JP2738206B2 - Shift control method for automatic transmission for vehicle - Google Patents

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 a vehicular automatic transmission, and more particularly to a shift control method for detecting a bent downhill by fuzzy inference and switching to an optimum shift speed.

[0002]

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

FIG. 1 shows a shift map for detailing the above-mentioned situation in the normal shift control. In the figure, at an operating point A where the throttle valve opening is defined by θ1 and the vehicle speed is defined by V1, the second gear is set. Steps have been established. When the throttle valve opening is returned from θ1 to θ2 from this state, the shift position is switched from the second speed to the fourth speed at the operating point B. There is no problem with this shift shift on a flat road, but in mountainous areas, for example, on a downhill road surface, the vehicle speed increases from V1 to V2 of the operating point C with the fourth gear set at the operating point B unchanged. And braking force is required.
In such a case, in the conventional shift control, a foot brake is used, a select switch for inhibiting the 4th speed, which is an overdrive speed, is operated, or the shift lever is switched to the 2nd speed range or the L range by the select lever. It was going down and the engine brake was working.

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

[0005]

However, the conventional fuzzy shift control method has disadvantages such as a large number of rules and a complicated membership function shape. Need. Further, since the number of rules is large and the shape of the membership function is complicated, tuning is difficult, and therefore, there is a problem that it is difficult to expand to other models. Further, in order to obtain information such as engine torque information and steering angle information, a sensor must be specially added, resulting in a problem that the cost is increased. For example, in fuzzy shift control disclosed in Japanese Patent Application Laid-Open No. 3-92667, a sensor for detecting engine intake pipe pressure is added in addition to various sensors in order to obtain engine torque information.

In the fuzzy speed change control disclosed in Japanese Patent Application Laid-Open No. 2-261957, the road surface gradient is identified by using the acceleration of the vehicle as an input variable. In addition, there is a problem that it is not possible to determine the descending gradient even if the climbing gradient can be determined. The present invention has been made in order to solve such a problem, and it is possible to accurately determine a curved downhill road without adding a special sensor, and to automatically shift on such a curved downhill road. It is an object of the present invention to provide a shift control method for an automatic transmission for a vehicle, in which a downshift is performed to apply an engine brake.

[0007]

In order to achieve the above 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 a parameter representing the engine load during a first predetermined period before the detection time of
The jerk amount in the second predetermined period before the detection time point is calculated, and based on the calculated average value and jerk amount, the degree of fitness of a curved descending slope is fuzzy inferred. When it is determined that the vehicle is traveling on a curved downhill road, the shift position is switched to a lower gear position where engine braking is effective.

[0008]

According to the shift control method of the present invention, the degree of conformity of a curved downhill is fuzzy inferred based on 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 determine a downhill while excluding a flat road and an uphill road, and the jerk amount is used to determine a curved road. When the vehicle descends on a downhill with a constant gradient and the engine margin torque immediately before and during cornering of the downhill is considered, each engine margin torque can be expressed by the acceleration at that time, and the cornering resistance is calculated immediately before cornering. It can be seen that it is proportional to the difference in acceleration during cornering, ie, the jerk. The present invention has been made based on such knowledge, and it is possible to determine a curved downhill road from the average value of the throttle valve opening and the jerk amount.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail 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 denotes an internal combustion engine, and the output of the engine 1 is transmitted to driving 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 is, for example, a forward four-stage reverse 1
It is provided with a friction engagement element of a hydraulic clutch or a hydraulic brake for performing a shift operation by switching a shift speed and a 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.
Operate each clutch and brake independently of each other. Each solenoid valve is electrically connected to an output side of a controller (ECU) 40, which will be described later, and adjusts a working oil pressure supplied to the friction engagement element according to a drive signal from the ECU 40.

The ECU 40 has built-in storage devices such as a ROM and a 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 speed sensor (N
t sensor) 21, a No sensor 22 for detecting the number of revolutions of the transfer drive gear (not shown) (the number of revolutions of the output shaft of the gear transmission 3) No. As a value, a throttle valve opening sensor (θt sensor) 23 for detecting the valve opening θt of the throttle valve is electrically connected. Each of these sensors 21 to 23 outputs a detection signal to the ECU.
40. The ECU 40 determines the rotational speed No of the transfer drive gear detected by the No sensor 22.
, The vehicle speed and the jerk of the vehicle can be calculated.

When switching the shift position of the automatic transmission, the ECU 40 performs duty control of the above-described solenoid valve to engage or disengage a required friction engagement element. For example, when shifting up from the second gear to the third gear, the frictional engagement of the friction coupling element that established the second gear is released, and the friction coupling element that establishes the third gear is frictionally engaged. . The 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, a description will be given, with reference to FIGS. 3 and 4, of a shift control on a curved downhill performed by the ECU 40. FIG. 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, and makes a fuzzy inference whether or not the vehicle is traveling on the curved downhill. 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 operation amount あ る as a fuzzy input variable is calculated. Jerk ΔG
Are respectively calculated. In this specification, the second derivative of the vehicle speed V, that is, jerk, is represented by a symbol (V) ", and the one derivative of the vehicle speed V, that is, acceleration is represented by a symbol (V) '. Here, the throttle average operation amount Θ is calculated based on the following equation (A1).

Θ = (total throttle valve opening detected in the 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. Is stored in Average throttle operation amount 操作
Is calculated from the throttle valve opening detection value stored in the storage device, and the calculated value includes the throttle valve opening detection value detected in the current loop (time t), and the first value before the detection time. Means the average value of the detected values of the throttle valve opening during the predetermined period x.

On the other hand, the jerk ΔG is calculated based on the following equation (A2). ΔG = (sum of jerks detected in the past y seconds at time t) (A2) jerk (V) ”is actually calculated by ECU 40 as follows. First, the vehicle speed V is calculated from the rotational 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 aforementioned storage device. The acceleration (V) 'is calculated, and the acceleration (V)' is also stored in the storage device each time, and the jerk (V) "of the present time is calculated from the difference between the previous value and the current value of the acceleration (V) '. It is calculated and also stored in the storage device. The jerk amount ΔG calculated from the equation (A2) is calculated in the second predetermined period y before the detection time, including the jerk (V) ″ calculated in the current loop (time t). The sum of the squares of the jerk speeds.

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 may be set to the same value. .
The jerk amount ΔG may be calculated as the sum of the squares of the jerk calculated in the second predetermined period y as described above, but may be calculated as the sum of the squares calculated in the second predetermined period y. It can also be obtained as the sum of the absolute values of the speeds.

Next, the ECU 40 calculates the fitness Z of the curved downhill road from the fuzzy input variables Θ and ΔG obtained as described above.
o fuzzy inference. In general, there are various methods for fuzzy inference, such as "MIN-MAX centroid method", "algebraic product-addition-centroid method", and "simplification method". Any of these methods may be used to fuzzy infer the fitness Zo of a curved downhill from the fuzzy input variables Θ and ΔG. The method of inference will be described.

First, in step S12, the ECU 40 obtains grade values a, b, c, and d of each fuzzy input variable Θ and ΔG for each rule. FIG. 4 shows membership functions of the jerk amount ΔG and the average throttle operation amount Θ prepared for n (four) fuzzy rules, respectively. Grade values a to d corresponding to the jerk amount ΔG and the average throttle operation amount Θ calculated in this way are calculated. The degree hi (i = 1 to n) at which a real number Zi (i = 1 to n) is obtained as a 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),
The fitness Zo of the curved downhill is calculated (step S1).
4). The degree hi at which the real number Zi is obtained is obtained as the product of the grade values obtained from the membership function of the i-th rule. For example, the degree h1 of the rule 1 in which the real number Z1 is obtained is obtained as the product of the grade values a and b.
The degree h1 of the rule 2 is obtained as a 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) Zi can be set to an arbitrary 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 average throttle operation amount Θ is small, it is concluded that the fitness is large. According to Rule 2, if the jerk amount ΔG is large, If the average throttle operation amount Θ is also large, it is concluded that the fitness is small.

After calculating the fitness Zo in step S14, it is determined whether the calculated fitness Zo is greater than a predetermined value XZ (step S16). If the result of this determination is negative (No), it cannot be considered that the vehicle is traveling on a curved downhill, and the routine ends 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.

Here, how the curved downhill road is determined based on the jerk amount ΔG and the throttle average operation amount Θ will be described. Now, the vehicle descends downhill with a constant slope,
Assume a state where the vehicle turns a corner. Generally, the following equation (A) is provided between the vehicle acceleration (V) ′ and the engine margin torque.
It is known that 4) holds.

[0021]

(Equation 1)

The engine margin torque can be expressed by the following equation (A5). Engine excess torque = engine output-rolling resistance-cornering resistance-aerodynamic resistance-acceleration resistance ... (A5) In the above equations (A4) and (A5), assuming that the engine output, rolling resistance, aerodynamic resistance, and acceleration resistance are constant. The following equation (A6) holds between the acceleration (V) '0 immediately before the vehicle enters the corner and the acceleration (V)' 1 during cornering.

[0023]

(Equation 2)

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

On a downhill, the value of (V) '1 is smaller than the value of (V)' 0, and the value of ((V) '0-(V)' 1) becomes substantially (V) '0. Since it is equal, when trying to determine a downhill curved road focusing only on acceleration, it is always in an accelerating state just before cornering and during cornering, whether it is down a straight downhill or down a curved downhill. It is impossible to determine whether there is any. Therefore, it is possible to determine the curved downhill road only by the jerk.

The average throttle operation amount Θ is used for distinguishing traveling on an uphill road and traveling on a flat road from traveling on a downhill road and excluding 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 shift command may be output to switch the shift position to a position where the engine brake is effective and one lower than the current shift speed. It is determined whether or not. This determination is negative if, for example, a predetermined time (for example, one second) has not elapsed since the previous shift shift was executed, and the shift shift is prohibited.

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

[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 during the first predetermined period, and the jerk during the second predetermined period. Based on the amount of jerk, based on fuzzy inference of the degree of fitness of a curved downhill, when it is determined that the vehicle is running on a curved downhill by the fuzzy inference,
Since the shift position is switched to the lower gear position where the engine brake is effective, it is possible to accurately determine a curved downhill road, and to automatically execute a downshift on such a curved downhill road to perform engine braking. Can work. In addition, there is no need to add a special sensor for detecting engine torque information and steering angle information, so that the system can be manufactured at low cost. 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 type of engine, for example, the type of a carburetor-equipped engine, a so-called multipoint fuel injection valve-equipped engine, or a diesel engine. It is possible,
Since the number of input variables is small and a simple inference method can be used, the computation time of the computer is short, and its capacity is small.

[Brief description of the 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 a method according to the present invention is implemented.

FIG. 3 is a flowchart of a bent downhill road speed shift control routine executed by a controller 40 of FIG. 2;

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

[Explanation of symbols]

 DESCRIPTION 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)

(57) [Claims] 1. A parameter value representing an engine load and a jerk of a vehicle are detected, and an average value of the parameter representing the engine load during a first predetermined period before the detection time is calculated. Of the jerk in the second predetermined period of time, and based on the calculated average value and jerk, fuzzy inference is given to the degree of suitability of the curved downhill road, and the vehicle is turned down by the fuzzy inference. A shift control method for an automatic transmission for a vehicle, characterized in that when it is determined that the vehicle is traveling, the shift position is switched to a lower shift speed at which engine braking is effective.