JPH10196784A - Shift controlling for vehicle continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To only use a portion related to the particular transmission gear ratio of a variable pulley so as to prevent uneven wearing of the pulley by changing a discrete transmission gear ratio according to a car speed in a device for selecting a discrete transmission gear ratio matching a traveling state as a target when a staged shift mode is selected. SOLUTION: An ECU 50 determines which mode is selected, a continuously variable shift mode or a staged shift mode, during vehicle traveling and, if the continuously variable shift mode is selected, a target input shaft rotational speed is decided from a continuously variable shift mode map. On the other hand, if the staged shift mode is selected, then based on a throttle valve opening degree and a car speed detected by a throttle sensor 56 and a second rotation sensor 62, a shift stage is decided by using a shift map and then a discrete transmission gear ratio is calculated. After the discrete transmission gear ratio is decided, the discrete transmission gear ratio is reduce more as a car speed is higher in a normal use area and, if a car speed is increased, the discrete transmission gear ratio is increased again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for a continuously variable transmission for a vehicle.

[0002]

2. Description of the Related Art Conventionally, there is provided a shift control device for a continuously variable transmission for a vehicle for continuously changing the speed of rotation of an engine and transmitting the rotation to drive wheels, wherein one of a continuously variable transmission mode and a stepped transmission mode is manually operated. One having a switch for switching is known.

For example, Japanese Unexamined Patent Publication No. 63-145138 discloses a continuously variable transmission having mode selection means for manually selecting one of a continuously variable transmission mode and a stepped transmission mode.

When the continuously variable transmission mode is selected by the mode selection means, the target rotation speed is determined on the basis of the relationship between the accelerator opening and the target rotation speed, and the engine rotation speed (or the transmission ratio is also determined). In this case, the speed ratio of the continuously variable transmission is controlled such that the same rotation speed (or the same meaning here as the target speed ratio) is equal to the target rotation speed. In the continuously variable transmission mode, the gear ratio is steplessly controlled so that the engine rotation speed is such that the required driving force determined by the accelerator opening and the vehicle speed at that time is most efficiently taken out. Therefore, desired power performance can be realized with the best fuel efficiency.

On the other hand, when the stepped shift mode is selected by the mode selecting means, the shift stage is determined based on the relationship between the accelerator opening and the vehicle speed and each shift stage, and
The gear ratio is set in accordance with the determined gear position, and the gear ratio of the continuously variable transmission is controlled so as to be a discrete gear ratio used discretely. In the stepped shift mode, the gear ratio is discretely selected (to about four to five steps) and fixedly controlled in the same manner as in a normal stepped (automatic) transmission. Therefore, on a discretely selected use speed ratio, the engine speed basically changes in accordance with the vehicle speed. Therefore, even when the accelerator pedal is frequently operated, for example, during a traffic jam,
The engine rotation speed does not fluctuate greatly. Also, during acceleration, the engine rotation speed increases as the vehicle speed increases, so that it is possible to drive with less discomfort.

[0006]

However, in the technology disclosed in the above publication, when the driver continues to use the stepped transmission mode, a specific portion of the belt contact surface of the variable pulley of the belt type continuously variable transmission is not used. Will continue to use only
There is a problem that uneven wear occurs in the variable pulley, and as a result, a belt slip occurs at the time of gear shifting, and the durability of the belt decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is intended to prevent uneven wear of a variable pulley when a driver continues to use a stepped shift mode, to suppress belt slip, and to reduce a belt slip. It is an object of the present invention to provide a shift control device for a continuously variable transmission for a vehicle, which can improve the durability of the vehicle.

[0008]

According to the present invention, as shown in FIG. 1, the gist of the present invention is a mode selecting means for manually selecting one of a continuously variable transmission mode and a stepped transmission mode.
When the continuously variable transmission mode is selected by the mode selection means, the speed ratio of the continuously variable transmission is controlled so that the engine speed matches the target rotation speed, while the stepped transmission mode is selected by the mode selection means. In this case, the transmission ratio is discretely used, one of the discrete transmission ratios is selected as a target value according to the traveling state, and the continuously variable transmission is selected so as to match the selected discrete transmission ratio. A transmission control device for a continuously variable transmission for a vehicle, comprising: a transmission ratio control unit that controls a transmission ratio; and a discrete transmission ratio changing unit that changes the discrete transmission ratio in accordance with a vehicle speed. It is a solution.

According to the present invention, when the stepped shift mode is selected, the discrete gear ratio set in accordance with the gear determined based on the relationship between the accelerator opening and the vehicle speed and each gear is set. Since the variable pulley is changed in accordance with the vehicle speed, only the portion of the variable pulley related to a specific speed ratio is used, so that the pulley can be prevented from being unevenly worn.

[0010]

In a preferred embodiment, the discrete gear ratio changing means changes the discrete gear ratio smaller as the vehicle speed increases.

As a result, uneven wear of the variable pulley can be suppressed, noise and fuel consumption at high vehicle speed can be reduced, and acceleration at low vehicle speed can be further improved.

Hereinafter, an example of a more specific embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram schematically showing a shift control device for a continuously variable transmission for a vehicle to which the present invention is applied.

In FIG. 2, a crankshaft 12 of an engine 10 is connected to an input shaft 18 of a belt type continuously variable transmission (CVT) 16 via an electromagnetic clutch 14. CVT
The 16 output shafts 20 are connected to the drive wheels of the vehicle via a differential gear device or the like (not shown). Thereby, the torque of the engine 10 is transmitted to the drive wheels.

The input shaft 18 and the output shaft 2 of the CVT 16
0 is provided with variable pulleys 22 and 24 whose effective diameters are variable. A transmission belt 26 is wound between these variable pulleys 22 and 24. The variable pulleys 22 and 24 are fixedly rotatable bodies 28 and 30 fixed to the input shaft 18 and the output shaft 20, and are movable in the axial direction to the input shaft 18 and the output shaft 22, but are relatively non-rotatable in the rotational direction. And movable rotators 32 and 34 provided.

By changing the thrust applied from the hydraulic cylinders 36 and 38 to the movable rotators 32 and 34, the V-groove width formed between the fixed rotators 28 and 30 and the movable rotators 32 and 34 is changed. That is, the hanging diameter of the belt is changed.

The hydraulic oil in the oil tank 40 is pumped by an oil pump 42 and is regulated to a line oil pressure by a pressure regulating valve 44 controlled by an electronic control unit (ECU) 50. This line oil pressure is supplied via a line oil passage 46 to a secondary hydraulic cylinder 38 that applies thrust to the secondary variable pulley 24.

The ECU 50 (speed ratio control means) controls the flow control valve 48 to supply the hydraulic oil in the line oil passage 46 to the primary hydraulic cylinder 36 to reduce the speed ratio, or The hydraulic oil in the hydraulic cylinder 36 is discharged to the drain to increase the gear ratio, and the CVT 1
6 is controlled.

The intake pipe of the engine 10 has a slot valve 54 which is opened and closed by an accelerator pedal 52 and a throttle sensor 56 for detecting the opening of the slot valve 54.
Is provided. The engine 10 is provided with an engine rotation sensor 58 for detecting an engine rotation speed based on a signal from an ignition circuit or the like.

A first rotation sensor 6 for detecting the rotation speed of the input shaft 18 and the output shaft 20 is provided near the fixed rotating body 28 on the primary side and the fixed rotating body 30 on the secondary side of the CVT 16.
0 and a second rotation sensor 62 are provided. ECU5
0 is the output shaft 2 detected by the second rotation sensor 62
The vehicle speed is calculated from the rotation speed of 0.

Shift lever 6 provided near the driver's seat
4 includes a shift sensor 6 for detecting the operation position.
6 are provided.

A mode changeover switch (mode selection means) 68 for manually selecting between the continuously variable transmission mode and the stepped transmission mode is provided in the vehicle interior.

In the continuously variable transmission mode, the CV is set so that the target input shaft rotation speed determined to operate the engine 10 on the minimum fuel consumption rate curve and the actual input shaft rotation speed coincide.
This is a mode for controlling the gear ratio of T16 steplessly. On the other hand, the stepped shift mode refers to the actual throttle valve opening (accelerator opening) and vehicle speed based on a prepared shift diagram (map), similarly to shift control in a conventional stepped automatic transmission. In this mode, the shift speed is determined based on the relationship with the shift speed, and the speed ratio of the CVT 16 is controlled so as to be set in accordance with the determined shift speed and to be used discretely. The ECU 50 (discrete gear ratio changing means) changes the discrete gear ratio according to the vehicle speed.

Hereinafter, control of the CVT 16 in the continuously variable transmission mode and the stepped transmission mode will be described. This CV
The control of T16 is performed according to the flowchart shown in FIG.
Executed every ms.

In step 100 of FIG. 3, it is determined which of the continuously variable transmission mode and the stepped transmission mode is selected by operating the mode changeover switch 68. If it is determined in step 100 that the continuously variable transmission mode has been selected, in step 110, the continuously variable transmission mode is selected based on the actual throttle valve opening or the actual throttle valve opening and vehicle speed. The target input shaft rotation speed is determined from the shift mode map, and normal stepless shift processing is performed.

If it is determined in step 100 that the stepped transmission mode has been selected, then in step 120, the throttle valve opening Acc is input from the throttle sensor 56 and the second rotation sensor 62 Then, the rotational speed of the output shaft 20 is input to calculate the vehicle speed V.

In the next step 130, a shift speed i is determined using a shift map as shown in FIG. This decision takes into account the current gear stage in addition to the throttle valve opening Acc and the vehicle speed V.

In the next step 140, the gear ratio (discrete gear ratio) R is determined by the following equation (1) using the constants ai and bi set for the gear position i.

R = ai × V + bi (1)

Here, i represents a shift speed, and i = 1, 2,
3, 4 or i = 1, 2, 3, 4, 5, etc.

Here, assuming that the constant ai is negative, as shown in FIG. 5, the higher the vehicle speed, the smaller the discrete speed ratio R is changed. FIG. 6 shows the relationship between the vehicle speed and the engine speed at each shift speed. In FIG. 6, a broken line shows a case where the discrete speed ratio R is constant at each speed, and the vehicle speed and the engine speed are proportional. On the other hand, the solid line shows the case where the discrete speed ratio R is reduced as the vehicle speed increases.
As shown in FIG. 6, when the vehicle speed is the same, the engine speed is low, so that noise and fuel consumption can be reduced particularly at a high vehicle speed, and acceleration performance can be improved at a low vehicle speed.

Alternatively, the discrete speed ratio R may be determined by a quadratic function of the vehicle speed V as shown in the following equation (2), where αi, βi and γi are constants.

R = αi × V ² + βi × V + γi (2)

When the discrete speed ratio R is determined in this manner, as shown in FIG. 7, the discrete speed ratio R decreases as the vehicle speed V increases in the normal use region, and the vehicle speed V further increases. If it does, the discrete speed ratio R increases again.
The reason why the discrete speed ratio R is increased again is that the driving force is emphasized.

Alternatively, more generally, the discrete speed ratio R may be determined by the following equation (3) using an arbitrary function fi.

R = fi (V) (3)

The variable pulleys 22 and 24 of the CVT 16 are controlled with the discrete speed ratio R thus determined as a target value. Therefore, the variable pulleys 24, 24 of the CVT 16 use the variable pulleys 24, 24 in the same stepped speed mode slightly in accordance with the change in the vehicle speed, so that the variable pulleys 22, 24 are not uniformly worn. Will not occur.

In this embodiment, the automatic transmission mode (AT mode) in which the discrete transmission ratio R is automatically switched among the stepped transmission modes has been described. In the case of the manual transmission mode (MT mode), FIG. The process in step 140 is the same as that in the AT mode, except that the process in step 130 is replaced with the gear position instruction by the driver.

In this embodiment, the CVT 16 always responds to the driver's operation in the same manner, so that the driver does not feel uncomfortable. For example, if the entire set of discrete gear ratios is changed according to the service period of the vehicle, etc., the operation of the driver (manual gear shifting, accelerator depression) and the use environment (vehicle speed, road gradient, etc.) are completely the same. Even so, there may be cases where the selected stepped gear ratios are not the same. At this time, some drivers may feel uncomfortable. As a specific example, a flat highway runs at a speed of 100 km /
h, when driving in the stepped transmission mode up to a certain point
Speed, gear ratio 2.53, engine speed 2400 rp
Suppose you were driving at m. Thereafter, it is assumed that, for example, the use period or the traveling distance has reached a certain value, and the gear ratio previously used is automatically shifted. For example, if the gear ratio is increased by 4% to 2.63, the engine speed becomes 2490 rpm. In other words, the same 100km /
Although the vehicle is running at h, the engine speed changes from 2400 rpm to 2490 rpm regardless of the driver's intention.
This change in the engine speed may give a sensitive driver an uncomfortable feeling.

In addition, the determination of the gear ratio of the highest gear in the stepped gear shift is basically based on the standard of the vehicle and the output torque characteristics of the engine, and the fuel consumption (requires a smaller gear ratio) and the driving force (greater The transmission ratio is automatically shifted in accordance with the period of use or mileage, even though the transmission ratio is set to be the best value on two conflicting events (requiring the transmission ratio). This also means that it deviates from its best gear ratio.

In the present embodiment, if the operation of the driver and the use environment are the same, the gear ratio used throughout the entire use process of the vehicle is the same, so that even a driver with a sharp sense can feel uncomfortable. Therefore, it is possible to set the discrete gear ratio R of the highest gear in the stepped gear shift mode to the best value.

When a characteristic such that the discrete speed ratio R becomes smaller with respect to the vehicle speed as shown in FIG. 5 is given, noise and fuel consumption at high speed can be reduced, and at low vehicle speed, acceleration and starting performance are improved. And the practicability of the stepped transmission mode can be enhanced.

At this time, as shown in FIG. 7, it is possible to set the discrete speed ratio R to be minimum in the normal high-speed range, and to set the emphasis on the acceleration in the higher speed range.

[0044]

As described above, according to the present invention, since the discrete speed ratio set according to the vehicle speed is changed, uneven wear of the variable pulley when the driver continues to use the stepped speed change mode. Can be prevented, and a reduction in belt slip and durability of the belt can be suppressed.

When the discrete gear ratio set with respect to the vehicle speed is reduced, noise and fuel consumption can be reduced in a high vehicle speed range, and acceleration and startability can be improved in a low vehicle speed range. Can be. Further, since the continuously variable transmission always responds the same to the driver's operation, the driver does not feel uncomfortable.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the gist of the present invention.

FIG. 2 is a configuration diagram schematically showing a shift control device for a continuously variable transmission for a vehicle to which the present invention is applied;

FIG. 3 is a flowchart showing control in a continuously variable transmission mode and a stepped transmission mode in the present embodiment.

FIG. 4 is a map for determining a shift speed from an accelerator opening and a vehicle speed.

FIG. 5 is a diagram showing a state where the discrete gear ratio is changed to be smaller as the vehicle speed is higher.

FIG. 6 is a diagram showing the relationship between the vehicle speed and the engine speed when the discrete gear ratio is reduced as the vehicle speed increases.

FIG. 7 is a diagram showing a state in which the vehicle speed has been changed so that the discrete speed ratio is minimized in a normal use range.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Engine 12 ... Crankshaft 14 ... Electromagnetic clutch 16 ... Belt-type continuously variable transmission (CVT) 18 ... Input shaft 20 ... Output shaft 20, 24 ... Variable pulley 26 ... Transmission belt 50 ... Electronic control unit (ECU) 68 ... Mode switch

Claims (2)

[Claims] 1. A mode selection means for manually selecting one of a continuously variable transmission mode and a stepped transmission mode, and when the continuously variable transmission mode is selected by the mode selection means, the engine speed is set to a target value. While the speed ratio of the continuously variable transmission is controlled so as to match the rotation speed, when the stepped speed change mode is selected by the mode selection means, the speed ratio is used discretely, and depending on the traveling state, Speed control means for selecting the discrete speed ratio as a target value and controlling the speed ratio of the continuously variable transmission so as to match the selected discrete speed ratio. A control device for a continuously variable transmission for a vehicle, comprising: a control unit that changes a discrete gear ratio according to a vehicle speed. 2. A transmission control apparatus for a continuously variable transmission for a vehicle according to claim 1, wherein said discrete gear ratio changing means changes said discrete gear ratio to be smaller as the vehicle speed is higher.