Engine speed reduction method and device, vehicle and storage medium

Abstract

The invention relates to an engine speed reduction method and device, a vehicle and a storage medium, and belongs to the technical field of engine control. The method comprises the steps that the current rotating speed, the target rotating speed, the free speed reduction characteristic information and the expected speed reduction time of an engine are obtained; according to the free speed reduction characteristic information, predicting first time when the engine is freely decelerated from the current rotating speed to the target rotating speed; if the first time is smaller than or equal to the expected deceleration time, controlling the engine to decelerate freely; and if the first time is larger than the expected speed reduction time, first braking information is determined according to the difference value between the first time and the expected speed reduction time, and braking speed reduction is conducted on the engine according to the first braking information. According to the method, the speed reduction time of the engine in the AMT upshift process can be accurately controlled, so that speed reduction of the engine is completed within the expected speed reduction time.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and in particular to an engine speed reduction method, device, vehicle and storage medium. Background Art

[0002] During the upshift process of the Automated Manual Transmission (AMT), the engine speed needs to be reduced from the current speed to the target speed within the target time before the clutch can be engaged to restore power and complete the upshift process.

[0003] During the engine deceleration process, if the deceleration is too fast, in order to maintain the target speed, the engine needs to inject fuel to increase the engine speed, causing additional losses; if the deceleration is too slow, the target time will be extended, the AMT will wait, or the clutch will be forced to engage within the target time, causing jerking during driving. However, the relevant technology does not accurately control the engine deceleration time during the AMT upshift process. Summary of the invention

[0004] In view of this, it is necessary to provide an engine deceleration method, device, vehicle and storage medium to solve the problem that the related technology does not accurately control the engine deceleration time during the AMT upshift process.

[0005] In order to solve the above problems, in a first aspect, the present invention provides an engine speed reduction method, comprising: Obtain the current engine speed, target speed, free speed reduction characteristic information and expected speed reduction time; predicting, based on the free-speed-falling characteristic information, a first time for the engine to freely fall from the current speed to the target speed; If the first time is less than or equal to the expected deceleration time, controlling the engine to decelerate freely; If the first time is greater than the expected deceleration time, first braking information is determined according to a difference between the first time and the expected deceleration time, and the engine is braked and decelerated according to the first braking information.

[0006] Optionally, the free-speed deceleration characteristic information includes a first mapping relationship and a second mapping relationship; the first mapping relationship is a mapping relationship between the speed and the time taken for the speed to freely decelerate to reach the maximum deceleration; the second mapping relationship is a mapping relationship between the speed and time during free deceleration; then, predicting the first time for the engine to freely decelerate from the current speed to the target speed according to the free-speed deceleration characteristic information includes: Predicting, according to the first mapping relationship, a second time required for the engine to freely decelerate from the current speed to reach a maximum deceleration, and a first speed at the maximum deceleration; predicting, according to the second mapping relationship, a third time required for the engine to decelerate from the first speed to the target speed; The first time is calculated according to the following formula: ; in, For the first time, For the second time, For the third time, is the free speed reduction correction factor.

[0007] Optionally, controlling the engine to free-speed down includes: When the engine is decelerated freely to a preset range of the first speed, obtaining a target maximum deceleration within the preset range, a second speed at the target maximum deceleration, and a fourth time required to reach the target maximum deceleration; predicting, according to the second mapping relationship, a fifth time required for the engine to decelerate from the second speed to the target speed, and a target deceleration at the second speed; The sixth time is calculated according to the following formula: , ; in, For the sixth time, For the fourth time, For the fifth time, is the target deceleration, is the target maximum deceleration; After the engine reaches the second speed, if the sixth time is less than or equal to the expected deceleration time, controlling the engine to freely decelerate to the target speed; If the sixth time is greater than the expected deceleration time, second braking information is determined according to the difference between the sixth time and the expected deceleration time, and the engine is braked and decelerated according to the second braking information.

[0008] Optionally, the method further includes: Acquire the actual time taken for the engine to decelerate to the target speed, and the third speed of the engine when the expected deceleration time is reached; If the engine decelerates freely to the target speed and the actual time is less than or equal to the expected deceleration time, the free deceleration correction coefficient is corrected according to the ratio of the actual time to the expected deceleration time; If the engine decelerates freely to the target speed and the actual time is greater than the expected deceleration time, the free deceleration correction coefficient is corrected according to a ratio of the third speed to the target speed.

[0009] Optionally, the first braking information includes a first braking time and a braking time correction coefficient, and the method further includes: If the engine is decelerated to the target speed according to the first braking information, a brake opening delay time is obtained; The braking time correction coefficient and the free speed reduction correction coefficient are corrected according to the magnitude relationship between the brake opening delay time and the first braking time.

[0010] Optionally, the method further includes: If the engine is decelerated to the target speed according to the second braking information, the free deceleration correction coefficient is corrected according to the ratio of the target deceleration to the target maximum deceleration.

[0011] Optionally, the second braking information includes a second braking time and a braking time correction coefficient, and the method further includes: If the engine decelerates to the target speed according to the second braking information, and the actual time is less than or equal to the expected deceleration time, the braking time correction coefficient is corrected according to the ratio of the actual time to the expected deceleration time; If the engine decelerates to the target speed according to the second braking information, and the actual time is greater than the expected deceleration time, the braking time correction coefficient is corrected according to the ratio of the third speed to the target speed.

[0012] In a second aspect, the present invention further provides an engine speed reduction device, comprising: An information acquisition module is used to obtain the current speed, target speed, free speed reduction characteristic information and expected speed reduction time of the engine; A first time prediction module, used for predicting a first time for the engine to freely decelerate from the current speed to the target speed according to the free deceleration characteristic information; A first speed reduction control module, configured to control the engine to freely reduce speed if the first time is less than or equal to the expected speed reduction time; The second deceleration control module is used to determine first braking information according to the difference between the first time and the expected deceleration time if the first time is greater than the expected deceleration time, and brake and decelerate the engine according to the first braking information.

[0013] In a third aspect, the present invention further provides a vehicle comprising a memory and a processor, wherein the memory is used to store a program; and the processor is coupled to the memory and is used to execute the program stored in the memory to implement the steps in any one of the above-mentioned engine speed reduction methods.

[0014] In a fourth aspect, the present invention further provides a computer-readable storage medium for storing a computer-readable program, wherein the program or instructions, when executed by a processor, can implement the steps in any one of the above-mentioned engine speed reduction methods.

[0015] The beneficial effects of the present invention are: When the AMT shifts up, the current engine speed, target speed, free deceleration characteristic information and expected deceleration time are first obtained; based on the free deceleration characteristic information, the first time for the engine to freely decelerate from the current speed to the target speed is predicted; then if the first time is less than or equal to the expected deceleration time, the engine is controlled to freely decelerate; if the first time is greater than the expected deceleration time, first braking information is determined based on the difference between the first time and the expected deceleration time, and the engine is braked and decelerated based on the first braking information, so that the engine deceleration time during the AMT shift up process can be accurately controlled, so that the engine completes the deceleration within the expected deceleration time, and the first braking information is determined based on the difference between the first time and the expected deceleration time, and the engine is braked and decelerated based on the first braking information, so that the engine can be prevented from decelerating too quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic flow chart of an embodiment of an engine speed reduction method provided by the present invention; Figure 2 A schematic diagram of the in-cylinder brake operation provided by the present invention; Figure 3 A schematic flow chart of another embodiment of the engine speed reduction method provided by the present invention; Figure 4 A schematic structural diagram of an embodiment of an engine speed reduction device provided by the present invention. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0018] In the description of the embodiments of the present invention, unless otherwise specified, "multiple" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0019] The terms "first", "second", etc., involved in the embodiments of the present invention are used to distinguish similar objects, but are not used to describe a specific order or sequence, nor are they used to indicate or imply their relative importance or implicitly indicate the number of technical features indicated. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more.

[0020] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] Reference Figure 1 , shows a flow chart of an embodiment of an engine speed reduction method provided by the present invention, the method comprising: S101, obtaining the current speed, target speed, free deceleration characteristic information and expected deceleration time of the engine.

[0022] S102, predicting the first time for the engine to freely decelerate from the current speed to the target speed based on the free deceleration characteristic information.

[0023] S103: If the first time is less than or equal to the expected deceleration time, the engine is controlled to decelerate freely.

[0024] S104: If the first time is greater than the expected deceleration time, first braking information is determined according to the difference between the first time and the expected deceleration time, and the engine is braked and decelerated according to the first braking information.

[0025] The free deceleration of the engine refers to the phenomenon that the vehicle gradually decelerates due to the internal resistance of the engine and the external resistance (such as air resistance, rolling resistance, etc.) when the engine does not actively apply braking (such as not stepping on the brake or using the handbrake). The free deceleration characteristic information of the engine can be information describing the relationship between the engine speed and time when the engine is free decelerating. The free deceleration characteristic information of the engine can be measured experimentally in advance.

[0026] During the AMT shifting process, the current speed and target speed of the engine can be obtained, and then the first time for the engine to freely decelerate from the current speed to the target speed can be predicted based on the free deceleration characteristic information, and the size relationship between the first time and the expected deceleration time can be compared. If the first time is less than or equal to the expected deceleration time, no additional braking is required, and the engine can be allowed to freely decelerate to the target speed; if the first time is greater than the expected deceleration time, additional braking is required to control the engine to decelerate to the target speed within the expected deceleration time. And when applying the brake, the first braking information can be determined based on the difference between the first time and the expected deceleration time. For example, the length of the braking time, the size of the braking force, or the choice of the braking method can be determined based on the difference, so as to control the engine to decelerate to the target speed within the expected deceleration time, and not decelerate too fast, resulting in energy waste.

[0027] In one embodiment, the braking method may be in-cylinder braking. The process of determining the first braking information may be: first obtain Map1, the X-axis of Map1 is the rotation speed, the Y-axis is the difference between the first time and the expected deceleration time, and the Z-axis is the in-cylinder brake opening time. Map1 can be calculated based on the free deceleration characteristic information, the braking power curve when the in-cylinder brake is turned on, Map2 and Map3; wherein, the X-axis of Map2 is the rotation speed, the Y-axis is the oil temperature, and the Z-axis is the brake opening delay time, and the X-axis of Map3 is the rotation speed, the Y-axis is the oil temperature, and the Z-axis is the brake closing delay time; after obtaining Map1, the first braking time can be obtained by querying Map1 based on the current rotation speed and the difference between the first time and the expected deceleration time. Δta ,according to Δta×λ Activate the in-cylinder brake signal; where λ is the brake time correction coefficient, the initial value is 1, and it will be corrected according to the engine deceleration result each time.

[0028] Different current speeds, target speeds and engine oil temperatures will result in different free deceleration characteristics of the engine. Therefore, in one embodiment, the current engine oil temperature can be obtained at the beginning of the AMT shift, and the target free deceleration characteristic information can be determined based on the current engine speed, target speed and current oil temperature; then, based on the target free deceleration characteristic information, the first time for the engine to freely decelerate from the current speed to the target speed is predicted.

[0029] In one embodiment, the free-deceleration characteristic information includes a first mapping relationship and a second mapping relationship; the first mapping relationship is a mapping relationship between the rotational speed and the time consumed by the rotational speed to reach the maximum deceleration during free deceleration; the second mapping relationship is a mapping relationship between the rotational speed and time during free deceleration. For example, the first mapping relationship can be represented by Map4, in which the X-axis is the rotational speed, the Y-axis is the oil temperature, and the Z-axis is the time required for free deceleration to reach the maximum deceleration; the second mapping relationship can be represented by Map5, in which the X-axis is time, the Y-axis is the oil temperature, and the Z-axis is the rotational speed. The first mapping relationship and the second mapping relationship can be obtained through experimental testing and other methods.

[0030] In this embodiment, S102 may specifically include: predicting the second time required for the engine to freely decelerate from the current speed to reach the maximum deceleration and the first speed at the maximum deceleration according to the first mapping relationship; predicting the third time required for the engine to decelerate from the first speed to the target speed according to the second mapping relationship; and calculating the first time according to the following formula: ; in, For the first time, For the second time, For the third time, is the free speed reduction correction factor.

[0031] During the free deceleration process of the engine, it takes a certain amount of time (second time) to reach the maximum deceleration due to factors such as the engine's response time. After reaching the maximum deceleration, it is a complete free deceleration process. In this embodiment, the second time and the third time can be calculated for the two deceleration stages, and then the second time and the third time are substituted into the above formula to obtain the first time. In the above formula, the initial value of the free deceleration correction coefficient is 1, and the free deceleration correction coefficient will be corrected according to the engine's deceleration result each time.

[0032] Since the second time is related to the oil temperature and the initial speed, the subsequent free deceleration process is also related to the oil temperature. Therefore, in one embodiment, the second time and the first speed can be determined according to the current oil temperature, the current speed and Map4; the third time can be determined according to the first speed and Map5, and finally the first time can be calculated according to the second time, the third time and the above formula.

[0033] In one embodiment, S103 may specifically include: when the engine is decelerated freely to a preset range of the first speed, obtaining a target maximum deceleration within the preset range, a second speed at the target maximum deceleration, and a fourth time required to reach the target maximum deceleration; predicting a fifth time required for the engine to decelerate from the second speed to the target speed and the target deceleration at the second speed according to the second mapping relationship; and calculating a sixth time according to the following formula: , ; in, For the sixth time, For the fourth time, For the fifth time, is the target deceleration, It can be calculated based on the slope at the second speed position in Map5, is the target maximum deceleration; After the engine reaches the second speed, if the sixth time is less than or equal to the expected deceleration time, the engine is controlled to decelerate freely to the target speed; if the sixth time is greater than the expected deceleration time, the second braking information is determined based on the difference between the sixth time and the expected deceleration time, and the engine is braked and decelerated based on the second braking information.

[0034] In this embodiment, when the free deceleration is near the first speed, the local maximum deceleration, that is, the target maximum deceleration, is sought near the first speed; when the target maximum deceleration is found, the sixth time is calculated, and based on the relationship between the sixth time and the expected deceleration time, it is re-determined whether to maintain free deceleration or perform braking deceleration. If it is determined that braking deceleration is required, Map1 can be queried based on the difference between the second speed, the sixth time and the expected deceleration time to obtain the second braking time. Δta' ,according to Δta' × l Activate the in-cylinder brake signal. In this embodiment, the deceleration method is modified during the free deceleration process, so that the deceleration process is more controllable.

[0035] In one embodiment, the engine deceleration method also includes: obtaining the actual time used for the engine to decelerate to the target speed, and the third speed of the engine when the expected deceleration time is reached; if the engine decelerates freely to the target speed, and the actual time is less than or equal to the expected deceleration time, then the free deceleration correction coefficient is corrected according to the ratio of the actual time to the expected deceleration time; if the engine decelerates freely to the target speed, and the actual time is greater than the expected deceleration time, then the free deceleration correction coefficient is corrected according to the ratio of the third speed to the target speed.

[0036] In this embodiment, if the engine is free to slow down to the target speed, the actual time can be determined. t'' Is it less than or equal to the expected deceleration time? tt ,like , then determine ,like , then determine ,in, The third speed, is the target speed.

[0037] The prior art usually determines whether to turn on the in-cylinder brake based on the difference between the current engine speed and the target speed, and then controls the exit of the in-cylinder brake through the speed difference to achieve rapid engine deceleration. This method requires calibration of the relationship between the engine speed difference and the entry and exit of the in-cylinder brake, and requires separate calibration for different current gears and target gears, and recalibration when the AMT actuator changes, which requires a certain amount of work. However, with the method of this embodiment, there is no need to calibrate separately for different current gears and target gears, nor is there any need to recalibrate when the AMT actuator changes, which can save workload.

[0038] In addition, there are differences in properties between different engines. For example, there will be differences in in-cylinder braking power, and these differences will lead to differences in engine deceleration, thus affecting the actual control effect. In addition, the engine load, such as fans, air pumps, air conditioning compressors, and changes in the engine's water temperature, will also affect the engine's free deceleration rate, thereby making the adaptability of the actual deceleration control worse. The present embodiment corrects the free deceleration correction coefficient according to the free deceleration result, which can improve the accuracy of the free deceleration correction coefficient. Controlling the free deceleration process of the engine based on the free deceleration correction coefficient can make up for the differences from the calibration process caused by changes in environmental conditions and engine consistency, so that the actual control process is close to the expected control process, thereby improving the universality of the present invention to different vehicles and different engines.

[0039] In one embodiment, the first braking information includes a first braking time and a braking time correction coefficient, and the engine deceleration method further includes: if the engine decelerates to a target speed according to the first braking information, obtaining a braking start delay time; and correcting the braking time correction coefficient and the free deceleration correction coefficient according to a relationship between the braking start delay time and the first braking time.

[0040] In this embodiment, if the engine is decelerated to the target speed according to the first braking information, the actual time can be determined. t'' Is it less than or equal to the expected deceleration time? tt ,like , then let ,like , then let Then continue to determine whether the product of the first braking time and the braking time correction coefficient λ is greater than the brake opening delay time ,like , then let , ,like , then let , ;in, is the maximum deceleration during the entire deceleration process, Based on Speed ​​at and the interpolation calculation of the in-cylinder brake deceleration curve Theoretical deceleration at.

[0041] This embodiment corrects the free deceleration correction coefficient and the braking time correction coefficient according to the braking result of the engine according to the first braking information, which can improve the accuracy of the free deceleration correction coefficient and the braking time correction coefficient. The free deceleration process of the engine is controlled based on the free deceleration correction coefficient and the braking time correction coefficient, which can make the actual control process close to the expected control process, thereby improving the universality for different vehicles and different engines.

[0042] In one embodiment, the engine deceleration method further includes: if the engine is decelerated to the target speed according to the second braking information, then the free deceleration correction coefficient is corrected according to the ratio of the target deceleration to the target maximum deceleration.

[0043] If the engine speed drops to the target speed according to the second braking information, then .

[0044] In one embodiment, the second braking information includes a second braking time and a braking time correction coefficient, and the engine deceleration method further includes: if the engine decelerates to the target speed according to the second braking information, and the actual time is less than or equal to the expected deceleration time, then the braking time correction coefficient is corrected according to the ratio of the actual time to the expected deceleration time; if the engine decelerates to the target speed according to the second braking information, and the actual time is greater than the expected deceleration time, then the braking time correction coefficient is corrected according to the ratio of the third speed to the target speed.

[0045] If the engine slows down to the target speed according to the second braking information, the actual time is determined. t'' Is it less than or equal to the expected deceleration time? tt ,like , then let ,like , then let .

[0046] Reference Figure 2 , showing a schematic diagram of the in-cylinder brake operation provided by the present invention. t0 Start to slow down at this moment, and slow down to t1 Reaching maximum deceleration, t1 After that, it is a completely free deceleration process, decelerating to t4 Reach the target speed. for t0 To t1 The time between It is the time required for the cylinder brake to be activated and the braking power to reach the maximum, that is, the brake opening delay time; It is the time required to restore from the current deceleration rate to the natural deceleration rate when the cylinder brake is closed, that is, the brake closing delay time; for t1 To t4 The time between.

[0047] Reference Figure 3 , showing a flow chart of another embodiment of the engine speed reduction method provided by the present invention.

[0048] 1. Speed ​​reduction start phase: The timer starts timing based on the speed reduction start time t0 Oil temperature T and the current engine speed S0 , check Map4 to get the second time when the deceleration reaches the maximum value Δt1 And the first speed at this time S1 , based on the first speed S1 , Target speed St and oil temperature T Check Map5 to estimate the third time required to slow down Δt4 ,if The expected deceleration time has been exceeded tt , then through t-tt and S0 Check the cylinder brake deceleration Map1 to obtain the first braking time Δta ,according to Δta × l Activate the in-cylinder brake signal, otherwise keep free deceleration at the beginning of deceleration.

[0049] 2. Start the in-cylinder brake at the beginning of deceleration, and wait until the engine speed reaches St , record the time taken at this time t'' , wait for the recording time to reach tt , record the speed at this time Stt .like , then let ,like , then let . Measure and calculate the cylinder brake delay time Δt2, if , then let , ,like , then let , .

[0050] 3. Keep the speed down freely at the beginning of the speed down to the first speed. S1 Nearby, find the local maximum deceleration , record this moment t1' and the second engine speed S1' , found through the free deceleration curve Map5 S1' Deceleration at speed a1 , calculated Based on oil temperature T , Second speed S1' and target speed St , check Map5 to estimate Δt4' , .

[0051] if t'>tt , then based on S1' and t'-tt Look up table Map1 to get the duration of the in-cylinder brake that needs to be turned on D of , control the brake in the cylinder to open Δta' × l . Wait until the engine speed reaches St , record the time taken at this time t'' , wait for the recording time to reach tt , record the speed at this time Stt .like , then let ,like , then let ; .

[0052] if , then maintain free deceleration until the engine speed reaches St , record the time taken at this time t'' , wait for the recording time to reach tt , record the speed at this time Stt .like , then determine ,like , then determine , l Remain unchanged.

[0053] Reference Figure 4 , shows a schematic structural diagram of an embodiment of an engine speed reduction device provided by the present invention, the device 40 comprises: The information acquisition module 401 is used to acquire the current speed, target speed, free speed reduction characteristic information and expected speed reduction time of the engine; A first time prediction module 402, configured to predict a first time for the engine to freely decelerate from the current speed to the target speed according to the free deceleration characteristic information; A first deceleration control module 403, configured to control the engine to decelerate freely if the first time is less than or equal to the expected deceleration time; The second deceleration control module 404 is configured to determine first braking information according to a difference between the first time and the expected deceleration time if the first time is greater than the expected deceleration time, and brake and decelerate the engine according to the first braking information.

[0054] It should be noted that the implementation principles or implementation processes of the above modules can refer to the embodiments of the above-mentioned engine speed reduction method, and will not be described one by one here.

[0055] In one embodiment, the present invention further provides a vehicle, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the steps of any one of the above-mentioned engine speed reduction methods are implemented.

[0056] In one embodiment, the present invention further provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by the processor, the steps of any one of the above-mentioned engine speed reduction methods are implemented.

[0057] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0058] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An engine speed reduction method, characterized in that: include: Obtain the current engine speed, target speed, free speed reduction characteristic information and expected speed reduction time; predicting, based on the free-speed-falling characteristic information, a first time for the engine to freely fall from the current speed to the target speed; If the first time is less than or equal to the expected deceleration time, controlling the engine to decelerate freely; If the first time is greater than the expected deceleration time, first braking information is determined according to a difference between the first time and the expected deceleration time, and the engine is braked and decelerated according to the first braking information.

2. The engine speed reduction method according to claim 1, characterized in that: The free-speed deceleration characteristic information includes a first mapping relationship and a second mapping relationship; the first mapping relationship is a mapping relationship between the speed and the time taken for the speed to freely decelerate to reach the maximum deceleration; the second mapping relationship is a mapping relationship between the speed and time during free deceleration; Then, predicting the first time for the engine to freely decelerate from the current speed to the target speed according to the free deceleration characteristic information includes: Predicting, according to the first mapping relationship, a second time required for the engine to freely decelerate from the current speed to reach a maximum deceleration, and a first speed at the maximum deceleration; predicting, according to the second mapping relationship, a third time required for the engine to decelerate from the first speed to the target speed; The first time is calculated according to the following formula: ； in, For the first time, For the second time, For the third time, is the free speed reduction correction factor.

3. The engine speed reduction method according to claim 2, characterized in that: Controlling the engine to free-speed down, comprising: When the engine is decelerated freely to a preset range of the first speed, obtaining a target maximum deceleration within the preset range, a second speed at the target maximum deceleration, and a fourth time required to reach the target maximum deceleration; predicting, according to the second mapping relationship, a fifth time required for the engine to decelerate from the second speed to the target speed, and a target deceleration at the second speed; The sixth time is calculated according to the following formula: ， ； in, For the sixth time, For the fourth time, For the fifth time, is the target deceleration, is the target maximum deceleration; After the engine reaches the second speed, if the sixth time is less than or equal to the expected deceleration time, controlling the engine to freely decelerate to the target speed; If the sixth time is greater than the expected deceleration time, second braking information is determined according to the difference between the sixth time and the expected deceleration time, and the engine is braked and decelerated according to the second braking information.

4. The engine speed reduction method according to claim 3, characterized in that: The method further comprises: Acquire the actual time taken for the engine to decelerate to the target speed, and the third speed of the engine when the expected deceleration time is reached; If the engine decelerates freely to the target speed and the actual time is less than or equal to the expected deceleration time, the free deceleration correction coefficient is corrected according to the ratio of the actual time to the expected deceleration time; If the engine decelerates freely to the target speed and the actual time is greater than the expected deceleration time, the free deceleration correction coefficient is corrected according to a ratio of the third speed to the target speed.

5. The engine speed reduction method according to claim 3, characterized in that: The first braking information includes a first braking time and a braking time correction coefficient, and the method further includes: If the engine is decelerated to the target speed according to the first braking information, a brake opening delay time is obtained; The braking time correction coefficient and the free speed reduction correction coefficient are corrected according to the magnitude relationship between the brake opening delay time and the first braking time.

6. The engine speed reduction method according to claim 3, characterized in that: The method further comprises: If the engine is decelerated to the target speed according to the second braking information, the free deceleration correction coefficient is corrected according to the ratio of the target deceleration to the target maximum deceleration.

7. The engine speed reduction method according to claim 4, characterized in that: The second braking information includes a second braking time and a braking time correction coefficient, and the method further includes: If the engine decelerates to the target speed according to the second braking information, and the actual time is less than or equal to the expected deceleration time, the braking time correction coefficient is corrected according to the ratio of the actual time to the expected deceleration time; If the engine decelerates to the target speed according to the second braking information, and the actual time is greater than the expected deceleration time, the braking time correction coefficient is corrected according to the ratio of the third speed to the target speed.

8. An engine speed reduction device, characterized in that: include: An information acquisition module is used to obtain the current speed, target speed, free speed reduction characteristic information and expected speed reduction time of the engine; A first time prediction module, used for predicting a first time for the engine to freely decelerate from the current speed to the target speed according to the free deceleration characteristic information; A first speed reduction control module, configured to control the engine to freely reduce speed if the first time is less than or equal to the expected speed reduction time; The second deceleration control module is used to determine first braking information according to the difference between the first time and the expected deceleration time if the first time is greater than the expected deceleration time, and brake and decelerate the engine according to the first braking information.

9. A vehicle, characterized in that: comprising a memory and a processor, wherein: The memory is used to store programs; The processor is coupled to the memory and is used to execute the program stored in the memory to implement the steps in the engine speed reduction method described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: Used to store a computer-readable program, wherein when the program or instruction is executed by a processor, the steps in the engine speed reduction method described in any one of claims 1 to 7 can be implemented.

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