JP6011467B2 - Constant speed travel device - Google Patents

Description

  The present invention relates to a constant speed traveling device that controls the vehicle speed of a vehicle to a set vehicle speed.

  There is known a constant speed traveling device that controls the vehicle speed of a vehicle to a set vehicle speed without a driver operating an accelerator pedal. In the constant speed traveling device, at the time of acceleration (set vehicle speed> vehicle speed) or at the time of deceleration (set vehicle speed <vehicle speed), constant speed traveling is achieved by controlling the throttle opening and increasing / decreasing the driving force by shifting up / down.

  However, it is known that a constant speed traveling device causes so-called shift hunting that frequently shifts up and down on the uphill road or downhill road, and there is a technology for suppressing shift hunting on the uphill road or downhill road. (For example, refer to Patent Document 1). According to Patent Document 1, a downshift is performed under a condition where the vehicle speed deviation is α1 or more, and the running resistance estimated value when the vehicle speed deviation is α2 (where 0 <α2 <α1) is a predetermined value γ from the flat road running resistance. There is disclosed a constant speed traveling device that prohibits downshifting even when the downshifting condition is satisfied when the value is smaller than the reduced value. Further, this constant speed traveling device performs upshifting under the condition that the vehicle speed deviation is not more than a predetermined value α3 (where 0 <α3 <α1) and the estimated running resistance after downshifting is not more than the predetermined value. . As a result, shift hunting during climbing can be prevented, and even when the slope of the climbing path is small, it is possible to reliably shift up.

Japanese Patent Laid-Open No. 10-059015

  However, the shift hunting prevention method described in Patent Document 1 has a problem that shift hunting during downhill cannot be sufficiently suppressed.

FIG. 1 is a diagram for explaining an example of shift hunting.
t1: While traveling on a downhill road, the throttle opening was gradually reduced, but the cruise control control part requested a downshift because the vehicle speed exceeded the set vehicle speed by more than a threshold, and the downshift was made.
t2: The cruise control control unit cancels the downshift request because the vehicle decelerates and approaches the set vehicle speed due to the increase in running resistance.
t3: Shift up by canceling the downshift request. Since the running resistance decreases due to the shift up, the vehicle speed increases even when the throttle opening is fully closed or near the fully closed position.
t4: Shift down again because the vehicle speed exceeds the set vehicle speed by more than the threshold.

  Thereafter, t1 to t4 are repeated, and shift hunting in which upshifting (t3 to t4, t6 to t7) and downshifting (t4 to t6, t7 to t9) are repeated as shown in the drawing occurs. From the viewpoint of the passenger, shift hunting causes a decrease in drivability due to frequent changes in acceleration / deceleration.

  In order to suppress such downhill road shift hunting, it is conceivable to suppress the upshifting and to respond by controlling the throttle opening when acceleration is required.

  However, since the constant speed traveling device cannot know when the downhill road ends (when it is difficult to obtain accurate gradient information from the vehicle position and the road map), the engine speed becomes too high or the fuel consumption is reduced. May decrease. For this reason, another inconvenience occurs only by suppressing the shift-up.

  Therefore, it is considered to shift up when the throttle opening is increased to some extent. A large throttle opening means that a large driving force is required, so even if the vehicle speed becomes higher than the set vehicle speed, it can be decelerated by reducing the throttle opening for a while after the shift up and downshifting. It is because it can respond even if it does not do.

  However, depending on the control system structure, the constant speed traveling device may not always be able to refer to the throttle opening. First, the throttle opening is generally preferentially acquired by an engine control application that performs general engine control (fuel injection control, ignition timing control, etc.). The engine control application often performs feedback control of the throttle opening in accordance with the accelerator opening.

  Here, the application for the constant speed traveling device may be installed in, for example, the engine control unit, but the engine control application and the application for the constant speed traveling device are independent, so the application for the constant speed traveling device is the engine control application. In some cases, the control system structure does not directly refer to the throttle opening. This is due to the development side policy in consideration of the development system of the application and the simplification of the I / F structure between the applications. Therefore, physically, the application of the constant speed traveling device may acquire the throttle opening. Is possible. However, a development period for improving the engine control application is required. In addition, the control system structure becomes complicated.

  As described above, when the conventional constant speed traveling device has a control system structure that does not refer to the throttle opening, it is necessary to suppress shift hunting during traveling on a downhill road and to determine upshifting at an appropriate timing.

  In view of the above problems, an object of the present invention is to provide a constant-speed traveling device that can effectively suppress shift hunting that occurs during traveling on a downhill road and that can determine shift-up timing.

The present invention relates to a constant speed traveling device having a target vehicle speed setting receiving unit that receives a setting of a target vehicle speed and a target driving force determination unit that determines a target driving force for the host vehicle to travel at the target vehicle speed. Based on the stored driving force lower limit value for each gear ratio, based on the target driving force and the driving force lower limit value of the gear ratio smaller than the current time, shift-up control means for upshifting , Based on the driving force lower limit value determining means for determining the output possible driving force lower limit value for each gear ratio, and when a downshift occurs when traveling downhill, the driving force lower limit value determining means is determined immediately before the downshift. And a driving force lower limit value storing means for storing each driving force lower limit value by speed ratio, and when a downshift occurs when traveling on a downhill road, the driving force is within a predetermined time immediately before the downshifting. Noise removal means for performing noise removal processing on the plurality of driving force lower limit values determined by the limit value determining means, and the noise removal means is configured to remove noise. The shift power control unit stores the driving force lower limit value, and the shift-up control unit exceeds the driving force lower limit value of the gear ratio smaller than the current time read from the gear ratio specific driving force lower limit value storing unit. There is provided a constant speed traveling device characterized by shifting up in some cases .

  To provide a constant speed traveling device that can effectively suppress shift hunting that occurs during traveling on a downhill road and that can determine the upshift timing.

It is a figure explaining an example of shift hunting. It is an example of the figure explaining schematic operation | movement of the constant-speed traveling apparatus of this embodiment. It is an example of the block diagram of a constant-speed traveling apparatus. It is an example of a functional block diagram of an engine ECU. It is an example of the flowchart figure which shows the procedure until calculating a target drive force. It is an example of the functional block diagram of the present gear stage driving force lower limit calculation part. It is a figure which shows an example of each map. It is an example of the functional block diagram of the driving force lower limit learning part according to gear stage. It is an example of a functional block diagram of a shift determination unit. It is an example of the figure explaining the temporal transition of the gradient, the vehicle speed, the driving force lower limit of the gear stage g, the cruise request driving force, and the gear stage. It is an example of the flowchart figure which shows the process sequence of a constant speed traveling apparatus.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 2 is an example of a diagram illustrating a schematic operation of the constant speed traveling device of the present embodiment.
(1) It is assumed that the vehicle is equipped with a constant speed traveling device and is traveling at a constant speed with a predetermined gear stage (for example, four stages) by the constant speed traveling device. The gear stage is a gear ratio, and the transmission of this vehicle is, for example, an automatic transmission with a forward speed of five. Conventionally, the constant speed traveling device compares the vehicle speed with the set vehicle speed and calculates the required cruise driving force required for constant speed traveling.

One feature of the constant speed traveling device of the present embodiment is that the driving force lower limit value of each gear stage is calculated during constant speed traveling. The driving force lower limit value is the smallest driving force that can be realized at the gear stage, and is obtained from the engine speed or the like. The driving force lower limit value is a negative value as will be described later. Therefore, the smallest driving force that can be realized by the gear stage mainly means the strongest braking force by the engine brake that is realized by the gear stage.
(2) If the vehicle speed becomes higher than the set vehicle speed because the vehicle travels on a downhill road, the constant speed traveling device shifts down. Since the gear was shifted down from the 4th speed, the vehicle would run at the 3rd speed. After this, conventionally, there has been a shift up to the fourth speed, but in this embodiment, the shift is not performed until the following condition is satisfied.
(3) When the downhill road approaches the end of the downhill road and becomes gentle, the cruise demand driving force gradually increases to maintain the set vehicle speed (the throttle opening gradually increases). Therefore, the increase in the cruise demand driving force may be possible to shift up with respect to the slope of the downhill road.

  However, depending on the timing of the upshift, if the cruise demand driving force is weaker than the lower limit of the driving force at the time of upshifting, the engine brake is insufficient and the vehicle speed increases, and the vehicle speed becomes higher than the set vehicle speed. There is a risk of downshifting.

  Therefore, the constant speed traveling device determines that the shift is up when the cruise demand driving force is stronger than the driving force lower limit value F4 of the gear stage after the upshifting (when this relationship is satisfied for a predetermined time or more). As a result, even if the vehicle is upshifted, the cruise demand drive force does not fall below the engine brake that can realize the gear stage after the upshift, so that the vehicle is not likely to increase in speed and can run at a constant speed.

  Therefore, the constant speed traveling device of this embodiment does not shift up until the cruise demand driving force becomes larger than the driving force lower limit value of the gear stage after the shift up when downshifting while traveling on the downhill road. Shift hunting during traveling can be suppressed. In addition, the constant speed traveling device of the present embodiment shifts up when the cruise demand driving force becomes larger than the driving force lower limit value of the gear stage after the upshift, so that the end of the downhill road is accurately detected and the upshift is performed again. Shifting down can also be suppressed. In addition, since the constant speed traveling device of the present embodiment compares the driving force lower limit value stored in advance for each gear and the cruise request driving force, it is not necessary to be able to refer to the throttle opening.

[Configuration example]
FIG. 3 shows an example of a configuration diagram of the constant speed traveling device of the present embodiment. The constant speed traveling device 100 is controlled by an engine ECU (Electronic Control Unit) 15. The engine ECU 15 includes a microcomputer 22, an input circuit 21, an output circuit 23, a communication controller 24, and the like. The microcomputer 22 has a general configuration such as a CPU, a RAM, and a ROM, and provides functions such as constant speed traveling control and engine control when the CPU executes a program stored in the ROM.

  The input circuit 21 is connected to a cruise control SW 11, a wheel speed sensor 12, an NE sensor 13, a gear stage sensor 14, and the like. Further, the engine 17 is connected to the output circuit 23, and the transmission ECU 16 is connected to the communication controller 24. The communication controller 24 communicates with other ECUs and sensors via an in-vehicle network based on a communication protocol such as CAN (Controller Area Network), FlexRay, Ethernet (registered trademark), and Lin (Local Interconnect Network).

  The cruise control SW 11 receives a driver's operation on the constant speed traveling device 100. First, the cruise control SW 11 receives ON / OFF of the function when the main switch is pressed. The cruise control SW 11 has, for example, a swingable lever-like shape, and accepts various operations according to the operation direction and operation time. For example, an operation for setting the current vehicle speed as the set vehicle speed, an operation for increasing / decelerating the set vehicle speed by a predetermined speed, and an operation for continuously increasing / decreasing the set vehicle speed according to the swing time are accepted.

  The wheel speed sensor 12 is a sensor that detects the current vehicle speed of the vehicle. The vehicle speed is mainly used for comparison with the set vehicle speed, calculation of acceleration, and the like. You may further connect with the acceleration sensor which detects an acceleration directly. The NE sensor 13 detects the engine speed. The gear stage sensor 14 detects the current gear stage. Instead of using the gear stage sensor 14, the engine ECU 15 may acquire the gear stage by communicating with the transmission ECU 16.

  The transmission ECU 16 controls the gear stage of the transmission in response to a shift request from the engine ECU 15. The engine ECU 15 determines the necessity of shifting by referring to a map in which a shift line for the shift speed is determined with respect to the relationship between the current vehicle speed and the accelerator opening. When a shift is necessary, the transmission ECU 16 is requested to shift. Further, in the present embodiment, the engine ECU 15 makes a request for upshifting when downshifting due to traveling on a downhill road during constant speed traveling.

  A transmission 18 is connected to the transmission ECU 16. The transmission 18 is, for example, an automatic transmission having a plurality of gear stages for forward movement.

  The engine 17 includes a throttle motor 25, a throttle opening sensor 26, and the like. However, the function (application) for controlling the constant speed traveling device 100 in the engine ECU 15 cannot acquire the detection signal of the throttle opening sensor.

  Note that the configuration shown in the drawing is merely an example, and is not necessarily called by the names of the engine ECU 15 and the transmission ECU 16, and these functions may be provided by the ECU or the like. Further, the engine ECU 15 may have the function of the transmission ECU 16 (that is, one certain ECU may have the functions of the engine ECU 15 and the transmission ECU 16). Further, only main sensors and actuators to be connected are shown in the figure.

  FIG. 4 is an example of a functional block diagram of the engine ECU 15 of the present embodiment. The engine ECU 15 mainly includes a cruise control control unit 30 and a transmission control unit 40. The cruise control control unit 30 includes a constant speed travel control unit 31a and a shift up control unit 31b.

<Transmission control unit>
The transmission control unit 40 includes a driving force arbitration unit 41 and a transmission control unit 42. The driving force arbitration unit 41 mediates the mobility of the function that controls the driving force, including the cruise control control unit 30. For example, there is a function of stabilizing the behavior of the vehicle such as ABS (Anti_Lock Braking System), TRC (Traction Control), or ESC (Electronic Stability Control). Further, when the lane departure prevention device suppresses lane departure, there are cases where the yaw moment is given by controlling not only the rotational drive of the steering shaft but also the driving force of each wheel to suppress the yaw rate of the vehicle. Since these control the driving force of each wheel separately, they compete with the cruise request driving force for traveling at a constant speed.

  The driving force arbitration unit 41 mediates the driving force output to the engine 17 based on a predetermined priority order. In general, ABS, TRC, ESC, and the lane departure prevention device have a higher priority than the constant speed traveling control, and therefore, when these functions are activated, the cruise request driving force is discarded.

  The transmission control unit 42 instructs the transmission ECU 16 to change the gear. That is, when the driver performs vehicle speed control with accelerator work, an appropriate gear stage is determined based on the current vehicle speed, acceleration, and accelerator opening. When the cruise control control unit 30 performs constant speed running control, the gear stage is determined based on the current vehicle speed, acceleration, and cruise request driving force. In the present embodiment, the gear change determination unit 37 further instructs the transmission ECU 16 to set the gear stage in response to a gear change request.

<Constant speed running control unit>
The constant speed traveling control unit 31 a includes a set vehicle speed setting unit 32, a target acceleration calculation unit 33, and a target driving force calculation unit 34. These exist in order to travel at a constant speed.

Set vehicle speed setting unit The set vehicle speed setting unit 32 sets (holds) the set vehicle speed received by the cruise control SW 11.

Target Acceleration Calculation Unit and Target Driving Force Calculation Unit FIG. 5 is an example of a flowchart illustrating a procedure for calculating a target driving force. The engine ECU 15 repeats this processing periodically while the main switch of the cruise control SW 11 is ON and the constant speed traveling control is effective.

  The target acceleration calculation unit 33 acquires the current vehicle speed detected by the wheel speed sensor 12 (S10).

Further, the target acceleration calculation unit 33 reads the set vehicle speed from the set vehicle speed setting unit 32, and calculates the speed difference between the set vehicle speed and the vehicle speed (S20).
Speed difference = Set vehicle speed-Vehicle speed Next, the target acceleration calculation unit 33 calculates the target acceleration so that the speed difference becomes zero by feedback control, for example (S30). In the feedback control, PID control or PI control is employed. Feed forward control may be added.
Target acceleration = kp × speed difference + ki × ∫speed difference + kd × d (speed difference) / dt
Next, the target driving force calculation unit 34 calculates the target driving force from the target acceleration (S40). The target driving force is a driving force required for accelerating to the target acceleration. The driving force is F [N], the acceleration is α [m / S ² ], the vehicle weight is M [kg], and F = M × α can be obtained. The vehicle weight M may adopt a fixed value such as vehicle specification information, may estimate the load in the vehicle with a height sensor, or may detect the number of passengers with a seating sensor or the like to correct the vehicle weight M. . Thereby, the driving force F can be calculated more accurately.

  The target driving force determined in this way is output to the driving force arbitration unit 41 of the transmission control unit 40 as a cruise request driving force.

<Shift-up control unit>
The upshift control unit 31b determines whether or not to shift up when shifting down on a downhill road. The shift-up control unit 31 b includes a current gear stage driving force lower limit calculation unit 35, a gear stage-specific driving force lower limit learning unit 36, and a shift determination unit 37. Hereinafter, each function will be described in order based on the flowchart of FIG. Refer to the sequence diagram of FIG. 10 as appropriate.

・ Current gear stage driving force lower limit calculation part (S1, t0 to t1)
FIG. 6 shows an example of a functional block diagram of the current gear stage driving force lower limit calculation unit 35. Based on the engine speed, the current gear stage driving force lower limit calculation unit 35 refers to various maps and determines the current gear stage driving force lower limit value.

  S1-1: The current gear stage driving force lower limit calculation unit 35 includes a map storage unit 351, a gear stage-specific gear ratio storage unit 352, and a driving force lower limit calculation unit 353. The map storage unit 351 stores a NE-ISC air amount map, an air amount-throttle opening map, and a NE-generated torque-throttle opening map.

  7A is an example of an NE-ISC air amount map, FIG. 7B is an example of an air amount-throttle opening map, and FIG. 7C is an NE-generated torque-throttle opening map. It is an example.

  The ISC air amount is the minimum air amount necessary to maintain idle rotation. Therefore, the ISC air amount can be obtained from the engine speed with the NE-ISC air amount map. The ISC air amount is obtained in order to obtain the generated torque (engine torque) when the required throttle opening is fully closed during constant speed traveling.

  By knowing the ISC air amount, the throttle opening in the case of a certain ISC air amount can be obtained from the air amount-throttle opening map. The cruise control control unit 30 of the present embodiment is based on the premise that the current throttle opening cannot be acquired, but this map calculates the throttle opening for realizing the ISC air amount according to the engine speed.

  Further, by knowing the throttle opening, the generated torque can be obtained from the NE-generated torque-throttle opening map using the engine speed. The NE-generated torque-throttle opening map is a three-dimensional map, and holds the relationship between the engine speed and generated torque at each throttle opening (for example, in increments of 1%). Therefore, the generated torque can be obtained from the engine speed and the throttle opening. The region where the generated torque is negative is a region where the engine 17 applies a braking force to the wheel rotation because the throttle opening and the engine speed are low. It can be said that the engine brake is applied.

In FIG. 7, the generated torque is calculated using a map. However, as information processing by the microcomputer 22, a process of calculating the generated torque by appropriately interpolating numerical values from a table in which numerical values are registered is performed. Further, the generated torque may be calculated using a function as follows.
ISC air volume = f1 (engine speed)
Throttle opening = f2 (ISC air volume)
Generated torque = f3 (engine speed, throttle opening)
S1-2: The driving force lower limit calculation unit 353 calculates the current gear stage driving force lower limit value using the generated torque, the gear ratio ρ _g for each gear stage, the tire radius r, and the differential ratio ρ _def . The gear ratio storage unit 352 shown in FIG. 6 stores the gear ratio of each gear stage. The gear ratio is fixed to the transmission 18. An example of the relationship between each gear stage and a gear ratio is shown.
1st gear: 2.9
2nd gear: 1.9
3rd gear: 1.4
4th gear: 1.1
5th gear: 0.8
The current gear stage driving force lower limit value is obtained as follows.
Current gear stage driving force lower limit Fg, min = (ρdef / r) × generated torque × ρg
As described in S1-1, the generated torque obtained in S1-1 is a lower limit torque (minus torque) generated with a minimum air amount at a certain engine speed. Therefore, the current gear driving force lower limit value is, in other words, the upper limit (largest) deceleration torque.

  The driving force lower limit calculation unit 353 periodically calculates the current gear stage driving force lower limit value calculated as described above, and outputs it to the gear stage-specific driving force lower limit learning unit 36.

・ Gear-level driving force lower limit learning unit (S2, t1 to t2)
FIG. 8 shows an example of a functional block diagram of the gear-specific driving force lower limit learning unit 36. The gear-specific driving force lower limit learning unit 36 determines the post-upshift gear step driving force lower limit value based on the gear step and the current gear step driving force lower limit value. The gear stage-specific driving force lower limit learning unit 36 includes a current gear stage driving force lower limit storage unit 361, a noise removal unit 362, and a gear stage-specific driving force lower limit learning value storage unit 363.

S2-1: The current gear stage driving force lower limit storage unit 361 stores the current gear stage driving force lower limit value output from the current gear stage driving force lower limit calculation unit 35. That is, a plurality of current gear stage driving force lower limit values are always stored in the current gear stage driving force lower limit storage unit 361, and the oldest current gear stage driving force lower limit value is obtained based on the newly acquired current gear stage driving force lower limit value. Overwritten in order from the value.
Fg, min (t_n) = {Fg, min (t_ (k-1)), Fg, min (t_ (k-2)), ..., Fg, min (t_0)}
Here, Fg, min (t_n) means a set of current gear stage driving force lower limit values stored in the current gear stage driving force lower limit storage unit 361. Fg, min (t_ (k-1) and the like are elements of the set, and k is the number of the current gear stage driving force lower limit value.

  S2-2: A downshift occurs because the vehicle has traveled downhill. The shift down is apparent from the information from the gear stage sensor 14. In addition, the fact that the vehicle is traveling on a downhill road is detected from the fact that the cruise demand driving force is reduced while the vehicle speed is constant.

  When a downshift occurs, the current gear stage driving force lower limit storage unit 361 outputs all the stored current gear stage driving force lower limit values or the newest predetermined number of current gear stage driving force lower limit values to the noise removing unit 362. To do. For example, when the current gear stage driving force lower limit value is calculated at intervals of 100 milliseconds and the current gear stage driving force lower limit value for 2 seconds is output, 20 current gear stage driving force lower limit values are output to the noise removing unit 362. Is done. Hereinafter, the number of current gear stage driving force lower limit values output to the noise removing unit 362 is k.

  The current gear driving force lower limit value is calculated from the torque determined from the engine opening speed at that time and the throttle opening degree that realizes the ISC air amount at that time (for example, on the curve with the smallest throttle opening degree in the map of FIG. 7C). , Generated torque less than zero

  The noise removing unit 362 removes noise components from the k current gear stage driving force lower limit values.

式（１）は、各現在ギア段駆動力下限値に重み付けｗを乗じてｋ個を合計し、ｋで除算している。したがって、重み付けｗを"１"にすれば、ノイズ除去とは平均を算出する処理である。また、重み付けｗは、例えば新しいものほど大きくなるように設定してもよいし、値が小さい現在ギア段駆動力下限値ほど大きく重みづけしてもよい。

In the formula (1), each current gear stage driving force lower limit value is multiplied by a weight w, and k is totaled and divided by k. Therefore, if the weight w is set to “1”, noise removal is a process of calculating an average. Further, the weight w may be set so as to increase, for example, as a new one, or may be weighted as a lower current gear stage driving force lower limit value.

  The noise removal unit 362 stores the current gear stage driving force lower limit value from which noise has been removed in the gear stage driving force lower limit learning value storage unit 363 as the gear stage driving force lower limit learning value in the gear stage before the occurrence of the downshift. That is, when shifting down from the 4th speed to the 3rd speed, the 4th speed gear-dependent driving force lower limit learning value is stored.

  Thereafter, when shifting up, the fourth speed gear-dependent driving force lower limit learning value is output to the shift determination unit 37. On the other hand, if the vehicle is downshifted on the downhill road, but the vehicle cannot be sufficiently decelerated and the vehicle speed is higher than the set vehicle speed, the vehicle is shifted down again. In this case, since the gear is shifted down from the third speed to the second speed, the current gear stage driving force lower limit calculation unit 35 and the gear stage driving force lower limit learning unit 36 set the third gear stage driving force lower limit learning value to the gear stage. This is stored in the driving force lower limit learned value storage unit 363. In this way, the gear-by-gear driving force lower limit learning value storage unit 363 can store the gear-by-gear driving force lower limit learning value of each gear by downshifting on the downhill road.

  S2-3: The gear-by-gear drive force lower limit learning unit 36 uses the gear-by-gear drive force lower limit learned value stored in the gear-by-gear drive force lower limit learning unit 363 to drive the gear stage g after the upshift of the gear stage g. Output as force lower limit value.

・ Shift determination unit (S3, t2 to t6)
FIG. 9 shows an example of a functional block diagram of the shift determination unit 37. The shift determination unit 37 determines whether to shift (shift up), and outputs a shift request to the transmission control unit 42 when shifting. The shift determination unit 37 includes a driving force comparison unit 371.

  S3-1: The driving force comparison unit 371 compares the cruise request driving force and the post-upshift gear stage driving force lower limit value acquired from the gear stage-specific driving force lower limit learning unit 36 when downshifted on the downhill road.

S3-2: If the cruise request driving force is greater than the gear shift driving force lower limit value after the upshift If the cruise request driving force is greater than the lower gear limit driving force after the upshift for a predetermined time or more, a shift request is made to the transmission controller 42 (Shift up).

S3-3: When the cruise request driving force is equal to or less than the gear position driving force lower limit value after the upshift, no shift request is made to the transmission control unit 42, and the shifted down state is maintained. In other words, the transmission control unit 42 is instructed to maintain the downshifted state (inhibiting the upshifting).

  The lower gear limit after the upshift is the strongest braking force (engine brake) that is expected to be realized after the upshift, so that the cruise required drive force is greater than that, even if the shift is up, the speed does not increase Means that. Since the vehicle speed is not increased, there is no possibility of downshifting again to maintain the set vehicle speed or to decelerate the vehicle.

  Therefore, the constant speed traveling device of the present embodiment can suppress shift hunting while traveling on a downhill road by prohibiting upshifting until the condition of S3-2 is satisfied after downshifting. Further, after the downshift, the upshift is permitted when the condition of S3-2 is satisfied, so it is possible to properly detect the downhill road where the vehicle speed can be maintained at the gear stage, and when the upshift occurs, the downshift or upshift is performed again. Can be suppressed.

[Control example]
FIG. 10 is an example of a diagram for explaining the temporal transition of the gradient, the vehicle speed, the driving force lower limit of the gear stage g, the cruise request driving force, and the gear stage.
t0: Downhill road begins, and the cruise demand driving force starts to decrease with the gear stage g. In order to prevent the vehicle speed from exceeding the set vehicle speed on the downhill road, the throttle opening gradually decreases (not shown), and the cruise request driving force decreases. The current gear stage driving force lower limit value of the gear stage g is always stored periodically.
t1: The cruise demand driving force decreases below the negative value, but the vehicle speed increases due to the slope and starts to become higher than the set vehicle speed.
t2: Since the vehicle speed is higher than the set vehicle speed by a threshold value or more, the transmission control unit 42 shifts down to the gear stage g-1. Since the braking force of the engine brake is increased by the downshift, the cruise request driving force is maintained substantially constant. In addition, the gradient is constant around t2. Note that noise removal of the current gear driving force lower limit value of the current gear stage driving force lower limit storage unit 361 is performed between t1 and t2.
t3: When the vehicle speed decreases due to the downshift and becomes the same as the set vehicle speed, the set vehicle speed is maintained, so the throttle opening is slightly increased and the cruise demand drive force is also slightly increased.
t4: The slope begins to become gentle and the cruise demand driving force gradually increases to maintain the set vehicle speed.
t5: Cruise demand driving force starts to exceed gear stage driving force lower limit Fg, min after upshift.
t6: Since the predetermined time T has elapsed after the cruise request driving force exceeds the post-upshift gear stage driving force lower limit Fg, min, the shift determination unit 37 determines that the gear is shifted up, and the gear stage g is shifted up.

[Modifications, substitution examples, etc.]
-Applicable transmission types The transmission 18 according to the present embodiment has been described as being an automatic transmission (AT), but may be applicable to a CVT (Continuously Variable Transmission). In CVT, since the gear ratio changes continuously, it is difficult to calculate the driving force lower limit value for each gear ratio as in this embodiment, but there is CVT that can indicate a discontinuous gear ratio. Such a CVT can increase and decrease the gear ratio in a discontinuous manner like AT. Accordingly, since the CVT can be handled in the same manner as a multi-stage AT, the shift-up method of the present embodiment can be suitably applied to the constant speed traveling device 100 as in the AT.

  It should be noted that the speed ratio that increases or decreases in the CVT may be the difference in the speed ratio between the gears of the AT, or the smaller speed ratio difference can be defined as a single shift amount by taking advantage of the characteristics of the CVT. Good.

-Information required for the driving force lower limit calculation unit 353 The engine speed is required for the current gear stage driving force lower limit calculation unit 35 to calculate the current gear stage driving force lower limit value. However, the engine speed can be obtained from information other than the engine speed.

The rotational speed of the engine 17 is decelerated by the transmission 18 and the differential and transmitted to the drive wheels. The rotational speed of the engine 17 is the same as the rotational speed of the input shaft, and the rotational speed of the drive wheel is the same as the rotational speed of the output shaft. The speed reduction ratio of the differential is a fixed value, and the speed reduction ratio of the transmission 18 is determined by the current gear stage. That is, the following holds.
Input shaft rotation speed = reduction ratio x differential ratio x output shaft rotation speed Therefore, in addition to engine rotation speed, the input shaft rotation speed can be detected by a sensor, or the output shaft rotation speed can be detected by a sensor. The number of revolutions can be determined.

-About adaptive cruise control (ACC) In this embodiment, the upshift condition after the downshift which occurred when the constant speed traveling apparatus 100 traveled at a constant speed on the downhill road was described. However, this shift-up condition can also be suitably applied to ACC.

  First, in ACC, when the preceding vehicle is not supplemented by a radar or a camera, the vehicle speed is controlled to the constant speed of the set vehicle speed in the same manner as the constant speed traveling device 100.

  Further, although the preceding vehicle is supplemented, when the preceding vehicle accelerates on the downhill road and exceeds the set vehicle speed, it is the same as when the preceding vehicle does not exist. Further, when the preceding vehicle does not exceed the set vehicle speed even when accelerating on the downhill road, a downshift may occur if the preceding vehicle is traveling at a substantially constant speed. When downshifting, the conditions for upshifting in this embodiment can be applied. Therefore, the upshift condition of the present embodiment can be suitably applied to ACC.

11 Cruise control SW
12 Wheel speed sensor 13 NE sensor 15 Engine ECU
Reference Signs List 17 engine 18 transmission 30 cruise control control unit 35 current gear stage driving force lower limit calculation unit 36 gear stage-specific driving force lower limit learning unit 37 shift determination unit 100 constant speed traveling device

Claims (6)

A target vehicle speed setting receiving means for receiving a target vehicle speed setting;
In a constant speed traveling device having a target driving force determining means for determining a target driving force for the host vehicle to travel at the target vehicle speed,
Upshift control means for performing upshifting based on the target driving force and the driving force lower limit value of the gear ratio smaller than the current time based on the driving force lower limit value for each gear ratio stored in advance,
Driving force lower limit value determining means for determining a driving force lower limit value that can be output for each speed ratio based on the running state;
When a downshift occurs during downhill road driving, the driving force lower limit value determining unit stores the driving force lower limit value determined immediately before the downshifting according to the gear ratio,
Noise reduction means for performing noise removal processing on the plurality of driving force lower limit values determined by the driving force lower limit value determining means within a predetermined time immediately before downshifting when downshifting occurs during downhill travel; Have
The driving force lower limit value storage means by speed ratio stores the driving force lower limit value from which noise has been removed by the noise removing means,
The shift-up control means shifts up when the target driving force exceeds the driving force lower limit value of the speed ratio smaller than the current time read from the driving ratio lower limit value storing means by speed ratio. A constant speed traveling device. Before SL upshift control means, during downhill running, perform the upshift based on said driving force lower limit of the target driving force and the current is smaller than the gear ratio,
The constant speed traveling apparatus according to claim 1. The shift-up control means shifts up when the target driving force exceeds the driving force lower limit value of a gear ratio smaller than the current time.
The constant-speed traveling device according to claim 1 or 2, characterized in that. The shift-up control means shifts up when the target driving force continuously exceeds the driving force lower limit value of a gear ratio smaller than the current time for a predetermined time.
The constant speed traveling device according to claim 3 . The shift-up control means shifts up by instructing the automatic transmission to the largest speed ratio among the speed ratios smaller than the current time,
Alternatively, the constant speed traveling device according to any one of claims 1 to 4 , wherein the step-up transmission is shifted up by instructing a discontinuous transmission ratio smaller than the present time. The travel state is defined by the engine speed or by vehicle information for obtaining the engine speed,
The driving force lower limit determining means is performing an operation on the engine rotational speed determines the amount of intake air for idling rotation,
Determine the throttle opening by calculating the intake air amount,
Determining the driving force lower limit value based on the engine speed and the throttle opening;
The constant-speed traveling device according to any one of claims 2 to 5, wherein

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