JPS6256659A - Control method for continuously variable transmission for vehicle - Google Patents

Abstract

PURPOSE:To reduce speed change shock by changing the revolution number of an objective engine over into the value in a condition where a gear step of an auxiliary speed change gear is in a high gear step prior to the changeover of a gear step of the auxiliary speed change gear when the auxiliary speed change gear is changed over from low speed step to high speed step. CONSTITUTION:An objective input shaft rotating speed for the control of a speed change ratio is changed over, prior to the changeover of an actual gear step, from an objective input shaft rotating speed for low speed into an objective input shaft rotating speed for high speed when a shift-up control, that changeovers an auxiliary speed change gear from low speed gear step into high speed gear step, is executed. Hereby a torque and its preceding inertial torque which are input into the auxiliary speed change gear is reduced by the changeover of a gear train to reduce a speed change shock.

Description

Detailed Description of the Invention Technical Field The present invention relates to a method for controlling a continuously variable transmission for a vehicle having an auxiliary transmission that can be switched to at least two forward gears.
Especially the gear shift of the sub-transmission.

This paper relates to technology that reduces the effects of

BACKGROUND OF THE INVENTION Vehicles are known that are equipped with an auxiliary transmission that is automatically switched to one of at least two forward gears according to the driving state of the vehicle. For example, JP-A-60-3745
The one described in Publication No. 5 is one such example. In such vehicles, during gear change operations such as upshifting while the vehicle is accelerating, a sudden acceleration shock that follows a temporary deceleration is likely to occur as the gear train that makes up the gear changes, which impairs drivability. There were cases where

In particular, in continuously variable transmissions in which an auxiliary transmission is connected to the rear stage, the gear ratio of the continuously variable transmission body (input shaft rotational speed /
As the output shaft rotational speed increases, the torque input to the auxiliary transmission and the inertia torque of the preceding stage increase, so the shift shock associated with shifting the auxiliary transmission tends to increase. In some cases, the load applied to the frictional engagement device during shifting of the transmission becomes large, making it impossible to obtain durability.

Means for Solving the Problem The present invention has been made against the background of the above circumstances.
The gist of this is that in a continuously variable transmission for a vehicle that has an auxiliary transmission that can be switched to at least two forward gears, the gears of the continuously variable transmission are changed so that the rotational speed of the engine matches the target rotational speed. 2. A control method of the type in which the target rotational speed of the engine is determined to be higher when the auxiliary transmission is in a low gear than when the auxiliary transmission is in a high gear, while adjusting the gear ratio of the auxiliary transmission. When changing gears from a low gear to a high gear, the target rotational speed is switched to a value at which the gear of the auxiliary transmission is in a high gear, prior to changing the gear of the auxiliary transmission. be.

Operation and Effects of the Invention With this arrangement, when a gear change operation of the sub-transmission such as an upshift is performed while the vehicle is accelerating, the target rotational speed of the sub-transmission is set prior to changing the gear of the sub-transmission. Since the gear is switched to the value of the high gear,
When the gear train is switched, the torque input to the auxiliary transmission and the inertia torque of the preceding stage are reduced, thereby alleviating the shift shock. In particular, in the past, as the gear ratio (input shaft rotational speed/output shaft rotational speed) of the continuously variable transmission body increases, the torque input to the auxiliary transmission and the inertia torque of the previous stage thereof increase. However, according to the present invention, this problem can be effectively eliminated and drivability can be improved. Furthermore, the load applied to the shift special friction engagement device of the auxiliary transmission is reduced, and its durability is increased.

EXAMPLE Hereinafter, an application example of the present invention will be explained in detail based on the drawings.

In FIG. 2, the power of the engine 8 is transmitted through a fluid coupling 10, a belt type continuously variable transmission (hereinafter referred to as CVT) 12. Sub-transmission 14. Intermediate gear device 16. The signal is transmitted via the differential device 18 to a drive shaft (not shown) connected to the drive shaft 20.

In this embodiment, the continuously variable transmission is a CVT corresponding to its main body.
12 and an auxiliary transmission 14.

The fluid coupling 10 connects a pump 24 connected to a crankshaft 22 of an engine 8, a turbine 28 fixed to an input shaft 26 of a CVT 12 and rotated by oil from the pump 24, and a damper 30 connected to the input shaft 26. The lock-up clutch 32 is fixed to the lock-up clutch 32. The lock-up clutch 32 is activated when, for example, the vehicle speed, the engine rotational speed, or the rotational speed of the turbine 28 exceeds a predetermined value, and connects the crankshaft 22 and the input shaft 26 directly.

The CVT 12 includes variable pulleys 36 and 38 provided on the input shaft 26 and output shaft 34, respectively, and a transmission belt 40 wound around the variable pulleys 36 and 38. The variable boos IJ 36 and 38 have fixed rotating bodies 42 and 44 fixed to the input shaft 26 and the output shaft 34, respectively, and a human power shaft 26 and the output shaft 34.
The movable rotating bodies 46 and 48 are respectively provided to be movable in the axial direction and non-rotatable about the axis, and the movable rotating bodies 46 and 48 are connected to hydraulic cylinders 50 and 52.
By being moved by ■, the groove width, that is, the hanging diameter (effective diameter) of the transmission belt 40 is changed,
2 (=rotational speed N i of the human power shaft 26 /rotational speed N.ut of the output shaft 34 ) is changed. The hydraulic cylinder 50 is operated exclusively to change the gear ratio T, and the hydraulic cylinder 52 is operated exclusively to obtain the minimum clamping force within a range where the transmission belt 40 does not slip. The oil pump 54 constitutes a hydraulic pressure source of a hydraulic control device, which will be described later, and is connected to the crankshaft 22 via a not-illustrated connecting shaft passing vertically through the input shaft 26, and is constantly rotationally driven by the engine 8.

The auxiliary transmission 14 is a stepped automatic transmission that is connected in series with the CVT 12 at a later stage and is automatically switched between a forward high gear and a low forward gear according to the driving conditions of the vehicle. It is provided coaxially with the protrusion shaft 34 and includes a Ravigneau type compound planetary gear device.

This planetary gear device includes a pair of first sun gear 56 and second sun gear 58, a first planet gear 60 that meshes with the first sun gear 56, and a second planet gear 62 that meshes with the first planet gear 60 and second sun gear 58. and the first planetary gear 6
a carrier 66 that rotatably supports the ring gear 64 that meshes with the first planetary gear 60 and the second planetary gear 62;
It is equipped with The second sun gear 58 is fixed to a shaft 68 that is integrally connected to the output shaft 34, and the carrier 66 is fixed to an output gear 70. High speed clutch 72
controls the engagement between the shaft 68 and the first sun gear 56, the low speed brake 74 controls the engagement of the first sun gear 56 with the housing, and the reverse brake 76 controls the engagement of the ring gear 64 with the housing. control. FIG. 3 shows the operating state of each friction engagement element of the sub-transmission 14 and the reduction ratio in each range. In the figure, ◯ indicates an engaged state, x indicates a released state, and ρ1 and ρ2 are gear ratios defined from the following equation.

ρ1=Z□/Z.

ρ2=2.2/Z.

However, Zg+ is the number of teeth of the first sun gear 56, Z, , □ is the number of teeth of the second sun gear 58, and Zr is the number of teeth of the ring gear 64.

Therefore, in the low gear stages in the L and D ranges, the first frictional engagement device and the low gear brake 74 in L2 are operated and the first Zang gear 56 is fixed, so the reduction ratio (1(-ρ1/ Power is transmitted at ρ2), but L
In the high gear stage of the D range, the entire planetary gear system rotates as a unit by the operation of the high speed clutch 72 as the second frictional engagement device, thereby causing the reduction ratio to be 1.
Power is transmitted at. Furthermore, in the R range, the ring gear 64 is fixed to the housing by the operation of the reverse brake 76, so the gear ratio is (1-1/ρ2).

Power is transmitted by the reverse rotation of .

The output gear 70 of the sub-transmission 14 is connected to the differential device 18 via the intermediate gear device 16, and the power of the engine 8 is distributed to the left and right drive shafts 20 in the differential device 18, and then transferred to the left and right drive shafts 20. transmitted to the drive shaft.

FIG. 4 shows a hydraulic control circuit for controlling the vehicle power transmission device shown in FIG. The oil pump 54 pumps hydraulic oil and the like returned into an oil tank (not shown) through a strainer 80 to a suction line pressure oil passage 82 .

The throttle valve 84 generates a throttle pressure P corresponding to the throttle valve opening θ at its output port 86. The spool 88 of the throttle valve 84 receives in opposite directions an acting force that increases as the throttle valve opening θ increases from a throttle cam 90 that rotates together with the throttle valve, and a throttle pressure P as a feedback pressure from a control boat 92. , controls opening and closing of the line pressure oil passage 82 and the output port 86. The manual valve 94 is a shift lever
L (Low).

S (second), D (drive), neutral to N)
, R (reverse), and P (parking) A second line pressure Pg2, which is positioned in the axial direction in relation to range operation and is output from an output port 258 of a sub-primary valve 254 to be described later, is supplied through the boat 96 at 2172. It roars to the hydraulic actuator 76' that operates the reverse brake 76, to the boat 98 in the L and S ranges, and to the boats 98 and 100 in the D range. The relief valve 102 has a function as a safety valve that releases oil from the line pressure oil passage 82 when the first line pressure P11 of the line pressure oil passage 82 exceeds a predetermined value.

The secondary hydraulic oil passage 104 is connected to the line pressure oil passage 82 via an orifice 106 and a boat 110 from which surplus oil from the primary regulator valve 108 is discharged.
4 to the secondary hydraulic oil line 104, and the connection between the secondary hydraulic oil line 104 and the boat 120 in relation to the oil pressure in the control room 116 and the load of the spring 118. The control is performed to maintain the secondary hydraulic pressure Pz of the secondary hydraulic oil passage 104 at a predetermined value. Lubricant oil passage 122 is connected to secondary hydraulic oil passage 104 via boat 120 and orifice 124 . Lockup control valve 126 selectively connects secondary hydraulic oil passage 104 to the engagement side and release side of lockup clutch 32 in fluid coupling IO. The lock-up solenoid valve 128 controls the opening and closing of the lock-up control valve 1260 between the control chamber 130 and the drain 132, and when the solenoid valve 128 is off (non-energized state), the secondary The secondary hydraulic pressure Pz from the hydraulic oil passage 104 is transmitted, and power is transmitted via the fluid in the fluid coupling 10. However, when the solenoid valve 128 is on (energized state), the secondary hydraulic pressure Pz from the secondary hydraulic oil passage 104 is supplied to the engagement side of the lock-up clutch 32 and the oil cooler 134, and the power is transferred to the lock-up clutch 3.
2. Cooler bypass valve 136 controls cooler pressure.

The speed ratio control device includes a speed change direction switching valve device 138 consisting of a first spool valve 142 and a first solenoid valve 144, and a second spool valve 142 and a first solenoid valve 144.
A variable speed switching valve device 140 including a spool valve 146 and a second electromagnetic valve 148 is provided. First solenoid valve 144
is off, the spool of the first spool valve 142 is pressed toward the spring 152 by the secondary hydraulic pressure Pz of the chamber 150, and the first line pressure Pnl of the boat 154 pushes the boat 156 of the first spool valve 142. The water is sent to boats 1-158 of the second spool valve 146 via the boat 160 and the drain 162 are disconnected.

As a result, the gear ratio γ is switched in the decreasing direction.

During the period when the first solenoid valve 144 is on, the oil pressure P of the chamber 150 is
z is discharged through the drain 164 of the first solenoid valve 1.44, the spool of the first spool valve 142 is pushed towards the chamber 150 by the spring 152, and there is no line pressure PCI in the boat 156 and the boat 160 is connected to drain 162. As a result, the gear ratio is switched in the increasing direction.

During the period when the second solenoid valve 148 is off, the second spool valve 1
The spool 46 is pushed towards the spring 168 by the secondary hydraulic pressure I)2 in the chamber 166, the connection between the boat 158 and the boat 170 is broken, and the boat 172 is connected to the boat 174. The boats 170 and 172 are connected to the input hydraulic cylinder 50 of the CVT 12. Second solenoid valve 148
During the period when the second solenoid valve 148 is on, the oil pressure in the chamber 166 is turned on.
from the drain 176 of the second spool valve 146
The spool of is urged toward chamber 166 by spring 168, and boat 158 is connected to boat 170, and boat 17
2 and the boat 174 are disconnected. Boat 174 is connected to boat 160 via oil line 180. The orifice 182 is connected to the boat 1 when the second solenoid valve 148 is turned off.
Pour a small amount of oil from the 58 into the boat 170. Therefore, during the period when the first solenoid valve 144 is off and the second solenoid valve 148 is on, the input end hydraulic cylinder 50 of the CVT 12
Oil is quickly supplied to the engine, and the gear ratio γ rapidly decreases. The first solenoid valve 144 is off and the second solenoid valve 148
is off, the input hydraulic cylinder 5 of the CVT 12
0 is supplied through the orifice 182, and the gear ratio γ of the CVT 12 gradually decreases. When the first solenoid valve 144 is on and the second solenoid valve 148 is on, oil is not supplied to or discharged from the input hydraulic cylinder 50 of the CVT 12, and the gear ratio γ of the CVT 12 is determined by leakage from the hydraulic cylinder 50. etc., gradually increasing.

During the period when the first solenoid valve 144 is on and the second solenoid valve 148 is off, the oil in the input hydraulic cylinder 50 is discharged from the drain 162, so the gear ratio T of the CV'T'12 increases rapidly. .

The gear ratio detection valve 184 is equipped with a rod 194 that is in sliding contact with the movable rotary body 46 on the input side, and the rod 194 is moved in the axial direction by an amount of displacement equal to the displacement amount of the movable rotary body 46 in the axial direction. . The gear ratio detection valve 184 is the CVT 12
As the amount of displacement of the movable rotary body 46 relative to the fixed rotary body 42 on the input side increases, the discharge flow rate of the oil supplied through the orifice 218 increases. It decreases as it increases. The gear ratio pressure Pr is generated by controlling the discharge amount of the hydraulic medium supplied to the output boat 216.

The cut-off valve 226 is the lock-up control valve 12G.
The chamber 2 communicates with the control chamber 130 via an oil passage 228.
30. and a spool 234 that moves in relation to the oil pressure in its chamber 230 and the spring force of a spring 232, when the solenoid valve 128 is off: 1. That is, when the lock-up clutch 32 is in the released state (when the auxiliary transmission I4 changes gears, the lock-up clutch 32 is released in order to absorb the shock of the power transmission system), the lock-up clutch 32 is in the closed state. This prevents the gear ratio pressure Pr from being transmitted to the primary regulator valve 108.

The primary regulator valve 108 as a first line pressure generating means is connected to a boat 236. to which the throttle pressure P is supplied. A bolt 238 to which the gear ratio pressure Pr is supplied, and a bow 1-240 connected to the line pressure oil passage 82. Bow connected to the suction side of the oil pump 54) 242.
and a first line pressure pH via orifice 244) 246. Spool 2 that moves in the axial direction to control the connection between boat 240 and boat 242
48. a spool 250 that biases the spool 248 toward the boat 238 in response to the throttle pressure p th ; and a spring 25 that biases the spool 248 toward the boat 238
2. The pressure receiving areas of the two lands from the bottom of the spool 248 are Al, A2, and throttle pressure Pth, respectively.
If the pressure receiving area of the land of the spool 250 receiving the pressure is A3, and the acting force of the spring 252 is Wl, the following equations (1) and (2) hold true.

When the cut-off valve 226 is open and the gear ratio pressure Pr is coming to the boat 238, P41=(A3-Pth→-Wl-AI-Pr)/(A
2-Al) ・ ・ ・ ・ ・(11 When the cut-off valve 226 is closed and the gear ratio pressure Pr is not coming to the boat 238, lJ?1-(A3・P+Wl) / (A2-AI
)...(2) The sub-primary valve 254 serving as the second line pressure generating means is connected to the input port 256 to which the first line pressure PAL is introduced. Second line pressure Pff2 is generated (output capo) 258. Boat 260 guided by gear ratio pressure Pr. A second line pressure P12 as a feedback pressure is introduced through an orifice 262 to a boat 264. A spool 266 which controls the opening and closing of the input port 256 and the output port 1-258, and a boat 268 to which the throttle pressure P is guided. A spool 270 that biases the spool 266 toward the boat 260 in response to throttle pressure Pth from the boat 268. and a spring 272 that biases the spool 266 toward the boat 260. The pressure receiving areas of the two lands from the bottom of the spool 266 are B1 and B.
2. If the pressure receiving area of the land of the spool 270 that receives the throttle pressure P is defined as 83, and the elastic force of the spring 272 is defined as W2, then the second line pressure P12 is output according to the following equation (3).

PI = (B3-P, , +W2-111・Pr) /
(82-Bl)...(3) The shift valve 274 is connected to a hydraulic actuator 72'' that operates the high-speed clutch 72 and the low-speed brake 74 of the auxiliary transmission 14, and selects between 74 degrees. It applies hydraulic pressure to the shift lever, S, L.
Input boat 276, output boats 278, 280, orifice 282 to which second line pressure P12 is introduced during range operation
drain oil passage 2 having a drain 284 and terminating in a drain 284;
Boat 288 connected to 86. In the D range, the first line pressure P from the boat 100 of the manual valve 94
Control boat 300 supplied with NI, other control boats 302, 304, drain 306, spool 308,
and a spring 310 that biases the spool 308 toward the control boat 304 . Control boat 302.3
A secondary hydraulic pressure Pz is introduced to the control boats 302 and 304 through an orifice 312, and the hydraulic pressure of the control boats 302 and 304 is controlled by a shift solenoid valve 314. 2 from the bottom of spool 308
The pressure receiving area of each land is Sl.

52, and Sl<S2. Further, the on/off state of the solenoid valve 314 is controlled in relation to the driving parameters of the vehicle.

When spool 308 is in the spring 310 example position, human powered boat 276 is connected to output port 278 and output port 280 is connected to boat 288. Therefore, the second line pressure P! from output port 278! 2 is piston 3
Akiyo with 18.

Hydraulic actuator 7 for mulator 320 and high speed stage
At the same time, the pressure in the hydraulic actuator 74' for the low speed gear is exhausted, and the auxiliary transmission 14 becomes the high gear speed.

When the spool 308 is in the position on the control boat 304 side, the input boat 276 is connected to the output port 280 and the output port 278 is connected to the drain 306 . Therefore, the second line pressure P12 from the output port 280 is supplied to the low-speed hydraulic actuator 74°, and the pressure inside the high-speed hydraulic actuator 72' is exhausted, so that the sub-transmission 14 is shifted to the low-speed gear. becomes.

In the case of the L range and the S range, the first line pressure pH is not introduced to the control boat 300, so the solenoid valve 31
4 is turned off, the spool 308 initially has a pressure receiving area S
By the secondary hydraulic pressure Pz acting on the land of 2, and then by the secondary hydraulic pressure Pz acting on the land of the pressure receiving area S1,
It moves to the spring 310 side, but when the solenoid valve 314 is turned on, the oil pressure of the control bows 302 and 304 decreases, so
The spool 308 moves toward the control bow +-304 according to the biasing force of the spring 310. Therefore, in the (7) range and the S range, the sub-transmission 14 is switched between the high gear and the low gear in response to turning the solenoid valve 314 off and on.

In the D range, the first line pressure P6 is applied to the control boat 3f)0.
1 is guided, so once the spool 308 is in the position on the spring 310 side, the control boat 3 is placed on the land of the pressure receiving area S2.
The first line pressure pH from 00 is applied, and the spool 308 is held at the position on the spring 310 side regardless of whether the solenoid valve 314 is turned on or off thereafter. Therefore, sub-transmission 1
4 is held in high gear.

The shift timing valve 324 has a control boat 326 that communicates with the hydraulic actuator 72'' for the high speed gear, and a spool 328 whose axial position is controlled by the hydraulic pressure of the control boat 326, and the shift timing valve 324 has a spool 328 whose axial position is controlled by the hydraulic pressure of the control boat 326. When upshifting, the amount of oil supplied to the hydraulic actuator 72° for the high speed gear and the amount of oil discharged from the hydraulic actuator 74° for the low speed gear are controlled.

FIG. 5 shows an electronic circuit that controls the operation of the hydraulic control device described above. C equipped with CPU, RAM, ROM, etc.
The electronic control unit 330, which is a computer for VTV, receives information from sensors (not shown) such as throttle valve opening θ, CVT
The rotational speed N of the output shaft 34 of No. 12. 8. (The rotation speed ntj of the input side rotation shaft of the sub-transmission 14, the rotation speed N of the input shaft 26 of the CVTI 2, and the signals representing the operation position of the shift lever are supplied.The CPU in the electronic control unit 330 The solenoid valve 128 processes the input signal according to a program stored in advance in the ROM while utilizing the temporary storage function of the RAM, and controls the lock-up clutch 32, the gear ratio of the CVTI 2, and the gear position of the sub-transmission 14. ，
Signals for driving 144, 148, and 314 are outputted via amplifier 332, respectively.

In the electronic control device 330, when a main routine (not shown) is executed, the electronic control device is initialized in an initialization step, and input signals from each sensor are read in a signal reading step. In addition, in the vehicle speed calculation step, vehicle speed V etc. are calculated based on the read signal, and in the control mode selection step, fail safe control, cranking control, neutral control, shift control, gear ratio, etc. are calculated from the human input signal and data. Various control modes such as control are selected, and routines corresponding to the control modes are executed. When shift control is selected, a shift control routine is executed to change the gear position of the auxiliary transmission 14 to a high gear position or a low speed position in response to the operating position of the shift lever or according to the driving condition of the vehicle. Can be switched to any gear. Also,
When the gear ratio control is selected, a gear ratio control routine is executed to change the gear ratio γ of the CVTI 2 to an optimal value. This gear ratio control determines the optimum target input shaft rotation speed for increasing the efficiency of the engine 8 based on the throttle valve opening θ, vehicle speed ■, etc. from a predetermined relationship, and determines the optimum target input shaft rotation speed. The gear ratio γ of the CVT 12 is adjusted so that the actual rotational speed of the input shaft 26 matches the actual rotational speed of the input shaft 26. The target input shaft rotational speed is determined based on the throttle valve opening .theta. from one of two types of relationships stored in advance in the ROM, each using the vehicle speed (2) as a parameter, as shown in FIG. 9, for example. The above two types of relationships are selected according to the shift position of the sub-transmission 14, that is, the actual gear position, so the target input shaft rotation speed is related to the change in the actual gear position of the sub-transmission I4. It can be changed in two stages. In this way, the target input shaft rotational speed is determined, so at the same throttle valve opening θ, if the auxiliary transmission 14 is in a high gear, the target input shaft rotational speed for high speed・degrees N1−( ) I) is a low speed gear, the target input shaft rotation speed Ni for low speed is brighter than that.
,,'' (L) are determined. Therefore, as shown in FIG. r=n(
It), and in the case of a low gear, γ1. It is varied in the region between X(L) and rmrn(L). The above γ, , X ([+) and γ
, i, (H) are the maximum and minimum values of the gear ratio in the case of high gear, γ, , (L) and γw
in (L) is the maximum value and minimum value of the gear ratio in the case of a low speed gear.

Here, in the shift control, when an upshift operation is performed to change the auxiliary transmission 14 from a low gear to a high gear, the target input shaft for the gear ratio control is By switching the rotational speed from the low-speed target input shaft rotational speed Ni," (1,) to the high-speed target input shaft rotational speed N,," (I()), the shift shock is suppressed. That is, , a part of the main routine is provided with the steps shown in FIG. When it is determined to shift up the auxiliary transmission 14 based on the driving parameters of the vehicle from the pattern, a shift up control routine of step SM2 is executed.In the above main routine, step SM3 is a shift door control routine. This flag is provided to determine the content of flag F indicating that the shift-up control operation is continuing, and if it is determined that the content of flag F is "1" in step SM3, the step described below in the shift-up control routine is executed. SR3 and below will be executed again.

The shift-up control routine is configured as shown in FIG. 1, and the content of the flag F is set to "1" by executing step SRI. After that, step SR2 is executed, and for example, the relationship (Ni,,'' ()I) = of the two types of relationships shown in FIG.
f (θ, ■)) is selected, the target human power shaft rotation speed in the gear ratio control changes from the previous low speed target input shaft rotation speed N+, ”(1,) to a lower high speed. target input shaft rotation speed N,," (II). Then, by executing step SR3, the actual gear ratio T is set to a predetermined constant value γ.
. It is determined whether or not the value has decreased. Above step SR2
Immediately after the execution of The gear ratio T is a predetermined constant value γ. If it is determined that the voltage is lower than can be switched to Then, when step SR5 is executed to clear the contents of the flag F to "0", the shift amplifier control routine is ended and the main routine is returned.

As described above, according to the present embodiment, prior to switching to a high gear in step SR4, the target input shaft rotation speed for gear ratio control is changed to the previous low-speed target input shaft rotation speed Ni in step SR2. ,,” ([,) to lower target input shaft rotation speed Ni,” (I
I), the shift shock caused when a gear train constituting a high-speed gear is newly connected is alleviated compared to the conventional case where such a change in target input shaft rotational speed is not performed. Ru. That is, as shown in FIG. 8, when the vehicle speed is a constant Vo, the target human power shaft rotation speed is A when the auxiliary transmission 14 is in the low gear.
However, by executing step SR2, the target input shaft rotational speed is reduced to a value corresponding to point B, and the rotational speed of the engine 8 is suppressed prior to the actual gear change. Therefore, the rotational speed on the input side of the auxiliary transmission 14 and the inertia torque on the front side of the auxiliary transmission 14 are made smaller than in the past, and the shift shock at the time of upshifting is suitably alleviated. Also, this allows
Drivability is improved, and the load applied to the frictional engagement device during shifting of the sub-transmission is reduced, increasing its durability.

Further, according to this embodiment, the actual gear ratio r in step S R3 is the predetermined value γ.

When it is determined that the target input shaft rotation speed and the actual rotation of the human power shaft 26 are the same, step SR4 for switching the auxiliary transmission 14 to a high gear is executed. There is an advantage in that the shift change is suitably suppressed regardless of the response of the control that causes a loss in speed.

Although one application example of the present invention has been described above, the present invention can also be applied to other aspects.

For example, in the above-described embodiment, step SR3 is provided in the flowchart of FIG. 1, but this step SR4 actually shifts up the sub-transmission 14 when the actual gear ratio T is γ. This is to limit the timing when the following occurs to match the timing with the actual change in the gear ratio T, and does not necessarily need to be provided in the case of shift control types with different characteristics.

Further, instead of the actual throttle valve opening θ, a quantity representing the required output such as an accelerator pedal operation amount, an intake pipe negative pressure, a fuel injection time, etc. may be used. In this way, the present invention is suitably applied even when the vehicle is equipped with a diesel engine that does not use a throttle valve.

In addition, in the gear ratio control of the embodiment described above, the target human power shaft rotation speed is controlled to match the actual rotation speed of the input shaft 26, but the rotation speed of the input shaft 26 and the engine rotation speed are constant. Therefore, the target engine rotation speed and the actual rotation speed of the engine 8 may be controlled to match.

It should be noted that the above description is merely an example of application of the present invention, and the present invention may be modified in various ways without departing from its spirit.

[Brief explanation of the drawing]

FIG. 1 is a flowchart illustrating the main part of the operation of the apparatus to which the present invention is applied. FIG. 2 is a schematic diagram showing a power transmission device for a vehicle to which the present invention is applied. Figure 3 is the second
FIG. 3 is a diagram showing the relationship between the range of the sub-transmission and the frictional engagement device in the device shown in the figure. FIG. 4 is a circuit diagram showing in detail the hydraulic control system for operating the apparatus of FIG. 2; FIG. 5 is a professional line diagram showing the electrical control circuit provided in the apparatus of FIG. 2. FIG. 6 is a diagram showing a speed ratio change range of the belt type continuously variable transmission of FIG. 2, which is controlled by the operation of the electric control circuit of FIG. 5. FIG. 7 shows a main part of a main routine explaining the operation of the electric control circuit shown in FIG. FIG. 8 is a diagram illustrating changes in engine rotational speed during shift amplification of the device shown in FIG. 2. FIG. 9 is a diagram showing the relationship used to determine the target input shaft rotational speed in the gear ratio control of the electric control circuit of FIG. 5. FIG. 12: Belt type continuously variable transmission 14: Sub-transmission γ: Gear ratio N, n'': Target input shaft rotation speed N, 7 = Actual input shaft rotation speed

Claims (1)

[Scope of Claims] In a continuously variable transmission for a vehicle having an auxiliary transmission that can be switched to at least two forward gears, the gear ratio of the continuously variable transmission is such that the engine rotation speed matches a target rotation speed. , while determining a target rotational speed of the engine when the auxiliary transmission is in a low gear than when it is in a high gear, the control method comprising: adjusting the gear of the auxiliary transmission; When switching from a low gear to a high gear, the target rotational speed is switched to a value at which the gear of the auxiliary transmission is in a high gear, prior to switching the gear of the auxiliary transmission. A control method for a continuously variable transmission for a vehicle.