JP2014151679A - Vehicle running control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the same sense of acceleration as that to be perceived during normal driving by shortening a turbo lag of an engine with a supercharger occurring during cruise-controlled run.SOLUTION: A required torque calculation part 25c obtains a required torque Td on the basis of a target driving force Ft which is set in order to attain a target acceleration αt during cruise-controlled run, and a vehicle speed V. An instruction torque calculation part 25d references an engine instruction torque map on the basis of the required torque Td and a boost pressure of a turbo supercharger 5, and obtains an engine instruction torque TE/G for setting an instruction throttle angle THd. The engine instruction torque TE/G stored in the engine instruction torque map is set to a value nearly identical to the required torque Td, however the engine instruction torque TE/G in a domain in which a turbo lag is outstandingly manifested is set to a value higher than the required torque Td. As a result, the same sense of acceleration as that to be perceived during normal driving can be obtained during cruise-controlled run.

Description

  The present invention relates to a vehicle travel control device capable of obtaining an acceleration feeling equivalent to that of normal driving even in cruise traveling.

  Conventionally, for example, an ACC (Adaptive Cruise Control) device with an inter-vehicle distance control is a traveling environment in front of the host vehicle (preceding vehicle) acquired by a millimeter wave radar, an infrared laser radar, a stereo camera, a monocular camera or the like mounted on the vehicle. Various techniques for recognizing obstacles, etc., and controlling the traveling of the host vehicle have been proposed.

  In such an ACC device, when the vehicle (preceding vehicle) is not captured in front of the host vehicle, the vehicle travels at a constant speed with the vehicle speed (set vehicle speed) set by the driver as the target vehicle speed, captures the preceding vehicle, and When the vehicle speed of the preceding vehicle is equal to or lower than the set vehicle speed, follow-up running control is performed to follow the preceding vehicle with a predetermined distance between the vehicles.

  When the vehicle speed of the host vehicle (host vehicle speed) is slower than the target vehicle speed (set vehicle speed or preceding vehicle speed), a target acceleration is set according to the difference, and the host vehicle speed is quickly increased to the target vehicle speed by accelerating to a predetermined level. I try to make it reach.

  By the way, in a naturally aspirated engine, the engine output changes almost linearly with respect to the opening degree of the throttle valve (throttle opening degree), so that the throttle opening degree is controlled in cruise driving (hereinafter referred to as “ACC driving”). Thus, a desired engine output can be easily obtained.

  However, in the supercharged engine, the engine output characteristic with respect to the throttle opening has a strong non-linearity, so that it is difficult to obtain a stable engine output characteristic even if the same control as that of the naturally aspirated engine is performed.

  Therefore, for example, in Patent Document 1 (Japanese Patent No. 4474326), during ACC running, the turbocharger supercharging pressure is fixed at a constant low pressure, thereby suppressing engine output fluctuations due to changes in throttle opening. In addition, a technique for obtaining good running stability is disclosed.

Japanese Patent No. 4474326 JP-A-6-26351

  However, in the technique disclosed in the above-described document, the turbocharger is fixed at a constant low pressure during ACC travel, so that it is impossible to obtain the feeling of acceleration of soot that is obtained in normal driving. It will undermine expectations.

  In normal operation, the driver knows the turbo lag (superior pressure rise delay) of the turbocharger empirically. Therefore, the driver expects a drop in torque and depresses the accelerator pedal. ing. However, since the acceleration during ACC traveling is set to be almost constant, particularly in acceleration traveling in a low speed region, there is a disadvantage that torque shortage occurs due to the turbo lag described above, which makes the driver feel unsatisfactory.

  As a countermeasure, for example, in Patent Document 2 (Japanese Patent Laid-Open No. 6-26351), in a sequential turbo equipped with a primary turbo and a secondary turbo, when the host vehicle speed is lower than a target vehicle speed by a predetermined value or more during ACC travel, A technique is disclosed in which only the mari turbo is operated to obtain good responsiveness.

  However, Patent Document 2 is applicable only to a vehicle equipped with a sequential turbo engine, cannot be applied to a vehicle equipped with a single turbo engine, and has a problem of lack of versatility.

  In view of the above circumstances, the present invention is able to obtain the same acceleration feeling as in normal driving during cruise driving, even with a supercharged engine, without impairing the driver's expectation. An object of the present invention is to provide a vehicle travel control device that can be applied without affecting the type of turbocharger and can obtain good versatility.

  The present invention provides a supercharging pressure detecting means for detecting a supercharging pressure of intake air supplied to an engine and supercharged by a supercharger, a throttle actuator for opening and closing a throttle valve, and a preset cruise driving target Target acceleration calculation means for obtaining a target acceleration for converging the vehicle speed of the host vehicle to the one target vehicle speed based on one of the vehicle speed or the target vehicle speed for cruise traveling set based on the relative vehicle speed between the preceding vehicle and the host vehicle; Based on the required torque calculating means for obtaining the required torque for obtaining the target acceleration, and the engine instruction torque map stored in the storage means based on the required torque and the boost pressure detected by the boost pressure detecting means. A command torque calculating means for obtaining an engine command torque, a command throttle opening corresponding to the engine command torque, and a command torque. In a vehicle travel control device comprising a throttle opening calculation means for operating the throttle actuator with a drive signal corresponding to a throttle opening, the engine command torque map is stored in a region where turbo lag appears prominently. The engine command torque is set to a high value that shortens the turbo lag.

  According to the present invention, the engine instruction torque stored in the area where the turbo lag appears prominently in the engine instruction torque map searched for cruise traveling is set to a high value for shortening the turbo lag. Even in such a case, it is possible to obtain the same acceleration feeling as in normal driving during cruise driving, and the driver's expectation for acceleration is not impaired. Moreover, since only the value of the engine command torque stored in the engine command torque map is changed, it can be applied individually without affecting the type of turbocharger, and good versatility can be obtained. Can do.

Schematic configuration diagram of a travel control device having an engine control unit and a cruise control unit Functional block diagram showing the configuration of the engine control unit and cruise control unit during cruise control Conceptual diagram of engine command torque map Time chart showing the relationship between command torque, throttle opening, boost pressure and actual torque

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 in FIG. 1 denotes an engine with a turbocharger (hereinafter simply referred to as “engine”). An intake pipe 2 communicates with the intake side of the engine 1 and an exhaust pipe 3 communicates with the exhaust side. A throttle valve 4 is interposed in the middle of the intake pipe 2, and a compressor 5 a constituting the turbocharger 5 is interposed further upstream of the throttle valve 4. Although not shown, an air cleaner is interposed in the intake intake port of the intake pipe 2.

  The throttle valve 4 constitutes an electronically controlled throttle, and a throttle actuator 6 is connected to the throttle valve 4. The throttle actuator 6 is a throttle motor such as a step motor or a servo motor, and the throttle valve 4 is directly opened and closed by the throttle motor. Further, a turbine 5b constituting the turbocharger 5 is interposed in the middle of the exhaust pipe 3, and further, a muffler (not shown) is interposed downstream thereof.

  The throttle valve 4 is provided with a throttle opening sensor 10 such as a potentiometer for detecting the throttle opening TH [%] of the throttle valve 4, and further downstream of the throttle valve 4 of the intake pipe 2. A pressure sensor 11 is connected as supercharging pressure detection means for detecting the pressure (intake pipe pressure) downstream of the throttle valve 4 as an absolute pressure. In the present embodiment, the supercharging pressure of the intake air supercharged by the compressor 5a of the turbocharger 5 is detected by the pressure sensor 11, so that the intake pipe pressure will be read as the supercharging pressure Pt in the following. explain.

  The sensors 10 and 11 are connected to the input side of an engine control unit (E / G_ECU) 21 that controls the operating state of the engine 1. In addition to the sensors 10 and 11 described above, the E / G_ECU 21 includes a vehicle speed sensor 12 that detects the vehicle speed V, an engine speed sensor 13 that detects the engine speed Ne, and other sensors that detect the operating state of the engine 1. Is connected. The E / G_ECU 21 is configured by a computer such as a microcomputer having a memory such as a ROM and a RAM and a CPU, and the ROM stores fixed data such as a control program and various maps. The E / G_ECU 21 executes normal engine control such as air-fuel ratio control and ignition timing control based on the signals of the input sensors according to the control program.

  On the other hand, reference numeral 22 denotes a forward recognition unit as forward recognition means, which includes an in-vehicle camera 23 and an image recognition unit (IPU) 24 that processes an image in front of the host vehicle taken by the in-vehicle camera 23. . The in-vehicle camera 23 is a stereo camera having a main camera 23a and a sub camera 23b, and both the cameras 23a and 23b are fixed to the upper part of the front part of the vehicle interior (for example, on both sides of the room mirror) with a certain distance therebetween. Has been. In addition, the IPU 24 performs predetermined image processing on the image signal of the traveling environment in front of the host vehicle photographed by both the cameras 23a and 23b, and based on the processed image, the preceding vehicle that travels immediately before the host vehicle, the front of the host vehicle. Recognize forward information such as road shapes such as curves. The information recognized by the IPU 24 is output to the cruise control unit with inter-vehicle distance control (ACC_ECU) 25 as front recognition information.

  The ACC_ECU 25 is configured by a computer such as a microcomputer having a memory and a CPU such as a ROM and a RAM, like the above-described E / G_ECU 21, and the ROM stores fixed data such as a control program and various maps. The ACC_ECU 25 calculates an instruction torque necessary for vehicle travel based on the signals of the input sensors according to the control program. The ECUs 21 and 25 are connected to each other through a known in-vehicle communication line 26 such as a CAN (Controller Area Network).

  In addition to the IPU 24, a set vehicle speed switch 16 that sets a target vehicle speed Vt (= set vehicle speed Vset) at the time of ACC travel is provided on the input side of the ACC_ECU 25 in addition to the steering wheel (handle) operated by the driver. It is connected.

  The ACC_ECU 25 obtains a target driving force Ft based on the input parameters, obtains a cruise control required torque (hereinafter simply referred to as “requested torque”) Td required to realize the target driving force Ft, Based on the torque Td and the boost pressure Pt, the engine command torque TE / G is set. Further, when a preceding vehicle is recognized in front of the own vehicle runway and the vehicle speed of the preceding vehicle is slower than the set vehicle speed Vset, the relative vehicle speed is obtained from the change in the current inter-vehicle distance, and the actual vehicle speed is calculated based on the relative vehicle speed. A target vehicle speed (following target vehicle speed) Vt for maintaining the inter-vehicle distance at a preset target inter-vehicle distance is set.

  As shown in FIG. 2, the ACC_ECU 25 includes a target acceleration calculating unit 25a as a target acceleration deriving unit, a driving force calculating unit 25b, and a required torque calculating unit as a required torque calculating unit as functions for obtaining the engine instruction torque TE / G. 25c, and an instruction torque calculation unit 25d as instruction torque calculation means.

  The engine command torque TE / G obtained by the ACC_ECU 25 is read by the E / G_ECU 21. The E / G_ECU 21 includes a throttle opening calculation unit 21a, which is a throttle opening calculation means, as a function for obtaining the indicated throttle opening THd [%].

  Next, engine control during ACC travel executed by the above-described ACC_ECU 25 and E / G_ECU 21 will be described.

  When the preceding vehicle is recognized based on the forward recognition information obtained by the IPU 24, the target acceleration calculating unit 25a of the ACC_ECU 25 obtains the relative vehicle speed by differentiating the inter-vehicle distance between the preceding vehicle and the host vehicle. The following target vehicle speed Vt described above is set based on the relative vehicle speed, and the target acceleration αt for following the vehicle while maintaining the target inter-vehicle distance is set by differentiating the following target speed Vt with respect to time. On the other hand, when the preceding vehicle is not recognized, the target acceleration αt for converging the own vehicle speed V to the set vehicle speed Vset is set by differentiating the difference between the set vehicle speed Vset and the own vehicle speed V over time.

  The driving force calculation unit 25b calculates a running resistance (air resistance, acceleration resistance, rolling resistance, gradient resistance). Among these, the acceleration resistance is obtained by dividing the acceleration α obtained by differentiating the own vehicle speed V with time by the gravitational acceleration g (α / g). The gradient resistance is obtained based on the road surface gradient θ detected using an existing sensor (for example, a longitudinal acceleration sensor) and the total weight W of the host vehicle (W · sin θ). Further, the road surface gradient θ is obtained by subtracting α / g (g: gravitational acceleration) from the longitudinal acceleration Gx (θ = Gx−α / g). In this embodiment, air resistance and rolling resistance are set to constant values.

Then, the resistance component is added to obtain the running resistance R, and based on the running resistance R and the target acceleration αt, a target driving force Ft for obtaining the target acceleration αt is obtained.
Ft = W · αt + R
Ask from.

Then, in the required torque calculation unit 25c, a required torque Td corresponding to the target driving force Ft is obtained. Specifically, first, the target output Pw is set based on the target driving force Ft and the vehicle speed V. Next, the required torque Td is calculated based on the target output Pw and the total reduction ratio σi.
Td = Pw · r / σi
Ask from. Here, r is the radius of the drive wheel. For example, when the automatic transmission is a continuously variable transmission (CVT), the total reduction ratio σi is equal to the speed ratio i (= Np / Ns) between the primary rotation speed Np and the secondary rotation speed Ns. This is calculated by multiplying the reduction ratio (fixed value) after CVT, such as a differential device.

  Based on the required torque Td and the supercharging pressure Pt, the command torque calculation unit 25d refers to the engine command torque map shown in FIG. 3 with interpolation calculation to obtain the engine command torque TE / G. The engine command torque TE / G is fixed data stored in a ROM (storage means), and its characteristics are almost the same as the required torque Td set for each boost pressure Pt. The engine command torque TE / G in the region where the rise of the boost pressure is noticeable appears higher than the required torque Td so that the turbo lag can be shortened as a whole.

  That is, the required torque Td indicated by the thick line in FIG. 4 and the supercharging pressure Pt indicated by the broken line are substantially proportional. Therefore, by controlling the supercharging pressure Pt by the opening degree of the throttle valve 4, the required torque Td is obtained. A corresponding engine torque can be obtained. However, in general, the turbocharger 5 has a unique turbo lag (a delay in rising of the boost pressure), and even if the throttle valve 4 is opened at a throttle opening corresponding to the required torque Td, FIG. As indicated by the alternate long and short dash line, the engine torque temporarily falls due to the delay in the rise of the supercharging pressure Pt. This turbo lag is remarkably generated in a region where the supercharging pressure Pt is low and the required torque Td is high.

  Therefore, in this embodiment, as shown in the engine instruction torque map of FIG. 3, the turbo lag is stored in a region where the turbo lag appears significantly (in this embodiment, the region where the boost pressure Pt is low and the required torque Td is high). The engine command torque TE / G is set higher than the conventional value indicated by the alternate long and short dash line in FIG. The extent to which the engine command torque TE / G in the region where the turbo lag appears noticeably is determined by obtaining an optimum value from an experiment or the like. Note that the region in which the turbo lag appears remarkably has individual differences for each turbocharger, and therefore the characteristics of the engine command torque TE / G are set for each turbocharger.

  The engine command torque TE / G obtained by the command torque calculator 25d is read by the throttle opening calculator 21a of the E / G_ECU 21. The throttle opening calculation unit 21a sets a command throttle opening THd [%] by referring to a throttle map (not shown) based on the engine command torque TE / G obtained by the command torque calculation unit 25d. This throttle map is for converting the engine command torque TE / G into the command throttle opening THd [%]. The relationship between the engine torque and the throttle opening is obtained in advance through experiments or the like and mapped. .

  Then, the throttle opening calculation unit 21a outputs a drive signal corresponding to the set instruction throttle opening THd to the throttle actuator 6 to open / close the throttle valve 4 in a predetermined manner. Since the target acceleration αt set by the target acceleration calculation unit 25a of the ACC_ECU 25 described above is set based on the relative vehicle speed with the preceding vehicle or the difference between the set vehicle speed Vset and the host vehicle speed V, as a result, The opening degree of the throttle valve 4 is feedback controlled by the target acceleration αt.

  The command throttle opening THd set by the throttle opening calculation unit 21a is set based on the engine command torque TE / G set by referring to the throttle map, and the engine command stored in the throttle map is set. The characteristic of the torque TE / G is set to a high value of the engine command torque TE / G in the region where the turbo lag is remarkable, so that as shown in FIG. 4, the command throttle opening in the region where the drop in the supercharging pressure Pt is significant. THd is set to a large value.

  Then, in that region, the throttle opening TH is greatly opened, the exhaust pressure increases as the intake air amount increases, and accordingly, the rotational speed of the turbine 5b of the turbocharger 5 is promoted, and the compressor 5a The number of revolutions increases rapidly. As a result, the turbo lag is shortened, and as shown by the broken line in FIG. 4, the characteristic substantially follows the required torque Td, and the target acceleration αt during ACC traveling substantially matches the actual acceleration, which is the same as in normal driving. A feeling of acceleration can be obtained, and characteristics in line with the driver's expectation can be obtained.

  In addition, since it is possible to respond by simply changing the characteristics of the engine command torque TE / G stored in the throttle map, the turbocharger can be individually handled and good versatility can be obtained. Can do.

  The present invention is not limited to the above-described embodiment. For example, in a vehicle having a plurality of engine modes such as a sports mode, a normal mode, and an eco mode, the turbo lag is different for each engine mode. The engine instruction torque map described above may be provided for each engine mode, and the turbo lag may be shortened for each engine mode.

1 ... Engine,
5 ... Turbocharger,
6 ... Throttle actuator,
11 ... Pressure sensor,
16 ... Set vehicle speed switch,
21a: throttle opening calculation unit,
25a ... Target acceleration calculation unit,
25b ... Driving force calculation unit,
25c ... required torque calculation unit,
25d: Instruction torque calculation unit,
Ft: Target driving force,
Pt ... supercharging pressure,
Pw… Target output,
Td: Required torque,
TE / G: Engine command torque,
TH: throttle opening,
THd: Instruction throttle opening,
V ... Vehicle speed,
Vset ... set vehicle speed,
Vt ... Target vehicle speed,
α ... acceleration,
αt ... Target acceleration

Claims (3)

A supercharging pressure detecting means for detecting the supercharging pressure of the intake air supplied to the engine and supercharged by the supercharger;
A throttle actuator for opening and closing the throttle valve;
Based on one of the target vehicle speed for cruise driving set in advance or the target vehicle speed for cruise driving set based on the relative vehicle speed between the preceding vehicle and the host vehicle, the target acceleration for converging the vehicle speed of the host vehicle to the one target vehicle speed is Target acceleration calculation means to be obtained;
Required torque calculating means for determining a required torque for obtaining the target acceleration;
Instruction torque calculation means for retrieving an engine instruction torque by searching an engine instruction torque map stored in a storage means based on the required torque and a boost pressure detected by the boost pressure detection means;
In a travel control device for a vehicle, comprising a throttle opening degree calculation means for obtaining an indicated throttle opening degree corresponding to the engine instruction torque and operating the throttle actuator with a drive signal corresponding to the indicated throttle opening degree,
In the engine command torque map, the engine command torque stored in a region where the turbo lag appears prominently is set to a high value for shortening the turbo lag. The vehicle travel control apparatus according to claim 1, wherein the region in which the turbo lag appears significantly is a region in which the supercharging pressure is low and the required torque is high. The preceding vehicle is recognized based on an image in front of the host vehicle taken by an in-vehicle camera provided in a front recognition unit mounted on the host vehicle,
The target acceleration calculating means obtains the target vehicle speed for maintaining the inter-vehicle distance between the preceding vehicle and the host vehicle at a preset target inter-vehicle distance based on the relative vehicle speed. The vehicle travel control apparatus described.

Images