JPH02146366A - Belt ratio controller for continuously variable transmission - Google Patents

Abstract

PURPOSE:To prevent the sudden increase of the primary pressure in the case of a car velocity being more than a predetermined value at the time of a normal start mode, by conducting the changeover action of control from an open loop to a closed loop, and controlling a belt ratio. CONSTITUTION:A control mode RATMOD controlling in feedback a belt ratio and a control mode RNEMOD controlling in feedback an engine revolution number, are sought by multiplying by proportion gains 102, 108 deviations 100, 106 between a target ratio value RATSP and a target engine revolution number NESPR and their respective actual values. And in the case of a car velocity having become more than a predetermined value at the time of a normal start mode, an RDIMOD is changed over to a feedback control side, and an output duty DPWRAT which is in accordance with a deviation 122 between a value processed 114, 116, 118 in PI control and a ratio solenoid narrow duty value, is outputted, and oil pressure is supplied to a primary sheave. Thus, the sudden increase of the primary pressure is prevented, and the occurrence of hunting can be avoided.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a belt ratio control device for a continuously variable transmission, and in particular controls the belt ratio by switching between open-loop control and closed-loop control depending on the vehicle driving condition. The present invention relates to a belt ratio control device for a continuously variable transmission.

[Prior Art] In a vehicle, a transmission is interposed between an internal combustion engine and drive wheels. This transmission changes the driving force and running speed of the drive wheels in accordance with the widely varying running conditions of the vehicle, thereby allowing the internal combustion engine to fully demonstrate its performance. The transmission device 1 is formed between both pulley parts of a pulley having a fixed pulley part fixed to a 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. There is a continuously variable transmission that transmits power by increasing or decreasing the rotation radius of a belt wrapped around a pulley by increasing or decreasing the width of a groove, thereby changing the speed ratio (belt ratio). As this continuously variable transmission, for example, JP-A-57-18E! 65
No. 8, JP-A-59-43248, JP-A-59
These are disclosed in Japanese Patent Application Laid-open No. 81-233256 and Japanese Patent Application Laid-open No. 81-233256, respectively.

[Problems to be Solved by the Invention] By the way, in the conventional belt ratio control device for a continuously variable transmission, the ratio is adjusted to full load depending on the characteristics of the ratio solenoid duty and the primary pressure of the continuously variable transmission.
In order to set F/L, the duty is set lower than the ratio solenoid null duty value NNOMR.

At this time, when the ratio is set to full low F/L in the normal start mode, the ratio solenoid is driven at a duty of 0% to perform oven loop control RDIMOD.

Then, when the clutch slip CLUSLP becomes smaller than the clutch slip trigger value C8TR, a shift is made to the drive mode, but the shift control in this drive mode is a closed loop control RNEMOD that feedback controls the engine speed NE, and the duty is also controlled by an intermediate duty centering on the ratio solenoid duty value NNOMR.

Therefore, as shown in Fig. 4, when the normal start mode shifts to the drive mode, the ratio solenoid is driven with a duty of 0% in the normal start mode, so oil is not supplied to the primary sheave, resulting in a normal start. Simultaneously with the transition from the mode to the drive mode, the speed change control changes from oven loop control to closed loop control, and the duty also changes from 0% to an intermediate duty.

Further, the ratio is controlled in the direction of overdrive O/D by changing the speed change control state to closed loop control.

However, due to the increased volume of the primary sheave,
A large oil flow rate is required during speed change control, and a relatively long time is required from when the drive duty of the ratio solenoid changes until the ratio actually changes.

For this reason, the engine speed NE becomes the target engine speed N.
It becomes difficult to converge to ESPH, the integral value is accumulated, and the sixth
As shown in the figure, oil is suddenly supplied to the primary sheave at location A, causing the line pressure to fluctuate and the clutch pressure that divides the line pressure to fluctuate as well, causing various problems in clutch control. There is.

Furthermore, due to the large difference between the target engine speed NFSPR and the engine speed NE, there is a problem that the engine speed NE may cause hunting, which may cause fluctuations in the vehicle speed NCO.

[Object of the Invention] Therefore, in order to eliminate the above-mentioned disadvantages, an object of the present invention is to provide a belt ratio control device of a continuously variable transmission with oven loop control when the vehicle speed exceeds a predetermined value in the normal start mode. By providing a control unit that switches from to closed-loop control and controls the belt ratio, the control unit supplies oil to the primary sheave to prevent a sudden increase in primary pressure when transitioning from normal start mode to drive mode. This reduces the occurrence of hunting in drive mode by preventing the influence on line pressure and clutch pressure, and allows the engine speed to quickly converge to the target engine speed. The objective is to realize a belt ratio control device for a continuously variable transmission that can be handled only by improving the above.

[Means for Solving the Problems] In order to achieve this object, the present invention provides for a fixed pulley part and a movable pulley part attached to the fixed pulley part so as to be able to move toward and away from the fixed pulley part. In a belt ratio control device for a continuously variable transmission, the belt ratio control device for a continuously variable transmission performs speed change control to change the gear ratio by increasing/decreasing the rotation radius of the belt wound around both pulleys by decreasing/increasing the groove width of the belt. The present invention is characterized in that it includes a control section that controls the belt ratio by switching from oven loop control to closed loop control when the belt ratio exceeds the value.

[Function] According to the above-described invention, when the vehicle speed exceeds a predetermined value in the normal start mode, the control section switches from oven loop control to closed loop control, controls the belt ratio, and switches the belt ratio to the primary sheave. It supplies oil, prevents a sudden increase in primary pressure when transitioning from normal start mode to drive mode, prevents influence on line pressure and clutch pressure, reduces hunting in drive mode, and reduces engine speed. quickly converges to the target engine speed, and this can be done by only making some improvements to the program in the control section.

[Examples] Examples of the present invention will be described in detail below based on the drawings.

1 to 5 show embodiments of this invention. Fourth
In the figure, 2 is a belt-driven continuously variable transmission, 2A is a belt, 4 is a driving pulley, 6 is a driving side fixed pulley part, 8 is a driving side movable pulley part, 10 is a driven pulley, 12 14 is a driven side fixed pulley part, and 14 is a driven side movable pulley part. As shown in FIG. 4, the drive-side pulley 4 includes a drive-side fixed pulley piece 6 fixed to the rotation shaft 16, and a drive-side fixed pulley piece 6 fixed to the rotation shaft 16 so as to be movable in the axial direction of the rotation shaft 16 but not rotatable. It has a drive side movable pulley piece 8. Further, similarly to the drive pulley 4, the driven pulley 10 also includes a fixed driven pulley piece 12 and a movable driven pulley piece 14.

First and second housings 18.20 are attached to the drive side movable pulley piece 8 and the driven side movable pulley piece 14, respectively, and first and second hydraulic chambers 22.24 are formed, respectively. . At this time, a biasing means 26 made of a spring or the like is provided in the second hydraulic chamber 24 on the driven side to bias the second housing 20 in the direction of expansion of the second hydraulic chamber 24.

An oil pump 28 is provided on the rotating shaft 16, and the oil pump 28 is connected to the first and second hydraulic chambers 22,24.
The first oil passages 30 and 30 communicate with each other through second oil passages 30 and 32, and a primary pressure control valve 34, which is a speed change control valve, that controls the primary pressure, which is the input shaft sheave pressure, is interposed in the middle of the first oil passage 30. In addition, a line pressure (generally 5 to 25 kg/c
+m'') to a constant pressure (3 to 4 kg/cs2) is communicated with the primary pressure control valve 3.
4 is communicated with a first three-way solenoid valve 42 for primary pressure control through a fourth oil passage 40.

Further, a line pressure control valve 4 having a relief valve function for controlling the line pressure, which is the pump pressure, is disposed in the middle of the second oil passage 32.
4 is communicated through a fifth oil passage 46, and a second three-way solenoid valve 50 for line pressure control is communicated with this line pressure control valve 44 through a sixth oil passage 48.

Furthermore, a clutch pressure control valve 52 for controlling clutch pressure is installed in the seventh oil passage 5 in the middle of the second oil passage 32 on the side of the second hydraulic chamber 24 than the communicating portion of the line pressure control valve 44.
4, and a third direction solenoid valve 58 for clutch pressure control is connected to this clutch pressure control valve 52 through an eighth oil passage 66.
Communicate.

Further, the primary pressure control valve 34, the first solenoid valve 42 for primary pressure control, the constant pressure control valve 38, the sixth oil passage 48, the second solenoid valve 50 for line pressure control, and the clutch pressure control valve 52 are connected to a ninth oil The passages 60 communicate with each other.

The clutch pressure control valve 52 is communicated with the hydraulic start clutch 62 through a tenth oil passage 64, and a pressure sensor 68 is communicated with the tenth oil passage 64 through an eleventh oil passage 66. This pressure sensor 68 can directly detect the oil pressure when controlling the clutch pressure in hold and start modes, and contributes to instructing the detected oil pressure to be the target clutch pressure. Furthermore, since the clutch pressure becomes equal to the line pressure in the drive mode, it also contributes to line pressure control.

An input shaft rotation detection gear 70 is provided on the outside of the first housing 18.
A first rotation detector 72 on the input shaft side is provided near the outer peripheral portion of the input shaft rotation detection gear 70. Further, an output shaft rotation detection gear 74 is provided on the outside of the second housing 20, and a second rotation detector 76 on the output shaft side is provided near the outer peripheral portion of the output shaft rotation detection gear 74. Detection signals from the first rotation detector 72 and the second rotation detector 76 are output to a control section 82, which will be described later, to determine the engine rotation speed and 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. In other words, this third
The rotation detector 80 detects the rotation of the final output shaft directly connected to the reduction gear, the differential, the drive shaft, and the tires.
Vehicle speed can be detected. Further, the second rotation detector 7
6 and the third rotation detector 80, the hydraulic starting clutch 6
It is also possible to detect rotations around 2, which contributes to detecting the amount of clutch slip.

Furthermore, various conditions such as a throttle opening of a carburetor (not shown) of the vehicle, engine rotation from the first to third rotation detectors 72, 76, 80, vehicle speed, etc. are input, and the duty ratio is changed to perform gear change control. The controller 82 controls the first three-way solenoid valve 42 and 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 58 for clutch pressure control. It is configured to control the opening/closing operation and also control the pressure sensor 68. In addition, the various signals input to the control section 82 and the functions of the input signals are as follows: (1) Shift lever position detection signal...Request is made to each range by each range signal such as PlRlN, DlL, etc. Line pressure and ratio, clutch control, carburetor throttle opening detection signal...
Detects engine torque from memory input into the program in advance, determines target ratio or target engine speed, detects signal for carburetor idle position...Improves accuracy in correction and control of carburetor throttle opening sensor ■, Accelerator pedal signal: Detects the driver's intention based on the state of depression of the accelerator pedal, and determines the control direction when driving or starting ■, Brake signal: Brake pedal depression operation Detects the absence of the vehicle and determines the direction of control such as clutch disengagement■, Power mode obsilon signal...It is used as an option to make the performance of the vehicle more sporty (or more economical).

The control unit 82 is configured to control the belt ratio by switching from open loop control to closed loop control when the vehicle speed NCO exceeds a predetermined value when the vehicle operating state is in the normal start mode.

More specifically, the control unit 82 inputs a detection signal of the vehicle speed NCO, and sets the vehicle speed trigger value N at which the vehicle speed NCO is a predetermined value.
When the speed exceeds C0TR, the speed change control method is changed from open loop control to closed loop control even in the normal start mode.

Note that 84 is a piston of the hydraulic start clutch 62, and 86
is an annular spring, 88 is a first pressure coupler, 90 is a Frixilon plate, 92 is a second pressure coupler, 94
is an oil pan, and 96 is an oil filter.

Next, the effect will be explained.

As shown in FIG. 4, in the belt-driven continuously variable transmission 2, an oil pump 28 located on the rotating shaft 16 operates in response to the drive of the rotating shaft 16, and the oil is pumped into an oil pan 94 at the bottom of the transmission. is absorbed through the oil filter 96. The line pressure, which is this pump pressure, is controlled by the line pressure control valve 4.
4, the amount of leakage from this line pressure control valve 44,
In other words, if the amount of relief from the line pressure control valve 44 is large, the line pressure will be low, and if it is small, the line pressure will be high.

Further, the line pressure control valve 44 has a shift control characteristic that performs three-stage control by varying the line pressure in a full low state, a full over top state, and a fixed ratio state.

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 in accordance with the operation of the second three-way solenoid valve 50. , the second three-way solenoid valve 50 is controlled at a duty rate of a constant frequency. That is, when the duty rate is 0%, the second three-way solenoid valve 50 does not operate at all, the output side is connected to the atmosphere, and the output oil pressure is zero. Furthermore, when the duty rate is 100%, the second three-way solenoid valve 50 operates, the output side is connected to the atmosphere side, and the maximum output oil pressure is the same as the control pressure, and the output oil pressure is varied depending on the duty rate. Therefore, the characteristics of the second three-way solenoid valve 50 are approximately linear, and the line pressure control valve 44 can be operated in an analog manner, and the duty rate of the second three-way solenoid valve 55 can be changed arbitrarily. Line pressure can be controlled.

Further, the operation of the second three-way solenoid valve 50 is controlled by the control section 82.
controlled by. .

The primary pressure for speed change control is provided by the primary pressure control valve 3.
Similarly to the line pressure control valve 44, the operation of the primary pressure control valve 34 is also controlled by a dedicated first three-way solenoid valve 42. This first three-way solenoid valve 42 is used to conduct the primary pressure to the line pressure or to conduct the primary pressure to the atmosphere side,
The belt ratio is caused to shift to the full overdrive side by conducting to the line pressure, or to the full low side by conducting to the atmosphere side.

The clutch pressure control valve 52 that controls the clutch pressure is connected to the line pressure side when the maximum clutch pressure is required, and connected to the atmosphere side when the minimum clutch pressure is required. As with the line pressure control valve 44 and the primary pressure control valve 34, the operation of this clutch pressure control valve 52 is also controlled by a dedicated third three-way solenoid valve 58, and the explanation thereof will be omitted.

Clutch pressure varies within a range from minimum atmospheric pressure (zero) to maximum line pressure.

There are four basic patterns for clutch pressure control, which will be described later.These basic patterns are: (1) Neutral mode: When the shift position is N or P and the clutch is completely disengaged, the clutch pressure is the lowest. Pressure (zero) (2),
Hold mode: When the shift position is D or R and you release the throttle and have no intention of driving, or when you want to decelerate and cut off the engine torque while driving, the clutch pressure is set to a low level that the clutch contacts ( 3) Start mode: When starting or when trying to re-engage the clutch after the clutch has been disengaged, the clutch pressure is adjusted to prevent the engine from revving up and to maintain engine-generated torque (clutch input) that allows the vehicle to operate smoothly. (torque)), drive mode...When transitioning from a complete driving condition and the clutch is fully engaged, the clutch pressure should be high enough to withstand the engine torque. There are four levels. (1) of this basic pattern is performed by a dedicated switching valve (not shown) that is linked to the shift operation, and the other (2), (3), and (4) are performed by the first control valve controlled by the control section 82.
- It is performed by duty rate control of the third-way solenoid valve 42, 50, 58. Particularly in the state (4), the clutch pressure control valve 52 controls the seventh oil passage 54 and the tenth oil passage.
It communicates with the oil passage 64 to create a maximum pressure generation state, and the clutch pressure becomes the same as the line pressure.

In addition, the primary pressure control valve 34 and the line pressure control valve 4
4, and the clutch pressure control valve 52 is controlled by the output oil pressure from the first to third three-way solenoid valves 42.50, respectively.
．． The control oil pressure for controlling the pressure control valve 58 is a constant oil pressure output produced by a constant pressure control valve 38. This control oil pressure is always higher than the line pressure, but it is a stable and constant pressure. In addition, the control oil pressure is controlled by each control valve 34, 44.
52 is also introduced to stabilize these control valves 34, 44, and 52. - Next, electronic control of the belt-driven continuously variable transmission 2 will be explained.

Continuously variable transmission 2 is hydraulically controlled, and in response to commands from control unit 82, appropriate line pressure for belt retention and torque transmission, primary pressure for changing gear ratio, and clutch engagement are ensured. Clutch pressure is secured for each.

Belt ratio control of the belt-driven continuously variable transmission 2 will be explained with reference to FIG.

First, the target ratio value RATSP and the target engine speed NFSPR are determined by a method not shown, and the error between these target ratio value RATSP and the target engine speed NFSPR is determined.

In other words, the target ratio value RATSP is the target ratio value RA
Find the error between TsP and belt ratio RATC (100
), this error is multiplied by a proportional gain (102), and a control mode RATMOD for feedback controlling the belt ratio RATC with respect to the target ratio value RATSP determined from the throttle opening degree and vehicle speed is determined (104).

Further, the target engine speed NFSPR is determined by calculating the error between the target engine speed NFSPR and the actual engine speed NE (106). At this time, when the error becomes large, the duty ratio becomes large as a result, the opening degree of the primary pressure control valve 34 becomes large, and the speed change speed becomes faster. The error is multiplied by a proportional gain (108) to obtain the target engine speed NFS determined from the throttle opening and vehicle speed.
A control mode RNEMOD for feedback controlling the engine speed for PR is determined (110).

Then, the target ratio M to be set in the ratio control mode
The control mode RATMOD performs feedback control of the belt ratio RATC with respect to RATSP, and the control mode RNEMOD performs feedback control of the engine speed with respect to the target engine speed NFSPH (112).

Furthermore, there are two control modes RATMOD.

The error of either RNEMOD is multiplied by the proportional gain (114), and after comparing this value with the value obtained by multiplying this value by the integral gain (11B) and performing the integral processing (118), utility value) and calculate the error (120).

Then, depending on whether or not the control mode RDIMOD is in which the ratio solenoid is driven with a constant duty value, -error and duty value are selected (122).
The output duty is 0PWRAT, and each electromagnetic valve is excited by this output duty 0PWRAT.

A flowchart for controlling the belt ratio of the belt-driven continuously variable transmission 2 will be explained with reference to FIG.

First, the belt ratio control program is started by driving the belt-driven continuously variable transmission 2) (200
) let.

Next, it is determined whether the driving state of the vehicle is in the normal start mode (202), and if YES, the clutch slip CLUSLP and the clutch slip trigger value C8T are determined.
Compare L with R (204), and if NO, it is determined whether or not it is the drive mode (206).

Then, in the comparison (204) between clutch slip CLUSLP and clutch slip trigger value C8TR, C
If LUSLP>C8TR, compare the vehicle speed NCO and the vehicle speed trigger value NC0TR (208), and
If P≦C8TR, it is determined that the clutch is engaged, and the normal start mode is set to the drive mode (210), and the shift control method is controlled to feedback control the engine speed NE with respect to the target engine speed NFSPR. Mode RNEMO
D, and the engine speed NE is controlled in a closed loop to the target engine speed NFSPR determined based on the driving schedule.

Also, compare vehicle speed NCO and vehicle speed trigger value NC0TR (
In 20B), if NCO<NC0TR, the duty is set to 0% (212) L, and the process is shifted to return (218) as open loop control.

Then, in the case of NCO≧NC0TR in the comparison (208), the control mode RATMOD is set (214
)L,, Closed loop control is performed with the target of ratio full low - F/L, and then the process moves to return (218). Oil is supplied to the primary sheave through this closed loop control, and the primary pressure rises slightly as shown by the dashed line in FIG.

Furthermore, in the case of No in the above-mentioned drive mode determination (208), the process moves to return (218),
If YES, the control mode RNEMOD is set (21B)u for feedback controlling the engine speed with respect to the target engine speed determined by the throttle opening degree and vehicle speed, and then the process is shifted to return (218).

Furthermore, after setting the drive mode described above (210), the control mode RNEMOD is set (210), which performs feedback control of the engine speed with respect to the target engine speed determined by the throttle opening and vehicle speed.
18)・L, After that, the process moves to return (218).

Also, to explain Fig. 3, it shows the relationship between the duty ratio and pressure of each control valve, and shows the ratio shift point NN
At a duty value exceeding OMR (ratio solenoid duty value), the pressure in the input shaft sheave becomes greater than the pressure in the output shaft, and the gear shift shifts from full low to full overdrive. At a duty value below the ratio shift point NNOMR (ratio solenoid duty value), a downshift occurs in the opposite direction, and when the ratio is in a full low state, it is fixed at full low.

As a result, if the vehicle speed NCO becomes equal to or higher than the vehicle speed trigger value NC0TR when the vehicle operating state is in the normal start mode, the open-loop control is switched to the closed-loop control, oil is supplied to the primary sheave, and the normal start mode is set. It is possible to prevent a sudden increase in primary pressure at the time of transition from to drive mode, without affecting line pressure or clutch pressure, and to reduce the occurrence of hunting in drive mode, which is advantageous in practice.

Additionally, by preventing a sudden increase in primary pressure when the vehicle operating state changes from normal start mode to drive mode, the engine speed can quickly converge to the target engine speed, improving vehicle stability. can be done.

Furthermore, since the problem can be solved by improving only a part of the program in the control section 82, the configuration does not become complicated or large, and it is easy to manufacture, and the cost can be kept low, which is economically advantageous. It is.

[Effects of the Invention] As explained in detail above, according to the present invention, the belt ratio control device of a continuously variable transmission switches from open-loop control to closed-loop control when the vehicle speed exceeds a predetermined value during normal start mode. A control unit is provided that switches to control and controls the belt ratio, so when the vehicle speed exceeds a predetermined value, it switches from open-loop control to closed-loop control, supplies oil to the primary sheave, and returns to normal start mode. It is possible to prevent a sudden increase in primary pressure at the time of transition from to drive mode, and it is possible to reduce the occurrence of hunting in drive mode without affecting line pressure or clutch pressure.

Additionally, by preventing a sudden increase in primary pressure when the vehicle operating state changes from normal start mode to drive mode, the engine speed can quickly converge to the target engine speed, improving vehicle stability. can be done. Furthermore, since the problem can be solved by only improving a part of the program in the control section, the configuration does not become complicated and the cost can be kept low, which is economically advantageous.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, and FIG. 1 is an explanatory diagram for calculating a target engine speed and a target ratio value, and FIG.
Figure 3 is a flowchart for ratio control of a belt-driven continuously variable transmission, Figure 3 is a diagram showing the relationship between pressure and duty rate in each control valve, Figure 4 is a block diagram of a belt-driven continuously variable transmission, FIG. 5 is a time chart when shifting from normal start mode to drive mode. FIG. 6 is a time chart showing the prior art of the present invention when transitioning from the normal start mode to the drive mode. In the figure, 2 is a belt-driven continuously variable transmission, 2A is a belt, 4 is a driving pulley, 10 is a driven pulley, 3
0 is the first oil passage, 32 is the second oil passage, 34 is the primary pressure control valve, 36 is the third oil passage, 38 is the constant pressure control valve, 40 is the fourth oil passage, 42 is the first three-way solenoid valve, 44 46 is the line pressure control valve, 46 is the fifth oil passage, and 48 is the line pressure control valve.
is the sixth oil passage, 50 is the second three-way solenoid valve, 52 is the clutch pressure control valve, 54 is the seventh oil passage, 56 is the eighth oil passage, 58 is the third three-way solenoid valve, 60 is the eighth oil passage, 62 is a hydraulic starting clutch, 64 is a 10th oil passage,
66 is an eleventh oil passage, 68 is a pressure sensor, 72 is a first rotation detector, 76 is a second rotation detector, 80 is a third rotation detector, 82 is a control unit, 94 is an oil pan, and 96 is an oil filter. It is. Patent Applicant: Meiki Jidosha Kogyo Co., Ltd. Patent
Applicant Mitsubishi Electric Co., Ltd. Agent Patent Attorney
Yoshimi Saigo Figure 4 Figure 5 Figure 6 Procedural Dispute Manual (self-motivated) April 17, 1989 1, Indication of the case Patent Application No. 1983-297811 2, Name of the invention Continuously variable transmission Belt ratio control device 3, relationship with the amended person case Patent applicant address 300 Takatsuka, Kamimura, Hamana-gun, Shizuoka Prefecture Name (2)
08) Lead Automobile Industry Co., Ltd. (etc./powder 4, agent 〒101'lit 03-29
2-4411 (Representative) Address: 2-8-7, Kanda Ogawa-cho, Chiyoda-ku, Tokyo, Contents of amendment (1), page 15, line 9 of the specification, ``...on the atmospheric side...''
"..." is corrected to "...on the output side...". (2) "Clutch pressure..." on page 17, line 9 of the specification.
・" is corrected to "Clutch pressure is...". 6. Subject of amendment (1) Detailed description of the invention in the specification

Claims (1)

[Claims] 1. The radius of rotation of the belt wound around both pulleys can be increased by decreasing or increasing the groove width between the fixed pulley piece and the movable pulley piece that is attached to the fixed pulley piece so as to be able to move toward and away from the fixed pulley piece. In a belt ratio control device for a continuously variable transmission that performs gear change control to increase or decrease the gear ratio, if the vehicle speed exceeds a predetermined value during normal start mode, the system switches from open-loop control to closed-loop control. A belt ratio control device for a continuously variable transmission, characterized in that a control section for controlling a belt ratio is provided.