WO2015116628A1

WO2015116628A1 - Circuit enabling start function without relay

Info

Publication number: WO2015116628A1
Application number: PCT/US2015/013200
Authority: WO
Inventors: Todd W. Fritz
Original assignee: Eaton Corporation
Priority date: 2014-01-29
Filing date: 2015-01-28
Publication date: 2015-08-06

Abstract

An engine starter interlock circuit includes an interface circuit configured to present a predefined load to a transmission controller for diagnostics and receives first and second transmission start enable signals. A first logic circuit is configured to output a control signal when the first and second transmission start enable signals indicate that the transmission is in a state where starting of the engine is permitted. A second logic circuit generates a start command signals when both the control signal and one or more vehicle start enable signals indicate that starting of the engine is permitted. A latch is configured to maintain the control signal in an asserted state while the start command signal is being generated (i.e., in the asserted state). The interlock circuit includes a switch responsive to the start command signal configured to energize an electric engine starter assembly for cranking the engine.

Description

INTERLOCK CIRCUIT OF STARTING SYSTEM FOR COMBUSTION ENGINE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States provisional application no.

61/932,902, filed January 29, 2014 (the '902 application). The '902 application is hereby incorporated by reference as though fully set forth herein.

BACKGROUND

a. Technical Field

[0002] The instant disclosure relates generally to a circuit to enable an engine start function and more particularly to an engine starter interlock circuit to enable an engine start function without the use of an electro-magnetic relay. b. Background Art

[0003] This background description is set forth below for the purpose of providing context only. Therefore, any aspects of this background description, to the extent that it does not otherwise qualify as prior art, is neither expressly nor impliedly admitted as prior art against the instant disclosure.

[0004] A requirement for a so-called engine starter interlock, applied to motor vehicles, is provided for in the U.S. Department of Transportation, Federal Motor Carrier Safety Administration, Rules & Regulations, Subpart B-Federal Motor Vehicle Safety Standards, Part 571 Standard No. 102 ("FMVSS 571.102"). The engine starter interlock generally calls for the engine starter to be rendered inoperative when the transmission shift position is in a forward or reverse drive position. In a known system, a transmission control module is used to control the engine starter interlock by generating a start enable signal— thereby enabling engine cranking— by sensing when predetermined conditions permitting engine starting are present. For example, the transmission control module can monitor feedback signals from the transmission to ascertain a neutral gear position status and/or a master clutch dis-engaged status, and then generate the above-mentioned start enable signal(s) accordingly. However, there are challenges in such known systems.

[0005] First, the transmission control module used to generally control the automatic or semi-automatic gear-change transmission can include an electronic control unit (e.g., microprocessor) and/or electronic circuits that can be sensitive to supply voltage (battery voltage) fluctuations. A starter motor ordinarily draws a relatively large current during cranking that can cause the battery voltage to decrease to a relatively low value (i.e., a "brownout"). A low enough battery voltage can reset the microprocessor and/or other circuits thereby also resetting the engine starter enable signal which could have the unintended effect of disabling engine cranking, even when the battery voltage is still high enough that it would have been able to crank and start the engine successfully if not interrupted. One approach to address this situation involves latching a start enable relay in an active state, for example only, as seen by reference to U.S. pat. no. 5,252,861, hereby incorporated by reference in its entirety. [0006] Second, as noted above, it is also known to use an electromagnetic start enable relay— responsive to the start enable signal— to overcome the interlock and thus enable engine starter operation. However, the use of a relay in general can increase cost and complexity of the overall system.

[0007] The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.

SUMMARY

[0008] In an embodiment, in an engine-powered vehicle having a gear-change transmission coupled to an engine that can be cranked with an electric engine starter assembly, an engine starter interlock circuit is provided that comprises an interface circuit, a first logic circuit including a latch, a second logic circuit, and a switch. The interface circuit is configured to present a predefined load with respect to a transmission controller for diagnostic purposes and for receiving first and second transmission start enable signals. In an embodiment, the load comprises a resistive load that substitutes for the load presented by a relay in traditional implementations (i.e., interlock circuit embodiments consistent with the present teachings present substantially the same to the transmission controller for diagnostic purposes).

[0009] The first logic circuit is configured to process the first and second transmission start enable signals and to output a control signal when the first and second transmission start enable signals indicate that the transmission is in a state where starting of the engine is permitted. The second logic circuit is configured to generate a start command signal when both the control signal and one or more vehicle start enable signals indicate that starting of the engine is permitted. The switch is responsive to the start command signal to output an energizing signal to a start circuit so as to energize the electric engine starter assembly for cranking the engine. The first logic circuit includes the latch, which is responsive to the start command signal and maintains the control signal (in an asserted state) while the start command signal is being generated (i.e., in the asserted state). The latch overcomes the problem associated with battery voltage dip (i.e., "brownout") that can occur during engine cranking.

[0010] The foregoing and other aspects, features, details, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a block diagram of an engine starter interlock circuit for an automotive or commercial vehicle.

[0012] Figure 2 is a first embodiment of the engine starter interlock circuit illustrated in block form in Figure 1.

[0013] Figure 3 is a truth table diagram corresponding to the operation of the embodiment of Figure 2.

[0014] Figure 4 is a second embodiment of the engine starter interlock circuit of

Figure 1 , which combines the embodiment of Figure 2 with a controller area network (CAN) messaging embodiment.

[0015] Figure 5 is a block diagram view of an exemplary ETC7 Transmission Engine

Crank Enable (SPN 2900) message that is broadcast by the transmission controller in Figure 4 to allow or disable engine cranking based on predetermined transmission conditions.

[0016] Figure 6 is a simplified schematic and block diagram view of an engine interlock circuit that uses a start enable relay and a latch diode. DETAILED DESCRIPTION

[0017] Various embodiments are described herein to various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims. [0018] Before proceeding to a detailed description of engine starter interlock circuit according to the instant disclosure, an overview description— for comparison purposes— will be first described in connection with Figure 6 of an implementation of an engine starter interlock circuit that uses a start enable relay and a latch diode.

[0019] Figure 6 shows an engine starter configuration having an engine starter interlock function, which disables engine cranking unless certain transmission conditions and applicable other conditions are positively verified. In the illustrated implementation, the transmission controller, rather than a vehicle or body controller, determines whether the transmission is in a state where engine starting is permitted.

[0020] With continued reference to Figure 6, a start enable relay 500 is responsive to both a start enable relay (positive) signal and a start enable relay (negative) signal to selectively pass to a contactor Kl, when activated, an operator-enabled engine start voltage

502 via an ignition key operated switch 504. The start enable relay 500 includes an activation coil having an activation current path (e.g., between points e-f) and a switched load path. The start enable relay signals are generated by the transmission controller and are asserted— thereby enabling engine starting— when the controller determines that the transmission is in a state where engine starting is permitted. For example, the start enable relay signals are asserted (activated) when the transmission is in a neutral gear position and a master clutch of the transmission is disengaged. Likewise, the start enable relay signals are de-asserted (de-activated) when the transmission is not in a neutral gear position and/or the clutch is engaged. The start enable relay 500 provides an interlock function because it is normally open, which interrupts a current path from the engine start switch 504 to the contactor Kl . However, the implementation in Figure 6 present certain challenges. [0021] Sensitivity to Electrical Faults. While the implementation in Figure 6 uses a pair of semiconductor switches to produce the pair of start enable relay signals, in some implementations (not shown) of automated transmissions, an engine starter interlock relay can be controlled by a single semiconductor switch. In a single semiconductor switch arrangement, one of the terminals of the activation coil (i.e., either one of e or f) is connected to either the positive battery terminal or the negative battery terminal (ground), while the other one of the terminals is connected to the single semiconductor switch to complete the current path through the activation coil, which activates the start enable relay. In other words, there are two main configurations for a single semiconductor switch arrangement. A first configuration involves connecting one of the terminals of the activation coil to battery positive, and using a single low side switch to electrically connect the other activation coil terminal to battery negative or ground. A second configuration involves connecting one of the terminals of the relay (activation) coil to battery negative (ground), and using a single high side switch to electrically connect the other terminal to battery positive. [0022] In light of the above, there are three potential electrical faults that could inadvertently defeat (disable) the engine starter interlock function. In the first configuration mentioned above (high side direct connection), a short circuit of the negative terminal of the activation coil to vehicle frame rail ground can activate the relay, closing the relay contacts— thereby defeating (disabling) the interlock function. In the second configuration (low side direct connection), a short circuit of the positive connection to battery positive can activate the relay, closing the relay contacts— thereby also defeating (disabling) the interlock function. In addition, the potential for a reverse battery connection of the transmission control module with respect to other vehicle electrical systems can create a current path through the semiconductor switch that can also inadvertently activate the start enable relay— thereby also defeating (disabling) the interlock function.

[0023] Returning to Figure 6, the illustrated implementation utilizes two electrical semiconductor switches (rather than one as discussed immediately above) to produce two start enable relay signals. The use of two start enable relay signals can provide a mechanism to reduce or eliminate the potential problems associated electrical faults. As shown, the activation coil of the start enable relay 500 (i.e., between terminals marked e-f) is connected in series with the two electrical switches and a diode. The diode blocks the current path mentioned above due to a reverse voltage condition, which prevents activation of the start enable relay. Additionally, electrical shorts on one or the other of the terminals of the activation coil can be addressed by turning off the semiconductor switch on the opposite terminal from the short. For example, a short to battery positive fault on the high side of the activation coil can be addressed by turning off the low side switch, which ensures that the start enable relay will not be activated due to the short. Likewise, a short to vehicle ground fault (i.e., battery negative) on the low side of the activation coil may be addressed by turning off the high side switch, which also ensures that the start enable relay will not be activated due to the short.

[0024] "Brownout " During Engine Cranking. The battery voltage "brownout" condition described in the Background section of this application is also addressed in the implementation shown in Figure 6. Specifically, a latch diode 506 is provided. Once the start enable relay 500 has been activated (and the start voltage applied via start switch 504 to start engine cranking), the battery positive voltage at node a is routed through path a-b-c-d-e to the activation coil of the start enable relay 500. The start enable relay 500 is therefore latched "on" through diode 506.

[0025] In sum, in certain implementations that use a start enable relay 500, occurrence of faults may inadvertently defeat (disable) the engine start interlock function and thereby allow engine starter operation, even when the transmission is not in a neutral gear position. In addition, the start enable relay and the associated wiring circuit(s) can add cost and complexity to the overall system and thus also potentially reduce reliability. There is also the potential for human intervention of the engine starter interlock function to bypass the relay contacts. Also, with the implementation of the start enable relay, the system is sensitive to high current load(s) on the vehicle battery, for example, during engine cranking, that can present a low voltage ("brownout") on the vehicle electrical system, which in turn may cause a control circuit or relay to disconnect (dropout) or reset. While the use of a latching solution, such as the latch diode 506 described above, provides additional tolerance to a "brownout", it nonetheless adds cost to the system and potentially reduces reliability as well. Moreover, there is a potential for incorrectly wiring the start enable relay and latch diode, leading to complexity in the installation and in troubleshooting of the interlock. For at least all these reasons, an improved engine starter interlock circuit is desired. [0026] Referring now to the drawings wherein like reference numerals are used to identify identical or similar components in the various views, Figure 1 is a block diagram showing an engine-powered vehicle 10 (dashed- line block form) which includes a transmission controller 12, a vehicle or body controller 14 (hereinafter "body controller 14"), a start circuit 16 for providing an energizing signal for energizing an electrically-actuated engine starter assembly 18, an engine 20 selectively coupled to the engine start assembly 18, and a gear-change transmission 22 coupled to the engine 20.

[0027] The body controller 14 includes an engine starter interlock circuit 24 that prevents or blocks— unless defeated— engine starting even when an engine start signal 26 has been asserted (e.g., operator enabled— key ignition to START position; shown as block 26). The interlock circuit 24 prevents the start circuit 16 from energizing the engine starter assembly 18 used to crank the engine 20. The body controller 14 also includes an electronic control unit (ECU) 28, which may include a conventional microprocessor or the like, and a memory block 30 coupled to the ECU 28. The memory 30 may comprise conventional memory components. Programmed logic (i.e., software) may be stored in the memory 30 and be configured to be executed by the ECU 28 to perform one or more functions.

[0028] The transmission controller 12 is configured to determine whether one or more predetermined conditions in the transmission 22 have been satisfied and then to generate one or more start enable signals 32. The start enable signal(s) 32 indicate, when asserted, that the transmission 22 is in a state where starting of the engine 20 is permitted (e.g., neutral gear position). The transmission controller 12 may include an electronic control unit (ECU) 34, which may include a conventional microprocessor or the like, and a memory block 36 coupled to the ECU 34. The memory 36 may comprise conventional memory components. Programmed logic (software) may be stored in the memory 36 and be configured to be executed by the ECU 34 to perform one or more functions.

[0029] The transmission controller 12 further includes engine start enable/disable logic 38 that is configured to output the one or more start enable signal(s) 32. The engine start enable/disable logic 38 is responsive to one or more inputs 40 through which the logic 38 can determine whether the transmission 22 is in a state where starting of the engine 20 is permitted. In an embodiment, the start enable signal 32 may be a single signal. In another embodiment, however, the start enable signal 32 comprises a pair of signals, which together indicate when the transmission is in the state where starting of the engine is permitted. For example, a pair of signals can drive respective switches to more reliably communicate to the vehicle/body controller 14 that the engine starter interlock can be disabled. The engine start enable/disable logic 38 may comprise discrete electronic components configured to process the inputs 40 or alternatively may comprise programmed instructions. [0030] The state of the transmission when starting of the engine is permitted includes at least one of (i) a first condition where the transmission is in a neutral gear position and (ii) a second condition where a master clutch of the transmission is disengaged. The

transmission controller 12 may include one or more electrical and/or mechanical connections 42 to the transmission 22 for the purpose of obtaining or determining such inputs. Exemplary mechanisms through which the inputs 40 can be determined will be described below.

[0031] On manual gear-change transmissions, the shift gear position is determined by the position of a mechanical shift lever. The shift lever can be mounted to a shift-bar housing of the transmission. The shift-bar housing has a mechanical interlock and detent positions for the gear shift mechanism. An electrical switch— not shown— is closed through mechanical actuation when the transmission gear select shift-bars are aligned in a predefined gear-neutral position. In other words, a switch is closed when the transmission is in a neutral gear position, and the switch closure is then detected and processed by the logic 38 of the transmission controller 12.

[0032] On an automated mechanical transmission, the operator-adjustable shift lever is removed and the vehicle operator is provided in replacement thereof an electrical- mechanical interface device (e.g., a button to press). The operator interface device provides the transmission a shift-by- wire command signal of the operator's intent of a gear selection. The electrical signal indicating the operator-selected gear is in turn interpreted by the electronics (or programmed logic) of the transmission controller 12. Shift actuation is implemented in the transmission using an electrically-controlled mechanism to select gear engagement and neutral gear positions on one or more shift rails. To provide the starter interlock function, one or more position sensors and embedded control logic are used to determine the gear-neutral position of the shift actuator. The logic 38 in the transmission controller 12 can then determine if the transmission 22 is in a neutral-gear position. [0033] The logic 38 cooperates with logic inputs 78 (best shown in Fig. 2) to determine the status of one or more safety interlock functions of the vehicle in order to provide signal 76 to the starter control logic 74. These additional logic signals (block 78) are combined to provide the start enable intent signal 76 based upon the status of vehicle signals used to determine that the operator is intending to start the engine 20, and that furthermore it is safe to start the engine. Examples for logic input block 78 include enabled or safe state of the vehicle power switch, the engine start switch (engine start— described below also), the ignition switch, vehicle anti-theft security logic, engine hood cover-in-place, brake switch active, engine stopped logic, and any other proprietary logic that a vehicle integrator may define.

[0034] Figure 2 is a first embodiment of the engine starter interlock circuit shown in block form in Figure 1 (item 24). In addition, Figure 2 further shows (i) a source of electrical power, such as a battery 44 having positive (+) and negative (-) terminals; (ii) the starter circuit 16, which in the illustrated embodiment may comprise an electro-magnetic contactor that includes positive and negative activation terminals 46 and positive and negative load terminals 48; and (iii) the electric engine starter assembly 18, which in the illustrated embodiment includes a solenoid 50 having positive and negative energization terminals and an electric starter motor 52 with associated positive and negative terminals (coupled to battery positive and negative terminals). [0035] As described above, the transmission controller 12 through the logic 38 is configured to produce a pair of start enable signals, namely, a first transmission start enable signal (positive) 601 and a second transmission start enable signal (negative) 6Ο2 as shown. The logic 38 of Figure 1 includes, in the illustrated embodiment of Figure 2, a first portion, namely, a start enable logic function 38a and a second portion, namely, a start disable logic function 38b. Logic functions 38a, 38b operate as follows.

[0036] When the transmission 22 is in the state where the starting of the engine is permitted: (i) the start enable logic function 38a generates a logic high signal to turn on a high side driver 54 to thereby pull up the start enable (positive) signal 6O1 to the positive (+) battery bus level; and (ii) the start enable logic function 38b generates a logic high signal to turn on a low side driver 56 to thereby pull down the start enable (negative) signal 60₂ to the ground (-) battery level. The drivers 54, 56 may comprise conventional components known in the art, for example only, semiconductor devices, such as field effect transistor devices, commercially available under the trade name SmartFET from ON Semiconductor, 5005 East McDowell Road, Phoenix, AZ USA or ProFET from Infineon Technologies North America Corporation, 640 N. McCarthy Blvd., Milpitas, CA USA. It should be understood that the instant teachings are not limited to the foregoing devices. The transmission controller 12 further includes a diode 58 disposed between the low side and high side drivers 54, 56.

[0037] While the transmission controller 12 determines the conditions as to when to disable the engine starter interlock circuit, in the illustrated embodiment, the engine starter interlock function per se may be implemented in the body controller 14. The engine starter interlock circuit in the body controller 14 operates in accordance with the truth table shown in Figure 3. The engine starter interlock circuit includes an interface circuit 62, a first logic circuit 70, a second logic circuit 74, and a switch 82.

[0038] The interface circuit 62 includes a predefined load such as a resistor 64 and a level-shifting circuit 66. The resistor 64 is configured to present a predefined load to the transmission controller 12, for example, so as to permit diagnostic functions to be performed by the controller 12, such as electrical continuity checks, electrical fault checks (e.g., electrical shorts), and/or to provide a feedback path to sample the voltage level at the input of element 86₁ (or at point "B" in an embodiment where circuit 66 is omitted). The resistor 64, in an embodiment, may have a resistance value selected to approximate the load presented by a start enable relay, such as relay 500 (Figure 6). This selection allows for backwards compatibility with the transmission controller 12. In an embodiment, the resistor 64 may have a resistance of about 65-100 ohms (based on the replacement of a 12 volt start enable relay). It should be understood, however, that the foregoing is exemplary only and not limiting in nature. For example, a load circuit having comparable electrical properties may be substituted for the resistor 64. [0039] The level-shifting circuit 66 is configured to receive the first and second transmission start enable signals 60₁, 60₂-at a battery level— and then output, via respective level-shifting elements 86i, 86₂, the first and second transmission start enable signals 68₁, 68₂ at a modified, logic-level output. The level-shifting circuit 66 provides logic level outputs (e.g., 0 volts for a logic low or 5 volts for a logic high) that provide compatibility with downstream logic-level circuits, such as the first and second logic circuits 70, 74. In an alternate embodiment, the downstream circuits can be formed using battery-level components, in which case the level-shifting circuit 66 can be omitted. In a further alternate embodiment, the logic 38 in the transmission controller 12 may be configured to directly generate the start enable signals 32 at a logic levels (rather than battery levels), in which case the level-shifting circuit 66 can be omitted.

[0040] In an embodiment, the level-shifting elements 86i, 86₂ may comprise differential comparator elements or operational amplifier elements configured to detect when an input is within a predefined range corresponding to a logic 1 or a logic 0. For example, element 86₁ may be configured so that when the input signal 60₁ is equal to or greater than a predefined threshold (e.g., between about 0.7-0.8 of the battery voltage), the element 86₁ will output a logic 1 (e.g., 5 volts), otherwise it will output a logic 0 (e.g., about 0 volts).

Additionally, the element 86₂ may be configured so that when the input signal 6Ο₂ is equal to or less than a predefined threshold (e.g., between about 0.2-0.3 of the battery voltage), the element 86₁ will output a logic 0 (e.g., about 0 volts), otherwise it will output a logic 1 (e.g., 5 volts). These levels are exemplary only. Further, hysteresis may be incorporated into the configuration to minimize undesired switching between output states. In an embodiment, level-shifting elements 86₁, 86₂ may comprise commercially available components, such as differential comparator part no. LM339 or operational amplifier part no. LM324, from Texas Instruments Incorporated, 12500 TI Boulevard, Dallas, TX USA.

[0041] The first logic circuit 70 is configured to process the logic-level start enable signals 68₁, 68₂ and determines when the signals 68₁, 68₂ together have respective logic levels that indicate that the transmission is in a state where starting of the engine is permitted. When the first logic circuit 70 makes this determination, circuit 70 generates an output control signal 72. The output control signal 72 is a single signal that represents the transmission's state (whether engine starting is permitted or not).

[0042] In the illustrated embodiment, the first logic circuit 70 includes an OR logic gate 88 having (i) a first input receiving the modified, logic-level, first transmission start enable signal 68₁ and (ii) a second input receiving the (engine) start command signal 80. The first logic circuit 70 further includes an inverter logic gate 90 having an input configured to receive the modified, logic-level, second transmission start enable signal 68₂. The first logic circuit 70 still further includes an AND logic gate 92 having a pair of inputs configured to receive the respective outputs of the OR logic gate 88 and the inverter logic gate 90. The AND logic gate 92 includes an output for producing the above-mentioned control signal 72. [0043] The first logic circuit 70 includes a latch that is responsive to the start command signal 80 and maintains the control signal 72— and thus also the start command signal 80— in an asserted (active) state once the start command signal 80 has been initially asserted (active) by the second logic circuit 74 described below. The latch includes the above-mentioned OR logic gate 88 as well as a feedback line to carry the start command signal 80 from the output of the second logic circuit 74 (i.e., an AND logic gate 94) to the input of the OR logic gate 88. The latch is useful to address the problem of a battery voltage level dip ("brownout") during engine cranking. The latch function will maintain the start command signal 80 active, even if the first (positive) start enable signal 601 falls below the threshold where element 86i would output a logic 1.

[0044] The second logic circuit 74 is configured to output a start command signal 80 when the control signal 72 (indicating whether or not the transmission is in a state where starting is permitted) and one or more vehicle start enable signals 76 (indicating the vehicle is in a state where starting is permitted), both indicate permit engine starting. The vehicle start enable signals 76 may include at least an operator-enabled vehicle start signal 78 (i.e., key ignition start position). The ignition key start signal 78 typically is produced at a battery level voltage; however, in the illustrated embodiment, the signal 78 comprises a logic-level signal. The second logic circuit 74 may include an AND logic gate 94 having a first input configured to receive the control signal 72 and a second input configured to receive the above-mentioned vehicle start enable signals 76. Both signals 72, 76 must be a logic 1 in order for the start command signal 80 to be asserted.

[0045] The signal 80 (and thus also the signal 84) results from a logic AND function requiring an assertion or true state for plural input signals indicating that there is an intent to start the vehicle (operator, secondary start request, or remote engine start) AND that the power train (e.g., transmission 22) is in a neutral state AND that specific safeties are in place before engine start is enabled (i.e., signal 80 is asserted, which in turn asserts signal 84 to activate the switch 16). As noted above, safety and security interlock functions provide an enable signal (e.g., represented by a single signal 76— illustrative only) in addition to the clutch and transmission (e.g., represented by a single signal 72— illustrative only). In other embodiments (not shown), for example only Hybrid Electric embodiments or Hydraulic Hybrid embodiments, or any other architecture that includes start-stop of the engine under control of an engine power storage management system, the engine (and/or vehicle) start can be enabled by predefined operating logic (e.g., a determined state of energy storage) rather than by expressed operator intent (e.g., turn of a key switch).

[0046] A secondary function of the engine operation, however, can be to provide electrical power for entertainment and/or living space illumination, as well as for heating, ventilation, and air conditioning. This is commonly referred to as "Hotel" operation of the vehicle, where the vehicle operator sleeps/rests or otherwise remains in his vehicle but with the vehicle in a stopped condition (i.e., the vehicle is not being operated for movement). In this embodiment, the engine start management system may be configured to monitor several signals to verify that starting of the engine would not pose a risk for inadvertent vehicle movement. If such signals are verified, the engine start management system/logic will enable engine starting. These signals may include but are not limited to verifying that the transmission gear selection lever is in a non-drive mode such as a neutral position or a Park position; that the parking brake is active; that the vehicle is stopped without vehicle speed being measured; that a "Hotel" electric storage battery requires charging; that a heating, ventilation, and/or air conditioning function is requesting operation; and that the operator has requested that the vehicle be placed in the "Hotel" mode of operation.

[0047] With continued reference to Figure 2, the switch 82 (e.g., driver) is responsive to the start command signal 80 and is configured to produce an energizing signal 84 (e.g., battery voltage (+)) to be applied to the start circuit 16, which activates the start circuit (magnetic relay 16) to thereby energize the engine starter assembly 18. Energizing the engine starter assembly 18 results in cranking of the engine 20. The switch 82 may comprise the same component as described above for drivers 54, 56

[0048] Figure 3 is a truth table diagram corresponding to the different states of operation of the engine starter interlock circuit of Figure 2. As described above, the first and second transmission start enable signals 60ι, 6Ο2 together indicate whether or not the transmission is in a state where cranking of the engine is permitted. As shown in Figure 3, the start enable signals are active when (i) signal 601 is about 12 volts (i.e., battery voltage) corresponding to a logic 1 and (ii) signal 6Ο2 is about 0 volts (ground) corresponding to a logic 0. Conversely, the start enable signals are inactive when (i) signal 6Ο2 is about 6 volts corresponding to a logic 0 and (ii) signal 60₂ is about 6 volts corresponding to a logic 1. [0049] With reference to the table in Figure 3, when signals 601, 6Ο2 are active, the control signal 72 (column D) will assume a logic 1; however, the start command signal 80 (column M) will remain a logic 0 until the vehicle start enable signal 76 (Column E) also goes to a logic 1 (e.g., when the ignition key start signal 78 is enabled by the operator). Once the start command signal 80 goes to a logic 1, the above-mentioned latch (feedback of the start command signal 80 to the OR logic gate 88) will maintain the start command signal 80 at a logic 1, even if the signal 601 dips during engine cranking ("brownout") to the point where signal 601 is not high enough to maintain a logic 1 at the output of the level-shift circuit 66 (column B). [0050] Figure 4 is a second embodiment of the engine starter interlock circuit of

Figure 1 , which combines the embodiment of Figure 2 with a controller area network (CAN) messaging embodiment. The CAN messaging function can provide backup/redundant functionality with respect to the interlock circuit of Figure 2 alone.

[0051] Figure 4 shows that the transmission controller 12 and the body controller 14 are in communication in the same manner as in Figure 2, namely, at least by virtue of the above-described interconnections that transfer the transmission start enable signals 601, 6Ο2 from the transmission controller 12 to the body controller 14. In addition, Figure 4 further shows that the transmission controller 12 and the body controller 14 are in communication by way of a pair of CAN communication lines (J1939_CAN_HIGH and J1939_CAN_LOW) that are configured to carry CAN messages, such as a CAN-compliant transmission engine crank enable message 96 best shown in Figure 5. More particularly, in an embodiment, the message 96 as part of a controller area network (CAN) communication packet utilizes the ETC7 Transmission Engine Crank Enable (SPN 2900) message broadcast by the transmission controller 12 to allow or disable engine cranking based on predetermined transmission conditions (already described above) in accordance with SAE J1939-71 specifications. For example, the Transmission Engine Crank Enable Message 96 in accordance with SAE J1939- 71 and ETC7 SPN 2900 provides an indication that the block message 96 is the CAN message from the transmission controller (i.e., shown as the transmission control module 12 in Fig. 4) to the engine controller (i.e., shown as the engine control module in Fig. 4) or body controller 14 (i.e., shown as the body control module in Fig. 4). Both of the transmission controller 12 and the body controller 14 include a conventional CAN module and bus transceiver components (not shown) that allow communication of CAN messages, as known generally.

[0052] In operation, the transmission controller 12, through the logic 38 (Figure 1), determines when the transmission 22 is in a state where starting of the engine 20 is permitted (as described above). In this embodiment, the transmission controller 12 activates the transmission start enable signals 60ι, 6Ο2 as already described above. Additionally, however, the transmission controller 12 formats an engine crank message 96 and broadcasts the message 96 on the CAN bus. The transmission controller 12 may utilize an electronic transmission controller ETC7 Transmission Engine Crank Enable (Subject Parameter Number SPN 2900) message broadcast, which can be received, recognized and processed by the body controller 14 to allow or disable engine cranking (in accordance with SAE J1939-71 specifications). It should be understood, however, that for engine cranking to occur, other remaining conditions must be satisfied, specifically at least that the vehicle operator initiate engine cranking by moving the ignition key to the starting position. [0053] It should be understood that an electronic processor as described above for certain embodiments can include conventional processing apparatus known in the art, capable of executing pre-programmed instructions stored in an associated memory, all performing in accordance with the functionality described herein. To the extent that the methods described herein are embodied in software, the resulting software can be stored in an associated memory and can also constitute the means for performing such methods. Implementation of certain embodiments, where done so in software, would require no more than routine application of programming skills by one of ordinary skill in the art, in view of the foregoing enabling description. Such an electronic processor can be of the type having both ROM, RAM, a combination of non- volatile and volatile (modifiable) memory so that the software and predetermined data can be stored and yet allow storage and processing of dynamically produced data and/or signals.

[0054] It should be further understood that an article of manufacture in accordance with this disclosure includes a computer-readable storage medium having a computer program encoded thereon for implementing the start enable logic and other functionality described herein. The computer program includes code to perform one or more of the methods disclosed herein. [0055] Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

[0056] While one or more particular embodiments have been shown and described, it will be understood by those of skill in the art that various changes and modifications can be made without departing from the spirit and scope of the present teachings.

Claims

CLAIMS What is claimed is:

1. In an engine-powered vehicle having a gear-change transmission coupled to an engine that can be cranked with an electric engine starter assembly, an engine starter interlock circuit comprising: an interface circuit configured to present a predefined load to a transmission controller for diagnostic purposes and to receive at least a first transmission start enable signal from the transmission controller indicating when the transmission is in a state where starting of the engine is permitted, the interface circuit being further configured to output a modified, logic-level first transmission start enable signal; a first logic circuit responsive to the modified, logic-level first transmission start enable signal configured to output a control signal indicating that the transmission is in the state where starting of the engine is permitted; a second logic circuit configured to output a start command signal when both of the control signal and one or more vehicle start enable signals indicate that starting of the engine is permitted; and a switch responsive to the start command signal configured to provide an energizing signal to a start circuit to energizing an electric engine starter assembly for cranking the engine; wherein the first logic circuit includes a latch responsive to the start command signal configured to maintain the control signal in an asserted state while the start command signal is asserted.

2. The engine starter interlock circuit of claim 1 further comprising a second transmission start enable signal wherein the first and second transmission start enable signals together indicate when the transmission is in the state where starting of the engine is permitted, the interface circuit being further responsive to the second transmission start enable signal to produce a modified, logic-level second transmission start enable signal.

3. The engine starter interlock circuit of claim 2 wherein the state of the transmission where starting of the engine is permitted includes at least one of (i) a first condition where the transmission is in a neutral gear position and (ii) a second condition where a master clutch of the transmission is disengaged.

4. The engine starter interlock circuit of claim 2 wherein the first logic circuit includes: an OR logic gate having a first input receiving the modified, logic-level first transmission start enable signal and further having a second input receiving the start command signal; an inverter logic gate having an input thereof receiving the modified, logic- level second transmission start enable signal; and an AND logic gate having a pair of inputs receiving the respective outputs of the OR logic gate and the inverter logic gate, the AND logic gate further having an output producing the control signal.

5. The engine starter interlock circuit of claim 4 wherein said latch comprises a feedback of the start command signal to the OR logic gate.

6. The engine starter interlock circuit of claim 2 wherein said second logic circuit comprises an AND logic gate having a first input the one or more vehicle start enable signals and a second input receiving the control signal, said AND logic gate further includes an output generating the start command signal.

7. The engine starter interlock circuit of claim 2 wherein the first transmission start enable signal is configured to assume a first voltage level corresponding to a battery voltage and the second transmission start enable signal is configured to assume a ground level.

8. The engine starter interlock circuit of claim 1 wherein the switch comprises a semiconductor switch.

9. The engine starter interlock circuit of claim 1 wherein the first transmission start enable signal and the second transmission start enable signal appear on respective first and second lines, wherein the load comprises a resistor connected across the first and second lines.

10. The engine starter interlock circuit of claim 1 further comprising: a controller area network (CAN) module configured to receive an engine crank enable message from the transmission controller.

1 1. The engine starter interlock circuit of claim 1 wherein the one or more vehicle start enable signals comprises an ignition key start signal.

12. In an engine-powered vehicle having a gear-change transmission coupled to an engine that can be cranked with an electric engine starter assembly, an engine starter interlock circuit comprising: an interface circuit configured to present a predefined load with respect to a transmission controller for diagnostic purposes and for receiving first and second

transmission start enable signals; a first logic circuit configured to process the first and second transmission start enable signals and to output a control signal when the first and second transmission start enable signals indicate that the transmission is in the state where starting of the engine is permitted; a second logic circuit configured to determine when both the control signal and one or more vehicle start enable signals indicate that starting of the engine is permitted and to generate a start command signal in response thereto; and a switch responsive to the start command signal to output an energizing signal to a start circuit so as to energize an electric engine starter assembly for cranking the engine; wherein the first logic circuit further includes a latch responsive to the start command signal that maintains the control signal in an asserted state while the start command signal is generated.

13. The engine starter interlock circuit of claim 12 wherein the state of the transmission where starting of the engine is permitted includes at least one of (i) a first condition where the transmission is in a neutral gear position and (ii) a second condition where a master clutch of the transmission is disengaged.

14. The engine starter interlock circuit of claim 12 wherein the first logic circuit includes: an OR logic gate having a first input receiving the first transmission start enable signal and further having a second input receiving the start command signal; an inverter logic gate having an input thereof receiving the second transmission start enable signal; and an AND logic gate having a pair of inputs receiving the respective outputs of the OR logic gate and the inverter logic gate, the AND logic gate further having an output producing the control signal.

15. The engine starter interlock circuit of claim 14 wherein the latch comprises a feedback of the start command signal to the OR logic gate.

16. The engine starter interlock circuit of claim 12 wherein said second logic circuit comprises an AND logic gate having a first input configured to receive the one or more vehicle start enable signals and a second input configured to receive the control signal, said AND logic gate further includes an output configured to generate the start command signal.