Integrated power chain brake control method

Abstract

The application relates to an integrated power chain brake control method, which comprises a preset condition judgment process of constant-speed braking, an integrated brake sub-process and different-cylinder brake sub-processes. The application realizes stepless regulation of brake power by matching IAT and high-power brake linkage, and simultaneously considers the influence of a gearbox gear position on vehicle speed, so that constant-speed downhill driving is realized through gearbox gear position, engine braking and IAT opening degree adjustment. The application realizes high brake power, reduces safety hazards and lowers use cost.

Description

Technical Field

[0001] This invention relates to the field of engine technology, and more specifically to an integrated powertrain braking control method. Background Technology

[0002] Heavy vehicles traveling down long slopes on mining or mountain roads must maintain continuous braking to prevent them from accelerating to dangerous levels under their own weight. This converts potential energy into kinetic energy, which dissipates as heat, thus stabilizing the vehicle's speed at a safe level. Currently, relying solely on the service brakes for braking heavy trucks can easily lead to overheating, reduced braking capacity, severe wear, and even combustion. Even with the installation of water spray systems, numerous safety hazards remain. The rapid development of the automotive industry and the continuous improvement of vehicle performance have made vehicle safety increasingly important. Braking performance is one of the most crucial performance characteristics of a vehicle, directly impacting traffic safety. In Europe and America, the truck accident rate is far lower than in China, a significant reason being the installation of auxiliary braking devices on vehicles.

[0003] Auxiliary braking devices mainly include engine braking, hydraulic retarders, and eddy current retarders. Many vehicles use multiple auxiliary braking devices in combination. Hydraulic retarders are mainly optional based on customer needs, and their cost is relatively high. Furthermore, on long downhill slopes, if the engine cooling system cannot dissipate the retarder's heat in time, the retarder's oil and coolant temperatures will reach the retarder's torque-limiting temperature threshold, resulting in a decrease in braking power. Therefore, how to achieve effective braking on long downhill slopes by increasing engine braking power and selecting appropriate transmission gears, while simultaneously eliminating the need for hydraulic retarders and reducing the cost of auxiliary braking, has become a pressing issue.

[0004] The shortcomings of existing technology are:

[0005] 1. Due to the current technology, if heavy trucks rely solely on the continuous operation of the service brake, it is easy to cause the brake to overheat, brake capacity to decline, wear to become severe, and even cause combustion, thus posing a safety hazard.

[0006] 2. Because existing technologies require the installation of auxiliary braking devices to meet braking requirements, this leads to increased costs.

[0007] 3. Due to the limitations of existing auxiliary braking devices in long downhill conditions, if the engine cooling system cannot remove the heat from the retarder in time, the oil and water temperatures of the retarder will reach the retarder's torque-limiting temperature threshold, resulting in a decrease in braking power. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides an integrated powertrain braking control method, which aims to achieve high braking power, reduce safety hazards, and lower operating costs.

[0009] To solve the above problems, the technical solution provided by the present invention is as follows:

[0010] The integrated powertrain braking control method includes the following steps:

[0011] S100. Determine whether the current vehicle meets the preset conditions for constant speed braking; then, based on the determination result, perform the following operations:

[0012] If the vehicle meets the preset conditions for constant speed braking, then S200 is executed;

[0013] If the vehicle does not meet the preset conditions for constant speed braking, then S100 is executed again;

[0014] S200. Determine if the vehicle driver requires constant speed braking, and then perform the following operations based on the determination result:

[0015] If the driver presses the constant speed brake switch, it is determined that the driver has a need for constant speed braking, and then S300 is executed;

[0016] If the driver does not press the constant speed brake switch, it is determined that the driver does not require constant speed braking, and then the process returns and re-executes S100.

[0017] S300. Determine whether the current vehicle speed is within a manually preset constant speed range, and then perform the following operations based on the determination result:

[0018] If the current vehicle speed is within the constant vehicle speed range, then execute S400;

[0019] If the current vehicle speed is not within the constant vehicle speed range, return and re-execute S100;

[0020] S400. Record the current vehicle speed and set the current vehicle speed as the target speed for a constant vehicle speed;

[0021] S500. Record the current vehicle speed in real time, compare the target speed of the constant vehicle speed with the current vehicle speed, and then perform the following operations based on the comparison result:

[0022] If the current vehicle speed is greater than the target vehicle speed of the constant vehicle speed, and the current vehicle speed exceeds the manually preset integrated braking speed threshold, then execute S600.

[0023] If the current vehicle speed is not greater than the target speed of the constant vehicle speed, or the previous vehicle speed has not exceeded the integrated braking speed threshold, then it is determined that braking is not required at present.

[0024] S600 prioritizes gear shift calculations for the transmission and performs braking calculations based on the current engine speed and current gear position, executing an integrated braking sub-process.

[0025] Preferably, the integrated braking subprocess specifically includes the following steps:

[0026] Sa100. Calculate the first target gear of the transmission and the first target engine speed after downshifting one gear from the current transmission gear position.

[0027] Sa200. Determine whether the target speed of the first engine exceeds the manually preset engine protection speed threshold, and then perform the following operations based on the determination result:

[0028] If the target speed of the first engine exceeds the engine protection speed threshold, the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed.

[0029] If the target speed of the first engine does not exceed the engine protection speed threshold, then Sa300 is executed;

[0030] Sa300. Determine whether the required braking force after downshifting the transmission exceeds the engine's maximum braking force, and then perform the following operations based on the determination result:

[0031] If the required braking force after downshifting the transmission by one gear exceeds the maximum braking force of the engine, then step Sa400 is executed;

[0032] If the required braking force after downshifting one gear does not exceed the maximum braking force of the engine, the transmission will downshift one gear first, and then execute the braking sub-process with different cylinder numbers.

[0033] Sa400. Calculate the second target gear position and the second target engine speed after downshifting two gears from the current gear position;

[0034] Sa500. Determine whether the target speed of the second engine exceeds the engine protection speed threshold, and then perform the following operations based on the determination result:

[0035] If the target speed of the second engine exceeds the engine protection speed threshold, the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed.

[0036] If the target speed of the second engine does not exceed the engine protection speed threshold, then execute Sa600;

[0037] Sa600. Determine whether the required braking force after downshifting two gears in the transmission exceeds the maximum braking force of the engine, and then perform the following operations based on the determination result:

[0038] If the required braking force after downshifting two gears in the transmission exceeds the maximum braking force of the engine, then the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed.

[0039] If the required braking force after downshifting two gears does not exceed the engine's maximum braking force, the transmission will downshift two gears first, and then execute the braking sub-process for different cylinder numbers.

[0040] Preferably, the braking sub-process with different numbers of cylinders specifically includes the following steps:

[0041] Sb100. Determine whether the current required braking force necessitates maximum cylinder braking, and then perform the following operations based on the determination result:

[0042] If the required braking force exceeds the engine's maximum braking force, it is determined that maximum cylinder braking is required, and then Sb200 is executed.

[0043] If the required braking force does not exceed the engine's maximum braking force, it is determined that maximum cylinder braking is not required, and then Sb300 is executed.

[0044] Sb200 performs maximum cylinder braking, while steplessly adjusting the braking force by adjusting the opening of the IAT valve;

[0045] Sb300 applies 1 / 2 cylinder braking, while continuously adjusting the braking force by adjusting the opening of the IAT valve.

[0046] Preferably, the preset condition for constant speed braking is: the vehicle is in a downhill condition and the engine's high-power braking condition is met, wherein:

[0047] The high-power braking conditions are as follows: the engine speed is greater than the manually preset high-power braking speed threshold, the throttle opening is 0, the vehicle speed is greater than the manually preset high-power braking vehicle speed threshold, the boost pressure is greater than the manually preset high-power braking pressure threshold, and the water temperature is greater than the manually preset high-power braking water temperature threshold.

[0048] Preferably, the target speed of the first engine is expressed by the following formula:

[0049] n1=V / (k1×k h ×C×60)

[0050] Where: n1 represents the target speed of the first engine; V represents the current vehicle speed; k1 represents the gear ratio of the transmission downshifting by 1; k h C is used to characterize the rear axle speed ratio; C is used to characterize the tire circumference.

[0051] Preferably, the target speed of the second engine is expressed by the following formula:

[0052] n2=V / (k2×k h ×C×60)

[0053] Where: n2 is used to characterize the target speed of the second engine; k2 is used to characterize the gear ratio of the transmission downshifting by 2 gears.

[0054] Preferably, the required braking force is expressed by the following formula:

[0055]

[0056] Wherein: F T The required braking force is represented by m; vehicle mass is represented by g; g is represented by gravitational acceleration; f is represented by the rolling resistance coefficient; C d A is used to characterize the air drag coefficient; A is used to characterize the frontal area; ρ is used to characterize the air density; V is used to characterize the current vehicle speed.

[0057] Preferably, the air density is 1.293 kg / m³. 3 .

[0058] Preferably, the constant speed range is 45 km / h to 65 km / h.

[0059] Compared with the prior art, the present invention has the following advantages:

[0060] 1. This invention achieves high braking power by controlling the timing sequence of different braking solenoid valves in the engine.

[0061] 2. Because this invention achieves stepless control of braking power by coordinating IAT and high-power braking, and simultaneously considers the influence of gearbox gear on vehicle speed, it achieves constant downhill speed by adjusting gearbox gear, engine braking and IAT opening, thereby reducing safety hazards and lowering operating costs. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the integrated powertrain braking control process according to a specific embodiment of the present invention;

[0063] Figure 2 This is a schematic diagram illustrating the derivation of the braking force required by a vehicle in a downhill condition, according to a specific embodiment of the present invention. Detailed Implementation

[0064] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0065] like Figure 1 As shown, the integrated powertrain braking control method includes the following steps:

[0066] S100. Determine whether the current vehicle meets the preset conditions for constant speed braking; then, based on the determination result, perform the following operations:

[0067] If the vehicle meets the preset conditions for constant speed braking, then S200 is executed.

[0068] If the vehicle does not meet the preset conditions for constant speed braking, then S100 is executed again.

[0069] S200. Determine if the vehicle driver requires constant speed braking, and then perform the following operations based on the determination result:

[0070] If the driver presses the constant speed brake switch, it is determined that the driver has a need for constant speed braking, and then S300 is executed.

[0071] If the driver does not press the constant speed brake switch, it is determined that the driver does not require constant speed braking, and then the process returns and re-executes S100.

[0072] S300. Determine whether the current vehicle speed is within a manually preset constant speed range, and then perform the following operations based on the determination result:

[0073] If the current vehicle speed is within the constant speed range, then execute S400.

[0074] If the current vehicle speed is not within the constant speed range, return and re-execute S100.

[0075] S400. Record the current vehicle speed and set the current vehicle speed as the target speed for a constant vehicle speed.

[0076] S500. Records the current vehicle speed in real time, compares the target speed of the constant vehicle speed with the current speed, and then performs the following operations based on the comparison result:

[0077] If the current vehicle speed is greater than the target speed of the constant vehicle speed, and the current vehicle speed exceeds the manually preset integrated braking speed threshold, then S600 is executed.

[0078] If the current vehicle speed is not greater than the target speed of the constant vehicle speed, or the speed of the vehicle ahead has not exceeded the integrated braking speed threshold, then it is determined that braking is not required at present.

[0079] S600 prioritizes gear shift calculations for the transmission and performs braking calculations based on the current engine speed and current gear position, executing an integrated braking sub-process.

[0080] It should be noted that the integrated braking sub-process specifically includes the following steps:

[0081] Sa100. Calculates the first target gear and the first target engine speed after downshifting one gear from the current gearbox.

[0082] Sa200. Determine whether the target speed of the first engine exceeds the manually preset engine protection speed threshold, and then perform the following operations based on the determination result:

[0083] If the target speed of the first engine exceeds the engine protection speed threshold, the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed.

[0084] If the target speed of the first engine does not exceed the engine protection speed threshold, then execute Sa300.

[0085] Sa300. Determine whether the braking force required after downshifting the transmission by one gear exceeds the engine's maximum braking force, and then perform the following operations based on the determination result:

[0086] If the braking force required after downshifting the transmission by one gear exceeds the engine's maximum braking force, then step Sa400 is executed.

[0087] If the braking force required after downshifting the transmission by one gear does not exceed the engine's maximum braking force, the transmission will downshift first and then execute the braking process for different cylinder numbers.

[0088] Sa400. Calculates the target gear of the second transmission and the target engine speed after downshifting two gears from the current transmission gear position.

[0089] Sa500. Determine whether the target speed of the second engine exceeds the engine protection speed threshold, and then perform the following operations based on the determination result:

[0090] If the target speed of the second engine exceeds the engine protection speed threshold, the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed.

[0091] If the target speed of the second engine does not exceed the engine protection speed threshold, then execute Sa600.

[0092] Sa600. Determine whether the braking force required after downshifting two gears exceeds the engine's maximum braking force, and then perform the following operations based on the determination result:

[0093] If the braking force required after downshifting two gears exceeds the engine's maximum braking force, then the engine's maximum cylinder braking is activated, and the maximum braking force is maintained for braking, and then S500 is executed.

[0094] If the braking force required after downshifting two gears does not exceed the engine's maximum braking force, the transmission will downshift two gears first, and then execute the braking sub-processes for different cylinder numbers.

[0095] It should be noted that the braking sub-process for different numbers of cylinders specifically includes the following steps:

[0096] Sb100. Determine whether the current required braking force necessitates braking with the maximum number of cylinders, and then perform the following operations based on the determination result:

[0097] If the required braking force exceeds the engine's maximum braking force, it is determined that maximum cylinder braking is required, and then Sb200 is executed.

[0098] If the required braking force does not exceed the engine's maximum braking force, it is determined that maximum cylinder braking is not required, and then Sb300 is executed.

[0099] Sb200 applies maximum cylinder braking while continuously adjusting the braking force by regulating the opening of the IAT valve.

[0100] Sb300 applies 1 / 2 cylinder braking, while continuously adjusting the braking force by adjusting the opening of the IAT valve.

[0101] It should be further explained that the braking force of the engine itself was measured through experiments under different speeds and different numbers of cylinders.

[0102] It should be noted that the preset conditions for constant speed braking are: the vehicle is in a downhill condition and the engine's high-power braking conditions are met, including:

[0103] The conditions for high-power braking are: engine speed is greater than the manually preset high-power braking speed threshold, throttle opening is 0, vehicle speed is greater than the manually preset high-power braking vehicle speed threshold, boost pressure is greater than the manually preset high-power braking pressure threshold, and coolant temperature is greater than the manually preset high-power braking coolant temperature threshold.

[0104] It should be further explained that the high-power braking pressure threshold and the high-power braking coolant temperature threshold are formulated based on the actual reliability requirements of engine components; the high-power braking speed threshold and the high-power braking vehicle speed threshold are formulated based on the hardware operating characteristic parameters of the engine brake.

[0105] It should be noted that the target speed of the first engine is expressed according to Equation 1:

[0106] n1=V / (k1×k h ×C×60) (1)

[0107] Where: n1 represents the target speed of the first engine; V represents the current vehicle speed; k1 represents the gear ratio of the transmission downshifting by 1; k h C is used to characterize the rear axle speed ratio; C is used to characterize the tire circumference.

[0108] It should be noted that the target speed of the second engine is expressed according to Equation 2:

[0109] n2=V / (k2×k h ×C×60) (2)

[0110] Where: n2 is used to characterize the target speed of the second engine; k2 is used to characterize the gear ratio of the transmission downshifting by 2 gears.

[0111] It should be noted that the required braking force is expressed according to Equation 3:

[0112]

[0113] Wherein: F T Used to characterize the required braking force; m is used to characterize the vehicle mass; g is used to characterize gravitational acceleration; f is used to characterize the rolling resistance coefficient; C d A is used to characterize the air drag coefficient; A is used to characterize the frontal area; ρ is used to characterize the air density; V is used to characterize the current vehicle speed.

[0114] like Figure 2 As shown, it should be further explained that the required braking force is derived from the vehicle's acceleration formula; the vehicle's acceleration is expressed by Equation 4:

[0115]

[0116] Where: a is used to characterize the acceleration of the vehicle; F W Used to characterize the air resistance experienced by a vehicle; F f θ is used to characterize the rolling resistance experienced by the vehicle; θ is used to characterize the angle of the downhill slope.

[0117] The air resistance is expressed according to Equation 5:

[0118]

[0119] The rolling resistance is expressed according to Equation 6:

[0120] F f =fmg×cosθ (6)

[0121] Substituting equations 5 and 6 into equation 4, we obtain equation 7:

[0122]

[0123] Among them: According to my country's highway design specifications, the gradient of general roads is relatively small, so we can let sinθ≈tanθ=i, cosθ=1; i is used to characterize the gradient of the vehicle going downhill.

[0124] When going downhill at a constant speed, let the acceleration be equal to 0. The formula for the required braking force in Equation 3 can be derived from Equation 7.

[0125] It should be further noted that the air resistance coefficient was determined through testing; the frontal area is related to the windward surface of the entire vehicle; and the rolling resistance coefficient was determined through actual road use testing.

[0126] In this specific embodiment, the air density is taken as 1.293 kg / m³. 3 .

[0127] In this specific embodiment, the constant vehicle speed range is 45km / h to 65km / h.

[0128] In this specific embodiment, the engine protection speed threshold is determined based on engine reliability tests.

[0129] In this specific embodiment, the maximum number of cylinders for braking is 6-cylinder braking, and the 1 / 2 cylinder number braking is 3-cylinder braking.

[0130] It should be further noted that the present invention is also applicable to 4-cylinder engines.

[0131] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0132] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0133] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0134] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An integrated powertrain braking control method, characterized in that: Includes the following steps: S100. Determine whether the current vehicle meets the preset conditions for constant speed braking; then, based on the determination result, perform the following operations: If the vehicle meets the preset conditions for constant speed braking, then S200 is executed; If the vehicle does not meet the preset conditions for constant speed braking, then S100 is executed again; S200. Determine if the vehicle driver requires constant speed braking, and then perform the following operations based on the determination result: If the driver presses the constant speed brake switch, it is determined that the driver has a need for constant speed braking, and then S300 is executed; If the driver does not press the constant speed brake switch, it is determined that the driver does not require constant speed braking, and then the process returns and re-executes S100. S300. Determine whether the current vehicle speed is within a manually preset constant speed range, and then perform the following operations based on the determination result: If the current vehicle speed is within the constant vehicle speed range, then execute S400; If the current vehicle speed is not within the constant vehicle speed range, return and re-execute S100; S400. Record the current vehicle speed and set the current vehicle speed as the target speed for a constant vehicle speed; S500. Record the current vehicle speed in real time, compare the target speed of the constant vehicle speed with the current vehicle speed, and then perform the following operations based on the comparison result: If the current vehicle speed is greater than the target vehicle speed of the constant vehicle speed, and the current vehicle speed exceeds the manually preset integrated braking speed threshold, then execute S600. If the current vehicle speed is not greater than the target speed of the constant vehicle speed, or the previous vehicle speed has not exceeded the integrated braking speed threshold, then it is determined that braking is not required at present. S600 prioritizes gear shift calculations for the transmission, and calculates braking based on the current engine speed and current gear position, and executes an integrated braking sub-process. The integrated braking subprocess specifically includes the following steps: Sa100. Calculate the first target gear of the transmission and the first target engine speed after downshifting one gear from the current transmission gear position; Sa200. Determine whether the target speed of the first engine exceeds the manually preset engine protection speed threshold, and then perform the following operations based on the determination result: If the target speed of the first engine exceeds the engine protection speed threshold, the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed. If the target speed of the first engine does not exceed the engine protection speed threshold, then Sa300 is executed; Sa300. Determine whether the required braking force after downshifting the transmission exceeds the engine's maximum braking force, and then perform the following operations based on the determination result: If the required braking force after downshifting the transmission by one gear exceeds the maximum braking force of the engine, then step Sa400 is executed; If the required braking force after downshifting one gear does not exceed the maximum braking force of the engine, the transmission will downshift one gear first, and then execute the braking sub-process with different cylinder numbers. Sa400. Calculate the second target gear position of the transmission and the second target engine speed after downshifting two gears from the current transmission gear position; Sa500. Determine whether the target speed of the second engine exceeds the engine protection speed threshold, and then perform the following operations based on the determination result: If the target speed of the second engine exceeds the engine protection speed threshold, the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed. If the target speed of the second engine does not exceed the engine protection speed threshold, then execute Sa600; Sa600. Determine whether the required braking force after downshifting two gears in the transmission exceeds the maximum braking force of the engine, and then perform the following operations based on the determination result: If the required braking force after downshifting two gears in the transmission exceeds the maximum braking force of the engine, then the maximum number of cylinders of the engine is engaged for braking, and the maximum braking force is maintained for braking, and then S500 is executed. If the required braking force after downshifting two gears does not exceed the maximum braking force of the engine, the transmission will downshift two gears first, and then execute the braking sub-process for different cylinder numbers. The braking sub-process for different numbers of cylinders specifically includes the following steps: Sb100. Determine whether the current required braking force necessitates maximum cylinder braking, and then perform the following operations based on the determination result: If the required braking force exceeds the engine's maximum braking force, it is determined that maximum cylinder braking is required, and then Sb200 is executed. If the required braking force does not exceed the engine's maximum braking force, it is determined that maximum cylinder braking is not required, and then Sb300 is executed. Sb200 performs maximum cylinder braking, while continuously adjusting the braking force by adjusting the opening of the IAT valve; Sb300 applies 1 / 2 cylinder braking, while continuously adjusting the braking force by regulating the opening of the IAT valve.

2. The integrated powertrain braking control method according to claim 1, characterized in that: The preset conditions for constant speed braking are: the vehicle is in a downhill condition and the engine's high-power braking conditions are met, wherein: The high-power braking conditions are as follows: the engine speed is greater than the manually preset high-power braking speed threshold, the throttle opening is 0, the vehicle speed is greater than the manually preset high-power braking vehicle speed threshold, the boost pressure is greater than the manually preset high-power braking pressure threshold, and the water temperature is greater than the manually preset high-power braking water temperature threshold.

3. The integrated powertrain braking control method according to claim 2, characterized in that: The target speed of the first engine is expressed by the following formula: n1=V / (k1×k h ×C×60) Where: n1 represents the target speed of the first engine; V represents the current vehicle speed; k1 represents the gear ratio of the transmission downshifting by 1; k h C is used to characterize the rear axle speed ratio; C is used to characterize the tire circumference.

4. The integrated powertrain braking control method according to claim 3, characterized in that: The target speed of the second engine is expressed by the following formula: n2=V / (k2×k h ×C×60) Where: n2 is used to characterize the target speed of the second engine; k2 is used to characterize the gear ratio of the transmission downshifting by 2 gears.

5. The integrated powertrain braking control method according to claim 4, characterized in that: The required braking force is expressed by the following formula: Wherein: F T The required braking force is represented by m; vehicle mass is represented by g; g is represented by gravitational acceleration; f is represented by the rolling resistance coefficient; C d A is used to characterize the air drag coefficient; A is used to characterize the frontal area; ρ is used to characterize the air density; V is used to characterize the current vehicle speed.

6. The integrated powertrain braking control method according to claim 5, characterized in that: The air density is 1.293 kg / m³.

7. The integrated powertrain braking control method according to claim 6, characterized in that: The constant speed range is 45km / h to 65km / h.

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