JPH0719337A - Creep-torque control device for automatic transmission - Google Patents

Abstract

PURPOSE:To prevent retreat of a vehicle on an upgrade slope, excessive creep- torque at the time of idle-up, etc., by controlling speed change gears in response to the grade of a road surface, engine speed, etc., and making it possible to control the speed change gears to creep-torque permitting the vehicle to stop or advance at extremely slow speed always in any condition. CONSTITUTION:Respective output signals from an engine speed sensor 12, a speed sensor 13, a grade sensor 14, and an oil temperature sensor 15 are inputted to the A/T controller 20 of an automatic transmission which provides command signals to solenoids 21 to 24 provided in a hydraulic control device 6 to control the engaging state of a clutch and a brake, and to establish specified speed change gears. Loss torque FL is determined from the map data indicating the relationship between AT oil temperature and the loss torque, necessary torque FN is determined from the map data indicating the relationship between the grade of a road and the necassary loss, and output torque FO is determined from the map data indicating the relationship between engine speed and the output torque of a torque converter. Then, a gear ratio K1 is calculated fron the formula K1=FN/(FO-FL) in order speed change control to be carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling the creep torque of an automatic transmission equipped with a torque converter.

[0002]

2. Description of the Related Art In the case of an automatic transmission equipped with a torque converter, when the shift lever is in the driving range (D, L, R), the creep phenomenon in which the vehicle travels at a very low speed is inevitable without depressing the accelerator pedal. . In order to eliminate such a creep phenomenon, conventionally, a technique has been proposed in which the creep torque is reduced by selecting the gear stage having the minimum gear ratio instead of the maximum gear ratio when the vehicle is stopped in the travel range. However, the method as described above has a drawback that the creep torque cannot be used when the vehicle is held in a stopped state on an uphill road or driven at a very low speed on a congested road.

[0003]

[Patent Document 1] Japanese Unexamined Patent Publication No. 61-
As disclosed in Japanese Patent No. 146646, a creep condition is controlled according to the vehicle stop condition by detecting a vehicle stop condition according to a road gradient, an engine idle speed, an inter-vehicle distance, and the like, and selecting a gear stage from the vehicle stop condition. What to do is proposed.

[0004] However, the factors of variation of the creep torque include the gradient of the road surface, the engine speed, the inter-vehicle distance, and the oil temperature change of the automatic transmission. In particular, when the oil temperature is low, not only the drag torque of the clutch increases, but also the agitation resistance due to gears increases, which greatly affects the creep torque. Therefore, it is an object of the present invention to provide a creep torque control device for an automatic transmission, which can be controlled to an optimum creep torque according to the engine speed, the road surface gradient and the oil temperature of the automatic transmission.

[0005]

In order to achieve the above object, the present invention provides an automatic transmission equipped with a torque converter, which has a torque required to bring a vehicle into a stopped state or a slow speed advancing state in accordance with a gradient of a road surface. Required torque estimating means for estimating the output torque, output torque detecting means for detecting the output torque of the torque converter corresponding to the engine speed, loss torque estimating means for estimating the loss torque according to the oil temperature of the automatic transmission, and the gear A gear shift control means is provided for controlling the gear stage to have a ratio closest to a value obtained by dividing the required torque by the difference between the output torque and the loss torque.

[0006]

Operation: First, the gradient of the road surface is detected, and the required torque F for bringing the vehicle into a stopped state or a slow speed advancing state from this gradient is obtained.
Estimate _N. Further, since the output torque of the torque converter fluctuates according to the engine speed during idling, the output torque F _O according to the engine speed is detected. Furthermore, the loss torque F _L according to the oil temperature of the automatic transmission
To estimate. The required torque F _N , output torque F _O, and loss torque F _L are preset as map data. The torque values F _N , F _O , F obtained in this way
_The gear ratio K _i is calculated from _L based on the following equation.

[0007]

[Equation 1] When the gear is shifted to the gear having the gear ratio closest to the gear ratio K _i , the vehicle is in a stopped state under any conditions such as optimum creep torque, that is, warm-up, stopping on an uphill road, idling up, etc. Alternatively, it can be controlled to a slightly advanced state.

[0008]

1 is a system diagram of a power transmission system having a creep torque control device according to the present invention. Engine 1
Is transmitted to the speed change mechanism 4 via the torque converter 3 of the automatic transmission 2, and the speed change mechanism 4 is connected to wheels (not shown). The automatic transmission 2 includes an oil pump 5 driven by a torque converter 3, and the oil discharged from the oil pump 5 is sent to a hydraulic control device 6. The hydraulic control device 6 controls the hydraulic pressure of various friction elements such as a shift clutch and a brake built in the speed change mechanism 4 according to the vehicle speed and the throttle opening.

Reference numeral 10 is a range sensor for detecting a range switched by a shift lever, 11 is a throttle sensor for detecting a throttle opening of the engine 1, 12 is an engine speed sensor for detecting an engine speed, and 13 is an output shaft rotation. A vehicle speed sensor that detects the speed (vehicle speed), 14 is a gradient sensor that detects the gradient of the road surface, and 15 is an oil temperature sensor that detects the AT oil temperature. The signals of these sensors 10 to 15 are input to the A / T controller 20. The A / T controller 20 is a computer that compares and arithmetically processes an input signal and setting data according to a predetermined program to perform line pressure control, lockup control, gear shift control and creep torque control. A command signal is output to the solenoids 21 to 24 provided in the device 6. Of these, 21 is a line pressure control solenoid, 22
Are lock-up solenoids, and 23 and 24 are shift control solenoids, and each hydraulic pressure is linearly adjusted according to a duty control signal input to each solenoid 21-24.

The A / T controller 20 has map data indicating the relationship between the AT oil temperature and the loss torque (see FIG. 2).
And map data showing the relationship between the road surface gradient and the torque required to bring the vehicle into a slow forward state (see FIG. 3), and map data showing the relationship between the engine speed and the output torque of the torque converter 3 (see FIG. 4) and are set. According to this, when the AT oil temperature is low, the drag torque and the stirring resistance of the clutch are large, so that the loss torque _FL
It is large, and decreases the loss torque F _L as the temperature rises,
Loss torque F _L if equal to or higher than the predetermined temperature is substantially constant. Further, as the gradient of the road surface increases, the rearward attractive force applied to the vehicle increases, so that the required torque F _N increases sinusoidally. The required torque F _N is not limited to the case where the vehicle is allowed to move at a slight speed even on an uphill road.
The torque may be set such that the stopped state is always maintained. Further, the output torque F _O of the torque converter is determined by the engine performance curve and the performance of the torque converter, and increases as the engine speed increases.

The A / T controller 20 determines the loss torque F _L and the required torque F obtained from the above map data.
_{From the N} and the output torque F _{O, the} gear ratio K _{i is} calculated by the equation (1).
Is calculated, and the speed is changed to the gear having the gear ratio closest to the gear ratio K _i . As a result, the vehicle can be controlled to the slow speed advancing state under any conditions such as the oil temperature, the gradient of the road surface, and the idle up. The gear having the gear ratio closest to the gear ratio K _i may be the first gear having the maximum gear ratio or may be other gears.

Next, a specific method for controlling the creep torque according to the present invention will be described with reference to FIG. First, range, throttle opening, engine speed,
Various signals such as vehicle speed, road surface gradient, AT oil temperature, etc. are read (step 40) to determine whether the vehicle is in the running range, is idling (throttle fully closed), or is the vehicle almost stopped (the vehicle speed is, for example, 5 km / h). The following is determined (steps 41 to 43). In the case of a and less than a predetermined value vehicle speed idling in the running range, the subsequently calculated torque loss F _L from AT oil temperature (step 44) to obtain the required torque F _N from the gradient (step 45), further the engine speed Then, the output torque F _O of the torque converter is obtained from (step 46). Next, the gear ratio K _i is calculated by the equation (1) (step 47), and the shift control solenoids 23 and 2 are arranged so that the shift stage has the gear ratio closest to this gear ratio.
4 is controlled (step 48). As described above, the creep torque is controlled to the optimum value so that the vehicle always travels at a slow speed under any condition. Therefore, it is possible to solve problems such as a decrease in creep torque when cold, a vehicle retreating on an uphill road, and an excessive creep torque when idling up, and the vehicle can be controlled with light braking.

In the above-described embodiment, the creep torque is controlled so that the vehicle always moves at a slight forward speed under any condition, but the creep torque may be controlled so that the vehicle is always stopped. However, it is more convenient to move the vehicle forward at a slight speed when entering the garage or in a traffic jam, so the above control is performed.

[0014]

As is apparent from the above description, according to the present invention, the gear position is controlled according to the gradient of the road surface, the engine speed and the oil temperature, and it is always stopped or at a slight speed under any condition. Since the creep torque is controlled so that it will move forward, problems such as lower creep torque during cold, vehicle retreat on uphill roads, excessive creep torque during idle up can be solved, and the advantages of automatic transmission can be maximized. .

[Brief description of drawings]

FIG. 1 is a system diagram of a power transmission system including a creep torque control device according to the present invention.

FIG. 2 is a diagram showing a relationship between AT oil temperature and loss torque.

FIG. 3 is a diagram showing a relationship between a road gradient and a required torque.

FIG. 4 is a diagram showing a relationship between engine speed and output torque.

FIG. 5 is a flowchart showing an example of the creep torque control method of the present invention.

[Explanation of symbols]

 1 Engine 2 Automatic Transmission 11 Throttle Sensor 12 Engine Speed Sensor 13 Vehicle Speed Sensor 14 Gradient Sensor 15 Oil Temperature Sensor 20 A / T Controller

Claims (1)

[Claims] 1. An automatic transmission equipped with a torque converter, comprising: a required torque estimating means for estimating a required torque for bringing a vehicle into a stopped state or a slow speed advancing state in accordance with a gradient of a road surface; An output torque detecting means for detecting the output torque of the torque converter, a loss torque estimating means for estimating a loss torque according to the oil temperature of the automatic transmission, and a gear ratio which gives the above required torque as a difference between the output torque and the loss torque. A creep torque control device for an automatic transmission, comprising: a shift control means for controlling a shift stage closest to a value divided by.