JPH0417292B2 - - 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 of a vehicle, and particularly relates to a method for controlling a continuously variable transmission (hereinafter referred to as "CVT") used as a power transmission device of a vehicle, and particularly to a method for controlling a continuously variable transmission (hereinafter referred to as "CVT"). Concerning a control method.

[Conventional technology]

CVT has 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.

The transmission efficiency of CVT is transmission speed e〓 (speed at which speed ratio e is changed: value de/dt obtained by differentiating speed ratio e with time t)
It is generally known that the absolute value of |de/dt| is a linear decreasing function.

Therefore, if only the transmission efficiency of the CVT is considered, the smaller the shift speed e〓, the better.
If the shift speed e〓 is set too small, the response during sudden acceleration etc. will be poor, so conventionally, a constant shift speed e〓 was set to balance this.
was set.

Furthermore, this shift speed e〓 is constant regardless of the driving state of the vehicle, especially whether or not the driver is requesting deceleration, or whether the vehicle speed is high or not. was set to the value of

[Problem to be solved by the invention]

However, if the shifting speed e〓 is set constant regardless of the vehicle running condition,
Since the speed ratio e is changed at the same speed change speed e when engine braking is not required as much or when strong engine braking is required, the engine braking that is truly required by the driver is There was a problem in that it was not possible to generate exactly the amount needed.

An object of the present invention is to provide a vehicle that can generate engine braking precisely as much as the driver requires, thereby improving drivability and fuel consumption efficiency.
The objective is to provide a CVT control method.

[Means to solve the problem]

The present invention provides a method for controlling a continuously variable transmission for a vehicle in which a speed ratio can be changed steplessly, including a step of determining whether or not a driver requests deceleration;
The above method can be achieved by including a step of detecting the vehicle speed, and a step of setting the speed at which the speed ratio is changed to be faster as the vehicle speed is lower when it is determined that the driver requests deceleration. The purpose has been achieved.

[Effect]

In the present invention, when it is determined that the driver requests deceleration, the speed at which the speed ratio is changed is
I try to set it faster when the vehicle speed is lower.

In order to determine whether the driver is requesting deceleration, for example, it is necessary to check whether the throttle opening is fully closed or whether the throttle opening remains fully closed for a predetermined period of time or longer. It is sufficient to detect whether or not the foot brake is engaged, or whether a combination of these is established.

In a running state where deceleration is required, the speed ratio is generally changed in the direction of decreasing speed ratio (low gear direction). This is to obtain stronger engine braking and to prepare for re-acceleration.

In this case, in the present invention, when the vehicle speed is high, the shifting speed is set to be low, so the speed ratio shifts to the low gear side at a slow speed. As a result, the engine brake does not work as much, allowing the vehicle to drive with high fuel consumption efficiency. On the other hand, when the vehicle speed is low, the gear is shifted to the low gear side at a high speed, so stronger engine braking can be obtained.

That is, in general, engine braking is hardly effective when the speed ratio is high (in a high gear state), and becomes more effective as the speed ratio becomes lower (shifting to the low gear side). Therefore, the earlier the vehicle shifts to the low gear side, the earlier the stronger engine braking can be applied.

Furthermore, when the speed ratio is shifted to the low gear side, the engine rotational speed is further increased, so that engine braking occurs due to inertia torque when the engine rotational speed is increased. Since engine braking caused by this inertia torque is greater as the shift speed is faster, sufficient engine braking can be obtained more quickly and at lower vehicle speeds from this point of view as well.

〔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 and 6b are provided facing each other, one input side disk 6a is provided on the input shaft 5 so as to be movable in the axial direction, and the other input side disk 6b is fixed to the input shaft 5. ing. Further, a pair of output side disks 7a and 7b are also provided facing each other, with one output side disk 7a
is fixed to the output shaft 8, and the other output side disk 7
b 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 includes input side disks 6a, 6b and output side disks 7a, 7b.
It is hung between.

The opposing surfaces of the input side disks 6a, 6b and the opposing surfaces of the output side disks 7a, 7b are formed into tapered cross sections such that the distance between them increases as they proceed radially outward. The input and output side disks 6a, 6b,
The radius of engagement (effective diameter) of the belt 9 at 7a and 7b increases or decreases, and the speed ratio and transmission torque change.

The oil pump 14 sends oil sucked from the oil sump 15 to the pressure regulating valve 16. 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 a hydraulic cylinder of the output side disk 7b. The linear solenoid type flow control valve 19 increases the pressing force between the input side disks 6a, 6b to obtain a speed ratio (speed ratio e=rotational speed Nout of the output side disks 7a, 7b/input side disk 6).
Rotation speed Nin of a, 6b: However, when increasing Nin = engine rotation speed Ne), the input side disk 6
The flow cross-sectional area between the oil passage 20 and the oil passage 18 to the hydraulic cylinder a is increased, and the connection between the oil passage 20 and the drain 17 is cut off, and the input side disk 6a,
In order to reduce the speed ratio by reducing the pressing force between the oil passages 6b, the connection between the oil passages 18 and 20 is cut off, and the flow cross-sectional area between the oil passage 20 and the drain 17 is controlled. That is, the speed ratio e of the CVT 4 is controlled by controlling the flow rate of oil to the input side disk 6a.

The cylinder oil pressure of the output side disc 7b, that is, the line pressure, is controlled to the minimum oil pressure that can ensure torque transmission without the belt 9 slipping, and as a result, the pump 14
driving loss is suppressed.

Note that the cylinder oil pressure of the output side disk 7b≧the cylinder oil pressure of the input side disk 6a, but since the pressure receiving area of the cylinder piston is input side > output side, the effective diameter on the input side is forcibly changed by changing the flow rate (speed ratio change) is possible.

Rotation angle sensors 23 and 24 measure the rotational speed of the input side disk 6b and the output side disk 7a, respectively.
Detect Nin, Nout. The water temperature sensor 25 detects the temperature of the cooling water of the engine 1. The throttle opening sensor 26 detects the opening of an intake system throttle valve that is linked to the accelerator pedal 27. Shift position sensor 2
8 detects the range of the shift lever near the seat 29. The brake switch 30 detects depression of the foot brake pedal 31.

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 and 24, the shift position sensor 28, and the brake switch 30 are sent to the interface 35, and the analog outputs of the water temperature sensor 25 and throttle opening sensor 26 are sent to the A/D 36, and the output pulses of the D/A 37 are sent to the interface 35. Output is pressure regulating valve 1
6 and the flow rate control valve 19.

FIG. 3 is a control block diagram of the CVT4.
In block 44, from the throttle opening θ
CVT4 input side rotation speed Nin (=engine rotation speed
A target value Nin′ of Ne) is calculated. In CVT4, the required horsepower of the engine 1 is set as a function of the throttle opening θ, and the engine rotation speed Ne that achieves each required horsepower with the minimum fuel consumption is determined by the throttle opening θ at that time.
is determined as the target value Nin' of the input side rotational speed Nin at .

In block 46, the target speed ratio e' is increased or decreased by Δe until Nin reaches Nin'. However, the change amount Δe is a positive value, and the value is changed by a method described later. By changing the value of this change amount Δe, the shift speed e〓 is changed. The initial value of the target speed ratio e' is the actual speed ratio e, and if Nin<Nin', -Δe, Nin>
In the case of Nin′, +Δe is selected respectively.

In block 48, the operating amount of the flow control valve 19 is calculated from the deviation of the actual speed ratio e from the target speed ratio e'. This manipulated variable is sent to the flow control valve 19 via the flow control amplifier 50, and the speed ratio e of the CVT 4 is
is controlled.

The lock 52 calculates the shaft torque Te of the engine 1 from the input side rotational speed Nin and the throttle opening θ.

Block 54 calculates line pressure as a function of CVT 4 transmission torque. The transmission torque of CVT4 is the shaft torque Te of engine 1, the input side rotation speed
It is a function of Nin and output side rotational speed Nout.
The output of block 54 is sent to pressure regulating valve 16 via pressure regulating valve amplifier 56, and the line pressure of CVT 4 is controlled.

FIG. 4 is a flowchart for executing control according to the control block diagram of FIG.

The outline of the control is as already explained in FIG. The upper and lower limits of the target speed ratio e' are
emax and emin, the flow control valve voltage as the input voltage of the flow control valve 19 is K ₀ (e'-e) (however, K ₀ here is a constant), and the input voltage of the pressure control valve 16 is the control valve voltage. The pressure valve control voltage is g(Te, Nin,
Nout).

In steps 60, 62, and 64, the throttle opening θ, the input side rotation speed Nin, and the output side rotation speed Nout are
is read, and in step 66, the target input side rotational speed Nin' is calculated.

In step 68, Nin and Nin' are compared and Nin
= Nin', hold e' in step 70, and if Nin<Nin', hold e' in step 72.
e' is decreased by Δe, and if Nin>Nin', e' is increased by Δe in step 76. Step 7
Steps 3 and 74 limit the lower limit of e' to emin, and steps 78 and 80 limit the upper limit of e' to emax.
At step 82, the flow rate control voltage is calculated, at step 84, the engine shaft torque Te is calculated, and at step 86, the pressure regulating valve control voltage is calculated.

FIG. 5 is a flowchart of a routine for calculating the shift speed e, specifically the amount of change Δe in the speed ratio e used in block 46 of FIG. 3 and steps 72 and 76 of FIG.

To explain each step in FIG. 5 in detail, step 9
0, the idle contact switch included in the throttle opening sensor 26 (the switch that turns on when the throttle opening is fully closed) is activated for a predetermined time T or more.
It is determined whether the idle contact switch is continuously on or not, and if the idle contact switch is continuously on for a predetermined time T or more, it is determined that the driver is requesting deceleration, and the process proceeds to step 92. Otherwise, it is determined that there is no request for deceleration, and the process proceeds to step 100.

In step 92, the speed change subroutine A shown in FIG. 6 is executed. In step 94, it is determined whether the foot brake is on or off. If it is on, the process proceeds to step 96, and if it is off, the process proceeds to step 98. Note that when the foot brake is operating, it is defined as foot brake on, and when it is not operating, it is defined as foot brake off.

In steps 96, 98, and 100, Y·e〓, e〓, and A are respectively substituted for the shifting speed e〓. However, Y>1.

In subroutine A in FIG.
10, the vehicle speed V (=C・Nout), where C is a constant) is compared with a predetermined value V1, and if V≧V1, the process proceeds to step 118, and if V<V1, the process proceeds to step 112.
Proceed to.

In step 112, the vehicle speed V and a predetermined value V2 (however,
V2<V1), and if V≧V2, proceed to step 116; if V<V2, proceed to step 114.
Proceed to. In steps 114, 116, and 118, the shift speed e〓 is changed to c, b, and a (where c>b>
Set to a).

FIG. 7 shows the relationship between the vehicle speed V, the operating state of the foot brake, and the shift speed e in this routine. As a result, the higher the vehicle speed V, the smaller the shift speed e〓 is set, and when the foot brake is on, the shift speed e〓 is set to a larger value than when the foot brake is off. It operates strongly at low vehicle speeds and when the foot brake is on, and weakly at high vehicle speeds and when the foot brake is off, making it possible to generate good engine braking depending on the vehicle speed and the operating state of the foot brake.

Note that when it is determined that deceleration is not required, the shift speed e is set to a small value a.

FIG. 8 is a flowchart of another shift speed calculation routine.

In this calculation routine, the shift speed e〓 is defined as a continuous function f(V) of the vehicle speed V.

Step 12 instead of step 92 in FIG.
0,122 is executed. In step 120, V
and V1, and if V≧V1, step 10
If V≦V1, proceed to step 122;
In step 122, f(V) is substituted for the shift speed e.

FIG. 9 shows f(V) and y·f(V). By setting a continuous function, the value of the speed change e can be set more accurately.

With the above configuration, when it is determined that the driver is requesting deceleration, the lower the vehicle speed is, that is, the stronger the engine brake is required, the lower the shift speed e〓 becomes. We will be able to proceed. As a result, the speed ratio e can quickly reach a lower speed ratio, and in combination with the engine brake effect caused by the inertia torque generated at that time, a stronger engine brake can be applied quickly. become able to.

In addition, in this embodiment, the state of the foot brake is also taken into consideration, and when the foot brake is turned on, the shifting speed is further increased.
This makes it possible to generate engine braking that more accurately reflects the driver's intentions.

〔Effect of the invention〕

As explained above, according to the present invention, when the driver requests deceleration, the lower the vehicle speed, the faster the gear change speed is set. It is possible to secure engine braking, and when engine braking is not so required, the occurrence of engine braking can be suppressed as much as possible to improve fuel consumption efficiency, which is an excellent effect.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the entire CVT to which the present invention is applied, Figure 2 is a block diagram of the electronic control device, and Figure 3 is a block diagram of the electronic control device.
The figure is a CVT control block diagram, Figure 4 is a flowchart of a CVT control routine according to the control block diagram of Figure 3, Figure 5 is a flowchart of a shift speed calculation routine, and Figure 6 is a flowchart of a CVT control routine according to the control block diagram of Figure 3. FIG. 7 is a graph showing the relationship between vehicle speed, foot brake operating state, and gear shift speed in the routine of FIG. 5. FIG. 8 is a flow chart of another shift speed calculation routine. 9 is a graph showing the relationship between the vehicle speed, the operating state of the foot brake, and the gear shift speed in the routine of FIG. 8. 4...CVT, 19...Flow rate control valve, 24...Output side disk rotation speed sensor (vehicle speed sensor), 26...
Throttle opening sensor, 30...brake switch, 31...brake pedal, V...vehicle speed, e...speed ratio, Δe...speed ratio shift amount, e=...speed ratio change speed (shift speed).

Claims (1)

[Claims] 1. A control method for a continuously variable transmission for a vehicle configured to be able to change a speed ratio steplessly, comprising: a procedure for determining whether a driver requests deceleration; and detecting vehicle speed. and a step of setting the speed at which the speed ratio is changed to be faster when the vehicle speed is lower, when it is determined that the driver requests deceleration. Control method for gear transmission.