JPH0428945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a control method for a continuously variable transmission (hereinafter referred to as "CVT") used as a power transmission device for a vehicle, and particularly relates to a control method during acceleration. .

Conventional technology and its issues CVT has a speed ratio e (=output side rotational speed Nout/
The input side rotational speed (Nin) can be continuously controlled and is used in vehicles as a power transmission device with excellent fuel consumption efficiency. In the conventional CVT control method, if there is a deviation between the actual engine rotation speed Ne and the target engine rotation speed No, a gear shift (change in speed ratio e) is performed regardless of the magnitude of the requested acceleration. There is. However, shifting when slow acceleration is required gives the driver the impression that the change in the engine rotational speed Ne is too large compared to the change in the vehicle speed V, which is undesirable in terms of driving sensation (drive feeling). CVT has the disadvantage that fuel consumption efficiency deteriorates because the transmission efficiency during gear shifting decreases.

An object of the present invention is to provide a CVT control method that can improve driving sensation and fuel consumption efficiency during slow acceleration.

Means for Solving the Problems In order to achieve this object, according to the present invention, the target engine rotational speed No. is set as a function of engine operating parameters such as the intake system throttle opening θ or the intake pipe negative pressure, and the actual Control the CVT so that the engine rotation speed Ne becomes the target engine rotation speed No.
In the CVT control method, slow acceleration is required,
Further, when the deviation between the actual engine rotation speed and the target engine rotation speed is larger than a predetermined value, the speed ratio e of the CVT is maintained at a constant value.

Operation and Effects of the Invention Therefore, during slow acceleration, if the deviation between the actual engine rotation speed and the target engine rotation speed is larger than a predetermined value, the vehicle speed V increases only due to an increase in the output torque of the engine. , the engine rotational speed Ne and the vehicle speed V increase correspondingly, and the problem that the increase in the engine rotational speed Ne is too large relative to the increase in the vehicle speed V is prevented. In addition, during slow acceleration, the CVT shift is canceled when the deviation between the actual engine speed and the target engine speed is larger than a predetermined value.
During this suspension period, CVT transmission loss due to gear shifting is suppressed, and fuel consumption efficiency can be improved.

As a result of the speed ratio e being held constant, the responsiveness decreases accordingly, but as large responsiveness as during sudden acceleration is not required during slow acceleration, there is no problem with the responsiveness during slow acceleration. do not have.

In a preferred embodiment, the speed ratio e of the CVT after acceleration detection is maintained during the slow acceleration period.

Whether the acceleration is slow or not can be detected by comparing the throttle opening θ with a predetermined value θ1 or by comparing the throttle opening θ with time.

Example Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, 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 6a, 6b are provided opposite to each other, one input side disk 6a is provided on the input shaft 5 so as to be relatively movable in the axial direction,
The other input side disk 6b is fixed to the input shaft 5. Also, a pair of output side disks 7a, 7b
are also provided facing each other, one output side disk 7a is fixed to the output shaft 8, and the other input side disk 7b is provided on the output shaft 8 so as to be movable in the axial direction. The belt 9 has an isosceles trapezoidal cross section and is stretched between the input side disks 6a, 6b and the output side disks 7a, 7b. Opposing surfaces of input side disks 6a and 6b, and output side disk 7
The opposing surfaces of a and 7b are formed into a tapered cross section so that the distance between them increases as they move outward in the radial direction. Input side and output side disks 6a, 6b, 7a, 7b in relation to an increase or decrease in the distance between opposing surfaces.
The radius of engagement of the belt 9 increases or decreases, and the speed ratio e and the transmitted torque change. oil pump 1
4 is a pressure regulating valve 16 that absorbs oil from an oil sump 15.
send to The linear solenoid type pressure regulating valve 16 controls the amount of oil discharged to the drain 17 to control the line pressure of the oil passage 18 . The oil passage 18 is connected to the output side disk 7
It is connected to the hydraulic cylinder b. The linear solenoid type flow control valve 19 includes an input side disk 6a,
By increasing the pressing force between 6b and speed ratio e (speed ratio e
=Rotational speed Nout/ of output side disks 7a, 7b
When increasing the rotational speed Nin of the input side disks 6a and 6b (where Nin = engine rotational speed Ne), the oil path 2 to the hydraulic cylinder of the input side disk 6a
In the case where the speed ratio e is decreased by increasing the flow cross-sectional area between the oil passage 20 and the oil passage 18, cutting off the connection between the oil passage 20 and the drain 17, and reducing the pressing force between the input side disks 6a and 6b. There are oil lines 18 and 2.
0 and oil passage 20 and drain 17.
Control the cross-sectional area of flow between Rotation angle sensor 2
3 and 24 detect the rotational speeds Nin and Nout of the input side disk 6b and the output side disk 7a, respectively. The cylinder oil pressure of the output side disk 7b, that is, the line pressure, is controlled to the minimum oil pressure that can ensure torque transmission without the belt 9 slipping, thereby controlling the drive loss of the pump 14. The speed ratio e of the CVT 4 is controlled by the flow rate of oil to the input side disk 6a. Note that the cylinder oil pressure of the output side disk 7b is the cylinder oil pressure of the input side disk 6a, and the pressure receiving area of the cylinder piston is on the input side>
It is the output side, and a speed ratio e of 1 or more can be realized. The water temperature sensor 25 detects the temperature of the cooling water of the engine 1. The throttle opening sensor 26 detects the opening θ of an intake system throttle valve (not shown) that is linked to the accelerator pedal 27 . The shift position sensor 28 detects the range of a shift lever (not shown) near the seat 29.

FIG. 2 is a block diagram of the electronic control unit.
The CPU 32, RAM 33, ROM 34, I/F (interface) 35, A/D (analog/digital converter) 36, and D/A (digital/analog converter) 37 are connected to each other by a bus 38. The output pulses of the rotation angle sensors 23, 24 and the shift position sensor 28 are sent to the interface 35.
The analog outputs of the water temperature sensor 25 and throttle opening sensor 26 are sent to the A/D 36, and the output of the D/A 37 is sent to the pressure regulating valve 16 and flow control valve 19.

To roughly explain the control principle of CVT4, the target engine rotation speed No. is determined as a function of engine operating parameters such as intake system throttle opening θ and vehicle speed
(=Target input side rotation speed Nino) is calculated. Third
The figure shows the relationship between θ and No when the target engine rotational speed No is a function of only the throttle opening θ. In setting the relationship shown in Figure 3, the horsepower required for the internal combustion engine 1 is determined by adjusting the throttle opening θ
The engine rotation speed Ne that can produce the required horsepower with the minimum amount of fuel consumption is set as the target engine rotation speed No. At low vehicle speeds, the change in engine rotational speed Ne for a constant change in throttle opening θ is reduced to avoid deterioration of driving sensation, and at high vehicle speeds, the amount of increase in vehicle speed V for a constant change in throttle opening θ is reduced. It is preferable to improve the driving performance by increasing the value of Nino, and for this purpose, the target input side rotational speed Nino may be a function of the throttle opening θ and the vehicle speed V. In that case, set it based on the characteristic line in Figure 3. Also, the target speed ratio eo is
It becomes Nout/No. However, Nout is the actual output rotation speed of CVT4. In CVT4, the flow control valve 1
9 is controlled.

FIG. 4 is a flowchart of the control routine of CVT4. When rapid acceleration is required, the engine rotation speed Ne is increased to the target engine rotation speed No by operating the flow control valve 19 and reducing the speed ratio e of the CVT 4, but when slow acceleration is required. In this case, the speed ratio e of the CVT 4 is held at the value e1 immediately before acceleration detection until the engine rotation speed Ne reaches the vicinity of the target engine rotation speed No, and the engine rotation speed Ne is increased only by increasing the output torque of the engine 1. . Therefore, the engine rotational speed Ne can be increased in accordance with the increase in the vehicle speed V, and it is possible to avoid deterioration of the driving feeling due to the increase in the engine rotational speed Ne being too large compared to the increase in the vehicle speed V during slow acceleration. I can do it. Furthermore, as a result of preventing the CVT 4 from shifting during slow acceleration, an increase in transmission loss due to shifting is suppressed, and fuel consumption efficiency can be improved. To explain each step in detail, in step 40, the currently detected throttle opening θ is compared with the previously detected throttle opening θ', and if θ>θ', that is, if acceleration is required, step 42 is performed. If the value is θθ', step 40 is executed again. In step 42, the target input side rotational speed No. is calculated from the throttle opening θ, the vehicle speed V, etc. In step 44, the throttle opening θ is compared with a predetermined value θ1, and if θ>θ1, that is, rapid acceleration is required, the process proceeds to step 46, and if θθ1, that is, slow acceleration is required, the process proceeds to step 52. In addition, in determining whether the requested acceleration is sudden acceleration or slow acceleration, the difference Δθ (=θ−θ′) between the current throttle opening θ and the previous throttle opening θ′ is compared with a predetermined value Δθ1. It's okay. That is, if Δθ>Δθ1, it is rapid acceleration, and if ΔθΔθ1, it is slow acceleration. In step 46, the engine rotational speed Ne is detected. In step 48, |No−Ne| is compared with a predetermined value C, and |
If No-Ne|<C, that is, the actual engine rotation speed Ne is sufficiently close to the target engine rotation speed No, the routine ends; If Ne is far from the target engine speed No., proceed to step 50. In step 50, the control amount to the flow rate control valve 19 is
The change in Vi ΔVi is the function f(No−Ne) of No−Ne
Then, the process returns to step 46. In step 52, the speed ratio e1 at that time, that is, the speed ratio e1 immediately after the acceleration detection is detected. step
54, the speed ratio e is fixed at e1. In step 56, the engine rotational speed Ne is detected. In step 58, similarly to step 48, |No-Ne| is compared with a predetermined value C, and if |No-Ne|<C, the routine is terminated, and if |No-Ne|C, the process returns to step 56. .

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the entire CVT to which the present invention is applied, Fig. 2 is a block diagram of the electronic control device, and Fig. 3 is a schematic diagram of the entire CVT to which the present invention is applied.
The figure is a graph showing the relationship between throttle opening and target engine speed, and Figure 4 is a flowchart of the CVT control routine. 4...CVT, 19...Flow control valve, 23...
Input side rotation angle sensor, 26...throttle opening sensor.

Claims (1)

[Claims] 1. A continuously variable transmission for a vehicle that sets a target engine rotation speed as a function of engine operating parameters and controls the continuously variable transmission so that the actual engine rotation speed becomes the target engine rotation speed. In the control method, when slow acceleration is required and the deviation between the actual engine rotation speed and the target engine rotation speed is larger than a predetermined value, the speed ratio of the continuously variable transmission for a vehicle is maintained at a constant value. A control method for a continuously variable transmission for a vehicle, characterized by: