JPH0413577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a hydraulic control system for a belt-driven continuously variable transmission used, for example, as a power transmission system for automobiles.

BACKGROUND ART Continuously variable transmissions that can control the speed ratio to minimize the fuel consumption rate relative to the horsepower required by the driver have been attracting attention, and the applicant has previously developed a vehicle with a continuously variable transmission. proposed a power transmission device for For example, Japanese Patent Application No. 57-40747 (Japanese Patent Application No. 58-160661)
This is the belt-driven continuously variable transmission described in . Such a belt-driven continuously variable transmission is configured such that power is transmitted by a belt wrapped around an input-side disk and an output-side disk with variable effective diameters. The tension of the belt is controlled by changing the control pressure acting on a hydraulic servo that changes the effective diameter of the disk located on the driven side of the belt, that is, the output side disk in the normal power transmission direction. There is.

Problems to be Solved by the Invention By the way, if the tension of the bell described above, that is, the belt clamping force at the input side disk and the output side disk, is too low, power transmission will be impaired due to belt slippage, and if it is too high, the durability of the CVT will be reduced. It is desirable to control the oil pump appropriately, as this may cause damage to the oil pump or increase the power loss of the engine that drives the oil pump. Furthermore, the applicant has previously
Japanese Patent Application No. 57-96122 (Japanese Unexamined Patent Publication No. 58-214054) discloses a hydraulic control device for necessary and sufficient control of belt tension by increasing and decreasing the control pressure in relation to the torque of the input side disk and the output side disk. However, the present invention provides a technique for controlling the control pressure to an optimum value using a different principle.

Means for Solving the Problems The present invention has been made based on various studies against the background of the above-mentioned circumstances. As a result, the control pressure value at which belt slippage occurs in a belt-driven continuously variable transmission has been determined. This value is slightly lower than the control pressure at which the maximum transmission efficiency is obtained, and we have discovered that the control pressure can be adjusted to an optimal value based on the actual transmission efficiency of the belt-driven continuously variable transmission. The present invention has been made based on this knowledge.

That is, the gist of the present invention is to provide a belt-driven continuously variable transmission in which power is transmitted by a belt wound around an input side disk and an output side disk with variable effective diameters, in which the tension of the belt is controlled. a pressure regulating valve that regulates the control pressure applied to the hydraulic servo of the driven side disk of the input side disk and the output side disk for control, and based on the actual input torque and speed ratio from the pre-stored relationship, A hydraulic control device comprising: (a) a transmission efficiency for detecting the transmission efficiency of power from the input disk to the output disk; and (b) feedback correction means for correcting the control value so that the actual transmission efficiency detected by the transmission efficiency detection means is maintained near its maximum value.

Operation and Effects of the Invention The control pressure value at which the belt of the belt-driven continuously variable transmission occurs is a value close to the control pressure at which the maximum transmission efficiency of the belt-driven continuously variable transmission is obtained. Therefore, in the present invention, the control value is corrected by the feedback correction means so that the actual transmission efficiency detected by the transmission efficiency detection means is maintained near its maximum value, so that the tension of the belt is The pressure is regulated to the minimum optimum value within a range that does not cause any problem in transmission.

Example The present invention will be explained with reference to the drawings.

First, the entire vehicle power system to which the present invention is applied will be explained with reference to FIG. A crankshaft 2 of an engine 1 is connected to an input shaft 5 of a CVT 4 via a clutch 3. A pair of input side disks 6 and 7 are arranged to face each other, one input side disk 6 is supported by the input shaft 5 so as to be relatively movable in the axial direction, and the other input side disk 7 is fixed to the input shaft 5. has been done. A pair of output side disks 8 and 9 are also arranged to face each other, one output side disk 8 is fixed to the output shaft 10, and the other output side disk 9 is supported by the output shaft 10 so as to be relatively movable in the axial direction. has been done. The opposing surfaces of the pair of input side disks 6, 7 and output side disks 8, 9 are formed such that the distance between them increases radially outward. The belt 11 has a trapezoidal cross section and is stretched between the input disks 6 and 7 and the output disks 8 and 9. A pressure regulating (relief) valve 15 is connected to an oil passage 1 by an oil pump 17 from an oil pan 16.
Oil is sent through the oil passage 19 to generate control pressure, ie, line pressure, for adjusting the tension of the belt 11 in the oil passage 19. In order to adjust the line pressure, the flow rate of oil returned to the drain oil passage 20 is controlled, and the oil passage 19 is connected to the hydraulic servo of the output side disk 9. The flow rate control valve 24 is connected to the oil passage 19, the drain oil passage 25, and the oil passage 26, and the oil passage 26 is connected to the hydraulic servo of the input side disk 6. When increasing the servo oil pressure of the input side disc 6, the oil passage 26 is connected to the oil passage 19 in the flow control valve 24, and when decreasing the servo oil pressure of the input side disc 6, the oil passage 26 is connected to the oil passage 19. Connect to 25. Torque sensors 29 and 30 detect torques Tin and Tout of input shaft 5 and output shaft 10, respectively, from changes in the direction of the magnetic field. Rotation angle sensors 31 and 32 detect rotation speeds Nin and Nout of input side disk 7 and output side disk 8, respectively. The throttle actuator 35 controls the opening degree of the intake system throttle valve, and the accelerator pedal sensor 36 detects the amount of depression of the accelerator pedal 38 near the driver's seat 37.

As the servo oil pressure of the output side disk 9 increases, the output side disk 9 is pushed toward the output side disk 8, and accordingly, the contact position of the belt 11 on the disks 8 and 9 moves radially outward. . The line pressure is controlled so that the belt 11 does not slip against the disks 8 and 9. Further, as the servo oil pressure of the input side disk 6 increases, the input side disk 6 is pressed toward the input side disk 7,
Along with this, the belt 1 on the disks 6 and 7
The contact position No. 1 moves radially outward, thereby controlling the speed ratio of the CVT 4. The servo oil pressure Pin of the input side disk 6 ≦ the servo oil pressure Pout of the output side disk 9, but the pressure receiving area Ain of the hydraulic servo of the input side disk 6 ≧ the pressure receiving area Aout of the hydraulic servo of the output side disk 9, so it is less than 1. It is also possible to achieve a speed ratio of

The required horsepower is set as a function of the amount of depression of the accelerator pedal 38, and the target torque and target rotational speed of the engine are set as functions of the required horsepower. The opening degree of the intake system throttle valve is controlled as a function of the target torque, and the speed ratio of the CVT 4 is controlled as a function of the target rotational speed. The details of the control of the engine torque Te and rotational speed Ne are as described in the above-mentioned Japanese Patent Application No. 57-40747.

The basic idea of the present invention will be explained with reference to FIG.
The transmission efficiency η can be calculated, for example, from the following equation.

η=Nout・T〜out/Nin・T〜in where Nout: Rotational speed of the output side disks 8, 9 Nin: Rotational speed of the input side disks 6, 7 T〜out: Torque Tout of the output side disks 8, 9 DC component T~in: DC component of the torque Tin of the input side disks 6, 7 According to Fig. 2, as the line pressure Pl, that is, the output side servo oil pressure Pout decreases, the transmission efficiency η
increases, and when η passes the peak value, η becomes the line pressure.
It decreases rapidly as Pl decreases, and belt 11 slips (dashed line). The peak value of η is belt 11
If the line pressure Pl is controlled so that η is in the vicinity of the start of slippage, and therefore η is in the vicinity of its peak value, the line pressure Pl will be approximately the minimum value that does not cause any trouble in power transmission. In the present invention, the line pressure is controlled so that η is in the vicinity of this peak value, that is, in the vicinity where η starts decreasing rapidly as the line pressure decreases.

FIG. 3 is a block diagram of the present invention. In the block 44, the input voltage Vout of the pressure regulating valve amplifier 45 is
is set from the following formula stored in advance.

Vout=K・T~n・Nin/Nout where K is a constant. The Vout thus calculated becomes the initial value of Vout. The low-pass filter 48 sends the DC components T~in and T~out of Tin and Tout to the block 49. Block 49 calculates η. In block 50, α is calculated from the following equation.

α=η ^(k) /η ^(k ′ ⁾ −a However, η ^(k) is the actual efficiency of the CVT 4, that is, the current efficiency. η ^(k ′ ⁾ is the maximum efficiency of the CVT4, that is, the peak value of the curve in FIG. a is a constant, for example 1, which takes a positive value when the line pressure is larger than the value corresponding to its maximum efficiency η ^(k ' ⁾ , and takes a negative value when it is smaller.

In block 51, the correction amount ΔV or -ΔV is selected based on whether α<0 or α≧0. That is,
If a=1 in the above equation, the actual efficiency η ^(k)
is lower than the maximum efficiency value η ^(k ′ ⁾ of CVT4 or a value near it, and the line pressure at that time is larger than the value corresponding to the maximum efficiency η ^(k ′ ⁾ , α<0.
−ΔV is selected, but the actual efficiency η ^(k)
is lower than the maximum efficiency value η ^(k ′ ⁾ of CVT4 or a value around it, and the line pressure at that time is smaller than the value corresponding to the maximum efficiency η ^(k ′ ⁾ , α≧0.
Therefore, +ΔV is selected. In block 52
Assign Vfb ^(k-1) ±ΔV to Vfb ^(k) . However, Vfb ^(k)
is the current feedback amount, and Vfb ^(k-1) is the previous feedback amount. At the addition point, block 54, Vout+Vfb ^(k) is substituted for Vout, and the new Vout is sent to the pressure regulating valve amplifier 45. Vout
As the line pressure Pl increases, the line pressure Pl also increases. When a=1 or a−1, the actual efficiency η ^(k) is the second
If it is to the left of the peak value in the figure, α<0
Therefore, the line pressure Pl is increased, and since α>0 if the actual efficiency η ^(k) is to the right of the peak value in FIG. 2, the line pressure Pl is decreased. As a result, the line pressure Pl is controlled so that α=0, that is, near the actual efficiency η ^(k) peak value.

In this embodiment, the block 44 functions as a control value determining means for determining a control value for driving the pressure regulating valve 15 based on the actual input torque and speed ratio from a pre-stored relationship. Block 49 functions as a transmission efficiency detection means,
The blocks 50, 51, 52, and 54 function as feedback correction means for correcting the control value so that the actual transmission efficiency is maintained near its maximum value.

FIG. 4 shows details of the electronic control device. By bus 55, CPU56, RAM57, ROM58,
I/F (interface) 59, A/D (analog/digital converter) 60, D/A (digital/
The analog converters) 61 are connected to each other.
Pulses from the input side rotation angle sensor 31 and the output side rotation angle sensor 32 are sent to the I/F 59. Input side torque sensor 29 and output side torque sensor 3
The analog output of 0 is sent to the A/D 60 via the low pass filter 48. Therefore A/D60
Then, the DC components Tin,
A/D conversion of Tout is performed. The output voltage Vout of the D/A 61 is sent to the pressure regulating valve amplifier 45.

FIG. 5 is a flowchart of an algorithm according to the present invention. In step 71, T~in, Nin,
Load Nout. In step 72, the input voltage of the pressure regulating valve amplifier 45 Vout=K・T~in・Nin/Nout
is calculated based on the data read in step 71. The Vout calculated in step 72 becomes the initial value of Vout. In step 73, Nin, Nout,
Read Tin, Tout. In step 73, Nin,
Read Nout, Tin, Tout. In step 74
DC components T~in and T~out of Tin and Tout are detected.
In step 75, η=Nout, T~out/Nin・T~in
Calculate. In step 76, α=η ^(k) /η ^(k ′ ⁾ −
a is calculated based on the data read or detected in steps 73 and 74. In step 77, α is compared with 0, and if α≧0, the process proceeds to step 82, and if α<0, the process proceeds to step 83. In step 82, Vfb ^(k-1) - ΔV is assigned to Vfb ^(k) , and in step 83, Vfb ^(k-1) + ΔV is assigned to Vfb ^(k).
Assign to . In step 84, Vout+Vfb
Assign it to Vout and return to step 73.

As described above, according to the present invention, based on the fact that the line pressure near the point where the CVT belt begins to slip can be detected from the transmission efficiency of the CVT, the line pressure is controlled in relation to the detected value of the transmission efficiency of the CVT, thereby increasing the line pressure. It is possible to control the torque to a substantially minimum value that does not interfere with torque transmission.

[Brief explanation of drawings]

Fig. 1 is an overall schematic diagram of a vehicle power transmission device to which the present invention is applied, Fig. 2 is a line pressure-transmission efficiency characteristic graph for explaining the basic idea of the present invention, and Fig. 3 is a diagram of the present invention. FIG. 4 is a detailed block diagram of the electronic control unit, and FIG. 5 is a flowchart of the algorithm according to the invention. 4...CVT, 6, 7...Input side disk, 8,
9... Output side disk, 11... Belt, 15...
...Pressure regulating valve, 29, 30...Torque sensor, 31,
32...Rotation angle sensor 44...Block (control value determining means), 49...Block (transmission efficiency detection means), 50, 51, 52, 54...Block (feedback correction means).

Claims (1)

[Claims] 1. In a belt-driven continuously variable transmission in which power is transmitted by a belt wrapped around an input side disk and an output side disk with variable effective diameters, in order to control the tension of the belt. A pressure regulating valve that regulates the control pressure applied to the hydraulic servo of the driven side disk of the input side disk and the output side disk, and the pressure regulating valve is adjusted based on the actual input torque and speed ratio from the relationship stored in advance. A hydraulic control device comprising a control value determining means for determining a control value for driving, a transmission efficiency detecting means for detecting the transmission efficiency of power from the input side disk to the output side disk, and the transmission efficiency. A hydraulic control device for a belt-driven continuously variable transmission, comprising feedback correction means for correcting the control value so that the actual transmission efficiency detected by the detection means is maintained near its maximum value.