CN104390000B - Electric automobile three keeps off the downshift course control method for use of line traffic control automatic transmission - Google Patents

Abstract

The invention discloses a kind of electric automobile three and keep off the downshift course control method for use of line traffic control automatic transmission, the method is determined a need for being down to a gear by two gears, being down to two grades by three gears by detection D position switch signal, the GES v of vehicle speed sensor, the opening amount signal α of motor accelerator pedal position sensor by ECU, and the electromagnetic clutch electrical current carrying out each downshift process controls.This downshift course control method for use not only can avoid the interruption of motor input power during downshift, and can avoid shift shock, it is achieved the steady downshift of line traffic control automatic transmission.

Description

Control method for downshift process of three-speed wire-controlled automatic transmission of electric vehicle

technical field

The invention relates to a control method of an automatic transmission, more precisely, a control method for a downshift process of a three-speed wire-controlled automatic transmission of an electric vehicle.

Background technique

Automatic transmissions are widely used in various vehicles such as automobiles, electric vehicles, and construction machinery. The existing automatic transmissions mainly include hydromechanical automatic transmission (AT), metal belt continuously variable automatic transmission (CVT), mechanical automatic transmission (AMT) and dual clutch automatic transmission (DCT).

The above-mentioned four types of automatic transmissions all adopt electronically controlled hydraulic servo devices to realize the control of the shifting process, which has complex structure, high cost and increased control difficulty and complexity. In particular, the executive mechanism of DCT includes: oil supply mechanism composed of hydraulic pump, hydraulic valve and accumulator, shift actuator driven by hydraulic pressure or electric motor, clutch control mechanism driven by hydraulic pressure or electric motor. These hydraulic control mechanisms make the overall structure of the transmission complex, the cost is high, and the control difficulty and complexity are increased.

With the gradual maturity of automotive electronic technology and automatic control technology and the wide application of automotive network communication technology, automotive wire control technology has become the future development trend of automobiles; The controller replaces the mechanical and hydraulic systems, and the driver's manipulation action is converted into an electrical signal through the sensor, which is input to the electronic control unit, and the control signal is generated to drive the actuator to perform the required operation. Automobile control-by-wire technology can reduce the complexity of components, reduce hydraulic and mechanical transmission devices, and at the same time, the flexibility of wiring layout expands the free space of automobile design.

In the three-speed wire-controlled automatic transmission for electric vehicles, one end of the input gear is connected to the transmission input shaft, and the other end of the input gear is sequentially connected with the first-speed high-speed gear, the second-speed high-speed gear, the third-speed high-speed gear, and the reverse idler along the circumferential outer side of the gear. The wheels are constantly meshed; the first gear high speed gear, the second gear high speed gear, the third gear high speed gear, and the reverse gear high speed gear pass through the first gear electromagnetic clutch, the second gear electromagnetic clutch, the third gear electromagnetic clutch, the reverse gear electromagnetic clutch and the first gear spindle, the second gear Gear main shaft, third gear main shaft, and reverse gear main shaft are connected; first gear main shaft, second gear main shaft, third gear main shaft, and reverse gear main shaft are distributed on the outer periphery of the intermediate shaft of the transmission; the electronic control unit controls the high-speed gear of each gear through the electromagnetic clutch of each gear. The engagement and disengagement of the driving gear realizes the wire-controlled shift control of the three-speed wire-controlled automatic transmission of electric vehicles, and has the advantages of compact structure, wire-controlled power shifting, and no mechanical or hydraulic shifting parts.

In order to ensure the smooth shifting of the three-speed automatic transmission by wire for electric vehicles and avoid the interruption of the input power of the motor and the shock of shifting during the shifting process, it is necessary to control the shifting process of the three-speed automatic transmission by wire for electric vehicles.

Contents of the invention

The object of the present invention is to provide a downshifting process control method of a three-speed by-wire automatic transmission of an electric vehicle that can avoid the interruption of the input power of the motor and the impact of the shifting during the shifting process, and can realize the smooth downshifting of the vehicle. A method for controlling the downshifting process of a three-speed by-wire automatic transmission for an electric vehicle. The control device for the three-speed by-wire automatic transmission for an electric vehicle that realizes the control method includes an electric motor, a D gear switch, a vehicle speed sensor, an accelerator pedal position sensor for an electric motor, and an electric motor. control unit, first gear electromagnetic clutch, second gear electromagnetic clutch, and third gear electromagnetic clutch, in the electronic control unit, the regular curve of the first gear down from the second gear and the second gear down from the third gear are stored in advance.

Technical scheme of the present invention is as follows:

After the electric motor is started, the electronic control unit is powered on, and the downshift process control method of the three-speed by-wire automatic transmission of the electric vehicle starts to run. The control method includes the following steps:

Step 1. The electronic control unit detects the D gear switch signal, the vehicle speed signal v of the vehicle speed sensor, and the opening signal α of the motor accelerator pedal position sensor;

Step 2. Determine whether to engage the D gear: when the electronic control unit detects that the D gear switch signal is on, go to step 3; otherwise, when the electronic control unit detects that the D gear switch signal is not on, go to step 1;

Step 3. Judging whether the second gear needs to be downshifted to the first gear: When the electronic control unit detects that the vehicle speed signal v of the vehicle speed sensor and the opening signal α of the accelerator pedal position sensor of the electric motor satisfy the downshifting rule curve of the third gear automatic transmission by wire of the electric vehicle When the downshift point on the second-gear-down-first-gear law curve is judged that the second gear needs to be downshifted to the first gear, go to step 4; otherwise, when the electronic control unit detects the vehicle speed signal v of the vehicle speed sensor and the opening of the accelerator pedal position sensor of the electric motor When the speed signal α does not meet the downshift point on the second gear down first gear regular curve in the downshift regular curve of the three-speed wire-controlled automatic transmission of the electric vehicle, it is judged that the downshift from the second gear to the first gear is unnecessary, and proceed to step 6;

Step 4. The second gear down to the first gear process control: the electronic control unit follows the first gear electromagnetic clutch current function I _1a (t)={I ₁ , 0≤t≤T _δ ;kI ₁ +I ₁ (1-k) (tT _δ )/(T ₂₁ -T _δ ), T _δ <t≤T ₂₁ } controls the energizing current of the first-gear electromagnetic clutch, and at the same time, according to the energizing current function of the second-gear electromagnetic clutch I _2a (t)={I ₂ , 0≤t≤βT _δ ; 0,βT _δ <t≤T ₂₁ } controls the energizing current of the second-gear electromagnetic clutch, where: I ₁ is the rated value of the energizing current of the first-gear electromagnetic clutch, and I ₂ is the second-gear electromagnetic clutch The rated value of the energized current, T _δ is the minimum energization time required to eliminate the separation gap of the first gear electromagnetic clutch, T ₂₁ is the fixed control period for the second gear down to the first gear, k is the engagement strength coefficient, and β is the delay separation time coefficient;

Step 5. Determine whether the duration t of the control process of downgrading from the second gear to the first gear is less than the fixed control period T ₂₁ of the downgrade from the second gear to the first gear: when the duration t of the control process of downgrading from the second gear to the first gear is less than the fixed control period of downgrading from the second gear to the first gear At period T ₂₁ , it is judged that the control process of downgrading from the second gear to the first gear has not ended, and return to step 4; otherwise, when the duration t of the control process of the second gear down to the first gear is greater than or equal to the fixed control period T ₂₁ , it is judged that the second gear is down to the first gear and the control process is over, and returns to step 1;

Step 6. Judging whether the third gear needs to be downshifted to the second gear: When the electronic control unit detects that the vehicle speed signal v of the vehicle speed sensor and the opening signal α of the accelerator pedal position sensor of the electric motor satisfy the downshifting rule curve of the third gear automatic transmission by wire of the electric vehicle When the downshift point on the third-gear and second-gear law curve is judged that the third gear needs to be downgraded to the second gear, go to step 7; When the speed signal α does not satisfy the downshift point on the third gear downshift regular curve in the downshift regular curve of the three-gear automatic transmission by wire automatic transmission of the electric vehicle, it is judged that the downshift from the third gear to the second gear is unnecessary, and the process returns to step 1;

Step 7. The third gear is downgraded to the second gear process control: the electronic control unit uses the current function of the second gear electromagnetic clutch I _2b (t)={I ₂ , 0≤t≤T _δ ;kI ₂ +I ₂ (1-k) (tT _δ )/(T ₃₂ -T _δ ), T _δ <t≤T ₃₂ } controls the energizing current of the second-gear electromagnetic clutch, and at the same time, according to the energizing current function of the third-gear electromagnetic clutch I _3b (t)={I ₃ 0 ≤t≤βT _δ ; 0,βT _δ <t≤T ₃₂ } controls the energized current of the third-gear electromagnetic clutch, where: I ₂ is the rated value of the energized current of the second-gear electromagnetic clutch, and I ₃ is the current of the third-gear electromagnetic clutch The rated value of the energized current, T _δ is the minimum energization time required to eliminate the separation gap of the second gear electromagnetic clutch, T ₃₂ is the fixed control period for the third gear down to the second gear, k is the engagement strength coefficient, and β is the delay separation time coefficient;

Step 8. Judging whether the duration t of the control process of downgrading from the third gear to the second gear is less than the fixed control period _T32 of the downgrade from the third gear to the second gear: when the duration t of the control process of downgrading from the third gear to the second gear is less than the fixed control period of downgrading from the third gear to the second gear At period _T32 , it is judged that the control process of downgrading from third gear to second gear has not ended, and return to step 7; otherwise, when the duration t of the control process of downgrading from third gear to second gear is greater than or equal to the fixed control period _T32 of downgrading from third gear to second gear , it is judged that the third gear down to the second gear control process is over, and returns to step 1.

After the driver turns off the switch, the electric control unit is powered off, and the downshift process control method of the three-speed by-wire automatic transmission of the electric vehicle ends its operation.

In the process control of step 4 down from second gear to first gear and step 7 down from third gear to second gear process control, joint strength coefficient k is a fixed value set, k=0.5～0.8; delayed separation time coefficient β is set Set a fixed value, β=0.8～1.2.

In the process control of step 4 down from the second gear to the first gear, the fixed control cycle T ₂₁ is a set fixed value, T ₂₁ =500-1000ms.

In the above step 7, the third gear is downgraded to the second gear process control, the fixed control period T ₃₂ of the third gear down to the second gear is a set fixed value, T ₃₂ =400-700ms.

Compared with the prior art, the present invention has the advantages of:

(1) The downshifting process control method of the three-speed by-wire automatic transmission for electric vehicles of the present invention can quickly eliminate the separation gap of the electromagnetic clutch of the low gear during the downshifting process, and gradually increase the energizing current of the electromagnetic clutch of the low gear , to realize the smooth increase of the transmission torque of the electromagnetic clutch in the low gear, thereby avoiding the shifting shock phenomenon during the downshifting process;

(2) The downshifting process control method of the three-speed by-wire automatic transmission for electric vehicles of the present invention can control the high-gear electromagnetic clutch to ensure reliable engagement before the low-gear electromagnetic clutch transmits torque during the downshift process, The power transmission is maintained, and after the electromagnetic clutch of the low gear starts to transmit power, the electromagnetic clutch of the high gear disengages quickly, thereby avoiding the power interruption phenomenon during the downshifting process.

Description of drawings

Fig. 1 is a schematic structural diagram of the control device and the transmission device of the first gear and the reverse gear of the three-speed wire-controlled automatic transmission of the electric vehicle according to the embodiment of the present invention.

Fig. 2 is a schematic structural diagram of the control device and the transmission device for the second gear and the third gear of the three-speed wire-by-wire automatic transmission of the electric vehicle according to the embodiment of the present invention.

Fig. 3 is a flowchart of a downshift process control method for a three-speed by-wire automatic transmission of an electric vehicle according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of a downshift regularity curve of a three-speed by-wire automatic transmission of an electric vehicle according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of the first gear electromagnetic clutch energizing current function I _1a (t) curve and the second gear electromagnetic clutch energizing current function I _2a (t) curve of the three-speed wire-by-wire automatic transmission of the embodiment of the present invention.

Fig. 6 is a schematic diagram of the current function I _2b (t) curve of the second-gear electromagnetic clutch and the curve of the current function I _3b (t) of the third-gear electromagnetic clutch of the third-gear by-wire automatic transmission of an electric vehicle according to the embodiment of the present invention.

In the figure: 1. Motor 2. Transmission housing 23. Transmission input shaft 24. Transmission intermediate shaft 25. Transmission output shaft 3. Input gear 31. Reverse gear idler 41. First gear electromagnetic clutch 411. First gear electromagnetic clutch slip ring 412. First gear electromagnetic clutch brush 42. Second gear electromagnetic clutch 421. Second gear electromagnetic clutch slip ring 422. Second gear electromagnetic clutch brush 43. Third gear electromagnetic clutch 431. Third gear electromagnetic clutch slip ring 432. Third gear electromagnetic clutch Electric brush 44. Reverse gear electromagnetic clutch 441. Reverse gear electromagnetic clutch slip ring 442. Reverse gear electromagnetic clutch brush 4Z1. First gear main shaft 4Z2. Second gear main shaft 4Z3. Third gear main shaft 4Z4. Reverse gear main shaft 51. First gear high speed gear 52. Second gear high speed gear 53. Third gear high speed gear 54. Reverse gear high speed gear 61. First gear driving gear 62. Second gear driving gear 63. Third gear driving gear 64. Reverse gear driving gear 71. First gear driven gear 72 . Second gear driven gear 73. Third gear driven gear 74. Reverse gear driven gear 91. Sun gear 92. Planetary gear 93. Ring gear 94. Planet carrier 100. Electronic control unit 100a. First gear control output terminal 100b. Second gear control output terminal 100c. Third gear control output terminal 100d. Reverse gear control output terminal VSS. Vehicle speed sensor D-SW. D gear switch M-APS. Motor accelerator pedal position sensor D ₂₁ . _32. The regular curve of third gear down and second gear.

detailed description

Below in conjunction with the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention are described in detail. Obviously, the described embodiments are only part of the embodiments of the present invention, not all embodiments; based on the present invention Embodiments, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

A method for controlling the downshifting process of a three-speed by-wire automatic transmission for an electric vehicle. The control device for realizing the three-speed by-wire automatic transmission for an electric vehicle in the embodiment of the present invention includes a motor 1, a D gear switch D-SW, a vehicle speed sensor VSS, a motor Accelerator pedal position sensor M-APS, electronic control unit 100, first gear electromagnetic clutch ₄₁ , second gear electromagnetic clutch 42, third gear electromagnetic clutch 43; The law curve D ₃₂ of downshifting from third gear to second gear.

Housing 2 is fixedly installed with a gear electromagnetic clutch brush 412, a second gear electromagnetic clutch brush 422, a third gear electromagnetic clutch brush 432, a reverse gear electromagnetic clutch brush 442, a first gear electromagnetic clutch brush 412, a second gear electromagnetic clutch Electric brush 422, third gear electromagnetic clutch electric brush 432, reverse gear electromagnetic clutch electric brush 442 respectively with first gear electromagnetic clutch slip ring 411, second gear electromagnetic clutch slip ring 421, third gear electromagnetic clutch slip ring 431, reverse gear electromagnetic clutch slip ring The ring 441 keeps sliding contact; the connecting terminal of the first gear electromagnetic clutch brush 412, the connecting terminal of the second gear electromagnetic clutch brush 422, the connecting terminal of the third gear electromagnetic clutch brush 432, and the connecting terminal of the reverse gear electromagnetic clutch brush 442 respectively The first gear control output terminal 100a, the second gear control output terminal 100b, the third gear control output terminal 100c, and the reverse gear control output terminal 100d of the electronic control unit 100 are connected through wires.

The electronic control unit 100 controls the first gear electromagnetic clutch 41, Engagement and separation of the second gear electromagnetic clutch 42, the third gear electromagnetic clutch 43, and the reverse gear electromagnetic clutch 44; the electronic control unit 100 controls the first gear electromagnetic clutch brush 412, the second gear electromagnetic clutch brush 422, and the third gear electromagnetic clutch brush 432. The energized voltage or current of the reverse gear electromagnetic clutch brush 442 controls the engagement and separation speeds of the first gear electromagnetic clutch 41, the second gear electromagnetic clutch 42, the third gear electromagnetic clutch 43, and the reverse gear electromagnetic clutch 44.

Realize that the transmission device of the three-gear-by-wire automatic transmission for electric vehicles of the present invention comprises input gear 3, transmission input shaft 23, transmission intermediate shaft 24, transmission output shaft 25, housing 2; one end of input gear 3 and transmission input shaft 23 One end is connected; the other end of the transmission input shaft 23 is connected with the motor 1; the transmission intermediate shaft 24 is sequentially fixedly connected with a third gear driven gear 73, a second gear driven gear 72, a first gear driven gear 71, and a reverse gear driven gear 74 A sun gear 91 is also fixedly connected to one end of the transmission intermediate shaft 24 away from the input gear 3 .

The input gear 3 is in constant mesh with the first-speed high-speed gear 51, the second-speed high-speed gear 52, the third-speed high-speed gear 53, and the reverse idler gear 31 along its gear circumferential outer side, and the reverse idler gear 31 is in constant mesh with the reverse high-speed gear 54. .

The first gear high speed gear 51, the second gear high speed gear 52, the third gear high speed gear 53, and the reverse gear high speed gear 54 are respectively connected with the passive end of the first gear electromagnetic clutch 41, the passive end of the second gear electromagnetic clutch 42, and the passive end of the third gear electromagnetic clutch 43. end, the passive end of reverse gear electromagnetic clutch 44 is connected; Gear main shaft 4Z1, second gear main shaft 4Z2, third gear main shaft 4Z3, reverse gear main shaft 4Z4 are connected with first gear driving gear 61, second gear driving gear 62, third gear driving gear 63, reverse gear driving gear 64; first gear driving gear 61, Second gear driving gear 62, third gear driving gear 63, reverse gear driving gear 64 are in constant mesh with first gear driven gear 71, second gear driven gear 72, third gear driven gear 73, reverse gear driven gear 74 respectively.

The sun gear 91 is constantly meshed with the planetary gear 92, and the planetary gear 92 is also constantly meshed with the ring gear 93. The planetary gear 92 is rolled and installed on the planet carrier 94 through its central bearing hole, and the planet carrier 94 is fixed on the transmission case 2. The ring gear 93 is fixed on one end of the transmission output shaft 25 by a spline, and the other end of the transmission output shaft 25 is used as the power output end of the transmission.

The power transmission routes of each forward gear and reverse gear of the three-speed wire-by-wire automatic transmission of the electric vehicle according to the embodiment of the present invention will be further described below with reference to FIG. 1 and FIG. 2 .

First-gear transmission: the electronic control unit 100 controls the first-gear electromagnetic clutch 41 to be energized and engaged, and the other electromagnetic clutches are de-energized and separated. The torque of the motor 1 is transmitted to the input gear 3 through the transmission input shaft 23, and the input gear 3 further transmits the torque to the first gear The high-speed gear 51 transmits the power to the sun gear 91 through the engagement of the first gear electromagnetic clutch 41 through the engagement of the first gear driving gear 61 and the first gear driven gear 71, and finally outputs the power to the transmission output shaft through the central spline of the ring gear 93 25. Realize first gear transmission.

Second gear transmission: the electronic control unit 100 controls the second gear electromagnetic clutch 42 to be energized and engaged, and the other electromagnetic clutches are deenergized and separated. The torque of the motor 1 is transmitted to the input gear 3 through the transmission input shaft 23, and the input gear 3 further transmits the torque to the second gear The high-speed gear 52 transmits power to the sun gear 91 through the engaged second-speed electromagnetic clutch 42 through the engagement of the second-speed driving gear 62 and the second-speed driven gear 72, and finally outputs the power to the transmission output shaft through the central spline of the ring gear 93 25. Realize the second gear transmission.

Three-speed transmission: the electronic control unit 100 controls the third-speed electromagnetic clutch 43 to be energized and engaged, and the other electromagnetic clutches are de-energized and separated. The torque of the motor 1 is transmitted to the input gear 3 through the transmission input shaft 23, and the input gear 3 further transmits the torque to the third gear. The high-speed gear 53 transmits the power to the sun gear 91 through the meshing of the third-speed driving gear 63 and the third-speed driven gear 73 through the engaged third-speed electromagnetic clutch 43, and finally outputs the power to the transmission output shaft through the central spline of the ring gear 93 25. Realize the third gear transmission.

Reverse gear transmission: the electronic control unit 100 controls the reverse gear electromagnetic clutch 44 to be energized and engaged, and the other electromagnetic clutches are powered off and separated. The torque of the motor 1 is transmitted to the input gear 3 through the transmission input shaft 23, and the input gear 3 further transmits the torque to the reverse gear The idler gear 31 and the high-speed reverse gear 54 transmit power to the sun gear 91 through the engaged reverse electromagnetic clutch 44 through the meshing of the reverse drive gear 64 and the reverse driven gear 74, and finally pass through the central spline of the ring gear 93. The key is output to the transmission output shaft 25 to realize reverse gear transmission.

Neutral gear: the electronic control unit 100 controls the electromagnetic clutch 41 of the first gear, the electromagnetic clutch 42 of the second gear, the electromagnetic clutch 43 of the third gear, and the electromagnetic clutch 44 of the reverse gear, all of which are in the power-off and separated state to realize the neutral gear.

The flow chart of the downshifting process control method of the third-gear automatic transmission by wire for electric vehicles of the present invention is shown in Figure 3. After the motor 1 is started, the electronic control unit 100 is powered on, and the downshifting process of the three-speed automatic transmission by wire for electric vehicles is controlled. Method begins to run, and this control method comprises the following steps:

Step S1, the electronic control unit 100 detects the signal of the D gear switch D-SW, the vehicle speed signal v of the vehicle speed sensor VSS, and the opening signal α of the motor accelerator pedal position sensor M-APS;

Step S2, judging whether the D gear is engaged: when the electronic control unit 100 detects that the D gear switch D-SW signal is on, proceed to step S3; otherwise, when the electronic control unit 100 detects that the D gear switch D-SW signal is not connected When it is passed, proceed to step S1;

Step S3, judging whether the second gear needs to be downgraded to the first gear: the downshift regular curve of the third gear by wire automatic transmission of the electric vehicle shown in Figure 4, when the electronic control unit 100 detects the vehicle speed signal v of the vehicle speed sensor VSS and the electric motor accelerator pedal When the opening degree signal α of the position sensor M-APS satisfies the downshift point on the second gear down first gear regular curve D ₂₁ in the downshift regular curve of the three-gear automatic transmission by wire of the electric vehicle, it is judged that the second gear needs to be downshifted to the first gear. Proceed to step S4; otherwise, when the electronic control unit 100 detects that the vehicle speed signal v of the vehicle speed sensor VSS and the opening signal α of the motor accelerator pedal position sensor M-APS do not satisfy the second gear in the downshift law curve of the three-speed automatic transmission by wire of the electric vehicle When the downshift point on the first gear rule curve D ₂₁ is determined, it is judged that the second gear is not required to be downgraded to the first gear, and step S6 is performed;

Step S4, second gear down to first gear process control: the electronic control unit 100 presses the first gear electromagnetic clutch 41 energized current function I _1a (t)={I ₁ , 0≤t≤T _δ ; kI ₁ +I ₁ (1- k)(tT _δ )/(T ₂₁ −T _δ ), T _δ <t≤T ₂₁ } controls the energizing current of the first gear electromagnetic clutch 41, and at the same time according to the second gear electromagnetic clutch 42 energizing current function I _2a (t)= {I ₂ , 0≤t≤βT _δ ; 0,βT _δ <t≤T ₂₁ } controls the energizing current of the second gear electromagnetic clutch 42, where: I ₁ is the rated value of the energizing current of the first gear electromagnetic clutch 41, I ₂ is the rated value of the energized current of the second-gear electromagnetic clutch 42, T _δ is the minimum energization time required to eliminate the separation gap of the first-gear electromagnetic clutch 41, T ₂₁ is the fixed control period for the second gear down to the first gear, and k is the joint strength coefficient , β is the delayed separation time coefficient;

Step S5, judging whether the duration t of the control process of downgrading from the second gear to the first gear is less than the fixed control period _T21 of the downgrading from the second gear to the first gear: when the duration t of the control process of downgrading from the second gear to the first gear is less than the fixed control period of downgrading from the second gear to the first gear During the period _T21 , it is judged that the control process of downgrading from the second gear to the first gear has not ended, and return to step S4; otherwise, when the duration t of the control process of downgrading from the second gear to the first gear is greater than or equal to the fixed control period T ₂₁ of the second gear down to the first gear , it is judged that the control process of downshifting from the second gear to the first gear is over, and returns to step S1;

Step S6, judging whether the third gear needs to be downgraded to the second gear: the downshift regular curve of the third gear by wire automatic transmission of the electric vehicle shown in Figure 4, when the electronic control unit 100 detects the vehicle speed signal v of the vehicle speed sensor VSS and the motor accelerator pedal When the opening degree signal α of the position sensor M-APS satisfies the downshift point on the third gear down second gear regular curve D ₃₂ in the downshift law curve of the three-speed wire-controlled automatic transmission of the electric vehicle, it is judged that the third gear needs to be downshifted to the second gear. Proceed to step S7; otherwise, when the electronic control unit 100 detects that the vehicle speed signal v of the vehicle speed sensor VSS and the opening degree signal α of the motor accelerator pedal position sensor M-APS do not satisfy the third gear in the downshift law curve of the three-speed automatic transmission by wire of the electric vehicle When shifting down to the downshift point on the second gear regular curve D ₃₂ , it is judged that the third gear is not required to be downgraded to the second gear, and the process returns to step S1;

Step S7, third gear down to second gear process control: the electronic control unit 100 presses the second gear electromagnetic clutch 42 energization current function I _2b (t)={I ₂ , 0≤t≤T _δ ; kI ₂ +I ₂ (1- k)(tT _δ )/(T ₃₂ −T _δ ), T _δ <t≤T ₃₂ } controls the energizing current of the second-gear electromagnetic clutch 42, and simultaneously presses the energizing current function I _3b (t) of the third-gear electromagnetic clutch 43 = {I ₃ , 0≤t≤βT _δ ; 0,βT _δ <t≤T ₃₂ } controls the energizing current of the third gear electromagnetic clutch 43, where: I ₂ is the rated value of the energizing current of the second gear electromagnetic clutch 42, I ₃ is the rated value of the energized current of the third-gear electromagnetic clutch 43, T _δ is the minimum energization time required to eliminate the separation gap of the second-gear electromagnetic clutch 42, T ₃₂ is the fixed control period when the third gear is lowered to the second gear, and k is the joint strength coefficient , β is the delayed separation time coefficient;

Step S8, determine whether the duration t of the control process of downgrading from third gear to second gear is less than the fixed control period _T32 of downgrading from third gear to second gear: when the duration t of the control process of downgrading from third gear to second gear is less than the fixed control period of downgrading from third gear to second gear At period _T32 , it is judged that the control process of downgrading from third gear to second gear has not ended, and return to step S7; otherwise, when the duration t of the control process of downgrading from third gear to second gear is greater than or equal to the fixed control period _T32 of downgrading from third gear to second gear , it is judged that the third gear is downgraded to the second gear and the control process ends, and the process returns to step S1.

After the driver turns off the switch, the electronic control unit 100 is powered off, and the downshift process control method of the three-speed by-wire automatic transmission of the electric vehicle ends its operation.

In this embodiment, the joint strength coefficient k is taken as 0.6; the delayed separation time coefficient β is taken as 1.0; the fixed control period T ₂₁ of the second gear down to the first gear is taken as _700ms ; the fixed control period T32 of the third gear down to the second gear is taken as 550 ms; the minimum energization time T _{1 δ} required to eliminate the separation gap of the first gear electromagnetic clutch 41 and the minimum energization time T _{2 δ} required to eliminate the separation gap of the second gear electromagnetic clutch 42 are both taken as 250 ms.

Below in conjunction with Fig. 4, Fig. 5, step S3 of the embodiment of the present invention is further described to determine whether the second gear is downgraded to the first gear and step S4 the second gear is downgraded to the first gear process control process:

As shown in Figure 4, the embodiment of the present invention is a schematic diagram of the _{downshift regularity} curve of the three-gear-by-wire automatic transmission of the electric vehicle. and the accelerator pedal opening signal α running to point A(28,50), the electronic control unit 100 judges that point A is the second gear down on the first gear down law curve D ₂₁ according to the downshift regular curve of the electric vehicle's third-gear automatic transmission by wire Downshift point, and then carry out second gear down to first gear process control;

As shown in Figure 5 , the first gear electromagnetic clutch energized current function I _1a (t) curve and the second gear electromagnetic clutch energized current function I _2a (t) curve schematic diagram of the third gear by wire automatic transmission of the embodiment of the present invention, the first gear Electromagnetic clutch 41 current function I _1a (t)={I ₁ , 0≤t≤250ms; 0.6·I ₁ +0.4·I ₁ ·(t-250)/450, 250ms<t≤700ms}, second gear electromagnetic Clutch 42 energization current function I _2a (t)={I ₂ , 0≤t≤250ms; 0, 250ms<t≤700ms}.

Below in conjunction with Fig. 4, Fig. 6 further illustrate the step S6 of the embodiment of the present invention to judge whether the third gear is downgraded to the second gear and step S7 the third gear is downgraded to the second gear process control process:

As shown in FIG. 4 , the schematic diagram of the downshift regularity curve of the third-gear automatic transmission by wire of the embodiment of the present invention, when the vehicle speed signal v and the accelerator pedal opening signal α run to point B(72,50), the electronic control unit 100 Determine that point B is the downshift point on the third gear down second gear law curve D ₃₂ according to the downshift law curve of the three-gear-by-wire automatic transmission of the electric vehicle, and then carry out the third gear down to the second gear process control;

As shown in Figure 6, the second gear electromagnetic clutch energized current function I _2b (t) curve and the third gear electromagnetic clutch energized current function I _3b (t) curve schematic diagram of the third gear by wire automatic transmission of the embodiment of the present invention, the second gear Electromagnetic clutch 42 energized current function I _2b (t)={I ₂ , 0≤t≤250ms; 0.6·I ₂ +0.4·I ₂ ·(t-250)/300, 250ms<t≤550ms}, third gear electromagnetic Clutch 43 energization current function I _3b (t)={I ₃ , 0≤t≤250ms; 0, 250ms<t≤550ms}.

The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and can also be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. Variations.

Claims (4)

1. A downshift process control method of three gears by wire automatic transmission for electric vehicles, the control device of the three gears by wire automatic transmission for electric vehicles that realizes the control method includes electric motor (1), D gear switch (D-SW), Vehicle speed sensor (VSS), electric motor accelerator pedal position sensor (M-APS), electronic control unit (100), electromagnetic clutch for first gear (41), electromagnetic clutch for second gear (42), electromagnetic clutch for third gear (43). The control unit (100) stores in advance the regular curve (D ₂₁ ) of the second gear down and the first gear down, and the third gear down and the second gear regular curve (D ₃₂ ), characterized in that the control method includes the following steps: Step 1. The electronic control unit (100) detects the D gear switch (D-SW) signal, the vehicle speed signal v of the vehicle speed sensor (VSS), and the opening signal α of the motor accelerator pedal position sensor (M-APS); Step 2, judging whether to mount the D gear: when the electronic control unit (100) detects that the D gear switch (D-SW) signal is turned on, proceed to step 3; otherwise, when the electronic control unit (100) detects the D gear switch When the (D-SW) signal is not connected, proceed to step 1; Step 3. Judging whether the second gear needs to be downgraded to the first gear: When the electronic control unit (100) detects that the vehicle speed signal v of the vehicle speed sensor (VSS) and the opening signal α of the motor accelerator pedal position sensor (M-APS) meet the requirements of the electric vehicle When the downshift point on the second gear downshift regular curve (D ₂₁ ) of the third gear by wire automatic transmission downshift regular curve curve (D 21 ), it is judged that the second gear needs to be downgraded to the first gear, proceed to step 4; otherwise, when the electronic control unit ( 100) It is detected that the vehicle speed signal v of the vehicle speed sensor (VSS) and the opening signal α of the motor accelerator pedal position sensor (M-APS) do not meet the second gear down first gear rule in the downshift rule curve of the third-gear automatic transmission by wire of the electric vehicle At the downshift point on the curve (D ₂₁ ), it is judged that the second gear is not required to be downshifted to the first gear, and proceed to step 6; Step 4. Process control of second gear down to first gear: the electronic control unit (100) presses the first gear electromagnetic clutch (41) energized current function I _1a (t)={I ₁ , 0≤t≤T _δ ;kI ₁ +I ₁ (1-k)(tT _δ )/(T ₂₁ -T _δ ), T _δ <t≤T ₂₁ } controls the energizing current of the first-gear electromagnetic clutch (41), and at the same time energizes the second-gear electromagnetic clutch (42) The current function I _2a (t)={I ₂ , 0≤t≤βT _δ ; 0,βT _δ <t≤T ₂₁ } controls the energizing current of the second-gear electromagnetic clutch (42), where: I ₁ is the first-gear electromagnetic The rated value of the energized current of the clutch (41), I ₂ is the rated value of the energized current of the second gear electromagnetic clutch (42), and T _δ is the required minimum energized time for eliminating the separation gap of the first gear electromagnetic clutch (41), T ₂₁ is the fixed control period from the second gear down to the first gear, k is the joint strength coefficient, and β is the delayed separation time coefficient; Step 5. Determine whether the duration t of the control process of downgrading from the second gear to the first gear is less than the fixed control period T ₂₁ of the downgrade from the second gear to the first gear: when the duration t of the control process of downgrading from the second gear to the first gear is less than the fixed control period of downgrading from the second gear to the first gear At period T ₂₁ , it is judged that the control process of downgrading from the second gear to the first gear has not ended, and return to step 4; otherwise, when the duration t of the control process of the second gear down to the first gear is greater than or equal to the fixed control period T ₂₁ , it is judged that the second gear is down to the first gear and the control process is over, and returns to step 1; Step 6. Judging whether the third gear needs to be downgraded to the second gear: when the electronic control unit (100) detects that the vehicle speed signal v of the vehicle speed sensor (VSS) and the opening signal α of the motor accelerator pedal position sensor (M-APS) meet the requirements of the electric vehicle When the downshift point on the third gear downshift regular curve (D ₃₂ ) of the third gear by wire automatic transmission downshift regular curve curve (D 32 ), it is judged that the third gear needs to be downgraded to the second gear, proceed to step 7; otherwise, when the electronic control unit ( 100) It is detected that the vehicle speed signal v of the vehicle speed sensor (VSS) and the opening signal α of the motor accelerator pedal position sensor (M-APS) do not meet the third gear downshifting rule in the downshifting rule curve of the three-speed wire-controlled automatic transmission of the electric vehicle At the downshift point on the curve (D ₃₂ ), it is judged that the third gear is not required to be downshifted to the second gear, and return to step 1; Step 7. The third gear is downgraded to the second gear process control: the electronic control unit (100) presses the second gear electromagnetic clutch (42) to energize the current function I _2b (t)={I ₂ , 0≤t≤T _δ ; kI ₂ +I ₂ (1-k)(tT _δ )/(T ₃₂ -T _δ ), T _δ <t≤T ₃₂ } Control the energizing current of the second-gear electromagnetic clutch (42), and simultaneously press the third-gear electromagnetic clutch (43) to energize The current function I _3b (t)={I ₃ , 0≤t≤βT _δ ; 0,βT _δ <t≤T ₃₂ } controls the energizing current of the third-gear electromagnetic clutch (43), where: I ₂ is the second-gear electromagnetic The rated value of the energized current of the clutch (42), I ₃ is the rated value of the energized current of the third gear electromagnetic clutch (43), T _δ is the required minimum energized time for eliminating the separation gap of the second gear electromagnetic clutch (42), T ₃₂ is the fixed control period from the third gear down to the second gear, k is the joint strength coefficient, and β is the delayed separation time coefficient; Step 8. Judging whether the duration t of the control process of downgrading from the third gear to the second gear is less than the fixed control period _T32 of the downgrade from the third gear to the second gear: when the duration t of the control process of downgrading from the third gear to the second gear is less than the fixed control period of downgrading from the third gear to the second gear At period _T32 , it is judged that the control process of downgrading from third gear to second gear has not ended, and return to step 7; otherwise, when the duration t of the control process of downgrading from third gear to second gear is greater than or equal to the fixed control period _T32 of downgrading from third gear to second gear , it is judged that the third gear down to the second gear control process is over, and returns to step 1. 2. The downshift process control method of the three-gear-by-wire automatic transmission of an electric vehicle as claimed in claim 1, characterized in that, in step 4, the second gear is downgraded to the first gear process control, and in step 7, the third gear is downgraded to the second gear In process control, the joint strength coefficient k is a fixed value set, k=0.5-0.8; the delay separation time coefficient β is a fixed value set, β=0.8-1.2. 3. The downshift process control method of the three-gear-by-wire automatic transmission of an electric vehicle as claimed in claim 1, characterized in that, in the step 4, the second gear is downgraded to the first gear process control, and the second gear is downgraded to the first gear. The gear fixed control cycle T ₂₁ is a fixed value set, T ₂₁ =500～1000ms. 4. The downshift process control method of the three-gear-by-wire automatic transmission of an electric vehicle as claimed in claim 1, characterized in that, in the step 7, the third gear is downgraded to the second gear process control, and the third gear is downgraded to the second gear. The gear fixed control period T ₃₂ is a fixed value set, T ₃₂ =400-700ms.