CHOI, Yoonjoon (108-505 Gwanak Hyundai Apt, Sangdo 5-dongDongjak-gu, Seoul 156-781, KR)
PARK, Jungcheol (509 Shinsanbon Livingcetel, 872-2 Dang-dongGunpo-si, Gyeonggi-do 435-010, KR)
CHO, Songpyo (8 Seorak Apt, Sanbon-dongGunpo-si, Gyeonggi-do 435-040, 75-1904, KR)
KIM, Byungjun (1405-403 Maehwa Apt, Sanbon 1-dongGunpo-si, Gyeonggi-do 435-738, KR)
CHOI, Yoonjoon (108-505 Gwanak Hyundai Apt, Sangdo 5-dongDongjak-gu, Seoul 156-781, KR)
PARK, Jungcheol (509 Shinsanbon Livingcetel, 872-2 Dang-dongGunpo-si, Gyeonggi-do 435-010, KR)
CHO, Songpyo (8 Seorak Apt, Sanbon-dongGunpo-si, Gyeonggi-do 435-040, 75-1904, KR)
Claims
[1] A shift control method in incorrectness of a gear ratio for a vehicle, comprising: detecting whether shift is completed with an engine on; monitoring continuously incorrectness of a gear ratio after the shift control is completed; shifting a shift range to a substitute shift range that is lower than the present shift range when the incorrectness of a gear ratio is detected; and shifting the shift range to another substitute shift range that is lower than the substitute shift range when the incorrectness of a gear ratio is re-detected after the completing the shift control to the substitute shift range.
[2] The method according to claim 1, further comprising: determining whether input/output shaft speed sensors have problems, between the determining of the completion of shift and the determining of the incorrectness of a gear ratio.
[3] The method according to claim 1, wherein in detecting the incorrectness of a gear ratio, by comparing the difference of the number of rotations of the turbine that has been estimated and the number of rotations of the turbine that has been measured with a set value, when the difference is smaller than the set value, a normal state is determined, and when the difference is larger than the set value, it is determined that incorrectness of a gear ratio corresponding to an error is generated.
[4] The method according to claim 3, wherein the set value is determined by an experimental value obtained in consideration of a tolerance in which the set value is not a base for determining generation of the incorrectness of a gear ratio.
[5] The method according to claim 1, wherein when the incorrectness of a gear ratio is not generated in the detecting of the incorrectness of a gear ratio, or when an error of the incorrectness of a gear ratio is not generated any more, after the incorrectness of gear ratio is generated and the shift control to the substitute shift range is performed, and the substitute shift range is a higher shift range than the first stage, the normal shift control is performed at the other shift ranges than the shift range where the incorrectness of a gear ratio is generated while the vehicle travels.
[6] The method according to claim 1 , wherein the substitute shift range is set to a shift range that is one- stage lower than the present shift range.
[7] The method according to claim 1, wherein the shifting of the shift range to the lower substitute range is repeated until the substitute shift range becomes the first stage, as long as the incorrectness of a gear ratio is detected. [8] The method according to claim 7, wherein when the substitute shift range becomes the first stage, hydraulic control is finished to unnecessary hydraulic control for the shift control is not performed any more. |
Description
SHIFT CONTROL METHOD IN INCORRECTNESS OF GEAR RATIO FOR AUTOMATIC TRANSMISSION
Technical Field
[1] The present invention relates to a shift control method of an automatic transmission, particularly a shift control method in incorrectness of gear ratio for an automatic transmission that can secure minimum traveling of a vehicle by varying a substitute shift range that is set in shift control that is made for a limp home generated in incorrectness of a gear ratio while the vehicle travels. Background Art
[2] In general, in transmissions equipped in a vehicle, an automatic transmission automatically converts and outputs a driving force supplied from the engine in consideration of the driver's intention and the present traveling speed in an appropriate gear ratio.
[3] That is, the shift control of the automatic transmission is performed according to opening of a throttle valve by pushing an acceleration pedal and a shift pattern optimally set in consideration of the present vehicle speed.
[4] On the other hand, when incorrectness of a gear ratio is generated while a vehicle equipped with the automatic transmission travels, a transmission control unit controls a limp home by stopping power for a solenoid and shift the present shift range to a predetermined shift range.
[5] In this operation, there are a variety of reasons for the incorrectness of a gear ratio, but slip due to wear generated in friction elements, such as a clutch, and adherence of valves provided in a hydraulic system for controlling the operation of the friction elements are known as main factors.
[6] Further, the substitute shift range that is shifted in the incorrectness of a gear ratio is set to a direct drive shift range where the input and output of the transmission is generally converted in the same level, which results from shift control to the direct drive shift range while the transmission control unit determines the incorrectness of a gear ratio.
[7] However, when the incorrectness of a gear ratio is generated again or the slip in the friction elements that operate at the direct drive shift range or the adherence of valves providing hydraulic pressure to the friction elements are generated, even after the shift to the direct drive range is performed in the incorrectness of a gear ratio, a vehicle cannot travel.
[8] That is, in controlling a limp home in an automatic transmission in the related art,
since the substitute shift range is fixed to one type of shift range, such as the direct driver shift range, a normal function for the limp home cannot be achieved. Disclosure of Invention Technical Problem
[9] In order to overcome the problems, it is an object of the invention to achieve a normal function of a limp home by varying substitute shift ranges that is set to avoid incorrectness of a gear ratio for shift control for the limp home when the incorrectness of a gear ratio is generated while a vehicle travels such that minimum traveling is secured for the vehicle. Technical Solution
[10] In order to accomplish the object of the invention, a shift control method in incorrectness of a gear ratio for an automatic transmission, includes: detecting whether shift is completed with an engine on; determining incorrectness of a gear ratio after the shift is completed; shifting a shift range to a substitute shift range that is lower than the present shift range when the incorrectness of a gear ratio is detected; monitoring continuously the incorrectness of a gear ratio after the shift to the substitute shift range is completed; and shifting the shift range to another substitute shift range that is lower than the substitute shift range when the incorrectness of a gear ratio is re-detected.
Advantageous Effects
[11] According to the shift control method in incorrectness of a gear ratio for an automatic transmission of the invention, when a problem of incorrectness of a gear ratio is generated while a vehicle travels, shift control to a substitute shift range that makes normal operation possible, and when an error is generated while the vehicle travels at the substitute shift range, shift control to another shift range is performed by continuously monitoring the incorrectness of a gear ratio. Further, as long as an error due to the incorrectness of a gear ratio is generated, the sequential shift controls for the limp home are performed until the another substitute shift range becomes a first stage to secure the minimum traveling of the vehicle..
[12] That is, it is possible to give improved reliability to the limp home for various errors, by varying substitute shift ranges that are set for the limp home for the incorrectness of a gear ratio. Brief Description of the Drawings
[13] FIG. 1 is a flowchart illustrating a shift control method in incorrectness of gear ratio for an automatic transmission according to the invention. Mode for the Invention
[14] Before describing the configuration of the invention, it should be understood that the rotational speed of an input shaft of the automatic transmission is detected by an input
shaft speed sensor that detects the number of rotations of a turbine of a torque converter and the rotational speed of an output shaft is detected by an output shaft speed sensor that detects the number of rotations with respect to a differential drive gear corresponding to the output shaft of the automatic transmission.
[15] As shown in the figure, when the engine is started and the vehicle travels, a transmission control unit detects the vehicle speed with respect to opening of a throttle valve and performs shift control on the basis of a predetermined optimal shift pattern.
[16] Then, the transmission control unit detects whether the shift is completed (SlO).
[17] Subsequently, when it is determined that the shift is completed, it is detected whether the input shaft speed sensor and the output shaft speed sensor are in normal states (S12).
[18] Further, when it is determined that the input shaft speed sensor and the output shaft speed sensor are in normal states, an error, incorrectness of a gear ratio, is detected (S14).
[19] When it is determined that the incorrectness of a gear ratio is generated, shift control to a substitute shift range is performed (S 16).
[20] Further, after the shift control to the substitute shift range is performed, it is detected whether the present shift range is the first stage (S 18).
[21] When it is determined that the present shift range is not the first stage, the above operations are repeated.
[22] However, when it is determined that the present shift range is the first stage, shift control is finished.
[23] That is, according to the invention, when it is detected that the shift control is completed with the engine started and the incorrectness of a gear ratio is detected by continuously monitoring an error, i.e. the incorrectness of a gear ratio, after the shift is completed, shift control from the present shift range to a substitute shift range that is lower than the present shift range is performed. Further, when the incorrectness of a gear ratio is re-detected even after the shift to the lower substitute shift range, shift control to another substitute shift range that is lower than the substitute shift range is performed, and these shift controls to substitute shift ranges are repeated until the present shift range is the first stage.
[24] Further, in detecting the incorrectness of a gear ratio, by comparing the difference of the number of rotations of the turbine that has been estimated and the number of rotations of the turbine that has been measured with a set value, when the difference is smaller than the set value, a normal state is determined, and when the difference is larger than the set value, it is determined that incorrectness of a gear ratio corresponding to an error is generated.
[25] The measured number of rotations of the turbine is a measured value detected by the
input shaft speed sensor and the estimated number of rotations of the turbine is an estimated value calculated in consideration of the measured value detected by the output shaft speed sensor and the gear ratio at the present shift range.
[26] Further, the set value is determined by an experimental value that makes the difference between the estimated number of rotations of the turbine and the measured number of rotations of the turbine not be a base for determining generation of the incorrectness of a gear ratio in common cases, that is, an experimental value that includes a tolerance in which the present shift condition is determined as the normal condition. In a common traveling section, the set value is generally determined by a value within about 5 to 10% of the present number of rotations of the turbine.
[27] On the other hand, the substitute shift range that is set when the incorrectness of a gear ratio is detected is set to a shift range that is one-state lower than the present traveling shift range, which is preparation for providing shift ranges that can be substituted when the incorrectness of a gear ratio is re-generated.
[28] That is, according to the invention, shifting the shift range to lower substitute shift ranges when the incorrectness of a gear ratio is detected is repeated until the substitute shift range becomes the first stage, as long as the incorrectness of a gear ratio is generated.
[29] Further, when the substitute shift range becomes the first stage, the transmission control unit finishes the shift control without more hydraulic control, which is because the hydraulic control is not needed any more. Finishing the hydraulic control means that hydraulic pressure of 100% is provided to friction elements that operate at the first stage. That is, it is performed to prevent other problems due to unnecessary additional control of the transmission control unit by making the transmission control unit perform duty control in order to apply operational power of 100% to a power terminal of a solenoid of a hydraulic control valve that provides a fastening pressure to friction elements corresponding to the hydraulic control such that the fastening pressure from the hydraulic control valve to the corresponding friction elements is applied as a line pressure and then unnecessary pressure control is not performed any more.
[30] Further, it should be understood that normal shift control is performed unless incorrectness of a gear ratio is not generated in the step (S 14) of detecting the incorrectness of a gear ratio (S20).
[31] Further, after the incorrectness of gear ratio is generated and the shift control to the substitute shift range is performed, when an error of the incorrectness of a gear ratio is not generated any more during continuously monitoring the incorrectness of a gear ratio and the substitute shift range, i.e. the present shift range is higher than the first stage, normal shift control is performed at the other shift ranges than the shift range where the incorrectness of a gear ratio is generated while the vehicle travels (S20).
[32] For example, if the incorrectness of a gear ratio is generated at a fourth stage and the substitute shift range is determined as a third stage, when shift from the third stage is required while the vehicle travels, shift control is performed in the other shift ranges than the fourth shift range where the incorrectness of a gear ratio is generated. That is, for a fifth-stage automatic transmission, normal shift control can be performed in fifth, third, second, and first stages, which are substitute shift ranges, other than the fourth stage.