JP3637712B2 - Shift control device for continuously variable transmission for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shift control device for a continuously variable transmission for a vehicle.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a transmission control device for a continuously variable transmission for a vehicle that continuously changes the rotation of an engine and transmits it to a drive wheel, and has a switch for manually switching one of a continuously variable transmission mode and a stepped transmission mode. It has been known.
[0003]
For example, Japanese Patent Application Laid-Open No. 63-145138 discloses a continuously variable transmission having mode selection means for manually selecting one of the continuously variable transmission mode and the stepped transmission mode.
[0004]
When the continuously variable transmission mode is selected by the mode selection means, the target rotational speed is determined based on the relationship between the accelerator opening and the target rotational speed, and the engine rotational speed (or the gear ratio here is also synonymous here). The gear ratio of the continuously variable transmission is controlled so as to coincide with the target rotational speed (or the target gear ratio is synonymous here). In the continuously variable transmission mode, the gear ratio is controlled steplessly so that the required driving force determined by the accelerator opening and the vehicle speed at that time is the engine rotational speed at which it is most efficiently extracted. Therefore, the desired power performance can be realized with the best fuel efficiency.
[0005]
On the other hand, when the stepped speed change mode is selected by the mode selection means, the speed stage is determined based on the relationship between the accelerator opening, the vehicle speed, and each speed stage, and the speed ratio is determined. The transmission ratio of the continuously variable transmission is controlled so as to be a discrete transmission ratio that is set according to In the stepped transmission mode, the gear ratio is selected and fixed in a discrete manner (about 4 to 5 steps) in the same manner as a normal stepped (automatic) transmission. Therefore, on the use gear ratio selected discretely, the engine rotation speed basically changes in correspondence with the vehicle speed. For example, even when the accelerator pedal is frequently operated, such as during a traffic jam, The engine speed does not fluctuate greatly, and at the time of acceleration, the engine speed increases as the vehicle speed increases, so that it is possible to drive with less discomfort.
[0006]
[Problems to be solved by the invention]
However, in the one disclosed in the above publication, if the driver continues to use the stepped speed change mode, only a specific part of the belt contact surface of the variable pulley of the belt type continuously variable transmission will continue to be used. There is a problem that uneven wear occurs in the pulley, and as a result, belt slip occurs at the time of shifting and the durability of the belt decreases.
[0007]
The present invention has been made in view of the above-described conventional problems, and prevents uneven wear of the variable pulley when the driver continues to use the stepped transmission mode, suppresses belt slip, and durability of the belt. It is an object of the present invention to provide a shift control device for a continuously variable transmission for a vehicle capable of improving the above.
[0008]
[Means for Solving the Problems]
As the gist of the present invention is shown in FIG. 1, the mode selection means for manually selecting one of the continuously variable transmission mode and the stepped transmission mode, and the continuously variable transmission mode is selected by the mode selection means. In this case, the transmission ratio of the continuously variable transmission is controlled so that the engine rotation speed matches the target rotation speed. A transmission ratio control means that selects one of the discrete transmission ratios as a target value in accordance with a running state and controls the transmission ratio of the continuously variable transmission so as to match the selected discrete transmission ratio; In the transmission control device for a continuously variable transmission for a vehicle, the above-described problem is solved by providing discrete gear ratio changing means for changing the discrete gear ratio according to the vehicle speed.
[0009]
According to the present invention, when the stepped speed change mode is selected, the discrete speed ratio set according to the speed determined based on the relationship between the accelerator opening and the vehicle speed and each speed is changed to the vehicle speed. Since the change is made accordingly, only the portion of the variable pulley related to a specific gear ratio is used, and the pulley can be prevented from being unevenly worn.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment, the discrete gear ratio changing means changes the discrete gear ratio smaller as the vehicle speed increases.
[0011]
As a result, uneven wear of the variable pulley can be suppressed, noise and fuel consumption at a high vehicle speed can be reduced, and acceleration at a low vehicle speed can be improved.
[0012]
Hereinafter, an example of a more specific embodiment of the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 2 is a block diagram showing an outline of a shift control device for a continuously variable transmission for a vehicle to which the present invention is applied.
[0014]
In FIG. 2, the crankshaft 12 of the engine 10 is connected to an input shaft 18 of a belt type continuously variable transmission (CVT) 16 via an electromagnetic clutch 14. The output shaft 20 of the CVT 16 is connected to drive wheels of the vehicle via a differential gear device or the like (not shown). Thereby, the rotational force of the engine 10 is transmitted to the drive wheels.
[0015]
The input shaft 18 and the output shaft 20 of the CVT 16 are provided with variable pulleys 22 and 24 having variable effective diameters. A transmission belt 26 is wound around the variable pulleys 22 and 24. The variable pulleys 22 and 24 are fixed to the input shaft 18 and the output shaft 20, and can be moved in the axial direction with respect to the input shaft 18 and the output shaft 22, but cannot be relatively rotated in the rotation direction. The movable rotating bodies 32 and 34 provided are provided.
[0016]
By changing the thrust applied to the movable rotating bodies 32 and 34 from the hydraulic cylinders 36 and 38, a V-groove width formed between the fixed rotating bodies 28 and 30 and the movable rotating bodies 32 and 34, that is, a belt. The hanging diameter is changed.
[0017]
The hydraulic oil in the oil tank 40 is pumped by an oil pump 42 and is regulated to a line hydraulic pressure by a pressure regulating valve 44 controlled by an electronic control unit (ECU) 50. The 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.
[0018]
The ECU 50 (transmission ratio control means) controls the flow rate control valve 48 to supply hydraulic oil in the line oil passage 46 to the primary hydraulic cylinder 36 to reduce the transmission ratio, or the hydraulic cylinder 36. The hydraulic oil in the cylinder is discharged to the drain to increase the gear ratio, and the gear ratio of the CVT 16 is controlled.
[0019]
The intake pipe of the engine 10 is provided with a slot valve 54 that is opened and closed by an accelerator pedal 52 and a throttle sensor 56 that detects the opening degree of the slot valve 54. The engine 10 is provided with an engine rotation sensor 58 for detecting the engine rotation speed based on a signal from an ignition circuit or the like.
[0020]
In the vicinity of the primary fixed rotating body 28 and the secondary fixed rotating body 30 of the CVT 16, a first rotation sensor 60 and a second rotation sensor 62 for detecting the rotation speeds of the input shaft 18 and the output shaft 20. Is provided. The ECU 50 calculates the vehicle speed from the rotation speed of the output shaft 20 detected by the second rotation sensor 62.
[0021]
The shift lever 64 provided in the vicinity of the driver's seat is provided with a shift sensor 66 for detecting the operation position.
[0022]
Further, a mode changeover switch (mode selection means) 68 for manually selecting and operating the continuously variable transmission mode and the stepped transmission mode is provided in the vehicle interior.
[0023]
In the continuously variable transmission mode, the gear ratio of the CVT 16 is continuously controlled so that the target input shaft rotational speed determined so as to operate the engine 10 on the minimum fuel consumption rate curve matches the actual input shaft rotational speed. Mode. On the other hand, the stepped transmission mode refers to the actual throttle valve opening (accelerator opening), the vehicle speed, and the vehicle speed from the shift diagram (map) prepared in advance, similarly to the shift control in the conventional stepped automatic transmission. In this mode, the gear stage is determined based on the relationship with the gear stage, and the gear ratio of the CVT 16 is controlled so that the discrete gear ratio is set according to the determined gear stage and used discretely. The ECU 50 (discrete gear ratio changing means) changes the discrete gear ratio according to the vehicle speed.
[0024]
Hereinafter, the control of the CVT 16 in the continuously variable transmission mode and the stepped transmission mode will be described. The control of the CVT 16 is executed every 10 ms along the flowchart shown in FIG.
[0025]
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 is selected, in step 110, the continuously variable transmission mode is determined based on the actual throttle valve opening, or based on the actual throttle valve opening and the vehicle speed. The target input shaft rotational speed is determined from the shift mode map, and a normal continuously variable transmission process is performed.
[0026]
If it is determined in step 100 that the stepped speed change mode is selected, in the next step 120, the throttle valve opening Acc is input from the throttle sensor 56, and the output shaft is output from the second rotation sensor 62. A rotational speed of 20 is input to calculate the vehicle speed V.
[0027]
In the next step 130, a shift stage i is determined using a shift map as shown in FIG. This determination takes into account the current gear stage in addition to the throttle valve opening Acc and the vehicle speed V.
[0028]
In the next step 140, a gear ratio (discrete gear ratio) R is determined by the following equation (1) using constants ai and bi set corresponding to the gear stage i.
[0029]
R = ai × V + bi (1)
[0030]
Here, i represents a gear position, i = 1, 2, 3, 4 or i = 1, 2, 3, 4, 5, etc.
[0031]
Here, if the constant ai is negative, as shown in FIG. 5, the discrete speed ratio R is changed smaller as the vehicle speed increases. FIG. 6 shows the relationship between the vehicle speed and the engine speed at each gear stage. In FIG. 6, the broken line indicates a case where the discrete gear ratio R is constant at each gear stage, and the vehicle speed and the engine speed are proportional. On the other hand, the solid line shows the case where the discrete gear ratio R is reduced as the vehicle speed increases. As shown in FIG. 6, since the engine speed is low at the same vehicle speed, noise and fuel consumption can be reduced particularly at high vehicle speeds, and acceleration performance can be enhanced at low vehicle speeds.
[0032]
Also, the discrete speed ratio R may be determined by a quadratic function of the vehicle speed V, as shown in the following equation (2), with αi, βi and γi as constants.
[0033]
R = αi × V ² + βi × V + γi (2)
[0034]
When the discrete gear ratio R is determined in this way, as shown in FIG. 7, when the vehicle speed V is higher in the normal use range, the discrete gear ratio R decreases and the vehicle speed further increases as the vehicle speed increases. Then, the discrete speed ratio R increases again. The reason why the discrete gear ratio R is increased again is because the driving force is emphasized.
[0035]
Or more generally, the discrete transmission gear ratio R may be determined by the following equation (3) using an arbitrary function fi.
[0036]
R = fi (V) (3)
[0037]
The variable pulleys 22 and 24 of the CVT 16 are controlled with the discrete gear ratio R thus determined as a target value. Accordingly, the use location of the variable pulleys 24 and 24 of the CVT 16 slightly changes according to the change in the vehicle speed even in the same stepped gear mode, so that the variable pulleys 22 and 24 are subject to uneven wear. It does not occur.
[0038]
In the present embodiment, the automatic transmission mode (AT mode) that automatically switches the discrete transmission ratio R among the stepped transmission modes has been described. However, in the case of the manual transmission mode (MT mode), step 130 in FIG. The processing in step 140 is replaced with the gear speed instruction from the driver, and the processing in step 140 is the same as in the AT mode.
[0039]
In the present embodiment, the CVT 16 always responds the same to the driver's operation, so the driver does not feel uncomfortable. For example, when the entire set of discrete gear ratios is changed according to the period of use of the vehicle, the driver's operations (manual shift, accelerator depression) and the usage environment (vehicle speed, road gradient, etc.) are exactly the same. Even in such a case, the selected stepped gear ratio may not be the same. At this time, some drivers may feel uncomfortable. As a specific example, when driving on a flat highway at a vehicle speed of 100 km / h, until a certain point, it was running at 5 gears in stepped transmission mode with a gear ratio of 2.53 and an engine speed of 2400 rpm. To do. After that, for example, assuming that the use period or the travel distance reaches a certain value, it is assumed that the gear ratio that has been used is automatically shifted. For example, if the gear ratio is increased by 4% to 2.63, the engine speed is 2490 rpm. That is, the engine speed changes from 2400 rpm to 2490 rpm regardless of the driver's intention even though the vehicle is traveling on the same road at 100 km / h. This change in engine speed may give the driver a sense of discomfort.
[0040]
This also means that the determination of the gear ratio of the top step of the stepped transmission is based on the vehicle specifications and the engine output torque characteristics, and the fuel efficiency (requires a smaller gear ratio) and driving force (the larger gear ratio). Although it is set to be the best value on two conflicting events (request), the gear ratio is automatically shifted according to the period of use, travel distance, etc. It also means that it will deviate from the best gear ratio.
[0041]
In this embodiment, if the driver's operation and the use environment are the same, the gear ratio used throughout the entire use process of the vehicle will be the same, so it will not give a sense of incongruity to a sharp driver, It becomes possible to set the discrete speed ratio R at the highest stage in the stepped speed change mode to the best value.
[0042]
Further, when the characteristic of the discrete gear ratio R to be reduced with respect to the vehicle speed as shown in FIG. In addition, the practicality of the stepped transmission mode can be enhanced.
[0043]
At this time, as shown in FIG. 7, it is possible to minimize the discrete gear ratio R in the normal high speed region, and to set acceleration with emphasis on acceleration in higher speed regions.
[0044]
【The invention's effect】
As described above, according to the present invention, the discrete gear ratio set according to the vehicle speed is changed, so that it is possible to prevent uneven wear of the variable pulley when the driver continues to use the stepped transmission mode. It is possible to suppress belt slip and a decrease in belt durability.
[0045]
When the discrete gear ratio set for the vehicle speed is reduced, noise and fuel consumption can be reduced at high vehicle speeds, and acceleration and startability can be improved at low vehicle speeds. In addition, since the continuously variable transmission always responds 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 showing an outline of a shift control device for a continuously variable transmission for a vehicle to which the present invention is applied. FIG. 3 is a continuously variable transmission mode in the present embodiment. FIG. 4 is a map for determining the gear position from the accelerator opening and the vehicle speed. FIG. 5 is a diagram showing how the discrete gear ratio is changed smaller as the vehicle speed increases. 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 shows the vehicle speed changed so that the discrete gear ratio becomes the smallest in the normal use range. Diagram [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Engine 12 ... Crankshaft 14 ... Electromagnetic clutch 16 ... Belt type continuously variable transmission (CVT)
DESCRIPTION OF SYMBOLS 18 ... Input shaft 20 ... Output shaft 20, 24 ... Variable pulley 26 ... Transmission belt 50 ... Electronic control unit (ECU)
68. Mode selector switch

Claims (2)

Mode selection means for manually selecting one of the continuously variable transmission mode and the stepped transmission mode, and when the continuously variable transmission mode is selected by the mode selection means, the engine rotational speed matches the target rotational speed. When the step-variable transmission mode is selected by the mode selection means, the transmission ratio is discretely used, and one of the discrete transmission ratios is selected according to the driving state. A transmission ratio control means for controlling the transmission ratio of the continuously variable transmission so as to coincide with the selected discrete transmission ratio, and a transmission control device for a continuously variable transmission for a vehicle,
A shift control apparatus for a continuously variable transmission for a vehicle, comprising: discrete gear ratio changing means for changing the discrete gear ratio according to a vehicle speed. 2. The transmission control apparatus for a continuously variable transmission for a vehicle according to claim 1, wherein the discrete gear ratio changing means changes the discrete gear ratio smaller as the vehicle speed is higher.

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