JP2929046B2 - Shift control device for continuously variable transmission - Google Patents

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, and more particularly to a pulley portion of a fixed pulley portion and a movable pulley portion which is detachably mounted on the fixed pulley portion. The present invention relates to a speed change control device for a continuously variable transmission that changes a speed ratio by decreasing or increasing a groove width between the pulleys and increasing or decreasing a rotation radius of a belt wound around both pulleys.

[0002]

2. Description of the Related Art In a vehicle, a transmission is interposed between an internal combustion engine and driving wheels. This transmission changes the driving force of the drive wheels and the traveling speed in accordance with the traveling conditions of the vehicle that vary over a wide range, thereby sufficiently exhibiting the performance of the internal combustion engine. The transmission is formed between both pulley parts of a pulley having a fixed pulley part fixed to the rotating shaft and a movable pulley part attached to the rotating shaft so as to be able to approach and separate from the fixed pulley part. 2. Description of the Related Art There is a continuously variable transmission that changes the radius of rotation of a belt wound around a pulley by increasing or decreasing the width of a groove to transmit power and change a gear ratio (belt ratio).

[0003] Further, as disclosed in Japanese Patent Application Laid-Open No. 2-150555, for example, a belt ratio control device of a continuously variable transmission is set by a throttle opening when starting on a road surface having a low road surface friction coefficient. In some cases, control means for controlling the belt ratio so as to obtain the target belt ratio value is provided.

[0004]

A shift control device for a conventional continuously variable transmission includes a snow mode SNOW.
There are some which have MODE, and this snow mode SNO
W MODE controls the speed ratio RATC to an intermediate ratio in the normal start mode NST, and easily starts on a snowy road, a frozen road surface, or a muddy road.

[0005] In addition, the shift control device of another continuously variable transmission includes a gear ratio RATC other than the snow mode SNOW MODE, that is, even in the normal normal start mode NST.
In some cases, the starting feeling is improved by controlling the intermediate ratio.

The above-mentioned snow mode SNOW MODE
As shown in FIG. 9, the transmission control device for a continuously variable transmission provided with a transmission ratio target value map for obtaining a transmission ratio target value RATSP using the throttle opening degree THR of the engine as a variable. Is controlled so as to coincide with the target gear ratio value RATSP obtained from the target gear ratio map. However, the target gear ratio map shown in FIG. 9 is set such that the target gear ratio RATSP decreases as the throttle opening THR increases.

For this reason, not only is it impossible to obtain a sufficient driving force, but also the temperature of the clutch, for example, the hydraulic starting clutch rises sharply, that is, the heat generation becomes large, and the durability of the hydraulic starting clutch deteriorates. At the same time, the transmission oil ATF is deteriorated, which is disadvantageous in practical use.

In addition, the rise in the temperature of the hydraulic start clutch lowers the friction coefficient of the hydraulic start clutch, thereby deteriorating the control of the hydraulic start clutch and causing inconveniences such as a rapid increase in engine speed and a long start time. I was invited.

[0009]

SUMMARY OF THE INVENTION Accordingly, in order to eliminate the above-mentioned disadvantages, the present invention is directed to a pulley portion comprising a fixed pulley portion and a movable pulley portion which is detachably attached to the fixed pulley portion. A continuously variable transmission that changes the gear ratio by increasing or decreasing the groove width between the two pulleys to increase or decrease the radius of rotation of the belt wound around the two pulleys is provided. A speed ratio target value map for determining the vehicle speed, and controlling the speed ratio of the continuously variable transmission to match the speed ratio target value obtained from the speed ratio target value map. As the speed ratio target value map at the time of starting, at least a normal start mode speed ratio target value map for a normal road surface and a snow mode speed change for a slippery road surface. A target value map, wherein the snow mode speed ratio target value map is set such that the speed ratio target value decreases as the throttle opening increases when the throttle opening is less than the set value, and the throttle opening Is larger than the set value, the gear ratio target value is set to increase as the throttle opening increases, and when the snow mode is selected when the vehicle starts, the gear ratio of the continuously variable transmission is changed to the snow mode. And a control unit for performing a speed change control so as to match the speed ratio target value obtained from the speed ratio target value map for use.

[0010]

The shift control device for a continuously variable transmission according to the present invention comprises:
As a speed ratio target value map at the time of starting of the vehicle, when the throttle opening is smaller than the set value, the speed ratio target value is set to decrease as the throttle opening increases, and when the throttle opening is equal to or more than the set value. A gear ratio target value map for snow mode is provided for slippery roads, which is set so that the gear ratio target value increases as the throttle opening increases.If the snow mode is selected when the vehicle starts, continuous variable speed By providing a control unit that controls the speed change so that the speed ratio of the engine matches the speed ratio target value obtained from the snow mode speed ratio target value map, the snow mode is selected when the vehicle starts and the engine torque increases. If the throttle opening is larger than the set value, the throttle opening becomes larger from the snow mode gear ratio target value map. The larger gear ratio target value As the determined by the shift control so as to match the gear ratio of the continuously variable transmission to the large speed ratio target value, it is possible to suppress the heat generation of the clutch.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

1 to 6 show an embodiment of the present invention. In FIG. 2, 2 is a belt-driven continuously variable transmission, 2A is a belt, 4 is a driving pulley, 6 is a driving fixed pulley piece, 8 is a driving movable pulley piece, 10 is a driven pulley, and 12 Is a driven-side fixed pulley part, and 14 is a driven-side movable pulley part. As shown in FIG. 2, the drive side pulley 4 is fixed to the rotation shaft 16, and the drive side pulley piece 6 is attached to the rotation shaft 16 so as to be movable in the axial direction of the rotation shaft 16 and cannot rotate. And a driving-side movable pulley portion piece 8. In addition, the driven pulley 10 also
Like the drive pulley 4, it has a driven fixed pulley piece 12 and a driven movable pulley piece 14.

A first housing 18 and a second housing 18 are attached to the driving-side movable pulley portion 8 and the driven-side movable pulley portion 14.
20 are respectively mounted, and first and second hydraulic chambers 22, 24 are respectively formed. At this time, in the second hydraulic chamber 24 on the driven side, an urging means 26 made of a spring or the like for urging the second housing 20 in the expanding direction of the second hydraulic chamber 24 is provided.

An oil pump 28 is provided on the rotary shaft 16 and is connected to the first and second hydraulic chambers 2.
The first and second oil passages 30 and 32 communicate with the first and second oil passages 30, respectively, and a primary pressure control valve 34 as a transmission control valve for controlling a primary pressure as an input shaft sheave pressure is provided in the first oil passage 30. I do. Further, a line pressure (generally 5 to 25 kg / cm ² ) is applied to the first oil passage 30 on the oil pump 28 side of the primary pressure control valve 34 by a third oil passage 36 to a constant pressure (3 to 4 kg / c).
m ² ), a primary pressure control first three-way solenoid valve 42 is connected to the primary pressure control valve 34 via a fourth oil passage 40.

In the middle of the second oil passage 32, a line pressure control valve 44 having a relief valve function for controlling a line pressure serving as a pump pressure is connected through a fifth oil passage 46 to the line pressure control valve 44. A second three-way solenoid valve 50 for line pressure control communicates with the six oil passages 48.

Further, a clutch pressure control valve 52 for controlling a clutch pressure is provided in the second oil passage 32 on a side closer to the second hydraulic chamber 24 than a portion where the line pressure control valve 44 communicates.
The clutch pressure control valve 5 communicates with the oil passage 54.
A third three-way solenoid valve 58 for clutch pressure control communicates with the second through an eighth oil passage 56.

The primary pressure control valve 34, the first three-way solenoid valve 42 for primary pressure control, the constant pressure control valve 3
The eighth, sixth, oil passages 48, the second three-way solenoid valve for line pressure control 50, and the clutch pressure control valve 52 are communicated by a ninth oil passage 60, respectively.

The clutch pressure control valve 52 has a tenth oil passage 64 connected to a clutch, for example, a hydraulic starting clutch 62.
And the tenth oil passage 64
A pressure sensor 68 is communicated on the way through an eleventh oil passage 66. The pressure sensor 68 can directly detect the hydraulic pressure when controlling the clutch pressure in the hold and start modes and the like, and contributes when instructing the detected hydraulic pressure to be the target clutch pressure. In the drive mode, the clutch pressure becomes equal to the line pressure, which also contributes to line pressure control.

An input shaft rotation detecting gear 70 is provided outside the first housing 18, and a first rotation detector 72 on the input shaft side is provided near an outer peripheral portion of the input shaft rotation detecting gear 70.
Further, an output shaft rotation detection gear 74 is provided outside the second housing 20, and a second rotation detector 76 on the output shaft side is provided near an outer peripheral portion of the output shaft rotation detection gear 74. Then, detection signals from the first rotation detector 72 and the second rotation detector 76 are output to a control unit 82, which will be described later, to grasp the engine speed and the belt ratio.

The hydraulic start clutch 62 is provided with an output transmission gear 78, and a third rotation detector 80 for detecting the rotation of the final output shaft is provided near the outer periphery of the gear 78. That is, the third rotation detector 80 includes a reduction gear and a differential gear,
It detects the rotation of the drive shaft and the final output shaft directly connected to the tire, and can detect the vehicle speed. In addition, the second
The rotation detector 76 and the third rotation detector 80 can also detect the rotation before and after the hydraulic start clutch 62, which contributes to the detection of the clutch slip amount.

Furthermore, various conditions such as the throttle opening of a carburetor (not shown) of the vehicle and the engine rotation and the vehicle speed from the first to third rotation detectors 72, 76, 80 are input and the duty ratio is changed to control the shift. The control unit 82 performs the primary three-way solenoid valve 42 and the constant pressure control valve 38 for primary pressure control, the second three-way solenoid valve 50 for line pressure control, and the third three-way solenoid valve for clutch pressure control. The opening and closing operation of the valve 58 is controlled, and the pressure sensor 68 is also controlled.

The functions of various signals input to the control unit 82 and the functions of the input signals will be described in detail below. The detection signals of the shift lever position... P, R, N, D,
Line pressure and ratio required for each range by each range signal such as L, control of clutch, detection signal of throttle opening degree ... Detection of engine torque from memory previously input into the program, target ratio or target engine speed , A driver demand switch (DDTSW) signal... Detects the driver's will by the depression state of the accelerator pedal, and determines the control method at the time of running or starting. The accelerator pedal signal... According to the depression state of the accelerator pedal Detects the driver's will, determines the control direction when driving or starting, brake signal ... Detects whether or not the brake pedal is depressed, determines the control direction such as disengaging the clutch, and power mode option signal ... vehicle Options to make sports performance (or economy) There is a use such as emissions.

The control unit 82 controls the gear ratio target value RATSP by using at least the throttle opening degree THR of the engine as a variable.
Of the continuously variable transmission 2 in accordance with these various input signals.
The gear shift control is performed so that the ATC matches the gear ratio target value RATSP obtained from the gear ratio target value map.

Here, the continuously variable transmission 2 will be described with reference to FIG.
A description will be given along the torsional vibration system model. From FIG. 3, IE · dθe / dt = T_E-T_C/ I_B  ∴T_c= I_B(T_E-I_E・ Dθe / dt) I_E : Engine inertia θe: Engine speed NE T_E : Engine torque θs: Clutch input rotation speed (NC2) T_c : Clutch capacity θc: clutch output speed (NCO) i_B : Gear ratio RATC I_R: Load inertia and gear ratio RATCi_BThe larger the
H capacity T_cAnd a large driving force can be obtained.

When the starting control is started at t = 0 sec and ended at t = tc, the calorific value Q of the hydraulic starting clutch at the start is calculated by the following equation.

(Equation 1) Next, this _{T C = i B (T E} -I E · dθe / d
t) and θs = (1 / i _B ) · θe, the calorific value Q of the hydraulic starting clutch is

(Equation 2) Becomes

Therefore, the clutch input rotation speed (NC2) θ
s> At the clutch output rotational speed (NCO) θc, the heat generation amount Q decreases as the speed ratio RATCi _B increases,
The longer the start control time or the engine torque _TE
Is larger, the calorific value Q is larger.

Further, in the driving side of the hydraulic start _{clutch, i B · I E · dθs} / dt = i B · T E -T C ∴dθs / dt = (1 / i B «· I E) · (i B · T _E -T _C ), and on the driven side of the hydraulic start clutch, I _R · d θc / dt = T _C -T _R d d c / dt = (1 / I _R ) · (T _C -T _R ) T _R : Load The clutch input speed (NC2) θs and the clutch output speed (NCO) θc when the initial values are θsο and θco.
Is, θs = θsο + (1 / i B «· I E) · (i B · T E -T C) θc = θcο + (1 / I R) · (T C -T R) becomes, where, t = If a [theta] s = .theta.c at tc, θsο + (1 / i B «· I E) · (i B · T E -T C) tc = θcο + (1 / I R) · (T C -T R) tc, whereby the time tc becomes

(Equation 3) Becomes

Furthermore, upon starting control, since the _{T C = i B (T E} -I E · dθe / dt) is satisfied, the time tc,

(Equation 4) Becomes

[0029] Furthermore, the start control at the time, since the fluctuation of the clutch output rotational speed (NCO) .theta.c is small, when dθe / dt = 0, the time _{tc, ∴tc = (I R /} i B · T E - T _R) · (θsο-θc
ο) Thus, as the gear ratio RATCi _B is large time tc is shorter.

As a result, the following conclusion is obtained. The smaller the gear ratio RATC, the greater the amount of heat generated by the hydraulic start clutch. The smaller the speed ratio RATC, the longer the start control. The longer the start control, the greater the amount of heat generated by the hydraulic start clutch. The greater the engine torque, the greater the amount of heat generated by the hydraulic start clutch.

From this conclusion, the heat value Q of the hydraulic start clutch rapidly increases when the engine torque is large and the gear ratio RATC is low.

Therefore, according to the present invention, at least the normal start mode speed ratio target value map for normal road surface shown in FIG. 6 and the throttle opening THR shown in FIG. When the throttle opening THR is smaller than the set value S, the target gear ratio RATSP is set to be smaller as the throttle opening THR is larger. When the throttle opening THR is larger than the set value S, the target gear ratio is set as the throttle opening THR becomes larger. Value R
A snow mode speed ratio target value map for a slippery road surface set to increase ATSP is provided, and the throttle opening THR at which the snow mode SNOW MODE is selected when the vehicle starts to increase the engine torque is set to the set value S.
In the above case, a gear ratio target value RATSP that increases as the throttle opening THR increases from the snow mode gear ratio target value map is determined, and the gear ratio RATC of the continuously variable transmission 2 is set to this large gear ratio target value RATSP. By controlling the shift so that they coincide with each other, the heat generation amount Q of the hydraulic start clutch 62 is prevented from abnormally increasing.

The control unit 82 has a structure in which a target gear ratio value is set so as to increase the gear ratio when the control mode in which the engine torque is increased is set, and the amount of heat generated by the hydraulic start clutch is suppressed. ing.

More specifically, as shown in FIG. 4, the control unit 82 controls the normal start mode gear ratio target value map (106) shown in FIG. 6 and the slippery road surface map shown in FIG. Gear ratio target value map for snow mode (1
00) and the throttle opening THR when the vehicle starts moving
F (TH) of the gear ratio target value RATSP by the detection signal of
R) From the gear ratio target value map (100) for the normal start mode consisting of the curve RATCV2, the gear ratio target value R
The ATSP is determined, and the target gear ratio RATSPH in the hold mode HLD is set as the target gear ratio RATSP (102).

As the gear ratio target value RATSP, one of the above-mentioned ones is used by the operation of a control mode switch SW (104) described later.

The control mode switch SW (1
04) connects to the normal start mode speed ratio target value map (100) side in the normal start mode NST and connects to the processing (102) side in the hold mode HLD according to the selected control mode.

The speed ratio target value RATSP is obtained from a snow mode speed ratio target value map (106) comprising an f (THR) curve RATCV1 of the speed ratio target value RATSP based on the detection signal of the throttle opening degree THR.

Thereafter, the gear ratio target value RATSP is determined by the operation of the snow mode switch NOW MODESW (108).

The snow mode switch SNOW MO
The DE SW (108) is connected to the control mode switch (104) besides the snow mode,
In the snow mode, it is connected to the snow mode speed ratio target value map (106) comprising the f (THR) curve RATCV1.

Further, a snow mode switch SNOW
Filter processing is performed on the gear ratio target value RATSP determined by the MODE SW (108) (110), then an error from the gear ratio RATC is obtained (112), and the ratio solenoid duty OPW is obtained by PI control (114).
RAT is calculated and the ratio solenoid duty OP
Each solenoid valve is excited by WRAT.

Reference numeral 84 denotes the hydraulic start clutch 6
2 is a piston, 86 is an annular spring, 88 is a first pressure plate, 90 is a friction plate, and 92 is a second plate.
A pressure plate, 94 is an oil pan, and 96 is an oil filter.

Next, the operation will be described.

As shown in FIG. 2, the belt-driven continuously variable transmission 2 includes an oil pump 2 located on a rotating shaft 16.
8 operates according to the drive of the rotating shaft 16, and the oil is absorbed from an oil pan 94 at the bottom of the transmission via an oil filter 96. The line pressure, which is the pump pressure, is controlled by the line pressure control valve 44. If the amount of leakage from the line pressure control valve 44, that is, the escape amount of the line pressure control valve 44, is large, the line pressure decreases. If it is less, the line pressure will be higher.

The line pressure control valve 44 has a shift control characteristic of changing the line pressure in each of a full low state, a full overtop state, and a fixed ratio state to perform three-stage control.

The operation of the line pressure control valve 44 is controlled by a dedicated second three-way solenoid valve 50, and the line pressure control valve 44 operates following the operation of the second three-way solenoid valve 50. The second three-way solenoid valve 50 is controlled at a constant frequency duty ratio. That is, when the duty ratio is 0%, the second three-way solenoid valve 50 does not operate at all, the output side is connected to the atmosphere side, and the output oil pressure becomes zero.
When the duty ratio is 100%, the second three-way solenoid valve 50 operates, the output side is connected to the output side, the maximum output oil pressure is the same as the control pressure, and the output oil pressure is varied according to the duty ratio. Therefore, the characteristics of the second three-way solenoid valve 50 are substantially linear, and the line pressure control valve 44 can be operated in an analog manner.
The line pressure can be controlled by arbitrarily changing the duty ratio. The operation of the second three-way solenoid valve 50 is controlled by the control unit 82.

The primary pressure for shifting control is controlled by the primary pressure control valve 34, and the operation of the primary pressure control valve 34 is also controlled by a dedicated first three-way solenoid valve 42, similarly to the line pressure control valve 44. ing. The first three-way solenoid valve 42 is used to conduct the primary pressure to the line pressure or conduct the primary pressure to the atmosphere side. The first three-way solenoid valve 42 conducts the line pressure to shift the belt ratio to the full overdrive side, or Side to make a full-low side.

Clutch pressure control valve 5 for controlling clutch pressure
Reference numeral 2 denotes a connection to the line pressure side when the maximum clutch pressure is required, and a connection to the atmosphere side when the minimum clutch pressure is required. This clutch pressure control valve 52 is also similar to the line pressure control valve 44 and the primary pressure control valve 34,
The operation is controlled by the dedicated third three-way solenoid valve 58, and the description is omitted. The clutch pressure varies within a range from a minimum atmospheric pressure (zero) to a maximum line pressure.

There are four basic patterns for controlling the clutch pressure, which will be described later. These basic patterns are as follows: (1) Neutral mode: When the shift position is N or P and the clutch is completely disengaged, the clutch pressure becomes the minimum pressure. (Zero) (2) Hold mode: If the shift position is D or R and the throttle is released and there is no driving intention, or if it is desired to decelerate during running and cut off the engine torque, the clutch pressure should be such that the clutch contacts. Low level (3), start mode: When attempting to re-engage the clutch at the time of starting or after the clutch is disengaged, the clutch pressure prevents the engine from rising and the engine-generated torque (clutch input torque) that allows the vehicle to operate smoothly. (4) Drive mode: transition from complete driving state When the clutch is fully engaged, there are four high levels of clutch pressure that can afford enough to withstand engine torque. The basic pattern (1) is performed by a dedicated switching valve (not shown) that is interlocked with the shift operation, and the other (2), (3), and (4) are the first to third control units by the control unit 82.
This is performed by controlling the duty ratio of the third three-way solenoid valves 42, 50, 58. Particularly in the state of (4), the seventh oil passage 54 and the tenth oil passage 54 are controlled by the clutch pressure control valve 52.
The oil pressure is communicated with the oil passage 64 so that a maximum pressure is generated, and the clutch pressure becomes equal to the line pressure.

The primary pressure control valve 34, the line pressure control valve 44, and the clutch pressure control valve 52
The control hydraulic pressure for controlling the first to third three-way solenoid valves 42, 50 and 58 is generated by the constant pressure control valve 38. Constant hydraulic pressure. This control oil pressure is always higher than the line pressure, but is a stable and constant pressure. The control hydraulic pressure is also introduced into each of the control valves 34, 44, 52, and these control valves 34, 44,
4, 52 are stabilized.

Next, the electronic control of the belt-driven continuously variable transmission 2 will be described.

The continuously variable transmission 2 is hydraulically controlled, and receives an appropriate line pressure for holding the belt and transmitting torque, a primary pressure for changing the gear ratio, and a clutch in response to a command from the control unit 82. Clutch pressures for secure connection are ensured respectively.

A shift control flowchart of the belt-driven continuously variable transmission 2 will be described with reference to FIG.

First, the belt-driven continuously variable transmission 2
To start the control program (200).

Next, a snow mode switch SNOW M
Determination of ON / OFF state of ODE SW (108) (20
2) is performed, and if it is off, it is determined (204) whether or not the driving state of the vehicle is the normal start mode NST.

If the determination (204) is YES, the normal start mode speed ratio target value map (100) consisting of the f (THR) curve RATCV2 in FIG. 6 is used to determine the speed ratio target value RATSP according to RATSP = RATCV2 (THR). (206), and the judgment (204)
Is NO, it is determined whether or not the mode is the hold mode HLD (208).

If the judgment (208) is NO, the process shifts to another shift control (210) and returns (21).
Proceeding to 8), if the determination (208) is YES, the gear ratio target value RATSPH in the hold mode HLD is set as the gear ratio target value RATSP (212).

The control mode R is determined by the gear ratio target value RATSP from steps (212) and (206).
The ATMOD is set (214), the ratio solenoid duty OPWRAT is calculated (216), and the process proceeds to the return (218).

In the above judgment (202), the snow mode switch SNOW MODE SW (108)
Is ON, it is determined whether the driving state of the vehicle is in the normal start mode NST (220). If YES, the snow mode speed ratio target value consisting of the f (THR) curve RATCV1 in FIG. 5 is determined. From the map (106), a gear ratio target value RATSP is obtained from RATSP = RATCV1 (THR) (222), and if NO, it is determined whether or not the hold mode is HLD (224).

If the judgment (224) is NO, the process shifts to another shift control (210) and returns (21).
8), and if the judgment (224) is YES, FIG.
RATSP by the snow mode speed ratio target value map (106) composed of the f (THR) curve RATCV1 of FIG.
= RATCV1 (THR) to obtain the gear ratio target value RATS
P is determined (222), and the control mode RATEMOD is determined by the gear ratio target value RATSP from the process (222).
Is set (214), and after the ratio solenoid duty OPWRAT is calculated (216), the return (2)
Proceed to 18).

As described above, the speed ratio target value map for the normal start mode shown in FIG. 6 and the speed ratio target value map for the normal start mode shown in FIG.
When the throttle opening THR is smaller than the set value S, the target gear ratio value RATSP is set to decrease as the throttle opening THR increases, and when the throttle opening THR is equal to or more than the set value S, the throttle opening T is set.
A snow mode speed ratio target value map for a slippery road surface is provided which is set so that the speed ratio target value RATSP increases as the HR increases. When the vehicle starts, the snow mode SNOWMODE is selected and the engine torque increases. When the throttle opening THR is equal to or greater than the set value S,
From the gear ratio target value map for the snow mode, the gear ratio target value R that increases as the throttle opening THR increases.
The ATSP is obtained, and the gear ratio is controlled so that the gear ratio RATC of the continuously variable transmission 2 matches the large gear ratio target value RATSP. The heat generation amount Q of the hydraulic start clutch 62 increases when the engine torque is large and the speed ratio RATC is small, which is derived from the conclusion based on the torsional vibration system model shown in FIG. When the snow mode SNOW MODE is selected and the engine torque is increased, the throttle opening THR is set to the set value S.
In the above case, the heat generation amount Q of the hydraulic start clutch 62 is abnormally increased by performing the speed change control so that the speed ratio RATC of the continuously variable transmission 2 matches the large speed ratio target value RATSP as shown in FIG. This can prevent the temperature of the hydraulic start clutch 62 from rising, shorten the start control time, secure the durability of the hydraulic start clutch 62 and extend the service life. In addition, the maintenance cost can be reduced, which is economically advantageous, the friction coefficient of the hydraulic start clutch 62 can be maintained, and the controllability of the hydraulic start clutch 62 can be ensured, which is practically advantageous.

Further, since it is possible to cope with only a part of the program in the control unit, the configuration is not complicated, the size is not increased, the manufacturing is easy, the cost can be maintained at a low cost, and the cost can be reduced. Is advantageous.

Further, when starting at a high throttle opening, a sufficient driving force can be obtained quickly and surely, so that the starting performance can be improved, which is practically advantageous.

Further, by preventing the temperature of the hydraulic starting clutch from rising, deterioration of the transmission oil ATF can be prevented.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made.

For example, in the above embodiment, the gear ratio target value RATSP is determined using the throttle opening THR as a variable, but the gear ratio target value RATSP may be determined using the engine generated torque as a variable.

[0066]

As described above in detail, according to the present invention, the target value of the gear ratio when the vehicle starts moving is:
When the throttle opening is less than the set value, the gear ratio target value is set to decrease as the throttle opening increases, and when the throttle opening is equal to or greater than the set value, the gear ratio target value increases as the throttle opening increases. A snow mode speed ratio target value map for a slippery road surface set to be large is provided, and when the snow mode is selected when the vehicle starts, the speed ratio of the continuously variable transmission is set to the snow mode speed ratio target value. By providing a control unit that controls the gearshift to match the gear ratio target value obtained from the map, when the snow mode is selected when the vehicle starts and the throttle opening at which engine torque becomes large is equal to or greater than the set value, From the snow mode gear ratio target value map, a gear ratio target value that increases with an increase in the throttle opening is obtained. By controlling the transmission so that the transmission gear ratio matches the large gear ratio target value, the amount of heat generated by the clutch can be suppressed, the temperature of the clutch can be prevented from rising, and the time for starting control can be shortened. Can secure the durability of the clutch and extend the service life,
It is practically advantageous. In addition, by being able to cope with only a part of the program in the control unit, the configuration is not complicated, the size is not increased, and the production is easy.
The cost can be kept low, which is economically advantageous. Further, even when starting at a high throttle opening, a sufficient driving force can be obtained quickly and reliably, so that the starting performance can be improved, which is practically advantageous.

[Brief description of the drawings]

FIG. 1 is a shift control flowchart of a continuously variable transmission according to an embodiment of the present invention.

FIG. 2 is a schematic view of a continuously variable transmission.

FIG. 3 is a diagram showing a torsional vibration system model of the continuously variable transmission.

FIG. 4 is a block diagram of shift control of a control unit of the continuously variable transmission.

FIG. 5 is a diagram showing a relationship between a throttle opening degree THR and a gear ratio target value RATSP according to a snow mode gear ratio target value map.

FIG. 6 shows a throttle opening THR and a gear ratio target value RATSP based on a gear ratio target value map for a normal start mode.
FIG.

FIG. 7 is a diagram showing an engine torque curve.

FIG. 8 is a time chart for gear shift control of the continuously variable transmission.

FIG. 9 shows a throttle opening degree THR and a gear ratio target value RATS according to a gear ratio target value map showing the prior art of the present invention.
It is a figure showing the relation with P.

FIG. 10 is a time chart for gear shift control of a continuously variable transmission showing the conventional technique of the present invention.

[Explanation of symbols]

 2 Belt Drive Continuous Variable Transmission 2A Belt 4 Drive Pulley 10 Driven Pulley 28 Oil Pump 34 Primary Pressure Control Valve 38 Constant Pressure Control Valve 44 Line Pressure Control Valve 52 Clutch Pressure Control Valve 62 Hydraulic Start Clutch 68 Pressure Sensor 82 Control Department

Continued on the front page (56) References JP-A-1-283470 (JP, A) JP-A-2-150555 (JP, A) JP-A-2-124357 (JP, U) (58) Fields investigated (Int) .Cl. ⁶ , DB name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48 B60K 41/00-41/28

Claims (1)

(57) [Claims] 1. A belt which is wound around both pulleys by increasing or decreasing a groove width between a fixed pulley portion and a movable pulley portion attached to and detachable from the fixed pulley portion. A continuously variable transmission that changes a gear ratio by increasing or decreasing a radius of rotation; a gear ratio target value map for obtaining a gear ratio target value using at least a throttle opening of the engine as a variable; In the continuously variable transmission that controls the speed change so as to match the speed ratio target value obtained from the speed ratio target value map, the speed control device includes at least a normal start for a normal road surface as the speed ratio target value map when the vehicle starts. A speed ratio target value map for a mode and a snow mode speed ratio target value map for a slippery road surface are provided. When the throttle opening is smaller than the set value, the gear ratio target value is set to decrease as the throttle opening increases, and when the throttle opening is equal to or larger than the set value, the gear ratio target value increases as the throttle opening increases. When the snow mode is selected when the vehicle starts, the gear ratio of the continuously variable transmission is made to match the gear ratio target value obtained from the snow mode gear ratio target value map. A shift control device for a continuously variable transmission, comprising a control unit for performing shift control.