JPS62286847A - Control for continuously variable transmission for vehicle - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a continuously variable transmission due to the abnormal temperature rise of working oil by changing the speed change ratio of the continuously variable transmission to the smaller value side when the working oil temperature is over a prescribed temperature or the cooling water temperature is over a prescribed value. CONSTITUTION:A continuously variable transmission 1 is equipped with a water temperature sensor 21 for detecting the cooling water temperature, oil temperature sensor 22 for detecting the working oil temperature, throttle position sensor 23, engine revolution speed sensor 24, car speed sensor 25, input side pulley revolution speed sensor 26, and an output side pulley revolution speed sensor 27 for detecting the revolution speed of an output side pulley 8. The signal supplied from each sensor is input into an electronic controller 30, and controls a CVT 4 by driving a pressure control valve 13 and a flow rate control valve 14.

Description

Detailed Description of the Invention 3. 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 used, for example, in an automobile.

[Prior Art] In recent years, vehicles such as automobiles have been known to be equipped with a continuously variable transmission that continuously changes the output of an internal combustion engine and transmits the output to drive wheels. The continuously variable transmission as described above can set its speed ratio according to the operating state. Therefore, compared to conventional automatic transmissions and the like, there is an advantage that power performance can be improved.

By the way, the above-mentioned continuously variable transmission is composed of, for example, an input pulley, an output pulley, and a transmission belt wound around both. Both of the above pulleys have a movable pulley fitted onto a rotating shaft that is integrated with the fixed pulley so as to be movable in the axial direction, allowing stepless speed change operation by changing the effective diameter at the position where the transmission belt is wound. Let's do it. Movement, lubrication, cooling, etc. of the movable pulley are performed by hydraulic oil that is pumped. Note that the hydraulic oil is cooled using cooling water for the internal combustion engine.

[Problems to be Solved by the Invention] However, in vehicles equipped with the above-mentioned continuously variable transmission, the internal combustion engine is often used in an operating state in a high output range. For example, when an internal combustion engine is operated for a long time in a region with high output and a high fuel consumption rate, the amount of heat generated increases. That is, the heat load on the cooling system increases, and the cooling water temperature also rises. For this reason, there is a problem in that the temperature of the hydraulic oil of the continuously variable transmission cooled by the cooling water increases, accelerating deterioration such as a decrease in the viscosity of the hydraulic oil.

Further, in conjunction with the above-mentioned problem, there has also been a problem that the lubrication performance and power transmission capacity of the continuously variable transmission are decreased.

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 is effective in preventing a rise in the temperature of hydraulic fluid in the continuously variable transmission.

[Means for Solving the Problems] The present invention, which has been made to solve the above problems, as illustrated in FIG. In the control method for a continuously variable transmission for a vehicle, when the temperature of the hydraulic oil of the continuously variable transmission exceeds a predetermined hydraulic oil temperature (
Sl), or when the temperature of the cooling water for cooling the internal combustion engine exceeds a predetermined cooling water temperature (S2), change the gear ratio of the continuously variable transmission to a smaller side (S3). The gist of this paper is a characteristic control method for a continuously variable transmission for a vehicle.

Here, the predetermined hydraulic oil temperature and predetermined cooling water temperature are determined according to the temperature of the hydraulic oil or cooling water in a state where a large heat load is applied to the cooling system due to an increase in the amount of heat generated by the internal combustion engine, for example. It is.

Note that the above-mentioned control circuit can be realized by, for example, a discrete logic circuit. Alternatively, for example, a logic operation circuit including a well-known CPLJ, ROM, RAM, and other peripheral circuit elements may be implemented by executing a predetermined processing procedure.

[Function] As illustrated in FIG. 1, the method for controlling a continuously variable transmission for a vehicle according to the present invention is performed when the hydraulic oil temperature of the continuously variable transmission is equal to or higher than a predetermined hydraulic oil temperature (Sl), or when the cooling water temperature is When the coolant temperature is equal to or higher than a predetermined temperature (S2), the gear ratio of the continuously variable transmission is changed to a smaller one (S3).

That is, when the heat load on the cooling system is large, by changing the gear ratio to a smaller side and lowering the rotational speed of the internal combustion engine, a shift is made to an operating state in which the driving force is equal and the amount of heat generated is smaller.

Therefore, in the control method for a continuously variable transmission for a vehicle according to the present invention, when the temperature of the hydraulic oil or cooling water exceeds a predetermined value,
It works to lower the above-mentioned temperature without causing large fluctuations in the driving force. The technical problems of the present invention are solved by the effects of the present invention as described above.

[Embodiment] Next, a preferred embodiment 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 to which the method of the present invention is applied.

A continuously variable transmission device 1 for a vehicle transmits the driving force of an engine 2 to a continuously variable transmission (hereinafter simply referred to as a CVT!2) via a fluid coupling 3.
4. The driving force input to the CVT 4 is transmitted to the input shaft 5. Input side pulley 6, belt 7, output side boo 98. It is transmitted in order of the output shaft 9. The input pulley 6 and the output pulley 8 each include a hydraulic chamber 10.11. The volume of the pressure chambers 10.11 on both sides is changed by the hydraulic oil supplied from the reservoir 12 through the pressure control valve 13 and the flow control valve 14, and one end side of the two boobies 96, 8 is axially Sliding. Therefore, the effective diameter of the winding position of the belt 7 changes, allowing stepless speed change operation.

Above fluid coupling 3. CVT4 hydraulic oil is oil cooler 15
After being cooled down, it is refluxed to the reservoir 12 again. on the other hand,
After the cooling water for the engine 2 is air-cooled by the radiator 1 - 6 , the hydraulic oil is cooled by the oil cooler 15 , and then circulated through the cooling system of the engine 2 again to cool the engine 2 .

The continuously variable transmission @1 includes, as detectors, a water temperature sensor 212 that detects the cooling water temperature and an oil temperature sensor 2 that detects the hydraulic oil temperature.
2. A throttle position sensor 23 that detects the throttle valve opening of the engine 2, a rotation speed sensor 24 that detects the rotation speed of the engine 2. Vehicle speed sensor 25 for detecting vehicle speed. An input pulley rotation speed sensor 26 that detects the rotation speed of the input pulley 6. An output side pulley rotation speed sensor 27 is provided to detect the rotation speed of the output side pulley 8.

The signals from each of the above sensors are controlled by an electronic control unit (hereinafter simply EC).
The ECtJ 30 drives the pressure control valve 13 and the flow rate control valve 14 to control the CVT 4.

ECU3O includes a CPU30a and a ROM30b.

It is configured as a logic operation circuit centering on 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 repeatedly executed at predetermined time intervals.

First, in step 100, a process is performed in which the water temperature sensor 21 detects the cooling water temperature TW, and the oil temperature sensor 22 detects the oil temperature TL. In the following step 110, the cooling water temperature T
It is determined whether W exceeds the allowable cooling water temperature TWS or whether the oil temperature TL exceeds the allowable oil temperature TLS. If the determination is affirmative, the process proceeds to step 120, whereas if the determination is negative, it is assumed that the speed change for cooling is not necessary, and the present speed change control process is temporarily terminated.

Step 1 executed when gear shifting is required for cooling
At 20, processing for detecting the operating state of the engine 2 is performed. That is, the engine rotation speed, vehicle speed, throttle valve opening, and gear ratio of the CVT 4 are detected. In subsequent step 130, a process is performed to calculate the amount of heat generated by the engine 2 and CVT 4 based on the operating state detected in step 120. Next, in step 140, the heat dissipation capacity of the radiator 16 is calculated from the cooling water flow rate and cooling air velocity in the operating state detected in step 120, and the heat dissipation capacity of the oil cooler 15 from the hydraulic oil flow 1 from the CVT 4 to the oil cooler 15. Processing to calculate is performed. In the following step 15.0, the calorific value of the engine 2 and CVT 4 calculated in step 130 above is equal to the sum of the amount of heat radiated into the air and the heat radiation capacity of the radiator 16 and oil cooler 15 calculated in step 140 above. Based on the thermal equilibrium equation, the radiator 16
Population, oil cooler 15 population, and each cooling water temperature at the oil cooler 15 outlet T1. T2. T3 and oil cooler 15
Population, each oil temperature at the oil cooler 15 outlet T4. A process for calculating T5 is performed. Note that the calculated value in step 150 is confirmed by comparison with the detected value in step 100 above.

Next, the process proceeds to step 160, and each cooling water temperature T1. calculated in step 150 above. T2. T3 and each oil temperature T4
．． A process is performed to calculate, based on the map, the operating state of the engine 2 in which the temperature T5 can be lowered below each permissible temperature determined correspondingly. That is, according to the map shown in Fig. 4, the current operating state (indicated by point a in the figure) is changed in the six directions of arrows along the equal horsepower line (indicated by the dashed line in the figure), and the fuel An operating state (shown as a dot in the figure) in which the consumption rate (equal fuel consumption rate line is shown as a solid line in the figure) is small and the amount of heat generated is small is determined. In this operating state, the engine speed decreases from the value Ne1 to the value Ne2, while the engine torque increases from the value Tel to the value Te2.

Next, the process proceeds to step 170, where a process is performed to calculate the gear ratio of the CVT 4 based on the map.

That is, according to the map shown in FIG. 5, a gear ratio that can maintain the same vehicle speed even in the operating state of the engine 2 shut off in step 160 is determined. In the current driving state, vehicle speed vO, engine rotation speed Ne1. Since the throttle valve opening degree is θ1, the speed ratio is set to a large value r1 (indicated by point C in the figure). In this case, in the operating state where the amount of heat generated is low as calculated in step 160 described above, the engine rotational speed decreases to Ne2, so
The gear ratio that can maintain the same vehicle speed is determined to be a small value r2. Note that this gear ratio r2 is determined when the driving state is vehicle speed vO1 engine rotation speed Ne2. This value is determined based on the prediction that the throttle valve opening degree will shift to θ2 (indicated by point d in the figure).

In the subsequent step 180, the pressure control valve 13 is adjusted so that the gear ratio of the CVT 4 becomes the value calculated in the above step 170.
．． After the flow rate control valve 14 is driven and controlled to decrease the gear ratio, the present gear change control process is temporarily terminated.

This shift control process is repeatedly executed every time the above-described execution conditions are satisfied. In addition, as the gear ratio changes from a large value r1 to a small value r2, the driver increases the throttle valve opening degree from 01 to 02 in order to maintain the vehicle speed at vO. Therefore, the operating state of the engine 2 shifts to the operating state calculated in step 160 described above.

As explained above, in this embodiment, when at least one of the cooling water temperature and the oil temperature exceeds the allowable temperature,
The engine 2 is configured to change the gear ratio of the CVT 4 to a smaller value to shift the engine 2 to an operating state that generates less heat. Therefore, without reducing the driving performance of the vehicle,
Cooling water temperature and hydraulic oil temperature can be lowered to below permissible temperatures.

Therefore, deterioration such as a decrease in the viscosity of the hydraulic oil of the CVT 4 can be prevented, and the shift performance of the CVT 4 can be compensated for a long period of time.

Further, the shift control process of this embodiment is a process performed in an emergency when the cooling water temperature or oil temperature exceeds an allowable temperature, so it is rarely activated during normal driving. Therefore, there is no adverse effect during normal driving.

In this embodiment, both the cooling water temperature and the oil temperature are detected and used to determine whether to start control. However, for example, it may be configured to detect only either the cooling water temperature or the oil temperature to make the determination.

Further, in this embodiment, only control is performed to change the gear ratio of the CVT 4 to a small value. However, for example, in a vehicle equipped with an actuator that changes the throttle valve opening, the speed ratio may be changed to a small value, and the throttle valve opening may be changed greatly. With this configuration, the engine can be reliably shifted to an operating state with less heat generation while maintaining the driving force and running performance constant at all times.

Although the embodiments of the present invention have been described above, the present invention is not equally limited to these embodiments, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

Effects of the Invention As detailed above, the method for controlling a continuously variable transmission for a vehicle of the present invention allows continuously variable transmission to be performed when the hydraulic oil temperature is above a predetermined hydraulic oil temperature or when the cooling water temperature is above a predetermined cooling water temperature. It is configured to change the gear ratio of the machine to the smaller side. For this reason, when the temperature of the hydraulic oil or cooling water exceeds a predetermined value, the operating state of the internal combustion engine is shifted to a dormant state with less heat generation, thereby preventing deterioration due to abnormal temperature rises in the hydraulic fluid of the continuously variable transmission. This has the excellent effect of preventing the above and improving the durability of the continuously variable transmission.

Moreover, along with the above effects, the lubrication performance and power transmission capacity of the continuously variable transmission are compensated, and its reliability is also improved.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram illustrating the contents of the present invention, Fig. 2 is a system configuration diagram of an embodiment of the present invention, Fig. 3 is a flow chart showing its control, and Fig. 4 is the operation of the engine. FIG. 5 is a graph showing a map of the state, and a graph showing a map of the speed change state of the continuously variable transmission. 1... Continuously variable transmission for vehicle 2... Engine 4... Continuously variable transmission (CVT) 21... Water temperature sensor 22... Oil temperature sensor

Claims (1)

[Claims] 1. In a control method for a continuously variable transmission for a vehicle that continuously changes the output of an internal combustion engine and transmits it to drive wheels, when the temperature of the hydraulic oil of the continuously variable transmission exceeds a predetermined hydraulic oil temperature, or A control method for a continuously variable transmission for a vehicle, characterized in that when the temperature of the cooling water for cooling the internal combustion engine exceeds a predetermined cooling water temperature, the gear ratio of the continuously variable transmission is changed to a smaller side.