight angle and the engine may stop. If the starter pinion gear meshes with the flywheel during such reverse rotation of the crankshaft, the teeth of the pinion gear may be lost. Therefore, in this apparatus, even if other engine restart conditions are satisfied until the predetermined time has elapsed since the engine stopped, the restart of the engine is prohibited in preference to this. .
[0030]
As described above, whether or not the normal restart conditions (1) and (2) are both satisfied in a state where the restart prohibition condition is not satisfied (that is, after a predetermined time has elapsed after the engine is stopped). If any one of the forced restart conditions (1) to (10) is satisfied, the engine is restarted.
In addition to the above, for example, when the driver tries to shift from neutral without stepping on the clutch during automatic engine stop, an alarm is sounded to alert the driver, or the shift is actually performed. After this, the engine restart is prohibited.
[0031]
The vehicular engine automatic start control apparatus according to one embodiment of the present invention is configured as described above. Hereinafter, an example of the operation will be briefly described with reference to the flowchart shown in FIG. First, this routine starts when the ignition key is turned on. In step S1, it is determined whether or not the main switch 23 is on. If the main switch 23 is on, the idle stop function is in a standby state, and the process proceeds to step S2 and subsequent steps. If the main switch 23 is off, the process returns. However, since the main switch 23 is set to ON immediately after the ignition key is turned on, the process proceeds from step S1 to step S2 in the first control cycle.
[0032]
Next, in step S2, it is determined whether or not the engine is operating. If the engine is operating, the process proceeds to step S3, and if not, the process returns. In step S3, it is determined whether an engine stop condition is satisfied. That is, it is determined whether or not the automatic stop basic conditions (1) to (4) and the automatic stop permission conditions (1) to (9) set in the engine automatic stop means 2 are all satisfied.
[0033]
If all these conditions are satisfied, it is determined that the engine stop condition is satisfied, and the process proceeds to step S4, where the engine is automatically stopped (automatic stop). Further, if any one of the above conditions is not satisfied, the process returns without stopping the engine.
Next, it progresses to step S5, it is determined whether predetermined time passed after engine stop, and the determination in step S5 is repeated until predetermined time passes. When a predetermined time has elapsed, the engine restart prohibition condition is not satisfied, and the engine can be restarted.
[0034]
Thereafter, the process proceeds to step S6, and whether or not the normal restart conditions (starting basic conditions) (1) and (2) set in the normal restart means 3a in step S6 are satisfied (that is, normal restart) Whether the condition is satisfied) or one of the forced restart conditions (forced start conditions) (1) to (10) set in the forced restart means 3b is satisfied (that is, the forced restart condition is satisfied) Whether or not) is determined. When the forced restart condition is satisfied in step S6, the process proceeds to step S7, where the engine is restarted and the process returns.
[0035]
That is, when the driver's intention to start is determined by the normal restart means 3a, the engine is naturally restarted, and the safety and comfort of the vehicle may be impaired by the forced restart means 3b. If it is determined, the engine is forcibly started to ensure safety and comfort even when the auto stop is in progress and the driver does not intend to start.
[0036]
As described above, according to the vehicle automatic engine start control device according to the embodiment of the present invention, in addition to the advantages of a general idle stop vehicle, the engine is stopped based on information from each sensor. If it is determined that there is a possibility that the safety and comfort of the vehicle may be impaired, and if it is determined that there is a possibility, the automatic engine stop function is forcibly (actively) Is canceled or the engine is restarted, so there is an advantage that the safety and comfort of the vehicle can be ensured.
[0037]
In particular, even if the driver does not intend to start after the engine has been automatically stopped, there is an advantage that a reduction in vehicle safety and comfort can be reliably prevented by forcibly restarting the engine. Furthermore, when an in-cylinder injection gasoline engine is applied to the engine, the engine is forcibly started before falling into a state where rapid start by compression stroke injection is impossible, so that the startability of the engine is ensured. be able to.
[0038]
The vehicular engine automatic start control device of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, as the engine, each condition other than the condition (10) relating to the compression stroke start is not limited to the in-cylinder injection type engine, but can be widely applied to a general port injection type engine or the like. Moreover, the predetermined values (threshold values) such as the respective temperatures and current values described above are merely examples, and can be variously changed according to the specifications and performance of the vehicle.
[0039]
【The invention's effect】
  As detailed above,BookAccording to the vehicle automatic engine start control device of the invention,In-cylinder gasoline engineSince the engine is forcibly started when the pressure of the fuel supplied to the engine falls below a predetermined value, the optimal fuel injection amountAnd fuel injection pressureThe engine startability can always be kept good.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram focusing on functions of a vehicle engine automatic start control device according to an embodiment of the present invention.
FIG. 2 is a view for explaining characteristics of the vehicle engine automatic start control device according to the embodiment of the present invention;
FIGS. 3A and 3B are diagrams for explaining the characteristics of the vehicle engine automatic start control device according to the embodiment of the present invention. FIGS.
FIG. 4 is a flowchart for briefly explaining the operation of the vehicle engine automatic start control device according to the embodiment of the present invention;
[Explanation of symbols]
1 Control means (ECU)
2 Engine automatic stop means
3 Engine restart means
3a Normal restart means
3b Forced restart means
3c Forced restart prohibition means

Claims (1)

Vehicle having engine automatic stop means for automatically stopping the engine when a predetermined engine automatic stop condition is satisfied, and engine restart means for automatically starting the engine when the predetermined engine automatic start condition is satisfied after the engine is automatically stopped In the engine automatic start control device for
The engine is a direct injection gasoline engine capable of directly injecting fuel into a cylinder, and is configured to inject fuel at a high pressure into a cylinder in a compression stroke at the start,
The engine automatic start condition includes a start basic condition for determining a driver's intention to start a vehicle, and a forced start condition for forcibly starting the engine when the pressure of fuel supplied to the engine falls below a predetermined value.
The engine automatic start control device for a vehicle, wherein the engine restart means starts the engine when either one of the basic start condition and the forced start condition is satisfied.

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