JPH041230B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a continuously variable transmission that is used, for example, in a vehicle power transmission device and continuously changes its speed ratio.

[Conventional technology]

The present applicant previously filed Japanese Patent Application No. 57-67362 (Japanese Patent Laid-Open No. 58
−184347), the engine rotational speed −
A vehicle power transmission system has been disclosed that controls the operation of an engine along a minimum fuel consumption rate line defined on an engine output torquer coordinate system. In the vehicle power transmission device,
The engine rotation speed is changed by changing the CVT speed ratio.

[Problem to be solved by the invention]

It is impossible to change the CVT speed ratio e (=output side rotational speed Nout/input side rotational speed Nin) from 0 to infinity, and the speed ratio e is limited to a predetermined range due to the size, weight, etc. of the CVT body. It will be done. In vehicles, the gear ratio γ is set to ensure hill-climbing performance, etc.
(=1/e) is required to be 11 to 12, but in order to improve the fuel efficiency, it is desirable that the minimum gear ratio be as small as possible. Due to this fact, the period in which an actual vehicle is operated with the speed ratio e at the maximum value e max or minimum value e min within the predetermined range becomes long. FIG. 2 shows the change in speed ratio over time when a vehicle equipped with the vehicle power transmission device of the prior application was actually run on a predetermined test course. In particular, the period of operation in the e max state is becoming extremely long. In the CVT of the earlier application, when the target speed ratio e ^* of the engine becomes large or small, the CVT moves out of the feedback range and operates at the maximum or minimum speed ratio that is limited by the structure of the CVT body. At this time, the movable disk of the CVT is in contact with the stopper, causing an imbalance in the servo hydraulic pressure, and excessive force is applied to the belt, reducing transmission efficiency and reducing belt durability. An object of the present invention is to provide a control device for a continuously variable transmission that can be operated while avoiding deterioration in transmission efficiency and belt durability.

[Means to solve the problem]

In order to achieve this object, the continuously variable transmission control device of the present invention has the following features as shown in FIG.
means for detecting the amount of depression of the accelerator pedal, means for determining a target input side rotation speed based on the amount of depression of the accelerator pedal, means for detecting the input side rotation speed, means for detecting the output side rotation speed, and an input side rotation speed. means for calculating an actual speed ratio from the side rotational speed and the output side rotational speed, means for calculating the target speed ratio from the target input side rotational speed and the actual output side rotational speed, and setting in advance the maximum value of the speed ratio. means for comparing the target speed ratio and the maximum value; and when the target speed ratio is smaller than the maximum value, performing feedback control so that the input side rotation speed becomes the target input side rotation speed. means for controlling the speed ratio by, when the target speed ratio is larger than the maximum value of the speed ratio, the target speed ratio is once reset to the maximum value of the speed ratio, and then the speed ratio is set to the maximum value of the speed ratio; The present invention is characterized by comprising means for controlling the speed ratio by performing feedback control so as to reach the reset target speed ratio.

[Effect]

In the present invention, in addition to the maximum value of the speed ratio that is limited by the structure of the CVT main body, a maximum value e max of the speed ratio in feedback control is separately set,
Target speed ratio e ^* is the maximum value e of this set speed ratio
When it is smaller than max, the speed ratio e is controlled by feedback control so that the input side rotational speed Nin of the CVT becomes the target input side rotational speed Nin ^* .
control. Since the output side rotational speed Nout of the CVT corresponds to the vehicle speed and cannot be suddenly changed, the speed ratio e can be controlled by performing feedback control so that the input side rotational speed Nin becomes the target input side rotational speed Nin ^* . On the other hand, if the target speed ratio e ^* is larger than the maximum value e max of the set speed ratio, the target speed ratio e ^* is once reset to the maximum value e max of the speed ratio, and then the speed ratio e The speed ratio e is controlled by performing feedback control so that the reset target speed ratio e ^* is achieved. That is, the target speed ratio e ^* is the maximum value e of the speed ratio
If smaller than max, input side rotation speed
Feedback control is performed targeting Nin, and when it is large, feedback control is performed targeting speed ratio e. Feedback control for the speed ratio e ensures that the speed ratio is maintained at the set maximum value, which prevents the CVT's movable disk from coming into contact with the stopper and causing the servo oil pressure to become unbalanced.
It is possible to accurately prevent transmission efficiency from being reduced due to excessive force being applied to the belt, and the durability of the belt can be improved.

【Example】

Embodiments of the present invention will be described with reference to the drawings. In FIG. 3, an output shaft 2 of an internal combustion engine 1 is brought into contact with an input shaft 5 of a CVT 4 via a clutch 3. The input shaft 5 and the output shaft 6 are provided parallel to each other, the input side fixed disk 7 is fixed to the input shaft 5, and the input side movable disk 8 is movable in the axial direction by splines or balls on the outer periphery of the input shaft 5. The output side fixed disk 9 is fixed to the output shaft 6 by means of a bearing, etc., and the output side movable disk 10 is fitted to the outer periphery of the output shaft 6 using a spline or a ball bearing so as to be movable in the axial direction. Note that the pressure receiving area of the movable side disk is set so that input side>output side, and the arrangement of the fixed disk and the movable disk in the axial direction is opposite to each other on the input side and output side. Fixed disks 7, 9 and movable disks 8, 10
The opposing surfaces of the discs are tapered to increase the distance from each other in the radial outward direction, and a belt 11 having a truncated conical cross section is placed between the input and output disks. Therefore, as the clamping force of the fixed and movable disks changes, the radial contact position of the belt 11 on the disk surface changes continuously. When the contact position of the belt 11 on the surfaces of the input side disks 7 and 8 moves radially outward, the contact position of the belt 11 on the surfaces of the output side disks 9 and 10 moves radially inward, and the CVT 4 The speed ratio e (=rotational speed Nout of the output shaft 6/rotational speed Nin of the input shaft 5) increases, and in the opposite case, e decreases. The power of the output shaft 6 is transmitted to drive wheels (not shown). The throttle opening sensor 18 detects the intake system throttle opening θth. The accelerator pedal and the intake system throttle valve are coupled so that the output horsepower of the engine is a desired function of the amount of depression of the accelerator pedal. The input side and output side rotation angle sensors 20, 21 detect the rotation angles and therefore the rotation speeds of the disks 7, 10, respectively. The line pressure generating valve 24 adjusts the line pressure Pl of the oil passage 29 by controlling the amount of oil as a hydraulic medium sent from the reservoir 26 via the oil passage 27 by the oil pump 25 to the oil passage 28. do. The hydraulic servo of the output side movable disk 10 is supplied with line pressure Pl via an oil passage 29. The flow rate control valve 30 controls the amount of oil flowing into and out of the movable disk 8 on the input side. In order to maintain the speed ratio e of CVT4 constant,
Line pressure oil passage 3 branching from oil passage 33 and oil passage 29
1 and the drain oil passage 32, that is, to maintain the axial position of the input side movable disk 8 constant and increase the speed ratio e, oil is supplied to the oil passages 31 to 33. In order to increase the clamping force between the side disks 7 and 8 and to decrease the speed ratio e, the hydraulic pressure of the hydraulic servo of the movable disk 8 is conducted to the atmosphere side through the drain oil passage 32 to connect the input side disks 7 and 8. Reduce the thrust between. Although the oil pressure in the oil passage 33 is below the line pressure Pl, the piston action area of the hydraulic servo on the input side movable disk 8 is larger than the piston action area of the hydraulic servo on the output side movable disk 10.
It is possible to make the tightening force of the output disks 9 and 10 larger than that of the output side disks 9 and 10. The line pressure Pl is controlled by the line pressure generation valve 24 so as to generate a tightening force that ensures torque transmission without the belt 11 slipping on the output side disks 9 and 10, and the line pressure Pl is controlled by the line pressure generating valve 24 to generate the tightening force on the input side disks 7 and 8. The speed ratio e is controlled by changing the flow rate control valve 30. The electronic control unit 38 includes a D/A (digital/analog converter) 40, an I/F (input interface) 41, and an A/D (analog/digital converter) that are connected to each other by an address data bus 39.
42, CPU43, RAM44, and ROM45. The analog output of the throttle opening sensor 18 is sent to the A/D 42, and the rotation angle sensor 20, 2
A pulse of 1 is sent to input interface 41. Outputs to the flow control valve 30 and line pressure generation valve 24 are output from the D/A 40 to amplifiers 50 and 51, respectively.
sent via. Details of the control can be found in the above-mentioned patent application in 1982.
Please refer to No.-67362. FIG. 4 is a flowchart corresponding to an embodiment of the present invention. In this embodiment, the speed ratio e of CVT4 is
A maximum value e max and a minimum value e min are set in advance. These e max and e min are set as allowable values that can suppress deterioration of the CVT transmission efficiency and the durability of the belt 11, and e max is smaller than the minimum speed ratio determined by the structure of the CVT 4, and e
min shall be a value larger than the minimum speed ratio determined by the structure. In step 56, the throttle opening θth is read.
In step 57, θth is calculated based on the θth−Nin ^* map.
The target input side rotational speed Nin ^* (=target engine rotational speed N e ^* ) is calculated from. In step 58, the actual output side rotational speed Nout is read. In step 59
The target speed ratio e ^* is calculated from Nin ^* and Nout. However, e ^* = Nout/Nin ^* . e ^* in step 60
and e max , and if e ^* < e max, the process proceeds to step 64, and if e ^* ≧ e max, the process proceeds to step 70. In step 64, e ^* and e min are compared, and if e ^* > e min, the process proceeds to step 66, and if e ^* ≦e min, the process proceeds to step 71. In step 65, the actual input side rotational speed Nin is read, and in step 66, feedback control of the input side rotational speed of the CVT 4 is performed. i.e. flow control voltage
The output voltage from the D/A 40 as Vin to the flow control valve amplifier 50 is calculated from Vin=K1·(Nin ^* −Nin) and output. However, K1 is a constant. Therefore, if e min < e ^* < e max, feedback control of the input side rotational speed Nin is performed. In step 70, e max is substituted for the target speed ratio e ^* .
In step 71, e min is substituted for the target speed ratio e ^* . In step 72, the actual input side rotational speed Nin is read. In step 73, the actual speed ratio e=
Calculate Nout/Nin. In step 74, the output voltage from the D/A 40 to the flow control valve amplifier 50 as the flow control voltage Vin is set as Vin=K1・(e ^* −e).
Calculate and output from. Therefore, if e ^* ≦ e min or e ^* ≧ e max, feedback control is performed so that the speed ratio e becomes e min or e max, and as a result, deterioration of the transmission efficiency and the durability of the belt 11 is avoided. . Note that when the CVT 4 is switched from the feedback control of the input side rotational speed Nin to the feedback control of the speed ratio e, the responsiveness during transients is slightly reduced. In step 77, engine output torque Te (=input torque Tin of CVT 4) is calculated from θth and Nin based on the θth and Nin-Te map. In step 78, the output voltage Vout from the D/A 40 to the line pressure generating valve 51 as the line pressure control voltage is set to Vout=K2・
Calculate Te・Nout/Nin. However, K2 is a constant. In this way, the line pressure is controlled to a substantially minimum value that ensures torque transmission in the CVT 4, and power loss is prevented. As described above, according to this embodiment, when the target speed ratio e ^* exceeds the range of e min < e ^* < e max,
Feedback control is performed so that e ^* becomes e min or e max, and the CVT speed ratio e is prevented from decreasing or increasing indefinitely, without deteriorating transmission efficiency and belt durability.
Can drive CVT. In addition, in the present invention, the minimum value e of the speed ratio
As for min, it is not necessarily necessary to set this.

【Effect of the invention】

As explained above, according to the present invention, the CVT is no longer operated at a maximum speed ratio that is limited by its structure, and the durability of the CVT belt etc. can be improved. Effects can be obtained.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the gist of the present invention, Figure 2 is a block diagram showing the gist of the present invention;
3 is a diagram showing changes in speed ratio e when the vehicle is driven on a predetermined test course, FIG. 3 is a schematic diagram of the entire vehicle power transmission device to which the present invention is applied,
The figure is a flowchart showing a control flow executed by the CPU of the power transmission device. 4...CVT, 7, 8...Input side disk, 9,
10...Output side disk, 30...Flow control valve,
38...Electronic control unit, e...Speed ratio, e ^* ...Target speed ratio, Nin...Input side rotation speed, Nin ^* ...
Target input side rotation speed, Nout...Output side rotation speed,
e max...Maximum value of speed ratio.

Claims (1)

[Scope of Claims] 1. Means for detecting the amount of depression of the accelerator pedal, Means for determining the target input side rotation speed based on the amount of depression of the accelerator pedal, Means for detecting the input side rotation speed, and Output side rotation speed. means for detecting the actual speed ratio from the input side rotation speed and the output side rotation speed; means for calculating the target speed ratio from the target input side rotation speed and the actual output side rotation speed; means for presetting a maximum value of the ratio; means for comparing the target speed ratio with the maximum value; when the target speed ratio is smaller than the maximum value;
means for controlling the speed ratio by performing feedback control so that the input side rotational speed becomes the target input side rotational speed, and when the target speed ratio is larger than the maximum value of the speed ratio, Means for controlling the speed ratio by once setting the speed ratio to the maximum value and then performing feedback control so that the speed ratio becomes the reset target speed ratio. Continuously variable transmission control device.