JP2000328980A - Idle stop vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent starting performance of a vehicle mounted with a continuously variable transmission from decreasing when it restarts, since an idle stop system therein is activated while a transmission gear ratio is not maximum. SOLUTION: A vehicle with an idle stop system is provided with an engine 1, drive-wheel 7, and continuously variable transmission 5 interposed between the engine 1 and drive-wheel 7. When the vehicle stops, a controller 15 automatically stops the engine 1 provided that the prescribed condition for the idle stop is satisfied. In this case, when a transmission gear ratio of the continuously variable transmission 5 is less than a prescribed threshold level, the controller 15 prohibits the engine 1 from stopping automatically. Therefore, the idle stop system is not activated while the transmission gear ratio is still low, and thus starting performance when restarting is prevented from decreasing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle for automatically stopping an engine when stopping and automatically restarting the engine when restarting.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 8-291725 discloses that, for the purpose of improving fuel efficiency and suppressing exhaust gas, when a vehicle is stopped at a traffic light or in traffic jam, the engine is automatically stopped. An idle stop vehicle that automatically restarts the engine is disclosed. Similar automatic engine stop,
Automatic restart is also possible in a vehicle equipped with a belt-type or toroidal-type continuously variable transmission (hereinafter, CVT) as a transmission. In this case, further improvement in fuel efficiency and suppression of exhaust gas can be expected.

[0003]

Problems to be Solved by the Invention When the engine is automatically stopped, the gear ratio is set to a maximum (maximum Lo).
w), it is necessary to ensure startability at the time of restart. Normally, in a CVT-equipped vehicle, the speed ratio is controlled based on the throttle opening and the vehicle speed, and when the vehicle is stopped, the speed ratio is maximized. Therefore, even if the engine is automatically stopped, the startability at the time of restarting is impaired. Never.

[0004] However, when the vehicle is suddenly stopped by applying a sudden brake, or when the wheels are locked or AB
When the vehicle stops with the rotation of the wheels being small due to the operation of the S (anti-lock brake system), the vehicle may be stopped without returning to the maximum gear ratio. In this case, C
The gear ratio cannot be changed unless a disconnection means such as a clutch is provided between the VT and the axle, the vehicle restarts from a state with a small gear ratio, and the startability at the time of restarting deteriorates. If the idle stop is executed, the startability is further deteriorated due to a response delay of the engine or the hydraulic pump.

[0005] Further, even if the vehicle is provided with a shut-off means between the CVT and the axle and can change the gear ratio while the vehicle is stopped, the CV
The same problem occurs if the shift response of T is poor and the engine is automatically stopped before the gear ratio returns to the maximum.

The present invention has been made in view of the above technical problem, and in a vehicle with a CVT, an idle stop is executed in a state where the gear ratio is not at a maximum, and the startability at the time of restart is further deteriorated. The purpose is to prevent

[0007]

According to a first aspect of the present invention, there is provided an engine, a drive wheel driven by the engine, a continuously variable transmission interposed between the engine and the drive wheel, and a vehicle in a stopped state. Means for calculating the speed ratio of the continuously variable transmission in an idle stop vehicle having idle stop means for automatically stopping the engine when a predetermined idle stop condition is satisfied; Idle stop prohibiting means for prohibiting the automatic stop of the engine by the idle stop means when it is smaller.

According to a second aspect of the present invention, in the first aspect, there is provided means for detecting a road surface gradient at the own vehicle position, and means for calculating the predetermined threshold value based on the detected road surface gradient. It is a feature.

According to a third aspect of the present invention, in the first aspect, there are provided means for estimating a starting load at the own vehicle position, and means for calculating the predetermined threshold value based on the estimated starting load. It is a feature.

According to a fourth aspect of the present invention, in the first aspect, if the motor capable of transmitting the driving force to the driving wheels and the idle stop prohibiting means prohibits the automatic stop of the engine, the driving force is assisted by the motor at the time of restart. And means for performing the operation.

According to a fifth aspect of the present invention, in the fourth aspect, means is provided for calculating an assist torque at the time of restart by the motor in accordance with a speed ratio of the continuously variable transmission.

In a sixth aspect based on the fourth or fifth aspect, the means for detecting a road surface gradient at the own vehicle position and the means for calculating the assist torque at the time of restart by the motor in accordance with the detected road surface gradient. It is characterized by having.

According to a seventh aspect, in the first aspect, the continuously variable transmission has a snow mode, and the idle stop prohibiting means does not prohibit the automatic stop of the engine when the snow mode is selected. It is characterized by the following.

According to an eighth aspect of the present invention, in the first aspect, a driving force cut-off means is provided between the continuously variable transmission and the driving wheels, and the idle stop prohibiting means is provided with a speed ratio corresponding to the calculated first speed ratio. It is characterized in that the automatic stop of the engine is prohibited while it is smaller than.

[0015]

According to the first aspect of the present invention, even if the vehicle is stopped due to signal waiting or traffic congestion and a predetermined idle stop condition is satisfied, the gear ratio is smaller than a predetermined threshold value (to the high side). Yes) and idle stop is prohibited. If the gear ratio is small, the startability at the time of restarting will be worse, and if the idle stop is executed, the startability will be further worse.In such a state, the idle stop is prohibited, so the startability at the time of restarting will be further deteriorated Can be prevented.

The startability at the time of restarting is greatly influenced by the road gradient at that time and the load required for starting. According to the second and third aspects of the present invention, the detected road gradient and the estimated starting load are determined. The threshold value for determining whether or not to prohibit the idle stop is calculated based on the above, so that it is possible to appropriately determine whether or not to prohibit the idle stop.

According to the fourth aspect of the invention, when the automatic stop of the engine is prohibited, that is, when the vehicle is stopped with a small gear ratio, the driving force is assisted by using the motor at the time of restart. Therefore, even when the vehicle is started from a state where the gear ratio is small, the vehicle can be smoothly started.

Further, the assist torque required for a smooth start increases as the ascending gradient becomes steeper and the starting load increases, but according to the fifth and sixth aspects of the invention, the detected road surface slope and starting torque are increased. Since the assist torque is calculated based on the load, the desired startability can be always ensured.

Further, according to the seventh aspect, when the driver selects the snow mode intended to start at a low gear ratio, the idle stop is not prohibited, so that the driver's intention is prioritized. be able to.

According to the eighth aspect, the idle stop is executed after the speed ratio becomes larger than the speed ratio corresponding to the first speed of the stepped transmission. As a result, it is possible to prevent the idle stop from being performed in a state in which the shift cannot be made in time and the speed ratio is small, and that the startability at the time of restarting is deteriorated.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of an idle stop vehicle according to the present invention. The output of the engine 1 is transmitted to driving wheels 7 via a torque converter 3, a forward / reverse switching mechanism 4, a belt-type continuously variable transmission (CVT) 5, and a drive shaft 6. 3, the engine 1 is directly connected to the crankshaft.
And a motor generator 2 that rotates in synchronization with the motor generator.

The engine 1 has an injector (not shown),
A spark plug is provided for each cylinder to perform fuel injection corresponding to the intake air amount and spark ignition corresponding to the engine load and the engine speed. The engine 1 is a so-called multipoint injection type engine in which an injector is provided in an intake port of each cylinder to inject fuel, but may be a direct injection type engine in which fuel is directly injected into each cylinder.

The motor generator 2 is an AC machine that can function as both a motor and a generator. Motor generator 2 is connected to battery 8 via inverter 9.
Can be powered by power supply from
The regenerative operation is performed in response to the output of the engine 1, and the battery 8 can be charged via the inverter 9.

The forward / reverse switching mechanism 4 is composed of a forward clutch and a reverse clutch. When the forward clutch is engaged and the reverse clutch is released, the driving force can be transmitted in the direction in which the vehicle moves forward. When the clutch is released and the reverse clutch is engaged, the driving force can be transmitted in a direction to move the vehicle backward. Further, when both the forward clutch and the reverse clutch are released, transmission of the driving force to the driving wheels can be cut off.

The CVT 5 has a so-called snow mode in addition to the normal running mode. When the driver selects this snow mode when traveling on a low μ road such as a snowy road, the shift pattern of the CVT 5 is set so that the gear ratio becomes smaller than that in the normal traveling mode, for example, the gear ratio corresponding to the second speed of the stepped transmission when starting. Is changed.

The rotation speeds of the engine 1 and the motor generator 2 are detected based on a REF signal cycle output from the crank angle sensor 10, and the intake air amount and the cooling water temperature of the engine 1 are detected by an air flow meter and a water temperature sensor (not shown). . Further, the depression operation of the brake pedal and the operation amount of the accelerator pedal by the driver are detected by the brake sensor 11 and the accelerator sensor 12, respectively.

In addition, the vehicle is provided with a road surface gradient sensor 13 for detecting the gradient of the road surface at the vehicle position, and a navigation system 14 for storing road surface information such as a bad road or a paved road and a road shape. Information outside the vehicle can be detected. Note that the road surface gradient may be calculated from information stored in the navigation system 14.

The controller 15 controls the engine 1, the motor generator 2, the CVT 5 and the like on the basis of the detected operating state and external information. I do. When decelerating or traveling on a downhill road, the motor generator 2 is regeneratively operated to assist the braking force, and the battery 8 is charged with the regenerated electric power.

Further, the controller 15 processes the flow shown in FIG. 2 and performs automatic stop control of the engine. That is, when the vehicle is not in the idle stop prohibiting mode described later and a predetermined engine automatic stop condition is satisfied while the vehicle is stopped at a traffic light or in a traffic jam (S11, S12), the fuel injection to the engine 1 is stopped and the engine 1 is stopped. Automatically stop (S
13). On the other hand, when the speed ratio of the CVT 5 when the vehicle is stopped is small and the engine is in the idle stop prohibition mode, the automatic stop of the engine is not performed (S11), and the startability at the time of restarting is prevented from deteriorating. Here, the predetermined condition for automatically stopping the engine is satisfied, for example, when the engine 1 has been warmed up, the brake pedal is depressed, the vehicle speed is almost zero, and the accelerator pedal is depressed. None ・ The engine speed is the idle speed.

When the engine is stopped, the controller 15 processes the flow shown in FIG. 3 and performs automatic restart control of the engine. That is, when a predetermined engine automatic restart condition, such as the depression of the brake pedal is released or the engine stop time exceeds a predetermined time (S21), an engine restart command is issued and the engine 1 is automatically restarted. (S22).

Further, the controller 15 determines whether or not to shift to the idle stop prohibition mode for prohibiting the automatic stop of the engine by processing the flow shown in FIG.

According to this, first, at step S31, it is determined whether the vehicle is stopped or not, and at step S32, it is determined whether the snow mode is not selected. It is determined that the vehicle is stopped and the snow mode is not selected. If so, the process proceeds to step S33.

In step S33, the road surface gradient sensor 13
The starting load is estimated from road surface information such as a road surface gradient, a bad road detected by the navigation system, and a pavement road. In step S34, the speed ratio of the CVT 5 (= input shaft rotation speed / output shaft) Rotation speed).

In step S35, the detected road surface gradient,
Based on the estimated starting load, an I / S prohibition threshold for determining whether to prohibit the idle stop is calculated with reference to a map shown in FIG. As the I / S prohibition threshold value, a larger value is calculated as the upslope becomes steeper,
A smaller value is calculated as the downhill becomes steeper. A large value is also calculated when there is a factor that increases the starting load, such as when the running road surface is a bad road.

In step S36, the gear ratio of the CVT 5 detected in step S34 is calculated based on the I / V calculated in step S35.
It is determined whether it is smaller than the / S prohibition threshold value. If the speed ratio of the CVT 5 is smaller than the I / S prohibition threshold value, the process proceeds to step S37, and shifts to the idle stop prohibition and assist start mode.

In the assist start mode, at the time of restart, the motor generator 2 is driven by power to perform driving force assist. At this time, the assist amount is calculated based on the road surface gradient and the gear ratio with reference to the map shown in FIG. 6, and the assist amount is calculated to be larger as the up grade becomes steeper and the gear ratio of the CVT 5 becomes smaller.

On the other hand, when the gear ratio of the CVT 5 is larger than the threshold value, the startability at the time of restarting is not affected even if the idle stop is executed, and the driving force assist at the time of restarting is not required. Then, the process proceeds to step S38 to shift to the idle stop permission and assist start no mode.

Accordingly, by processing this flow, in a situation where the gear ratio of the CVT 5 is small and the startability at the time of restarting is predicted to be degraded when the idle stop is executed, the vehicle shifts to the idle stop prohibition mode. Even if the idle stop condition is satisfied, the idle stop is not executed.

Next, the effect of performing such control will be described with reference to FIG.

As shown in this figure, when the speed ratio of the CVT 5 is sufficiently large and the vehicle is not in the idle stop prohibition mode, the engine 1 is activated when predetermined engine automatic stop conditions are satisfied when the vehicle is stopped. The engine 1 is automatically stopped (time t1), and when the engine automatic stop condition is not satisfied, the engine 1 is automatically restarted (time t2). CVT5
If the gear ratio is sufficiently large, even if the idle stop is performed in this manner, the startability at the time of restarting does not deteriorate.

However, when the speed ratio of the CVT 5 is smaller than the predetermined I / S prohibition threshold value and the vehicle is in the idle stop prohibition mode, the vehicle is stopped and the engine 1 is stopped even if the engine automatic stop condition is satisfied. Is not automatically stopped (time t3). If the vehicle is stopped in a state where the speed ratio is small, the startability deteriorates, and if the idle stop is executed here, the startability further deteriorates due to a response delay of the engine or the hydraulic pump. In such a state, the idle stop is prohibited.

Further, when the vehicle is stopped in the idle stop prohibition mode, the vehicle is restarted from a state where the gear ratio is small. In such a case, the motor generator 2 appropriately drives the vehicle according to the road surface gradient and the road surface condition. Force assist is performed (time t4). As a result, even if the gear ratio of the CVT 5 is small, a sufficient driving force can be secured, and the vehicle can be started smoothly.

Next, a second embodiment will be described.

In this embodiment, as shown in FIG.
A forward / reverse switching mechanism 4 'is provided between the drive wheel 5 and the drive wheels 7 as a driving force cutoff means. If the forward clutch and the reverse clutch of the forward / reverse switching mechanism 4' are released, the CVT 5 can be shifted even when the vehicle is at a standstill. The difference from the first embodiment is that the ratio can be changed. The same components as those in the first embodiment are denoted by the same reference numerals.

FIG. 9 shows the processing performed in the controller 15. This flow is executed instead of the flow shown in FIG.

According to this, first, at step S41, it is determined whether or not the vehicle is stopped. When it is determined that the vehicle is stopped, at step S42, the CVT speed ratio 5 is set to the first speed of the stepped transmission. It is determined whether the gear ratio is larger than the gear ratio corresponding to.

When the CVT speed ratio is smaller than the speed ratio corresponding to the first speed, the process proceeds to step S43 to shift to the idle stop prohibition mode, and waits until the speed ratio of the CVT 5 becomes larger than the speed ratio corresponding to the first speed. When the speed ratio becomes larger than the speed ratio corresponding to the first speed, the process proceeds to step S44, and idle stop is permitted.

Therefore, in this embodiment, as shown in FIG. 10, even if the vehicle is stopped and the idle stop condition is satisfied, the idle stop is not executed if the gear ratio is small (time t5). When the gear ratio of the CVT 5 returns to the first speed, idle stop is permitted (time t6).

As a result, idling stop in a state where the gear ratio is small is prohibited, so that restarting from a state where the gear ratio is small can be prevented, and the startability at the time of restart can be prevented from being deteriorated. it can.

Here, the completion of the shift is determined based on the fact that the speed ratio has become larger than the speed ratio corresponding to the first speed. However, instead of the speed ratio corresponding to the first speed, it is determined in the first embodiment. The completion of the shift may be determined using the I / S prohibition threshold value.

The embodiments of the present invention have been described above. However, the above embodiments are illustrative, and the configurations of a vehicle and a control device to which the present invention can be applied are limited to the configurations of this embodiment. is not. The technical scope of the present invention is determined based on the claims, and all modifications belonging to the scope of the invention described in the claims are included in the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an idle stop vehicle according to the present invention.

FIG. 2 is a flowchart showing control contents when the engine is automatically stopped.

FIG. 3 is a flowchart showing control contents at the time of automatic engine restart.

FIG. 4 is a flowchart for determining a shift to an idle stop prohibition mode.

FIG. 5 is a map for calculating an I / S prohibition threshold value.

FIG. 6 is a map for calculating an assist torque by a motor generator.

FIG. 7 is a timing chart for explaining the operation of the present invention.

FIG. 8 is a schematic configuration diagram of an idle stop vehicle according to a second embodiment.

FIG. 9 is a flowchart for determining a shift to an idle stop prohibition mode.

FIG. 10 is a timing chart for explaining the operation of the second invention.

[Explanation of symbols]

 Reference Signs List 1 engine 2 motor generator 4, 4 'forward / reverse switching mechanism 5 continuously variable transmission mechanism 7 drive wheel 8 battery 9 inverter 11 brake sensor 12 accelerator sensor 13 road surface gradient sensor 14 navigation system 15 controller

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B60L 11/14 (72) Inventor Hiroaki Daikin 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. 72) Inventor Taiyo Yoshino 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa F-term (reference) 3G092 AA01 AC02 AC03 CA01 EA09 EA14 FA03 FA30 GA04 GB01 HE01Z HE03Z HE08Z HF08Z HF15Z HF26Z HG03Z AA00 BA22 CA04 CB00 CB05 DA01 DA05 DA06 DA07 DB00 DB06 DB10 DB11 DB15 DB18 EB00 FA11 FB05 5H115 PG04 PI16 PU08 PU25 PV09 QE10 QI04 QN12 RB08 RE01 RE05 SE05 SE08 SJ12 SJ13 TO07 TO21 TO23

Claims (8)

[Claims] 1. An engine, a drive wheel driven by the engine, a continuously variable transmission interposed between the engine and the drive wheel, and the engine when a vehicle is stopped and a predetermined idle stop condition is satisfied. An idle-stop vehicle comprising: an idle-stop means for automatically stopping the idle stop; a means for calculating a speed ratio of the continuously variable transmission; and an idle-stop when the calculated speed ratio is smaller than a predetermined threshold value. Idle stop prohibiting means for prohibiting automatic stop of the engine by the means. 2. The apparatus according to claim 1, further comprising: means for detecting a road surface gradient at a position of the own vehicle; and means for calculating the predetermined threshold value based on the detected road surface gradient. Idle stop vehicle. 3. The vehicle according to claim 1, further comprising: means for estimating a starting load at the own vehicle position; and means for calculating the predetermined threshold value based on the estimated starting load. Idle stop vehicle. 4. A motor capable of transmitting a driving force to the driving wheel, and means for assisting the driving force with the motor when the engine is restarted when the idle stop prohibiting means prohibits the automatic stop of the engine. The idle stop vehicle according to claim 1, wherein: 5. The idle stop vehicle according to claim 4, further comprising means for calculating an assist torque at the time of restart by the motor according to a speed ratio of the continuously variable transmission. 6. The vehicle according to claim 1, further comprising: means for detecting a road surface gradient at the own vehicle position; and means for calculating an assist torque at the time of restart by the motor in accordance with the detected road surface gradient. The idle stop vehicle according to 4 or 5. 7. The system according to claim 1, wherein the continuously variable transmission has a snow mode, and the idle stop prohibiting means does not prohibit the automatic stop of the engine when the snow mode is selected. The idle stop vehicle described. 8. An idle stop prohibiting means provided between the continuously variable transmission and the driving wheels, wherein the idle stop prohibiting means is configured to stop the idle stop while the calculated speed ratio is smaller than the speed ratio corresponding to the first speed. 2. The idle stop vehicle according to claim 1, wherein the automatic stop of the engine by the means is prohibited.