Hybrid vehicle and method for controlling its speed limit

Abstract

The present disclosure relates to a hybrid vehicle and a method for controlling speed limit thereof. The method includes: determining a smaller value between a vehicle speed and a target speed limit as a virtual vehicle speed; determining a larger value between a first APS value and a second APS value as a virtual APS value; when it is desired to switch from a first mode of maintaining the SOC of a battery at the target speed limit to a second mode of depleting the SOC, switching to the second mode at a time point when an actual APS value and the second APS value become different; and determining a transmission gear by applying the determined virtual vehicle speed and the determined virtual APS value to one of a first shift mode and a second shift mode.

Description

Technical Field

[0001] The present invention relates to a hybrid vehicle and a method for controlling its speed limit. Background Art

[0002] A speed limit device is a safety driving system that limits acceleration so that a driver drives a vehicle at a speed not exceeding a predetermined speed limit to prevent speeding. As a representative example of a speed limit device, a manual speed limit assist (MSLA) function can be used.

[0003] Generally, during the execution of the MSLA function, braking control for deceleration is not performed. Therefore, the vehicle may accelerate above the predetermined speed on a downhill road, and different from smart cruise control (SCC), the relative position / speed of the vehicle ahead is not considered. Thus, the driver must visually check the road ahead.

[0004] Recently, functions such as camera-based SLA (CSLA) using speed limit information recognized by a front camera and intelligent SLA (ISLA) using speed limit information from a navigation system have been developed and applied.

[0005] In the evaluation items of the New European Driving Cycle (NEDC), these speed limit devices are defined in "Safety Assist - Speed Assist Systems - Speed Control Function". A description will be made with reference to Figure 1 this.

[0006] Figure 1 The shown curve graph represents the evaluation criteria of the speed limit device.

[0007] In Figure 1 , V set represents the set speed of the speed limit device. In addition, V stab represents the convergence speed of the speed limit device, which is defined as the average speed within 20 seconds after 10 seconds from reaching "V set - 10 kph", and must satisfy the range of "V set - 5 < V stab < V set ".

[0008] Hybrid electric vehicles (HEVs) generally use two types of power sources, and the two types of power sources are mainly an engine and an electric motor. Compared with vehicles having only an internal combustion engine, such hybrid electric vehicles have excellent fuel efficiency, high power performance, and reduced exhaust emissions, and thus are now being actively developed.

[0009] A hybrid vehicle can operate in two drive modes depending on which power train is driven. In the electric vehicle (EV) mode, the hybrid vehicle is driven only by an electric motor, while in the hybrid electric vehicle (HEV) mode, the hybrid vehicle is driven by both an electric motor and an engine. The hybrid vehicle can switch between the two modes according to the conditions during driving.

[0010] Figure 2 FIG. is a block diagram showing an example of the power train structure of a parallel hybrid vehicle.

[0011] Figure 2 FIG. shows the power train of a parallel hybrid vehicle adopting a parallel hybrid system, in which a drive motor 140 and an engine clutch (EC) 130 are installed between an internal combustion engine (ICE) 110 and a transmission 150.

[0012] In this vehicle, when the driver steps on the accelerator pedal after starting, first, the motor 140 is driven using the power of the battery in a state where the engine clutch 130 is open, and the power of the motor causes the wheels to move via the transmission 150 and the final drive (FD) 160 (i.e., in the EV mode). When the vehicle gradually accelerates and thus requires a greater driving force, the starter generator motor 120 can operate to drive the engine 110.

[0013] Therefore, when the rotational speeds of the engine 110 and the motor 140 are equal to each other, the engine clutch 130 engages, so that the vehicle is driven by the engine 110 and the motor 140 or only by the engine 110 (i.e., switching from the EV mode to the HEV mode). When a predetermined engine shutdown condition is satisfied, i.e., when the vehicle decelerates, the engine clutch 130 opens and the engine 110 stops (i.e., switching from the HEV mode to the EV mode). In addition, in a hybrid vehicle, when the vehicle brakes, the driving force of the wheels can be converted into electrical energy, so that the battery can be charged using this electrical energy, and such an energy recovery mechanism is called regenerative braking or brake energy regeneration.

[0014] When the engine 110 is started, the starter generator motor 120 serves as a starter motor, and after the engine 110 is started or when the engine 110 is shut down and the rotational energy of the engine 110 is recovered, the starter generator motor 120 serves as a generator. Therefore, the starter generator motor 120 can be called a Hybrid Starter Generator (HSG), and in some cases can be called an auxiliary motor.

[0015] In addition to the above drive mode classification based on the powertrain, particularly in the case of a plug-in hybrid vehicle (PHEV), the drive mode of the plug-in hybrid vehicle can be classified into a charge depleting (CD) mode and a charge sustaining (CS) mode based on the change in the state of charge (SOC) of the battery. Generally, in the CD mode, the plug-in hybrid vehicle does not utilize the power of the engine but uses the power of the battery to drive the motor for driving, and in the CS mode, the vehicle utilizes the power of the engine to prevent the battery SOC from decreasing. The transition between the CD mode and the CS mode can be performed based on the SOC of the battery or based on the driving load according to the setting.

[0016] In a hybrid vehicle, the hybrid control unit is set as a superior control unit for overall control of the powertrain (i.e., the engine 110 and the motor 140), and the above speed limit function is generally achieved by torque control through the hybrid control unit. This will be described with reference to Figure 3 this.

[0017] Figure 3 is a block diagram showing an example of the configuration of the control unit for implementing the speed limit function of a hybrid vehicle.

[0018] Referring to Figure 3 , in the hybrid control unit HCU, in order to execute the speed limit function, the speed controller converts the set speed limit V set into the corresponding torque Tq controller , and the value of the accelerator pedal sensor (or accelerator position sensor) APS is converted into the driver demand torque Tq through a predetermined APS-torque conversion map MAP APS . The hybrid control unit HCU determines the smaller value of the two converted torques Tq controller and Tq APS as the speed limit torque Tq slc , converts the speed limit torque Tq slc into a virtual APS value APS vir , and sends the virtual APS value APS vir to the transmission control unit TCU to control the transmission 150.

[0019] In the case of a plug-in hybrid vehicle (PHEV), the transmission control unit TCU determines the transmission gear by applying the virtual APS value APS vir and the current vehicle speed V to the transmission map corresponding to the current set mode among the transmission maps corresponding to the CD mode and the transmission maps corresponding to the CS mode. This will be described with reference to Figure 4Describe two shift maps (shift patterns) used in a plug-in hybrid vehicle (PHEV).

[0020] Figure 4 Show graphs representing the CS shift pattern and the CD shift pattern.

[0021] Refer to Figure 4 , assuming that the engine 110 is started in the CS mode. Therefore, considering the efficiency of the engine 110, the CS shift pattern maintains a low RPM, and in the CD mode, the motor 140 is mainly used. Therefore, considering the efficiency of the motor 140, the CD shift pattern allows a high RPM. Thus, at the same vehicle speed, the same APS value 410 corresponds to the third gear in the CS shift pattern and the second gear in the CD shift pattern, that is, the desired gear can vary according to the current mode.

[0022] A hybrid vehicle that selectively applies two shift maps with different efficiency characteristics is not conducive to applying a speed limit function to the hybrid vehicle. This will be described below with reference to Figure 5A and Figure 5B .

[0023] Figure 5A Show a graph representing an example of the change in vehicle speed, APS value, and drive mode over time when the speed limit function is applied. Figure 5B Show an example of the shift form under the conditions shown in Figure 5A .

[0024] Refer to Figure 5A , if the speed limit function is applied to a hybrid vehicle that selectively applies two shift maps with different efficiency characteristics, the hybrid vehicle is accelerated until the vehicle speed reaches the set speed limit V set , and due to the higher virtual APS value, the CS shift pattern is applied to the hybrid vehicle. Then, when the virtual APS value drops below a specific standard at the mode conversion point 510 where the vehicle speed approaches the set speed limit V set , the hybrid vehicle switches to the CD mode, so the CD shift pattern is applied to the hybrid vehicle. However, as described above, since braking is not involved in the speed limit function (e.g., the manual speed limit assist (MSLA) function), although the vehicle speed reaches the set speed limit V set and the virtual APS value becomes the lowest value, the vehicle speed still increases, and when the vehicle speed is again below the set speed limit V set , the virtual APS value increases and the vehicle speed converges to the set speed limit V set .

[0025] As Figure 5BAs shown, in terms of speed change, since the CS speed change mode is applied before the mode conversion point 510, when the vehicle speed passes the boundary 520 between the first gear and the second gear, the hybrid vehicle shifts up from the first gear to the second gear, and when the vehicle speed passes the boundary 530 between the second gear and the third gear, it shifts up from the second gear to the third gear. However, when the hybrid vehicle switches to the CD mode at the mode conversion point 510, the CD speed change mode is applied, and there are vehicle speed and virtual APS values between the boundary 540 between the first gear and the second gear and the boundary 550 between the second gear and the third gear. Therefore, the hybrid vehicle downshifts from the third gear to the second gear again. After that, although the vehicle speed exceeds the set speed limit V set and the virtual APS value decreases, the vehicle speed increases and reaches the boundary 550 between the second gear and the third gear. The hybrid vehicle shifts up to the third gear again, and when the vehicle speed decreases again, the hybrid vehicle downshifts to the second gear, resulting in unnecessary frequent shifting (busy shifting). In addition, due to this frequent shifting, the required torque cannot be met, and thus an overshoot of excessive increase in the virtual APS value occurs. And since no braking is involved, after the overshoot occurs, it takes a relatively long time for the vehicle speed to reach the target speed. Therefore, it is difficult to meet the requirements such as those of EURO NCAP. SUMMARY OF THE INVENTION

[0026] Accordingly, the present invention relates to a hybrid vehicle and a method for controlling its speed limit that substantially eliminates one or more problems caused by the limitations and disadvantages of the prior art. Specific embodiments relate to a hybrid vehicle capable of preventing unnecessary speed changes in a state where a speed limit function is set and a method for controlling its driving mode.

[0027] Embodiments of the present invention provide a hybrid vehicle capable of providing a more effective speed limit function and a method for controlling its driving mode.

[0028] Another embodiment of the present invention provides a method that can prevent frequent shifting and overshoot during following a target speed limit when applying a speed limit function to a hybrid vehicle that selectively applies two speed change modes with different efficiency characteristics.

[0029] Other advantages, objects, and features of the embodiments of the present invention will be partially described in the following description, and will be partially obvious to those of ordinary skill in the art after reading the following content, or can be learned from the practice of the present invention. The objects and other advantages of the embodiments of the present invention can be achieved and obtained by the structures specifically pointed out in the written description, its claims, and the drawings.

[0030] To achieve these and other advantages and in accordance with the purposes of the present invention, as embodied and broadly described herein, a method for controlling the speed limit of a hybrid vehicle includes: determining a virtual vehicle speed as the smaller value of the vehicle speed and the target speed limit; determining a virtual APS value as the larger value of a first accelerator position sensor (APS) value corresponding to a constant speed driving load at the target speed limit and a second APS value following the target speed limit; when desiring to switch from a first mode of maintaining the state of charge (SOC) of the battery at the target speed limit to a second mode of depleting the SOC, switching to the second mode at a time point when the actual APS value and the second APS value become different; and determining a transmission gear according to whether switching to the second mode by applying the determined virtual vehicle speed and the determined virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode.

[0031] In another embodiment of the present invention, a method for controlling the speed limit of a hybrid vehicle includes: when the vehicle speed is higher than the target speed limit, correcting the virtual vehicle speed to the target speed limit; when a first APS value corresponding to a constant speed driving load at the target speed limit is less than a second APS value following the target speed limit, correcting the virtual APS value to the first accelerator position sensor (APS) value; when desiring to switch from a first mode of maintaining the state of charge (SOC) of the battery at the target speed limit to a second mode of depleting the SOC, switching to the second mode at a time point when the actual APS value and the second APS value become different; and determining a transmission gear according to whether switching to the second mode by applying the virtual vehicle speed and the virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode.

[0032] In yet another embodiment of the present invention, a hybrid vehicle includes: a hybrid control unit including: a vehicle speed corrector configured to determine a virtual vehicle speed as the smaller value of the vehicle speed and the target speed limit; a virtual APS corrector configured to determine a virtual APS value as the larger value of a first accelerator position sensor (APS) value corresponding to a constant speed driving load at the target speed limit and a second APS value following the target speed limit; and a mode corrector configured to determine to switch to the second mode at a time point when the actual APS value and the second APS value become different when desiring to switch from a first mode of maintaining the state of charge (SOC) of the battery at the target speed limit to a second mode of depleting the SOC; and a transmission control unit configured to determine a transmission gear according to whether switching to the second mode by applying the determined virtual vehicle speed and the determined virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode.

[0033] In a further embodiment of the present invention, a hybrid vehicle includes: a hybrid control unit, comprising: a vehicle speed corrector configured to correct a virtual vehicle speed to a target speed limit when the vehicle speed is higher than the target speed limit; a virtual APS corrector configured to correct a virtual APS value to a first accelerator position sensor (APS) value when a first APS value corresponding to a constant speed driving load at the target speed limit is less than a second APS value following the target speed limit; and a mode corrector configured to determine to switch to a second mode at a time point when an actual APS value and the second APS value become different when it is desired to switch between a first mode of maintaining a state of charge (SOC) of a battery at the target speed limit and a second mode of depleting the SOC; and a transmission control unit configured to determine a transmission gear by applying the virtual vehicle speed and the virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode according to whether to switch to the second mode.

[0034] It should be understood that the above summary and the following detailed description of the embodiments of the present invention are both exemplary and explanatory, and are intended to provide further illustration of the claimed invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings are intended to provide a further understanding of the present invention and are incorporated into and constitute a part of this application. These drawings illustrate embodiments of the present invention and, together with the description, are used to explain the principles of the present invention. In the figures:

[0036] Figure 1 A graph showing evaluation criteria of a speed limit device is shown;

[0037] Figure 2 is a block diagram showing an example of a powertrain structure of a parallel hybrid vehicle;

[0038] Figure 3 is a block diagram showing an example of a configuration of a control unit for implementing a speed limit function of a hybrid vehicle;

[0039] Figure 4 A graph showing curves of a CS shift mode and a CD shift mode is shown;

[0040] Figure 5A A graph showing an example of changes in vehicle speed, APS value, and driving mode over time when applying the speed limit function is shown;

[0041] Figure 5B Shows that in Figure 5A A graph showing an example of a shift pattern under the conditions shown in is shown;

[0042] Figure 6is a block diagram showing an example of a control system of a hybrid vehicle to which an embodiment of the present invention can be applied;

[0043] Figure 7 is a block diagram showing an example of the configuration of a control system that performs speed limit control according to an embodiment of the present invention;

[0044] Figure 8 is a view showing the operation of a vehicle speed corrector according to an embodiment of the present invention;

[0045] Figure 9 is a view showing the operation of a virtual APS corrector according to an embodiment of the present invention;

[0046] Figure 10 is a view showing the operation of a CD / CS mode corrector according to an embodiment of the present invention;

[0047] Figure 11A shows a graph representing an example of changes in vehicle speed, virtual APS value, and driving mode over time when applying a speed limit function according to an embodiment of the present invention;

[0048] Figure 11B shows that in Figure 11A a graph representing an example of a shift pattern under the conditions shown in; and

[0049] Figure 12 is a flowchart showing an example of a process for controlling speed limit according to an embodiment of the present invention. Detailed Description of the Invention

[0050] Now, preferred embodiments of the present invention will be described in detail. Examples of these preferred embodiments are shown in the drawings. However, the disclosure of the present invention is not limited to the embodiments described herein, and various modifications can be made. In the drawings, for the purpose of clearly describing the present invention, descriptions of elements unrelated to the embodiments of the present invention are omitted, and even if the same or similar elements are shown in different drawings, they are denoted by the same reference numerals.

[0051] In the following description of the embodiments, it will be understood that when a component "includes" an element, unless otherwise stated, the component may further include other elements, and the presence of these other elements is not excluded. Further, in the following description of the embodiments, parts denoted by the same reference numerals represent the same elements.

[0052] Before describing a hybrid vehicle and a method for controlling its speed limit according to an embodiment of the present invention, a control system of a hybrid vehicle to which an embodiment of the present invention can be applied will be described.

[0053] Figure 6 It is a block diagram showing an example of a control system of a hybrid vehicle to which an embodiment of the present invention can be applied.

[0054] Referring to Figure 6 , in a hybrid vehicle to which an embodiment of the present invention can be applied, an internal combustion engine 110 can be controlled by an engine control unit 210, a starting generator motor 120 and a drive motor 140 (motor 120 / 140) can be controlled by a motor control unit (MCU) 220, and an engine clutch 130 can be controlled by a clutch control unit 230. Here, the engine control unit 210 can be referred to as an engine management system (EMS). In addition, a transmission 150 can be controlled by a transmission control unit 250.

[0055] Each control unit is connected to a hybrid control unit (HCU) 240, a superior control unit for controlling the entire mode conversion process, and can provide information required to change the drive mode, control the engine clutch 230 during gear shifting, and / or control the stop of the engine 110 to the hybrid control unit 240, or perform an operation corresponding to a control signal from the hybrid control unit 240 under the control of the hybrid control unit 240.

[0056] More specifically, the hybrid control unit 240 determines whether to perform a conversion between an EV mode and an HEV mode or a conversion between a CD mode and a CS mode according to the driving state of the vehicle. For example, the hybrid control unit 240 judges the time point when the engine clutch 130 is separated (open), and controls the hydraulic pressure (if the engine clutch 130 is a wet engine clutch) or controls the torque capacity (if the engine clutch 130 is a dry engine clutch) when the engine clutch 130 is separated. In addition, the hybrid control unit 240 can judge the state of the engine clutch 130 (lock-up, slip, open, etc.), and control the time point when the fuel injection of the engine 110 stops. In addition, the hybrid control unit 240 can send a torque command for controlling the torque of the starting generator motor 120 to the motor control unit 220 to control the stop of the engine 110, thereby controlling the recovery of the rotational energy of the engine 110. In addition, the hybrid control unit 240 can control the subordinate control units to judge the mode conversion conditions and perform a conversion between modes while controlling the drive mode conversion.

[0057] Of course, the connection relationships between the above control units, the functions of each control unit, and the division between each control unit are merely exemplary, and it will be obvious to those skilled in the art that the control units are not limited to the above elements. For example, the hybrid control unit 240 may be implemented such that its corresponding functions can be executed by any one control unit other than the hybrid control unit 240, or may be implemented such that its corresponding functions can be assigned to two or more of the control units other than the hybrid control unit 240.

[0058] Figure 6 The above-described configuration shown is merely an example of the configuration of a hybrid vehicle, and the hybrid vehicle to which the embodiments of the present invention can be applied is not limited to this configuration.

[0059] Hereinafter, based on the above configuration of the hybrid vehicle, the speed limit control according to an embodiment of the present invention will be described.

[0060] An embodiment of the present invention proposes to prevent shifting caused by a change in vehicle speed at a speed greater than or equal to a set speed limit through vehicle speed correction, prevent shifting caused by overshoot by correcting the minimum value of the virtual APS value to the APS value when driving at a constant speed at the set speed limit; and when it is desired to switch between modes, prevent shifting caused by a change in the shifting mode by performing the mode switch in advance. For this purpose, reference will be made to Figure 7 Describe the configuration of the control system.

[0061] Figure 7 is a block diagram showing an example of the configuration of a control system that performs speed limit control according to an embodiment of the present invention.

[0062] Refer to Figure 7 , according to an embodiment of the present invention, the hybrid control unit 240 may include a speed controller 241, an APS-torque conversion map 242, a comparator 243, a torque-APS conversion map 244, a vehicle speed corrector 245, a virtual APS corrector 246, and a CD / CS mode corrector 247.

[0063] Here, the speed controller 241, the APS-torque conversion map 242, the comparator 243, and the torque-APS conversion map 244 are similar to the Figure 3 corresponding configurations, and thus their detailed descriptions will be omitted. The shifting MAP 251 of the transmission control unit 250 has a CD shifting mode and a CS shifting mode, similar to the Figure 3 configuration. However, different from the Figure 3 configuration, the torque-APS conversion map 244 converts the virtual APS value APS virSent to the virtual APS corrector 246 instead of sending the virtual APS value APS vir directly to the transmission control unit 250.

[0064] In the following, the remaining elements 245, 246, and 247 of the hybrid control unit 240 will be described.

[0065] First, reference will be made to Figure 8 describe the vehicle speed corrector 245.

[0066] Figure 8 is a view showing the operation of the vehicle speed corrector according to an embodiment of the present invention.

[0067] Referring to Figure 8 , the vehicle speed corrector 245 outputs the smaller value between the set speed limit V set and the vehicle speed V as the virtual speed V vir , and the virtual speed V vir is sent to the transmission control unit 250 instead of the existing vehicle speed V. Thus, although the actual vehicle speed V exceeds the set speed limit V set , the virtual speed V vir remains at the set speed limit V set Thereafter, therefore, shifting due to an increase in the vehicle speed V can be prevented.

[0068] Next, reference will be made to Figure 9 describe the virtual APS corrector 246.

[0069] Figure 9 is a view showing the operation of the virtual APS corrector according to an embodiment of the present invention.

[0070] Referring to Figure 9 , the virtual APS corrector 246 calculates the constant speed driving load at the set speed limit V set , and then obtains the APS value corresponding to the corresponding torque through the torque-APS conversion map 244. Here, the constant speed driving load can be calculated by a map determined in advance through testing or by using the rolling resistance and air resistance coefficients of the vehicle, and the constant speed driving load is corrected according to the slope or road surface information. The virtual APS corrector 246 outputs the larger value between the APS value for constant speed driving at the set speed limit V set and the virtual APS value APS determined by the torque-APS conversion map 244 as the corrected virtual APS value APS vir , and the corrected virtual APS value APS vir，mody instead of the existing virtual APS value APS vir，mody is sent. virSent to the transmission control unit 250. In other words, it can be considered that when the APS value AP corresponding to the constant-speed driving load SS is greater than the virtual APS value APS vir , the APS value sent to the transmission control unit 250 is corrected.

[0071] Thus, the minimum value of the APS value APS sent to the transmission control unit 250 vir，mody becomes the APS value for constant-speed driving at the set speed limit V set . Therefore, since the virtual APS value APS vir becomes 0 after exceeding the target speed limit due to overshoot, shifting during the process of returning to the normal state can be prevented.

[0072] Next, the CD / CS mode corrector 247 will be described with reference to Figure 10 .

[0073] Figure 10 is a view showing the operation of the CD / CS mode corrector according to an embodiment of the present invention.

[0074] Referring to Figure 10 , the CD / CS mode corrector 247 can determine whether the vehicle is to be switched to the CD mode by comparing the driving load for constant-speed driving at the set speed limit V set with the standard power used as a standard for switching between the CD mode and the CS mode according to the current SOC. This is because the vehicle is in the CS mode during acceleration, but when the constant-speed driving load at the set speed limit V set is less than the standard power (i.e., standard power > constant-speed driving load), the vehicle will switch to the CD mode. Therefore, the CD / CS mode corrector 247 can determine to switch to the CD mode at an earlier time point when the actual APS value and the virtual APS value APS vir become different (i.e., Tq APS >Tq controller ). Thus, upshifting to the gear in the CD mode can be performed until the vehicle reaches the set speed limit V set , thereby preventing frequent shifting.

[0075] The effect of the above speed limit control will be described with reference to Figure 11A and Figure 11B .

[0076] Figure 11A shows a graph representing an example of the change in vehicle speed, virtual APS value, and driving mode over time when applying the speed limit function according to an embodiment of the present invention, Figure 11B shows that in Figure 11AA graph showing an example of a variable speed form under the conditions shown.

[0077] Referring to Figure 11A , if a speed limit function is applied to a hybrid vehicle that selectively applies two variable speed maps with different efficiency characteristics, the hybrid vehicle is accelerated until the vehicle speed reaches the set speed limit V set , and due to the higher virtual APS value, the CS variable speed mode is applied to the hybrid vehicle. However, in this embodiment, when the driving load at the target speed limit is lower than the standard power that is the standard for switching between the CS mode and the CD mode, the hybrid vehicle switches to the CD mode in advance at the time point when the virtual APS value and the driver APS value become different, and corrects the minimum value of the virtual APS value to the APS value corresponding to the constant speed driving load at the target speed limit. Therefore, even when the vehicle speed exceeds the set speed limit V set , the virtual APS value does not become 0, thereby preventing frequent gear shifting due to the change of the virtual APS value.

[0078] Furthermore, as Figure 11B shown, the vehicle speed input to the transmission control unit 250 does not exceed the set speed limit V set , so there is no gear shifting caused by exceeding the set speed limit V set , and the mode conversion is advanced, and therefore there is no gear shifting caused by the mode conversion near the set speed limit V set .

[0079] Next, the process for controlling the speed limit according to the above-described embodiment of the present invention will be described with reference to Figure 12 .

[0080] Figure 12 is a flowchart showing an example of a process for controlling the speed limit according to an embodiment of the present invention. In Figure 12 , a situation is assumed in which the virtual APS value APS has been obtained by operating the speed controller 241, the APS-torque conversion map 242, the comparator 243, and the torque-APS conversion map 244 vir .

[0081] Referring to Figure 12 , when the vehicle speed V is higher than the set speed limit V set (yes in S1210), the vehicle speed corrector 245 of the hybrid control unit 240 corrects the virtual vehicle speed V vir to be input to the transmission control unit 250 to the smaller value of the vehicle speed V and the set speed limit V set (S1220).

[0082] In addition, when compared with at the set speed limit V setThe APS value APS corresponding to the constant-speed driving load under ss is greater than the virtual APS value APS vir When (in S1230, it is "Yes"), the virtual APS corrector 246 of the hybrid control unit 240 can correct the virtual APS value to be input to the transmission control unit 250 to the APS value APS corresponding to the constant-speed driving load ss (that is, the APS value vir，mody )(S1240).

[0083] In addition, when the driving mode MODE under the set speed limit is expected SS is the CD mode (in S1250, it is "Yes"), the CD / CS mode corrector 247 of the hybrid control unit 240 can determine that the hybrid vehicle is switched to the CD mode in advance at the time point when the actual APS value and the virtual APS value APS vir become different (S1260).

[0084] The effects of the speed limit control according to the above embodiments are as follows.

[0085] The vehicle speed limit device does not generate braking torque for deceleration. Therefore, when an overshoot occurs during the operation of the vehicle speed limit device, the vehicle speed exceeds the target speed limit for a relatively long time. If the state where the vehicle speed exceeds the target speed limit continues for a long time, the marketability of the vehicle speed limit device may deteriorate severely, and it may lead to negative results in NCAP. In addition, with the continuous development of speed limit devices that utilize cameras and navigation systems such as intelligent speed limit assist (ISLA), the speed limit control according to these embodiments can prevent frequent gearshifts, thereby improving the ability to follow the target speed. Therefore, the marketability of the speed limit device can be improved.

[0086] Although the above embodiments have been described based on hybrid vehicles, particularly plug-in hybrid vehicles (PHEVs), the same effects can be obtained if the operations of the vehicle speed corrector 245 and the virtual APS corrector 246 are applied to a general internal combustion engine, except for the operation of the CD / CS mode corrector 247.

[0087] The present invention can be implemented as computer-readable code in a computer-readable recording medium recording a program. Such a computer-readable recording medium can include all types of recording media capable of storing computer system-readable data. For example, the computer-readable recording medium can include a hard disk drive (HDD), a solid-state disk (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc.

[0088] As is apparent from the above description, a hybrid vehicle and a method for controlling its speed limit according to at least one embodiment of the present invention can provide a more effective vehicle speed limit function.

[0089] In particular, when applying a vehicle speed limit function to a hybrid vehicle that selectively applies two shift patterns with different efficiency characteristics, the method prevents frequent gear shifting and overshoot during following the target speed limit, so that the hybrid vehicle can reach the target speed limit effectively, quickly, and stably.

[0090] It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Therefore, if the modifications and variations of the present invention fall within the scope of the appended claims and their equivalents, the present invention is intended to cover these modifications and variations of the present invention.

Claims

1. A method for controlling the speed limit of a hybrid vehicle, comprising: Determining the smaller value between the vehicle speed and the target speed limit as the virtual vehicle speed; Determining the larger value between the first APS value corresponding to the constant-speed driving load at the target speed limit and the second APS value following the target speed limit as the virtual accelerator position sensor value, i.e., the virtual APS value; When it is desired to switch from the first mode of maintaining the state of charge (SOC) of the battery at the target speed limit to the second mode of depleting the SOC, switching to the second mode at the time point when the actual APS value and the second APS value become different; And According to whether switching to the second mode, determining the transmission gear by applying the determined virtual vehicle speed and the determined virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode.

2. The method according to claim 1, wherein Determining the virtual APS value includes: Calculating the constant-speed driving load at the target speed limit; and Obtaining the first APS value by applying the constant-speed driving load to a torque-APS conversion map.

3. The method according to claim 1, wherein Switching to the second mode includes: Based on the SOC, judging the standard power for switching between the first mode and the second mode; Judging the constant-speed driving load at the target speed limit; and When the standard power is greater than the constant-speed driving load, judging that the hybrid vehicle is to switch to the second mode.

4. The method according to claim 1, wherein The first mode includes a charge-sustaining mode, i.e., the CS mode; and The second mode includes a discharge mode, i.e., the CD mode.

5. A non-transitory computer-readable recording medium having recorded thereon a program for executing the method according to claim 1.

6. A method for controlling the speed limit of a hybrid vehicle, comprising: When the vehicle speed is higher than the target speed limit, correcting the virtual vehicle speed to the target speed limit; When the first accelerator position sensor value, i.e., the first APS value, corresponding to the constant-speed driving load at the target speed limit is less than the second APS value following the target speed limit, correcting the virtual accelerator position sensor value, i.e., the virtual APS value, to the first APS value; When it is desired to switch from the first mode of maintaining the state of charge (SOC) of the battery at the target speed limit to the second mode of depleting the SOC, switching to the second mode at the time point when the actual APS value and the second APS value become different; And According to whether switching to the second mode, determining the transmission gear by applying the virtual vehicle speed and the virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode.

7. The method according to claim 6, wherein Correcting the virtual APS value includes: Calculating the constant-speed driving load at the target speed limit; and The first APS value is obtained by applying the constant-speed driving load to the torque-APS conversion map.

8. The method according to claim 6, wherein Converting to the second mode includes: Based on the SOC, determining the standard power for conversion between the first mode and the second mode; Determining the constant-speed driving load at the target speed limit; and When the standard power is greater than the constant-speed driving load, determining that the hybrid vehicle is to be converted to the second mode.

9. A non-transitory computer-readable recording medium having recorded thereon a program for executing the method according to claim 6.

10. A hybrid vehicle, comprising: A hybrid control unit, comprising: A vehicle speed corrector that determines the smaller value between the vehicle speed and the target speed limit as the virtual vehicle speed; A virtual accelerator position sensor corrector, i.e., a virtual APS corrector, that determines the larger value between the first APS value corresponding to the constant-speed driving load at the target speed limit and the second APS value following the target speed limit as the virtual APS value; and A mode corrector that, when expecting to switch to the second mode between the first mode of maintaining the state of charge of the battery, i.e., the SOC, and the second mode of depleting the SOC at the target speed limit, determines to switch to the second mode at the time point when the actual APS value and the second APS value become different; and A transmission control unit that determines the transmission gear by applying the determined virtual vehicle speed and the determined virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode according to whether or not to switch to the second mode.

11. The hybrid vehicle according to claim 10, wherein The virtual APS corrector calculates the constant-speed driving load at the target speed limit and obtains the first APS value by applying the constant-speed driving load to the torque-APS conversion map.

12. The hybrid vehicle according to claim 10, wherein The mode corrector determines the standard power for conversion between the first mode and the second mode based on the SOC, determines the constant-speed driving load at the target speed limit, and determines that the hybrid vehicle is to be converted to the second mode when the standard power is greater than the constant-speed driving load.

13. The hybrid vehicle according to claim 10, wherein The first mode includes a charge-sustaining mode, i.e., a CS mode; and The second mode includes a discharge mode, i.e., a CD mode.

14. A hybrid vehicle, comprising: A hybrid control unit, comprising: A vehicle speed corrector that corrects the virtual vehicle speed to the target speed limit when the vehicle speed is higher than the target speed limit; A virtual accelerator position sensor corrector, i.e., a virtual APS corrector, that corrects the virtual APS value to the first APS value when the first APS value corresponding to the constant-speed driving load at the target speed limit is less than the second APS value following the target speed limit; and A mode corrector that determines to switch to the second mode at a time point when the actual APS value and the second APS value become different when it is desired to switch to the second mode in a first mode of maintaining the state of charge (SOC) of the battery at the target speed limit and a second mode of depleting the SOC; and A transmission control unit that determines a transmission gear by applying the virtual vehicle speed and the virtual APS value to one of a first transmission mode corresponding to the first mode and a second transmission mode corresponding to the second mode according to whether the switch to the second mode is made.

15. The hybrid vehicle according to claim 14, wherein the virtual APS corrector calculates the constant-speed driving load at the target speed limit and obtains the first APS value by applying the constant-speed driving load to a torque-APS conversion map.

16. The hybrid vehicle according to claim 14, wherein the mode corrector determines the standard power for switching between the first mode and the second mode based on the SOC, determines the constant-speed driving load at the target speed limit, and determines that the hybrid vehicle is to switch to the second mode when the standard power is greater than the constant-speed driving load.

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