JP2003239780A - Device for automatically stopping/restarting engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the shock when an engine is automatically restarted caused by the cost reduction of a motor and an inverter, etc. <P>SOLUTION: The device for automatically stopping/restarting the engine is applied to a vehicle in which the motor synchronously rotating with the engine and an automatic transmission with the torque converter are installed. The device is for automatically stopping and restarting the engine in the state when the driving torque from the engine can be transmitted to the driving wheels of the vehicle according to the operation condition of the vehicle. The device has a braking force detecting means for detecting the braking force of the vehicle. When the braking force is a first prescribed determination value or lower while the vehicle is stopped with the engine automatically stopped, the engine is rotated by the motor, and when the braking force is a second prescribed determination value, smaller than the first determination value, or lower, combustion of the engine is started. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic engine stop / restart device.

[0002]

2. Description of the Related Art A vehicle equipped with an automatic engine stop / restart device has been conventionally known in order to improve fuel efficiency and exhaust emission of the vehicle.

This automatic engine stop / restart device is used when the vehicle is temporarily stopped while the driving force in the forward direction can be transmitted to the driving wheels, that is, when the select lever of the automatic transmission is in the D range. , When the vehicle is temporarily stopped due to waiting for a signal, the engine automatically stops.
Then, when the vehicle starts again, the engine is automatically restarted.

By the way, when the engine is automatically restarted, the negative pressure in the intake passage of the engine is small (close to the atmospheric pressure) between the automatic stop of the engine and the automatic restart of the engine. When combustion of the engine is started in this state, the engine pressure blows up due to the high combustion pressure,
Due to so-called overshoot in which the engine speed rapidly increases, the drive torque may rapidly increase, giving an uncomfortable shock to the vehicle occupant.

With respect to such a problem, Japanese Patent Laid-Open No. 2000-
No. 205003 discloses combustion of an engine after a motor generator (electric motor) that rotates synchronously with the engine causes the engine to motor up to a predetermined engine speed or after the engine has been motorized for a predetermined time. When the engine speed exceeds the predetermined target speed, the motor generator is switched from the power running mode to the regenerative mode to prevent overshoot of the engine speed. Suppress,
A technique for reducing a shock caused by a rapid rise in driving force is disclosed.

[0006]

However, in such a conventional technique, when burning the engine,
Since the magnitude of the brake braking force acting on the vehicle is not taken into consideration, if the brake braking force remains when starting the engine combustion, the engine torque suddenly increased due to the combustion of the engine causes the regenerative motion of the motor generator. If it is not absorbed completely by the engine, the driving force due to the engine torque is suppressed by the brake, and the reaction force of this driving force is received by the mount of the engine or automatic transmission and transmitted to the vehicle body to convey a shock to the driver. There is a problem that it will end up.

Further, in order to control the rotation speed of the motor generator, it is necessary to perform switching control between the power running operation and the regenerative operation of the motor generator with high accuracy, and for that purpose, a switching element, a motor controller and an inverter capable of high-speed calculation are used. And the like are required, which causes problems such as an increase in cost, an increase in weight, and deterioration of mountability in a vehicle. Further, if the cost of these drivers is reduced, the rotation speed of the motor generator cannot be controlled with high accuracy, and it becomes impossible to suppress the overshoot of the engine rotation speed.

Therefore, the automatic engine stop / automatic restart device according to the present invention has a brake braking force as a condition for starting combustion of the engine against a shock at the time of automatic restart of the engine, which is a problem due to the cost reduction of the electric motor and the inverter. The purpose of this is to make it possible to reduce this shock.

[0009]

Therefore, the invention described in claim 1 is applied to a vehicle equipped with an electric motor that rotates in synchronization with an engine and an automatic transmission having a torque converter, and is driven by the engine. In the automatic engine stop / automatic restart device that automatically stops / automatically restarts the engine according to the driving conditions of the vehicle while torque can be transmitted to the drive wheels of the vehicle, the automatic engine stop / automatic restart device is A brake braking force detecting means for detecting a brake braking force of the vehicle, and when the brake braking force becomes a predetermined first judgment value or less while the engine is automatically stopped, the engine is rotated by the electric motor to brake the brake. It is characterized in that the combustion of the engine is started when the motive power becomes equal to or less than a predetermined second determination value which is smaller than the first determination value. At the start of combustion of the engine, the engine is already started by the electric motor (motoring), so the intake negative pressure develops, the intake air amount decreases, and the combustion pressure becomes low. Further, it is not necessary to control the rotation speed of the electric motor by determining the combustion start timing of the engine from the brake braking force.

According to a second aspect of the present invention, in the first aspect of the present invention, the brake braking force detecting means measures the brake fluid pressure or the depression amount of the brake pedal as the brake braking force. It has a feature.

According to a third aspect of the present invention, in the first or second aspect of the invention, the second determination value of the brake braking force is due to an overshoot of the engine speed that occurs with the start of combustion of the engine. When the overshoot torque that is transmitted to the drive wheels of the vehicle is transmitted, the overshoot torque is set to a degree that allows a slight rotation of the drive wheels.
As a result, the drive wheels are slightly rotated by the overshoot torque, and the reaction force of the overshoot torque received by the mount of the engine, the automatic transmission, or the like is reduced.

According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects, the brake braking force is first.
It is characterized in that the combustion of the engine is started even if the brake braking force is not less than or equal to the second determination value when a predetermined time elapses after the determination value is less than or equal to the determination value. Thus, for example, even when the brake braking force is held at a value between the first determination value and the second determination value for a long time, the combustion of the engine is started after the predetermined time has elapsed, so that the electric motor It is possible to prevent the operating time from becoming too long.

[0013]

According to the present invention, by determining the combustion start timing of the engine from the brake braking force, the overshoot torque resulting from the overshoot of the engine speed generated with the start of combustion of the engine is Even if the driving force is transmitted to the drive wheels, if the braking force is small, the drive wheels are slightly rotated and absorbed. That is, it is not necessary to suppress the overshoot torque due to the overshoot of the engine speed by controlling the rotation speed of the electric motor.

Therefore, even if an electric motor that does not control the rotation speed is used, it is possible to suppress the shock felt by the driver due to the overshoot of the engine rotation speed, and the driver such as the switching element, the motor controller and the inverter, and the like. The cost of the electric motor itself can be reduced.

Further, according to the invention of claim 4, it is possible to prevent the operating time of the electric motor from becoming excessively long and to save the electric power consumption of the electric motor.

[0016]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, an automatic transmission 2 is connected to the rear end of the engine 1. This automatic transmission 2
Consists of a torque converter 3 on the engine 1 side and a CVT (continuously variable transmission) 4 connected to the engine 1 via the torque converter 3, and the output side of the CVT 4 is
Similar to a general automobile, it is connected to drive wheels (not shown) via a final reduction gear device (not shown). A stepped automatic transmission may be used instead of the CVT 4.

At the front end of the engine 1, a crank pulley 6 which rotates integrally with the crank shaft 5 is arranged. Then, this crank pulley 6 and an AC motor generator 7 as an electric motor (hereinafter referred to as an AC motor)
The motor pulley 8 attached to the output shaft 7a of
The belt 9 is wrapped around. That is, the AC motor 7 and the crankshaft 5 are configured to rotate synchronously.

The AC motor 7 is a motor controller 11 which receives a command from the total control unit 10.
The start and stop, and switching between power running operation and regenerative operation are controlled by. That is, during power running operation of the AC motor 7 such as at engine start-up, electric power from the battery 13 is supplied to the AC motor 7 via the inverter 12,
During the regenerative operation of the AC motor 7 that receives the rotation of the engine 1, the AC motor 7 controls the power generation and the charging of the battery 13 with the power generated by the AC motor 7.

The total control unit 10 controls the operation of the engine 1 together with the engine control module 14, and receives a signal from the battery controller 15 which detects the charge amount of the battery 13. Furthermore, the total control unit 10
Includes an oil temperature sensor 16 for detecting the oil temperature of the CVT 4, a CV
The hydraulic pressure sensor 17 for detecting the hydraulic pressure of T4, the water temperature sensor 18 for detecting the cooling water temperature of the engine 1, the accelerator sensor 20 for detecting the on / off of the accelerator pedal, the engine speed sensor 21 for detecting the engine speed, and the vehicle speed are A vehicle speed sensor 22 for detecting, a select position sensor 23 for detecting a select position of the automatic transmission 2, an open / close sensor 2 for detecting an open / closed state of an open / close device such as a vehicle door or hood.
4. Brake negative pressure booster sensor 25 for detecting the negative pressure of the brake negative pressure booster for assisting the operation of the brake pedal, and brake pedal sensor 26 as a brake braking force detecting means for detecting the depression amount of the brake pedal.
Also, a signal from a brake fluid pressure sensor 27 as a brake braking force detecting means for detecting the brake fluid pressure is input.

The braking force is proportional to the brake fluid pressure and the brake pedal depression amount, and can be estimated by detecting the brake fluid pressure and the brake pedal depression amount. The open / close sensor 24 detects the open / closed states of all opening / closing devices of the vehicle such as doors and hoods.

When the total control unit 10 determines that there is an automatic engine stop request (described later in detail) when the vehicle is temporarily stopped after the warm-up operation is completed,
The fuel injection of the engine 1 is stopped to stop the engine 1 (engine automatic stop). Further, when the total control unit 10 determines that there is an engine automatic restart request (details will be described later), it automatically restarts the engine.

Here, the control contents executed by the total control unit will be described with reference to the flowchart of FIG.

First, in step 1, it is confirmed whether the engine 1 is in idle stop, that is, in the state where it is automatically stopped. If the engine 1 is automatically stopped, the process proceeds to step 2 and if the engine 1 is not automatically stopped. Proceed to step 13.

At step 2, it is judged whether or not there is a request for starting the AC motor 7. That is, when the selector lever of the automatic transmission 2 is in the D range, the brake pedal is depressed by the driver, the vehicle speed is 0 (km / h), and the opening / closing devices such as the door and the bonnet are all closed, While stopped, the accelerator is turned on, the brake is turned off, the charge amount of the battery 13 is below a predetermined value (battery SOC is low), the negative pressure of the brake negative pressure booster is below a predetermined value, the engine water temperature is below a predetermined value, and the oil temperature of the CVT 4 is predetermined. Below the value, CVT
If any of the hydraulic pressures of 4 and below is detected, A
The total control unit 10 determines that there is a request to start the C motor 7. The accelerator ON is detected when the depression amount of the accelerator pedal is equal to or more than a predetermined value. Brake OFF means that when the amount of depression of the brake pedal is equal to or less than the first pedal depression amount first determination value,
Alternatively, it is detected when the brake fluid pressure becomes equal to or lower than a predetermined brake fluid pressure first determination value.

If it is determined in step 2 that there is a request to start the AC motor 7, the process proceeds to step 3 and immediately A
The C motor 7 is started, and the motoring of the engine 1 is started by the power running operation of the AC motor 7.

In step 4, it is determined whether the request to start the AC motor 7 is made by turning off the brake.
If the activation request for the AC motor 7 is made by turning off the brake, the process proceeds to step 5, and if not, the process proceeds to step 8.

In step 5, it is determined whether or not a predetermined constant time (for example, 1 to 2 seconds) has elapsed from the start of motoring, that is, the start of the AC motor 7. If the predetermined fixed time has not elapsed, the routine proceeds to step 6, where it is determined whether the brake braking force has become equal to or less than a predetermined ignition permission threshold value by turning off the brake. More specifically, the brake pedal depression amount is smaller than a predetermined pedal depression amount second determination value (ignition permission threshold value) smaller than the pedal depression amount first determination value, or the brake fluid pressure is the brake fluid pressure first determination. If it is less than or equal to a predetermined brake fluid pressure second determination value (ignition permission threshold value) smaller than the value, the process proceeds to step 7 and combustion of the engine 1 is started.

Further, in step 5, if a predetermined constant time has elapsed after the start of motoring, the amount of depression of the brake pedal is equal to or less than the second pedal depression amount judgment value (ignition permission threshold value), or the brake is applied. Even if the hydraulic pressure is not lower than the second brake hydraulic pressure determination value (ignition permission threshold value), the routine proceeds to step 7 and combustion of the engine 1 is started.

When the process proceeds from step 4 to step 8, motoring (step 8) is continued, and when the brake OFF is detected during this motoring (step 9), the process proceeds to step 5. Further, when a predetermined fixed time (1 to 2 seconds) elapses after the motoring is started in step 8 and the brake OFF is not detected (step 1
0), the process proceeds to step 7 to start combustion of the engine 1.

When the combustion of the engine 1 is started, it is determined in step 11 whether the engine speed has reached a predetermined target speed. The target rotation speed is specifically the idle rotation speed of the engine 1.

In step 11, in consideration of the overshoot of the engine speed, the engine speed reaches the target speed when the engine speed continuously maintains the target speed (idle speed) for a certain period of time. To determine. When it is determined in step 11 that the engine speed has reached the target speed, the process proceeds to step 12, and the AC motor 7 is stopped.

In step 13, it is determined whether or not there is a request to automatically stop the engine 1. That is, when the select lever of the automatic transmission 2 is in the D range, the brake pedal is depressed by the driver, the vehicle speed is 0 (km / h), and the opening / closing devices such as the door and the hood are all closed, the engine 1 is When burning, accelerator off, brake O
N, the charge amount of the battery 13 (battery SOC) is a predetermined value or more, the negative pressure of the brake negative pressure booster is a predetermined value or more, the engine water temperature is a predetermined value or more, the oil temperature of CVT4 is a predetermined value or more, and the oil pressure of CVT4 is a predetermined value. If it is above, there is a request for automatic engine stop and the total control unit 10
Is determined and the engine 1 is stopped in step 14.

In this way, steps 1 to 12
The above is the control regarding the automatic engine restart, and the steps 13 and 14 are the control regarding the automatic engine stop.

The accelerator OFF is detected when the depression amount of the accelerator pedal becomes a predetermined value or less. Brake ON is detected when the amount of depression of the brake pedal exceeds a predetermined value or when the brake fluid pressure exceeds a predetermined value. Further, the conditions for the negative pressure of the brake negative pressure booster, the engine water temperature, the oil temperature and oil pressure of the CVT 4, and the charge amount of the battery 13 (battery SOC) are included in the request for starting the AC motor 7 and the request for automatically stopping the engine. This is to prevent the starting time at the time of automatic engine restart from varying due to the influence of these parameters.

FIG. 3 shows a timing chart when the engine is automatically restarted. In FIG. 3, the brake hydraulic pressure is taken as an example of the brake OFF condition.

When the brake fluid pressure corresponding to the brake braking force becomes equal to or less than the predetermined brake fluid pressure first determination value, the AC motor 7 starts the power running operation. When the brake fluid pressure becomes equal to or lower than a predetermined brake fluid pressure second determination value (ignition permission threshold value) smaller than the brake fluid pressure first determination value, combustion of the engine 1 is started. The second brake fluid pressure determination value (ignition permission threshold value) is obtained when the overshoot torque resulting from the overshoot of the engine speed that occurs with the start of combustion of the engine 1 is transmitted to the drive wheels of the vehicle. The overshoot torque is set so as to allow a slight rotation of the drive wheels.

After the combustion of the engine 1 starts, when the engine speed reaches a predetermined target speed such as an idle speed, A
The operation of the C motor 7 is switched to the regenerative operation. In addition, AC
The motor 7 stops its operation when a certain time has elapsed after the engine speed stabilizes at the target speed.

The driver's intention to restart the vehicle is detected by an operation of loosening the depressed brake pedal such as a change in the brake pedal depression amount or the brake fluid pressure,
Using that as a trigger, the AC motor 7 is power-operated, after which combustion of the engine 1 is started, and the engine 1 is instantly and automatically restarted.

In the case of a vehicle equipped with a torque converter, D
When the combustion of the engine is started from the range, the driving force corresponding to the engine speed is transmitted to the drive wheels. Therefore, when the engine speed overshoots, the driving force suddenly acts on the drive wheels.

When the driving force is transmitted to the driving wheels with the brake braking force remaining, the reaction force of the driving force is received by the mounts of the engine 1 and the automatic transmission 2 and is transmitted to the vehicle body. As indicated by a broken line in the figure, the shock felt by the driver is beyond the allowable range, and the driver feels uncomfortable.

When the wheels are not fixed by a brake or the like, the driving force is used as a force for moving the vehicle, energy is consumed, and the driving force is transmitted from the mount of the engine or CVT (automatic transmission) to the vehicle body. The reaction force of the force is reduced, and the shock felt by the driver can be alleviated. That is, the vehicle will move slightly, but there is no problem because the driver originally intended to start.

Therefore, as in the present invention, the brake fluid pressure is small and the brake fluid pressure or the amount of depression of the brake pedal that can reduce the shock at the time of overshoot of the engine speed is the second brake fluid pressure determination value (ignition permission). By setting the threshold value) to the second depression amount second determination value (ignition permission threshold value) and permitting the start of combustion of the engine 1, it is possible to mitigate the shock received by the driver when the engine 1 is automatically restarted.

Further, since the shock received by the driver at the time of automatic restart of the engine 1 can be alleviated without controlling the rotational speed of the AC motor 7, the control current of the AC motor 7 is converted into the scalar control so that the inverter 12 and the motor can be controlled. The controller 11 can be simplified, and the cost of the switching element, the drivers such as the motor controller 11 and the inverter 12, and the AC motor 7 itself can be reduced.

Further, a time interval until the brake braking force reaches the second determination value from the first determination value, that is, from the brake fluid pressure first determination value to the brake fluid pressure second determination value. The time interval or the amount of depression of the brake pedal is from the first depression amount to the second depression amount.
When the time interval until the judgment value is reached has passed a fixed time of about 1 to 2 seconds (when the brake pedal is slowly loosened), the intake negative pressure develops due to the activation of the AC motor 7, and engine combustion is performed. However, since the intake air amount is decreasing, the combustion pressure is low, overshoot does not occur,
No shock will occur.

Therefore, when the time interval between the first judgment value and the second judgment value (ignition permission threshold value) of the brake braking force is a certain time or more, the brake braking force is less than the first judgment value. Therefore, if engine combustion is started after 2 seconds, for example, it is possible to prevent shock and reduce power consumption due to continuing motoring for a long time, and prevent deterioration of fuel consumption.

In the first embodiment described above, both the brake fluid pressure and the amount of depression of the brake pedal are detected as the braking force, but the total control unit 10 detects only one of them. You may do it.

Next, a second embodiment of the present invention will be described. The same components as those in the first embodiment described above are designated by the same reference numerals, and duplicate description will be omitted.

In the second embodiment, the DC motor 30 is used as the electric motor, and the DC motor 30 includes the clutch 31.
It is connected to the motor pulley 8 via. Clutch 3
1 indicates that the DC motor 30
Is controlled by the total control unit 10 so that the DC motor 30 is stopped and the DC pulley 30 is disconnected from the motor pulley 8 at the same time when the DC motor 30 is stopped.

The on / off control of the clutch 31 is performed by the DC motor 3
0 is started and stopped at the same time as the DC motor 30
The DC motor 30 is controlled so as to rotate synchronously with the engine 1 only during the rotation.

The start-up control of the DC motor 30 is performed by the control unit 10, and the start-up timing is the same as in the first embodiment described above. That is, when the brake fluid pressure is equal to or less than the predetermined brake fluid pressure first determination value or the brake pedal depression amount is equal to or less than the predetermined depression amount first determination value during the automatic stop of the engine 1, the DC motor 30 is started, After engine combustion, when the engine speed reaches the target speed, the DC motor 30 is stopped.

Thus, even when the DC motor 30 is used as the electric motor, the DC motor 30 is started when the brake braking force becomes equal to or lower than the first determination value, and the brake braking force becomes equal to or lower than the predetermined second determination value. If the combustion of the engine 1 is started when a predetermined time elapses after the braking force becomes less than or equal to the first determination value, the same effect as that of the above-described first embodiment can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a system configuration of an automatic engine stop / automatic restart device according to the present invention.

FIG. 2 is a flowchart showing the control contents of the automatic engine stop / restart system according to the present invention.

FIG. 3 is a timing chart at the time of automatic restart of the engine in the automatic engine stop / automatic restart device according to the present invention.

FIG. 4 is an explanatory diagram showing a system configuration of another embodiment of the automatic engine stop / automatic restart device according to the present invention.

[Explanation of symbols]

1 ... engine 2 ... Automatic transmission 3 ... Torque converter 4 ... CVT (continuously variable transmission) 7 ... AC motor 10 ... Total control unit 11 ... Motor controller 12 ... Inverter 13 ... Battery

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02N 11/04 F02N 11/04 A 11/10 11/10 AC 15/00 15/00 EF term ( Reference) 3G084 BA28 CA01 DA11 EB16 EC01 FA03 FA05 FA06 FA10 FA20 FA33 3G092 AA01 AB02 AC03 CA01 DG08 EA16 FA04 FA30 GA01 HE01Z HE08Z HF02Z HF05Z HF08Z HF11Z HF12Z HF12Z HF26Z 3G093 AA05 DB01 DB01 DA02 BA01 DA02 BA21 BA01 BA02 BA21 BA21 BA01 BA01 BA02 BA21 BA21 BA01

Claims (4)

[Claims] 1. The present invention is applied to a vehicle equipped with an electric motor that rotates in synchronization with an engine and an automatic transmission equipped with a torque converter, wherein the driving torque of the engine can be transmitted to driving wheels of the vehicle. In an engine automatic stop / automatic restart device that automatically stops / automatically restarts the engine according to operating conditions, the automatic engine stop / automatic restart device includes a braking force detection means for detecting the braking force of the vehicle. Have,
When the brake braking force becomes less than or equal to the predetermined first determination value while the vehicle is stopped automatically, the engine is rotated by the electric motor, and the brake braking force becomes less than or equal to the predetermined second determination value less than the first determination value. When this happens, an engine automatic stop / restart device is characterized by starting combustion of the engine. 2. The engine automatic stop / automatic restart according to claim 1, wherein the brake braking force detection means measures a brake fluid pressure or a depression amount of a brake pedal as the brake braking force. apparatus. 3. The second determination value of the braking force is the above-mentioned overshoot when the overshoot torque resulting from the overshoot of the engine speed generated with the start of combustion of the engine is transmitted to the drive wheels of the vehicle. 3. The shoot torque is set so as to allow a slight rotation of the drive wheel.
The automatic engine stop / restart device described in. 4. The engine combustion is started when a predetermined time has elapsed after the brake braking force becomes equal to or lower than the first determination value, even if the brake braking force does not become equal to or lower than the second determination value. The automatic engine stop / restart device according to any one of 1 to 3.