JP2863919B2 - Belt ratio control method for continuously variable transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuously variable transmission belt ratio control method, and more particularly, to a shift control based on at least a previously fixed belt ratio fixed value stored in advance when open loop control is performed. The present invention also relates to a continuously variable transmission belt ratio control method for preventing a belt strip. 2. Description of the Related Art In a vehicle, a transmission is interposed between an internal combustion engine and drive 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. In the transmission, a width of a groove formed between a pulley portion having a fixed pulley portion fixed to a rotating shaft and a movable pulley portion attached to and detachable from the fixed pulley portion is provided. There is a continuously variable transmission that reduces the radius of rotation of a belt wound around a pulley by transmitting power to change the belt ratio (speed ratio). Examples of this continuously variable transmission include, for example, JP-A-57-186656 and JP-A-59-4324.
No. 9, JP-A-59-77159, and JP-A-61-233256. [Problems to be Solved by the Invention] By the way, in the conventional continuously variable transmission belt ratio control method, during normal deceleration or sudden deceleration, the drive mode is switched from the drive mode to the hold mode by a predetermined passing point of the vehicle speed or the engine speed. It has been switched. In general, the belt ratio is set low for the purpose of reducing fuel consumption and taking measures against noise during traveling in the dry mode, and the full low state or the belt ratio is set high in the hold mode. In addition, when the vehicle speed is suddenly decreased by sudden braking and the belt ratio during traveling is in a low state, a rapid ratio change (downshift) is required. Normally, in a belt-driven continuously variable transmission, a change in belt ratio is achieved by moving a movable pulley piece. In the case of a downshift, the primary pressure of the drive-side pulley, which is the input shaft side, is controlled to decrease. In this control, the primary pressure control valve is opened to the atmosphere, and the primary pressure is rapidly reduced. . However, if the pump does not have sufficient excess pressure or the pump pressure is not increased during the downshift, the drive-side pulley moves, and the line of the driven-side pulley as the output shaft side moves. Pressure drops temporarily. For this reason, if the rapid acceleration operation is performed in the above-described temporary decrease in the line pressure, the belt holding force is temporarily insufficient until the predetermined line pressure is reached, causing belt slip and causing belt slip. There is an inconvenience that the service life of the belt or the pulley is shortened due to the wear at the time. [Object of the Invention] Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages by storing an integrated value immediately before switching to open-loop control when switching to open-loop control by deceleration, and storing a ratio fixed value stored in advance. Is corrected by the stored integral value immediately before switching and the predetermined delay constant, and the speed is controlled by the corrected ratio fixed value, whereby the belt holding force can be prevented from lowering, and the belt slip can be reliably prevented. An object of the present invention is to realize a belt ratio control method for a continuously variable transmission that can avoid wear of a belt or a pulley at the time of belt slip and prolong the service life of the belt or a pulley. Means for Solving the Problems In order to achieve this object, the present invention reduces the groove width between a fixed pulley piece and a movable pulley piece which is detachably attached to the fixed pulley piece. The speed change control is performed to reduce and increase the radius of rotation of the belt wound around the two pulleys to change the belt ratio, and to perform the speed change control including at least the integral control in which closed loop control and open loop control are selectively used according to the speed. In the continuously variable transmission control method, when switching to open-loop control is performed by deceleration, the integrated value immediately before switching to open-loop control is stored, and the previously stored fixed value is changed by a predetermined delay from the stored integrated value immediately before switching. It is characterized in that it is corrected by a constant and the shift control is performed by the corrected ratio fixed value. [Operation] According to the above-described invention, when the open loop control is performed due to the deceleration, the integrated value immediately before the open loop control is switched is stored, and the previously stored fixed value is changed to the predetermined integrated value by the stored integrated value immediately before the switched. The gear ratio is corrected by the delay constant, the gear ratio is controlled by the corrected ratio fixed value, the belt holding force is prevented from lowering, and the belt slip is prevented.
The belt and pulley are prevented from being worn when the belt slips, and the service life of the belt and pulley is extended. Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings. 1 to 5 show an embodiment of the present invention. In FIG. 5, 2 is a belt-driven continuous variable transmission, 2A is a belt, 4 is a driving pulley, 6 is a driving fixed pulley piece, 8 is a driving variable pulley piece, 10 is a driven pulley,
Reference numeral 12 denotes a driven-side fixed pulley part, and reference numeral 14 denotes a driven-side variable pulley part. As shown in FIG. 5, the drive-side pulley 4 includes a drive-side fixed pulley piece 6 fixed to a rotating shaft 16,
And a drive-side movable pulley part mounted on the rotary shaft 16 so as to be movable and non-rotatable in the axial direction of the rotary shaft 16. The driven pulley 10 also has a driven-side fixed pulley piece 12 and a driven-side movable pulley piece 14, similarly to the drive-side pulley 4. First and second housings 18 and 20 are mounted on the driving-side movable pulley piece 8 and the driven-side movable pulley piece 14, respectively, to form first and second hydraulic chambers 22 and 24, respectively. . At this time, the second hydraulic chamber 24 on the driven side
There is provided a biasing means 26 comprising a spring or the like for biasing the second housing 20 in the direction of enlargement. An oil pump 28 is provided on the rotating shaft 16. The oil pump 28 communicates with the first and second hydraulic chambers 22 and 24 via first and second oil passages 30 and 32, respectively. Is provided with a primary pressure control valve 34 as a shift control valve for controlling a primary pressure as an input shaft sheave pressure. 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 at a constant pressure (1.5 to 2.0 kg / c).
m ² ), a first 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 4 having a relief valve function for controlling a line pressure as a pump pressure is provided.
Through a fifth oil passage 46, and the line pressure control valve
A second three-way solenoid valve 50 for line pressure control is connected to 44 by a sixth oil 48. Further, a clutch pressure control valve 52 for controlling a clutch pressure is communicated with a seventh oil passage 54 in the middle of the second oil passage 32 closer to the second hydraulic chamber 24 than the portion where the line pressure control valve 4 communicates. An eighth oil passage 56 connects the clutch control valve 52 to a third three-way solenoid valve 58 for clutch pressure control. Further, the primary pressure control valve 34, the first solenoid valve 42 for primary pressure control, the low pressure control valve 38, the sixth oil passage 4
8. The second solenoid valve 50 for line pressure control and the clutch pressure control valve 52 are connected to each other by a ninth oil passage 60. The clutch pressure control valve 52 is connected to the hydraulic
While communicating with the oil passage 64, a pressure sensor 68 is provided in the middle of the tenth oil passage 64 by an eleventh oil passage 66.
To communicate. 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 inspection 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 detection gear 70. Further, an output 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, the first rotation detector 72 and the second
A detection signal from the rotation detector 76 is output to a control unit 82 described later, and the engine speed and the belt ratio are grasped. The hydraulic starting 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 detects the rotation of the reduction gear, the differential, the drive shaft, and the final output shaft directly connected to the tire, and can detect the vehicle speed. Further, the second rotation detector 76 and the third
The rotation detector 80 can also detect rotation around the hydraulic start clutch 62, which contributes to the detection of the clutch slip amount. Further, there is provided a control unit 82 for inputting various conditions such as a throttle opening of a carburetor (not shown) of the vehicle, an engine rotation, a vehicle speed, and the like, and changing a duty ratio to perform shift control.
The first three-way solenoid valve for primary pressure control 42 and the constant pressure control valve 38, the second three-way solenoid valve for line pressure control 50,
In addition, the opening and closing operation of the third three-way solenoid valve 58 for controlling the clutch pressure is controlled, and the pressure sensor 68 is also controlled. The various signals input to the control unit 82 and the functions of the input signals will be described in detail. The shift lever position detection signal... P, R, N, D, L, etc. Required line pressure, ratio, clutch control, carburetor throttle opening detection signal ... Detects engine torque from memory previously input into the program, determines target ratio or target engine speed, and detects carburetor idle position Signal: Improvement of accuracy in correction and control of the carburetor throttle opening sensor, accelerator pedal signal: Detection of the driver's will based on the depression state of the accelerator pedal, determination of the control direction during running or oscillation, brake signal ... … Detects whether the brake pedal has been depressed, determines the control direction, such as disengagement of the clutch. Performance sports of the options signal ...... vehicle (or the economy of)
There is an option to use it. 84 is a piston of the hydraulic oscillation clutch 62, 86 is an annular spring, 88 is a first pressure plate, 90 is a friction plate, 92 is a second pressure plate, 94 is an oil pan, and 96 is an oil filter. The primary pressure control valve 34 has a spool valve that reciprocates in a body (not shown). Further, 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 control unit 82 stores an integrated value immediately before switching to open-loop control when switching to open-loop control due to deceleration, and stores a fixed ratio value stored in advance, a stored integrated value immediately before switching, and a predetermined delay constant. Corrected by
The gear ratio is controlled by the corrected ratio fixed value. That is, the integrated value (XIR) of the ratio fixed value (Null value, RN) in the last ratio fixed state in the shift control immediately before the open loop control switching is stored, and when the open loop control is performed by the deceleration operation, The fixed ratio value (Null value, RN) stored in advance is corrected by the integral value (XIR) and the predetermined delay constant (A), and the shift control, for example, the engine speed is controlled. Here, the belt holding force and the belt slip phenomenon will be described in detail with reference to FIGS. In FIG. 2, T ₁ is engine torque, T ₂ is clutch input torque, T ₃ is clutch output torque,
P is the pump pressure, P _L is the line pressure, P _P is the primary pressure, the P _C shows the clutch pressure. The belt slip occurs due to the belt holding force (axial force, F) generated by the pressure supplied to the movable pulley part, and the belt slipping force (shaft) due to the centrifugal force due to the belt tension and the belt's own weight. force, is due to the balance between Fs), in relation F> F ₃ without belt slip occurs, the belt slip occurs in the relationship F ≦ Fs. The belt holding force due to the pump pressure P is: F ₁ = (P _P , S ₁ , N ₁ ) = K ₁ · P _P · S ₁ −K ₂ / N ₁₂ ^{On the} output shaft side, _{F 2 = (P L, S} 2, N 2) = K 1 · P L · S 2 -K 2 / N 2 2 K 1, K 2: constants S _1, S _2: the pulleys pressure receiving areas N _1, N ₂ : Indicated by the formula of each engine speed. At this time, the engine speed is affected because the first and second hydraulic chambers on the input shaft side are affected by the centrifugal force due to the rotation. However, the centrifugal force is extremely small in the normal engine speed range. So it can be ignored. The axial force that the belt tries to slip is the input torque T ₁ ,
And the belt ratio has a large factor, but can be generally expressed by the following equation. That is, on the input shaft side, On the output shaft side, α ₁ , α ₂ : Belt clamping angle β: Sheave angle R ₁ : Belt radius on the input shaft side μ: Friction coefficient between pulley and belt Φ: Angle at which belt tension at the contact point with the pulley belt changes from maximum to minimum Therefore, [Phi <alpha without belt slip not occur if is ₁ or alpha _2, exchanges work from the belt towards the belt tension if [Phi ≧ alpha ₁ or alpha ₂ opposite to the pulley is insufficient, Belt slip occurs. The axial force at the time of belt slip can be considered as α ₁ = Φ and α ₂ = Φ, and R ₁ is a ratio function (i). Therefore, if μ and β are constants, the above equation can be replaced with F _S1 or F _S2 = (T ₁ , i). To prevent belt slip from occurring, the equation F ₁ = ( P _P , S ₁ , N ₁ )> (T ₁ , i) and F ₂ = (P _L , S ₂ , N ₂ )> (T ₁ , i) must always hold. When the downshift command is input, the primary pressure control valve 34 opens the first hydraulic chamber 22 on the driving side to the atmospheric pressure and lowers the primary pressure. At this time, the belt 2A has a tension by the input torque T ₁ and the second hydraulic chamber 24 side pressure, the primary pressure decreases to move the input shaft side pulley by a belt tension (pushes open), the output shaft for outputting simultaneously side is a large rotation radius belt pressing force by the pressure P _L of the second hydraulic chamber 24 side. The downshift is performed in such an order, and the above two inequalities must be satisfied as conditions for preventing the belt from slipping. Two inequalities, as a factor of the belt slip, or T ₁ is large, i.e. if the engine torque is large, there are two or P rate of change of _P and P _L, that is, abrupt shift changes, the P _P Even if the primary pressure control valve 34 is opened, the rate of change is such that the belt ratio changes even if the primary pressure control valve 34 is opened.
It is necessary to push out the oil inside, but the pressure drop speed becomes slow due to the resistance of the throttle provided in the middle of the passage, and does not change much. Further, since the rate of change of P _L is constant, P _L <P due to the resistance of the throttle if the shift is rapid.
Becomes That is, if the downshift is performed early, the moving speed of the movable pulley increases, so that a large amount of oil needs to be supplied. In general, the relationship between pressure and flow rate is represented by Hagen-Boiseuille's equation: Q = π · ΔP · r / 8 μl Q: flow rate, ΔP: pressure change (decrease), r: pipe radius, μ: fluid viscosity, l: Shown by the length of the pipeline. Therefore, assuming that the pipe area is S, Q∝S ² · ΔP / l, and the portion corresponding to 1 is the stop. Here, when applying the Q continuously variable transmission of the present invention, the amount of oil on the output shaft side from the pump becomes larger and the downshift is fast, corresponds to ΔP = P-P _L, that is, fast downshift The pressure drop is increased. From the above, in general, if the downshift is early, the hydraulic pressure in the second hydraulic chamber on the output shaft side drops, the belt holding force becomes insufficient, and belt slip occurs. Next, determination conditions for each control mode will be described. , Neutral mode... Is determined when the shift lever position is at the N or P position. At this time, the clutch pressure is set to 0 kg / cm ² . , Hold mode, when the shift lever position is R, D, or L,
It is determined when the engine speed is less than 1000 rpm, the clutch output shaft (vehicle speed) is less than 8 kg / H, and the accelerator pedal signal is off when the accelerator pedal is not depressed. At this time, the clutch pressure is determined by feedback control. The duty output signal is controlled so that the target clutch pressure is 3.5 kg / cm ² (clutch engage pressure). , Start mode (Normal)… When the shift lever position is any of the R, D, and L positions,
When clutch output shaft (vehicle speed) is less than 8kg / H, accelerator pedal signal is on, and engine engine speed is 1000rp
It is judged when it is more than m. In the control of the start mode, the engine torque obtained by the throttle opening when the accelerator pedal is depressed is calculated from an engine map (torque value determined by the throttle opening in the engine output characteristic stored in advance). The engine torque value is multiplied by a proportional gain to convert the engine torque value into a clutch pressure value capable of transmitting the determined engine torque (referred to as a feedforward amount). Further, the target engine speed is calculated from the same throttle opening according to the start mode schedule, and the actual engine speed is feedback-controlled to convert the difference from the target value into a clutch pressure value. In the start mode schedule, the engine speed determined by the throttle opening in the engine output characteristics is stored in advance as a map. In the above-described calculation loop, when the actual engine speed is higher than the target engine speed, a calculation value for increasing the clutch pressure to reduce the actual engine speed is calculated (speed loop deviation). Then, a start mode target clutch pressure is determined from the feedforward amount and the speed loop deviation. The actual clutch pressure is controlled by the duty output signal so as to reach the target clutch pressure by feedback control. , Special start mode ..... The judgment is made when the shift lever position is any of R, D, or L and the clutch output shaft (vehicle speed) is 8 kg / H or more. The clutch pressure conversion value is calculated so that the difference between the clutch output shaft speed and the clutch output shaft speed (clutch slip amount) becomes the correction amount Φ. Similarly to the above-described start mode, the actual clutch pressure is adjusted to the target clutch pressure by feedback control. Is controlled by the duty output signal. , Drive mode ... The shift lever position is one of the R, D, and L positions.
It is determined when the clutch output shaft (vehicle speed) is 8 kg / H or more and the clutch slip amount is 20 rpm or less, and the clutch pressure becomes maximum to lock up the clutch. Next, the shift control of the belt-driven continuously variable transmission 2 will be described with reference to FIG. First, a first signal based on a detection signal of the carburetor throttle opening (θ) and a vehicle speed detection signal from the third rotation detector 80 are used.
Obtaining the target engine speed N ₁ (100). And the first
Obtains an error between the actual engine speed N ₂ and the target engine speed N _1, that the error between the first error E1 (102). In this case, in which the duty ratio as in the first error E ₁ becomes larger as a result becomes large, the shift speed opening becomes large in the primary pressure control valve 34 becomes faster. Further, the first error E _1, multiplied by a gain corresponding to the actual engine speed N _2, obtaining a second error E ₂ (104). Then, proportional control by proportional circuit to the second error E ₂ (10
For 6), along with determining the third error E _3, the third error E ₃
Adding the integrated value XIR obtained in integral control (108) by integrating circuit to obtain the fourth error E ₄ (110). Ratio fixed value (Null value, RN) subtracting the fourth error E ₄ from obtaining a fifth error E ₅ (112). Here, the fixed ratio value indicates a duty ratio in a state where the ratio does not change due to the balance between the primary pressure and the line pressure. Said fifth error E ₅ is via the normal (while connected to) the switch SW, converts the fifth error E ₅ to the duty ratio (11
4) The respective solenoid valves are excited by the duty ratio in this conversion period. And in the case of the fifth error
E ₅ is, RN-XIR-E _3, and the further, third error E _{3 is, E 3 = E 2 + C} = E 1 · G · C = (N 1 -N 2) · G · C and be converted, next value XIR (n-1) is, XIR (n-1) = XIR (n) + E 2 · D = XIR (n) + (n 1 -N 2) · G · C XIR (n): previous value C : Proportional constant G: Gain D: Integral constant. Here, in the open-loop control, for example, when there is a command to switch to the full low state, the state is switched from the state where the switch SW is connected to, and the last integrated value XIR (n In addition to subtracting -1), a predetermined delay constant A is subtracted (116), and the calculated value is output to the duty ratio conversion (114) via the switch SW. The resulting value is RN-XIR (n-1) -A, and the open-loop control is performed by the fixed ratio value RN, the integral value XIR (n-1), and the predetermined delay constant A regardless of the engine speed. For this reason, E ₁ = 0 is controlled by feedback control, and E ₃ = 0, and the integrated value XIR at that time means a deviation between the actual fixed ratio value and the fixed ratio value in the program. There are four basic patterns to be described later according to the clutch pressure. 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 is the minimum pressure (zero). Mode: When the shift position is D or R and the throttle is released and there is no driving intention, or when it is desired to decelerate during running and cut off the engine torque, the clutch pressure is low enough to make the clutch contact (3) Start mode ... When the clutch is to be engaged again at the time of starting or after the clutch is disengaged, the clutch pressure is set to an appropriate level (4) according to the engine generated torque (clutch input torque) that prevents the engine from rising and allows the vehicle to operate smoothly. ) Drive mode: Completely running and the clutch is fully engaged If high levels of There are four clutch pressure having a margin to withstand sufficiently the engine torque. The basic pattern (1) is performed by a dedicated switching valve (not shown) interlocked with the shift operation, and the other (2), (3), and (4) are performed by the control unit 82 with the first to third three-way solenoid valves. It is performed by the duty ratio control of 42, 50 and 58. Particularly in the state (4), the seventh oil passage 54 and the tenth oil passage 64 are operated by the clutch pressure control valve 52.
To make the maximum pressure generation state, and the clutch pressure becomes the same as the line pressure. Further, 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 hydraulic pressure from the first to third three-way solenoid valves 42, 50 and 58, respectively, and controls these first to third three-way solenoid valves 42, 50 and 58. The control oil pressure is a constant oil pressure generated by the constant pressure control valve 38. This control oil pressure is always lower than the line pressure, but is a stable and constant pressure. The control oil pressure is also introduced into the control valves 34, 44, and 52 to stabilize the control valves 34, 44, and 52. Accordingly, when the open loop control is performed by the deceleration operation, the open loop control is stored in advance by the last integrated value stored in the last ratio fixed state in the shift control immediately before the open loop control switching and a predetermined excellent constant. The gear ratio can be controlled based on the corrected ratio fixed value, and the corrected gear ratio can be controlled at a constant speed without the influence of variations in the actual machine such as the valve body and pump. , And belt slip can be prevented. Also, without making design changes such as increasing the capacity of the pump or enlarging the passageway, it is possible to eliminate the temporary drop in line pressure during deceleration or sudden deceleration by changing only the software, thereby preventing belt slip, and reducing costs. Can be inexpensive, which is economically advantageous. Further, by changing the delay constant according to various conditions such as the throttle opening and the shift position, the speed of downshift can be arbitrarily controlled, which is practically advantageous. Furthermore, by being able to prevent belt slip,
Wear of the belt and the pulley at the time of belt slip can be prevented, and the service life of the belt and the pulley can be extended. Note that the present invention is not limited to the above-described embodiment, and various application modifications are possible. For example, in the embodiment of the present invention, the shift control is performed by controlling the engine speed when the open-loop control is performed by the deceleration operation. However, the shift control may be performed by controlling the belt ratio. . [Effect of the Invention] As described in detail above, according to the present invention, when the open loop control is performed by the deceleration operation, the integrated value immediately before the switching of the open loop control is stored, and the previously stored ratio fixed value is stored. Is corrected by the integrated value immediately before the switching and the predetermined delay constant, and the shift control is performed by the fixed ratio value after the correction, whereby the integrated value stored immediately before the open-loop control is switched when the open-loop control is performed. Thus, the fixed ratio value stored in advance can be corrected, and gear shift control can be performed based on the corrected fixed ratio value. Thus, a reduction in belt holding force can be prevented, and belt slip can be reliably prevented. In addition, since the wear of the belt and the pulley during the belt slip can be avoided, the service life of the belt and the pulley can be extended, which is economically advantageous. Furthermore, without making design changes such as increasing the capacity of the pump or expanding the passage,
A temporary reduction in line pressure during deceleration or sudden deceleration can be eliminated only by changing the software to prevent belt slip, so that the cost can be reduced and it is economically advantageous. Furthermore, if the delay constant is changed according to various conditions such as the throttle opening and the shift position during the previous shift control based on the integral value, the speed of downshift can be arbitrarily controlled, which is practically advantageous. is there.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 5 show an embodiment of the present invention, FIG. 1 is a block diagram for controlling a belt ratio of a belt-driven continuously variable transmission, and FIG. 2 is a belt-driven continuously variable transmission. FIG. 3 is a schematic enlarged explanatory view of an input / output shaft side, FIG. 4 is a schematic enlarged view of a pulley portion, and FIG. 5 is a block diagram of a belt-driven continuously variable transmission. 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, 30 is a first oil passage, 32 is a second oil passage, and 34 is a primary pressure control valve. , 36 is a third oil passage, 38 is a constant pressure control valve, 40 is a fourth oil passage, 42 is a first three-way solenoid valve, 44 is a line pressure control valve, 46 is a fifth oil passage, 48 is a sixth oil passage, 50 is a second three-way solenoid valve, 52 is a clutch pressure control valve, 54 is a seventh oil passage, 56 is an eighth oil passage, 58 is a third three-way solenoid valve, 60 is a ninth oil passage, 62 is a hydraulic starting clutch, 64 is a tenth oil passage, 66 is an eleventh oil passage, 68 is a pressure sensor, 70 is an input shaft rotation detection gear, 72 is a first rotation detector, 74 is an output shaft rotation detection gear, and 76 is a second rotation detector , 80 is a third rotation detector, 82 is a control unit, and 96 is an oil filter.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yoshinobu Yamashita               4590 Maisaka, Maisaka-cho, Hamana-gun, Shizuoka Prefecture (72) Inventor Takumi Tatsumi               840 Chiyoda-cho, Himeji-shi, Hyogo Mitsubishi Electric               Machine Himeji Works (72) Inventor Hiroaki Yamamoto               6 Sadahoncho, Himeji City, Hyogo Prefecture Mitsubishi Electric Corporation               Control Software Co., Ltd. Himeji               Inside the office                (56) References JP-A-62-191239 (JP, A)

Claims (1)

(57) [Claims] The width of the groove between the fixed pulley part and the movable pulley part attached to and detachable from the fixed pulley part is reduced to increase the radius of rotation of the belt wound around the two pulleys, thereby changing the belt ratio. In the continuously variable transmission control method for performing a shift control including at least an integral control in which a closed-loop control and an open-loop control are selectively used according to a speed while controlling the shift, the open-loop control is performed when switching to the open-loop control is performed by deceleration. An integrated value immediately before switching is stored, a fixed ratio value stored in advance is corrected by the stored integrated value immediately before switching and a predetermined delay constant, and shift control is performed based on the corrected ratio fixed value. Belt ratio control method for continuously variable transmission.