JP2013194689A - Vehicle control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve fuel consumption saving of an engine through power generation control of an alternator and gear shift control of an engine brake, an exhaust brake and a mechanical transmission in order to obtain appropriate deceleration in accordance with a magnitude of slope descending energy of a vehicle.SOLUTION: In a vehicle mounting a mechanical type automatic T/M 2 for automatically performing shift and select operations therein, a vehicle control device includes: a power generation output variable alternator 5; an exhaust brake means; a target deceleration setting means for slope descending control in the case where a vehicle speed and a gradient are equal to or more than prescribed levels; and a target deceleration achievement determination means for determining whether the vehicle achieves target deceleration in accordance with a settlement within an alternator driving load limitation and a load of deceleration by exhaust brake operation. In the case where the target deceleration achievement determination means determines that the vehicle can achieve the target deceleration within the alternator driving load limitation, operation of the exhaust brake is stopped.

Description

  The present invention relates to a control device for a downhill of a vehicle equipped with a mechanical automatic transmission that automatically performs a shift / select operation in accordance with the traveling state of the vehicle.

Conventionally, when a lorry equipped with a diesel engine (hereinafter abbreviated as “engine”) travels downhill, the driver downshifts the exhaust brake and the gear stage of the mechanical transmission according to the slope of the downhill. The service brake (foot brake) is used alone or in combination as appropriate.
This is when the vehicle is going downhill with its own weight (including both cargo and empty vehicles), but depending on the slope, the speed of the vehicle becomes too fast and cannot be controlled by engine brake alone. By operating the exhaust brake, the shift down of the gear stage of the mechanical transmission, the service brake, and the like, the vehicle's potential energy is converted into kinetic energy and heat energy to perform safe driving of the vehicle.

However, converting the potential energy of the vehicle into kinetic energy and heat energy by the descending slope from the top climbing up against the uphill load leads to energy loss.
Japanese Unexamined Patent Application Publication No. 2010-151154 (Patent Document 1) is disclosed as a prior art that uses the energy to improve fuel efficiency.
According to Patent Document 1, when traveling on a gentle downhill, if the target deceleration can be achieved within the load limit of the alternator, the downhill control is performed with the power generation load of the alternator only, and the power generation load of the alternator is If the target deceleration cannot be obtained, the load on the alternator is controlled to the maximum, and the insufficient load torque obtained by subtracting the maximum torque of the alternator from the torque required to achieve the target deceleration is obtained. The shift control of the continuously variable transmission is performed so as to achieve the target input rotation speed.
For this reason, excessive engine speed fluctuations are eliminated by turning on / off the downhill control, and it is possible to reduce the uncomfortable feeling due to a decrease in the engine speed when the acceleration is weak during downhill control.

JP 2010-151154 A

In the prior art, the downhill control of the vehicle is performed only by the power generation load control of the alternator and the shift control (engine brake) of the continuously variable transmission.
However, when there is a large vehicle weight difference between commercial vehicles, especially trucks and other loads, and when the vehicle is empty (no luggage), only alternator power generation load control and continuously variable transmission shift control (engine brake) Then downhill control is not possible.
That is, trucks equipped with diesel engines are equipped with exhaust brakes in almost all vehicles.
Therefore, when the vehicle is empty and the descent slope is gentle, if the alternator power generation control, engine brake, and exhaust brake are activated, the deceleration will be too large and the engine rotation will become unstable and abnormal vibration will occur. To do.
In the case of a loaded vehicle, since the downhill energy of the vehicle is large, there may be a case where the deceleration cannot be obtained only with the alternator power generation control, the engine speed, and the exhaust brake.

  Therefore, the present invention has been made in view of such problems, and in order to obtain an appropriate deceleration depending on the magnitude of the downhill energy of the vehicle, power generation control of the alternator, engine brake, exhaust brake, and mechanical transmission The purpose is to reduce the fuel consumption of the engine by shift control.

The present invention is to achieve such an object, in a vehicle equipped with a mechanical automatic transmission that automatically performs a shift and select operation in accordance with the traveling state of the vehicle.
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
A slope estimation means for estimating the slope of the downhill road surface;
A generator output variable type alternator driven by the engine of the vehicle;
Alternator output adjusting means for adjusting the output of the alternator;
An exhaust brake that is mounted on the exhaust manifold of the engine and stops the flow of exhaust gas to generate braking force;
Exhaust brake operation control means for controlling the operation of the exhaust brake;
Downhill control determining means for determining start of downhill control when the vehicle speed is equal to or higher than a predetermined vehicle speed and the gradient is equal to or higher than a predetermined gradient;
Target deceleration setting means for setting a target deceleration for downhill control from the gradient estimated value and the vehicle speed;
A target deceleration achievement determination means for determining whether or not the target deceleration can be achieved by the alternator drive load limit and a deceleration load by the exhaust brake operation,
If the downhill control determining means determines the start of downhill control, and the target deceleration achievement determining means can achieve the target deceleration within the alternator drive load limit, the exhaust brake operation control means Is characterized in that the operation of the exhaust brake is stopped and the output of the alternator is increased.

  In this invention, when the target deceleration can be achieved within the alternator driving load limit by the target deceleration achievement determination means when descending downhill, the operation of the exhaust brake is stopped. By efficiently converting to the power generation output of the alternator, the charge amount of the in-vehicle battery can be increased, and the power generation driving load during general traveling can be reduced, thereby reducing the fuel consumption of the engine.

  Preferably, in the present invention, when the target deceleration achievement determination means determines that the target deceleration cannot be achieved within the alternator drive load limit, the mechanical automatic transmission is shifted down, It is preferable to increase the power generation load of the alternator by increasing the engine speed.

  With this configuration, the automatic automatic transmission is shifted down, the power generation load of the alternator is increased, and the vehicle deceleration power is converted into an increase in power generation output. The fuel consumption of the engine can be further reduced by increasing the amount and reducing the power generation driving load during general traveling.

  Preferably, in the present invention, when the target deceleration achievement determining means determines that the target deceleration cannot be achieved within the alternator drive load limit, the exhaust brake operation control means performs the operation of the exhaust brake. It is good to start.

  With this configuration, the target deceleration is achieved by the alternator drive load and the deceleration load due to the exhaust brake operation, thereby reducing the frequency of service brake use and reducing vehicle deceleration changes. Thus, the ride comfort of the driver can be improved.

  Further, in the present invention, preferably, a determination means for determining whether or not the power output from the alternator can be charged to the battery is provided, and when the charge is possible, the output of the alternator is adjusted.

  In this way, by providing the chargeability determination means for determining whether or not the battery can be charged, it is possible to prevent the evaporation of the electrolyte caused by the overcharged state of the battery and the occurrence of sulfation to the battery electrode plate. The performance can be maintained.

In the present invention, preferably, in a vehicle equipped with a mechanical automatic transmission that automatically performs a shift and select operation in accordance with the traveling state of the vehicle,
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
A slope estimation means for estimating the slope of the downhill road surface;
A generator output variable type alternator driven by the engine of the vehicle;
Alternator output adjusting means for adjusting the output of the alternator;
An exhaust brake that is mounted on the exhaust manifold of the engine and stops the flow of exhaust gas to generate braking force;
Exhaust brake operation control means for controlling the operation of the exhaust brake;
Downhill control determining means for determining start of downhill control when the vehicle speed is equal to or higher than a predetermined vehicle speed and the gradient is equal to or higher than a predetermined gradient;
Target deceleration setting means for setting a target deceleration for downhill control from the gradient estimated value and the vehicle speed;
A target deceleration achievement determination means for determining whether or not the target deceleration can be achieved by the alternator drive load limit and a deceleration load by the exhaust brake operation,
Based on the setting value of the target deceleration setting means, the step of selecting either deceleration by the load of the alternator or deceleration by the combined use of the alternator load and the exhaust brake, and setting of the target deceleration setting means A target deceleration achievement determination step for determining whether or not the deceleration can be achieved may be provided.

  By adopting such a method, a step of selecting a deceleration method based on the set value of the target deceleration setting means and a step of determining whether or not the target deceleration can be achieved are provided. The range of deceleration can be ensured reliably, and it is safe and can be applied to commercial vehicles with a large difference in the weight ratio.

When the target deceleration can be achieved within the alternator drive load limit during downhill, the exhaust brake operation is stopped so that the vehicle deceleration power is output from the alternator. Therefore, the fuel consumption of the engine can be reduced by increasing the charge amount of the in-vehicle battery and reducing the power generation drive load during general traveling.
The target deceleration is achieved by the alternator drive load and the deceleration load caused by the exhaust brake operation, thereby reducing the frequency of use of the service brake, reducing the vehicle deceleration change, and improving the ride comfort of the driver. be able to.

The schematic block diagram which shows embodiment of this invention is shown. The conceptual explanatory view of the 1st load torque in the present invention is shown. The conceptual explanatory view of the 2nd load torque in the present invention is shown. The control flow figure in this invention is shown.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specifically described. Only.

FIG. 1 is an overall schematic configuration diagram for carrying out the present invention.
Reference numeral 1 denotes an engine. The engine 1 burns a mixed gas of air and fuel to generate an output, and exhaust gas discharged from the combustion chamber 12 is introduced to the side of the engine 1. An exhaust manifold 11 is mounted.
A mechanical automatic transmission 2 (hereinafter referred to as “mechanical automatic T / M”) is connected to the rear of the engine 1 via a clutch 6.
Further, an alternator 5 that generates power by being driven by a drive belt 51 wound around a pulley (not shown) directly connected to a crankshaft (not shown) of the engine 1 is disposed on the side of the engine 1.
Reference numeral 8 denotes a battery, which stores the electric power generated by the alternator 5.
3 is a control device. The control device 3 includes an engine 1, a mechanical automatic T / M 2 operation status, an alternator 5, a battery 8, a vehicle speed sensor 31 that is a vehicle speed detection unit, and a gradient sensor that is a gradient estimation unit that estimates a road surface gradient during vehicle travel. They are controlled based on information from 32 etc.

An exhaust brake device 7 is disposed on the exhaust manifold 11 downstream side of the exhaust manifold 11. The exhaust brake device 7 stops the flow of exhaust gas in the exhaust manifold 11 and applies a load when a piston (not shown) in the combustion chamber 12 slides upward, and opens and closes the butterfly valve 72. And an actuator 71. Operation control of the actuator 71 (exhaust brake operation control means) is performed by the control device 3.
That is, by applying a load to the upward sliding of the piston, it acts so as to prevent the rotation of the engine 1, so that the hindering force is applied to the mechanical automatic T / M 2 via the clutch 6 (clutch engagement state) and The brake force is transmitted to the tire.

The clutch 6 transmits and blocks the rotational force of the engine 1 to the mechanical automatic T / M2.
Further, the mechanical automatic T / M2 is selected and shifted by the shift actuator 21 so that the optimum driving state is achieved in accordance with the traveling state (vehicle speed, load) of the vehicle.
The shift actuator 21 provided in the mechanical automatic T / M2 performs the gear shift operation of the mechanical automatic T / M2, that is, select shift, with the clutch 6 disengaged based on the command of the control device 3. It is supposed to be. Reference numeral 33 denotes a clutch sensor which detects the disengagement or engagement state of the clutch 6 and inputs the result to the control device 3 to control the disengagement / engagement of the clutch 6.
Incidentally, the mechanical automatic T / M2 is an existing technology, for example, disclosed in Japanese Patent Laid-Open No. 8-240230. Therefore, detailed description thereof is omitted in the present invention.

The alternator 5 is a variable load type that can adjust the output based on a command from the control device 3.
By changing the required power generation amount by the control device 3, the power generation load can be electrically controlled (alternator output adjusting means).
That is, by suppressing the power generation amount, the load on the engine 1 can be reduced, and by increasing the power generation amount, the load on the engine 1 can be increased and the resistance of the rotational force of the engine 1 can be increased.
As means for varying the amount of power generation, it is possible to use means known in the art such as controlling the strength of an excitation circuit for power generation.

FIG. 4 shows a control flow diagram of the present invention.
This will be described in detail with reference to FIG. Starting in step S1, when the vehicle enters a downhill state in step S2, the driver stops depressing the accelerator pedal. The exhaust brake operates when the clutch is ON (connected).
In general, the exhaust brake device 7 stops operating when the accelerator brake or the clutch pedal is depressed.
Therefore, the exhaust brake does not operate during general traveling.
Further, in the state of step S1, the exhaust brake device 7 + engine brake is operated at the fuel injection amount 0 (zero).
The engine brake means that the engine 1 is rotated from the tire side via the mechanical transmission when the accelerator is depressed (the clutch is in a connected state) when the vehicle is in a downhill state or an inertial force traveling state. It means that it is in the state where the load to act acts. Acts to cause deceleration in the vehicle.
Therefore, since the engine brake operation occurs without any special operation, the control flow in FIG. 4 shows the state in which the engine brake is included in each step for explaining the deceleration element. In order to prevent complication, the expression of engine brake is omitted.

In step S3, based on the detection signals of the vehicle speed sensor 31 and the gradient sensor 32, it is determined whether or not to perform downhill control (downhill control determination means).
This is to prevent the vehicle speed from increasing depending on the vehicle speed and the road surface gradient, so that safe driving cannot be maintained.
If it is determined in step S3 that downhill control is to be performed, Yes is selected and the process proceeds to step S4.
When it is determined that the downhill control is not performed, that is, when it is determined that the vehicle speed does not increase, No is selected and the process returns to step S2.

In step S4, a target deceleration is set (target deceleration setting means) based on detection signals from the vehicle speed sensor 31 and the gradient sensor 32.
Proceeding to step S5, the magnitude of the target deceleration is determined at step S5.
Accordingly, in step S5, it is determined whether the target deceleration can be achieved with the current deceleration means (state of step S2) (step of selecting a deceleration method).
If it is determined in step S5 that the target deceleration can be achieved, Yes is selected and the process proceeds to step S6.

In step S6, it is determined whether a load within the output adjustment limit of the alternator 5 can be used instead of the exhaust brake (target deceleration achievement determination step).
If it is determined that load adjustment within the output adjustment limit of the alternator 5 can be substituted, Yes is selected and the process proceeds to step S7.
On the other hand, if No is selected in step S6, that is, if it is determined that the target deceleration cannot be obtained only with the load within the alternator output limit, the process proceeds to step S8.
In step S8, it is determined whether or not the shift speed of the mechanical automatic T / M2 has been shifted down.
This is because the rotation of the vehicle from the tire side causes the rotation of the engine 1 to increase due to the shift down of the mechanical automatic T / M2, and the power generation output of the alternator 5 increases to the engine 1 due to the shift down. This is intended to increase the load.
If it is determined in step S8 that the mechanical automatic T / M2 shift stage is shifted down to the first stage so that substitution is possible (target deceleration achievement determination step), Yes is selected and the process proceeds to step S9. A downshift of the first stage of the stage is performed.
Then, the process proceeds to step S7.
On the other hand, if it is determined in step S8 that substitution is not possible even if the first-stage downshift is performed, the process proceeds to step S12, and the current exhaust brake operation state (including engine brake) is continued.

FIG. 2 is a conceptual explanatory diagram of the load torque in step S6 and step S8.
The horizontal axis shows the engine speed rpm, the vertical axis shows the engine torque on the upper side, the engine brake on the lower side, and the load torque driven by the alternator 5 drive.
Point A indicates a normal running state based on engine output, which is a downhill road, and the load changes while the engine speed remains unchanged.
That is, the point B indicates a position where it is determined that a load within the output adjustment limit of the engine brake + alternator 5 can be substituted, and Yes is selected in step S6.
Point C indicates the case where No is selected in step S6, and the case where it is determined that substitution is possible in step S8.
That is, by shifting down the mechanical automatic T / M, the position changes from the C position to the D position. Since the load horsepower does not change (load equivalent horsepower curve), the load torque decreases as the rotation speed increases.
Accordingly, the point D is positioned within the output adjustment limit of the engine brake + alternator 5, and Yes is selected in step S8.

In step S7, it is determined whether or not further charging is possible from the charged state of the battery 8.
This is because, when the battery 8 is in an overcharged state, evaporation of water in the electrolyte and sulfation in which crystals of the electrolyte adhere to the battery electrode plate occur. These phenomena reduce the performance of the battery 8 and shorten the life. Therefore, the occurrence of these phenomena is prevented and the performance of the battery 8 is maintained.
If it is determined that the battery 8 can be charged, the process proceeds to step S10.
In step S10, the control device 3 transmits a command for optimal power generation output within the output adjustment limit of the alternator 5, and starts charging the battery 8 in step S11.
On the other hand, if the battery 8 cannot be charged in step S7, No is selected and the process proceeds to step S12.

If No is selected in step S5, if it is determined that it is difficult to achieve the target deceleration with only the exhaust brake, the process proceeds to step S13 to determine whether or not the foot brake is necessary.
This indicates that the target deceleration cannot be obtained unless the foot brake (service brake) is used (deceleration method selection step).
If Yes is selected in step S13, the process proceeds to step S14.

In step S14, it is determined whether a load within the output adjustment limit of the exhaust brake + alternator 5 can be used instead of the foot brake (target deceleration achievement determination step).
If it is determined that the load within the output adjustment limit of the engine brake + exhaust brake + alternator 5 can be substituted, Yes is selected and the process proceeds to step S15.
On the other hand, if No is selected in step S14, the process proceeds to step S16.
In step S16, it is determined whether or not the shift stage of the mechanical automatic T / M2 is shifted down to the first stage.
This is intended to increase the load on the engine 1 as the power generation output of the alternator 5 increases.
If it is determined in step S16 that the mechanical automatic T / M2 shift stage is shifted down to the first stage so that substitution is possible (target deceleration achievement determination process), Yes is selected and the process proceeds to step S17. A downshift of the first stage of the stage is performed.
Then, the process proceeds to step S15.
On the other hand, even if the first-stage downshift is performed in step S16, if substitution is not possible, No is selected and the process proceeds to step S20.

FIG. 3 is a conceptual diagram in which the horizontal axis represents the engine speed rpm, the vertical axis represents the engine torque on the upper side, the lower side represents the engine torque, the alternator 5 drive, and the load torque by the exhaust brake.
Point A indicates a normal running state based on engine output, which is a downhill road, and the load changes while the engine speed remains unchanged.
That is, the point B indicates a position where it is determined that the engine brake + the load within the output adjustment limit of the alternator 5 + the exhaust brake can be substituted, and Yes is selected in step S14.
Point C indicates the case where No is selected in step S14, and the case where it is determined that substitution is possible in step S8.
That is, by shifting down the mechanical automatic T / M, the position changes from the C position to the D position. Since the load horsepower does not change (load equivalent horsepower curve), the load torque decreases as the rotation speed increases.
Accordingly, the point D is positioned within the output adjustment limit of the engine brake + the high brake + the alternator 5, and “Yes” is selected in step S16.

In step S15, it is determined whether or not further charging is possible from the state of charge of the battery 8. Since the reason is the same as that in step S7, the description is omitted.
If it is determined that the battery 8 can be charged, the process proceeds to step S18.
In step S18, the control device 3 transmits a command for optimal power generation output within the output adjustment limit of the alternator 5, and starts charging the battery 8 in step S19.
On the other hand, if the battery 8 cannot be charged in step S15, No is selected and the process proceeds to step S20.

When No is selected in step S13, if it is determined that it is difficult to achieve the target deceleration with only the foot brake, the process proceeds to step S20, and it is determined whether engine brake + foot brake + exhaust brake is necessary.
This indicates that the target deceleration cannot be obtained unless the foot brake (service brake) + exhaust brake + engine brake is used (step of selecting a deceleration method), and the deceleration is required.
If Yes is selected in step S20, the process proceeds to step S21.

In step S21, it is determined whether it is possible to substitute the exhaust brake + the load within the output adjustment limit of the alternator 5 + the engine brake instead of the foot brake (service brake) + the exhaust brake + the engine brake (target deceleration achievement determination step). To do.
If it is determined that the exhaust brake + load within the output adjustment limit of the alternator 5 + engine brake can be substituted (target deceleration achievement determination step), Yes is selected and the process proceeds to step S22.
On the other hand, if No is selected in step S21, the process proceeds to step S23.
In step S23, it is determined whether the gear position of the mechanical automatic T / M2 has been shifted down to a second level deeper than step S16.
This is intended to further increase the power generation output of the alternator 5.
If it is determined in step S23 that the mechanical automatic T / M2 shift stage is shifted down to the second stage to determine that substitution is possible (target deceleration achievement determination process), Yes is selected and the process proceeds to step S24. The second stage downshift of the formula automatic T / M2 is performed. Then, the process proceeds to step S22.
On the other hand, even if the downshift is performed in step S23, if substitution is not possible, No is selected and the process proceeds to step S27 to operate the foot brake and the exhaust brake.

In step S22, it is determined whether or not further charging is possible from the charged state of the battery 8. Since the reason is the same as that in step S7, the description is omitted.
If it is determined that the battery 8 can be charged, the process proceeds to step S25.
In step S25, the control device 3 issues a command for maximum power generation output within the output adjustment limit of the alternator 5, and starts charging the battery 8 in step S26.
On the other hand, if the battery 8 cannot be charged in step S22, No is selected and the process proceeds to step S27, where the foot brake and the exhaust brake are actuated (including engine brake).

In this way, when the target deceleration achievement judging means can achieve the target deceleration within the alternator drive load limit during downhill, the operation of the exhaust brake is stopped and the vehicle deceleration force is stopped. Can be effectively converted into the power generation output of the alternator, and the fuel consumption of the engine can be reduced by increasing the charge amount of the in-vehicle battery and reducing the power generation driving load during general traveling.
In addition, the target deceleration is achieved by alternator drive load and exhaust brake operation, so that the frequency of use of the foot brake (service brake) is reduced, the change in vehicle deceleration is reduced, and the ride quality of the driver is improved. Can also be planned.

  It can be used for a vehicle downhill control device equipped with a mechanical automatic transmission that automatically performs a shift / select operation in accordance with the vehicle's running conditions.

1 Engine 2 Mechanical automatic T / M (mechanical automatic transmission)
3 Control device 5 Alternator 6 Clutch 7 Exhaust brake device (exhaust brake operation control means)
8 Battery 21 Shift actuator 31 Vehicle speed sensor (vehicle speed detection means)
32 Gradient sensor (gradient estimation means)

Claims (5)

In a vehicle equipped with a mechanical automatic transmission that automatically shifts and selects according to the driving situation of the vehicle,
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
A slope estimation means for estimating the slope of the downhill road surface;
A generator output variable type alternator driven by the engine of the vehicle;
Alternator output adjusting means for adjusting the output of the alternator;
An exhaust brake that is mounted on the exhaust manifold of the engine and stops the flow of exhaust gas to generate braking force;
Exhaust brake operation control means for controlling the operation of the exhaust brake;
Downhill control determining means for determining start of downhill control when the vehicle speed is equal to or higher than a predetermined vehicle speed and the gradient is equal to or higher than a predetermined gradient;
Target deceleration setting means for setting a target deceleration for downhill control from the gradient estimated value and the vehicle speed;
A target deceleration achievement determination means for determining whether or not the target deceleration can be achieved by the alternator drive load limit and a deceleration load by the exhaust brake operation,
If the downhill control determining means determines the start of downhill control, and the target deceleration achievement determining means can achieve the target deceleration within the alternator drive load limit, the exhaust brake operation control means Stops the operation of the exhaust brake and increases the output of the alternator.   If the target deceleration achievement determining means determines that the target deceleration cannot be achieved within the alternator driving load limit, the mechanical automatic transmission is shifted down to increase the engine speed. 2. The vehicle control device according to claim 1, wherein a power generation load of the alternator is increased.   When the target deceleration achievement determining means determines that the target deceleration cannot be achieved within the alternator driving load limit, the exhaust brake operation control means starts the operation of the exhaust brake. The vehicle control device according to claim 1 or 2.   2. The vehicle control method according to claim 1, further comprising chargeability determination means for determining whether or not the electric power output from the alternator can be charged into a battery, and adjusting the output of the alternator when charging is possible. In a vehicle equipped with a mechanical automatic transmission that automatically shifts and selects according to the driving situation of the vehicle,
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
A slope estimation means for estimating the slope of the downhill road surface;
A generator output variable type alternator driven by the engine of the vehicle;
Alternator output adjusting means for adjusting the output of the alternator;
An exhaust brake that is mounted on the exhaust manifold of the engine and stops the flow of exhaust gas to generate braking force;
Exhaust brake operation control means for controlling the operation of the exhaust brake;
Downhill control determining means for determining start of downhill control when the vehicle speed is equal to or higher than a predetermined vehicle speed and the gradient is equal to or higher than a predetermined gradient;
Target deceleration setting means for setting a target deceleration for downhill control from the gradient estimated value and the vehicle speed;
A target deceleration achievement determination means for determining whether or not the target deceleration can be achieved by the alternator drive load limit and a deceleration load by the exhaust brake operation,
Based on the setting value of the target deceleration setting means, the step of selecting either deceleration by the load of the alternator or deceleration by the combined use of the alternator load and the exhaust brake, and setting of the target deceleration setting means A vehicle control method comprising a target deceleration achievement determination step for determining whether or not a deceleration of a value can be achieved.

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