JP2876324B2 - Control device for continuously variable transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a control device for electronically performing speed change control and line pressure control in a belt type continuously variable transmission for a vehicle,
More specifically, the present invention relates to a method of performing speed change control with a change speed of a pulley position as a control object.

[Conventional technology]

Generally, in this type of continuously variable transmission, a line pressure capable of transmitting torque is applied to a secondary cylinder, a predetermined oil amount is supplied to a primary cylinder by a shift control valve, a primary pressure is generated, and the speed ratio is variably controlled. It has a configuration. Therefore, in the electronic control of the shift, the shift control valve is operated by an electric signal to control the flow rate, thereby making the oil amount of the primary cylinder variable. In this case, attention is paid to the point that the shift by the primary cylinder is controlled by the flow rate of the shift control valve, and what parameter is optimally used for the control target is devised.

Therefore, conventionally, there is a prior art in Japanese Patent Application Laid-Open No. 62-221930, for example, regarding the computerization of the shift control of the continuously variable transmission. Here, the primary cylinder oil amount is determined by a function of the gear ratio, and the flow rate obtained by time-differentiating the oil amount is determined by a function of the shift speed and the gear ratio. Further, the flow rate controlled by the shift control valve is determined by the duty ratio and the speed ratio of the electric operation amount, and the operation amount is determined by the shift speed and the speed ratio in a relationship between the duty ratio and the above-described primary cylinder side flow rate. . On the other hand, it is shown that the control amount is set as the shift speed and the shift speed is calculated based on a deviation between the target speed ratio and the actual speed ratio.

[Problems to be solved by the invention]

By the way, in the above-mentioned prior art, the flow rate of the primary cylinder is determined by a function of the shift speed and the speed ratio, but in the actual deployment type, if the term of the speed ratio changes, the rate of change in the flow rate is Become. Therefore, when the speed change is small and the speed changes little by little, the speed ratio term can be neglected, but if the change amount is large, the effect becomes large. Need to be corrected or corrected.

Here, the speed ratio of the continuously variable transmission can be determined by various factors such as the oil amount of the primary cylinder, the primary pressure, the position of the pulley, and the like. When the speed ratio is constant, the speed ratio is simply determined by the pressure ratio between the primary pressure and the secondary pressure. Can be controlled. For this reason,
It is desired to select a control target without being particular about the "shift" element and to set the operation amount accurately and easily.

The present invention has been made in view of such a point, and an object of the present invention is to easily and reliably perform flow control by a shift control valve using a pulley position and its change speed in electronic control of shift. It is an object of the present invention to provide a control device for a continuously variable transmission.

[Means for solving the problem]

In order to achieve the above object, a control device according to the present invention provides a shift control system that performs a shift operation by controlling a shift control valve at least by a flow rate with an electric operation amount, and at least a deviation between a target pulley position and an actual pulley position; And means for controlling the pulley position change speed based on the change speed of the target pulley position.

[Action]

Based on the above configuration, the pulley position change speed in a one-to-one relationship with the flow rate controlled by the shift control valve is controlled as a control target. As the target pulley position is set according to each driving and running condition, the pulley position change speed is calculated from the deviation from the actual pulley position and the target pulley position change speed of the phase advance element. The operation amount is set without correcting the position.
This operation amount is output to the shift control valve to operate, and by controlling the flow rate of the primary cylinder, the shift control is performed so that the actual pulley position always quickly follows the target pulley position and converges.

〔Example〕

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

Referring to FIG. 2, an outline of a transmission system including a continuously variable transmission to which the present invention is applied will be described. An engine 1 is connected to a primary shaft 5 of a continuously variable transmission 4 via a clutch 2 and a forward / reverse switching device 3. I do. In the continuously variable transmission 4, the secondary shaft 6 is arranged in parallel with the primary shaft 5, and the primary shaft 5
Is provided with a primary pulley 7, a secondary shaft 6 is provided with a secondary pulley 8, and the primary pulley 7 and the secondary pulley 8 are equipped with a primary cylinder 9 and a secondary cylinder 10 on the movable side, and a drive belt 11 is wound therearound. Have been. Here, the pressure receiving area of the primary cylinder 9 is set to be larger, and the ratio of the winding diameter of the drive belt 11 to the primary pulley 7 and the secondary pulley 8 is changed by the primary pressure so that the stepless transmission is performed.

The secondary shaft 6 is connected to an output shaft 13 via a set of reduction gears 12, and the output shaft 13 is a final gear.
The transmission is configured to be transmitted to the drive wheels 16 via the differential gear 15.

Next, the hydraulic control system of the continuously variable transmission 4 will be described. An oil pump 20 driven by the engine 1 is provided, and the line pressure oil passage 21 on the discharge side of the oil pump 20 is connected to the secondary cylinder 10 and the line pressure control valve. 22, communicates with the shift control valve 23, and communicates with the primary cylinder 9 via the oil passage 24 from the shift control valve 23. The line pressure oil passage 21 has an orifice
The line pressure communicates with one of the solenoid valves 27 and 28 and the shift control valve 23 via 32, and the line pressure is the original pressure of each of the solenoid valves 27 and 28. Each solenoid valve 27, 28 is connected to the control unit 40
For example, the pressure signal is turned on to discharge the pressure, and turned off to output a hydraulic pressure equal to the line pressure in response to the duty signal from the controller, thereby generating such a pulse-like control pressure. The control pressure from the solenoid valve 27 is applied to the line pressure control valve 22 by the oil passage 25.
Act on. On the other hand, the pulse-like control pressure from the solenoid valve 28 acts on the other of the transmission control valve 23 through the oil passage 26. Reference numeral 29 in the figure denotes a sensor shoe which is engaged with the primary pulley 7 and mechanically controls the line pressure according to the gear ratio.
30 is an oil pan.

The line pressure control valve 22 controls the line pressure PL based on the gear ratio i and the engine torque T by the control pressure from the solenoid valve 27.
Control.

The shift control valve 23 is connected to the oil supply position for connecting the oil passages 21 and 24 and the oil discharge position for draining the oil passage 24 according to the relationship between the line pressure of the original pressure and the pulse control pressure from the solenoid valve 28. Operate.

The duty ratio changes the operating state of the two positions to control the flow rate Q of oil supply or drainage to the primary cylinder 9 to control gear shifting.

That is, the required oil amount V of the primary cylinder 9 is mechanically determined in relation to the pulley position e, and V = f (e). The flow rate Q is obtained by differentiating the oil amount V with time. From this, Q = dv / dt = df (e) / dt, and the flow rate Q and the pulley position change speed de / dt completely correspond one-to-one.

Also, primary cylinder internal pressure Pp, line pressure PL, flow coefficient c, gravity acceleration g, oil specific weight γ, valve oil supply port opening area
Assuming Si and the oil discharge port opening area SD, the oil supply flow rate Qi and the oil discharge flow rate QD are as follows: QD = c · SD [(2g · Pp) / γ] ^1/2 = a · SD (Pp) ^1/2 Qi = a · Si (PL−Pp) ^1/2 where a = c (2g / γ) ^1/2

Therefore, the duty ratio (on / off ratio) of the operation amount is set to D
Then, the average flow rate Q in one cycle (refueling is assumed to be positive)
Q = a ｛D · Si (PL−Pp) ^1/2 − (1−D) × SD (P
p) ^1/2 、, where a, Si, and SD are constants, the following equation is obtained.

Q = f (D, PL, Pp) where the line pressure PL is the pulley position e, the engine torque T
And the primary cylinder pressure Pp is
It is determined by the pulley position e and the line pressure PL. Now, assuming that the engine torque T is constant, Q = f (D, e), and the following equation holds.

de / dt = f (D, e) Therefore, when the equation is expanded, D = f (de / dt, e). From the above, the duty ratio D is the relationship between the pulley position change speed de / dt and the pulley position e. It will be decided by.

On the other hand, since the pulley position changing speed de / dt is based on the deviation between the steady target pulley position es and the actual pulley position e, the following equation is established.

de / dt = K (es−e) (K is a constant) From this, at each pulley position e, if the pulley position change speed de / dt is determined from the above equation, the duty ratio D is obtained based on it. If the shift control valve 23 is operated at the duty ratio D, shift control can be performed over the entire shift range of the low-speed gear and the high-speed gear.

By the way, the above-described shift control is a basic feedback control system that does not include any disturbance element. Therefore, when the continuously variable transmission is actually controlled by the operation amount of the duty ratio D, the control system of the continuously variable transmission is required. Causes a first-order delay and poor convergence. Therefore, the target pulley position change speed des / dt is calculated as a phase advance element of the first-order lag control system, and this is taken into account in advance. From this, the pulley position change speed de / d
t can be determined as follows:

de / dt = K ₁ (es−e) + K ₂ · des / dt (K ₁ and K ₂ are coefficients) Thus, by taking into account the target pulley position change speed des / dt, a phase lead element is added to converge Is improved. Here, since the target pulley position change speed des / dt is a change state of the target pulley position in a certain traveling state of the vehicle, the target pulley position change amount Δes is obtained at regular time intervals Δt, and is calculated by Δes / Δt.

Coefficient K ₁ is directly related to the pulley position change rate,
It can be made to be a predetermined fixed value or variable in relation to a change in the accelerator opening in accordance with the driver's intention to accelerate. Factor K ₂ is relates to the delay component, for example a continuously variable transmission,
The value can be fixed or variable in consideration of the oil viscosity of the hydraulic control system.

Thus, the electronic control system shown in FIG. 1 is configured based on the above principle, and will be described below.

First, the shift control system will be described. It has a primary pulley 7, a secondary pulley 8, a primary pulley rotation speed sensor 41 of the engine 1, a secondary pulley rotation speed sensor 42, an engine rotation speed sensor 43, and a throttle opening sensor 44. Then, in the control unit 40, the rotation signals Np and Ns from the primary pulley rotation speed sensor 41 and the secondary pulley rotation speed sensor 42 are input to an actual pulley position calculation unit 45,
The actual pulley position e of the primary pulley 7 corresponding to the actual speed ratio i is obtained by e = Np / Ns. The signals of the actual pulley position e and the throttle opening θ of the throttle opening sensor 44 are input to the target primary pulley rotation speed search unit 46, and the target primary pulley rotation speed NPD is determined in relation to e−θ.

Here, in the region A where the throttle opening is small, the primary pulley rotation speed Np has a constant characteristic with emphasis on smoothness of shifting. On the other hand, in the region B where the throttle opening is medium or large, the primary pulley rotation speed Np is increased in the shift-up direction in which the actual pulley position e decreases at the same throttle opening with emphasis on followability during transition. The target primary pulley rotation speed NPD is selected by searching such a map.

The target primary pulley rotation speed NPD of the target primary pulley rotation speed search unit 46 and the secondary pulley rotation speed sensor 42
Is input to the target pulley position calculator 47, where the target pulley position es is es = N PD
It is calculated by / Ns. The signal of the target pulley position es is input to the target pulley position change speed calculation unit 48, and the target pulley position change speed des / dt is calculated based on the change amount Δes of the target pulley position es every fixed time Δt. And the actual pulley position mentioned above
e, the target pulley position es, the target pulley position change speed des / dt, and the coefficients K ₁ and K ₂ of the coefficient setting unit 49 are input to the pulley position change speed calculation unit 50, and de / dt = K ₁ (es−e) The pulley position change speed de / dt is calculated from + K ₂ · dse / dt. The signals from the pulley position change speed calculation unit 50 and the actual pulley position calculation unit 45 are further input to the duty ratio search unit 51.

Here, as described above, a table of the duty ratio D based on the pulley position change speed de / dt and the actual pulley position e is set according to the relationship of D = f (de / dt, e). Search for the duty ratio D. In this table, at a predetermined duty ratio D ₀ to be the boundary pulley position change velocity de / In value negative upshift direction dt D = 100% side of each pulley position e, the pulley position change rate de / dt The value becomes closer to 100% as the negative value of becomes smaller. On the other hand, in the downshift direction where the value of the pulley position change speed de / dt is positive, the pulley position change speed de / dt is on the D = 0% side.
Is set to a value close to 0% as the positive value of becomes larger. Then, a signal of the duty ratio D from the duty ratio search unit 51 is input to the solenoid valve 28 via the drive unit 52.

Next, the line pressure control system will be described. The signal θ of the throttle opening sensor 44 and the signal Ne of the engine speed sensor 43 are input to the engine torque calculation unit 53, and θ−Ne
The engine torque T is obtained from the table of the torque characteristics of the above. On the other hand, based on the actual pulley position e from the pulley position conversion unit 45, the required line pressure PLu per unit torque is determined in the required line pressure setting unit 54, and this and the engine torque T of the engine torque calculation unit 53 are used as the target line pressure. The target line pressure PL is input to the calculation unit 55 to calculate PL = PLu · T.

The output PL of the target line pressure calculation unit 55 is input to the duty ratio search unit 56 to set a duty ratio D corresponding to the target line pressure PL. The signal of the duty ratio D is input to the solenoid valve 27 via the driving unit 57.

Next, the operation of the thus-configured control device for a continuously variable transmission will be described.

First, the power corresponding to the depression of the accelerator from the engine 1 is input to the primary pulley 7 of the continuously variable transmission 4 via the clutch 2 and the forward / reverse switching device 3, and the power is shifted by the drive belt 11 and the secondary pulley 8. Is output and transmitted to the drive wheels 16 to drive the vehicle.

During the running, the target line pressure is set to be larger as the engine torque T is larger at a low speed where the value of the actual pulley position e is larger, and a duty signal corresponding to this is input to the solenoid valve 27 to generate a control pressure. By operating the line pressure control valve 22 with this control pressure, the line pressure PL of the line pressure oil passage 21 is increased. The line pressure PL is controlled so as to decrease as the value of the pulley position e decreases and the engine torque T decreases as the engine torque T decreases. Thus, the line pressure PL always corresponds to the transmission torque of the drive belt 11. Apply pulley pressing force.

The line pressure PL is always supplied to the secondary cylinder 10, and the transmission control valve 23 controls the primary cylinder 9.
The shift control is performed by supplying / discharging the oil, and this will be described below.

First, the signals Np, Ns, and θ from the primary pulley rotation speed sensor 41, the secondary pulley rotation speed sensor 42, and the throttle opening sensor 44 are read, and the control unit 40 obtains the actual pulley position e. Further, the target primary pulley rotation speed NPD is once searched from a map based on the actual pulley position e and the throttle opening θ, and the target primary pulley rotation speed N
The target pulley position es and the target pulley position change speed dse / dt corresponding to the PD are calculated. Then, the deviation between the target pulley position es and the actual pulley position es, the target pulley position change speed des / dt, and the coefficients K ₁ and K ₂ are used to calculate the pulley position change speed de / dt. The duty ratio D is retrieved from the map of the actual pulley position e.

Here, since the flow rate Q and the pulley position change speed de / dt have a one-to-one correspondence, the duty ratio D of the operation amount is set only by the pulley position change speed de / dt. The duty signal is input to the solenoid valve 28 to generate a pulse-like control pressure. This control pressure and the line pressure of the original pressure act opposite to the shift control valve 23, and the two positions of the oil supply and the oil discharge are performed. Operate repeatedly.

Therefore, in the shift pattern shown in FIG.
Becomes the maximum e _max , and at a low speed with a mechanical maximum gear ratio i _L ,
When es ≧ e _max, the value of the pulley position change speed de / dt becomes positive, and the duty ratio D becomes a value smaller than, for example, 50%.
Therefore, in the transmission control valve 23, the operation time at the oil discharge position is prolonged due to the high control pressure, and the primary cylinder 9 is in the oil discharge state. Next, after the shift start point P
When the relationship of es <e _max is satisfied, the value of the pulley position change speed de / dt becomes negative, and the duty ratio D becomes a value greater than 50%. The operation time becomes longer, and the primary cylinder 9 is refueled. Therefore, the primary pressure gradually increases with the oil amount of the primary cylinder 9, and the belt 11 shifts so as to increase the winding diameter on the primary pulley 7 side, and is upshifted. When the pulley position e reaches a minimum speed ratio i _H fast stage on mechanism becomes minimum e _mln, maintaining a slight lubrication state values of the pulley position change rate de / dt is negative, the pulley position e is minimum _Held in the e _min .

On the other hand, es in the shift starting point since Q of minimum speed ratio i _H>
When the relationship of e _min is satisfied, the value of the pulley position change speed de / dt becomes positive and the duty ratio D becomes a value smaller than 50%, so that the primary cylinder 9 is gradually drained by the shift control valve 23. Therefore, belt 11 again moves down shift as winding diameter of the secondary pulley 8 side becomes large, pulley position e is returned to the maximum speed ratio i _L of the largest e _max.

Also, the target primary pulley rotation speed
For example, when the N PD rapidly increases and the value of the target pulley position es also rapidly increases, the value of the pulley position change speed de / dt becomes the target pulley position es.
The value suddenly becomes a large positive value in accordance with the deviation between the pulley position and the pulley position e. Then, the duty ratio D becomes the pulley position change speed de / d
The value is reduced to 0% according to the value of t, and the oil discharge flow rate is properly controlled by the shift control valve 23, and the pulley position e is set to the target pulley position es
, And the downshift rapidly occurs. Also, in the case of a sudden upshift, the duty ratio D corresponding to the value of the pulley position change speed de / dt is similarly determined.
Place in, thus it will be continuously variable across the maximum speed ratio i _L and the minimum speed ratio i _H.

Next, a description will be given of a state where the pulley position e follows the target pulley position es in FIG.

First, for example, when a kick-down operation is performed, the target pulley position es is immediately increased as shown by the solid line in the relationship between the target primary pulley rotation speed NPD and the secondary pulley rotation speed Ns, and the actual pulley position e is accordingly set. Also mainly K ₁ (es
Due to the deviation of -e), it increases following the target pulley position es as shown by the broken line, and downshifts. And pulley position e
Approaches the target pulley position es,
The value of target pulley position change velocity des / dt change in the decreasing direction by becomes negative, the pulley position e by section K ₂ · dse / dt, without overshoot come peaks in early It smoothly follows the target pulley position es and converges.

Although the embodiment of the present invention has been described above, the position of the pulley may be detected by a stroke sensor. Further, the target pulley position may be directly searched by a map of the throttle opening θ and the secondary pulley rotation speed Ns. The pulley position may detect the secondary pulley.

〔The invention's effect〕

As described above, according to the present invention, in the electronic control of the continuously variable transmission, the oil amount of the primary cylinder is determined as a function of the position of the pulley, and the flow rate corresponds to the pulley position changing speed on a one-to-one basis. Since the control method uses the position change speed as a control target, the operation amount can be easily and accurately set only by the value of the pulley position change speed or the like, which facilitates the control and improves the accuracy of the shift control.

Furthermore, by calculating the pulley position change speed from the deviation between the target pulley position and the actual pulley position, the speed can be controlled so as to follow the actual pulley position at any speed change, taking into account the change speed of the target pulley position. Improves the convergence.

Further, based on the position of the pulley, it is possible to easily check the shift state in combination with the signal of the stroke sensor, and to switch to pressure ratio control or the like at the maximum and minimum fixed pulley positions, thereby facilitating the control.

[Brief description of the drawings]

1 is a block diagram showing an embodiment of a control device for a continuously variable transmission according to the present invention. FIG. 2 is a diagram showing a drive system and a hydraulic control system of the continuously variable transmission to which the present invention is applied. FIG. 4 is a diagram showing a shift pattern, and FIG. 4 is a diagram showing a state in which a pulley position e follows a target pulley position es during kick down. 4 ... continuously variable transmission, 9 ... primary cylinder, 23 ...
Transmission control valve, 28 Solenoid valve, 40 Control unit, 45 Actual pulley position calculator, 47 Target pulley position calculator, 48 Target pulley position change speed calculator, 50
Pulley position change speed calculation unit, 51: Duty ratio search unit

Claims (2)

(57) [Claims] A shift control system for performing a shift operation by controlling at least a flow rate of an electrical control amount of a shift control valve, wherein at least a deviation between a target pulley position and an actual pulley position and a change speed of the target pulley position. A control device for a continuously variable transmission, comprising: means for controlling a pulley position change speed. 2. The control device for a continuously variable transmission according to claim 1, wherein the actual pulley position is calculated as the same as the gear ratio or detected by a stroke sensor.