Claims:We claim:
1. A control unit (110) for Automatic Change Over (ACO) (120) of engine operation between a primary fuel and a secondary fuel in a bi-fuel vehicle, said primary fuel and said secondary fuel are selected from at least one of a gaseous medium and a liquid medium, said control unit (110) configured to:
determine occurrence of a condition comprising engine temperature, to switch from said primary fuel to said secondary fuel, characterized in that,
switch engine operation between said primary fuel and said secondary fuel after detection of any one of a first set of conditions and a second set of conditions, said engine operation is switched from said primary fuel to said secondary fuel based on fulfillment of said first set of conditions and said engine operation is switched from secondary fuel to said primary fuel based on fulfillment of said second set of conditions.

2. The control unit (110) as claimed in claim 1, wherein said first set of condition comprises at least one or all selected from a group comprising engine speed is zero or at idle speed, detection of a new drive cycle of said vehicle, said ACO (120) is not completed from previous drive cycle, said vehicle is operated using said primary fuel and said vehicle is not enabled with ACO (120).

3. The control unit (110) as claimed in claim 1, wherein said second set of conditions is at least one selected from a group comprising a soak condition and a reset condition, wherein said soak condition comprises checking difference between said engine temperature and an ambient temperature is below a threshold difference, and said ambient temperature less than a threshold temperature.

4. The control unit (110) as claimed in claim 3, wherein said reset condition disables said ACO (120) and switches said vehicle back to primary fuel, said reset condition is any one selected from a group comprising
an error in any one of said vehicle, hardware parts and said ACO (120),
a number of failed starts in secondary fuel exceeds a threshold count,
said secondary fuel consumption is more than an upper threshold quantity and a fuel cut-off request is received,
said secondary fuel consumption is more than a lower threshold quantity with detection of at least one of an ignition Key ON state and a new drive cycle,
a low fuel level of said secondary fuel is detected, and
a duration of failed crank attempts is greater than said threshold duration.

5. The control unit (110) as claimed in claim 1, wherein said ACO (120) is performed to keep said secondary fuel based limp home fuel system in an operating state.

6. A method for Automatic Change Over (ACO) (120) of engine operation between a primary fuel and a secondary fuel in a bi-fuel vehicle, said primary fuel and said secondary fuel are selected from any one of a gaseous medium and a liquid medium, said method comprises the steps of:
determining occurrence of a condition, comprising engine temperature, for switching from said primary fuel to said secondary fuel, , characterized by,
switching engine operation between said primary fuel and said secondary fuel after detecting any one of a first set of conditions and a second set of conditions, wherein switching from said primary fuel to said secondary fuel is based on fulfillment of said first set of conditions and switching from said secondary fuel to said primary fuel is based on fulfillment of said secondary set of conditions.

7. The method as claimed in claim 6, wherein said first set of condition comprises at least one or all conditions selected from a group comprising engine speed is zero or at idle speed, detecting a new drive cycle of said vehicle, said ACO (120) is not completed from previous drive cycle, said vehicle is running in said primary fuel and said vehicle is not enabled with ACO (120).

8. The method as claimed in claim 6, wherein said second set of conditions is at least one selected from a group comprising a soak condition and reset condition, wherein said soak condition comprises checking difference between said engine temperature and an ambient temperature is below a threshold difference, and said ambient temperature less than a threshold temperature.

9. The method as claimed in claim 8, wherein said reset condition disables said ACO (120) and switches said vehicle back to said primary fuel, said reset condition is any one selected from a group comprising
an error in any one of said vehicle, hardware parts and said ACO (120),
a number of failed starts in secondary fuel exceeds a threshold count,
said secondary fuel consumption is more than an upper threshold quantity together with receiving a fuel cut-off request,
said secondary fuel consumption is more than a lower threshold quantity together with detecting any one of an ignition Key ON state and a new drive cycle,
a low fuel level of said secondary fuel is detected, and
a duration of failed crank attempts is greater than said threshold duration.

10. The method as claimed in claim 1, wherein said ACO (120) is performed to keep said secondary fuel based limp home fuel system in an operating state.
, Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:

Field of the invention:
[0001] The present invention relates to a control unit and method for automatic changeover of engine operation in bi-fuel vehicle.

Background of the invention:
[0002] When a vehicle has primary gaseous fuel such as a Compressed Natural Gas (CNG) or Liquified Petroleum Gas (LPG) and a Limp home fuel as gasoline (liquid fuel), the limp home fuel system may not be used for very long time. This can happen when the primary fuel availability in the user region is surplus. This causes the limp home fuel system to become nonfunctional or improper functioning due to injector stuck or fuel pump failure or fuel line clogging or other reasons due to being inoperative. When the user/driver needs the limp fuel system to be operated after long time, the Engine Management System (EMS) fails to support due to malfunction of the corresponding components or parts.

[0003] A patent literature CN110630387 discloses a dual-fuel engine switching method, device, and system. The method includes: if the switch is in the set state, detecting whether the starting temperature of the engine is greater than the first preset temperature when the switch is in the set state; If the starting temperature is greater than the first preset temperature, the engine is controlled to operate in a first fuel mode; if the switch is in a reset state, the engine is controlled to switch from the first fuel mode to the second fuel mode. The free switching of the engine fuel mode is realized, which can not only meet the switching needs of vehicle users, but also ensure the normal operation of the engine, thereby improving the safety and reliability of vehicle driving.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0005] Fig. 1 illustrates a block diagram of a control unit for Automatic Change Over (ACO) of engine operation, according to an embodiment of the present invention, and
[0006] Fig. 2 illustrates a method for ACO of the engine operation, according to the present invention.

Detailed description of the embodiments:
[0007] Fig. 1 illustrates a block diagram of a control unit for Automatic Change Over (ACO) of engine operation, according to an embodiment of the present invention. The ACO 120 of the engine operation is done between a primary fuel (or a primary fuel injection system 116) and a secondary fuel (or secondary fuel injection system 118) in a bi-fuel vehicle. The primary fuel and the secondary fuel are selected from at least one of a gaseous medium and a liquid medium. The control unit 110 configured to determine occurrence of a condition comprising an engine temperature, to switch from the primary fuel to the secondary fuel, characterized in that, the control unit 110 switches the engine operation between the primary fuel and the secondary fuel after detection of any one of a first set of conditions and a second set of conditions. The engine operation is switched from the primary fuel to the secondary fuel based on fulfillment of the first set of conditions, and the engine operation is switched from secondary fuel to the primary fuel based on the fulfillment of the second set of conditions. In other words, the control unit 110 switches between the primary fuel injection system 116 and the secondary fuel injection system 118 based on fulfillment of respective set of conditions. The secondary fuel injection system 118 is also referred to as limp home fuel system.

[0008] In an embodiment, the control unit 110 checks both the first set of condition and the second set of condition irrespective of the present state of the ACO 120. Alternatively, the control unit 110 checks for the first set of condition if the secondary fuel is being used, and checks the second set of condition if the primary fuel is being used. Further, the control unit 110 checks for one or combinations of additional conditions in the first set of conditions and the second set of conditions.

[0009] According to the present invention, the ACO 120 is a functionality which enables toggling between primary fuel and the secondary fuel (ON/OFF state) based on any one of the first set of conditions and the second set of conditions. Alternatively, the ACO 120 is a switch to effect the changeover between the primary fuel and the secondary fuel. The control unit 110 when enables or activates the ACO 120, the engine is operated in secondary fuel and wen disables or deactivates the ACO 120, the engine is operated in primary fuel.

[0010] The combination of primary fuel and secondary fuel is selected from a group comprising one gaseous medium and one liquid medium, one liquid medium and one gaseous medium, both liquid medium and both gaseous medium. Furthermore, the primary fuel is the main fuel with which the vehicle is operated, whereas the secondary fuel is for limp home or other emergency functionalities.

[0011] According to an embodiment of the present invention, the control unit 110 contains computing devices/units comprising components such as memory element 114 such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC), Digital-to-Analog Convertor (DAC), clocks, timers, counters and a processor (capable of implementing machine learning) connected with the each other and to other components through communication bus channels. The components mentioned are just for understanding and the control unit 110 may have more or less components as per requirement. The memory element 114 is pre-stored with logics or instructions or programs or applications or threshold values/limits/rate which is accessed by the processor as per the defined routines. The internal components of the control unit 110 are not explained for being state of the art, and the same must not be understood in a limiting manner. The control unit 110 may be capable of communicating through wired and wireless means such as but not limited to Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, Universal Serial Bus (USB) cable, micro-USB, and the like. In accordance to an embodiment, the control unit 110 is at least one selected from a group comprising an Engine Control Unit (ECU) of the EMS or other control unit 110 interfaced with the ECU.

[0012] In accordance to an embodiment of the present invention, the first set of condition is at least one or all conditions selected from a group comprising, engine temperature greater than a threshold engine temperature, engine speed is zero or at idle speed, detection of a new drive cycle of the vehicle, the ACO 120 is not completed from previous drive cycle, the vehicle is operated using the primary fuel and the vehicle is not enabled with ACO 120. In an embodiment, at least one condition in the first set of condition is checked. In an alternative, all the conditions in the first set of conditions are checked. Now, each of the first set of conditions are briefly explained. The engine speed is zero to ensure that if the switching of engine operation happens, then the switching must not be done when the vehicle is being driven to prevent any effect on drivability. Instead, the switching is done during the Key On of the vehicle when the ECU is just turned ON. Alternatively, the switching is done when the engine is idling or is at idle speed. The condition on engine temperature is to ensure that the engine is sufficiently hot before ACO 120. The new drive cycle of the vehicle is detected based on ignition key ON state position with a calibratable threshold time. The new drive cycle is to ensure that the opportunity of switching to secondary fuel must be after Key ON condition. The ACO 120 if activated or enabled in previous drive cycle is not complete, then the ACO 120 should be continued in the new drive cycle. The condition of ACO 120 not completed is dependent on consumption quantity of the secondary fuel having at least one limit. In an embodiment, the at least one limit comprises a lower limit and an upper limit. The condition of ACO 120 not completed is explained in subsequent paragraph. The engine of the vehicle must be operating on the primary fuel to enable switching to the secondary fuel. The condition of ACO 120 is not enabled or is in disabled state is to ensure that if ACO 120 is already enabled, then switching will cause the engine to be operated back in primary fuel.

[0013] In accordance to an embodiment of the present invention, the second set of conditions is at least one selected from a group comprising a soak condition and a reset condition. The soak condition comprises checking difference between the engine temperature and the ambient temperature is below a threshold difference, and the ambient temperature is less than a threshold temperature. The soak condition ensures that the engine temperature is same or almost same as the ambient temperature to ensure that the engine uses primary fuel always before ACO 120.

[0014] Similarly, the reset condition disables the ACO 120 and switches the vehicle back to the primary fuel. The reset condition is any one selected from a group comprising, an error in the vehicle, hardware parts and the ACO 120, a number of failed starts in secondary fuel exceeds a threshold count, the secondary fuel consumption is more than an upper threshold quantity with fuel cut-off request, the secondary fuel consumption is more than a lower threshold limit and a anyone of an ignition Key ON state and a new drive cycle is detected, a low fuel level of the secondary fuel is detected, and a duration of failed crank attempts is greater than the threshold duration. Now each of the condition of the secondary set of conditions is briefly explained. If an error is detected in the vehicle, in hardware parts or in the ACO 120, then the control unit 110 switches to the primary fuel or prevents switching from primary fuel as part of ACO 120 to ensure that no other abnormality is caused in the secondary fuel system to prevent any drivability issues. If the number of failed starts in secondary fuel exceeds the threshold count, the control unit 110 switches to primary fuel as continuance will cause the draining of a battery. If the fuel consumption of the secondary fuel is more than the upper threshold quantity and the fuel cut-off request is received, then the control unit 110 switches back to primary fuel as the desired engine operation has been performed. If the secondary fuel consumption is more than the lower limit and the ignition Key ON is detected or a new drive cycle is detected, then the control unit 110 switches back the primary fuel. The fuel-cut-off request is checked with the consumption quantity of the secondary fuel to ensure that the control unit 110 switches back the primary fuel in optimal time. Also, if the fuel consumption of the secondary fuel is more than the lower threshold quantity at Key ON, then the control unit 110 switches back to primary fuel as the desired engine operation has been performed. If the secondary fuel level is low in comparison to a threshold level, then the control unit 110 switches back to the primary fuel, as further consumption would lead to depletion of secondary fuel or may lead to damage to fuel pump or injector for a real limp home scenario. If the duration of failed crank attempts is greater than the threshold duration, then the control unit 110 switches back the primary fuel to ensure operability of the engine and to prevent the battery drain.

[0015] The values needed for the first set of conditions and the second set of conditions are obtained using the sensors such as engine speed sensor 102, engine temperature sensor 104, ambient temperature sensor 106, fuel level sensor 108, ignition key position sensor 112, pressure sensor and the like. Alternatively, the values are derived using the other sensor as known in the art. Further, the hardware parts of the primary fuel injection system 116 and the secondary fuel injection system 118 comprises a fuel pump, a fuel injector, a fuel tank, and the like. These components are different for each fuel injection system. Some hardware components are possible to be shared such as fuel injector and not limited to the same.

[0016] In accordance to an embodiment of the present invention, the ACO 120 is performed to keep the secondary fuel based limp home fuel system in an operating state. The control unit 110 keeps using the limp home fuel system of the bi-fuel vehicle so that the limp home fuel system is operational at the time of actual need. In order to keep the limp home fuel system in operation state, the control unit 110 keeps using the secondary fuel whenever the first set of conditions are satisfied.

[0017] In accordance to an embodiment of the present invention, the primary fuel and the secondary fuel which are selected from at least one of a gaseous medium and liquid medium comprises a CNG a Liquefied Petroleum Gas (LPG),PNG, natural gas, methanol, a Liquefied Natural Gas (LNG), gasoline, diesel ethanol, flex-fuel, hydrogen fuel and the like. Further as an example, the bi-fuel (or dual fuel) vehicle uses primary fuel as CNG and secondary fuel as gasoline.

[0018] In accordance to the present invention, a working of the control unit 110 is explained. Consider the vehicle is being started in the morning by the user. The engine temperature is same as ambient temperature. The control unit 110 detects all the conditions of the first set of conditions and the engine temperature is detected to be less than the threshold, and therefore the engine operation using the secondary fuel is not triggered. The control unit 110 keeps the ACO 120 in disabled/OFF state and operates the engine in primary fuel. Consider the vehicle is now driven for some distance and stops the vehicle. The user again restarts the vehicle as detected by the ignition key in the ON position. Now, all the conditions of the first set of conditions are satisfied including the engine temperature greater than threshold temperature (which is calibratable). The control unit 110 triggers the engine operation based on the secondary fuel.

[0019] According to the present invention, the working of the control unit 110 using another example is envisaged. Consider the vehicle is started by the user. In a previous drive cycle, the ACO 120 was active however only 50% of lower limit of secondary fuel was consumed. As the vehicle is started, the control unit 110 checks for the first set of conditions and finds that ACO 120 is not completed. For the ACO 120 to be completed, the lower limit of fuel consumption of the secondary fuel must be met to ensure the required operation of the limp home fuel system. The lower limit is the minimum fuel which unless and until is consumed, the control unit 110 will not consider the ACO 120 is complete. The control unit 110 also allows the completion of lower limit for fuel quantity to be consumed in different drive cycle and need not be in single drive cycle. For example, in two, three drive cycles. Further, in case the lower limit is reached, and the vehicle is not stopped, the control unit 110 waits until the upper limit is also reached to ensure proper operation and then switches back to primary fuel when the upper limit is also exceeded. By reaching the upper limit or the lower limit, at least one secondary set of condition is satisfied, and thus the control unit 110 switches back to primary fuel. This is just an example and must not be understood in limiting manner.

[0020] Fig. 2 illustrates a method for ACO of the engine operation, according to the present invention. The ACO 120 of engine operation is between the primary fuel and the secondary fuel in the bi-fuel vehicle. The primary fuel and the secondary fuel are selected from at least one of a gaseous medium and liquid medium. The method comprises plurality of steps of which a step 202 comprises determining occurrence of the condition comprising engine temperature for switching from the primary fuel to said secondary fuel. The method is characterized by a step 204, which comprises switching engine operation between the primary fuel and the secondary fuel after detecting any one of the first set of conditions and the second set of conditions. The switching from the primary fuel to the secondary fuel is based on fulfillment of the first set of conditions and switching from the secondary fuel to the primary fuel is based on the fulfillment of the secondary set of conditions.

[0021] According the present invention, the method checks both the first set of condition and the second set of condition irrespective of the present state of the ACO 120. Alternatively, the method checks for the first set of condition if the secondary fuel is being used, and checks the second set of condition if the primary fuel is being used. Further, the method checks for one or combinations of additional conditions in the first set of conditions and the second set of conditions.

[0022] According the present invention, the first set of condition is at least one selected from the group comprising engine temperature is greater than a threshold engine temperature, engine speed is zero, detecting the new drive cycle of the vehicle, the ACO 120 is not completed from previous drive cycle, the vehicle is running in the primary fuel and the vehicle is not enabled with ACO 120. Similarly, the second set of conditions is at least one selected from the group comprising the soak condition and the reset condition. The soak condition comprises checking difference between the engine temperature and the ambient temperature is below the threshold difference, and the ambient temperature is less than the threshold temperature. The reset condition disables the ACO 120 and switches the vehicle back to primary fuel. The reset condition is any one selected from the group comprising the error in any one of the vehicle, the hardware parts and the ACO 120, the number of failed starts in secondary fuel exceeds the threshold count, the secondary fuel consumption is more than the upper threshold quantity and a fuel cut-off request is received, the secondary fuel consumption is more than the lower limit and any one of the ignition Key On state or new drive cycle is detected, the low fuel level of the secondary fuel is detected, and the duration of failed crank attempts is greater than the threshold duration. The reasons for each of the first set of conditions and the second set of conditions are explained under Fig. 1 description and not repeated here for simplicity. The method of ACO 120 is performed to keep the secondary fuel based limp home fuel system in an operating state.

[0023] According to an embodiment of the present invention, the control unit 110 and the method are suitable to be implemented for bi-fuel vehicle selected from a two-wheeler, a three-wheeler, four-wheeler, and other types of vehicles.

[0024] According to the present invention, an auto change over between primary fuel to limp home fuel and vice-versa is provided. The control unit 110 and the method ensures that the secondary fuel injection system 118 is operational and functional when actually needed. The secondary fuel injection system 118 is kept functional by operating during the functioning of the primary fuel injection system 116 as per predetermined criteria.

[0025] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.