CONTROL METHOD FOR HYBRID VEHICLE

FIELD OF THE INVENTION
The present invention relates to a hybrid vehicle which is configured to detect a slope or a gradient.

DESCRIPTION OF PRIOR ART

Two kinds of hybrid vehicles known in the prior art include the parallel type hybrid vehicle and the series type hybrid vehicle. The parallel-type hybrid vehicle is configured such that either the engine or the traction motor selectively powers the vehicle, whereas, the series-type hybrid vehicle is configured such that only the traction motor powers the vehicle. In this arrangement, the engine does not directly power the vehicle but powers the traction motor which in turn drives the vehicle. However, in both the types of hybrid vehicles, it is difficult to drive the vehicle on a gradient or a slope using a single source as propellant because the vehicle experiences increased load. Therefore, when the hybrid vehicle encounters a slope or gradient it becomes essential to switch the drive mode from a single source power mode to a dual source power mode or a hybrid power mode. In such conditions, it becomes necessary to firstly detect the gradient or the slope at which the hybrid vehicle is travelling and thereafter alter the drive mode of the vehicle to a hybrid power mode.

In patent document JP-A-8-126116, there is disclosed a parallel type hybrid vehicle which can control the charging of a battery device relative to a travelling route of the hybrid vehicle. Specifically, the charging of the battery is based on whether the hybrid vehicle is ascending a slope or descending a slope. This parallel-type hybrid vehicle includes a navigation processing part which is connected to a GPS receiver, wherein slope ascending or descending information in the travelling route of the vehicle is extracted by the navigation processing part. However, since gradient detection in this hybrid vehicle involves the use of GPS radio waves from an artificial satellite, it is difficult to detect a gradient in a place where GPS radio waves cannot be received, such as a tunnel.

In another known art, a series-type hybrid vehicle is disclosed, wherein the hybrid vehicle includes a control unit and an inclination sensor. While the control unit controls the output of a generator and the charging of a battery, the inclination sensor detects an inclination in the running direction of the vehicle with respect to a horizontal surface. The control unit controls the output of the generator and the charging of the battery based on the information received on a slope ascending state or a slope descending state of the vehicle from the inclination sensor. However, as this arrangement involves the use of an additional inclination sensor along with the control unit to determine a slope or gradient, it makes the hybrid vehicle more costly.

Therefore, it is an object of the invention to provide a gradient detection system in a hybrid vehicle capable of detecting a gradient at any point during vehicle running condition.

It is another object of the invention to provide a gradient detection system in a hybrid vehicle capable of taking increased load on a gradient, while maintaining fuel economy of the vehicle.

It is yet another object of the invention to provide an inexpensive gradient detection system in a hybrid vehicle without involving the use of an inclination sensor or a GPS receiver for gradient detection.

SUMMARY OF THE INVENTION

The present subject matter described herein relates to a hybrid vehicle with a controller which can detect a gradient or a slope at which the vehicle is travelling and thereafter automatically alter the vehicle drive mode to a hybrid power mode. In order to achieve this, the controller is programmed to process information relating to vehicle rpm and throttle position, which in turn is provided from a position sensor and a throttle position sensor respectively. Further, the controller compares a measured value of vehicle rpm for a corresponding measured value of throttle position of the vehicle with a predetermined rpm value for a corresponding predetermined value of throttle position, wherein the predetermined rpm value and the corresponding predetermined value of throttle position are stored in the controller. Based on the processing of the above mentioned information, the controller switches the vehicle drive mode to the hybrid power mode and thereby increases the load carrying capacity of the hybrid vehicle on a slope or a gradient and ensures a comfortable ride. Also, when the hybrid vehicle crosses the gradient, the controller switches from the hybrid power mode to a previous user selected drive mode. Thus, gradient detection in the hybrid vehicle is performed without involving the use of a separate device or sensor specifically mounted for gradient detection.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a hybrid vehicle according to the present invention. Figure 2 shows a flowchart outlining the method of functioning of a controller for gradient detection according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a hybrid vehicle and a control method for said hybrid vehicle in accordance to the present invention will be described hereunder with reference to the accompanying drawings. Various features of the hybrid vehicle and the control method for the hybrid vehicle in accordance to the present invention will become discernible from the following description set out hereunder. It is further to be noted that terms "upper", "lower", "right", "left", "rearward", "forward", "downward" and like terms are used herein based on the illustrated state or in a standing state of a motorcycle with a driver riding thereon. Furthermore, a longitudinal axi refers to a front to rear axis relative to the vehicle, while a lateral axis refers to a side to side, or left to right axis relative to the vehicle.

Figure 1 illustrates a hybrid vehicle 10 in accordance to the present invention. The hybrid vehicle 10 has a main tube 11, a head pipe 12 connected to the upper most portion of the main tube and positioned anterior to the main tube 11 and a down tube 67 extending rearwardly and horizontally in the vehicle length direction from the lower most portion of the main tube 11. Pair of side tubes 15 are arranged side by side extending obliquely upwards in a rear direction from a connecting portion of the down tube. In an upper portion of the head pipe 12, a handlebar 13 is rotatably integrally connected to the steering shaft (not shown). To a lower end of the steering shaft a front fork 23 is attached and a front wheel 91 is journaled to a lower end of the front fork 23. The front wheel 91 is rotated in a certain range by steering the handlebar 13. A touch screen LCD unit 3 is mounted on the handle bar 13, to display the various operating modes, power flow pattern and warning signals. Rear view mirrors 27 are mounted on the right and left sides of the handle bar 13.

Furthermore, an engine 14 is arranged in a space formed at a substantially central lower portion between the side tubes 15. Further, the engine 14 is supported by a swing arm 9. The swing arm 9 is attached to the lower portion of the downtube 67 by means of a toggle link 5. The other end of the swing arm 9 holds a rear wheel 101. The rear wheel 101 and the swing arm 9 are connected to the pair of side tubes 15 by means of a pair of shock absorbers 25 provided on either side of the vehicle.

A traction motor 19 is mounted on the hub of the rear wheel 101. A battery 63 is mounted to the rear of the left side tube 15 and supplies power to the traction motor 19. A controller 7 is placed posteriorly and to the right hand side of the battery 63.

Said hybrid vehicle 10 is designed to be propelled either by the engine 14 alone or by the traction motor 19 alone or by both engine 14 and traction motor 19 simultaneously. At zero vehicle speed, a rider can select any of the following four operating drive modes with the help of a mode switch. The four operating drive modes of the hybrid vehicle 10 are: (a) a sole engine mode where engine 14 alone powers the vehicle (b) a sole motor mode where the traction motor 19 alone powers the vehicle (c) a hybrid power mode wherein the engine 14 and the traction motor 19 together power the hybrid vehicle 10 (d) a hybrid economy mode wherein only the engine 14 or only the traction motor 19 or both power the hybrid vehicle depending on the vehicle operating conditions.
The hybrid vehicle 10 is configured to detect a gradient or a slope at which it is travelling without involving the use of an inclination sensor or a GPS receiver to detect the gradient. The hybrid vehicle 10 is provided with a controller 7 that helps in detecting the gradient or the slope at which the vehicle 10 is travelling and automatically switches the drive mode to the hybrid power mode on detection of a gradient. The controller 7 determines the gradient at which the vehicle 10 is travelling by processing information relating to vehicle rpm and throttle position. Information on vehicle rpm and throttle position is provided to the controller from a position sensor mounted inside the traction motor, which is in turn mounted on the hub of the rear wheel and a throttle position sensor respectively. Based on the processing of the above mentioned information, the controller 7 switches the drive mode to the hybrid power mode when the hybrid vehicle 10 is encounters a slope or gradient.

Figure 2 represents an illustrative flowchart outlining the method of operation of the controller 7. The controller 7 in the hybrid vehicle 10 is programmed to monitor vehicle rpm and throttle position continuously in order to detect a slope or gradient in running direction of the vehicle with respect to a horizontal surface. The controller 7 receives information on vehicle rpm and throttle position from a position sensor and a throttle position sensor respectively and measures the exact value of the vehicle rpm and throttle position. The controller 7 detects the gradient by comparing the measured value of vehicle rpm for a corresponding measured value of throttle position with a predetermined threshold value of vehicle rpm for a corresponding predetermined value of throttle position which is programmed into it and switches the drive mode accordingly. .

The method of functioning of the controller 7 is outlined below. The controller 7 firstly checks whether the prevailing drive mode of the vehicle is the hybrid power mode or a non hybrid power mode, wherein the non hybrid power mode constitutes any of the three above mentioned operating modes other than the hybrid power mode. If the prevailing drive mode of the vehicle is the hybrid power mode, then the controller 7 checks whether the hybrid power mode has been activated by the rider (user selected hybrid power mode) or whether the hybrid power mode has been automatically activated because of a gradient, wherein the hybrid power mode operating due to automatic activation may be referred to as non user selected hybrid power mode. If the hybrid power mode was a user selected mode then the controller performs no further processing of information and the vehicle continues to run in the same mode even after crossing a gradient. However, if the operation of the hybrid power mode was automatic (non user selected hybrid power mode) due to a gradient then the controller 7 exits from the hybrid power mode and switches to the previous user selected mode when the value of throttle position falls to less than 60% and the vehicle rpm is greater than 30kmph for z seconds. In other words, the controller 7 switches to the previous user selected mode from the hybrid power mode, as soon as the hybrid vehicle 10 crosses the gradient.

If the prevailing drive mode of the hybrid vehicle 10 is a non hybrid power mode i.e. a mode other than the hybrid power mode, then based on the information processed for vehicle rpm value and the throttle position value, the controller 7 switches to the hybrid power mode. For instance, when the throttle position value received by the controller 7 is more than 85%, the controller 7 checks for any of the following conditions: (a) whether measured value of vehicle rpm is less than 1kmph for a time interval of 'x' seconds, (b) whether measured value of vehicle rpm is less than 20 kmph for 'y' seconds, wherein 'x' is less than y, (c) whether change in vehicle rpm is negative. The controller 7 checks for the above mentioned conditions sequentially when the throttle position value received by it is more than 85%. In other words, if the first condition is not satisfied, the controller 7 checks for the second condition and so on. When any one of the above mentioned conditions is satisfied for a throttle position value greater than 85%, the controller 7 switches the prevailing non hybrid power mode to the hybrid power mode. Once the vehicle crosses the gradient and the throttle position value reduces to less than 60% and the vehicle rpm is greater than 30kmph for z seconds, wherein z is equal to y and greater than x, the controller 7 automatically switches the hybrid power mode to the previous user selected non hybrid power mode. In other words, the drive mode is switched to the user selected non hybrid power mode in which the hybrid vehicle 10 was running prior to detection of the gradient.

However, when none of the above mentioned conditions is satisfied, the controller 7 does not change the drive mode of the hybrid vehicle 10 and the vehicle 10 continues to run in the prevailing non hybrid power mode.

Thus, the hybrid vehicle 10 is configured to detect a slope or a gradient without involving the use of additional sensors like an inclination sensor, or a GPS receiver. Moreover, since the controller automatically changes the drive mode to the hybrid power mode on encountering a slope, the vehicle does not stall on the slope or in case it stalls on the middle of a slope, it starts running again. Therefore, increased load can be easily carried by the hybrid vehicle 10 even on a gradient or slope. Also, since the controller switches from the hybrid power mode as soon as the gradient is crossed, fuel economy of the vehicle is ensured. Thus, the controller 7 not only ensures riding comfort on a gradient but also helps in maintaining fuel economy of the vehicle after crossing the gradient.

While the present invention has been shown and described with reference to the foregoing preferred embodiment, it will be apparent to those skilled in the art that changes in form, connection, and detail may be made therein without departing from the spirit and scope of the invention as defined in the appended claims:

WE CLAIM:

1. A control method for gradient detection in a hybrid vehicle, the hybrid vehicle comprising an internal combustion engine, a starter motor coupled to the internal combustion engine, a battery, a traction motor, a controller and a plurality of drive modes including an only engine mode, an only motor mode, a hybrid economy mode and a hybrid power mode; the control method comprising the steps of:
identifying a prevailing drive mode of the hybrid vehicle as the hybrid power mode or as a non hybrid power mode and if it is the hybrid power mode, then as a user selected hybrid power mode or as a non user selected hybrid power mode; measuring a vehicle rpm value from a position sensor; measuring a vehicle throttle position value from a throttle position sensor;

comparing a measured value of vehicle rpm for a corresponding measured value of throttle position continuously with a predetermined threshold value of vehicle rpm for a corresponding predetermined threshold value of throttle position stored in the controller; and if the prevailing drive mode identified is the non hybrid power mode then switching the prevailing non hybrid power mode to the hybrid

power mode when the measured value of vehicle rpm for a corresponding measured value of throttle position is less than the predetermined threshold value of vehicle rpm for the corresponding predetermined threshold value of throttle position stored in the controller and thereafter switching the hybrid power mode to a user selected previous non hybrid power mode when the measured value of vehicle rpm for a corresponding measured value of throttle position exceeds the predetermined threshold value of vehicle rpm for the corresponding predetermined threshold value of throttle position stored in the controller;

if the prevailing drive mode identified is the non user selected hybrid power mode then switching the prevailing non user selected hybrid power mode to the user selected previous non hybrid power mode when the measured value of vehicle rpm for a corresponding measured value of throttle position exceeds the predetermined threshold value of vehicle rpm for the corresponding predetermined threshold value of throttle position stored in the controller.

2. A controller mounted to a hybrid vehicle, the hybrid vehicle comprising an internal combustion engine, a starter motor coupled to the internal combustion engine, a battery, a traction motor, a controller and a plurality of drive modes including an only engine mode, an only motor mode, a hybrid economy mode and a hybrid power mode, wherein the controller;

identifies a prevailing drive mode of the hybrid vehicle as the hybrid power mode or as a non hybrid power mode and if it is the hybrid power mode then as a user selected hybrid power mode or as a non user selected hybrid power mode measures a vehicle r.p.m. value from a position sensor; measures vehicle throttle position value from a throttle position sensor;

compares a measured value of vehicle rpm for a corresponding measured value of throttle position continuously with a predetermined threshold value of vehicle rpm for a corresponding predetermined threshold value of throttle position stored in the controller; and

if the prevailing drive mode identified is the non hybrid power mode then switches the prevailing non hybrid power mode to the hybrid power mode when the measured value of vehicle rpm for a corresponding measured value of throttle position is less than the predetermined threshold value of vehicle rpm for the corresponding predetermined threshold value of throttle position stored in the controller and thereafter switches the hybrid power mode to a user selected previous non hybrid power mode when the measured value of vehicle rpm for a corresponding measured value of throttle position exceeds the predetermined threshold value of vehicle rpm for the corresponding predetermined threshold value of throttle position stored in the controller;

if the mode identified is the non user selected hybrid power mode then switches the prevailing non user selected hybrid power mode to the user selected previous non hybrid power mode when the measured value of vehicle rpm for a corresponding measured value of throttle position exceeds the predetermined threshold value of vehicle rpm for the corresponding predetermined threshold value of throttle position stored in the controller.

3. The controller as claimed in claim 2 for the hybrid vehicle, wherein the position sensor is mounted inside the traction motor, which is in turn mounted on a hub of a rear wheel of the hybrid vehicle.