JPS6121461A - Controlling method of stepless transmission for vehicles - Google Patents

Abstract

PURPOSE:To prevent a belt slip from occurring without fail, by controlling a solenoid clutch, connecting a stepless transmission to an engine, so as to cause its torque transmission capacity to be smaller than that of the stepless transmission all the time. CONSTITUTION:In time of engine operation, first of all, engine torque TE is calculated on the basis of each output of a throttle valve opening sensor 16 and an engine speed sensor 17 at a control unit 15 and then torque transmission capacity TB in a stepless transmission 4 is set to be larger as mush as fixed value K1 than the said engine torque TE. A continuous rating value to a pressure control valve 12 is controlled so as to achieve this torque transmission capacity TB, and oil pressure of the specified pressure is led into each of hydraulic chambers 20 and 21, forcibly pressing a belt 10 in between. And at this time, torque transmission capacity TC of a solenoid powder type clutch unit 3 is set to be smaller as much as a fixed value K2 than the torque transmission capacity TB of the transmission 4, whereby a clutch current based on the setting value is constituted so as to be impressed on this clutch unit 3.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control method for a continuously variable transmission for a vehicle, and particularly relates to a control method for a continuously variable transmission for a vehicle.
The present invention relates to a control method for preventing slip in a continuously variable transmission for a vehicle that utilizes belt transmission.

[Prior art]

Continuously variable transmissions for vehicles that utilize V-belt transmission allow you to freely select the gear ratio within a specified range, making it possible to not only use the engine's capacity effectively but also drive with the lowest fuel efficiency. It is something to do.

However, there are problems with the durability of the belt, which is a transmission medium, and under certain running conditions, the belt is overloaded and slips. Methods to prevent this are to constantly maintain the hydraulic pressure that pinches the belt at a high pressure, or to temporarily supply high-pressure oil in anticipation of belt overload, but both methods are completely preventive. It has not become.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and its object is to provide a control method for a continuously variable transmission for a vehicle in which belt slip does not occur under any driving conditions.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

Reference numeral 1 is an engine, and 3 is an electromagnetic powder clutch unit, which is connected to the engine 1 through an input shaft 2. The output shaft of the clutch unit 3 is fixed integrally with the input shaft 5 of the continuously variable transmission 14. The continuously variable transmission 4 consists of a pair of input-side V-groove pulleys 6, 7, a pair of output-side V-groove pulleys 8, 9, and an endless belt 10 wound around the input and output pulleys. Input side ■Groove pulley 6
is fixed integrally with the input shaft 5, and the other input side V-groove pulley 7 is mounted so as to be slidable in the axial direction on the rotation axis of the input side V-groove pulley 6. A hydraulic chamber 20 for sliding the input V-groove pulley 7 in the axial direction is formed on the side of the input-side V-groove pulley 7 opposite to the part around which the endless belt 10 is wound. The pressure oil used controls the diameter of the input pulley defined by the input V-groove pulley 6.7. One output side ■groove boo 98 is connected to a drive wheel (not shown), and the other output side V groove pulley 9 is mounted on the rotating shaft of the output side V groove pulley 8 so as to be slidable in the axial direction. There is. A hydraulic chamber 21 for sliding the output V-groove pulley 9 in the axial direction is formed on the opposite side of the output side V-groove pulley 9 from the part around which the endless belt 10 is wound.
The output side V-groove pulley 8,
The size of the output pulley diameter defined by 9 is controlled. That is, by controlling the pressure oil flowing into the hydraulic chamber 20.21, the pulley diameters of the input pulley and the output pulley are adjusted, and as a result, the gear ratio e (e - manual pulley rotation speed N1N/output pulley rotation speed N) is freely selected. The pressure oil flowing into each hydraulic chamber 20°UT 21 is controlled by a flow control valve 11 and a pressure control valve 1.
2. 13 is a hydraulic pump, and 14 is a tank. Throttle opening sensor 16 for engine 1
and an engine rotation speed sensor 17 are provided on the input pulley of the continuously variable transmission 4, and an input pulley rotation speed sensor 18 for sensing the rotation speed of the input pulley and an output for sensing the rotation speed of the output pulley on the output pulley. A pulley rotation speed sensor 19 is provided respectively. Each of the above sensors is connected to a control device 15 consisting of a microcomputer, and the control device @15 controls the electromagnetic powder complete clutch unit 3 and the flow control valve 1 based on the signals from the respective sensors.
1 and the pressure control valve 12 are generated.

Next, the control method will be explained according to the flowchart shown in FIG.

In step 101, the engine throttle opening θTH is read from the throttle opening sensor 16. The read throttle opening degree θ, □ is input to the control device 15, and in step 102 θTH-〇 is determined. If the throttle opening degree is O, the rotation speed of the output valve 98 corresponding to the vehicle speed is outputted in step 103. Read from pulley rotation speed sensor 19.

Loaded output pulley rotation speed N. ol is the control device 15
In step 104, a predetermined constant value N1 is compared in magnitude, and if it is smaller than the constant value N1, the clutch current IC for magnetizing the powder in the clutch unit 3 is cut off. That is, the clutch unit 3 is in a released state. The constant value N1 is an experimentally determined value that is used to prevent the engine from stalling by releasing the clutch unit 3 when the throttle opening is zero and the vehicle speed is below a low constant value.

Next, the conditions for connecting the clutch unit 3 are step 1.
02, it is determined that the throttle opening θTH is not zero, or even if the throttle opening θTH is zero, the vehicle speed, that is, the output pulley rotation speed N. When the U work is above the predetermined value N1JX, the engine speed NF is read by the engine speed sensor 17 in step 106, and the engine speed NF is read in step 107.
Input 1 rotates together with the output shaft of clutch unit 3.
- Rotation speed NIN of pulley 6 is measured by rotary coupler rotation speed sensor 18.
Load it with In step 108, the slip amount N, -N1Ne of the clutch unit 3, which is the difference between the two, is calculated and compared with a predetermined upper limit value N2 of the slip amount. When the slip amount of the clutch unit is smaller than the upper limit value N2, in step 110, feedback control is performed using the time differential value 1c dl of the clutch currents i and c as a function of the slip amount until the slip amount becomes zero. If the slip amount of ~ is equal to or larger than the upper limit value N2, in step 109 the slip amount N = N is set to the upper limit value N
Set to 2. In other words, the time differential value dt of the latch current ic is the step 11.
At 0, it becomes a constant value and is fed back, and similarly, feedback control is performed until the slip amount becomes zero. The reason why the slip INE-N1N is set to the upper limit value N2 is that there is an upper limit to the time differential value of the clutch current. Furthermore, the reason why the time differential value of the clutch current is determined in step 110 is that the clutch connection must be performed smoothly and quickly.If the amount of slip is large and quick connection is required, the amount of increase in the clutch current is increased. This is to reduce the amount of increase in current as the amount of slip decreases. Here K is a constant.

When the connection of the clutch l-3 is completed by the above control, the slip amount of the clutch unit 3 becomes zero, and then the flow rate control of pressure oil that controls the gear ratio of the continuously variable transmission 4 is performed.
The pressure of the pressure oil is controlled to control the squeezing force of the belt 10, which determines the torque transmission ability of the speed change 814.

Next, flow control will be explained.

From the throttle opening degree θTH read in step 101, in step 201 a target engine speed N' corresponding to the throttle opening degree is calculated. Ni is calculated from FIG. 3, which shows the target engine speed at each throttle opening when a continuously variable transmission is used. The difference between the engine speed N read in step 106 and the target engine speed NL is calculated, and [If this difference is within the setting range ±No, the gear ratio e is not changed. When the target engine speed NC is higher than the engine speed N, the input pulley diameter is made smaller in order to increase N, that is, the current 'F is increased in step 204 to remove pressure oil from the hydraulic chamber 20.
1 is set and supplied to the flow rate control valve 11.

When the target engine speed N' is smaller than the engine speed NE, in order to reduce NE, the input pulley diameter is increased, that is, the current IF2 is set in step 203 so that pressure oil flows into the hydraulic chamber 20. and is supplied to the flow rate control valve 11. The flow rate control valve 11 has a current 'F' when releasing pressure oil.
It is necessary to control the current i when the pressure oil and pressure oil flow in, and the relationship between the oil flow rate and the currents 'Fl and 'F2 is shown in FIG. As is clear from FIG. 4, the flow rate control valve 11
The relationship 1 between the control current 1.1,' F2 and the flow rate is linear, making it easy to control the flow rate to determine the gear ratio e.

Simultaneously with the above-described flow rate control, pressure control for squeezing the belt 10 is performed. In step 301, the engine torque T is calculated based on the engine performance curve shown in FIG. 5 from the throttle opening degrees θ and □ read in steps 101 and 106 and the engine rotational speed NE. In step 302, the torque transmission capacity of the continuously variable transmission is set to a constant value much larger than the engine torque TE.

T = T' +K (1) EI Next, in step 303, the belt transmission horsepower P of the transmission is measured, and in step 304, the rotation speed N of the output pulley is determined. Ul
is read, and the gear ratio, which is the ratio to the input pulley rotation speed N1N read in step 107, is calculated in step 305, and from this value and the values of the pulley diameter and the center distance of the input and output pulleys, etc., as shown in FIG. 8. For belt wrapping, angles θ1 and θ2 are calculated in step 306, and values such as transmitted horsepower, belt speed, and friction coefficient are added to calculate the belt thrust, which is the force that pinches the transmission belt 10, in step 307. In step 308, the required current i is determined from the line pressure P,-current diagram shown in FIG. A current i is supplied to the control valve 12. As a result, an appropriate pressure P is added to the oil pressure 20.21, and the belt 1
0 is compressed, and the torque transmission capacity T8 of the transmission becomes the value set in step 302. Therefore, the transmission 4 is always capable of transmitting torque by a constant value K than the engine torque T. The larger the value of 1 is set to this constant value, the lower the risk of belt slip in the transmission 4 becomes, but at the same time, the transmission efficiency between the input and output pulleys decreases. In order not to reduce the efficiency, the value of 1 may be reduced to a constant value, but belt slip may occur when the engine torque T or load suddenly changes. Therefore, in step 111, the torque transmission capacity To of the clutch unit 3 is set to a constant value 2 smaller than the torque transmission capacity of the transmission.

T = T - K (2) B2 From the set torque transmission capacity To of the clutch unit 3, the necessary latch current IC is determined from the torque-current characteristic diagram of the clutch shown in FIG. The current IC is supplied to the clutch unit 3 and the powder is magnetized. As a result, the torque transmission capacity of the clutch unit 3 becomes a constant value 2 smaller than the torque transmission capacity T8 of the clutch unit, as shown by equation (2). Here, the constant value 1 set in step 302 and the constant value 2 set in step 111 are set to have a relationship expressed by equation (3).

K1>K2...(3) As a result, the torque transmission capacity of the clutch unit 3 is always larger than the engine torque TE, and there is a gap between the engine torque TF, the torque transmission capacity TC of the clutch unit, and the torque transmission capacity T8 of the transmission. The relationship of equation (4) is established, and T > T > T (4) CE Even if the engine torque increases rapidly, the clutch unit will always slip, and the transmission belt will never slip.

By maintaining the above relationship of formula (4), belt slip can be reliably prevented without reducing the transmission efficiency of the pulley including the belt.

〔Effect of the invention〕

Provided is a control method for a continuously variable transmission in which the clutch unit always slips even when the driving force or load of the engine suddenly increases, and belt slip in the transmission does not occur, and the durability of the continuously variable transmission is improved. It becomes possible to drive with low fuel consumption.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the control method of a continuously variable transmission for vehicles according to the present invention, FIG. 2 is a flowchart thereof, FIG. 3 is a graph showing target engine speed at each throttle opening, and FIG. The figure is a graph showing the relationship between current and flow rate in the flow control valve, Figure 5 is the engine performance curve, Figure 6 is a graph showing the relationship between line pressure and current in the pressure control valve, and Figure 7 is the electromagnetic powder set clutch. A graph showing the relationship between torque and current in the unit and FIG. 8 are schematic diagrams for explaining the angle of belt winding between pulleys. DESCRIPTION OF SYMBOLS 1... Engine, 3... Clutch unit, 4... Continuously variable transmission, 11... Flow control valve, 12... Pressure control valve, 15... Control device.

Claims (3)

[Claims] (1) In a method of controlling a continuously variable transmission for a vehicle using belt transmission, the torque transmission capacity of an electromagnetic clutch unit connecting the continuously variable transmission and the engine is greater than the torque transmission capacity of the continuously variable transmission. Controlling the continuously variable transmission and the electromagnetic clutch unit by sensing an engine rotation speed, a throttle opening, an input pulley rotation speed, and an output pulley rotation speed of the continuously variable transmission so that the rotation speed is always small. A control method for a continuously variable transmission for a vehicle, characterized by: (2) In the control method according to claim 1, the torque transmission capacity of the continuously variable transmission is controlled by a clamping force that clamps the belt of the transmission, and the torque transmission capacity of the electromagnetic clutch unit A control method for a continuously variable transmission for a vehicle, in which the power is controlled by the powder magnetization force of the clutch unit. (3) In the control method according to claim 2, the powder magnetizing force of the clutch unit is controlled by a clutch control current supplied to the clutch, and when the vehicle starts, the time derivative of the current is controlled. A control method for a continuously variable transmission for a vehicle, the value of which is proportional to the difference between the input and output rotational speeds of the clutch.