Shift control method and device for at transmission with auxiliary brake on

Abstract

This application relates to a shift control method and device for an automatic transmission (AT) when auxiliary braking is activated. Based on the current output shaft speed signal of the transmission and the engine's rated power point speed, the lowest gear that the transmission can be downshifted to under the current operating conditions is calculated. This lowest gear is then used as the target gear for downshift control. After downshifting, the engine speed is increased to near the rated speed, placing the engine in a high-speed range and enhancing the engine's braking effect. The AT transmission employs a new shift strategy to raise the downshift point when auxiliary braking is activated, which can quickly increase engine speed and maintain the engine in a high-speed range. Simultaneously, it accelerates the retarder's oil filling, rapidly establishing braking torque and improving the braking effect of auxiliary braking, effectively protecting the safety of the vehicle and its occupants.

Description

Technical Field

[0001] This application relates to the field of transmission control, and more specifically, to a shift control method and device for an automatic transmission when the auxiliary braking is activated. Background Technology

[0002] When cargo or passenger vehicles are on long downhill sections, the braking system is prone to heat fade due to prolonged operation, posing a safety hazard. Therefore, vehicles are often equipped with auxiliary braking systems, such as engine exhaust brakes and hydraulic retarders. These auxiliary braking systems can alleviate braking pressure on the main braking system to some extent. However, these auxiliary braking systems have the following drawbacks: 1. Engine exhaust brakes are directly related to engine speed, resulting in weak braking torque and poor braking effect at low engine speeds; 2. Hydraulic retarders rely on hydraulic transmission, so the establishment of braking torque is relatively delayed, resulting in weak initial braking effect. Summary of the Invention

[0003] In order to overcome at least one deficiency in the prior art, this application provides a shift control method and device when the auxiliary braking of an AT transmission is activated.

[0004] Firstly, a shift control method is provided for an automatic transmission (AT) when auxiliary braking is activated, including:

[0005] Calculate the lowest permissible gear (GearY) of the transmission based on the transmission output shaft speed and the engine rated power point speed;

[0006] When the auxiliary braking is activated, determine whether the current gear of the transmission is higher than the lowest permissible gear, GearY.

[0007] If the current gear of the transmission is higher than the lowest permissible gear GearY, downshift the current gear of the transmission to the lowest permissible gear GearY.

[0008] When the engine exhaust braking torque is greater than the first limit and continues for a set time, or when the retarder braking torque is greater than the second limit and continues for a set time, the transmission shift point is adjusted to obtain a new shift point.

[0009] Determine if the current gear is higher than the target gear for GearX;

[0010] If the current gear is higher than the target gear GearX, downshift to the target gear GearX according to the new shift point.

[0011] In one embodiment, the lowest permissible gear (GearY) of the transmission is calculated based on the transmission output shaft speed and the engine rated speed, including:

[0012] Step S11: Set the lowest gear allowed by the transmission, GearY, to the default highest gear of the transmission.

[0013] Step S12, calculate the maximum allowable transmission output shaft speed R, R = engine rated power point speed / GearY-1 gear ratio;

[0014] Step S13: Determine whether the current transmission output shaft speed is less than the maximum allowable transmission output shaft speed R; if yes, proceed to step S14; if no, proceed to step S15.

[0015] Step S14: Update the lowest allowed gear of the transmission, GearY, to GearY-1, denoted as GearY. ′ Calculate the maximum permissible transmission output shaft speed R at this time, R = engine rated power point speed / GearY ′ -1 gear ratio; return to step S13;

[0016] Step S15: Determine whether the lowest gear allowed by the transmission, GearY, is less than the target gear, GearX. If yes, the lowest gear allowed by the transmission, GearY, is equal to the target gear, GearX. If no, output the lowest gear allowed by the transmission, GearY.

[0017] In one embodiment, adjusting the transmission shift point includes increasing the output shaft speed at the downshift point.

[0018] In one embodiment, the first limit is 0 N / m, the second limit is 0 N / m, and the set duration is 2 seconds.

[0019] Secondly, a shift control device is provided for an automatic transmission (AT) when auxiliary braking is activated, comprising:

[0020] The lowest gear calculation module is used to calculate the lowest permissible gear (GearY) of the transmission based on the transmission output shaft speed and the engine rated power point speed.

[0021] The first judgment module is used to determine whether the current gear of the transmission is greater than the lowest permissible gear, GearY, when the auxiliary braking is activated.

[0022] The first downshift module is used to downshift the current gear of the transmission to the lowest permissible gear, GearY, if the current gear of the transmission is higher than the lowest permissible gear, GearY.

[0023] The shift point adjustment module is used to adjust the transmission shift point to obtain a new shift point when the engine exhaust braking torque is greater than the first limit and continues for a set time, or when the retarder braking torque is greater than the second limit and continues for a set time.

[0024] The second judgment module is used to determine whether the current gear is greater than the target gear of GearX;

[0025] The second downshift module is used to downshift the current gear to the target gear (GearX) according to the new shift point if the current gear is higher than the target gear (GearX).

[0026] In one embodiment, the lowest gear calculation module is also used to perform the following functions:

[0027] Step S11: Set the lowest gear allowed by the transmission, GearY, to the default highest gear of the transmission.

[0028] Step S12, calculate the maximum allowable transmission output shaft speed R, R = engine rated power point speed / GearY-1 gear ratio;

[0029] Step S13: Determine whether the current transmission output shaft speed is less than the maximum allowable transmission output shaft speed R; if yes, proceed to step S14; if no, proceed to step S15.

[0030] Step S14: Update the lowest allowed gear of the transmission, GearY, to GearY-1, denoted as GearY. ′ Calculate the maximum permissible transmission output shaft speed R at this time, R = engine rated power point speed / GearY ′ -1 gear ratio; return to step S13;

[0031] Step S15: Determine whether the lowest gear allowed by the transmission, GearY, is less than the target gear, GearX. If yes, the lowest gear allowed by the transmission, GearY, is equal to the target gear, GearX. If no, output the lowest gear allowed by the transmission, GearY.

[0032] In one embodiment, the shift point adjustment module is also used to: increase the output shaft speed at the downshift point.

[0033] In one embodiment, the first limit is 0 N / m, the second limit is 0 N / m, and the set duration is 2 seconds.

[0034] Thirdly, a computer-readable storage medium is provided, which stores a computer program that, when executed by a processor, implements the shift control method described above for when the auxiliary braking of an AT transmission is activated.

[0035] Fourthly, a computer program product is provided, including a computer program / instruction, which, when executed by a processor, implements the aforementioned shift control method for AT transmission auxiliary braking activation.

[0036] Compared with the prior art, this application has the following beneficial effects: This application provides a shift control method and device when the auxiliary braking of an AT transmission is activated, which can quickly increase the engine speed and keep the engine in the high speed range, improve the braking effect of the auxiliary braking, and effectively protect the safety of the vehicle and personnel. Attached Figure Description

[0037] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings, which, together with the detailed description below, are incorporated in and form part of this specification. In the drawings:

[0038] Figure 1 A flowchart of a shift control method for an AT transmission when auxiliary braking is activated, according to an embodiment of this application, is shown.

[0039] Figure 2 A schematic diagram showing the adjustment of the transmission shift points is shown;

[0040] Figure 3 A flowchart illustrating the calculation of the lowest permissible gear (GearY) of the transmission according to an embodiment of this application is shown. Detailed Implementation

[0041] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of the actual embodiments are described in the specification. However, it should be understood that many embodiment-specific decisions can be made in the development of any such actual embodiment to achieve the developer’s specific objectives, and these decisions may vary as the embodiments differ.

[0042] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the device structure closely related to the solution according to this application is shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0043] It should be understood that this application is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, embodiments may be combined with each other, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in one embodiment, where feasible.

[0044] This application provides a shift control method for an automatic transmission when auxiliary braking is activated. Figure 1 A flowchart illustrating a shift control method for an automatic transmission with auxiliary braking activated according to an embodiment of this application is shown. See also... Figure 1 The methods include:

[0045] Step S1: Calculate the lowest permissible gear GearY based on the transmission output shaft speed and the engine rated power point speed.

[0046] Here, it is first determined whether the vehicle is equipped with auxiliary braking function and whether the target gear GearX configuration is valid when the auxiliary braking function is activated. If the vehicle is equipped with auxiliary braking function and the target gear GearX configuration is valid when the auxiliary braking function is activated, step S1 is performed to calculate the lowest allowed gear GearY of the transmission. Otherwise, the existing shifting strategy is followed. Here, the target gear GearX is a transmission configuration parameter, generally set to direct drive. For example, in a 6-speed transmission, the direct drive is usually 4th gear.

[0047] Step S2: When the auxiliary braking is activated, determine whether the current gear of the transmission is higher than the lowest permissible gear, GearY.

[0048] Step S3: If the current gear of the transmission is higher than the lowest permissible gear (GearY), downshift the current gear to the lowest permissible gear (GearY). If the current gear is not higher than the lowest permissible gear (GearY), shift gears according to the existing shifting strategy.

[0049] Step S4: When the engine exhaust braking torque exceeds the first limit for a set duration, or the retarder braking torque exceeds the second limit for a set duration, adjust the transmission shift point to obtain a new shift point. If this condition is not met, shift according to the existing shift strategy.

[0050] Specifically, the first limit can be 0 N / m, the second limit can be 0 N / m, and the set duration can be 2 seconds. In other embodiments, the first limit, the second limit, and the set duration can also be other values.

[0051] Here, adjusting the transmission shift point specifically means increasing the output shaft speed at the downshift point. Figure 2 A schematic diagram showing the adjustment of the transmission shift points is shown. See [link / reference] Figure 2 Taking downshifting from 6th to 5th gear and from 5th to 4th gear as examples, once the conditions are met, the transmission shift point is adjusted, that is, the output shaft speed at the downshift point is increased. Figure 2 The black curve represents the default downshift point curve for downshifting from 6th to 5th gear and from 5th to 4th gear. After adjustment, the downshift point curve is the green part, which means increasing the output shaft speed at the downshift point, so that the output shaft speed increases by 200 rpm on the basis of the original downshift point speed.

[0052] Step S5: Determine whether the current gear is greater than the target gear GearX.

[0053] Step S6: If the current gear is higher than the target GearX gear, downshift to the target GearX gear according to the new shift point. See here. Figure 2 Taking a 5th gear downshift to 4th gear as an example, the default shift point for 5->4 with zero throttle is 1000 RPM. After adjustment, the downshift point RPM for 5->4 with zero throttle is increased to 1200 RPM. When the auxiliary brake is engaged, the downshift from 5th to 4th gear occurs when the output shaft speed is below 1200 RPM. This increases the downshift point RPM, controlling the transmission to downshift earlier and quickly reach the target GearX gear. If the current gear is not higher than the target GearX gear, the existing shifting strategy will apply.

[0054] In this embodiment, the AT transmission collects auxiliary braking switch signals (hard-wired signal input and CAN message input) during vehicle operation. When the auxiliary braking activation conditions are met and the auxiliary braking is working, the lowest gear that the transmission can be downshifted to under the current operating conditions is calculated based on the current output shaft speed signal of the transmission and the rated power point speed of the engine. This lowest gear is then used as the target gear for downshift control. After the AT transmission downshifts, the engine speed is increased to near the rated speed, the engine is in the high speed range, and the engine braking effect is enhanced.

[0055] When the automatic transmission (AT) engages auxiliary braking, it employs a new shifting strategy to raise the downshift point. Raising the downshift point allows the transmission to quickly downshift to the configured gear and keeps the engine in a high-speed range. This shifting strategy rapidly increases engine speed and maintains it in the high-speed range, enhancing engine-assisted braking. Simultaneously, it accelerates the retarder's oil filling to quickly build up braking torque, improving the braking effect of auxiliary braking and effectively protecting the safety of the vehicle and its occupants.

[0056] In one embodiment, in step S1, the lowest permissible gear GearY is calculated based on the transmission output shaft speed and the engine rated speed. Figure 3 A flowchart illustrating the calculation of the lowest permissible gear (GearY) according to an embodiment of this application is shown. See also... Figure 3 It can include:

[0057] Step S11: Set the lowest gear allowed by the transmission, GearY, to the default highest gear of the transmission; for example, GearY = 6.

[0058] Step S12, calculate the maximum allowable transmission output shaft speed R, R = engine rated power point speed / GearY-1 gear ratio;

[0059] Step S13: Determine whether the current transmission output shaft speed is less than the maximum allowable transmission output shaft speed R; if yes, proceed to step S14; if no, proceed to step S15.

[0060] Step S14: Update the lowest allowed gear of the transmission, GearY, to GearY-1, denoted as GearY. ′ Calculate the maximum permissible transmission output shaft speed R at this time, R = engine rated power point speed / GearY ′ -1 gear ratio; return to step S13;

[0061] Step S15: Determine whether the lowest gear allowed by the transmission, GearY, is less than the target gear, GearX. If yes, the lowest gear allowed by the transmission, GearY, is equal to the target gear, GearX. If no, output the lowest gear allowed by the transmission, GearY.

[0062] Based on the same inventive concept as the shift control method when the auxiliary braking of an AT transmission is activated, this embodiment also provides a corresponding shift control device for when the auxiliary braking of an AT transmission is activated, including:

[0063] The lowest gear calculation module is used to calculate the lowest permissible gear (GearY) of the transmission based on the transmission output shaft speed and the engine's rated power point speed.

[0064] The first judgment module is used to determine whether the current gear of the transmission is higher than the lowest permissible gear, GearY, when the auxiliary braking is activated.

[0065] The first downshift module is used to downshift the current gear of the transmission to the lowest permissible gear, GearY, if the current gear of the transmission is higher than the lowest permissible gear, GearY.

[0066] The shift point adjustment module is used to adjust the transmission shift point to obtain a new shift point when the engine exhaust braking torque is greater than a first limit and continues for a set time, or when the retarder braking torque is greater than a second limit and continues for a set time.

[0067] The second judgment module is used to determine whether the current gear is greater than the target gear in GearX.

[0068] The second downshift module is used to downshift the current gear to the target gear (GearX) according to the new shift point if the current gear is higher than the target gear (GearX).

[0069] In one embodiment, the lowest gear calculation module is also used to perform the following functions:

[0070] Step S11: Set the lowest gear allowed by the transmission, GearY, to the default highest gear of the transmission.

[0071] Step S12, calculate the maximum allowable transmission output shaft speed R, R = engine rated power point speed / GearY-1 gear ratio;

[0072] Step S13: Determine whether the current transmission output shaft speed is less than the maximum allowable transmission output shaft speed R; if yes, proceed to step S14; if no, proceed to step S15.

[0073] Step S14: Update the lowest allowed gear of the transmission, GearY, to GearY-1, denoted as GearY. ′ Calculate the maximum permissible transmission output shaft speed R at this time, R = engine rated power point speed / GearY ′ -1 gear ratio; return to step S13;

[0074] Step S15: Determine whether the lowest gear allowed by the transmission, GearY, is less than the target gear, GearX. If yes, the lowest gear allowed by the transmission, GearY, is equal to the target gear, GearX. If no, output the lowest gear allowed by the transmission, GearY.

[0075] The shift control device for AT transmission auxiliary braking in the above embodiment has the same inventive concept as the shift control method for AT transmission auxiliary braking in the above description. Therefore, the specific implementation of the device can be found in the embodiment section of the shift control method for AT transmission auxiliary braking in the above description, and its technical effects correspond to the technical effects of the above method. It will not be repeated here.

[0076] This application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned shift control method for AT transmission auxiliary braking activation.

[0077] This application provides a computer program product, including a computer program / instruction. When the computer program / instruction is executed by a processor, it implements the above-described shift control method when the auxiliary braking of an AT transmission is activated.

[0078] The above descriptions are merely various embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A shift control method for an automatic transmission when auxiliary braking is activated, characterized in that, include: Calculate the lowest permissible gear (GearY) of the transmission based on the transmission output shaft speed and the engine rated power point speed; When the auxiliary braking is activated, determine whether the current gear of the transmission is higher than the minimum allowable gear GearY; If the current gear of the transmission is greater than the lowest permissible gear GearY, then the current gear of the transmission is downgraded to the lowest permissible gear GearY. When the engine exhaust braking torque is greater than the first limit and continues for a set time, or when the retarder braking torque is greater than the second limit and continues for a set time, the transmission shift point is adjusted to obtain a new shift point. Determine if the current gear is higher than the target gear for GearX; If the current gear is greater than the target gear GearX, downshift to the target gear GearX according to the new shift point; The calculation of the lowest permissible gear (GearY) for the transmission, based on the transmission output shaft speed and the engine rated speed, includes: Step S11: Set the lowest gear allowed by the transmission, GearY, to the default highest gear of the transmission. Step S12, calculate the maximum allowable transmission output shaft speed R, R = engine rated power point speed / GearY-1 gear ratio; Step S13: Determine whether the current transmission output shaft speed is less than the maximum allowable transmission output shaft speed R; if yes, proceed to step S14; if no, proceed to step S15. Step S14: Update the lowest allowed gear of the transmission, GearY, to GearY-1, denoted as... ; Calculate the maximum permissible transmission output shaft speed at this time. , =Engine rated power point speed / -1 gear ratio; return to step S13; Step S15: Determine whether the lowest gear allowed by the transmission, GearY, is less than the target gear, GearX. If yes, the lowest gear allowed by the transmission, GearY, is equal to the target gear, GearX. If no, output the lowest gear allowed by the transmission, GearY.

2. The method as described in claim 1, characterized in that, The adjustment of the transmission shift point includes raising the output shaft speed at the downshift point.

3. The method as described in claim 1, characterized in that, The first limit is 0 N / m, the second limit is 0 N / m, and the set duration is 2 seconds.

4. A shift control device for an automatic transmission when the auxiliary brake is engaged, characterized in that, include: The lowest gear calculation module is used to calculate the lowest permissible gear (GearY) of the transmission based on the transmission output shaft speed and the engine rated power point speed. The first judgment module is used to determine whether the current gear of the transmission is greater than the minimum allowable gear GearY when the auxiliary braking is activated. The first downshift module is used to downshift the current gear of the transmission to the lowest permissible gear, GearY, if the current gear of the transmission is higher than the lowest permissible gear, GearY. The shift point adjustment module is used to adjust the transmission shift point to obtain a new shift point when the engine exhaust braking torque is greater than the first limit and continues for a set time, or when the retarder braking torque is greater than the second limit and continues for a set time. The second judgment module is used to determine whether the current gear is greater than the target gear of GearX; The second downshift module is used to downshift the current gear to the target gear GearX according to the new shift point if the current gear is greater than the target gear GearX. The lowest gear calculation module is also used to implement the following functions: Step S11: Set the lowest gear allowed by the transmission, GearY, to the default highest gear of the transmission. Step S12, calculate the maximum allowable transmission output shaft speed R, R = engine rated power point speed / GearY-1 gear ratio; Step S13: Determine whether the current transmission output shaft speed is less than the maximum allowable transmission output shaft speed R; if yes, proceed to step S14; if no, proceed to step S15. Step S14: Update the lowest allowed gear of the transmission, GearY, to GearY-1, denoted as... ; Calculate the maximum permissible transmission output shaft speed at this time. , =Engine rated power point speed / -1 gear ratio; Return to step S13; Step S15: Determine whether the lowest gear allowed by the transmission, GearY, is less than the target gear, GearX. If yes, the lowest gear allowed by the transmission, GearY, is equal to the target gear, GearX. If no, output the lowest gear allowed by the transmission, GearY.

5. The apparatus as described in claim 4, characterized in that, The shift point adjustment module is also used to: increase the output shaft speed at the downshift point.

6. The apparatus as claimed in claim 4, characterized in that, The first limit is 0 N / m, the second limit is 0 N / m, and the set duration is 2 seconds.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the shift control method for AT transmission auxiliary braking activation as described in any one of claims 1-3.

8. A computer program product, characterized in that, Includes a computer program / instruction, which, when executed by a processor, implements the shift control method for AT transmission auxiliary braking activation as described in any one of claims 1-3.

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