JP2010151154A - Control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a vehicle capable of reducing a shift busy feeling during slope descending control and reducing an uncomfortable feeling caused by weak accelerator-on during slope descending running. <P>SOLUTION: When running down a gentle slope, in the case when a target deceleration can be achieved within a load limit of an alternator, the slope descending control is executed only by the alternator. When the target deceleration cannot be achieved by just the alternator, load of the alternator is maximized, and shift control of a continuously variable transmission is executed so that a target input speed is achieved for obtaining insufficient load torque obtained by subtracting the load torque of the alternator from torque required for achieving the target deceleration. Thereby, excessive fluctuation of engine speed caused by on/off of the slope descending control is eliminated and the shift busy feeling can be reduced, and the uncomfortable feeling caused by lowering of the engine speed by weak acceleration (accelerator-on) during the slope descending control can be eliminated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a vehicle control device including a continuously variable transmission and a load variable alternator, and more particularly to a control device for performing downhill control.

Conventionally, when driving downhill, control the gear ratio of the continuously variable transmission to keep the engine speed high according to the slope of the downhill, slow down the acceleration with the engine braking force, and make it difficult to increase the vehicle speed Has been done. This is called downhill control. In descending slope control, the road surface gradient is detected, and the larger the detected road surface gradient, the higher the minimum target input rotational speed is restricted, and the stepless control is made so that it exceeds the lower limit value limited by the minimum target input rotational speed. Shift control of the transmission is performed.

However, if the difference between the engine speed when the accelerator is fully closed and the engine speed during downhill control is large, there is a problem that the driver feels uncomfortable (shifting busy feeling) by turning on / off the downhill control. . In addition, the downhill control is turned off (cancelled) just by depressing the accelerator pedal a little during downhill control, but the shift point in the shift diagram when the weak accelerator is on is lower than the shift point during downhill control. In this case, despite the intention to accelerate, the engine speed decreases and the user feels uncomfortable.

Patent Document 1 proposes an engine-driven alternator that increases the braking force by applying a load during deceleration traveling. Patent Document 2 proposes a method in which a target value for deceleration is set based on the road gradient at the time of downhill, and the speed ratio of the continuously variable transmission is controlled so as to obtain a desired engine braking force. . Patent Document 3 proposes changing the required charge amount to change the load of the alternator and increase the braking force.

In the case of Patent Document 1, since deceleration is not controlled using a continuously variable transmission, a load is applied only by an alternator. Therefore, in the case of a road surface gradient exceeding the load limit of the alternator, the deceleration is performed. There is a problem that cannot be controlled. In Patent Document 2, when driving downhill with the throttle fully closed, the target deceleration is controlled by maintaining the input rotational speed at a high rotational speed by the gear ratio control of the continuously variable transmission. If the pedal is stepped on, the downhill control is canceled, so that there is a concern that the input rotation speed is suddenly reduced and uncomfortable. Patent Document 3 describes that the load increase of the alternator is used during downhill, but it is not combined with downhill control of a continuously variable transmission, and is particularly useful for lowering the engine speed when the accelerator is weak. The accompanying discomfort is not considered at all.
JP-A-57-131840 JP-A-10-103469 Japanese Utility Model Publication No. 55-14048

An object of the present invention is to provide a vehicle control device that can reduce a shift busy feeling during downhill control and can reduce a sense of incongruity due to weak accelerator on during downhill driving.

In order to achieve the above object, the present invention includes a continuously variable transmission capable of continuously changing a gear ratio and a load variable type alternator driven by an engine, and wheels are driven by engine power via the continuously variable transmission. Vehicle speed detection means for detecting the vehicle speed of the vehicle, gradient estimation means for estimating the slope of the downhill road surface, brake detection means for detecting the brake operation, and the vehicle speed is equal to or higher than a predetermined vehicle speed, Means for determining the start of downhill control when the gradient is equal to or greater than a predetermined gradient and the brake is ON; and target deceleration setting means for setting a target deceleration for downhill control from the gradient value and the vehicle speed; Determining means for determining whether or not the target deceleration can be achieved within the load limit of the alternator, and the downhill control start determining means determines the start of downhill control, and the determining means determines the target deceleration. When the degree is determined to be achievable, the means for adjusting the load of the alternator to achieve the target deceleration, the downhill control start determination means determines the start of downhill control, and the determination means sets the target When it is determined that the deceleration cannot be achieved, the input for obtaining the insufficient load torque obtained by subtracting the alternator load torque from the torque necessary to achieve the target deceleration while maximizing the load of the alternator There is provided a vehicle control device comprising: means for performing shift control of a continuously variable transmission so as to achieve a rotational speed.

When the vehicle approaches a downhill, the vehicle speed, the road surface gradient, and the presence / absence of braking are determined. When the vehicle speed is equal to or higher than the predetermined vehicle speed, the gradient is equal to or higher than the predetermined gradient, and the brake is ON, the start of downhill control is determined. The predetermined vehicle speed is a minimum vehicle speed for determining whether or not it is necessary to perform downhill control, and is set, for example, in a region where the torque converter lockup is reliably turned on. A target deceleration for downhill control is preset in the vehicle based on the gradient value and the vehicle speed. Then, it is determined whether or not the target deceleration can be achieved within the load limit of the alternator. When the downhill control start determining means determines the start of downhill control, and the determination means determines that the target deceleration can be achieved, the load on the alternator is adjusted so as to achieve the target deceleration. That is, the target deceleration can be obtained only by adjusting the load of the alternator without performing the downhill control of the continuously variable transmission. The load of the alternator can be easily changed by changing the required power generation amount, for example. In addition, the engine brake at the time of normal driving | running can be made to act by implementing the fuel cut of an engine at this time. On the other hand, when the downhill control start determination means determines the start of downhill control and the determination means determines that the target deceleration cannot be achieved, the load on the alternator is maximized and the target deceleration is achieved. Shift control of the continuously variable transmission is performed so as to obtain a target input rotational speed that obtains an insufficient load torque (engine braking force) obtained by subtracting the load torque of the alternator from the torque required for the transmission. That is, the input rotational speed is increased and the engine braking force is increased. Thus, the target deceleration can be obtained by combining the load adjustment of the alternator and the shift control of the continuously variable transmission.

On a gentle downhill, the target deceleration can be obtained only by adjusting the load of the alternator.Therefore, there is no need to increase the engine speed, and the engine speed when the accelerator is fully closed and the engine speed during downhill control Can be made almost equal, and the downshift control is turned on / off, so that the driver is not given a shift busy feeling. Further, even if the accelerator pedal is depressed a little for slow acceleration during downhill control, the shift point hardly changes, so that the engine speed does not decrease and the user does not feel uncomfortable. Furthermore, when the slope of the downhill is increased, the target deceleration is obtained by using both the load adjustment of the alternator and the speed change control of the continuously variable transmission. The uncomfortable feeling that the engine speed sometimes decreases can be alleviated.

In the present invention, the slope estimation means for estimating the slope of the road surface is provided, but this slope estimation means can be estimated from the actual running state of the vehicle without using a special inclination sensor. Specifically, the gradient can be estimated from the output torque of the continuously variable transmission, the turbine torque, the actual gear ratio, the vehicle weight, the vehicle acceleration, and the like.

The control of the present invention does not always need to maximize the load of the alternator when it is determined that the target deceleration cannot be achieved only by adjusting the load of the alternator. For example, if it is determined that the gradient value is greater than a limit value greater than a predetermined gradient for starting downhill control, the target deceleration is achieved only by the shift control of the continuously variable transmission without adjusting the load of the alternator. It may be.

As described above, according to the present invention, downhill control is performed without increasing the engine speed as much as possible by using an alternator on a gentle downhill. Thus, the shift busy feeling can be reduced, and the uncomfortable feeling caused by the decrease in the engine speed during weak acceleration (accelerator on) during downhill control can be eliminated.

Hereinafter, preferred embodiments of the present invention will be described with reference to examples.

FIG. 1 shows an example of a vehicle system according to the present invention. An output shaft 11 of the engine 1 is connected to an input shaft (turbine shaft) 20 of the continuously variable transmission 2 via a torque converter 3 with a lock-up clutch. The input shaft 20 is connected to a drive shaft 25 via a belt type continuously variable transmission mechanism 21. Note that other mechanisms such as a forward / reverse switching mechanism are not shown. As is well known, the continuously variable transmission mechanism 21 wraps a belt 24 between a primary pulley 22 and a secondary pulley 23 and changes the belt wrapping diameters of the pulleys 22 and 23 to change the speed ratio. It will change in stages. The continuously variable transmission 2 is provided with a hydraulic control device 26 for operating the pulleys 22 and 23 and for controlling the lock-up clutch of the torque converter 3. The hydraulic control device 26 includes a plurality of solenoid valves. By controlling these solenoid valves with the control unit 40, the continuously variable transmission mechanism 21 is controlled to a desired gear ratio, and the lockup clutch is connected / disconnected. ing.

An alternator 15 is provided in the vicinity of the engine 1, and this alternator 15 is driven by the output shaft 11 of the engine 1 via a belt 16. The alternator 15 is a load variable type, and the load can be electrically varied by changing the required power generation amount by the control unit 40. As a means for changing the load of the alternator 15, any known means can be used.

The control unit 40 includes vehicle speed (secondary rotational speed), throttle opening (accelerator opening), engine speed, primary pulley rotational speed (input rotational speed), brake signal, P, R, N, D, L, etc. Signals are input from various sensors 41 to 47 that detect a shift position and the like, and the engine 1 and the continuously variable transmission 2 are controlled in an integrated manner, and the alternator 15 is also controlled. The memory of the control unit 40 stores an engine control program, a continuously variable transmission control program, an alternator control program, and various data. Since engine control and continuously variable transmission control are known per se, detailed description thereof is omitted.

A shift characteristic map of the continuously variable transmission 2 as shown in FIG. 2 is set in the control unit 40 in advance. As is well known, the speed change characteristic map has a target input rotational speed (target primary rotational speed) on the vertical axis, a vehicle speed (secondary rotational speed) on the horizontal axis, and an accelerator opening (or throttle opening) set as a parameter. It is. In FIG. 2, four characteristics of accelerator opening 0%, 25%, 50%, and 100% are shown. In addition to the accelerator opening, a minimum target input rotational speed for downhill control using a road surface gradient as a parameter is also set, and these minimum target input rotational speeds are set to change according to the vehicle speed. Here, level 1 (0.55 m / s ² ≧ a> 0.3 m / s ² ) is indicated by a hatched area as a road gradient, and level 2 (0.8 m / s ² ≧ a> 0.55 m / s ^2). ) And level 3 (a> 0.8 m / s ² ) are indicated by solid lines. The top of the diagonal line at level 1 represents the maximum load of the alternator.

As shown in FIG. 3, the gradient a indicates a value corresponding to the inclination angle θ of gravity acceleration, and a = G × sin θ. For example, in the case of a = 0.8 m / s ² , sin θ = 0.8 / 9.8 = 0.082, which is displayed as a gradient of about 8%.

The minimum target input rotational speed characteristic using the road gradient as a parameter is not limited to the above three levels, but may be set to two or four or more, and an area between them may be obtained by interpolation calculation. The control unit 40 can obtain a target input rotational speed (target primary rotational speed) from the vehicle speed and the accelerator opening during traveling, and can control the gear ratio so that the actual input rotational speed becomes the target input rotational speed. In particular, when a predetermined condition is satisfied on the downhill, the shift control (downhill control) is performed with the minimum target input rotational speed corresponding to the road surface gradient shown in FIG. 2 as the lower limit value.

For example, as indicated by a point K0 in FIG. 2, when the vehicle is traveling on a flat road at a vehicle speed of 60 km / h and an accelerator opening of 0%, the vehicle approaches a downhill, and when the road surface gradient becomes level 2, the target input speed When the road surface gradient reaches level 3, the lower limit value of the target input rotational speed increases to point K2. That is, the gear ratio increases (shifts to the low speed ratio). By maintaining the input rotational speed (engine rotational speed) high in this way, control is performed to slow down the acceleration by the engine braking force and make it difficult to increase the vehicle speed, that is, downhill control.

FIG. 4 shows a target deceleration characteristic for downhill control. In FIG. 4, target decelerations are set for normal shifting (flat road), level 1 (when using an alternator), level 2 and level 3. Level 1 corresponds to, for example, a gradient of 3.0% to 5.5% and depends on the capacity of the alternator. However, such a gentle gradient can usually be dealt with by adjusting the load of the alternator. Level 2 corresponds to, for example, a slope of 5.5% to 8.0%, level 3 corresponds to a slope of, for example, more than 8.0%, and the normal shift <level 1 <level 2 <level 3 The deceleration is set higher sequentially according to the gradient. The target deceleration is set to increase as the vehicle speed increases.

In addition to the shift control, the control unit 40 also has a function of estimating the road gradient from the actual running state of the vehicle. The gradient (m / s ² ) is calculated from the value obtained by dividing the theoretical driving force (N) by the vehicle body weight (kg) as shown in the following equation, and the running resistance (m / s ² ) and the actual acceleration (m / s ^2). ) Can be subtracted. Here, the running resistance is obtained by dividing the running resistance (N) by the vehicle body weight (kg).
Gradient = theoretical driving force / vehicle weight-traveling resistance-actual acceleration Theoretical driving force is obtained by engine torque × gear ratio × efficiency / tire diameter. Since the running resistance is a fixed value depending on the vehicle type, it can be obtained as a map value. The actual acceleration can be obtained from the differential value of the vehicle speed. Note that the gradient estimation method is not limited to the above method, and may be obtained by another known method.

FIG. 5 is a flowchart of an example of downhill control according to the present invention. First, vehicle speed, engine speed, primary pulley speed, throttle opening, brake signal, etc. are detected (step S1). Next, whether the vehicle speed is in the range of 20 km / h to 100 km / h (step S2), whether the throttle opening is fully closed (step S3), whether the brake is ON (step S4), It is determined whether it is a downhill (step S5). If any of steps S2 to S5 is negative, normal flat road control is performed (step S6). When the vehicle speed is less than 20 km / h and more than 100 km / h, the downhill control is not performed because there is no need to perform the downhill control. If it is 20 km / h or more, it is surely in the lockup ON region. In addition, when the vehicle speed is equal to or higher than a predetermined vehicle speed (for example, 20 km / h), the determination as to whether the vehicle speed is higher than 100 km / h may be omitted. If the throttle is fully closed (accelerator OFF), the fuel cut of the engine is performed. Further, if the brake is OFF, the driver does not attempt to decelerate, so the downhill control is not performed. In the downhill determination (S5), as described above, the gradient of the road surface is estimated from the actual running state of the vehicle, and it is determined whether or not the estimated gradient a is equal to or less than level 1 (0.3 m / s ² ). To do. If the road surface gradient is small, that is, if the gradient a ≦ 0.3m / s ^2, the continuously variable transmission is performed on a flat road control (step S6), and does not perform the exceptional load control of the alternator for downhill .

When all of steps S2 to S5 are affirmed, it is determined whether the slope a of the downhill is level 1 to 3 (steps S7 to S9). If it is determined that the gradient a is level 1 (0.55 m / s ² ≧ a> 0.3 m / s ² ) (step S7), then the current alternator load torque is subtracted from the maximum alternator load torque. The torque that can be used for downhill control is calculated (step S10). Then, the required torque for obtaining the target deceleration of level 1 is obtained from FIG. 4, and this required torque is compared with the torque that can be used for descending slope control (step S11). The target acceleration can be obtained only with the alternator load torque (auxiliary loss torque calculated from the alternator load) without performing the downhill control of the step transmission, so the level 1 downhill control is performed only with the alternator. (Step S12). At this time, since the continuously variable transmission performs normal flat road control and the engine performs fuel cut, the engine braking force during normal travel is applied. If the accelerator pedal is depressed a little during downhill control, the downhill control is turned off (released) and the normal shift control is performed. However, since the downhill control is performed only by the alternator, the vertical movement of the engine rotation is not performed. There is little, and a sense of incongruity can be reduced.

On the other hand, in step S11, if the required torque is greater than the usable torque, the descending slope control of level 1 cannot be performed only by the alternator, so the engine speed increase for obtaining the insufficient load torque (engine braking force) is set. Calculate (step S13). Then, the continuously variable transmission is shift-controlled so that the load torque of the alternator is maximized and the calculated engine speed increases (step S14). Thus, a desired target deceleration can be obtained by the sum of the alternator load torque and the engine braking force. The amount of increase in engine speed at this time can be lower than the amount of increase when downhill control is performed only with a continuously variable transmission without using an alternator, so when downhill control is canceled due to weak accelerator on. The feeling of strangeness can be reduced.

When it is determined that the gradient a is level 2 (0.8 m / s ² ≧ a> 0.55 m / s ² ) (step S8), a required load torque that can obtain the target deceleration of level 2 is calculated ( In step S15), the required increased engine speed is calculated from the required load torque (step S16). Then, the speed change control of the continuously variable transmission, that is, the level 2 downhill control (step S17) is performed with the engine speed as the lower limit.

When it is determined that the gradient a is level 3 (a> 0.8 m / s ² ) (step S9), a required load torque that can obtain the target deceleration of level 3 is calculated (step S15). The required engine speed is calculated from the required load torque (step S16). Then, the speed change control of the continuously variable transmission, that is, the level 3 downhill control (step S18) is performed with the engine speed as the lower limit.

In FIG. 5, when the road surface gradient is large as in levels 2 and 3, load control of the alternator is not performed. However, if the capacity of the alternator is large, even in downhill control of level 2 and 3, Similarly to step S14 of level 1, the load torque of the alternator may be maximized and used in combination with the shift control of the continuously variable transmission.

The continuously variable transmission according to the present invention is not limited to a V-belt type continuously variable transmission, but can be applied to a continuously variable transmission of another type such as a toroidal continuously variable transmission. Moreover, in the said Example, although the rotation speed of the primary pulley was used as input rotation speed, the turbine rotation speed which is the output rotation speed of a torque converter can also be used. Further, although the torque converter with a lock-up clutch is provided on the input side of the continuously variable transmission, the present invention can also be applied to a continuously variable transmission that does not have a torque converter.

1 is a system diagram of a vehicle according to the present invention. It is a speed change characteristic figure of a continuously variable transmission. It is a figure which shows the relationship between the gradient of a road surface, and the gravitational acceleration of a vehicle body. It is a figure which shows the relationship between the target deceleration and vehicle speed in downhill control. It is a flowchart figure of an example of the downhill control which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Continuously variable transmission 3 Torque converter 15 Alternator 20 Input shaft 21 Continuously variable transmission mechanism 22 Primary pulley 23 Secondary pulley 24 Belt 25 Output shaft (drive shaft)
26 Hydraulic Control Device 40 Control Unit 41 Vehicle Speed Sensor 42 Throttle Opening Sensor 43 Engine Speed Sensor 44 Turbine (Primary) Speed Sensor 45 Brake Sensor 46 Shift Position Sensor

Claims (1)

In a vehicle including a continuously variable transmission capable of continuously changing a gear ratio and a load variable alternator driven by an engine, and driving wheels via a continuously variable transmission by engine power,
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
A slope estimation means for estimating the slope of the downhill road surface;
Brake detecting means for detecting brake operation;
Means for determining the start of downhill control when the vehicle speed is equal to or greater than a predetermined vehicle speed, the gradient is equal to or greater than the predetermined gradient, and the brake is ON;
Target deceleration setting means for setting a target deceleration for downhill control from the gradient value and the vehicle speed;
Determination means for determining whether or not the target deceleration can be achieved within the load limit of the alternator;
Means for adjusting the load on the alternator so as to achieve the target deceleration when the downhill control start determining means determines the start of downhill control and the determination means determines that the target deceleration can be achieved; ,
When the downhill control start determining means determines the start of downhill control and the determination means determines that the target deceleration cannot be achieved, the load on the alternator is maximized and the target deceleration is Means for carrying out shift control of the continuously variable transmission so as to obtain an input rotational speed that obtains an insufficient load torque obtained by subtracting the load torque of the alternator from the torque necessary to achieve A vehicle control device.

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