JP2757448B2 - Vehicle speed change control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a shift control device for a vehicle equipped with an automatic transmission, and more particularly to a shift control device for a vehicle intended to provide an engine braking effect on a downhill road.

(Prior Art) It is known that if a foot brake is continuously depressed while traveling on a downhill, particularly a downhill where a steep slope continues for a long time (hereinafter, a downhill road), a braking force is reduced due to heating of a brake device or the like. ing. In such a case, the combined use of the engine brake is effective. For example, in a vehicle equipped with a manual transmission, an engine brake can be actuated by appropriately selecting a lower gear, so that the vehicle can travel safely on a downhill.

By the way, it is generally recognized that any of the following two operations may be performed when applying the engine brake in a vehicle equipped with an automatic transmission. One is to tilt the shift lever from the drive range to two ranges or one range.
One is a switch operation for inhibiting the overdrive in the drive range (turning off the overdrive switch). In particular, this operation can be expected to have a relatively large engine brake, and is effective when traveling downhill.

However, in view of the purpose of an automatic transmission, such as automating a gear shifting operation, even if it is for applying an engine brake, the necessity of an operation by a driver deviates from the purpose and is desirable. is not. In addition, engine braking when traveling on a descending road must be performed from the viewpoint of foot brake protection, and does not depend on the driver's will.

Considering the current situation, it is undeniable that not a few drivers over-consciously consider the "automatic" of the automatic transmission and do not operate not only the shift lever but also the overdrive switch. Letting the driver use the engine brakes, is of great doubt.

For these reasons, various proposals have been made in the past, such as the following.

First Conventional Example A system in which a descending slope is detected from a forward leaning angle of a vehicle body and an engine brake is automatically applied (see Japanese Patent Application Laid-Open No. 57-110849).

Second Conventional Example When the vehicle speed changes in a direction in which the vehicle speed increases in a state where an accelerator pedal is not depressed, the system detects traveling on a down slope and automatically applies an engine brake (Japanese Patent Laid-Open No.
195455).

And according to these conventional examples, when traveling downhill,
The engine brake can be operated without requiring any special operation.

(Problems to be Solved by the Invention) However, in the first conventional example, it is intended to detect a descending slope from the forward leaning angle of the vehicle body, but the forward leaning angle of the vehicle body depends on the balance of the longitudinal load. For example, the forward inclination angle naturally changes depending on the number of passengers in the rear seats and the amount of luggage in the rear trunk, which may lead to erroneous detection of a downhill road, which is a problem in terms of control reliability. There is a point.

Further, the second conventional example has a disadvantage that it is impossible to detect a downhill road when the accelerator pedal is slightly depressed. That is, in practice, it is extremely rare that the foot is completely released from the accelerator pedal while traveling on a downhill, except when the brake is operated, and the second condition in which this rare state is one of the control conditions is considered. The conventional example is not sufficient in terms of reliably detecting a downhill road.

Therefore, an object of the present invention is to improve the accuracy of detection of a downhill road and stably apply an engine brake when traveling on a downhill road.

(Means for Solving the Problems) In order to achieve the above object, a shift control device for a vehicle according to the present invention has a basic conceptual diagram as shown in FIG. A first output means for outputting a first index which decreases with an increase in an output signal from a physical quantity detecting means for detecting a physical quantity involved in combustion of the engine, Calculating a logical product or an algebraic product of the first and second indices, a second output means for outputting a second index which increases with an increase in an output signal from the acceleration detecting means for detecting the acceleration of the vehicle; And a command means for commanding selection of a shift speed that allows transmission of reverse driving force from the driving wheel side to the engine side when the calculated value of the calculating means exceeds a predetermined reference value. ing.

(Operation) In the present invention, the first and second indices are obtained as large values in the driving state where the depression amount of the throttle pedal is small and the vehicle speed naturally increases, and these calculated values are obtained. When the value exceeds the reference value, downhill traveling is determined.

Here, it is needless to say that the calculated value may be a “logical AND operation value” of the first index and the second index, but other than this, the first index and the second index "Algebraic product operation value".

Hereinafter, the present invention will be described with reference to the drawings.

2 to 4 are views showing an embodiment of a shift control device for a vehicle according to the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes a sensor group. The sensor group 1 is a throttle opening sensor 2 for detecting a throttle opening TVO, and a vehicle speed for detecting a vehicle speed V from the number of revolutions of an output shaft, a driving wheel, and the like of an automatic transmission. sensor 3, the type detection sensor 4 for detecting the gasoline type F (type such as whether regular gasoline or high-octane gasoline), the engine coolant temperature sensor 5 that detects the engine coolant temperature T _F, detects the oil temperature T ₀ of the automatic transmission ATF An oil temperature sensor 6 and a vehicle body load sensor 7 for detecting a vehicle body load W are provided. The throttle opening sensor 2 functions as physical quantity detecting means.
In addition, as the physical quantity detecting means, a means for detecting a fuel supply amount (or an injection amount), a boost pressure or the like may be used. The point is that it only needs to detect a physical quantity involved in combustion of the engine.

Reference numeral 10 denotes an automatic transmission control device (hereinafter referred to as ATCU).
Is provided with a mapped shift pattern. The ATCU 10 refers to a shift pattern based on the throttle opening TVO and the vehicle speed V, determines a shift stage, and outputs a shift signal SEL indicating the shift stage. However, when the command signal EB is input from the sub-control device 20 to be described later, the “predetermined shift speed at which the engine braking effect can be expected”
(To be described later) is determined, and SEL indicating the predetermined gear position is output. That is, when the command signal EB is output,
The selection of the predetermined gear position is instructed irrespective of the mapped shift pattern. Reference numeral 11 denotes a valve controller of the automatic transmission. The valve controller 11 combines valves in accordance with SEL and operates a known transmission mechanism of the automatic transmission 12.

The automatic transmission 12 has a speed change mechanism composed of a planetary gear, a multi-plate clutch, a brake band, a multi-plate brake, a one-way clutch, and the like. Of these elements, a specific multi-plate clutch (overrun clutch and (Sometimes referred to as "brake"), the reverse driving force can be transmitted from the driving wheel side to the engine side (so-called engine braking action). The engagement of the overrun clutch is performed at, for example, the first and second speeds of the drive range, the second speed of the first and second ranges, and the first speed of the one range. Therefore, the "predetermined gear stage" refers to the first and second speeds of the drive range, the second speed of the first and second ranges, and the first speed of the one range. Of course, it is sufficient that the shift speed is such that the engine brake can be applied, and the speed is not limited to the above example.

On the other hand, reference numeral 20 denotes a sub-control device having functions as acceleration detection means, calculation means and command means. The sub-control device 20 calculates the acceleration of the vehicle according to various signals from the sensor group 1, and calculates ▼ (TVO
The moving average value is used to calculate an estimated value λ of the magnitude of the downhill slope, and when the λ is larger than a predetermined reference value, the operation is performed so as to output the command signal EB. In the sub-controller 20, there are two function tables used when calculating λ, that is, an f _(X) function table shown in FIG. 3A and a g _(Z) function shown in FIG. 3B. A table is provided. In these tables, f _(X) functions as a first output unit, and g _(Z) functions as a second output unit. Details will be described later.

 Next, the operation will be described.

FIG. 4 is a flowchart of a program executed inside the sub-control device 20. In FIG. 4, first, the vehicle speed V detected by the vehicle speed sensor 3 and the throttle opening TVO detected by the throttle opening sensor 2 are read (steps P ₁ and P ₂ ), and the moving average value of the TVO is calculated according to the following equation.
Calculate ▼ (step P ₃ ).

The above is to improve the reliability of data by smoothing the flapping of the accelerator pedal and the whirling during traveling with a primary filter, and it is preferable that the time constant in the above equation is about 20 seconds.

Next, although the processing steps are omitted, a one-step difference value Δv _(t) of V at a predetermined time Δt is obtained, smoothed, and used as the acceleration of the vehicle.

Next, an estimated value λ of the magnitude of the slope of the downhill is calculated based on ▲ and 求 め thus obtained (step P ₅ ). The calculation of λ is performed as follows. That is, the function table f _(X) shown in FIG.
The function table g shown in FIG.
_(Z) , the minimum value (not large ₎ of the value of f _(X) as the first index and the value of g _(Z) as the second index, which is looked up from both tables. Is calculated, and the calculated value is determined as λ (this calculated value is generally called a logical product). F _(X) shown in FIG. 3 (a) is, for example, a linear function line connecting two points (a) and (b).
The opening corresponds to zero, and ▲ at the point (b) corresponds to a throttle opening capable of generating an engine speed of, for example, about 2000 rpm in each gear. FIG. 3 (b)
G _(Z) shown in, for example a linear function straight line connecting two points (C) (D), is at the point (c), in the heavy-load throttle fully closed and typical downhill slope (e.g. −10%), which corresponds to the vehicle acceleration on a typical downhill slope with the throttle fully closed and a light load at point (d). Note that the slopes of the straight lines of f _(X) and g _(Z) shown in FIGS. 3 (a) and 3 (b) are merely examples, and the present invention is not limited thereto. Further, f _(X) and g _(Z) are desirably set for each shift speed.

The obtained λ is used as follows. First, λ is compared with a predetermined reference value L _Hi, and when λ exceeds L _Hi , traveling downhill is determined (step P ₆ ). Then, at the time of this determination, ED is output (step P ₇ ) to cause the automatic transmission to select a predetermined shift speed and apply the engine brake. On the other hand, when the λ does not exceed L _Hi in step P _6, the λ is determined whether below a predetermined reference value _{L LOW (L Hi> L LOW} ) ( step P _8), when the YES instruction ED Is stopped (engine brake release) (step P ₉ ).

As described above, in the present embodiment, the throttle opening information (▲ ▼) is used for the physical quantity related to the combustion of the engine,
The two function tables f _(X) and g _(Z) are referred to according to ▲ ▼ and the acceleration information (), and the value of f _(X) as the first index looked up from the function table and the second
The calculated value of the logical product with the value of g _(Z) as the index of is determined as the estimated value (λ) of the amount of downhill slope, and when this λ is greater than L _Hi , downhill traveling is determined. Thus, a predetermined gear position is selected. That is, the first index (f _(X) ) changes to a large value as the throttle opening is closed, while the second index (g _(Z) ) changes to a large value as the acceleration increases. Therefore, the degree of inclination of the downhill can be correctly represented by λ obtained by adding the first and second indices. Therefore, the detection accuracy of traveling downhill can be improved, and the engine brake can be applied stably during the traveling.

In the above embodiment, the logical product of the first index (f _(X) ) and the second index (g _(Z) ) is calculated and the estimated value (λ) is calculated.
, But instead of calculating the logical product, the algebraic product (2
Multiplied by two values. A so-called product) may be calculated to obtain the estimated value (λ).

(Effects) According to the present invention, it is possible to improve the accuracy of detecting a downhill road, and to stably apply an engine brake during traveling on a downhill road.

[Brief description of the drawings]

FIG. 1 is a diagram showing the basic concept of the present invention, and FIGS. 2 to 4 are views showing an embodiment of a shift control device for a vehicle according to the present invention.
FIGS. 3 (a) and 3 (b) show the function tables f _(X) and g _(Z) , respectively, and FIG. 4 is a flowchart of the processing program. 2 ... Throttle opening sensor (physical quantity detection means), 12 ...
... automatic transmission, 20 ... sub-controllers (acceleration detection means, calculation means, command means), f _(X) , g _(Z) ... function tables (first and second output means).

Claims (1)

(57) [Claims] 1. A shift control device for a vehicle capable of automatically switching a shift speed of an automatic transmission according to a mapped shift pattern, wherein a shift amount of an output signal from a physical quantity detecting means for detecting a physical quantity involved in combustion of an engine is provided. First output means for outputting a first index that decreases with an increase, and second output means for outputting a second index that increases with an increase in an output signal from the acceleration detection means for detecting the acceleration of the vehicle. Calculating means for calculating a logical product or an algebraic product of the first and second indices; and a reverse driving force from the driving wheel side to the engine side when the calculated value of the calculating means exceeds a predetermined reference value. A gear shift control device for a vehicle, comprising: command means for commanding selection of a shift speed that allows transmission.