JP4439212B2 - Shift control method for continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shift control method for a V-belt continuously variable transmission for a vehicle.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 4-244661 [Patent Document 2]
In general, in a transmission control method for a continuously variable transmission, a target input rotation speed is searched according to a shift pattern from a throttle opening (accelerator opening) and a vehicle speed, and the rotation speed and the current vehicle speed are searched. It is customary to change gears with a gear ratio determined by (output shaft speed) as a target value. The shift pattern is set such that the larger the throttle opening, the larger the input rotational speed for the same vehicle speed, and the input rotational speed is substantially constant and only the vehicle speed changes at the same throttle opening. Therefore, when accelerating with the throttle opening being constant, only the vehicle speed increases while maintaining the input rotational speed substantially constant.
In a continuously variable transmission having such a shift pattern, the input rotational speed is maintained substantially constant even when the allowable maximum speed is exceeded on a downhill or the like, so the peripheral speed of the V belt exceeds the speed limit, and V A problem occurs in the durability and reliability of the belt.
[0003]
In order to solve such a problem, Japanese Patent Application Laid-Open No. H10-228688 discloses a shift set so that when the vehicle exceeds a predetermined vehicle speed that is close to the maximum allowable speed, the target input rotation speed is lower than when the vehicle is below the predetermined vehicle speed. There has been proposed a method of shifting with a pattern.
FIG. 6 is a shift pattern diagram shown in Patent Document 1. In FIG.
As shown in FIG. 6, the target input rotational speed is set in accordance with the throttle opening TH, and if the throttle opening is kept constant, only the vehicle speed increases while maintaining the input rotational speed substantially constant. To go. However, when the vehicle speed exceeds V2 due to a downhill or the like, the input rotational speed rapidly decreases to N1, and the peripheral speed of the V belt also decreases, so that it is prevented that the speed limit Cv of the V belt is exceeded.
[0004]
[Problems to be solved by the invention]
However, even if the speed change control method as described above is performed, the peripheral speed of the V-belt may exceed the speed limit.
For example, as shown in Patent Document 2, a vehicular continuously variable transmission is known in which a power intermittent clutch such as a starting clutch is provided downstream of a belt-type transmission having a drive pulley and a driven pulley. In the case of such a continuously variable transmission in which a clutch is provided on the output shaft system, if the clutch is disengaged and the accelerator pedal is depressed, the peripheral speed of the V belt cannot be limited. This is because in such a continuously variable transmission, the driven pulley and the output shaft are not connected when the clutch is disengaged, so that the driven pulley can freely rotate and the peripheral speed of the V-belt increases as the engine speed increases. Because it will do. In particular, when the gear ratio is high, the peripheral speed of the V belt wound around the driven pulley exceeds the speed limit.
For example, in FIG. 6, when the vehicle speed is Vx lower than V2 and the throttle opening TH = 4/4, the target input rotational speed is Nx and the target gear ratio is Rx. At this time, assuming that the engine speed of the engine is Ny, the peripheral speed of the V-belt greatly exceeds the speed limit Cv.
In the clutch disengaged state, almost no load is applied to the V belt. The no-load V-belt speed limit Cv ′ is higher than the loaded speed limit Cv ′, but the peripheral speed of the V-belt may still exceed the speed limit Cv ′.
[0005]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a continuously variable transmission having a clutch in an output shaft system, which can limit the peripheral speed of the V-belt within a limit value when the clutch is disengaged and the accelerator pedal is depressed. It is to provide a control method.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is directed to a belt-type transmission in which a drive pulley is connected to an engine, a driven pulley is connected to an output shaft, and a gear ratio can be changed steplessly, and the driven In a transmission control method for a continuously variable transmission comprising a power intermittent clutch provided between a pulley and an output shaft, a step of detecting a vehicle speed from the rotational speed of the output shaft, and an input rotation of the transmission A step of detecting a number, a step of detecting that the clutch is in an asynchronous state from an input rotational speed and an output rotational speed of the clutch, a step of detecting depression of an accelerator pedal, clutch is asynchronous condition, and when the accelerator pedal is depressed, the variable and obtaining a target speed ratio from the detected vehicle speed and the input rotational speed, a proximity value of the target gear ratio as a target value Providing a step of speed change control device, a shift control method for a continuously variable transmission, characterized in that it comprises a.
[0007]
In a continuously variable transmission having a clutch in the output shaft system, the clutch is in an asynchronous state (the input speed of the clutch is different from the output speed) and when the accelerator pedal is depressed, the driven pulley and the output shaft Are not connected to each other, so the engine speed (input speed) increases rapidly. In particular, when the gear ratio is on the high side, the peripheral speed of the V belt wound around the driven pulley may exceed a limit value.
Therefore, in the present invention, when the clutch is in an asynchronous state and the accelerator pedal is depressed, the target gear ratio is obtained from the vehicle speed (output shaft rotational speed) and the input rotational speed (engine rotational speed), and the target value Shift control is executed using the vicinity value as a target value. Since the output shaft and the driven pulley are not connected, the vehicle speed does not correspond to the rotational speed of the driven pulley, but the vehicle speed does not change abruptly, so shift control is performed using the vehicle speed and the input rotation speed. For example, the gear ratio can be controlled as low as possible, and the peripheral speed of the V-belt can be prevented from exceeding the speed limit.
Even when the clutch changes from an asynchronous state to a synchronous state, since the gear ratio is maintained in the vicinity of the gear ratio corresponding to the vehicle speed and the input rotation speed in advance, a sudden engine braking phenomenon occurs when the clutch is reengaged. And over-rotation of the engine can be avoided.
[0008]
When the clutch is in the engaged state (synchronized state), the target input rotational speed or the target speed ratio may be obtained from the accelerator opening and the vehicle speed in the same manner as before, and the shift control may be performed toward this target value. The target value is preferably set so as not to exceed the input rotational speed or the gear ratio determined from the belt peripheral speed limit corresponding to the vehicle speed at that time.
Furthermore, when the clutch is in an asynchronous state and the accelerator pedal is not depressed, the V-belt peripheral speed may not exceed the speed limit. Therefore, the same control as that during clutch synchronization may be performed. In addition, the same control as in the state where the accelerator pedal is depressed may be performed. Furthermore, the larger input rotation speed or gear ratio of the two controls may be set as the target value.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to examples.
1 and 2 show an example of a continuously variable transmission according to the present invention.
The continuously variable transmission of this embodiment is an FF horizontal type automobile transmission, which is roughly an input shaft 3 driven via a torsional damper 2 by an engine output shaft 1 and a drive shaft that supports a drive pulley 11. 10, a driven shaft 20 that supports the driven pulley 21, a drive pulley 11 and a V belt 15 wound around the driven pulley 21, a first reduction shaft 30, a second reduction shaft 31, an output shaft 32 connected to wheels, and a speed change Motor 40, tension device 50, and the like. The driving pulley 11, the driven pulley 21, and the V belt 15 constitute a belt type transmission in the present invention.
The V-belt 15 used in this embodiment is a known dry type composite belt composed of a pair of endless tension bands and a large number of blocks locked to the tension bands in the length direction.
[0010]
The drive pulley 11 includes a fixed sheave 11a fixed on the drive shaft 10, a movable sheave 11b supported on the drive shaft 10 so as to be movable in the axial direction, and a stroke mechanism 12 provided behind the movable sheave 11b. I have. The stroke mechanism 12 of this embodiment is a ball screw mechanism that moves the movable sheave 11b in the axial direction by rotational input from the speed change motor 40. The female screw member 12b is supported on the movable sheave 11b via a bearing 12a so as to be relatively rotatable. And a male screw member 12c fixed to the housing, and a transmission gear 13 is fixed to the outer periphery of the female screw member 12b.
[0011]
The driven pulley 21 includes a fixed sheave 21a fixed on the driven shaft 20, a movable sheave 21b supported on the driven shaft 20 so as to be axially movable, and a stroke mechanism 22 provided behind the movable sheave 21b. I have. This stroke mechanism 22 is also a ball screw mechanism having the same configuration as the stroke mechanism 12 of the drive pulley 11, a female screw member 22 b supported by the movable sheave 21 b through a bearing 22 a so as to be relatively rotatable, and a male screw fixed to the housing. The transmission gear 23 is fixed to the outer peripheral portion of the female screw member 22b.
[0012]
A forward / reverse switching mechanism 24 is provided at a position closer to the engine than the driven pulley 21 of the driven shaft 20, and a forward gear 25 and a reverse gear 26 are rotatably supported on both sides thereof. When the forward / reverse switching mechanism 24 is shifted to the left in FIG. 1, the forward (D) position is set, and when the right / left switching mechanism 24 is shifted to the right, the reverse (R) position is set. A start clutch 27 is provided at the shaft end of the driven shaft 20 on the engine side, and the start clutch 27 connects and disconnects the hub 24 a of the forward / reverse switching mechanism 24 to the driven shaft 20. The forward gear 25 is engaged with the gear 30a of the first reduction shaft 30, the gear 30b of the first reduction shaft 30 is engaged with the gear 31a of the second reduction shaft 31, and the gear 31b of the second reduction shaft 31 is further connected to the differential device 33. Is engaged with the ring gear 33a. Further, the reverse gear 26 meshes with the gear 30 b of the first reduction shaft 30 through the idler gear 28. And the output shaft 32 connected with the wheel via the differential device 33 is driven.
[0013]
The output gear 41 of the speed change motor 40 is meshed with a reduction gear 45 a provided at one end of the first speed change shaft 45. A gear 45 b provided at the other end of the first transmission shaft 45 is a spur gear having a length corresponding to the moving stroke of the movable sheave 21 b of the driven pulley 21, and meshes with the transmission gear 23 provided on the driven pulley 21. Yes. When the gear 45b of the first speed change shaft 45 is rotated, the speed change gear 23 is rotated so that the movable sheave 21b can be moved in the axial direction by the action of the ball screw mechanism 22. The transmission gear 23 of the driven pulley 21 meshes with the first idler gear 46 a of the second transmission shaft 46, and the second idler gear 46 b of the second transmission shaft 46 meshes with the transmission gear 13 of the drive pulley 11. These idler gears 46a and 46b are also constituted by spur gears having a length corresponding to the moving stroke of the movable sheaves 11b and 21b, similarly to the gear 45b of the first transmission shaft 45. The rotational force of the speed change motor 40 is transmitted to the speed change gear 13 of the drive pulley 11 via the first speed change shaft 45, the speed change gear 23 of the driven pulley 21, and the second speed change shaft 46. Therefore, the movable sheave 11a of the driving pulley 11 and the movable sheave 21a of the driven pulley 21 are synchronized with each other, and can move in the axial direction while changing the pulley groove width (belt winding diameter) in the opposite direction.
[0014]
As shown in FIG. 2, the continuously variable transmission is provided with a mechanism that applies belt tension necessary for torque transmission to the V-belt 15, that is, a tension device 50.
As described above, the pulley groove width (belt wrapping diameter) of the pulleys 11 and 21 is varied by the speed change motor 40, but only that causes slippage between the V belt 15 and the pulleys 11 and 21 due to the transmission torque. End up. Therefore, a tension device 50 is provided to apply a belt tension that does not cause the V belt 15 to slip. The tension device 50 includes a tension roller 51, and this tension roller 51 is supported by a tension arm 53 through a link 52 so as to be swingable.
[0015]
A rotating shaft 53 a of the tension arm 53 is provided on the outer side in the radial direction of the drive pulley 11 and is urged toward the V-belt 15 by a tension spring 54. Therefore, the tension roller 51 presses the loose side of the V-belt 15 inward with a predetermined load. By pressing the V-belt 15 from the outside to the inside in this way, a predetermined belt tension is obtained, and the winding length of the V-belt 15 around the pulleys 11 and 21 is lengthened to increase the transmission efficiency.
Note that the tension roller 51 is not limited to pressing the V-belt 15 from the outside to the inside, but may be pressed from the inside to the outside.
Further, although the tension roller 51 is attached to the arm 53 via the link 52, the tension roller 51 may be directly attached to the arm 53 so as to be freely rotatable.
The tension device 50 of the above embodiment uses the tension spring 54. However, as disclosed in JP 2001-330097 A, the tension device 50 may include an assist motor in addition to the tension spring. A combination of a tension spring and a compression spring may be used as in JP 2002-213549 A. Further, an actuator such as a hydraulic cylinder may be used instead of the assist motor.
[0016]
FIG. 3 shows a control device 60 for controlling the starting clutch 27 and the speed change motor 40.
The controller 60 receives the engine speed (the speed of the input shaft 3), the vehicle speed (the speed of the output shaft 32), the accelerator opening, the speed of the driven shaft 20, a shift position signal, and the like. A shift map or the like is set in the control device 60, a target gear ratio is calculated according to the input signal, and the shift motor 40 is controlled to perform shift control.
The start clutch 27 is controlled to be connected and disconnected by a clutch control actuator 61. The actuator 61 is configured by a known linear solenoid valve, a duty solenoid valve, or a combination of a duty solenoid valve and a hydraulic control valve. The actuator 61 adjusts the clutch hydraulic pressure in accordance with an electric signal, and increases the transmission torque of the start clutch 27. Control. A control map of the starting clutch 27 is also set in the control device 60, and the starting clutch 27 is controlled according to the input signal.
[0017]
The starting clutch 27 is subjected to slip control at the time of starting to realize a smooth starting. In addition, it is normally maintained in an engaged state during traveling, but is interrupted when the shift lever is shifted to the N range even during traveling. In particular, since the starting clutch 27 is provided on the downstream side of the driven pulley 21, even when the belt-type transmission does not return to the low position where it can restart at the time of sudden deceleration, the starting clutch 27 is cut off to drive the clutch. Since the pulley 11 and the driven pulley 21 can be idled by the engine, it can be easily returned to the Low position. The starting clutch 27 is also disconnected when switching between forward and reverse travel.
[0018]
The control device controls the speed changing motor 40 according to the following control law.
(1) A target input rotational speed Nin is obtained from the accelerator opening during clutch synchronization and the vehicle speed, and shift control is performed using this target input rotational speed as a target value. However, the upper limit is set so that the target input speed Nin does not exceed the limit input speed Ncv obtained from the belt peripheral speed limit Cv and the vehicle speed. Therefore, the peripheral speed of the V belt does not exceed the belt peripheral speed limit, and the durability reliability of the V belt is not lowered.
Note that a gear ratio may be used as the target value instead of the input rotation speed.
(2) The target speed ratio Ry is obtained from the actual vehicle speed and the actual input speed (= actual engine speed) when the clutch is not synchronized and the accelerator is ON, and the speed change control is performed so that the target speed ratio Ry is close to the target speed ratio Ry. To do.
The vicinity value of the target speed ratio Ry may be obtained, for example, by adding a predetermined value α (0 or more) to the actual vehicle speed and using the vehicle speed and the actual input rotational speed. The reason why the positive value α is added in this way is to prevent sudden engine braking when the clutch 27 is re-engaged and engine over-rotation (over-rev).
Since the driven pulley and the output shaft are not connected when the clutch is asynchronous, the engine speed (input speed) increases rapidly as the accelerator pedal is depressed, and increases to near the limiter speed. When the gear ratio is in the high state, the peripheral speed of the V belt wound around the driven pulley becomes very high, and there is a possibility that the speed limit Cv ′ at no load is exceeded. Therefore, if the speed change control is performed using the target speed ratio Ry obtained from the vehicle speed and the input rotation speed as the target value, the speed ratio can be shifted to the low side, and the increase in the peripheral speed of the V belt wound around the driven pulley is suppressed. Is done.
(3) When the clutch is not synchronized and the accelerator is OFF At this time, the engine speed is low and the peripheral speed of the V-belt does not exceed the speed limit. Asynchronous control similar to that when the accelerator is ON may be performed. Furthermore, the larger gear ratio of the two controls may be set as the target value.
[0019]
FIG. 4 shows a shift pattern of the continuously variable transmission according to the present invention.
In the figure, R _HI is the minimum gear ratio (high), R _LO is the maximum gear ratio (low), Cv is the belt peripheral speed limit at load, Cv ′ is the belt peripheral speed limit at no load, and Ny is the engine limiter. The number of revolutions.
For example, when the vehicle is traveling at a point A, that is, in a clutch-synchronized state with the throttle opening being 2/4 and high, the target input rotational speed Nin is obtained from the accelerator opening and the vehicle speed, and this target input rotational speed Nin is determined as the target. Shift control is performed as a value. When the limit input rotational speed Ncv is obtained from the vehicle speed at the point A and the belt peripheral speed limit Cv, Nin <Ncv. Therefore, the V belt peripheral speed does not exceed the belt peripheral speed limit, and the speed change control is performed with Nin as a target value. There is no problem even if you do.
If the clutch 27 is disengaged for some reason while traveling at point A, the engine speed rapidly rises to near the limiter speed Ny, so that the point moves to point B. Point B also exceeds the belt peripheral speed limit Cv ′ when the belt peripheral speed is unloaded, and the durability reliability of the V-belt is lowered.
Therefore, in the present invention, when the clutch is in an asynchronous state and the accelerator is ON, the shift control is performed using the target speed ratio Ry obtained from the actual vehicle speed Vy and the actual input rotational speed Ny as a target value. That is, the shift control is performed with the point C as a target. Therefore, the belt peripheral speed can be kept lower than the belt peripheral speed limit Cv ′ when no load is applied, and the durability of the V belt can be prevented from being lowered.
In FIG. 4, the engine limiter rotational speed Ny is constant, but the limiter rotational speed Ny may be set lower when the clutch is asynchronous than when the clutch is synchronized. In that case, the belt peripheral speed can be further reduced.
[0020]
FIG. 5 shows a specific flow of the shift control according to the present invention.
When the control starts, it is first determined whether or not the clutch is in a synchronized state (step S1). This determination can be made by comparing the input rotational speed (driven shaft rotational speed) of the clutch 27 with the output rotational speed (output shaft rotational speed).
At the time of clutch synchronization, the target input speed Nin is obtained from the accelerator opening and the vehicle speed (step S2), and the target input speed Nin and the limit input speed Ncv obtained from the current vehicle speed and the belt peripheral speed limit Cv are obtained. Compare (step S3). If Nin ≦ Ncv, the belt peripheral speed limit is not exceeded, so the process proceeds to the next step. If Nin> Ncv, the belt peripheral speed limit is exceeded, so the target input speed Nin is limited to the limit input rotation. The number is limited by Ncv (step S4). Then, the shift control is performed with the target input rotational speed Nin as the target value (step S5).
On the other hand, when the clutch is asynchronous, it is determined whether or not the accelerator is ON (step S6). When the accelerator is ON, the target speed ratio Ry is subsequently calculated from the vehicle speed and the input rotational speed (step S7), and the speed change control is performed using the target speed ratio Ry as the target value (step S8).
When the clutch is asynchronous and the accelerator is OFF, the target input rotational speed Nin is obtained from the accelerator opening and the vehicle speed (step S9) as in step S2, and the shift control is performed using the target input rotational speed Nin as the target value (step S9). S10). In this case, since there is no possibility that the belt peripheral speed exceeds the limit value, it is not necessary to perform a comparison with the limit input rotation speed Ncv.
[0021]
The speed change control method according to the present invention is not limited to the above embodiment.
As control at the time of clutch synchronization, the upper limit of the target input rotational speed Nin is limited by the limit input rotational speed Ncv obtained from the current vehicle speed and the belt peripheral speed limit Cv, but when the predetermined vehicle speed is exceeded as in Patent Document 1. The shift control may be performed in accordance with a shift pattern in which the target input rotation speed is smaller than when the vehicle speed is equal to or lower than a predetermined vehicle speed. However, in this case, since a plurality of different shift patterns must be set, the setting becomes complicated and the target value becomes discontinuous, so that a sense of incongruity may occur during the shift. On the other hand, if the upper limit is limited by the limit input rotational speed Ncv obtained from the belt peripheral speed limit Cv as in the embodiment, it is not necessary to set a plurality of shift patterns, and the peripheral speed limit Cv is changed depending on the temperature or the like. Is easy, and since it is a continuous target value, discomfort can be eliminated. Furthermore, there is an advantage that it can be used up to the limit of the peripheral speed limit of the V-belt.
[0022]
【The invention's effect】
According to the first aspect of the present invention, when the clutch is in an asynchronous state and the accelerator pedal is depressed, the target speed ratio is obtained from the vehicle speed and the input rotational speed, and the speed is changed with the vicinity value of the target value as the target value. Since the control is executed, the peripheral speed of the V-belt does not increase rapidly, and it is possible to prevent the speed limit from being exceeded. Even when the clutch changes from an asynchronous state to a synchronous state, since the gear ratio is maintained in the vicinity of the gear ratio corresponding to the vehicle speed and the input rotation speed in advance, a sudden engine braking phenomenon occurs when the clutch is reengaged. And over-rotation of the engine can be avoided.
[Brief description of the drawings]
FIG. 1 is a skeleton diagram of an example of a continuously variable transmission according to the present invention.
FIG. 2 is a schematic view of a tension device used in the continuously variable transmission shown in FIG.
FIG. 3 is a diagram showing an outline of an input system and an output system of a control device.
FIG. 4 is a shift diagram showing shift control according to the present invention.
FIG. 5 is a flowchart showing an example of shift control according to the present invention.
FIG. 6 is a shift diagram showing conventional shift control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine output shaft 3 Input shaft 11 Drive side pulley 21 Driven side pulley 27 Starting clutch 32 Output shaft 40 Speed change motor 60 Control device 61 Clutch control actuator

Claims (1)

A belt-type transmission in which a drive pulley is connected to an engine, a driven pulley is connected to an output shaft, and a gear ratio can be changed steplessly; and a power interrupting clutch provided between the driven pulley and the output shaft; In the transmission control method for a continuously variable transmission comprising:
Detecting the vehicle speed from the rotational speed of the output shaft;
Detecting the input rotational speed of the transmission,
Detecting that the clutch is in an asynchronous state from the input rotation speed and the output rotation speed of the clutch;
Detecting the depression of the accelerator pedal;
A step of obtaining a target gear ratio from the detected vehicle speed and the input rotational speed when the vehicle is running and the clutch is in an asynchronous state and the accelerator pedal is depressed;
And a step of controlling the transmission of the transmission using a value close to the target gear ratio as a target value.

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