METHOD FOR CONTROLLING SENSE OF SHIFT DIFFERENCE AND 4-WHEEL DRIVE VEHICLE APPYLING THE SAME

Abstract

A 4 wheel drive vehicle removes sense of shift difference through an acceleration shift control mode, and the acceleration shift control mode transfers an independent other drive shaft input torque to a drive shaft not connected to a transmission with respect to a transmission input torque transferred to a drive shaft connected with the transmission, so that a vehicle acceleration in an actual shift section connecting between a fore-section and post-section of the shift can be maintained to be equal to the vehicle acceleration of the fore-section and post-section of the, thereby overcoming the transfer torque change, which is not overcome in a conventional slip control method, speed control method and time control method, when transferring a torque to the drive wheels in the actual shift section and realizing the shift quality without the sense of shift difference.

Claims

1. A method for controlling sense of shift difference, performing an acceleration shift control mode through a controller when shifting during travelling of a vehicle, wherein the acceleration shift control mode transfers an independent other drive shaft input torque to a drive shaft not connected to a transmission with respect to a transmission input torque transferred to a drive shaft connected with the transmission, so that a vehicle acceleration in an actual shift section connecting between a fore-section and post-section of the shift can be maintained to be equal to the vehicle acceleration of the fore-section and post-section of the shift.

2. The method for controlling sense of shift difference of claim 1, wherein, in the acceleration shift control mode, (A) an average value of the vehicle acceleration depending on the vehicle travelling is calculated, it makes before shift section to A, and the A is matched to SP (Shift Phase) of the transmission dividing fore-section and post-section of the actual shift section into a shift preparation section and a shift completion section, respectively, (B) an actual shift section entry is recognized when the A gets out of the shift preparation section, (C) if a transmission transfer torque is calculated after entering into the actual shift section, the transmission input torque and the other drive shaft input torque are outputted by a torque prediction mode using the transmission transfer torque, and (D) if a transmission intervention torque is calculated after entering into the actual shift section, the transmission input torque and the other drive shaft input torque are outputted by a torque intervention mode using the transmission intervention torque.

3. The method for controlling sense of shift difference of claim 2, wherein the average value of the vehicle acceleration is the average of a vehicle acceleration measurement value of a G sensor in the shift preparation section.

4. The method for controlling sense of shift difference of claim 2, wherein the A is a calibration factor having a number greater than 0 and smaller than the actual shift section.

5. The method for controlling sense of shift difference of claim 2, wherein the transmission transfer torque is calculated by using slip being generated inside of the transmission.

6. The method for controlling sense of shift difference of claim 2, wherein, in the torque prediction mode, (C-1) the difference between a driver request torque of the vehicle and the transmission transfer torque is calculated, and the calculated difference value is defined as a first acceleration maintenance control torque, (C-2) the transmission intervention torque is outputted as the transmission input torque in the state of entering into the actual shift section, and the average value of the vehicle acceleration is calculated to an error compensation value by correcting a present vehicle acceleration, and (C-3) the first acceleration maintenance control torque is corrected by the error compensation value to be outputted to the other drive shaft input torque.

7. The method for controlling sense of shift difference of claim 6, wherein the first acceleration maintenance control torque and the error compensation value are summed.

8. The method for controlling sense of shift difference of claim 2, wherein, in torque intervention mode, (D-1) the deference between the driver request torque of the vehicle and the transmission intervention torque is calculated, the calculated difference value is defined as a second acceleration maintenance control torque, (D-2) the transmission intervention torque is outputted as the transmission input torque in the state of entering into the actual shift section, and the average value of the vehicle acceleration is calculated to an error compensation value by correcting a present vehicle acceleration, and (D-3) the second acceleration maintenance control torque is corrected by the error compensation value to be outputted to the other drive shaft input torque.

9. The method for controlling sense of shift difference of claim 8, wherein the second acceleration maintenance control torque and the error compensation value are summed.

10. A 4-wheel drive vehicle, comprising: a controller transferring an independent other drive shaft input torque to a drive shaft not connected to a transmission with respect to a transmission input torque transferred to a drive shaft connected with the transmission, so that a vehicle acceleration in an actual shift section connecting between a fore-section and post-section of the shift can be maintained to be equal to the vehicle acceleration of the fore-section and post-section of the shift when shifting during travelling of a vehicle; a transmission controller controlling the transmission; and a G sensor measuring a vehicle acceleration.

11. The 4-wheel drive vehicle of claim 10, wherein the controller is divided into a torque source controller controlling a torque source 1 generating the transmission input torque and a torque source 2 generating the other drive shaft input torque; and a torque map controller connected with the torque source controller.

12. The 4-wheel drive vehicle of claim 11, wherein the torque map controller is composed of a feedback controller correcting an error of a vehicle acceleration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other aspects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0022] FIGS. 1A and 1B are a flow chart of a method of controlling sense of shift difference using an acceleration shift control mode according to embodiments of the present invention;

[0023] FIG. 2 is an example of a 4-wheel drive vehicle in which an acceleration shift control mode according to embodiments of the present invention is implemented;

[0024] FIG. 3 is an example of a shift process before a 4-wheel drive vehicle according to embodiments of the present invention removes sense of shift difference through the acceleration shift control mode;

[0025] FIG. 4 is an example of a slip feedback controller for generating an acceleration maintenance control torque according to embodiments of the present invention;

[0026] FIG. 5 is an example of a non-slip feedback controller for generating an acceleration maintenance control torque according to embodiments of the present invention; and

[0027] FIG. 6 is an example of a shift process after a 4-wheel drive vehicle according to embodiments of the present invention removes sense of shift difference through the acceleration shift control mod.

DESCRIPTION OF EMBODIMENTS

[0028] One aspect of the present invention provides a system for controlling a wheel-driving motor in an electric 4WD (E-4WD) vehicle. The electric 4WD (E-4WD) vehicle has a motor 20-2 and an engine 20-1. In embodiments, the motor 20-2 and the engine 20-1 operate independently such that they can provide different driving torques to different wheels of the vehicle. In embodiments, a transmission 40 connected to the engine 20-1 drives one or more front wheels 1-1, not a rear wheel. The motor 20-2 drives one or more rear wheels, not a front wheel.

[0029] In embodiments, a controller 30 of the vehicle computes a driver request torque (TQ.sub.driver) based on a driver's input on the acceleration pedal. The controller 30 controls the engine 20-1 and the motor 20-2 to provide the driver request torque (TQ.sub.driver). In embodiments, the controller 30 computes a transmission input torque (TQ.sub.input-1) that the transmission 40 needs to provide to accomplish the driver request torque (TQ.sub.driver) assuming the motor provides its required torque (motor input torque). Further, the controller 30 computes a motor input torque (another drive shaft input torque, TQ.sub.input-2) that the motor needs to provide to accomplish the driver request torque (TQ.sub.driver) assuming the transmission provides its required torque (transmission input torque). The controller controls the engine 20-1 using the transmission input torque and also controls the motor 20-2 using the motor input torque.

[0030] In embodiments, the controller 30 monitors the driver request torque (TQ.sub.driver) and the vehicle's speed and determines whether a predetermined set of conditions for a gear shift is satisfied (S10). When the predetermined set of conditions is satisfied, a transmission controller 50 causes the transmission 40 to make a gear shift. During the gear shift, torque generated from the transmission 40 is not fully transmitted to the front wheel due to a slip inside the transmission 40, which results in transmitting a reduced torque (TQ.sub.transfer) to the front wheel(s). In embodiments, the controller 30 computes the reduced torque (TQ.sub.transfer) based on information from sensors monitoring the operation of the transmission 40 and also based on information from the transmission controller 50.

[0031] In embodiments, the motor input torque (TQ.sub.input-2) is computed in view of the computed reduced torque (TQ.sub.transfer) to compensate the loss of torque in the transmission during the gear shift. In embodiments, in computing the motor input torque for the motor 20-2 (TQ.sub.input-2), the controller 30 computes a feedforward torque (TQ.sub.feedforward-1) using the driver request torque (TQ.sub.driver) and the computed reduced torque (TQ.sub.transfer) (S50 in FIG. 1B). In embodiments, in calculating the motor input torque of the motor 20-2 (TQ.sub.input-2) the controller further considers the vehicle's acceleration measured by an acceleration sensor 70 (S52 in FIG. 1B).

[0032] Referring to FIGS. 1 A and 1B, a method for sense of shift difference may perform an acceleration shift control mode between a step S10 of determining whether shift is necessary and a shift completion step S70. In the acceleration shift control mode, the calculation of variable values for the acceleration shift control may be achieved such as S20, predictability determination of a transfer torque TQ.sub.transfer by slip inside of a transmission when moving from a shift preparation section SP((Shift Phase)=A)) to an actual shift section such as S30 and S40 may be achieved, and then, the other drive shaft input torque TQ.sub.input-2 of the other drive shaft (not connected with a transmission, for example, rear wheels) may be changed such as S50 or S60 in a state that a transmission input torque TQ.sub.input-1 of a drive shaft (connected with the transmission, for example front wheels) is in constant. As the result, the acceleration shift control mode may overcome the structural limits of not avoiding the transfer torque change when transferring a torque to the drive wheels in an actual shift section other than a slip control shift method, a speed control shift method and a time control shift method by equally maintaining the acceleration in before and after shift and the actual shift section.

[0033] Referring to FIG. 2, a 4WD vehicle 1 may include E_4WD system 10 (Electric 4-wheel Drive system), an automatic transmission or a double clutch transmission type transmission 40, and G sensor 70 for detecting an acceleration of a vehicle. The E_4WD system 10 may include a torque source 1 20-1 (for example, an engine) transferring a power to front wheels 1-1, a torque source 220-2 (for example, a motor) transferring a power to rear wheels 1-2, a torque source controller 30 for controlling individually or synthetically controlling the torque source 1 20-1 and the torque source 220-2, a transmission controller 50 for controlling the transmission 40 connected to the torque source 1 20-1, and a torque map controller 60 connected to the torque source controller 30 in order to carry out the acceleration shift control mode.

[0034] Particularly, the torque map controller 60 may be composed of a feedback controller for correcting the error between an average vehicle acceleration and a present vehicle acceleration in order to satisfy an average vehicle acceleration in the actual shift section, may calculate an acceleration maintenance control torque TQ.sub.feedback (for example, TQ.sub.feedback-1, TQ.sub.feedback-2) and, for this, may apply PID control or various kinds of control algorithm. Examples of the feedback controller are described in detail through FIGS. 4 and 5 below.

[0035] The E_4WD system 10 may connect the front wheels 1-1 with the transmission 40, the transmission 40 with the torque source 1 20-1, the rear wheels 1-2 with the torque source 2 20-2, and the torque source controller 30 with the torque map controller 60 via hardware, and connect the torque source controller 30 with the torque source 1 20-1 and the torque source 2 20-2, the torque source controller 30 with the torque source controller 30, the transmission controller 50 with the transmission 40, and the torque map controller 60 with the G sensor 70 via communication network.

[0036] Hereinafter, an embodiment of the method for controlling sense of shift difference using the acceleration shift control mode will be described in detail with reference to FIG. 3 to FIG. 6. A control subject of the acceleration shift control mode is the torque source controller 30 connected to the torque map controller 60 and will be explained as a controller. A control subject of the acceleration shift control mode is the torque source 220-2 but may include the torque source 1 20-1, if necessary.

[0037] The step S10 may determine, by the controller, whether shift conditions are satisfied or not in a state that the 4WD vehicle 1 applying the E_4WD system 10 is travelling. For this, the controller may monitor the change of the driver request torque TQ.sub.driver or the change of a vehicle speed V and then, determine shift conditions satisfaction through the change degrees. In this regard, the driver request torque TQ.sub.driver means the sum of the torque source 1 20-1 and the torque source 2 20-2, the vehicle speed V means the travelling speed of the 4WD vehicle 1 and the shift conditions satisfaction means that the transmission controller 50 changes the shift stages of the transmission 40.

[0038] As the result, the controller enters into the step S20 in a state of shift conditions satisfaction while continuing to monitor such as the step S10-1.

[0039] The step S20 may calculate variable values applied to the acceleration shift control by the controller, and the step S30 may detect, by the controller, whether entering the shift preparation section of shift phase SP or not.

[0040] Referring to the shift process of FIG. 3, the shift phase SP may be divided into a shift preparation section, an actual shift section and a shift completion section from the SP line for a transmission input speed of a shift line, and it is known from an acceleration line that a vehicle acceleration measurement value is significantly lowered in the actual shift section. Particularly, the shift phase SP may be divided into numbers greater than 0 in the shift preparation section, the actual shift section and the shift completion section, and the number sizes have the relationship of shift preparation section<the actual shift section<the shift completion section. In this regard, < is a sign of inequality that represents the size of two values.

[0041] Therefore, the controller may detect the driver request torque TQ.sub.driver through a present vehicle speed, a present gear stage and an amount of moving an accelerator pedal track, and so on, and calculate an average vehicle acceleration value G.sub.avg as an average value of a vehicle acceleration measurement value measured by the G sensor. As the result, the torque source 1 20-1 and the torque source 2 20-2 may be distributed based on the decided driver request torque TQ.sub.driver. Furthermore, the controller may determine that the shift conditions satisfaction state is converted into the shift preparation state from the relationship of SP>A. In this regard, the SP is the shift phase, the A represents before shift phase matched to the shift preparation section among the shift preparation section, the actual shift section and the shift completion section of the SP as a calibration factor having a number greater than 0, and > is a sign of inequality that represents the size of two values.

[0042] Therefore, the non-satisfaction of SP>A means that the SP does not leave the shift preparation section, and that the vehicle acceleration measurement value measured by the G sensor 70 in the shift preparation section is calculated to the average vehicle acceleration value G.sub.avg.

[0043] As the result, as the satisfaction of SP>A means that the SP leave the shift preparation section and then, enters into the actual shift section, the controller enters into the step S40, thereby converting the shift preparation section into the shift starting state.

[0044] The step S40 may determine, by the controller, whether the transfer torque TQ.sub.transfer by slip inside of the transmission is predicted or not. The reason for this is because the slip occurred inside of the transmission 40 when moving from the shift preparation section to the actual shift section, predicts transfer torque TQ.sub.transfer which the transmission 40 transfers to the drive shaft (front wheels 1-1). For this, the controller may use monitoring data for the transmission 40 or cooperatively control with the transmission controller 50.

[0045] As the result, the controller may convert into a torque prediction mode of the steps of S50 and S52 when predicting the transfer torque TQ.sub.transfer by slip while covert into a torque intervention mode of the steps of S60 and S62 when not predicting the transfer torque TQ.sub.transfer by slip. Therefore, the controller may change the other drive shaft input torque TQ.sub.input-2 transferred to the drive shaft of the rear wheels 1-2 from the torque source 2 20-2 depending on whether predicting the transfer torque TQ.sub.transfer by slip of the transmission 40 or not.

[0046] Performing the torque prediction mode is implemented as follows.

[0047] The step S50 may calculate, by the controller, a first acceleration maintenance control torque TQ.sub.feedforward-1 transferred to the drive shaft of the rear wheels 1-2. For this, the control may apply the relationship of TQ.sub.feedforward-1=TQ.sub.driverTQ.sub.transfer. In this regard, the TQ.sub.feedforward-1 is the first acceleration maintenance control torque, the TQ.sub.driver is the drive request torque, TQ.sub.transfer is the transmission transfer torque predicted by slip of the transmission 40 at the controller or the transmission controller 50, = is a sign of equality meaning that two values are equal, and is a calculation sign calculating a difference between two values. At this case, the prediction of the TQ.sub.transfer by slip may be realized in a conventional method of the transmission control field.

[0048] Therefore, the TQ.sub.feedforward-1 may be calculated by the value obtained by subtracting the TQ.sub.transfer from the TQ.sub.driver.

[0049] The step S52 may distribute, by the controller, a power to the front wheels and the rear wheels according to the actual shift section entry. For this, the control controls the torque source 1 20-1 so as to transfer the transmission input torque TQ.sub.input-1 to the drive shaft of the front wheels 1-1 connected with the transmission 40, and controls the torque source 2 20-2 so as to transfer the other drive shaft input torque TQ.sub.input-2 to the drive shaft of the rear wheels 1-2 not connected with the transmission 40.

[0050] Referring to FIG. 4, the torque map controller 60 may be composed of a slip feedback controller 60-1, and the controller may generate the transmission input torque TQ.sub.input-1 and the other drive shaft input torque TQ.sub.input-2 in conjunction with the slip feedback controller 60-1.

[0051] Concretely, by applying the relationship of TQ.sub.input-1=TQ.sub.intervention to the transmission input torque TQ.sub.input-1, the controller may calculate monitoring data for the transmission 40 or produce an output for generating the transmission intervention torque TQ.sub.intervention provided from the transmission controller 50. By applying the relationship of TQ.sub.input-2=TQ.sub.feedforward-1+G.sub.avg error compensation value G.sub.avg.sub._.sub.compensation to the other drive shaft input torque TQ.sub.input-2, the controller satisfies the average vehicle acceleration G.sub.avg in the actual shift section through the error correction of the average vehicle acceleration and the present vehicle acceleration and then, generates an output for producing the other drive shaft input torque TQ.sub.input-2.

[0052] Performing the torque intervention mode is implemented as follows.

[0053] The step S60 may calculate, by the controller, a second acceleration maintenance control torque TQ.sub.feedforward-2 transferred to the drive shaft of the rear wheels 1-2. For this, the control may apply the relationship of TQ.sub.feedforward-2=TQ.sub.driverTQ.sub.intervention. In this regard, the TQ.sub.feedforward-2 is the second acceleration maintenance control torque, the TQ.sub.driver is the drive request torque, and TQ.sub.intervention is a transmission transfer torque directly calculated by the controller or the transmission controller 50 through a transmission monitoring data or a setting map because of unpredictability by slip of the transmission 40. At this case, the calculation of the TQ.sub.intervention may be realized in a conventional method of the transmission control field.

[0054] Therefore, the TQ.sub.feedforward-2 may calculated by subtracting the TQ.sub.intervention from the TQ.sub.driver.

[0055] The step S62 may distribute, by the controller, a power to the front wheels and the rear wheels, respectively, according to the actual shift section entry. For this, the control controls the torque source 120-1 so as to transfer the transmission input torque TQ.sub.input-1 to the drive shaft of the front wheels 1-1 connected with the transmission 40, and controls the torque source 2 20-2 so as to transfer the other drive shaft input torque TQ.sub.input-2 to the drive shaft of the rear wheels 1-2 not connected with the transmission 40.

[0056] Referring to FIG. 5, the torque map controller 60 may be composed of a non-slip feedback controller 60-2, and the controller may generate the transmission input torque TQ.sub.input-1 and the other drive shaft input torque TQ.sub.input-2 in conjunction with the non-slip feedback controller 60-2.

[0057] Concretely, by applying the relationship of TQ.sub.input-1=TQ.sub.intervention to the transmission input torque TQ.sub.input-1, the controller may calculate monitoring data for the transmission 40 or produce an output for generating the transmission intervention torque TQ.sub.intervention provided from the transmission controller 50. By applying the relationship of TQ.sub.input-2=TQ.sub.feedforward-2+G.sub.avg error compensation value G.sub.avg.sub._.sub.compensation to the other drive shaft input torque TQ.sub.input-2, the controller satisfies the average vehicle acceleration G.sub.avg in the actual shift section through the error correction of the average vehicle acceleration and the present vehicle acceleration and then, generates an output for producing the other drive shaft input torque TQ.sub.input-2.

[0058] The step S70 may determine, by the controller, a shift completion in conjunction with the transmission controller 50. The step S70 means that the SP enters into the shift completion section from the actual shift section, thereby stopping the output of the other drive shaft input torque TQ.sub.input-2.

[0059] Referring to FIG. 6, it is known from the torque line that the other drive shaft input torque TQ.sub.input-2 and the transmission input torque TQ.sub.input-1 are compensated each other in the actual shift section. It is known form the acceleration line that the average vehicle acceleration G.sub.avg in the actual shift section is maintained to be substantially equal even in the fore-section and post-section of the shift divided into the shift preparation section and the shift completion section. As the result, the acceleration shift control mode may overcome the transfer torque change, which is not overcome in a conventional slip control method, speed control method and time control method, when transferring a torque to the drive wheels in the actual shift section, thereby realizing the shift quality without the sense of shift difference.

[0060] As described above, the 4WD vehicle according to an embodiment of the present invention may remove the sense of shift difference through the acceleration shift control mode, and the acceleration shift control mode transfers the independent other drive shaft input torque TQ.sub.input-2 to the drive shaft not connected to the transmission with respect to the transmission input torque TQ.sub.input-1 transferred to the drive shaft connected to the transmission, so that the vehicle acceleration in the actual shift section connecting between the fore-section and post-section of the shift of the transmission can be maintained to be equal to the vehicle acceleration of the fore-section and post-section of the shift, thereby overcoming the transfer torque change, which is not overcome in a conventional slip control method, speed control method and time control method, when transferring a torque to the drive wheels in the actual shift section and realizing the shift quality without the sense of shift difference.

[0061] The embodiments discussed in the present disclosure are embodiments which may enable a person (hereinafter referred to as a skilled person in the relevant technology), who has a typical knowledge in a technology field that the present invention belongs to, to execute the present invention easily, but the present invention is not limited to the aforesaid embodiments and the attached drawings, and hence this does not result in limiting the scope of right in this invention. Therefore, it will be apparent to a skilled person in the relevant technology that several transposition, transformation, and change is possible within a scope of not deviating from the technological thought in the present invention and it is obvious that a easily changeable part by a skilled person in the relevant technology is included within the scope of right in the present invention as well.