JPS632745A - Continously variable transmission control vehicle - Google Patents

Abstract

PURPOSE:To make a correction suitably against an reduction in driving force of an internal combustion engine by correcting a gear change ratio in such a way as to become greater depending on the difference between intake air density and a predetermined value when intake air density is equal to or less than a predetermined value. CONSTITUTION:A continuously variable transmission 1 includes as a detector, a throttle position sensor 21, a revolving speed sensor 22, a vehicle speed sensor 23, an input shaft revolving speed sensor 24, an output shaft revolving speed sensor 25, an atmospheric temperature sensor 26, an atmospheric pressure sensor 27, and a pattern setting switch 28. Signals from these sensors and the switches are inputted into an ECU 30 for driving a pressure regulating valve 14 and a flow control valve 15 so as to control the continuously variable transmission 1. And a ratio is corrected by the ECU 30 in such a way as to become greater depending on the difference between intake air density and a predetermined value when intake air density is equal to or less than a predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to a control method for a continuously variable transmission for a vehicle that is effective against changes in environmental conditions.

[Prior Art] Conventionally, as a control method for a continuously variable transmission installed in an automobile, etc., for example, the rotational speed of its input shaft is determined based on the throttle valve opening of an internal combustion engine and the speed of the vehicle. 2. Description of the Related Art There is a known technique for steplessly controlling a gear ratio so as to achieve a target rotational speed. Such speed ratio control has been performed on the premise that the internal combustion engine is constantly operated in an operating state that outputs a desired driving force at a minimum fuel consumption rate.

However, since internal combustion engines cannot output sufficient driving force during cold fetal movements, for example, controlling the gear ratio as described above may make it impossible for the vehicle to run smoothly. . As a countermeasure for such problems, "Speed change control method for V-belt type continuously variable transmission" (Japanese Unexamined Patent Publication No. 58-1
80865) etc. have been proposed. That is, when the engine cooling water temperature is low, the technology increases the gear ratio compared to the normal case.

[Problems to be Solved by the Invention] In general, the driving force output by an internal combustion engine changes depending on the driving environment of the vehicle, not only during cold start. For example, when driving for a long time in an area with high atmospheric temperature,
Alternatively, when the vehicle is traveling on a mountainous road at a high altitude where atmospheric pressure is low, the driving force output by the internal combustion engine also decreases due to the decrease in intake air density.

However, the conventional technology has a problem in that it does not take into consideration the case where the driving environment changes as described above.

Further, when the driving force output from the internal combustion engine is reduced due to the above-mentioned reasons, the driver counteracts this by increasing the amount by which the accelerator pedal is depressed. However, even if the driver performs a driving operation to output more driving force than normal, it is not reflected in the driving condition of the vehicle, so there is a problem in that the driver feels strange about the drivability.

Furthermore, in a vehicle equipped with a so-called power pattern that gives priority to the output of sufficient driving force as a control characteristic of the gear ratio, and a so-called economy pattern that keeps fuel consumption rate and noise to a minimum, the above-mentioned In such a case, it may be possible to switch to a power pattern, for example. However, when the power pattern is selected, there is a problem in that the reduction in driving force of the internal combustion engine due to changes in the driving environment is excessively compensated for, resulting in a worsening of the fuel consumption rate and an increase in noise.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method for a continuously variable transmission for a vehicle that suitably corrects a reduction in driving force of an internal combustion engine caused by changes in the driving environment.

Structure of the Invention [Means for Solving the Problems] The present invention, which has been made to solve the above problems, as illustrated in FIG. In a control method for a continuously variable transmission for a vehicle, the gear ratio is controlled so that the rotational speed of the input shaft of the continuously variable transmission for a vehicle is at least a target rotational speed calculated based on the required output amount of the internal combustion engine. , when it is determined that the intake air density of the internal combustion engine is less than or equal to a predetermined value (Sl), the gear ratio of the small dual-purpose continuously variable transmission is further adjusted according to the difference between the predetermined I revision and the intake air density. The gist of this article is a control method for a continuously variable transmission for a vehicle, which is characterized in that the correction is made to the larger side (S2).

Continuously variable transmissions for vehicles are, for example, so-called belt-type transmissions that are equipped with a pair of movable pulleys that rotate in the axial direction and realize stepless speed changes by changing the effective diameter of a belt wrapped between both movable pulleys. It can be configured with a continuously variable transmission. Alternatively, for example, a bearing-type continuously variable transmission using bearings may be used.

The required output ω of the internal combustion engine may be, for example, various quantities such as the throttle valve opening or the accelerator operation (2) of the internal combustion engine.

Determining that the intake air density is less than or equal to a predetermined value may be determined to correspond to the above condition, for example, when the atmospheric temperature exceeds a predetermined temperature. Alternatively, for example, it may be determined that the above condition is met when the atmospheric pressure is below a predetermined pressure.

Depending on the difference between the predetermined value and the intake air density, the speed ratio may be corrected to a larger value, for example, to the extent that the atmospheric temperature becomes higher than the predetermined temperature. Alternatively, for example, the speed ratio may be corrected to a larger value as the atmospheric pressure becomes lower than a predetermined pressure.

The above-described control can be realized by, for example, a discrete logic circuit. Alternatively, for example, a logic operation circuit configured with a well-known CPU, ROM, RAM, and other peripheral circuit elements may be implemented by executing a predetermined processing procedure.

[Operation] As illustrated in FIG. 1, the method for controlling a continuously variable transmission for a vehicle according to the present invention is such that the rotational speed of the input shaft of the continuously variable transmission for a vehicle is
When controlling the gear ratio so as to achieve the target rotational speed calculated based on at least the required output no.jm of the internal combustion engine, when the intake air density is less than a predetermined value (Sl), the difference between the intake air density and the predetermined value is Accordingly, the speed change ratio is corrected to a larger side (S2).

That is, the decrease in driving force due to a decrease in the charging efficiency of the internal combustion engine is compensated for by increasing the gear ratio of the continuously variable transmission for a vehicle.

Therefore, the control method for a continuously variable transmission for a vehicle according to the present invention is such that even if the driving environment of the vehicle changes, the driving force is increased by increasing the gear ratio to realize smooth running of the vehicle. work. The technical problems of the present invention are solved by the effects of the present invention as described above.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings. FIG. 2 shows a system configuration of a continuously variable transmission for a vehicle, which is a first embodiment to which the method of the present invention is applied.

The continuously variable transmission device 1 for a vehicle is configured to transmit driving force output from an engine 2 to a continuously variable transmission (hereinafter simply referred to as CVT) 4 via a fluid coupling 3. The driving force input to the CVT 4 is input to the input 11115, the input pulley 6,
Belt 7, output pulley 8 and output! It is transmitted in the order of P[l19. The input pulley 6 and the output pulley 8 each include hydraulic chambers 10 and 11. Both sleeve pressure chambers 10.11
is pumped from the reservoir 12 by the hydraulic pump 13,
The volume is changed by the hydraulic oil supplied through the pressure control valve 14 and the flow rate control valve 15, and the movable pulleys at one end of the pulleys 6.8 slide in their axial directions. Therefore, the effective diameter of the winding position of the belt 7 changes, allowing stepless speed change operation. Note that the driving force is transmitted from the output shaft 9 of the CVT 4 to the drive wheels via a reduction gear and a differential gear (not shown).

The continuously variable transmission device 1 for a vehicle includes, as detectors, a throttle position sensor 21 that detects the throttle valve opening of the engine 2, a rotation speed sensor 22 that detects the rotation speed of the engine 2, a vehicle speed sensor 23 that detects the vehicle speed, and an input. Axis 5
an input shaft rotation speed sensor 24 that detects the rotation speed of the output shaft 9; an output shaft rotation speed sensor 25 that detects the rotation speed of the output shaft 9;
It is provided with an atmospheric temperature sensor 26 for detecting atmospheric temperature, an atmospheric pressure sensor 27 for detecting atmospheric pressure, and a pattern setting switch 28 for selecting either an economy pattern or a power pattern.

Signals from each of the above sensors and switches are input to an electronic control unit (hereinafter simply referred to as ECU).
3O drives the pressure control valve 14 and flow rate control valve 15 to control the continuously variable transmission device 1 for a vehicle.

ECU3O includes a CPU30a and a ROM30b.

It is configured as a logic operation circuit centering around the RAM 30c, and is connected to an input section 30e and an output section 30f via a common bus 30d to perform input/output with the outside.

Next, the speed change control process executed by the ECU 3O will be explained based on the flowchart of FIG. 3.

This shift control process is activated when the vehicle starts, and is repeatedly executed at predetermined time intervals.

First, in step 100, a process is performed in which the vehicle speed, throttle valve opening, input shaft rotation speed, output shaft rotation speed, setting pattern, and atmospheric temperature T are inputted from the sensors and switches described above.

In the following step 110, it is determined whether or not the set pattern is an economy pattern.
80 respectively. In step 120, which is executed when the economy pattern is selected, the speed ratio γE of the economy pattern is calculated according to the map. That is, a target rotational speed in an operating state of the engine 2 that achieves a predetermined driving force with a minimum fuel sludge rate is determined based on the vehicle speed and the throttle valve opening.

Next, a gear ratio T[ that makes the input shaft rotational speed of the CVT 4 the target rotational speed is calculated. Next, the process proceeds to step 130, where it is determined whether or not the atmospheric temperature T exceeds the predetermined temperature TO. If the judgment is affirmative, the process proceeds to step 140, and if the judgment is negative, the process proceeds to step 170. Step 140 executed when the atmospheric temperature T exceeds the predetermined temperature]°O
Then, a process is performed to calculate the temperature deviation 8 as shown in the following equation (1).

εT=T-To (1) In the following step 150, a process is performed to calculate a correction coefficient α based on the eight temperature deviations calculated in step 140 above. Here, as shown in FIG. 4, the correction coefficient α increases from the value 1.0 as the temperature deviation increases.

The ECU 30 stores a map as shown in FIG. 4 in the ROM 30b in advance, and adjusts the correction coefficient α according to the map.
Calculate. Note that the correction coefficient α may be calculated using an arithmetic expression corresponding to the above map. Next, the process proceeds to step 160, and the gear ratio γE calculated in step 120 is calculated using the correction coefficient α calculated in step 150 as shown in the following equation (2).
A correction process is performed as shown below.

γ=αXγE (2) In the subsequent step 170, after a speed change process is performed to drive the pressure control valve 14 and the flow rate control valve 15 so that the speed ratio of the CVT 4 becomes the value calculated in the current process. ,-The main shift control process ends.

- On the other hand, in step 130 above, the atmospheric temperature is set to the predetermined temperature TO.
If it is determined that the gear ratio γ is less than or equal to
After the speed change process for realizing E is performed, the main speed change control process ends.

If it is determined in step 110 that the power pattern has been selected, the process proceeds to step 180, where the speed ratio γP of the power pattern is calculated according to the map, and then the main speed change control process is performed once through step 170 described above. end. Thereafter, this shift control process is repeatedly executed as described above.

As explained above, in the first embodiment, when the economy pattern is set and the atmospheric temperature T exceeds the predetermined temperature To, the gear ratio is corrected to a larger value using the correction coefficient α determined according to the temperature deviation 8. is configured to do so. Therefore, even if the driving force decreases due to a decrease in the charging efficiency of the engine 2 when continuously driving in a high-temperature area, it is possible to prevent a decrease in the vehicle's power performance, allowing smooth driving according to the driver's operations. realizable.

In addition, since the gear ratio when setting the economy pattern is corrected according to the temperature deviation between the actual atmospheric temperature T and the predetermined temperature To, excessive correction of the gear ratio can be prevented and the fuel consumption rate can be reduced. It is possible to maintain the temperature and reduce noise generation.

Next, a second embodiment of the present invention will be described based on the drawings. The difference between the first and second embodiments is that in the first embodiment, the gear ratio is corrected to a larger value when the atmospheric temperature exceeds a predetermined temperature, whereas in the second embodiment, the gear ratio is corrected to a larger value when the atmospheric temperature exceeds a predetermined temperature. The point is that the gear ratio is corrected to a larger value when the pressure becomes less than a predetermined pressure. The system configuration of the second embodiment is the same as that of the first embodiment described above, and therefore a description thereof will be omitted.

Next, the speed change control process in the second embodiment will be explained based on the flowchart of FIG. First, input the vehicle speed, throttle valve opening, input shaft rotation speed, output shaft rotation speed, setting pattern, and atmospheric pressure.Step 2o-o>,,;
A p-constant pattern is determined (step 210). When setting the power pattern, the speed ratio of the power pattern is calculated (step 280), and speed change processing is performed based on the speed ratio (step 270).

On the other hand, when setting the economy pattern, the speed ratio γE of the economy pattern is calculated (step 220). Next, it is determined whether the atmospheric pressure pa is less than or equal to a predetermined pressure PaO (step 230). As soon as the atmospheric pressure pa exceeds the predetermined pressure PaO, the gear shifting process is performed (step 27).
0). When the atmospheric pressure Pa is less than a predetermined pressure (a), the pressure deviation εP is calculated as shown in the following equation (3) (
step 240).

εP=PaO-Pa - (3) Next, according to the pressure B difference εP, a correction coefficient β is calculated according to the map shown in FIG. 6 (step 250).
. Note that the correction coefficient β may be calculated according to an arithmetic expression. Furthermore, the speed ratio γE of the economy pattern calculated in the above step 220 is corrected as shown in the following equation (4) using the correction coefficient β calculated in the above step 250 (step 260
).

T=βXTE (4) Next, after a speed change process is performed to set the speed ratio of the CVT4 to the value calculated in the current process (step 270),
- End the amount water speed change control process. Thereafter, this shift control process is repeatedly executed at predetermined time intervals.

As explained above, in the second embodiment, when the economy pattern is set and the atmospheric pressure Pa is lower than the predetermined pressure PaO, the gear ratio is set to a large value by the correction coefficient β determined according to the pressure deviation εP. It is configured to compensate for Therefore, when driving on highlands with low atmospheric pressure such as mountain roads, so-called altitude guarantee is achieved by correcting the gear ratio, which prevents the vehicle's driving performance from deteriorating even if the driving force output from the engine 2 decreases. can.

Further, since the speed ratio at the time of setting the economy pattern is corrected according to the pressure deviation εP between the actual atmospheric pressure pa and the predetermined pressure PaO, it is possible to prevent harmful effects caused by excessive correction.

Although several embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can be implemented in various ways without departing from the gist of the present invention. Of course.

Effects of the Invention As detailed above, the method for controlling a continuously variable transmission for a vehicle according to the present invention, when the intake air density is less than a predetermined value, increases the gear ratio according to the difference between the intake air density and the predetermined value. It is configured to correct the side. Therefore, even if the driving force output from the internal combustion engine decreases due to a decrease in intake air density due to changes in the vehicle's driving environment, the reduction in driving force is compensated for by increasing the gear ratio to ensure smooth running. It has an excellent effect of guaranteeing performance.

Furthermore, since the decrease in driving force is corrected by increasing the gear ratio as described above, the driver does not feel any discomfort during operation.

Roughly speaking, since the gear ratio is largely corrected according to the difference between the intake air density and the predetermined value, excessive correction can be prevented, and fuel consumption rate can be improved and noise can be reduced.

For example, configuring the vehicle to determine that the intake air density is below a predetermined value when the atmospheric temperature is higher than a predetermined temperature is effective when driving for a long time in an area with high atmospheric temperature.

For example, if the configuration is such that when the atmospheric pressure is lower than a predetermined pressure, it is determined that the intake air density is less than a predetermined value,
This makes it possible to provide so-called altitude protection when driving on mountain roads.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram illustrating the contents of the present invention, Fig. 2 is a system configuration diagram of the first embodiment of the invention, Fig. 3 is a flow chart showing its control, and Fig. 4 is its correction coefficient. FIG. 5 is a flowchart showing the control of the second embodiment of the present invention, and FIG. 6 is a graph showing a map of the correction coefficients. 1...Continuously variable transmission for vehicle 2...Engine 4...Continuously variable transmission (CVT) 21...Throttle position sensor 26...Atmospheric temperature sensor 27...Atmospheric pressure sensor 130 ...Electronic control unit (ECU) 30a ・CPU

Claims (1)

[Scope of Claims] 1. The rotational speed of the input shaft of a continuously variable transmission for a vehicle that continuously changes the output of the internal combustion engine and transmits it to the drive wheels is calculated based on at least the required output amount of the internal combustion engine. In a control method for a continuously variable transmission for a vehicle that controls a gear ratio to achieve a target rotational speed, when it is determined that the intake air density of the internal combustion engine is less than or equal to a predetermined value, the predetermined value and the intake air density are A control method for a continuously variable transmission for a vehicle, characterized in that the gear ratio of the continuously variable transmission for a vehicle is corrected to a larger side in accordance with the difference between the two. 2. The control method for a continuously variable transmission for a vehicle according to claim 1, wherein the intake air density is determined to be less than or equal to a predetermined value when the atmospheric temperature is higher than a predetermined temperature. 3. The control method for a continuously variable transmission for a vehicle according to claim 1, wherein the intake air density is determined to be below a predetermined value when atmospheric pressure is lower than a predetermined pressure.