JPH05280624A - Speed change control method of automatic transmission for vehicle - Google Patents

Abstract

PURPOSE:To apply an engine brake by automatically executing a shift down on a curved descending road such as accurately decided without adding a particu lar sensor. CONSTITUTION:A parameter value representing an engine load and acceleration of a vehicle are detected to calculate a mean value of a parameter THETA representing an engine load in the first predetermined period before the point of time of these detection and a derivative of acceleration quantity DELTAG in the second predetermined period before the point of time of detection.(S10) Based on the calculated mean value and acceleration quantity, a fuzzy inference (S12, S14) of conformity to serve as a curved descending road is performed, and when the vehicle is decided in running on the curved descending road (S16) by this fuzzy inference, a speed change position is switched to a speed change shift in a low speed side where an engine brake is effective. (S20)

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control method for an automatic transmission for a vehicle, and more particularly to a shift control method for detecting a curved downhill road by fuzzy reasoning and switching to an optimum shift stage.

[0002]

2. Description of the Related Art In a conventional automatic transmission for a vehicle, a shift pattern is set in advance according to a throttle opening (engine load) and a vehicle speed, and the throttle opening and the vehicle speed detected by using this shift pattern are set. The gear shift stage is set in accordance with and the shift shift is automatically executed. This conventional automatic gear shift control method (normal gear shift control method) has no particular problem in gear shift on a flat road such as city driving, and the gear shift is smooth and comfortable. However, according to the conventional normal gear shift control method, when traveling on a mountain downhill or the like, a situation may occur in which the optimum gear stage according to the road condition is not set.

FIG. 1 shows a shift map for explaining the above-mentioned situation in the normal shift control in detail. At the operating point A defined by the throttle valve opening θ1 and the vehicle speed V1 in the figure, the second speed is set. Dan is established. When the throttle valve opening is returned from θ1 to θ2 from this state, the gear position at the operating point B is switched from the second gear to the fourth gear. On a flat road, there is no problem with this shift shift, but in the mountains, for example, on a road surface with a downward slope, the vehicle speed increases from V1 to V2 at the operating point C at the fourth speed set at the operating point B. However, braking force is required.
In such a case, in the conventional shift control, a foot brake is used, a select switch for prohibiting the 4th speed, which is an overdrive speed, is operated, or a select lever is used to switch to the 2nd speed range or the L range to shift. I tried to bring it down and apply the engine brake.

As described above, according to the conventional normal shift control method, it is not always possible to set the optimum shift speed on a mountain road or the like. Therefore, control is performed to automatically determine the road condition and switch the shift speed to the optimum shift speed. As a method, so-called fuzzy shift control based on engine torque information, steering angle information, etc. has been proposed.

[0005]

However, the conventional fuzzy shift control method has drawbacks in that the number of rules is large and the shape of the membership function is complicated. Therefore, a computer having a large capacity for practical use is required. Need. Further, since there are many rules and the shape of the membership function is complicated, there is a problem that tuning is difficult and, therefore, expansion to other models is also difficult. Further, in order to obtain information such as engine torque information and steering angle information, it is necessary to add a special sensor, which causes a problem of cost increase. For example, in the fuzzy shift control disclosed in Japanese Patent Laid-Open No. 3-92667, a sensor for detecting the engine intake pipe pressure is added in addition to various sensors in order to obtain engine torque information.

In the fuzzy shift control disclosed in Japanese Patent Laid-Open No. 2-261957, the acceleration of the vehicle is used as an input variable to identify the road gradient, but according to the shift control method disclosed in this publication, However, there is a problem in that it is not possible to discriminate the downhill slope even if the uphill slope can be discriminated. The present invention has been made to solve such a problem, and it is possible to accurately determine a curved downhill road without adding a special sensor, and automatically shift on such a curved downhill road. An object of the present invention is to provide a shift control method for an automatic transmission for a vehicle, which is designed to perform down and to apply engine braking.

[0007]

In order to achieve such an object, a shift control method for an automatic transmission for a vehicle according to the present invention detects a parameter value representing an engine load and a jerk of the vehicle, An average value of parameters representing the engine load in a first predetermined period before the detection time of
A jerk amount in a second predetermined period before the detection time point is calculated, and based on the calculated average value and jerk amount, a goodness of fit, which is a curved downhill road, is fuzzy inferred. When it is determined that the vehicle is traveling on a curved downhill road, the shift position is switched to a low-speed gear position where engine braking is effective.

[0008]

In the shift control method of the present invention, the degree of suitability as a curved downhill road is fuzzy inferred on the basis of a parameter representing the engine load, for example, the average value of the throttle valve opening and the jerk. The average value of the throttle valve opening is used to exclude a flat road and an uphill road and determine a downhill, and the jerk is used to determine a curved road. Considering the engine margin torque just before and during cornering on a downhill with a constant slope, each engine margin torque can be expressed by the acceleration at that time, and the cornering resistance is measured immediately before cornering. It can be seen that the difference is proportional to the acceleration difference during cornering, that is, the jerk. The present invention has been made based on such knowledge, and it is possible to determine the curved downhill road from the average value of the throttle valve opening and the jerk.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 shows a schematic configuration of an automatic transmission of an automobile that implements the shift control method according to the present invention. Reference numeral 1 in the figure indicates an internal combustion engine, and the output of the engine 1 is transmitted to drive wheels (not shown) via an automatic transmission 2. The automatic transmission 2 includes a torque converter 4, a gear transmission 3, a hydraulic circuit 5, a controller 40 and the like. The gear transmission 3 has, for example, four forward gears and one reverse gear.
It is provided with a gear shift stage and a friction engagement element of a hydraulic clutch or a hydraulic brake that performs a shift operation by switching the shift position. The hydraulic circuit 5 has a duty solenoid valve (hereinafter simply referred to as a solenoid valve) corresponding to each of the friction engagement elements described above, and each friction engagement element, that is,
Operate each clutch and brake independently of each other. Each solenoid valve is electrically connected to the output side of a controller (ECU) 40, which will be described later, and adjusts the hydraulic pressure supplied to the friction engagement element by a drive signal from the ECU 40.

The ECU 40 has a built-in storage device such as ROM and RAM, a central processing unit, an input / output device, a counter (all not shown) and the like. On the input side of the ECU 40, various sensors, for example, a turbine rotation speed sensor (N which detects the rotation speed Nt of the turbine of the torque converter 4).
t sensor) 21, a No sensor 22 for detecting a rotational speed No (not shown) of a transfer drive gear (the rotational speed of the output shaft of the gear transmission 3), a parameter which is arranged in the intake passage of the engine 1 and which represents an engine load. As a value, a throttle valve opening sensor (θt sensor) 23 or the like for detecting the valve opening θt of the throttle valve is electrically connected. Each of these sensors 21 to 23 sends a detection signal to the ECU.
Supply to 40. The ECU 40 determines that the transfer drive gear rotation speed No. detected by the No sensor 22.
Based on, the vehicle speed and the vehicle jerk can be calculated.

When switching the shift position of the automatic transmission, the ECU 40 duty-controls the solenoid valve to engage or disengage a desired friction engagement element. For example, when shifting up from the second gear to the third gear, the frictional engagement of the frictional coupling element that has established the second gear is released, and the frictional coupling element that establishes the third gear is frictionally engaged. .. Control of engagement or disengagement of the friction engagement element at this time is not particularly limited in the method of the present invention, and various known control methods can be adopted.

Next, the shift control of the curved downhill road executed by the ECU 40 will be described with reference to FIGS. 3 and 4. The ECU 40 repeatedly executes the shift control routine shown in FIG. 3 at a predetermined cycle in order to execute the shift control on the curved downhill road, and fuzzy infers whether the vehicle is traveling on the curved downhill road. More specifically, the ECU 40
First, in step S10, from the throttle valve opening θt detected by the throttle valve opening sensor 23 and the jerk (V) ″ detected by the No sensor 22, the throttle average manipulated variable Θ, which is a fuzzy input variable, Jerk rate ΔG
Are calculated respectively. In this specification, the second derivative of the vehicle speed V, that is, the jerk is represented by the symbol (V) ", and the first derivative of the vehicle speed V, that is, the acceleration is represented by the symbol (V) '. Here, the average throttle operation amount Θ is calculated based on the following equation (A1).

Θ = (sum of throttle valve opening detected in past x seconds at time t) / (time constant) (A1) The throttle valve opening θt is detected at a predetermined cycle, and these are stored in the storage device. Remembered in. Throttle average operation amount Θ
Is calculated from the throttle valve opening detection value stored in the storage device, and the calculation value includes the throttle valve opening detection value detected at this time loop (time t) Means the average value of the throttle valve opening detection values in the predetermined period x.

On the other hand, the jerk amount ΔG is calculated based on the following equation (A2). ΔG = (sum of squares of jerk detected in past y seconds at time t) (A2) jerk (V) ”is actually calculated by the ECU 40 as follows. First, the vehicle speed V is calculated from the rotation speed No of the transfer drive gear detected by the No sensor 22, and the vehicle speed V calculated each time is stored in the above-mentioned storage device. The acceleration (V) 'is calculated, and the acceleration (V)' is also stored in the storage device each time, and the current jerk (V) "is calculated from the deviation between the previous value and the current value of the acceleration (V) '. It is calculated and is also stored in the storage device. The jerk amount ΔG calculated from the equation (A2), including the jerk (V) ″ calculated in the current loop (time t), is calculated in the second predetermined period y before this detection time. It is the sum of each square of jerk.

The above-mentioned predetermined periods x and y may be set to appropriate values for each vehicle type, and these values may be set to different values or the same value. ..
The jerk amount ΔG may be calculated as the sum of the squares of the jerks calculated in the second predetermined period y as described above, but the jerk calculated in the second predetermined period y may be calculated. It can also be obtained as the sum of absolute values of speeds.

Next, the ECU 40 uses the fuzzy input variables Θ and ΔG obtained as described above to determine the suitability Z of the curved downhill road.
fuzzy reasoning o. Generally, there are various methods for fuzzy inference, and "MIN-MAX centroid method", "algebraic product-addition-centroid method", "simplification method" and the like are known. Any of these methods may be used as a method for fuzzy inferring the fitness Zo of a curved downhill from the fuzzy input variables Θ and ΔG of the present invention. However, the following is a simplified method for fuzzy determination of the fitness Zo of a curved downhill. Explain how to reason.

First, in step S12, the ECU 40 obtains the grade values a, b, c, d of the fuzzy input variables Θ and ΔG for each rule. FIG. 4 shows the membership functions of the jerk amount ΔG and the throttle average manipulated variable Θ prepared for each of the n (four) fuzzy rules. From each membership function, as described above, Then, the grade values a to d corresponding to the jerk amount ΔG and the throttle average manipulated variable Θ calculated as above are calculated. Then, the degree hi (i = 1 to 1) that the real number Zi (i = 1 to n) is obtained as the conclusion of each rule from the obtained grade values a to d
n) is obtained, and from the obtained degree hi, based on the following equation (A3),
Calculate the fitness Zo of the curved downhill road (step S1)
4). The degree hi of obtaining the real number Zi is obtained as a product of grade values obtained from the membership function of the i-th rule. For example, the degree h1 of obtaining the real number Z1 in Rule 1 is obtained as the product value of the grade values a and b,
The degree h1 of rule 2 is obtained as the product value of the grade values a and c.

Zo = (Z ₁ h ₁ ＋ Z ₂ h ₂ ＋ Z ₃ h ₃ ＋ …… ＋ Z _n h _n ) ÷ (h ₁ ＋ h ₂ ＋ h ₃ ＋ …… ＋＋ h _n ) …… (A3) Where, a real number Zi can be set to any value. For example, the real number Z1 of rule 1 is set to the value 1 and the real number Z2 of rule 2 is set to the value (-1). And rule 1
Then, if the jerk amount ΔG is large and the throttle average operation amount Θ is small, it is concluded that the conformity is large, and in Rule 2, if the jerk amount ΔG is large. If the average throttle operation amount Θ is also large, it is concluded that the degree of conformity is small.

When the goodness of fit Zo is calculated in step S14, it is determined whether or not the calculated goodness of fit Zo is larger than a predetermined value XZ (step S16). When the result of this determination is negative (No), it cannot be considered that the vehicle is traveling on a curved downhill road, and the routine is ended without doing anything. On the other hand, if the determination result of step S16 is affirmative (Yes), it is determined that the vehicle is traveling on a curved downhill road.

Now, how the curved downhill road is determined by the jerk amount ΔG and the throttle average operation amount Θ will be described. Now the vehicle is going down a downhill slope
Assume the situation when turning a corner. Generally, between the vehicle acceleration (V) 'and the engine margin torque, the following equation (A
It is known that 4) holds.

[0021]

[Equation 1]

The engine surplus torque can be expressed by the following equation (A5). Engine margin torque = Engine output-Rolling resistance-Corning resistance-Aerodynamic resistance-Acceleration resistance (A5) Assuming that the engine output, rolling resistance, aerodynamic resistance, and acceleration resistance are constant in the above formulas (A4) and (A5). , The following equation (A6) is established between the acceleration (V) '0 immediately before the vehicle enters the corner and the acceleration (V)' 1 during cornering.

[0023]

[Equation 2]

As is clear from the above equation (A6), the cornering resistance is proportional to ((V) '0- (V)' 1), that is, the amount of change in acceleration (jerk). Therefore, when the jerk exceeds a predetermined determination value, it can be determined that the vehicle is traveling on a curved road. In reality, when the jerk amount ΔG, which is the sum of the squares of the jerks detected in the predetermined period y, exceeds a predetermined determination value, it is determined that the vehicle is traveling on a curved road.

On the downhill, the value of (V) '1 is smaller than the value of (V)' 0, and the value of ((V) '0- (V)' 1) becomes approximately (V) '0. Since it will be the same, if you try to distinguish the downhill curved road by focusing only on the acceleration, you will always be in an accelerating state both before and during cornering, and whether you are going down a straight downhill or going down a curved downhill. You will not be able to determine if you are there. Therefore, the curved downhill road can be discriminated only by the jerk.

The average throttle operation amount Θ is used for distinguishing traveling on an uphill road and a flat road from traveling on a downhill road and eliminating them. Returning to the flowchart of FIG. 3, when the bent downhill road is determined in step S16, the process proceeds to step S18, and a gear shift command for switching the gear shift position to a gear position lower than the current gear position by the engine braking may be output. It is determined whether or not. This determination is negative, for example, unless a predetermined time (for example, 1 second) has elapsed since the previous shift shift was executed, and the shift shift is prohibited.

If the result of the determination in step S18 is affirmative, the process proceeds to step S20, in which the ECU 40 outputs a gear shift command signal to the hydraulic circuit 5 to set the gear position to the next lower gear for which engine braking is effective, for example, the current gear position. The gear position is 4
If it is the first speed, it is switched to the third speed, and if it is the third speed, it is switched to the second speed. The above-described shift control on a curved downhill road may be executed in combination with a conventionally known normal shift control, or may be executed by incorporating it into a fuzzy shift control that determines all shift speeds by fuzzy inference. May be.

[0028]

As described above, according to the method of the present invention, the parameter representing the engine load, for example, the average value of the throttle valve opening in the first predetermined period and the jerk in the second predetermined period. On the basis of the jerk and the amount of jerk, fuzzy inference is performed on the fitness that is a curved downhill road, and when it is determined that the vehicle is traveling on the curved downhill road by the fuzzy inference,
Since the shift position is switched to the low speed side where the engine brake works, it is possible to accurately determine a bent downhill road, and automatically perform downshifting on such a bent downhill road to perform engine braking. Can be used. Moreover, since it is not necessary to add a special sensor for detecting the engine torque information and the steering angle information, the system can be made inexpensive. Further, since only the throttle valve opening is used as the engine information, the shift control method of the present invention is applied regardless of the engine type, for example, carburetor-equipped engine, so-called multi-point fuel injection valve-equipped engine, diesel engine, or the like. It is possible,
Since the number of input variables is small and a simple inference method is sufficient, the calculation time of the computer is short and its capacity is small.

[Brief description of drawings]

FIG. 1 is a graph showing a shift pattern defined by a throttle valve opening and a vehicle speed, for explaining a problem to be solved by the present invention.

FIG. 2 is a schematic configuration diagram of an automatic transmission for a vehicle in which the method according to the present invention is implemented.

3 is a flowchart of a bend downhill road shift control routine executed by the controller 40 of FIG. 2. FIG.

FIG. 4 is a graph showing a membership function for fuzzy inference in the shift control of the present invention.

[Explanation of symbols]

 1 Engine 2 Automatic Transmission 3 Gear Transmission 5 Hydraulic Circuit 22 Transfer Drive Gear Rotation Speed Sensor 23 Throttle Valve Opening Sensor 40 Controller

Claims (1)

[Claims] 1. A parameter value representing an engine load and a jerk of a vehicle are detected, and an average value of the parameters representing the engine load in a first predetermined period before the detection time point and an average value before the detection time point are detected. And a jerk in a second predetermined period of time are calculated. Based on the calculated average value and the jerk, the degree of conformity which is a curved downhill road is fuzzy inferred, and the vehicle is bent downhill by the fuzzy inference. When determining that the vehicle is traveling, a shift control method for an automatic transmission for a vehicle, characterized in that the shift position is switched to a low-speed gear position where engine braking is effective.