JP2821536B2 - Control device for continuously variable transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a primary pulley and a secondary pulley with variable pulley spacing, in which a drive belt composed of a metal band and a plurality of elements is wound, and a hydraulic cylinder of each pulley is provided. The present invention relates to a control device for a continuously variable transmission that performs a continuously variable transmission by changing a winding diameter of a drive belt by controlling a line pressure acting on a transmission belt based on an output signal from a control unit.

[Conventional technology]

In this type of continuously variable transmission, a drive belt is wound between a primary pulley on the input side and a secondary pulley on the output side, and the distance between the pulleys is changed by a hydraulic servo mechanism with line pressure. It is designed to automatically change the speed continuously. In this case, the line pressure is controlled so as to be high in the low speed stage where the transmission torque is large and to decrease as the speed stage is high, in order to prevent the drive belt from slipping, and to always maintain the pulley pressing force commensurate with the transmission torque. Things.

By the way, if the line pressure does not follow particularly during acceleration and deceleration of the engine, a slip phenomenon occurs in the drive belt, wear and damage of each pulley and the drive belt occur, and an appropriate gear ratio cannot be obtained.

Therefore, belt slippage is detected from a change in the relationship between the torque of the input shaft and the torque of the output shaft due to an increase or decrease in the line pressure.
JP-A-58-214054 discloses that the line pressure is controlled to a minimum value at which a predetermined torque transmission by a belt is ensured. It is also disclosed in Japanese Patent Laid-Open Publication No. Heisei 1 to determine a slip on the basis of a speed ratio obtained from the strokes of the primary pulley and the secondary pulley and a speed ratio obtained from the rotation speed of each pulley, and to set the line pressure to a predetermined pressure in accordance with the number of slips. -266355.

[Problems to be solved by the invention]

By the way, as shown in the above prior arts, when the belt slip is obtained by detecting the rotation speed of each pulley, the belt slip which cannot be avoided from the structure of the drive belt and the belt slip when the load changes are detected. There is a problem that it is not possible.

On the other hand, focusing on the fact that the drive belt is composed of a metal band and a plurality of elements, the belt speed of the drive belt can be detected, and a highly accurate belt is determined from the target belt speed and the actual belt speed. It is possible to grasp the slip.

The present invention has been made in view of such a point, and in a continuously variable transmission driven by a metal belt, a line pressure is controlled based on a belt slip change amount of a drive belt to prevent the drive belt from slipping. It is an object to provide a control device for a step transmission.

[Means for solving the problem]

In order to achieve the above object, the present invention provides: (1) a drive belt composed of a metal band and a plurality of elements is wound around a primary pulley and a secondary pulley with variable pulley spacing, and acts on a hydraulic cylinder of each of the pulleys. A belt speed detecting means for detecting a belt speed of the drive belt in a continuously variable transmission in which the line pressure is controlled on the basis of an output signal from a control unit to change the winding diameter of the drive belt and change the speed continuously. The control unit is configured to correct a target line pressure of a line pressure acting on a hydraulic cylinder of each of the pulleys when slippage of the drive belt occurs. Target belt speed calculating means for calculating the belt speed, actual belt speed calculating means for calculating the actual belt speed, and target belt speed And a belt slip change amount calculating means for calculating a slip change amount of the drive belt from the actual belt speed. (2) a belt speed detecting means for detecting a belt speed of the drive belt; A displacement sensor for detecting a distance between an element of the belt and the electromagnetic pickup; and a driving unit for always maintaining a distance between the electromagnetic pickup and the element of the drive belt within a predetermined range. ing.

[Action]

Based on the above configuration, during operation of the continuously variable transmission, the target belt speed and the actual belt speed of the drive belt are constantly calculated, and the target line pressure is corrected based on the amount of change between the target belt speed and the actual belt speed. . Thus, slip of the drive belt is prevented, the durability of each pulley and the drive belt is improved, and drivability with excellent responsiveness is obtained.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, an outline of a drive system of a belt-type continuously variable transmission with a lock-up torque converter will be described. Reference numeral 1 denotes an engine, and a crankshaft 2 is configured to be sequentially transmitted to a torque converter device 3, a forward / reverse switching device 4, a continuously variable transmission 5, and a differential device 6.

In the torque converter device 3, the crankshaft 2 is connected to the converter cover 11 and the pump impeller 12 a of the torque converter 12 via the drive plate 10. A turbine runner 12b of the torque converter 12 is connected to a turbine shaft 13, and a stator 12c is guided by a one-way clutch 14. A lock-up clutch 15 integrated with the turbine shaft 13 is installed between the converter cover 11 and the engine power to transfer the engine power to the torque converter 12 or the lock-up clutch.
Communicate through 15.

The forward / reverse switching device 4 has a double pinion type planetary gear 16. The input side sun gear 16 a is connected to the turbine shaft 13, and the output side carrier 16 b is connected to the primary shaft 20. A forward clutch 17 is provided between the sun gear 16a and the ring gear 16c, a reverse brake 18 is provided between the ring gear 16c and the case, and the planetary gear 16 is integrated with the forward clutch 17 to form the turbine shaft 13 and the primary shaft. Connect directly to 20. Further, the reverse power is output to the primary shaft 20 by the engagement of the reverse brake 18, and the planetary gear 16 is made free by releasing the forward clutch 17 and the reverse brake 18.

The continuously variable transmission 5 includes a primary pulley 22 having a hydraulic cylinder 21 on a primary shaft 20 and a variable pulley interval, and a secondary pulley 25 also having a hydraulic cylinder 24 on a secondary shaft 23. A drive belt 26 is wound around the pulley 25. Here, the pressure receiving area of the primary cylinder 21 is set larger, and the ratio of the winding diameter of the drive belt 26 with respect to the primary pulley 22 and the secondary pulley 25 is changed by the primary pressure to perform stepless transmission.

In the differential device 6, an output shaft 28 is connected to the secondary shaft 23 via a pair of reduction gears 27, and a drive gear 29 of the output shaft 28 meshes with the final gear 30. The differential gear 31 of the final gear 30 is connected to the axles 32, 3
It is connected to the left and right wheels 33, 33 via 2.

On the other hand, in order to obtain a high hydraulic pressure source for controlling the continuously variable transmission, the continuously variable transmission 5 is provided with a main oil pump 34, which is directly connected to the crankshaft 2 via a pump drive shaft 35. Further, in order to obtain a low hydraulic pressure source for controlling the torque converter 12, the lock-up clutch 15 and the forward / reverse switching device 4, a sub oil pump 36 is provided in the torque converter device 3, and the sub oil pump 36 And directly connected to the converter cover 11.

In FIG. 2, the drive belt 26 includes a plurality of elements.
The primary pulley 22 and the secondary pulley 25 are wound around the primary pulley 22 and the secondary pulley 25 integrally and continuously. The belt speed detecting means faces the curved portion of the drive belt 26 wound around the primary pulley 22.
37 are arranged.

The belt speed detecting means 37 is an element of the drive belt 26.
An electromagnetic pickup 37a that detects the time when 26a passes,
A non-contact type displacement sensor 37b for detecting a distance L between the element 26a and the electromagnetic pickup 37a, and an electromagnetic pickup 37a and a displacement sensor 37b in accordance with the radial movement of the drive belt 26.
Servo motor as drive means for moving the motor in the radial direction
38 and has.

The electromagnetic pickup 37a and the displacement sensor 37b are mounted on a holder 37c, and a guide bar 37d and a rack 37e are mounted on the side of the holder 37c opposite to the drive belt 26 side.
The rack 37e is engaged with a pinion 38b provided on a motor shaft 38a of the DC servo motor 38, and an end of the rack 37e is fixed to a housing of a continuously variable transmission (not shown).
The guide bar 37d is also supported by the stay 39
Supported by

 In FIG. 3, the hydraulic control system will be described.

First, the hydraulic control system of the continuously variable transmission 5 will be described.
High pressure main oil pump 34 communicating with oil pan 40
The line pressure oil passage 41 communicates with the line pressure control valve 42 to generate a high line pressure, and this line pressure is always supplied to the secondary cylinder 24 via the oil passage 43. The line pressure is further led to a shift speed control valve 45 via an oil passage 44,
46 supplies and discharges oil to and from the primary cylinder 21 to generate primary pressure. An operating pressure oil passage 47 from a sub oil pump 36 described later communicates with a reducing valve 48 to constantly generate a constant oil pressure. The reducing oil passages 49 and 50 have a solenoid 51a of a line pressure control valve 42 having a solenoid 51a. The valve 51 communicates with a solenoid valve 52 having a solenoid 52a of a shift speed control valve 45.

The solenoid valve 51 is turned on / off by a duty signal from the control unit 80 to generate a pulse-like control pressure. The control pressure is smoothed by an accumulator 53, and the line pressure control valve 42
Act on. Then, the line pressure PL is controlled according to the gear ratio i, the engine torque Te, the torque converter torque amplification factor, and the like.

Similarly, the solenoid valve 52 generates a pulse-like control pressure based on the duty signal, and operates the shift speed control valve 45 to two positions of oil supply and oil discharge. Then, the operation state of the two positions is changed by the duty ratio to control the flow rate of oil supply / discharge to the primary cylinder 21, and the speed change control is performed by changing the speed ratio i and the actual speed ratio change speed di / dt.

Next, regarding a hydraulic control system such as a torque converter, the oil passage 60 from the sub oil pump 36 communicates with the regulator valve 61 to generate a predetermined low operating pressure. The working pressure oil passage 62 communicates with a lock-up control valve 63.
The oil chamber 65 releases the lock-up clutch 15
Connect to 66. On the other hand, the above-described oil path 68 of the reducing pressure communicates with the solenoid valve 67 having the solenoid 67a of the lock-up control valve 63. And control unit 80
If there is no lock-up signal from the torque converter 12 via the release chamber 66 through the oil passages 62 and 65,
When the lock-up signal is output, the operating pressure acts on the lock-up clutch 15 via the oil passages 62 and 64 to lock up.

The working pressure oil passage 69 branched from the oil passage 62 is connected to the forward clutch 17 via the select valve 70 and the oil passages 71 and 72.
It communicates with the reverse brake 18. Select valve 70 includes parking (P), reverse (R), neutral (N),
It switches according to each range of drive (D).
In the range, forward clutch 17 by oil passages 69 and 71
To the reverse brake 18 in the oil passages 69 and 72 in the R range, and to the forward clutch 17 in the P and N ranges.
And the reverse brake 18 is drained.

 The electronic control system will be described with reference to FIG.

As input means to a control unit 80 constituted by a microcomputer, an engine speed sensor 81, a primary pulley speed sensor 82, a secondary pulley speed sensor 83, a throttle opening sensor 84, a shift position sensor
85, an electromagnetic pickup 37a, and a displacement sensor 37b.

Therefore, regarding the shift speed control system, the primary pulley rotation speed Np and the secondary pulley rotation speed Ns of the primary pulley rotation speed sensor 82 and the secondary pulley rotation speed sensor 83 are input to the actual speed ratio calculation means 86 by the control unit 80. The actual speed ratio i is calculated from the actual speed ratio i = Np / Ns.
The actual speed ratio i and the throttle opening θ of the throttle opening sensor 84 are input to the target primary pulley rotation speed search means 87, and i-θ based on the speed change pattern for each range of R, D and sporty drive (Ds). The target primary pulley rotation speed NPD is searched by using the table of FIG. The target primary pulley rotation speed NPD and the secondary pulley rotation speed Ns are input to a target speed ratio calculating means 88, and the target speed ratio is is calculated by is = NPD / Ns.

The target gear ratio is input to the target gear ratio change speed calculating means 89, and the target gear ratio change speed dis / dt is calculated based on the change amount of the target gear ratio is for a certain period of time. The actual gear ratio i, the target gear ratio is, and the target gear ratio change speed dis / dt are calculated by the gear speed calculating means 90.
And the shift speed Δis is calculated as follows.

Δis = K ₁ · (is−i) + K ₂ · (dis / dt) In the above equation, K ₁ and K ₂ are constants, is−i is the control amount of the target and actual speed ratio deviation, and dis / dt is the control. This is a delay correction factor of the system.

The shift speed Δis and the actual speed ratio i are input to the duty ratio search means 91. Here, the duty ratio D ₂ of the manipulated variable is D ₂
= F (Δis, i), the duty ratio D ₂ becomes Δis−i in the upshift and the downshift.
Is searched using the table. The value of the duty ratio D ₂ of the operation amount is further corrected before and after the shift start.

Describing the lock-up control system, there is provided a speed ratio calculating means 92 to which the engine speed sensor 81, the engine speed Ne of the primary pulley speed sensor 82, and the primary pulley speed Np are inputted, and the input / output side of the torque converter. The speed ratio e is calculated by e = Np / Ne. The speed ratio e and the engine speed Ne are input to the torque converter state determining means 93. Here, to determine the converter region and the coupling region of the torque converter 12, not only the set speed ratio es but also the condition that the rotational speed difference ΔN = (Ne−Np) is small, so that the shock is reduced. As shown in FIG. 5 (a), the set speed ratio es is set by an increasing function of the engine speed Ne, and when e ≧ es with respect to the set speed ratio es, it is determined that the coupling region is present.

The target speed ratio is and the target speed ratio change speed dis / dt are input to the speed change start determining means 94. When the target speed ratio is is ≧ 2.5 with respect to the maximum speed ratio 2.5 on the mechanism of the continuously variable transmission 5, the speed change is performed. Before the start, if the target speed ratio is is <2.5, it is determined after the start of the shift. Here, in the target gear ratio calculating means 88 of the electronic control system,
The target gear ratio is is calculated even in a region where the target gear ratio is is> 2.5, and the dashed lines is ₁ and is shown in FIG.
It changes like ₂ ... When the predetermined delay time Δt is set in a state before the start of the shift, the shift start needs to be instructed with a larger value of the target speed ratio is as the change in the target speed ratio is, that is, the target speed ratio change speed dis / dt is larger. There is
Based on this, the map of FIG. 5 (c) is set. Therefore, when the target speed ratio change speed dis / dt is the value A in the map of FIG. 5C, the shift start is determined when the target speed ratio is reaches the value B.

The signals of the torque converter state, shift start, shift position, and secondary pulley rotation speed Ns are input to the lock-up determining means 95, and the speed ratio e and the set speed ratio es satisfy e ≧
When the coupling judgment of es, the shift start judgment, the range of D or Ds, the secondary pulley rotational speed Ns and the set value Nso of the secondary pulley rotational speed satisfy all the conditions of Ns ≧ Nso, the lock-up clutch 15 Determine lockup on. The lock-up signal is transmitted to the driving means 96
Is output to the solenoid 67a for lock-up control via.

In terms of the line pressure control system, the throttle opening θ
Torque calculation means to input the engine speed and Ne
97, the correlation between the engine speed Ne, the throttle opening θ, and the engine torque Te shown in FIG. 6A is stored, and the engine torque Te according to the operating state of the engine is obtained. Further, in response to a change in the input torque to the continuously variable transmission due to the torque amplifying action of the torque converter 12, there is provided a torque ratio search means 98 for inputting the speed ratio e,
Here, as shown in FIG. 5 (d), when the speed ratio e is, for example, 0.8 or less, the relationship between the speed ratio e and the torque ratio r is stored with the characteristic that the torque ratio r increases in inverse proportion to this speed ratio. In advance, the torque ratio r retrieved based on the input speed ratio e is input to the input torque calculation means 99, where the engine torque
The input torque Tc transmitted in the continuously variable transmission 5 is calculated from the product of Te and the torque ratio r.

On the other hand, the actual speed ratio i is input to the required line pressure setting means 100, and the required line pressure PLu is overdriven (OD) with respect to the actual speed ratio i input as shown in FIG.
The characteristic which becomes smaller as going to the side is stored, and the necessary line pressure PLu is searched, and the target line pressure setting means is set.
Enter 101.

In the target line pressure setting means 101, the target line pressure is calculated based on the product of the required line pressure PLu and the input torque Tc.
cL is set and stored, and the lower limit value TcL is compared with the input torque Tc to calculate the target line pressure PLd by the following equation.

If Tc ≧ TcL: PLd = PLu × k · Tc If Tc <TcL: PLd = PLu × k · TcL where k = constant In this way, for example, input torque during deceleration, etc.
Even if Tc decreases, a lower limit value at the time of calculation is set, and input to the duty ratio setting means 103 so that the output target line pressure PLd does not fall below a predetermined value.

On the other hand, in the valve characteristic correcting means 102 for correcting the characteristic of the line pressure control valve 42, as shown in FIG. 6 (c), the line pressure is determined by a spring load by a feedback sensor (not shown) and a duty pressure generated by a duty solenoid. Therefore, it is considered that the duty ratio of the duty solenoid and the actual speed ratio i are the parameters that determine the line pressure. However, in actuality, the discharge of the main oil pump 34 that is substantially proportional to the engine speed Ne is considered. Since the line pressure also changes depending on the amount, the line pressure is determined by three parameters of the duty ratio D ₃ , the actual speed ratio i, and the engine speed Ne. Therefore, when the duty ratio D ₃ = 0%, that is, when the duty pressure = reducing pressure, the correlation between the actual speed ratio i, the engine speed Ne, and the line pressure maximum value PLm is set. Then, the line pressure maximum value PLm is calculated from the engine speed Ne and input to the duty ratio setting means 103.

In the duty ratio setting means 103, the valve characteristic correction means 1
02, although define the duty ratio D ₃ based on the line pressure maximum value was calculated by the target line pressure setting means 101 PLm and the target line pressure PLd, firstly Figure 6 duty ratio D ₃ as shown in (d) And the relationship between PLm and PLd are set in advance, and P
Calculating the duty ratio D ₃ corresponding to Lm-PLd, drive means
The signal is output via a line 104 to a solenoid 51a for line pressure control.

Next, correction of the shift control system by the lockup control and the line pressure control will be described.

Furthermore, since the shift speed changes depending on the change speed of the actual gear ratio and when shifting is started from a stationary state,
An actual gear speed calculating means 110 for inputting the actual gear ratio i;
The actual speed ratio change speed di / dt is calculated. Then, the actual speed ratio change speed di / dt is input to the duty ratio search means 91,
Using the correction term K · (di / dt) based on the actual speed ratio change speed di / dt, Δis = K · (dt / dt) · [K ₁ · (is−i) + K ₂ · (dis / dt)] performing correction, match the duty ratio D ₂ to the actual shift control state.

The output side of the duty ratio search means 91 has a correction means 111 corresponding to a change in line pressure, and has an input torque calculation means 99.
Input torque Tc is input. That is, the duty ratio D ₁ In is corrected, is output as D _1.

The output side of the correcting means 111 has a shift start instructing means 112, and signals of the shift start determining means 94 and the torque converter state determining means 93 are input. If the coupling condition is not satisfied, the output duty ratio D _O is set to D _O = 0. Further, when the shift start conditions are satisfied, the target speed ratio changing speed dis / dt In this case, [Delta] D and the increase correction according to the target gear ratio IS, the output duty ratio D _O coupling conditions are satisfied D _O
= D ₁ + ΔD, which is input to the solenoid 52a for speed change control via the driving means 113.

Next, the correction of the line pressure control system due to the slip of the drive belt 26 will be described.

Since the drive belt 26 cannot avoid slip due to its structure, and the line pressure does not follow up when the engine 1 is accelerated or decelerated, a belt slip occurs. As a result, an appropriate target speed ratio is cannot be obtained. The target line pressure PLds is calculated and corrected by the following equation using the correction coefficient C determined by the slip amount.

PLds = C · PLd Thus by setting the duty ratio D _3, to prevent belt slippage.

First, the engine speed Ne, the throttle opening θ, and the target gear ratio is input, and the target belt winding pitch diameter search means 115 for searching the target belt winding pitch diameter Dp of the drive belt 26 from a preset map. The searched target belt winding pitch diameter Dp and the primary pulley rotation speed Np are input to the target belt speed calculating means 116, and the target belt speed V
s is calculated from a preset map.

On the other hand, there is provided an actual belt speed calculating means 117 to which the output of the electromagnetic pickup 37a is inputted. Here, as shown in FIG. Calculated and target belt speed Vs
The actual belt speed V and the belt slip change amount calculating means 11
8 and the amount of change in belt slip SL = d (Vs-V)
/ dt is calculated.

The calculated belt slip change amount SL is input to a line pressure correction coefficient setting means 119, and a line pressure correction coefficient C is set from a preset map. The correction coefficient C is set to 1.0 when there is no belt slip, and is set as an increasing function with respect to the amount of change in belt slip. Then, the target line pressure PLd set by the required line pressure PLu and the input torque Tc by the target line pressure setting means 101 is corrected by the line pressure correction coefficient C.

Also, the distance L between the electromagnetic pickup 37a and the element 26a of the drive belt 26 when the signal of the displacement sensor 37b is input,
Distance calculating means 12 calculated from the map shown in FIG.
0, and the calculated distance L is input to the determination means 121,
From the map of FIG. 7B, the distance between the drive belt 26 and the electromagnetic pickup 37a (displacement sensor 37b) is determined with respect to the lower limit value L _LOW and the upper limit value L _HIGH , and the determined signal is a servo motor driving means. It is output to the CD servo motor 38 via 122.

Next, the operation of the control device thus configured will be described.

First, when the engine 1 is started in the N or P range,
Although the torque converter device 3 is driven by the crankshaft 2, the torque converter device 3 is cut off by the forward / reverse switching device 4 and no engine power is input to the continuously variable converter 5. On the other hand, at this time, the main oil pump is driven by the pump drive shaft 35 and the converter cover 11.
The sub-oil pump 36 is driven, and a predetermined hydraulic pressure is generated by a line pressure control valve 42, a regulator valve 61, and a reducing valve 48 of the hydraulic control system. Here, the line pressure is supplied only to the secondary cylinder 24, and the drive belt 26 is shifted to the secondary pulley 25 side, so that the low speed stage having the maximum speed ratio is achieved. Further, since the solenoid valve 67 switches the lock-up control valve 63 to the release side of the lock-up clutch 15 by the lock-up / off signal of the lock-up determination means 95, the operating pressure is controlled by the torque converter 12 via the release chamber 66. To the lock-up clutch 15
Is turned off, and the torque converter 12 is activated.

Therefore, when shifting to the D range, the forward clutch 17 is supplied with oil by the select valve 70, so that the planetary gear 16 is integrated and the turbine shaft 13 and the primary shaft 20 are directly connected to each other, and the forward position is established. For this reason, the engine power is transmitted through the torque converter 12 to the primary shaft of the continuously variable transmission 5.
Input 20 to primary pulley 22, secondary pulley 25
The power of the lowest speed stage is output to the secondary shaft 23 by the drive belt 26 and transmitted to the wheels 33 via the differential device 6 to start.

This start is performed at a speed lower than the line l _L of the maximum speed ratio in the speed change pattern of FIG. 9, and the actual speed ratio is the maximum speed ratio.
It is held at 2.5. However, in the shift control system,
As the secondary pulley rotation speed Ns increases in step S103 of FIG. 8 (a), the actual speed ratio i is calculated by the increase of the secondary pulley speed Ns and the primary pulley rotation speed Np, and in step S104 the actual speed ratio i, the throttle opening θ, the shift position And the target primary pulley rotation speed N
PD is the target primary pulley rotation speed N in step S105.
Target speed ratio is is determined by PD and secondary pulley rotation speed Ns.
In step S106, the target speed ratio change speed dis / dt is calculated.

In step S107, the target speed ratio is, the actual speed ratio i, and the target speed ratio change speed dis / dt are used to determine the speed change Δis
Of the actual gear ratio change speed di / d in step S108.
calculating a t, the shift speed Δis corrected by the actual speed ratio changing speed di / dt in a step S109, it sets the operation amount of the duty ratio D ₂ corresponding to the control amount at step S110.

Next, in step S111, the engine torque Te is set from the map shown in FIG. 6A based on the engine speed Ne and the throttle opening θ, and in step S112, FIG.
The torque ratio r is searched from the map shown in FIG. Then, in step S113, the input torque Tc transmitted to the continuously variable transmission 5 is calculated from the product of the engine torque Te and the torque ratio r.

Further in step S114, obtaining the duty ratio D ₁ corrected in response to the line pressure.

In step S115, based on the target speed ratio is and the target speed ratio change speed dis / dt, it is determined that the speed change is to be started at a point in time when the target speed ratio is is large and the target speed ratio is large in the rapid speed change state. Is secured. Therefore, when the target speed ratio is and the target speed ratio change speed dis / dt satisfy the characteristics shown in FIG. 5C, it is determined that the shift is to be started, and when it is determined that the shift is to be started, the process proceeds to step S116.

In step S116, the speed ratio e is compared with the set speed ratio es. If e ≧ es, the coupling region is determined, and the process proceeds to step S117. Then, in step S117, lock-up of lock-up clutch 15 is determined.

Therefore, in step S118, a lock-up signal is output to the solenoid 67 for lock-up control, and the solenoid valve 67
By switching the lock-up control valve 63 to the torque converter side, the operating pressure is confined in the torque converter 12 and acts on the lock-up clutch 15, and the lock-up clutch 15 is directly connected to the converter cover 11 to lock up. Thus engine power will be efficiently transmitted by the lock-up clutch 15, the transmission throughout the lock-up region between the ninth diagram of a transmission start time of the gear ratio maximum line l _L and the minimum line l _H Become.

In step S119, the output duty ratio D _O is set by increasing and correcting the duty ratio D ₁ by ΔD.
At, and outputs a signal of the duty ratio D _O to shift speed control of the solenoid 52a. Thereby, the shift speed control valve 45 is operated by the solenoid valve 52 to generate a primary pressure,
Actually, starting at the same time shift the above lock-up from P a predetermined point of the line l _L of FIG. 9, to upshift.

In this lockup state, the speed ratio e is e = 1, and the torque amplification rate α is also 1. Therefore, thereafter, the line pressure is controlled only by the factors of the actual speed ratio i and the engine torque Te.

On the other hand, if the converter region of e <es is determined in step S116, the process returns to step S115 to prevent the start of gear shifting, waits for the determination of the coupling region, and performs lock-up and gear shifting simultaneously. Become.

In step S121, a lower limit value TcL of the input torque Tc is set, and a target line pressure PLd for the input torque Tc is calculated.

Therefore, when starting with the maximum gear ratio, the torque converter
12 has a torque amplifying effect due to a small speed ratio e. This amplification is based on the torque ratio r retrieved from the relationship between the speed ratio e and the torque ratio r in FIG. 5 (d) set in step S112, and based on the lower limit TcL in step S121.
Is obtained by the target line pressure PLd using the input torque Tc in which is set as a parameter as one of the parameters.
Even when the value of the actual gear ratio i is low on the OD side, the lower limit of the target line pressure PLd is restricted.

In step S122, the actual belt speed V of the drive belt 26 is calculated based on the output signal from the electromagnetic pickup 37a. In step S123, the target belt speed V is calculated from the map based on the engine speed Ne, the throttle opening θ, and the target gear ratio is. The belt winding pitch diameter Dp is set, and in step S124, the target belt speed Vs is calculated from the target belt winding pitch diameter Dp and the primary pulley rotation speed Np.

In step S125, a belt slip change amount SL between the target belt speed Vs and the actual belt speed V is calculated. In step S126, a line pressure correction coefficient C is set from a map based on the belt slip change amount SL. Line pressure PLd
Is corrected to PLds based on the correction coefficient C in step S127. In step S128, a line pressure maximum value PLm is calculated from a correlation map of the preset engine speed Ne, actual speed ratio i, and line pressure maximum value PLm, and in step S129, as shown in FIG. and set the duty ratio D ₃ from the map by the PLm-PLd and the duty ratio D ₃ showing, step S1
At 30, and outputs a signal of the duty ratio D ₃ to the line pressure control solenoid 51a.

Therefore, when the drive belt 26 slips, the target line pressure PLd is corrected to PLds by the belt slip change amount SL, so that the pressing force on the secondary pulley 25 is reliably obtained, and the distance between the drive belt 26 and the secondary pulley 25 is increased. Torque transmission can be performed without the occurrence of slippage.

Next, the control procedure of the DC servomotor 38 will be described based on the flowchart of FIG.

This is an interrupt routine executed at regular intervals or at regular intervals. First, in step S201, the displacement sensor 37b
(Electromagnetic pickup 37a) and element 2 of drive belt 26
The distance L from the sensor 6a is calculated based on the output signal of the displacement sensor 37b. In step S202, a predetermined lower limit L _{LOW is set.}
When L> L _LOW , the process proceeds to step S203. In step S203, the upper limit value L _HIGH is compared. When L <L _HIGH , the process proceeds to step S204.
38 stops.

When L ≧ L _{HIGH in} step S203, the process proceeds to step S205. In step S205, the DC servo motor 38 is driven in reverse to move the electromagnetic pickup 37a (displacement sensor 37b) in the direction approaching the drive belt 26. .

If L ≦ L _LOW in step S202, step S206
In step S206, the DC servo motor 38 is driven to rotate forward to move the electromagnetic pickup 37a (displacement sensor 37b) in a direction away from the drive belt 26.

Therefore, the actual belt speed V of the drive belt 26 is reliably calculated even during the transition of the continuously variable transmission 5 during the shift.

In the present embodiment, the belt speed detecting means 37 is provided on the primary pulley 22 side, but may be provided on the secondary pulley 25 side.

As mentioned above, although one Example of this invention was described, it is not limited to this.

〔The invention's effect〕

As described above, according to the present invention, the belt speed detecting means for detecting the belt speed of the drive belt is provided to face the drive belt, and the line acting on the hydraulic cylinder of each pulley when the slip of the drive belt occurs. In order to correct the target line pressure of the drive belt, the control unit includes: a target belt speed calculating unit that calculates a target belt speed of the drive belt; an actual belt speed calculating unit that calculates an actual belt speed; A belt slip change amount calculating means for calculating a slip change amount of the drive belt from the belt speed, so that the line pressure is corrected based on the slip change amount of the drive belt based on the target belt speed of the drive belt and the actual belt speed. As a result, the belt pressing force of the secondary pulley is obtained, preventing slippage between the drive belt and the secondary pulley. can do.

Further, since the line pressure is corrected based on the amount of change in belt slip obtained from the belt speed of the drive belt, it is possible to prevent slip which cannot be avoided from the structure of the drive belt and slip of the drive belt due to load fluctuation. .

The belt speed detecting means includes an electromagnetic pickup for detecting a belt speed of the drive belt, a displacement sensor for detecting a distance between the element of the drive belt and the electromagnetic pickup, and a distance between the electromagnetic pickup and the element of the drive belt. Since the driving means for maintaining the driving speed within the range is provided, it is possible to reliably calculate the actual belt speed of the driving belt even during shifting.

[Brief description of the drawings]

FIG. 1 is a skeleton diagram showing an embodiment of a belt-type continuously variable transmission with a torque converter of the present invention, FIG. 2 is a view taken in the direction of arrows II-II in FIG. 1, FIG. 3 is a circuit diagram of a hydraulic control system, 4 is a block diagram showing an embodiment of the control device, FIGS. 5 and 6 are characteristic diagrams, FIG. 7 (a) is a diagram showing the relationship between the output of the electromagnetic pickup and the belt speed, and FIG. 7 (b) ) Is an output characteristic diagram of the displacement sensor, FIGS. 8 (a) and (b) are flowcharts, and FIG. 9 is a diagram showing lock-up ON / OFF and shifting start. 21,24 …… Hydraulic cylinder, 22 …… Primary pulley, 25
...... Secondary pulley, 26 Drive belt, 26a Element, 26b Metal band, 37 Belt speed detecting means, 37a Electromagnetic pickup, 37b Displacement sensor, 38
... DC servo motor (drive means), 80 ... control unit, 116 ... target belt speed calculation means, 117 ... actual belt speed calculation means, 118 ... belt slip change amount calculation means.

Claims (2)

(57) [Claims] 1. A drive belt composed of a metal band and a plurality of elements is wound around a primary pulley and a secondary pulley with variable pulley spacing, and a line pressure acting on a hydraulic cylinder of each pulley is output from a control unit. In the continuously variable transmission that changes the winding diameter of the drive belt by changing the winding diameter of the drive belt, a belt speed detection unit that detects a belt speed of the drive belt is provided to face the drive belt. The control unit calculates a target belt speed of the drive belt so as to correct a target line pressure of a line pressure acting on the hydraulic cylinder of each of the pulleys when the drive belt slips. Means, an actual belt speed calculating means for calculating an actual belt speed, and Control device for a continuously variable transmission, characterized in that it has a belt slip variation calculating means for calculating a slip amount of change in the belt. A belt speed detecting means for detecting a belt speed of the drive belt; a displacement sensor for detecting a distance between an element of the drive belt and the electromagnetic pickup; The control device for a continuously variable transmission according to claim 1, further comprising a driving unit for keeping a distance from the element within a predetermined range.