JP2000310326A - Traveling control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an engine side driven by a CVT side at operating an accelerator off without giving a feeling of wrongness caused by an increase of an engine sound or an engine speed at operating the accelerator off when a, rotating speed of the CVT is required to be increased. SOLUTION: An ECU 30 increases a rotation speed of an input side of a CVT 12 to a specified target rotating speed based on a preliminary prepared map at operating an acceleration pedal 36 off. A lock-up clutch 16 for mechanically connecting an engine 10 side and the CVT 12 side is slipped a specified amount by the ECU 30 and only the rotating speed of the CVT 12 is increased to suppress the rotating speed of the engine 10, and a feeling of wrongness caused by increase of an engine sound and an engine speed, an excess engine brake, and the like is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle travel control device, and more particularly to a vehicle equipped with a power source and a continuously variable transmission, which shifts the speed ratio of the continuously variable transmission to a reduction side after an accelerator is turned off. The present invention relates to a travel control device for a vehicle that eliminates discomfort caused by sudden changes in the behavior of a vehicle or a power source when the vehicle is running.

[0002]

2. Description of the Related Art Conventionally, a continuously variable transmission (hereinafter referred to as a CVT-Continuo) capable of continuously controlling the speed ratio of a transmission.
There is a vehicle equipped with usly Variable Transmission-). Since the CVT can perform a smooth shifting operation, when the accelerator is turned off and the driver has no intention of accelerating, the engine side and the driving wheel side (CV
Even when the input shaft (T input shaft) is connected with a clutch or the like, the speed ratio of the CVT is sequentially changed to the maximum reduction speed ratio (Lo), so that the vehicle can continue to run smoothly. At this time, the engine side is driven by the drive wheel side, so that the vehicle speed gradually decreases, that is, a state in which a so-called engine braking force is applied.

[0003] In addition, the smooth shifting operation of the CVT can make full use of the characteristics of the engine to improve exhaust gas and fuel efficiency. This fuel efficiency improvement can be implemented, for example, by a fuel cut device that shuts off fuel to be supplied to the engine until the engine speed falls below a predetermined fuel cut lower limit speed when the vehicle is running at a reduced speed. it can. In such a vehicle, fuel is not consumed at the time of deceleration running that does not require the output of the engine, so that the running fuel efficiency of the vehicle can be improved. Since the effect of improving the running fuel efficiency increases as the fuel cut range increases, it is desired to set the fuel cut lower limit rotational speed as low as possible. To realize this, for example, while fuel supplied to the engine is cut off, a lock-up clutch for mechanically connecting and disconnecting power between the engine and the drive wheels is connected (engaged). The engine is rotated by transmitting the running force of the vehicle to the engine via the lock-up clutch as a state. At this time, if the vehicle is equipped with a CVT, the speed ratio can be easily changed to the Lo side even if the vehicle speed continues to decrease, so that the engine speed is maintained at the fuel cut lower limit speed for a certain period of time. The fuel consumption can be improved by increasing the substantial period in which the fuel can be cut. Further, Japanese Patent Application Laid-Open
Japanese Patent No. 3,315,186 discloses that the target speed of the engine is corrected to increase when the accelerator is turned off, so that the speed ratio of the CVT is forcibly corrected to the deceleration side (increase side) so as to reach the target engine speed. A configuration is disclosed in which the engine speed is included in the fuel cut region for as long a time as possible to further improve fuel efficiency.

[0004]

However, when the control for improving fuel efficiency is performed as described above, the engine speed rapidly increases despite the driver turning off the accelerator. In a vehicle having an engine speed display meter, the pointer of the meter rapidly changes, and accordingly, the engine sound sharply increases, giving rise to a problem that the driver feels great discomfort. As described above, the engine braking force can be represented by the product of the reduction ratio and the engine friction. However, since the engine friction increases as the engine speed increases, the engine braking force increases when the accelerator is turned off. As a result, there is a problem that a shock (pulling forward) due to excessive deceleration occurs and the ride comfort of the vehicle is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a vehicle equipped with a CVT, in which the CVT reduction ratio is controlled to the deceleration side when the accelerator is turned off, the engine noise or deceleration shock at the start of the control. An object of the present invention is to provide a traveling control device for a vehicle that can eliminate a sense of discomfort.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a power source, and is disposed between the power source and a driving wheel so that a gear ratio can be continuously changed. And a continuously variable transmission, in which the power source side is driven by the drive wheel side by turning off an accelerator while the power source side and the drive wheel side are connected via a clutch. In the control device, when the speed ratio of the continuously variable transmission is shifted to the reduction side after the accelerator is turned off, the clutch is slipped to reduce the rotation speed on the power source side from the rotation speed on the continuously variable transmission. It is characterized by.

[0007] According to this configuration, the rotational speed on the power source side is made lower than the rotational speed on the continuously variable transmission side due to slippage of the clutch, so that an increase in the engine rotational speed when the accelerator is turned off can be suppressed. As a result, it is possible to prevent sudden changes in the engine sound and the pointer of the rotation speed display meter, and it is possible to prevent the driver from feeling uncomfortable. Further, by causing the clutch to slip, it is possible to avoid excessive generation of the engine braking force, thereby preventing the ride comfort of the vehicle from being impaired.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 is a conceptual view of the configuration of a vehicle according to an embodiment of the present invention. The vehicle targeted in this embodiment uses an engine 10 as a power source, and has a continuously variable transmission (CV) between the engine 10 and driving wheels (not shown).
T) 12 are arranged. In FIG. 1, a crankshaft 10a of an engine 10 is connected to an input shaft 12a of a belt type CVT 12 via a torque converter 18 having a forward / reverse switching mechanism 14 and a lock-up clutch (clutch) 16. The output shaft 12b of the CVT 12 is connected to driving wheels of the vehicle via a differential gear device or the like (not shown). When the lock-up clutch 16 is mechanically connected (engaged), the torque of the engine 10 can be transmitted to the drive wheels, and the torque of the drive wheels can be transmitted to the engine 10.
Further, when the lock-up clutch 16 is disengaged (disengaged), the engine 10 side and the drive wheels (CVT1) are disengaged.
2) The side is independent (the fluid connection is made by the torque converter 18), and the engine 10 can be driven autonomously without receiving an unnecessary load on the driving wheel side, for example, it is possible to maintain idling rotation. become.

The CVT 12 shown in FIG.
a and a pair of variable pulleys 2 composed of a fixed rotating body 20b
The gear ratio is changed by changing the groove width of the belt 22 around these variable pulleys 20 by changing the groove width of the groove 22 by hydraulic pressure so that the tension is maintained constant. The change speed becomes the shift speed. Accordingly, the hydraulic control for supplying and discharging the actuator 24 for driving the movable sheave in each variable pulley 20 allows
The shift speed can be arbitrarily controlled. In addition, CV
As T, a toroidal type in which a power roller is sandwiched between a pair of disks having a toroidal surface, and the power roller is tilted to change the radius of a point of contact with the disk to change the speed can be used.

Further, the torque converter 18 basically operates the engine 1 even when the vehicle is stopped.
0 is operated intermittently.
The forward / reverse switching mechanism 14 is provided because the rotation direction of the engine 10 is limited to one direction and the CVT 12 does not have a reversing operation mechanism, and is a mechanism mainly composed of a planetary gear mechanism. And a mechanism including a reverse gear and a synchronous connection mechanism.

In order to detect the rotational speeds of the input shaft 12a and the output shaft 12b, rotational speed sensors 26 and 2 are provided, respectively.
8 are provided. These rotation speed sensors 26, 28
Is connected to an electronic control unit (hereinafter, referred to as ECU) 30 mainly composed of a microcomputer,
The ECU 30 calculates the gear ratio of the CVT 12 based on the detection signals of the rotation speed sensors 26 and 28.

An intake pipe of the engine 10 is provided with an air amount sensor 32 for detecting an intake air amount, and a rotation sensor 34 for detecting an engine rotation speed is provided near the crankshaft 10a. The ECU 30 optimally controls the fuel injection amount and the ignition timing according to the intake air amount detected by the air amount sensor 32 and the engine speed detected by the rotation sensor 34.

On the other hand, near the accelerator pedal 36, an accelerator sensor 38 for detecting an accelerator opening is provided, and a detection result is provided to the ECU 30. ECU 30
Is the accelerator opening detected by the accelerator sensor 38,
Based on the vehicle speed detected by the rotation speed sensor 28 and the engine rotation speed detected by the rotation speed sensor 34, the amount of intake air is controlled through the throttle actuator 40 so that, for example, fuel economy is optimized.

The shift lever 42 provided near the driver's seat is provided with a shift sensor 44 for detecting the operating position of the shift lever 42. The ECU 30 controls the drive range and the like detected by the shift sensor 44. Information and vehicle speed,
The lock-up clutch 1
6 and the gear ratio of the CVT 12 are controlled.

Further, a brake pedal sensor 48 for detecting the operation amount and operation speed of the brake pedal is provided near the brake pedal 46. The brake pedal sensor 48 is arranged on the brake pedal bracket, and outputs a voltage proportional to the amount of depression of the brake pedal as an EC.
Provide to U30.

A fuel cut device (computer) 50 is further connected to the ECU 30. The fuel cut device 50 uses the lock-up clutch 16 during deceleration traveling of the vehicle to mechanically connect the CVT 12 rotating by driving of drive wheels and the engine 10 to the predetermined vehicle traveling state. This shuts off the fuel supplied to the vehicle. Here, the vehicle running state is, for example, a predetermined fuel cut lower limit value (for example, when determined by an engine speed, 500
rpm, vehicle speed, 15 km / h, etc.).
Thus, the fuel cut device 50 is connected to the engine 10
The fuel consumption of the vehicle is improved by preventing the fuel from being consumed during the deceleration running that does not require the output of the vehicle. Note that the ECU 30 turns off the accelerator pedal 36 so as to maintain the engine speed at or above a predetermined value in order to make the fuel cut possible period as long as possible.
During operation, the reduction ratio of the CVT 12 is continuously increased (L
(shift to the o-side). When the state of the engine 10 becomes equal to or lower than the fuel cut lower limit, the fuel cut device 50 disconnects (releases) the lock-up clutch 16 and releases the engine 10 to the drive wheels (torque). In this state, the fuel injection to the engine 10 is resumed, the engine 10 is driven autonomously, and the idling rotation is maintained. And
When the accelerator pedal 36 is depressed, the ECU 30
Increases the output of the engine 10 and connects the lock-up clutch 16 again to reduce the output of the engine 10 to CVT.
The vehicle is accelerated by transmitting the signal to the drive wheels via the motor 12.

Further, an air conditioner (hereinafter, referred to as an air conditioner) 52, which is an auxiliary device, is connected to the ECU 30 to control the driving thereof. The compressor and the like of the air conditioner 52 are driven by the engine 10. FIG.
In the above, the ECU 30 and the fuel cut device 50 are shown as separate components, but may be configured by a single ECU.

A characteristic feature of this embodiment is that when the accelerator pedal is turned off and the engine 10 is driven by the wheels, the lock-up clutch 16 mechanically connects the engine 10 and the CVT 12. To avoid a rapid increase in the rotation speed of the engine 10 and to prevent engine noise, unnatural changes in the rotation speed display meter, and generation of excessive engine braking force.

FIG. 2 is a flow chart for explaining the control of the vehicle travel control device according to the present embodiment.
FIG. 3A shows the relationship between the vehicle speed and the rotation speed of the engine 10 and the CVT 12, and FIG. 3B shows the change in the engine braking force.

In FIG. 1, the ECU 30 determines whether or not the accelerator pedal 36 is turned off every predetermined time (Δt) (for example, every 16 ms) based on a signal from the accelerator sensor 38 or the like during the running of the vehicle. (S200).
If the accelerator pedal 36 is not OFF, that is, if the driver has turned on the accelerator pedal 36 to accelerate the vehicle or maintain the current speed, the ECU
Reference numeral 30 denotes a current vehicle speed of the vehicle obtained by a rotation speed sensor 28 and the like disposed on the output shaft 12b, and an accelerator sensor 38.
The target rotation speed of the engine 10 is obtained (interpolated) based on the accelerator opening obtained from (S201). And E
The CU 30 calculates the vehicle speed> the lock-up OFF vehicle speed (for example,
It is determined whether or not the speed is 15 km / h) (S202). If the vehicle speed is greater than the lockup OFF vehicle speed, a lockup ON mode (complete engagement) for continuing the connection of the lockup clutch 16 is executed (S203). , The driving force of the engine 10 is mechanically
The control signal is transmitted to the VT 12 to control the running of the vehicle according to the driving state of the engine 10. At this time, the ECU 30 calculates the required fuel injection amount and the opening degree of the throttle actuator 40, and controls, for example, the intake air amount so that fuel efficiency is optimized. The target rotation speed of the engine 10 can be easily determined by using, for example, a map (not shown) indicating the engine rotation speed on the vertical axis and the speed for each accelerator opening on the horizontal axis.

On the other hand, if the vehicle speed is not greater than the lock-up OFF vehicle speed in (S202), that is, if the vehicle speed has been sufficiently reduced, the lock-up clutch 16 is disconnected to connect the engine 10 side to the CVT 12 side. Then, a lock-up OFF mode for turning off the engine 10 and putting the engine 10 into a free state is executed (S204), the engine 10 is brought into an idling state, the driving of the engine 10 is maintained, and a re-acceleration request or the like is prepared.

On the other hand, if the ECU 30 determines in step S200 that the accelerator pedal 36 has been turned off, that is, the driver does not desire to accelerate or maintain the current speed, but instead drives the engine 10 to drive wheels (CVT 12). )), The ECU 3 determines that it wants to perform coasting that is driven by the ECU 3 as shown by the curve a1 in FIG.
0 acquires (interpolates) the target rotation speed on the input side (input shaft 12a side) of the CVT 12 (S205). In this case, the ECU 30 shifts the reduction ratio of the CVT 12 to the reduction side so that the rotation speed on the input side of the CVT 12 increases simultaneously with the operation of turning off the accelerator pedal 36. By shifting the reduction ratio of the CVT 12 to the reduction side in advance when the accelerator pedal 36 is turned off, the reduction ratio of the CVT 12 rapidly shifts to the reduction side when the vehicle decelerates (when no operation is performed on the vehicle). As a result, it is possible to prevent a sudden increase in the engine braking force.

By the way, at this time, if the lock-up clutch 16 is in the engaged state and the engine 10 is completely driven by the CVT 12 directly connected to the driving wheel side,
When the accelerator pedal 36 is turned off, the engine 1
0, the engine speed suddenly increases, the engine noise suddenly increases, and the engine 10 increases with the increase in the engine speed.
Friction rises sharply and excessive engine braking force is generated. Therefore, the ECU 30 determines that the current vehicle speed is vehicle speed> lock-up OFF vehicle speed (for example, 15 km /
h) is determined (S206). If the vehicle speed> the lockup OFF vehicle speed, the lockup clutch 16 is slipped as shown by the curve a2 in FIG. Even so, the target lockup slip ratio is obtained (interpolated) from a target slip ratio map (not shown) so that the rotational speed of the engine 10 does not increase even if the engine 10 is suppressed by the force driven by the CVT 12 (S207). ). Means for changing the slip ratio of the lock-up clutch 16 include, for example, a hydraulic controller that controls the energization of the lock-up clutch 16 so that the difference between the rotation speed of the engine 10 and the rotation speed of the CVT 12 becomes a predetermined value. It can be performed by controlling. The slip ratio (difference) can be appropriately selected depending on the type of vehicle and the like, but is preferably, for example, about 5 to 20%.

By slipping the lock-up clutch 16, as shown in FIG. 3 (a), even if the input-side rotational speed of the CVT 12 suddenly increases, the rotational speed of the engine 10 does not suddenly increase. OF
It is possible to prevent the engine sound from becoming louder during the F operation and to prevent the pointer of the display meter of the engine speed from fluctuating abruptly. Further, even if the accelerator pedal 36 is turned off, the rotational speed of the engine 10 does not increase, so that the friction of the engine 10 does not increase and the engine braking force is excessive as shown by the line b in FIG. This makes it possible to prevent the occurrence of the shock and to prevent a shock due to sudden deceleration or the like when the accelerator pedal 36 is turned off. In addition, CV
Since the speed ratio of T12 is shifted to the deceleration side by increasing the rotation speed when the accelerator pedal 36 is turned off, the speed ratio does not suddenly shift to the deceleration side even when the vehicle speed decreases, and the accelerator pedal 36 is turned off. The engine braking force does not suddenly increase after a lapse of time. Therefore, since an unnatural deceleration / acceleration force is not generated, the driver does not feel uncomfortable. Then the ECU
30 determines whether or not the target slip ratio obtained in (S207) has been reached (S208), and continues the lock-up slip mode until the target slip ratio is reached (S209). If the target slip ratio has been reached, the flow shifts to (S203), and the engine 10
Lock-up ON mode (complete engagement;
Slip = 0) is executed.

On the other hand, if the vehicle speed is not greater than the lock-up OFF vehicle speed in (S206), the lock-up clutch 16 is disconnected to disconnect the engine 10 and the CVT 12 and to set the engine 10 in a free state. The engine 10 is executed (S204) to bring the engine 10 into an idling state to prepare for a re-acceleration request or the like.

As described above, the accelerator pedal 36 can be easily controlled only by controlling the slip ratio of the lock-up clutch 16.
It is possible to prevent a sudden change in the engine sound or the pointer of the engine speed display meter at the time of the OFF operation of the vehicle, thereby preventing the driver from feeling uncomfortable. Furthermore, it is possible to avoid a driver's discomfort and a decrease in the riding comfort of the vehicle due to a sudden increase in the engine braking force.

When the lock-up clutch 16 is slip-controlled during deceleration as in the present embodiment, if a re-acceleration request is made by turning on the accelerator pedal 36 during the control, the lock-up is performed in the first stage. Clutch 1
Since the vehicle 6 slips, acceleration shock can be reduced. For comparison, transition of the engine braking force when the above-described slip control or the like is not performed (engine speed = a1) is shown by a line c in FIG. 3B.

In this embodiment, a vehicle equipped with an engine has been described as an example of a power source. However, the same control can be applied to a vehicle combining an engine and a motor as a drive source. Obtainable.

[0030]

According to the present invention, when the accelerator is turned off, the clutch for mechanically connecting the power source side and the continuously variable transmission is slipped by a predetermined amount. Even when it is necessary to increase the engine speed, it is possible to suppress a sudden change in the engine sound or the pointer of the engine speed display meter, thereby preventing the driver from feeling uncomfortable. Further, by causing the clutch to slip, it is possible to prevent an excessive generation of the engine braking force at the time of the accelerator OFF operation, to reduce a shock or the like at the time of deceleration, and to prevent a reduction in ride comfort of the vehicle.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram illustrating a schematic configuration of a vehicle including a control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a slip ratio control of a lock-up clutch according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating changes in an engine speed, an input-side speed of a CVT, and an engine braking force according to the embodiment of the present invention.

[Explanation of symbols]

10 engine, 12 continuously variable transmission (CVT), 16
Lock-up clutch, 30 ECU, 36 accelerator pedal, 50 fuel cut device.

Claims (1)

[Claims] 1. A power source, a continuously variable transmission disposed between the power source and driving wheels and capable of continuously changing a gear ratio,
A driving control device for a vehicle, wherein the power source side is driven by the driving wheel side when an accelerator is turned off in a state where the power source side and the driving wheel side are connected via a clutch; When the speed ratio of the continuously variable transmission is shifted to the reduction side after being turned off, the clutch is slipped to reduce the rotational speed of the power source side from the rotational speed of the continuously variable transmission. Travel control device.