Claims:
We Claim:
1. A control method for gradient detection in a hybrid vehicle, wherein vehicle rpm of said hybrid vehicle is equal to zero and wherein the hybrid vehicle comprises 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:
determining position of a side stand and a centre stand and a state of wheel brake in the hybrid vehicle by means of inputs received from a side stand switch (SS), a centre stand switch (CS) and a wheel brake sensor (WB) respectively;
if neither the side stand switch (SS) nor the centre stand switch (CS) nor the wheel brake sensor (WB) is turned on, then determining an occupancy of a vehicle seat by means of an input received from a seat occupancy sensor (SO);
if neither the side stand switch (SS) nor the centre stand switch (CS) nor the wheel brake sensor (WB) is turned on and the vehicle seat is not occupied by a rider, then disabling a vehicle drive mode or if neither the side stand switch (SS) nor the centre stand switch (CS) nor the wheel brake sensor (WB) is turned on, and the vehicle seat is occupied by a rider, then determining a gradient condition at which the hybrid vehicle is operating, as an up gradient or a down gradient, by means of input received from an inclination sensor;
on detection of an up gradient, comparing a measured value of throttle position (TPS) with a predetermined value of throttle position (TPSrefl) stored in the controller and if the measured value of TPS is greater than the predetermined value of the throttle position (TPSrefl) stored in the controller, then switching a user selected non hybrid power mode to a hybrid power mode, simultaneously calculating a reference value of current (Iref) based on a detected value of up gradient and a state of charge (SOC) of battery and supplying the reference value of current to the traction motor;
on detection of an up gradient, comparing a measured value of throttle position (TPS) with a predetermined value of throttle position (TPSrefl) stored in the controller and if the measured value of TPS is not greater than the predetermined value of the throttle position (TPSrefl) stored in the controller, then calculating a reference value of current (Iref) based on a detected value of up gradient and supplying the reference value of current (Iref) to the traction motor to prevent the vehicle from rolling backwards on the up gradient;
on detection of a down gradient, comparing a measured value of throttle position (TPS) with a predetermined value of throttle position (TPSrefl) stored in the controller and if the measured value of throttle position (TPS) is greater than the predetermined value of throttle position (TPSrefl) stored in the controller, then calculating a reference value of current (Iref) based on a detected value of down gradient and state of charge (SOC) of the battery and supplying the reference value of current (Iref) to the battery, in order to charge the battery; and
on detection of a down gradient, comparing a measured value of throttle position (TPS) with a predetermined value of throttle position (TPSrefl) stored in the controller and if the measured value of TPS is not greater than TPSrefl, then calculating a reference value of current (Iref) based on a detected value of down gradient and supplying the reference value of current (Iref) to the traction motor to prevent the vehicle from rolling forwards on the down gradient.
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;
determines vehicle rpm, gradient condition, throttle position of the vehicle, position of a side stand and centre stand, state of wheel brake, seat occupancy and state of charge of the battery, based on inputs received from a position sensor, an inclination sensor, a throttle position sensor, a side stand switch and a centre stand switch, a wheel brake sensor, a seat occupancy sensor and a battery respectively;
compares a determined value of vehicle rpm and a determined value of throttle position with a predetermined value of vehicle rpm and a predetermined value of throttle position respectively, when vehicle rpm is greater than zero, in order to determine whether a vehicle drive mode should be switched to a hybrid power mode and to determine an amount of reference current to be pumped to the traction motor on a gradient; determines an amount of reference current to be pumped to the battery based on a determined value of gradient and a state of charge (SOC) of the battery; and
prevents vehicle roll back or roll forward under gradient conditions, and when hybrid vehicle rpm is zero, by receiving inputs from the inclination sensor, the side stand switch, the centre stand switch, the wheel brake sensor and the seat occupancy sensor and calculating a reference value of current (Iref) to be pumped to the traction motor.
, Description:TECHNICAL FIELD
[0001] The present invention relates to a control system for hybrid vehicle to negotiate gradient condition, more particularly to a control system for a scooter type hybrid vehicle.
BACKGROUND
[0002] 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.
[0003] In patent document JP-A-8-126116, there is disclosed a parallel type hybrid vehicle in which the charging of battery device corresponding to travelling route of the hybrid vehicle can be controlled. Charging of the battery is based on the up gradient or the down gradient information. This parallel-type hybrid vehicle includes a navigation processing part which is connected to a GPS receiver, wherein up gradient information in the travelling route of the vehicle is extracted by the navigation processing part. However, since the hybrid vehicle disclosed in this patent document detects gradient by making use of GPS radio waves from an artificial satellite, it is difficult to properly perform cannot be received, such as a tunnel.
[0004] In another known art, a parallel-type hybrid vehicle is disclosed, wherein an electronic controller is provided in the hybrid vehicle to detect the gradient or slope. The controller is programmed to sense vehicle rpm and throttle position (TPS). Further, the controller compares the measured value of vehicle rpm for a corresponding measured value of throttle position with a predetermined rpm value for a corresponding predetermined value of throttle position, wherein the predetermined rpm value and the predetermined value of throttle position for several predetermined time intervals are stored in the controller and based on which the vehicle drive mode is changed automatically. However, in a vehicle using this system, if the vehicle is in stand still condition and TPS is higher than the predetermined value, automatically vehicle drive mode will be changed to hybrid power mode by the controller irrespective of the real gradient condition (can be up gradient or down gradient, flat road) condition. Also, in such conditions, the amount df current pumped to the traction motor will be more, thereby resulting in loss of power and low mileage of the hybrid vehicle.
[0005] Further, if the vehicle is running in economy mode and encounters an up gradient, a certain time delay is involved in the detection of the up gradient as the controller compares vehicle RPM and throttle position for predetermined time intervals. Therefore, this results in unnecessary time delay in changing vehicle drive mode to the hybrid power mode, thereby resulting in energy losses, as an additional amount of current is required to be supplied to the motor, till the time the up gradient is detected.
[0006] Therefore, the present invention tries to overcome the problem of the prior art and provides a vehicle with a controller which can detect gradient conditions and accordingly change the drive mode of the vehicle with minimal power losses and without undue time delay.

BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The detailed description described with reference to the accompanying figures. The same numbers have been used throughout the drawings to reference like features and components.
[0008] Fig.1 illustrates a hybrid vehicle according to the present invention.
[0009] Fig.2 shows a flowchart outlining the method of functioning of a controller for gradient detection according to the present invention in vehicle running condition.
[00010] Fig.3 shows a flowchart outlining the method of functioning of the controller for gradient detection according to the present invention in vehicle standstill condition.
DETAILED DESCRIPTION
[00011] Accordingly, it is an object of the present invention to provide a controller for a hybrid vehicle, which can detect a gradient or a slope at which the vehicle is travelling and thereafter automatically alter the vehicle drive mode on detection of a gradient, with minimal power losses and without undue time delay. The present invention involves the calculation of exact value of reference current required to power a traction motor when the vehicle drive mode is switched, wherein the calculation of reference current is based on the inclination at which the hybrid vehicle is travelling and on the state of charge (SOC) of the battery. It is also important to prevent vehicle roll back or roll forward, when the hybrid vehicle is in a standstill condition on a gradient. Therefore, it is another object of the invention to provide a controller which aids in preventing vehicle roll back or roll forward under gradient conditions.
[00012] In the present invention the controller receives inputs from an inclination sensor to detect an up gradient or a down gradient. This input along with vehicle rpm input from a motor position sensor and throttle position input form a throttle position sensor is used to change the drive mode of the vehicle under gradient conditions. Simultaneously, the controller also calculates the exact reference value of current required for charging a battery on a down gradient based on input from the inclination sensor and the state of charge (SOC) of battery and calculates the exact reference value of current required for motoring the traction motor on an up gradient based on inputs from the inclination sensor and information on state of charge (SOC) of battery. Input from the inclination sensor along with inputs from a side stand switch, a centre stand switch, a wheel brake sensor and a seat occupancy sensor is used to calculate the reference value of current to be pumped to a traction motor to avoid vehicle roll back on an up gradient and vehicle roll forward on a down gradient.
[00013] The nature and further characteristic features of the present invention will be made clearer from the following descriptions made with reference to the accompanying drawings.
[00014] 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 11 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 67. 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.
[00015] 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 in the rear portion of side tube(s) 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.
[00016] 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.
[00017] Figure 2 and Figure 3 represent an illustrative flowchart outlining the method of operation of the controller 7 in the hybrid vehicle 10. The controller 7 is programmed to monitor gradient condition, position of a side stand and a centre stand, throttle position, vehicle rpm, state of brake, vehicle seat occupancy by the rider and SOC continuously. Once the operator switches on the ignition of the vehicle, the controller 7 reads throttle position of the vehicle and vehicle rpm and acts in the manner described below.
[00018] (A) In a vehicle running condition, that is, when the measured value of vehicle rpm is greater than zero, the controller 7 checks for gradient condition using an inclination sensor, wherein the inclination sensor is mounted to an instrument cluster of the hybrid vehicle. If no gradient condition is detected, the controller 7 does not change the vehicle drive mode and the vehicle continues to run in the user selected drive mode. When an up gradient is detected, the controller 7 checks for the level of up gradient and if the detected value of up gradient is greater than a predetermined value of gradient (Gradient_ref), stored in the controller, then the controller 7 changes the vehicle drive mode to hybrid power mode and simultaneously, the controller 7 also calculates a current reference value (Iref) based on the gradient level detected and the state of charge (SOC) of the battery 63 and the same is supplied to the traction motor 19.
[00019] However, if the level of up gradient detected is not greater than Gradient_ref, then the controller 7 compares a measured value of throttle position (TPS) of the vehicle with a predetermined value of throttle position (TPSref2) stored in the controller and a measured value of vehicle rpm with a predetermined value of vehicle rpm (RPMref2) stored in the controller and if the measured value of TPS is greater than the predetermined value of throttle position (TPSref2) and the measured value of vehicle rpm is less than the predetermined value RPM (RPMref2), then the controller 7 changes the vehicle drive mode to hybrid power mode. Moreover, the drive mode of the vehicle is changed under the above -mentioned conditions only if the previously selected drive mode by the user was a non-hybrid power mode. If the previous user selected mode was the hybrid power mode, then the vehicle would continue to operate in the same mode. Along with changing the drive mode of the vehicle as per the above-mentioned conditions, the controller 7 simultaneously calculates a current reference value (Iref) based on the gradient level and state of charge (SOC) of the battery 63 and this Iref value of current is supplied to the traction motor 19. In the above-mentioned conditions, the measured value of TPS ranges from seventy per cent to eighty-five per cent and the measured value of vehicle rpm ranges from 25kmph to 35kmph. However, if the above-mentioned conditions of TPS and vehicle rpm are not satisfied, the controller 7 does not change the vehicle drive mode and the vehicle continues to run in the user selected drive mode. When the controller 7 detects a down gradient, it calculates a charging current reference (Iref) based on SOC and level of down gradient and accordingly charge the battery 63.
[00020] (B) When the vehicle ignition is "ON" and if measured value of vehicle rpm is equal to zero, that is, when the vehicle is in a standstill condition, then the controller 7 checks for position of side stand, position of centre stand and state of brake by means of a side stand switch (SS), a centre stand switch (CS) and a wheel brake sensor (WB) respectively. In a condition where neither SS nor CS nor WB is ON, then the controller 7 checks for occupancy of the vehicle seat by means of a seat occupancy sensor (SO), and if the seat is not occupied by the rider, then the controller 7 disables the vehicle drive mode. Thus, the vehicle is prevented from moving when a rider has not occupied the seat. However, if neither SS nor CS nor WB is ON and the controller 7 detects the seat to be occupied, then it checks for the gradient condition with the help of the inclination sensor. Further, the controller determines whether the gradient is an up gradient or a down gradient. If no gradient condition is detected, the controller maintains the drive mode of the vehicle as the user selected drive mode. However, if an up gradient is detected, the controller 7 checks for TPS value of the vehicle and further, if the measured value of TPS is greater than a predetermined value of the throttle position (TPSrefl) stored in the controller, then the controller 7 changes the vehicle drive mode to hybrid power mode when the rider throttles the vehicle and also calculates the reference current Iref based on the level of up gradient and the SOC. This Iref amount of current is pumped to the traction motor in order to aid the vehicle to cross the up gradient.
[00021] However, if an up gradient is detected but the measured value of TPS is not greater than TPSrefl, then the controller based on the level of up gradient detected, is involved only in calculating Iref amount of current to be pumped to the traction motor to prevent the vehicle from rolling backwards on the up gradient.
[00022] On the other hand, if a down gradient is detected, the controller 7 again compares a measured value of TPS with a predetermined value of TPS, TPSrefl and if the measured value of TPS is greater than TPSrefl, then the controller 7 calculates the amount of reference current (Iref) based on the level of down gradient and SOC in order to charge the battery. However, if on a down gradient, the measured value of TPS is not greater than the predetermined value of TPS (TPSrefl), then the controller 7 calculates a reference value of current (Iref) based on the level of gradient detected and the same is utilized in order to prevent the vehicle from rolling forward. In a condition where either SS or CS or WB is ON, the controller 7 does not perform any of the sequence of events mentioned above.
[00023] The embodiment of the controller for gradient detection, as described above helps in minimizing power losses as it aids in the calculation of the exact amount of current required to power the traction motor under up gradient conditions, based on the level of up gradient at which the hybrid vehicle is travelling and also based on the SOC of the battery, rather than providing the same amount of current to the traction motor, irrespective of the level of up gradient condition. Thus, the use of controller helps in improving the mileage of the hybrid vehicle. Unnecessary time delay is avoided in changing the drive mode to hybrid power mode on a gradient, as an inclination sensor is used to determine the slope condition. Further, said control system ensures safety, as vehicle drive mode is enabled only after the vehicle seat is occupied by the rider.
[00024] 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 and detail may be made therein without departing from the scope of the invention as defined in the appended claims.