JP5257382B2 - Vehicle control system - Google Patents

Description

  The present invention relates to a vehicle control system.

  2. Description of the Related Art Conventionally, a fuel cut control technique for stopping fuel supply to an engine during traveling is known. For example, Patent Document 1 discloses a technique for selecting a gear position so that fuel cut is efficiently performed according to a searched road condition when a brake-on determination is made.

Japanese Patent Laid-Open No. 9-166209

  As a condition for permitting the execution of the fuel cut control, there is a case where a range of the engine speed capable of performing the fuel cut control is determined. In this case, even if conditions other than the engine speed are satisfied, the fuel cut control cannot be executed unless the engine speed is set within this range. For this reason, the start of fuel cut control may be delayed, and fuel efficiency may not be sufficiently improved.

  An object of the present invention is to provide a vehicle control system capable of improving fuel consumption in a vehicle capable of executing fuel cut control.

  The vehicle control system of the present invention includes an engine and an automatic transmission that transmits power output from the engine to driving wheels of the vehicle, and a condition that the engine speed exceeds a predetermined speed and that the accelerator is off. When a fuel cut execution condition including the above is satisfied, fuel cut control for stopping the supply of fuel to the engine is executed, and a predetermined predetermined travel is estimated that the accelerator is turned off in front of the vehicle When the environment exists, the speed ratio of the automatic transmission is controlled so that the rotation speed exceeding the predetermined rotation speed can be maintained before the accelerator is turned off.

  In the vehicle control system, when downshifting is performed in the automatic transmission so that the rotation speed exceeding the predetermined rotation speed can be maintained, the intake air amount after the downshift is smaller than the intake air amount of the engine before the downshift. It is preferable to suppress fluctuations in the driving force due to the downshift by reducing.

  In the vehicle control system according to the present invention, when there is a predetermined traveling environment that is presumed that the accelerator is turned off in front of the vehicle, the engine speed that exceeds the predetermined rotational speed before the accelerator is turned off. The gear ratio of the automatic transmission is controlled so that the number can be maintained. Therefore, according to the vehicle control system of the present invention, when the accelerator is actually turned off, the fuel cut control can be started quickly, and the fuel consumption can be improved.

FIG. 1 is a flowchart showing the operation of the vehicle control system according to the embodiment. FIG. 2 is a diagram illustrating a vehicle according to the vehicle control system of the embodiment. FIG. 3 is a diagram illustrating an example of the relationship between the current vehicle speed and the predetermined distance. FIG. 4 is a diagram illustrating an example of the relationship between the inter-vehicle distance and a predetermined traveling environment. FIG. 5 is a diagram illustrating an example of a relationship among the gradient, the corner R, and a predetermined traveling environment. FIG. 6 is a diagram for explaining determination based on a gradient as to whether the probability of idle-on is large. FIG. 7 is a diagram for explaining determination based on the corner R whether the probability of idle-on is large.

  Hereinafter, an embodiment of a vehicle control system according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

(Embodiment)
The embodiment will be described with reference to FIGS. 1 to 7. The present embodiment relates to a vehicle control system capable of executing fuel cut control. FIG. 1 is a flowchart showing the operation of an embodiment of a vehicle control system according to the present invention, and FIG. 2 is a diagram showing a vehicle according to the vehicle control system of the embodiment.

  The vehicle control system according to the present embodiment uses IT information from a navigation device or the like, and in a driving scene where there is a high probability of future accelerator off (idle on) such as before a corner or downhill, immediately after idling on. Downshift or suppress upshift in advance so that the fuel cut can be executed. The fuel consumption can be improved by performing the shift control so that the engine speed capable of executing the fuel cut control is maintained.

The vehicle control system of this embodiment is based on the following (1) to (5).
(1) A vehicle including an internal combustion engine (engine) provided with a supply means for supplying fuel.
(2) An engine control device that can automatically control the fuel injection amount of the engine.
(3) A power transmission mechanism that includes a plurality of clutches or brakes from a power generation source, and converts and connects / disconnects power by controlling the clutches or brakes.
(4) A vehicle equipped with navigation and the like that can recognize the current position and the surrounding road information.
(5) A power transmission mechanism including a sensor or an estimation device that can detect vehicle state information (rotation, vehicle speed, hydraulic pressure, etc.).

The vehicle control system of this embodiment controls a vehicle based on the following (A) to (F).
(A) Using navigation or GPS information, it is detected whether the tip of the road that is currently running is a terrain that may be decelerated, such as down / corner / tollgate.
(B) It is detected whether the distance from the other vehicle is narrowed by an inter-vehicle distance sensor / inter-vehicle communication or the like.
(C) It is calculated whether the possibility (probability) of returning the accelerator in the future from (A) and (B) is high.
(D) If the probability of returning the accelerator in (C) is high, it is determined whether the current engine speed is greater than the F / C return speed.
(E) If the current engine speed is smaller than the F / C return rotation in (D) above, a downshift is performed until it exceeds the F / C return rotation.
(F) In the case of the driving force control control structure, the throttle opening is throttled in accordance with the increase in driving force due to the downshift, and control is performed so as not to cause fluctuations in driving force.

  According to the vehicle control system of the present embodiment, by performing a downshift in advance in a traveling scene with a high probability of returning the accelerator in the future, an immediate F / C can be performed from idling on, and thus fuel efficiency is improved. In addition, since the driver intends to decelerate in the case of accelerator return, according to the vehicle control system of the present embodiment, the engine brake effectiveness and responsiveness are improved by downshifting in advance. In addition, using the latest IT (navigation, inter-vehicle distance sensor, etc.), it is possible to accurately estimate a driving scene with a high probability of returning the accelerator in the future.

  As shown in FIG. 2, the vehicle 1 is provided with an engine 11. An automatic transmission 13 having a torque converter 12 is connected to the engine 11. The driving force of the engine 11 is input to the automatic transmission 13 via the torque converter 12 and transmitted to the driving wheels 16 via the differential gear 14 and the drive shaft 15. That is, the automatic transmission 13 transmits the power output from the engine 11 to the drive wheels 16 of the vehicle 1. In the automatic transmission 13, the gear ratio is automatically controlled by the A / T hydraulic control device 17 in accordance with the driving state of the vehicle. The brake device 18 is controlled by the brake hydraulic pressure control device 19 to brake the vehicle.

  The vehicle 1 is provided with an electronic control unit (ECU) 20 that controls the engine 11, the automatic transmission 13, the brake device 18, and the like. The ECU 20 performs comprehensive control of the engine 11, the automatic transmission 13 (A / T hydraulic control device 17), and the brake device 18 (brake hydraulic control device 19). The engine 11 can function as an acceleration changing unit that changes the acceleration (driving force) of the vehicle by controlling the output torque by being controlled by the ECU 20.

  The vehicle 1 is provided with an accelerator position sensor 21 for detecting an operation amount (accelerator opening) of an accelerator pedal. A signal indicating the accelerator opening detected by the accelerator position sensor 21 is output to the ECU 20. A throttle control valve 23 provided in the intake pipe 22 of the engine 11 can be opened and closed by a throttle actuator 24. The ECU 20 can control the throttle opening of the throttle control valve 23 by the throttle actuator 24 regardless of the accelerator opening.

  The engine 11 is provided with an engine speed sensor 28 that detects the engine speed (engine speed). The vehicle speed sensor 29 detects the vehicle speed of the vehicle. The shift position sensor 30 detects the position (shift position) of the shift lever operated by the driver. The brake operation amount sensor 32 detects the operation amount of the brake device 18. The inter-vehicle distance sensor 33 detects the inter-vehicle distance from the preceding vehicle. The inter-vehicle distance sensor 33 can be, for example, a sensor such as a laser radar sensor or a millimeter wave radar sensor mounted on the front of the vehicle. Signals indicating detection results of the sensors 28, 29, 30, 32, and 33 are output to the ECU 20.

  The ECU 20 has a shift map, determines the gear position of the automatic transmission 13 based on the throttle opening, vehicle speed, and the like, and sets the A / T hydraulic control device 17 so as to establish the determined gear position. Can be controlled.

  The navigation device 50 has a basic function of guiding the host vehicle to a predetermined destination, and includes an ECU 60, an operation unit 51, a display unit 52, a speaker 53, a position detection unit 54, and a map database 55. And an operation history recording unit 56. The ECU 60 of the navigation device 50 is capable of bidirectional communication with the ECU 20.

  The CPU 61 of the ECU 60 performs various arithmetic processes such as a navigation process based on the input information. The ROM 62 of the ECU 60 stores various programs for searching a route to the destination, traveling guidance in the route, determining a specific section, and the like. The RAM 63 is a readable / writable memory.

  The position detection unit 54 includes a GPS receiver, a geomagnetic sensor, a distance sensor, a beacon sensor, and a gyro sensor. The position detection unit 54 detects (positions) the position of the host vehicle and outputs data indicating the detected position of the host vehicle to the ECU 60.

  The map database 55 stores information (map, straight road, curve, uphill / downhill, highway, etc.) necessary for vehicle travel. The map database 55 includes a map data file, an intersection data file, a node data file, and a road data file. The ECU 60 reads out necessary information with reference to the map database 55. The vehicle control system 1-1 according to the present embodiment includes an ECU 20, an engine 11, an automatic transmission 13, and a navigation device 50.

  The ECU 20 performs fuel cut control for stopping the supply of fuel to the engine 11 when a predetermined fuel cut execution condition is satisfied. The fuel cut control execution condition includes a condition that the accelerator is off and a condition that the engine speed Ne exceeds a predetermined speed. Here, the accelerator off indicates that the accelerator opening is a predetermined opening or less, for example, an opening corresponding to full closing. The accelerator on means that the accelerator opening is larger than a predetermined opening. The ECU 20 detects accelerator off and accelerator on, for example, based on the detection result of the accelerator position sensor 21.

  The predetermined rotational speed is set as a threshold value of the engine rotational speed at which fuel cut control can be performed. If the engine speed Ne becomes equal to or lower than the predetermined speed during execution of the fuel cut control, the fuel cut control is terminated. That is, the predetermined rotation speed is a return rotation speed from the fuel cut control.

  In order to perform fuel cut control positively and improve fuel efficiency, it is desirable to be able to execute immediate fuel cut control when the accelerator is off. Patent Document 1 discloses a technique for selecting a gear position so as to follow a fuel-cut gear shifting pattern when a brake-on determination is made. However, a certain amount of time is required until the gear position is selected and the shift is completed and the fuel cut control can be executed. In addition, since the time has elapsed from when the accelerator is turned off to when the brake is turned on, the start of fuel cut control is delayed.

  The ECU 20 according to the present embodiment, when there is a predetermined traveling environment that is presumed that the accelerator is turned off in front of the vehicle 1, has an engine rotational speed Ne that exceeds the predetermined rotational speed before the accelerator is turned off. So that the transmission ratio of the automatic transmission 13 is controlled. In a situation where the accelerator is likely to be turned off, the engine speed Ne is not lowered below a predetermined speed in preparation for the accelerator off in advance. Control can begin. Thereby, compared with the case where fuel cut control can be executed by adjusting the engine speed Ne after the accelerator is turned off, the time during which the fuel cut control can be executed is increased, and the fuel consumption can be improved.

  The predetermined traveling environment estimated that the accelerator is off is set in advance based on, for example, the corner radius, the gradient of the traveling road, the inter-vehicle distance, and the like. When the front corner radius of the vehicle 1 is small, when the slope (inclination degree) of the downhill road ahead is large, or when the inter-vehicle distance from the preceding vehicle is small, it can be estimated that the probability of returning the accelerator in the future is high. When such a traveling environment is present in front of the vehicle 1, the ECU 20 performs shift control so that the engine speed Ne can be maintained by shifting down or suppressing the shift-up and maintaining the engine speed Ne exceeding a predetermined speed. In the following description, the speed change control for controlling the speed ratio of the automatic transmission 13 so that the engine speed Ne exceeding the predetermined speed can be maintained is also referred to as “rotation speed maintenance control”.

  The ECU 20 executes the rotation speed maintaining control when a predetermined traveling environment exists in front of a predetermined distance (or a position reached after a predetermined time). The predetermined distance and the predetermined time are determined in consideration of a delay time from the shift command to the end of the shift, and so as not to cause a reduction in fuel consumption due to traveling at a low gear ratio for a long time. For example, the predetermined time is any time from 2 seconds to 10 seconds, and the predetermined distance is a travel distance when traveling at a current vehicle speed for a predetermined time.

  FIG. 3 is a diagram illustrating an example of the relationship between the current vehicle speed and the predetermined distance. For example, when the predetermined time is 2 seconds, the predetermined distance when traveling at 100 km / h is determined to be 55 m. In this case, the ECU 20 executes (starts) the rotation speed maintaining control when a preceding vehicle is present at a position 55 m ahead (may be within 55 m ahead) while traveling at a vehicle speed of 100 km / h on an expressway or the like. Thereby, for example, when the driver feels that the inter-vehicle distance from the preceding vehicle is small and the accelerator is turned off, the immediate fuel cut control is executed, and the effectiveness and responsiveness of the engine brake are improved. In addition, fuel cut control is executed for as long as possible during deceleration, thereby improving fuel efficiency.

  FIG. 4 is a diagram illustrating an example of the relationship between the inter-vehicle distance and a predetermined traveling environment. In FIG. 4, the horizontal axis represents the vehicle speed, and the vertical axis represents the inter-vehicle distance from the preceding vehicle. Symbol Z1 indicates a zone that is estimated to have a high probability of returning the accelerator. As shown in FIG. 4, even if the inter-vehicle distance is the same as the preceding vehicle, it is not estimated that the probability of returning the accelerator is high at low vehicle speeds, and that the probability of returning the accelerator is high at high vehicle speeds. The Further, as the vehicle speed increases, the zone Z1, which is estimated to have a higher probability of returning the accelerator, expands in the direction in which the inter-vehicle distance increases. When the point determined by the combination of the vehicle speed and the inter-vehicle distance is within the area indicated by the reference sign Z1, it is determined that a predetermined traveling environment exists in front of the vehicle 1.

  FIG. 5 is a diagram illustrating an example of a relationship among the gradient, the corner R, and a predetermined traveling environment. In FIG. 5, the horizontal axis indicates the absolute value of the corner curvature (1 / m), and the vertical axis indicates the gradient. In the gradient, positive indicates an upward gradient, and negative indicates a downward gradient. Symbol Z2 indicates a zone that is estimated to have a high probability of returning the accelerator. If there is a corner at a predetermined distance ahead (or a position that reaches in a predetermined time is a corner), the ECU 20 determines whether the corner corresponds to a predetermined traveling environment based on the correspondence shown in FIG. Judging.

  As shown in FIG. 5, when the gradient is the same, if the corner curvature is large, it is estimated that the probability of returning the accelerator is high. For example, when the slope is 0% (flat road), if the front corner R (corner radius) is 80 m or less, the accelerator is likely to be returned at the corner, and a predetermined traveling environment is present in front of the vehicle 1. It is determined that it exists. When the corners R are the same, it is determined that the probability that the accelerator is returned when the gradient is small is high. For example, when the corner R is 80 m, it is determined that a predetermined traveling environment exists in front of the vehicle 1 if the gradient is 0% or less. In addition, on a downhill road with a slope equal to or less than a predetermined slope, that is, a downhill road with a certain degree of slope, it is estimated that the probability of returning the accelerator is high regardless of whether it is a corner. This predetermined gradient is set to, for example, -4.5%. In addition, at corners where the corner radius is less than or equal to a predetermined radius, it is estimated that there is a high probability of returning the accelerator even if it is an upward gradient. This predetermined radius is set to 80 m, for example.

  It should be noted that whether or not the accelerator return probability is high need not be determined by the combination of the corner R and the gradient, but may be determined independently. For example, the predetermined radius may be constant regardless of the gradient, and it may be determined whether there is a high probability of returning the accelerator depending on whether the corner R is equal to or less than the predetermined radius. It may be determined whether there is a high probability of returning the accelerator depending on whether the slope is equal to or less than a predetermined gradient.

  With reference to FIG. 1, operation | movement of the vehicle control system 1-1 of this embodiment is demonstrated. The control flow shown in FIG. 1 is repeatedly executed, for example, at predetermined intervals while the vehicle 1 is traveling.

  First, in step S1, information is acquired by the ECU 20. The ECU 20 acquires the engine speed Ne detected by the engine speed sensor 28, the current vehicle speed detected by the vehicle speed sensor 29, and the current position of the vehicle 1 measured by the navigation device 50, respectively.

  Next, in step S2, the ECU 20 calculates a corner R, a slope, and an inter-vehicle distance that are several seconds / tens of meters away. Based on the current position acquired in step S1, the ECU 20 calculates a corner R and a gradient at a position that can be reached a predetermined distance ahead or after a predetermined time, and an inter-vehicle distance from the preceding vehicle. Here, a case will be described in which each piece of information on a position that is a predetermined distance ahead of the current position is acquired. The ECU 20 acquires the corner R and the gradient of the road ahead by a predetermined distance from the map database 55 of the navigation device 50 based on the current position acquired in step S1. Further, the ECU 20 acquires the inter-vehicle distance from the preceding vehicle detected by the inter-vehicle distance sensor 33.

  Next, in step S3, the ECU 20 determines whether or not the probability of idling on is high. ECU20 performs determination of step S3 based on the information acquired by step S2. FIG. 6 is a diagram for explaining determination based on a gradient as to whether the probability of idle-on is large. FIG. 6 shows a case where the vehicle 1 is traveling toward a forward downhill. The ECU 20 periodically acquires a gradient of a predetermined distance while the vehicle 1 is traveling. At the P1 point, the gradient of the acquired predetermined distance ahead (P2 point) is equal to or less than the predetermined gradient. At this time, a condition where it is estimated that the probability of returning the accelerator is high is satisfied, that is, a predetermined traveling environment where it is estimated that the accelerator is turned off exists in front of the vehicle 1. Make a decision.

  FIG. 7 is a diagram for explaining determination based on the corner R whether the probability of idle-on is large. FIG. 7 shows a case where the vehicle is traveling toward the front corner on a flat road. The ECU 20 periodically acquires a corner R a predetermined distance away while the vehicle 1 is traveling. At the point P3, the value of the corner R at a predetermined distance ahead (point P4) is equal to or less than the predetermined corner R (predetermined radius). At this time, a predetermined traveling environment presumed that the accelerator is turned off is present in front of the vehicle 1, and the ECU 20 makes an affirmative determination in step S3.

  When determining whether the probability of idling on is large based on the inter-vehicle distance, the ECU 20 determines whether the inter-vehicle distance acquired in step S2 is a predetermined distance (or a predetermined distance or less). The preceding vehicle when the inter-vehicle distance is a predetermined distance is a predetermined traveling environment with a high probability of idle-on. In other words, there is a predetermined traveling environment in which it is estimated that the accelerator is turned off in front of the vehicle 1, and an affirmative determination is made in step S3.

  As a result of the determination in step S3, if it is determined that the probability of idling on is high (step S3-Y), the process proceeds to step S4, and if not (step S3-N), the present control flow returns. .

  In step S4, the ECU 20 determines whether the engine rotation is equal to or lower than the fuel cut return rotation. The ECU 20 performs the determination in step S4 by comparing the engine speed Ne acquired in step S1 with a predetermined return speed from the fuel cut control. As a result of the determination, if it is determined that the engine rotation is equal to or lower than the fuel cut return rotation (step S4-Y), the process proceeds to step S5, and if not (step S4-N), the control flow returns. .

  In step S5, the ECU 20 issues a downshift command. The ECU 20 controls the A / T hydraulic control device 17 so that the target shift speed is established by setting the shift speed one speed lower than the current shift speed as the target shift speed. When the downshift is executed, the determination in step S4 is performed again, and the downshift is repeated step by step until the engine speed Ne exceeds the return speed. Accordingly, the ECU 20 can cause the vehicle 1 to travel at the highest gear position within a range where the engine speed Ne exceeds the return speed. Thereby, since the vehicle 1 can be traveled without increasing the engine speed Ne more than necessary, excessive engine braking is prevented from occurring and the vehicle speed is reduced. Here, it is desirable that the engine rotation speed Ne always exceeds the return rotation speed by the rotation speed maintenance control. However, depending on the traveling state of the vehicle, the engine rotation speed Ne may be temporarily lower than the return rotation speed. . However, since the speed change control is performed so that the engine speed Ne exceeding the return speed can be maintained, the fuel cut control can be started more quickly after idling on than when such speed change control is not performed.

Once an affirmative determination is made in step S3 and the rotation speed maintenance control is started, the rotation speed maintenance control is continuously executed until an end condition for the rotation speed maintenance control as shown below is satisfied.
(A) When the fuel cut control is executed with idling on.
(B) A predetermined traveling environment no longer exists in front of the vehicle.

  Here, when the predetermined traveling environment no longer exists in front of the vehicle in (b), for example, when the vehicle passes a corner or a downhill that is the predetermined traveling environment, the inter-vehicle distance from the preceding vehicle is sufficient. This is the case when the vehicle is enlarged or when the preceding vehicle no longer exists. In addition, the rotation speed maintaining control may be terminated when there is no traveling environment in which the probability of idle-on is large.

  Note that the rotation speed maintaining control of the present embodiment is executed when a predetermined traveling environment exists in front of the vehicle 1, and is also executed during acceleration of acceleration. A low-speed gear ratio is selected so that the engine speed Ne exceeding the return speed during acceleration can be maintained, and the upshift is suppressed, so that whenever the driver returns to the accelerator and idles on, the fuel is cut immediately. Can do. For example, it becomes easier to enter fuel cut control even in an idling on acceleration scene on a downhill road. Further, by suppressing the upshift with respect to fluctuations in the vehicle speed, the shift frequency is reduced and drivability is improved.

  In the rotation speed maintenance control, the ECU 20 performs control so that fluctuations in driving force due to the downshift can be suppressed when the automatic transmission 13 performs a downshift so that the engine rotation speed exceeding the return rotation speed can be maintained. For example, the ECU 20 suppresses fluctuations in the driving force by reducing the intake air amount after the downshift than the intake air amount of the engine 11 before the downshift. The increase in driving force due to the downshift is canceled by the throttle control of the throttle opening so that the power is the same before and after the downshift. Thus, if the same power shift is performed to suppress fluctuations in driving force, the feeling of popping out due to the automatic downshift of the rotation speed maintaining control is suppressed. Further, since the throttle control valve 23 is throttled, fuel consumption is suppressed, and fuel consumption can be improved. Such power control that suppresses fluctuations in driving force may be executed, for example, in a driving force control control structure (such as one in which a target driving force is determined based on a driver's accelerator operation).

  In the present embodiment, the fuel cut control can be reliably performed at the time of idling by downshifting until the engine speed Ne exceeds the return speed (S4, S5). At the time of downshift, instead of shifting one step at a time until the engine rotational speed Ne exceeds the return rotational speed, a target gear position that can be set to the engine rotational speed Ne exceeding the return rotational speed is first determined. The A / T hydraulic control device 17 may be controlled so as to establish the target shift speed.

  In the present embodiment, the automatic transmission 13 is a stepped type, but is not limited thereto, and may be, for example, a continuously variable automatic transmission. Further, the traveling environment for determining whether or not the probability of idling on is high is not limited to the inter-vehicle distance, the gradient, and the corner R, but may be other traveling environments such as a toll gate, a temporary stop, a railroad crossing, and the like.

  As described above, the vehicle control system according to the present invention is useful for a vehicle capable of executing fuel cut control, and is particularly suitable for improving fuel consumption.

1-1 Vehicle Control System 1 Vehicle 11 Engine 13 Automatic Transmission 16 Drive Wheel 17 A / T Hydraulic Control Device 20 ECU
21 Accelerator position sensor 33 Inter-vehicle distance sensor 50 Navigation device

Claims (2)

An engine, and an automatic transmission that transmits power output from the engine to driving wheels of a vehicle,
Fuel cut control is executed to stop fuel supply to the engine when a fuel cut execution condition is satisfied, including a condition that the engine speed exceeds a predetermined speed and a condition that the accelerator is off, and the front of the vehicle When there is a predetermined traveling environment that is presumed that the accelerator is turned off, the automatic transmission can maintain the rotational speed exceeding the predetermined rotational speed before the accelerator is turned off. A vehicle control system for controlling a transmission ratio of the vehicle. When downshifting in the automatic transmission so as to maintain the rotational speed exceeding the predetermined rotational speed, the intake air amount after the downshift is decreased by reducing the intake air amount of the engine before the downshift. The vehicle control system according to claim 1, wherein fluctuation in driving force due to downshift is suppressed.

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