JPH0413576B2 - - Google Patents

Description

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

BACKGROUND ART A belt-driven continuously variable transmission (hereinafter referred to as CVT) that can control the speed ratio to minimize the fuel consumption rate relative to the horsepower required by the driver has been attracting attention, and the present applicant has previously proposed a power transmission system for vehicles equipped with CVT. For example, the patent application filed in 1987-
No. 40747 (Unexamined Japanese Patent Publication No. 58-160661) or Unexamined Japanese Patent Publication No. 160661
This is the belt-driven continuously variable transmission described in No.-67362 (Japanese Patent Application Laid-open No. 58-184347). 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. ing.

Problems to be Solved by the Invention By the way, if the belt tension mentioned above, that is, the belt clamping force at the input side disk and the output side disk, is too small, the power transmission will be impaired due to belt slippage, and if it is too large, 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. In contrast, the present applicant previously filed Japanese Patent Application No. 57-96122 (Japanese Unexamined Patent Application No. 58-9612)
No. 214054), they filed an application for a hydraulic control device that controls the control pressure as necessary and sufficiently by increasing or decreasing it in relation to the torque of the input side disk and the output side disk. However, such hydraulic control devices require a torque sensor to detect the actual transmitted torque, but torque sensors generally have low accuracy and are expensive, so the accuracy of hydraulic control cannot be obtained. Not only that, but it also had the disadvantage of not being practical in terms of cost.

Means for Solving the Problems As a result of various studies based on the above circumstances, the inventor of the present invention found that the actual hydraulic pressure P~ _io in the hydraulic servo of the input side disk in a belt-driven continuously variable transmission is as follows.
Theoretical relationship between the hydraulic pressure in the hydraulic servo of the input side disk P~ _io and the hydraulic pressure in the hydraulic servo of the output side disk P~ _put P~ _io = Sr・P The hydraulic pressure value in the servo of the input side disk obtained from _put It has been discovered that when P~ _put is reached, the belt of the belt-driven continuously variable transmission starts to slip. 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 acting on the hydraulic servo of the driven side disk of the input side disk and the output side disk for control;
a control value determining means for determining a control value for driving the pressure regulating valve based on the actual input torque and speed ratio from a pre-stored relationship, the hydraulic control device comprising: (a) the input; (b) hydraulic pressure detection means for detecting the hydraulic pressure in the hydraulic servo of the side disk and the hydraulic pressure in the hydraulic servo of the output side disk;
The hydraulic pressure in the input side disk obtained from the theoretical relationship between the hydraulic pressure in the hydraulic servo of the input side disk and the hydraulic pressure in the hydraulic servo of the output side disk, and the actual hydraulic pressure in the hydraulic servo of the input side disk. and feedback correction means for correcting the control value so that the differential pressure value is maintained at a predetermined value.

Operation and Effects of the Invention In this way, the hydraulic pressure in the input side disk and the actual input can be obtained from the theoretical relationship between the hydraulic pressure in the hydraulic servo of the input side disk and the hydraulic pressure in the hydraulic servo of the output side disk. The control value is corrected by the feedback correction means so that the differential pressure value between the side disk and the hydraulic pressure in the hydraulic servo is maintained at a predetermined value. Therefore, since the actual oil pressure in the hydraulic servo of the input side disk is maintained at the value immediately before belt slippage occurs, the control pressure is set to the minimum value within the range that does not interfere with torque transmission, that is, the CVT. This allows the pressure to be regulated to the optimum control pressure.

Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a vehicle power transmission device to which the present invention is applied. In the figure, a crankshaft 2 of an engine 1 is connected to an input shaft of a CVT 4 via a crank 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 movable in the axial direction, and the other input side disk 7 is supported by the input shaft 5.
Fixed. A pair of output side disks 8, 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 movable in the axial direction. 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 as the pair goes radially outward. The belt 11 is an endless belt having a trapezoidal cross section, and is wound around the input side disks 6 and 7 and the output side disks 8 and 9. Oil is force-fed from an oil pan 16 to a pressure relief valve 15 via an oil passage 18 by an oil pump 17. 19 to occur. In the pressure regulating valve 15, the return flow rate of oil to the drain oil passage 20 is controlled in order to regulate the line pressure Pl, and the oil passage 19 that guides the regulated line pressure Pl is connected to the hydraulic servo of the output side disk 9. It is connected. The flow 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. In the flow rate control valve 24, the oil passage 26 and the oil passage 19 are connected to each other, so that the hydraulic pressure in the hydraulic servo of the input side disk 6 is increased. Also,
By connecting the oil passage 26 and the drain oil passage 25, the hydraulic pressure in the hydraulic servo of the input side disk 6 is reduced.

The torque sensor 29 detects the torque T _io of the input shaft 5 from changes in the direction of the magnetic field. Rotation angle sensor 3
1 and 32 detect the rotational speeds Nio _{and Nput} of the input side disk 7 and the output side disk 8, respectively.
The oil pressure sensors 33 and 34 respectively detect the oil pressure P _io in the hydraulic servo of the input side disk 6 and the oil pressure P _put (=line pressure Pl) in the hydraulic servo of the output side disk 9.
Detect. The throttle actuator 35 is
The opening degree _θth of the intake system throttle valve is controlled, and the accelerator pedal sensor 36 controls the accelerator pedal 3 of the driver's seat 37.
The amount of depression of 8 is detected.

As the hydraulic pressure P _put in the hydraulic servo of the output side disk 9 increases, the output side disk 9 is pressed toward the output side disk 8 side, and the belts wound around the output side disks 8 and 9 are accordingly 1
1 diameter is increased. Line pressure Pl is belt 1
1 is controlled so that it does not slip with respect to the disks 8 and 9. In addition, as the hydraulic pressure P _io in the hydraulic servo of the input side disk 6 increases, the input side disk 6 is pressed toward the input side disk 7 side, and the belt 1 wrapped around the input side disks 6 and 7 is pressed.
The hanging diameter of CVT4 has been increased.
The speed ratio e (=output shaft rotational speed _Nput /input side rotational speed _Nio ) is controlled. Hydraulic pressure P _io in the hydraulic servo of the input side disk 6 ≦ Hydraulic pressure P _put in the hydraulic servo of the output side disk 9 , but the input side disk 6
Hydraulic servo pressure receiving area A _io ≧ Output side disk 9
Since the pressure receiving area of the hydraulic servo is _Aput , it is possible to achieve a speed ratio of 1 or more.

In the speed ratio control and throttle valve opening control of this embodiment, 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 1 are set as a function of the required horsepower,
It is stored in advance. The speed ratio e of the CVT 4 is adjusted so that the target rotation speed matches the actual engine rotation, while the throttle valve opening of the intake system is set as a function of the target torque, so that the target torque can be obtained. The throttle valve opening θ _th is adjusted as follows. The torque T _e and rotational speed N _e of the engine 1 are the same as those described in the aforementioned Japanese Patent Application No. 57-40747 and Japanese Patent Application No. 57-67362.

The basic idea of line pressure control in this embodiment will be explained using FIG. 2. In the CVT4 geometric model,
There is a theoretical relationship between the hydraulic pressure P _io in the hydraulic servo of the input side disk 6 and the hydraulic pressure P _put in the hydraulic servo of the output side disk 9 as shown in the following equation (1).

P _io /P _put = Sr...(1) This Sr is defined by the following formula (2),
The winding angles φ _io and φ _put in this equation (2) are defined as shown in FIG. 3, and are as shown in the following equations (3) and (4).

Sr＝A _put・φ _io /A _io・φ _put …(2) φ _io =π+2φ ₁ …(3) φ _put =π−2φ ₁ …(4) However, the relationship between P _io and P _put above is based on belt 11 Due to various characteristics of
The characteristic line is shown as a solid line in the figure. That is,
In areas where the line pressure Pl (=P _put ) is relatively high, P _io
and P _put are in the area above the broken line showing P _io = Sr・P _put , and when the line pressure Pl decreases, P _io and P _put match.The area matches the broken line showing P _io = Sr・P _put Then, the belt 11 starts to slip. Therefore, in this example, the intersection of the characteristic line showing the actual relationship between P _io and P _put and the broken line showing the theoretical relationship between P _io and P _put
Point Q ₂ above Q ₁ by a predetermined value a (constant) in the vertical axis direction
so that the line pressure Pl is maintained at That is, the control value V _put of the pressure regulating valve is corrected so that the actual P _io and P _put are located on the line shown as P _io =Sr·P _put +a. In other words, the hydraulic pressure P _io in the hydraulic servo of the input side disk 6 and the output side disk 9
The theoretical relationship between the hydraulic pressure in the hydraulic servo P _put and P _io =
The differential pressure value P _io −Sr・P _put between the hydraulic pressure in the hydraulic servo of the input disk 6 obtained from Sr・P _put and the actual hydraulic pressure in the hydraulic servo P _io of the input _disk 6 is determined in advance. The control value is maintained at the value a.
This allows V _put to be corrected.

FIG. 4 is a functional block diagram of this embodiment. In the figure, in block 40, the input shaft torque T _io of the CVT 4 (=DC component T _e of the output torque of the engine 1), the input shaft rotation speed N _io , and the output shaft rotation speed N _put
From this, the basic value V _puti of the input voltage V _put of the pressure regulating valve amplifier 41 is calculated according to the following formula (5) stored in advance.

_Vputi =K・_Tio・_Nio / _Nput ...(5) However, K is a constant.

Here, as shown in FIG. 5, the DC component T _io (=output torque T _e of the engine 1) of the input shaft torque of the CVT 4 is determined by the engine rotational speed N _e (=N _io ) and the throttle valve opening θ. _Therefore , instead of directly detecting T _io from the output of the input torque sensor 29, the actual engine rotation speed can be determined from the function shown in FIG.
T _io may be calculated based on N _e and throttle valve opening θ _th . Low pass filter 45 in Figure 4
is a pulsating component included in the signals output from the input side oil pressure sensor 33 and the output side oil pressure sensor 34,
For example, it is a filter with frequency characteristics that removes pitch noise of the belt 11, pulsation noise of a hydraulic pump, fluctuations in input torque, etc.
Input side servo hydraulic pressure P _io and output side servo hydraulic pressure of
The DC components P~ _io and P~ _put of _Pput are discriminated and output. In block 46, α is calculated from the following equation (6).

α=P~ _io -Sr・P~ _put -a...(6) In block 47, whether the above α is α≧0 or α
Depending on whether <0, increase value ΔV or decrease value -
Screen ΔV. In block 48, the current, ie, K-th feedback amount V _fb ^(k) is calculated from the following equation (7). However, in the following equation (7), V _fb ^(k-1) is the previous feedback amount, that is, the K-1th feedback amount.

V _fb ^(k) = V _fb ^(k-1) ±ΔV (7) The block 50 is an adder that calculates the basic value V _puti of the input voltage V _put of the pressure regulating valve amplifier 41 and the feedback amount V _fb ^(k) is added, and a control value V _put for the amplifier 41 that drives the pressure regulating valve 15 is output.

As a result, if α≧0, the actual hydraulic pressure in the hydraulic servo of the input side disk 6, P~ _io , becomes the hydraulic pressure in the hydraulic servo of the input side disk obtained from the theoretical relationship P~ _io = Sr・P~ _put If it is larger than Sr・P~ _put , the control value V _put is reduced by the decrease value −ΔV, and on the other hand, if α<0, that is, the actual hydraulic pressure P _io in the hydraulic servo of the input side disk 6 is , the control value _Vput is increased by the increase value ΔV if it is smaller than the hydraulic pressure in the hydraulic servo Sr·P~ _put of the input side disk obtained from the theoretical relationship P~ _io =Sr·P~ _put . As a result, the input side disk obtained from the theoretical relationship P~ _io = Sr・P~ _put between the hydraulic pressure in the hydraulic servo of the input side disk 6 P~ _io and the hydraulic pressure in the hydraulic servo P~ _put of the output side disk 9 Hydraulic pressure in the hydraulic servo Sr.
The differential pressure value P _{~ io} -Sr·P~put between P~ _put and the actual hydraulic pressure P~ _io in the hydraulic servo of the input side disk 6 is maintained at a predetermined value a. Therefore, the actual hydraulic pressure P _io in the hydraulic servo of the input side disk 6 is equal to the belt 1.
Since the line pressure Pl, which is the belt tension control pressure, is maintained at the value immediately before slippage occurs, the line pressure Pl, which is the belt tension control pressure, can be adjusted to the minimum value within the range that does not interfere with torque transmission, that is, the optimum belt control pressure for CVT4. This is possible.

In this embodiment, the block 40 drives the pressure regulating valve 15 for regulating the line pressure Pl based on the actual input torque T _io and speed ratio N _put /N _io from equation (5) stored in advance. It corresponds to the control value determining means for determining the control value to be
6, 47, 48, and 50 represent the theoretical relationship between the hydraulic servo internal hydraulic pressure P~ _io of the input side disk 6 and the hydraulic servo internal hydraulic pressure P~ _put of the output side disk 9 P _io =Sr・P~ _pu
The differential pressure value P~ _io −Sr・P~ _put between the hydraulic servo internal hydraulic pressure Sr・P~ _put of the input side disk obtained from _t and the actual hydraulic servo internal hydraulic pressure P~ _io of the input side disk 6 is predetermined. This corresponds to feedback correction means for correcting the control value so that the control value a is maintained at the specified value a.

FIG. 6 shows details of the electronic control device.
In the figure, CPU56, RAM57, ROM58,
An I/F (interface) 59, an A/D converter 60, and a D/A converter 61 are connected to the data bus line 5.
5 and are connected to each other by 5. The output pulses are supplied to the output pulse I/F 59 of the input side rotation angle sensor 31 and the output side rotation angle sensor 32. Analog outputs from the input torque sensor 29, the input oil pressure sensor 33, and the output oil pressure sensor 34 are sent to the A/D converter 60 via a low pass filter 45. Therefore, the A/D converter 60 performs A/D conversion of the DC components of the torque _Tio of the input side disks 6 and 7, the input side servo oil pressure _Pio , and the output side servo oil pressure _Pput . The output voltage _Vput of the D/A converter 61 is sent to the pressure regulating valve amplifier 41. When T _io is calculated from the throttle valve opening θ _th and the engine rotational speed _Ne , the input side torque sensor 29 can be omitted. In this case, the throttle valve opening degree θ _th corresponds to the output signal to the throttle actuator 35 and exists as an internal signal of the electronic control device, and is
As disclosed in No. 67362, it is a function of the amount of depression of the accelerator pedal 38.

FIG. 7 is a flowchart of the algorithm of this embodiment. In the figure, in step 72,
T _io , N _io , and N _put are read. If there is no input side trick sensor 29 and T _io cannot be read directly, the actual throttle valve opening θ _th and engine rotation speed can be determined from the pre-stored relationship shown in Fig. 5.
_Tio is calculated based on N _e . In step 73, the basic control amount to be supplied to the pressure regulating valve amplifier 41 is
V _puti is calculated from the pre-stored equation (5). In step 74, the DC components P~ _io and P _{~ put} of the input side servo oil pressure Pio and the output side servo oil pressure _Pput are read. In step 75, α is calculated from the previously stored equation (6). In step 76,
It is determined whether the above α is α≧0 or α<0. If α≧0, the previous feedback amount V _fb ^(k-1) is decreased by ΔV in step 77, and the current feedback amount is
V _fb ^(k) is determined, and if α<0, the previous feedback amount V _fb ^{(k-1) is} determined in step 78.
is increased by ΔV, thereby determining the current feedback amount V _fb ^(k) . Then, _in step 79, the control value V put is calculated by adding the current feedback amount V _fb ^(k) calculated in step 77 or 78 to the basic control amount V _puti calculated in step 73. .

As described above, according to this embodiment, the point indicating the actual input side servo oil pressure P~ _io and the output side servo oil pressure P~ _put is the point that indicates the actual input side servo oil pressure P~ _io and the output side servo oil pressure P~ _put . Taking advantage of the phenomenon that the belt 11 starts to slip when it reaches the broken line in FIG. 2, which shows the theoretical relationship, the control value V _{put is set} so that a predetermined distance a is maintained between that point and the broken line. By adjusting the line pressure Pl, the line pressure Pl is adjusted to a value immediately before the slippage start point of the belt 11 of the CVT 4, so that the line pressure Pl is set to a necessary and sufficient optimum pressure.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram of a vehicle power transmission system to which an embodiment of the present invention is applied. Figure 2 shows
FIG. 2 is a diagram illustrating the line pressure control principle of the embodiment of FIG. 1; FIG. 3 is a diagram illustrating the belt wrap angle in the embodiment of FIG. 1. Figure 4 is the first
7 is a functional block diagram of the electronic control device of FIG. 6 provided in the illustrated embodiment; FIG. FIG. 5 is a diagram showing the relationship between the output torque of the engine, the engine rotation speed, and the throttle valve opening in the embodiment of FIG. 1.
FIG. 6 is a block diagram showing an electronic control device included in the embodiment of FIG. 1. Figure 7 shows the 6th
3 is a flowchart illustrating the operation of the electronic control device shown in the figure. 4...CVT, 6, 7...Input side disk, 8,
9... Output side disk, 11... Belt, 15...
... Pressure regulating valve, 33, 34 ... Oil pressure sensor (oil pressure detection means), 40 ... Block (control value determining means), 4
6, 47, 48, 50...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 acting on 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 drive control value, the hydraulic control device comprising: hydraulic pressure detection means for detecting the hydraulic pressure in the hydraulic servo of the input-side disk and the hydraulic pressure in the hydraulic servo of the output-side disk, respectively. means, the hydraulic pressure in the hydraulic servo of the input side disk obtained from the theoretical relationship between the hydraulic pressure in the hydraulic servo of the input side disk and the hydraulic pressure in the hydraulic servo of the output side disk, and the actual hydraulic pressure in the hydraulic servo of the input side disk. A hydraulic control device for a belt-driven continuously variable transmission, comprising feedback correction means for correcting the control value so that the differential pressure value with respect to the hydraulic pressure is maintained at a predetermined value.