SYSTEM AND METHOD FOR OFF-HIGHWAY VEHICLE ENGINE CRANKING
FIELD
[0001] The subject matter disclosed herein relates to systems and methods for
improving engine cranking in off-highway vehicles.
BACKGROUND
[0002] Vehicles, such as off-highway vehicles (OHVs), include various systems for
cranking the engine in order to assist engine starting. The starting systems may utilize an
engine starter motor, or other engine propulsion components. In one example, the
propulsion system includes a battery that provides direct current (DC) power to an
inverter that converts the DC power into a controlled frequency alternating current (AC)
power. The AC power is then supplied to an alternator that generates rotation of a rotor,
which when coupled with the crankshaft of the engine, rotates the crankshaft for engine
starting.
[0003] However, the inventors herein have recognized OHVs may have traction
alternators, and it may be advantageous to utilize the traction alternator for engine
cranking. For example, traction alternators can be supplied with a high current, as
compared to a starter motor or an alternator which powers lights, pumps, etc. when the
engine is running. As such, the higher current can be converted into a higher mechanical
energy to crank the engine.
BRIEF DESCRIPTION[0004] In one approach, a method of operating an engine, the engine coupled to a
traction alternator for vehicle travelling and an auxiliary alternator, is disclosed. The
method comprises, in an off-highway vehicle running mode of operation, charging a
battery at a first voltage from the auxiliary alternator while supplying current from the
traction alternator to a traction motor to propel the vehicle, and, in a starting mode of
operation, generating a second, higher voltage, from stored energy to drive the traction
alternator to at least assist in starting the engine. For example, the second, higher voltage
may be generated by increasing an output of the battery via a DC-to-DC converter. In
this manner, the battery may be charged via the auxiliary alternator at a lower voltage,
and the battery may supply the traction alternator with the second, higher voltage to crank
the engine.
[0005] In another example, in an off-highway vehicle running mode (e.g., running
mode) of operation, current is supplied from the traction alternator to a traction motor via
a traction inverter to propel the vehicle, and, in a starting mode of operation, stored
energy is supplied from a first energy source and a secondary energy source to the
traction alternator to start the engine. For example, the first energy source may be a
relatively low voltage battery electrically coupled to the engine which provides electricity
for lights, pumps, etc., and the secondary energy source may be an ultracapacitor which
can deliver a higher current than the battery.
[0006] In one example, the first energy source, which outputs a lower voltage than
the secondary energy source, may charge the secondary energy source during the running
mode of operation via a DC-to-DC converter. In other examples, the secondary energy
source may be further charged via the traction alternator during the running mode ofoperation. In this way, the secondary energy source may provide a supply a high current
on demand for the traction alternator during engine cranking. Further, the charge level of
the secondary energy source may decrease at a slower rate since it can be charged via the
battery. As such, engine starting may occur even if the battery is degraded, for example.
[0007] It should be understood that the brief description above is provided to
introduce in simplified form a selection of concepts that are further described in the
detailed description. It is not meant to identify key or essential features of the claimed
subject matter, the scope of which is defined uniquely by the claims that follow the
detailed description. Furthermore, the claimed subject matter is not limited to
implementations that solve any disadvantages noted above or in any part of this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention will be better understood from reading the following
description of non-limiting embodiments, with reference to the attached drawings,
wherein below:
[0009] FIG. 1 shows an example block diagram of an engine system with a voltage
boost.
[0010] FIG. 2 shows an example block diagram of an engine system in an off-
highway vehicle with a voltage boost.
[0011] FIG. 3 shows an example block diagram of an engine system in an off-
highway vehicle with a voltage boost.[0012] FIG. 4 shows a flow chart illustrating a routine for an engine with a voltage
boost.
[0013] FIG. 5 shows an example block diagram of an engine system in an off-
highway vehicle with a secondary energy source that is charged via the engine.
[0014] FIG. 6 shows a flow chart illustrating a routine for an engine with a
secondary energy source that is charged via the engine.
[0015] FIG. 7 shows an example block diagram of an engine system in an off-
highway vehicle with a secondary energy source that is charged via a traction alternator.
[0016] FIG. 8 shows a flow chart illustrating a routine for an engine with a
secondary energy source that is charged via a traction alternator.
[0017] FIG. 9 shows an example block diagram of an engine system in an off-
highway vehicle with a secondary energy source and a hydraulic system.
[0018] FIG. 10 shows a flow chart illustrating a routine for an engine with a
secondary energy source and a hydraulic system.
[0019] FIG. 11 shows a flow chart illustrating a shut down routine for an engine
system in an off-highway vehicle with a secondary energy source.
DETAILED DESCRIPTION
[0020] The following description relates to various embodiments of an engine
system that is started via a traction alternator mechanically coupled to the engine.
Various approaches may be used to supply the traction alternator with an appropriate
level of current to crank the engine. In one embodiment, a battery is electrically coupled
to a DC-to-DC converter which boosts the output of the battery. The output of thebattery may be converted to AC for the traction alternator via a traction inverter (which
converts DC to AC for traction motors to propel the vehicle), an active rectifier, or an
inverter that is separate from the traction inverter, as described with reference to FIGS. 1-
4 .
[0021] In another embodiment, as described with reference to FIGS. 5 and 6, the
engine system further includes a secondary energy source such as an ultracapacitor which
outputs a higher voltage than the battery and which may be charged via the battery. In
this way, a relatively high level of charge may be stored such that the engine may be
started quickly, for example.
[0022] In another embodiment, the secondary energy source is charged via the
traction alternator during a running mode of operation of the engine, as described with
reference to FIGS. 7 and 8 . As such, the secondary energy source may receive energy
from two sources (the traction alternator and the battery) and a high level of charge can
be maintained in the secondary energy source.
[0023] In yet another embodiment, as described with reference to FIGS. 9 and 10,
the engine is coupled to a hydraulic system. The hydraulic system may provide another
source of energy for the battery and the secondary energy source during the engine
starting mode of operation. In this way, even if a charge level of the secondary energy
source is too low for engine cranking, the secondary energy source may be charged
before engine cranking so that the engine may start.
[0024] A routine for shutting down an engine with a secondary energy source is
described with reference to FIG. 10.[0025] Referring now to the drawings, like reference numerals are used to identify
similar components in the various views. FIGS. 1-3, 5, 7, and 9 refer to an engine system
with an electric storage battery 104, traction inverters 118, a traction alternator 120 with
an armature 124, a rotor ("R") 126, and field winding (not shown), and an engine 112.
[0026] Referring now specifically to FIG. 1, it shows the first embodiment of an
engine system 100 of an off-highway vehicle 10, which includes a voltage boost, and
which adjusts engine torque levels by continuous field shunting.
[0027] The engine system 100 comprises a controller 102, a prime mover or engine
112, a first energy source, which is an electric storage battery 104, a traction inverter 118,
and a traction alternator 120. The electric storage battery 104 supplies electrical energy
for starting the engine 112. The engine 112 may be started by generating an alternator
torque 122, which drives the crankshaft of the engine 112, as will be described in greater
detail below.
[0028] The electric storage battery 104 may be a lead-acid or nickel-cadmium type,
for example. The electric storage battery 104 may provide an output voltage of 24 volts,
depending on various parameters, including its state of charge, temperature, current draw,
etc. As an example, the controller 102 may estimate a state of charge and/or health of the
battery 104 based on input from sensors 150, 152, and 154 coupled to the battery 104 and
in communication with controller 102 for indicating a temperature, voltage, and output
current of the battery, for example. Further, during a running mode of operation electric
storage battery 104 is charged by the engine via auxiliary alternator (alternator and
rectifier) 114, and provides power to various components of the vehicle, such as lights,
pump, air-conditioning, etc.[0029] As shown the example embodiment of in FIG. 1, when the switching circuit
116 is closed, the DC supplied by the electric storage battery 104 is converted to AC and
supplied to the traction alternator 120 by the active rectifier 134 when the active rectifier
134 is made active (e.g., when the switching circuit 116 is open). Further, the active
rectifier 134 converts AC supplied by the traction alternator 120 to DC which is supplied
to the traction inverters 118. The active rectifier 134 and/or the traction invertersl 18 may
comprise at least three legs, where each leg may include at least two insulated gate
bipolar transistors (IGBT). For example, out of the six IGBTs, at least two are open
during circuit operation so that two phases are firing at a time. Furthermore, the output of
the electric storage battery 104 is boosted via DC-to-DC converter 106. As such, DC
supplied to the traction alternator may be increased to a desired level for engine cranking,
as well as regulated by the DC-to-DC converter 106.
[0030] In one example, the engine 112 may be a thermal or an internal-combustion
engine such as a 2500 horsepower, diesel engine that is used to provide the motive power
on an off-highway vehicle. In one example, the traction alternator 120 may perform two
modes of operation: during a starting mode of operation (e.g., engine cranking), the
traction alternator 120 may be an AC motor that drives the crankshaft to start the engine
112; after engine cranking, the traction alternator 120 may be a synchronous generator,
which supplies alternating current to an electric load circuit that is connected to its
armature winding 124. For example, the portion of the active rectifier 134 that converts
DC to AC to operate the traction alternator 120 as an AC motor is switched out of the
circuit when the engine is started such that the active rectifier 134 only supplies the
traction inverters 118 with DC.[0031] In the engine starting mode of operation as shown in FIG. 1, the rotor "R"
126 of the traction alternator 120 drives the crankshaft of the engine 112. The electric
energy supplied from the heavy duty electric storage battery 104 by the traction inverter
118 to the traction alternator 120 is converted into mechanical energy of the rotor 126.
The rotor 126 thus exerts torque (122) to turn the crankshaft and thereby crank the engine.
As the rotor "R" 126 accelerates, the engine speed (revolutions per minute, RPM)
increases and the back EMF generated in the armature 124 correspondingly increases,
while load current (e.g., current in the cranking circuit of FIG. 1) decreases in magnitude.
Once the rotor is rotating faster than a predetermined rate, typically about 200 rpm, the
engine is presumed to be started, and the engine cranking mode of operation is
discontinued.
[0032] The load current in the circuit thus may directly depend on battery voltage,
armature back EMF, and impedance in the circuit including that of the field. The
alternator torque 122 generated as a result of accelerating the rotor "R" 126 depends
primarily on the field resistance 128 and the back EMF of the alternator. Thus, by
shunting the field resistance continuously, it may be possible to adjust alternator torque in
real time, and in response to various operating conditions. For example, real time control
in a computer controlled system may include repeated and successive adjustment of
alternator torque by the system in response to calculations and sensor readings taken
throughout operation.
[0033] In one example, the continuous field shunting is achieved by connecting an
IGBT (not shown) in parallel to the field. The IGBT may be additionally and selectively
coupled to, and control, another component of the off-highway vehicle, for example. Theother component may include one or more of the following: a radiator fan, an air
compressor, a battery charger, a traction field regulator, or an AC traction motor. In this
manner, it is possible to utilize an IGBT to provide control of both the field, and thus the
traction alternator 120, during cranking, as well as another component that does not
operate during cranking, but operates before or after cranking, such as during off-
highway vehicle running conditions.
[0034] In one example, IGBT may be controlled by controller 102 in response to a
desired output torque, a desired speed trajectory, an actual engine speed, and/or various
other parameters, as described in further detail herein with regard to FIG. 2 . For example,
based on a comparison of the actual torque and the desired torque, the IGBT generates a
pulse width modulated (PWM) signal to continuously shunt the field via modulating the
impedance of the field. In another example, the IGBT may modulate the impedance of a
resistor connected in parallel to the field. Thus, torque supplied by a three-phase traction
alternator 120 in the starting system may be adjusted in more than two levels (e.g., 3 or
more torque levels) via continuous adjustment of field shunting of the alternator.
[0035] It may be noted that adjustment of torque among a plurality of levels may
also be achieved by connecting a series of resistors in parallel to the field winding, with
each of the resistors controlled by a switch. As multiple resistors are connected in
parallel to the field, it results in further field weakening and consequently a higher
alternator torque. The multiple switches may be in an on-state or an off-state at different
times, as adjusted by the controller, in turn allowing a plurality of torque levels during
engine cranking.[0036] As noted above, the active rectifier 134 and the IGBT may be used to control
and power the traction alternator 120 during cranking, and may also be used to control
and power another component of the off-highway vehicle 10 after engine cranking, such
as during off-highway vehicle running conditions, for example. Thus, once the engine
speed has reached about 200 rpm, for example, and the engine cylinders are firing, the
controller 102 identifies the completion of cranking and sends signals to a switching
circuit to connect traction inverters 118, which convert DC from the active rectifier 134
to AC, to the AC traction motors 148 to power the wheels 136 of the vehicle, during
subsequent engine operation.
[0037] In the example embodiment of FIG. 2, engine system 200 further includes
inverter 140. During the engine starting mode of operation, the DC supplied by the
electric storage battery 104 is converted to AC supplied to the traction alternator 120 by
the inverter 140, which is separate from the traction inverters 118. As in the example of
FIG. 1, during the engine running mode of operation, the traction alternator 120 provides
power to AC traction motors 148 via traction inverters 118. The AC from the traction
alternator 120 is converted to DC via the active rectifier 134, and traction inverters 118
convert the DC from the active rectifier 134 to AC.
[0038] In the example embodiment of FIG. 3, engine system 300 includes a transfer
switch 142 in addition to active rectifier 134. In such an embodiment, during the starting
mode of operation, transfer switch 142 is adjusted such that AC at a high voltage (which
has been converted by traction inverter 118 from DC supplied by the electric storage
battery 104) is supplied to the traction alternator 120. During the running mode of
operation, transfer switch 142 is adjusted such that the AC traction motor 148 receivescurrent from the traction inverter 118 to power wheels 136, and current is supplied to
traction inverters 118 from the traction alternator 120 via the active rectifier 134.
[0039] Thus, FIGS. 1-3 show embodiments of engine systems which have an electric
storage battery 104 that is boosted by a DC-to-DC converter 106. As described above, in
an engine starting mode of operation, the low voltage DC supplied by the electric storage
battery may be converted to high voltage DC via the DC-to-DC converter and to high
voltage AC for the traction alternator 120 by an active rectifier 134, a separate inverter
140, or by a traction inverter 118. In an engine running mode of operation, AC from the
traction alternator 120 is converted to DC by the active rectifier 134 before it is supplied
to the traction inverters 118.
[0040] For simplicity, FIGS. 4-1 1 will be described using an engine system that has
the basic configuration of the engine system of FIG. 1. It should be understood, however,
the engine systems described with reference to FIGS. 4-1 1 can also have the basic
configuration of FIGS. 2 or 3 .
[0041] FIG. 4 depicts a flow chart illustrating an example control routine 400 for an
engine with a voltage boost, such as engine system 100 described above. Specifically,
the routine 400 determines an operating mode of the engine and adjusts the circuitry such
that the traction alternator is used to crank the engine or to supply power to the wheels of
the vehicle.
[0042] At 410 of routine 400, it is determined if the engine is in a starting mode of
operation, such as a cranking mode, or a running mode of operation, such as a travelling
mode in which the vehicle is propelled. For example, the engine may already be running
or it may be shut down.[0043] If it is determined that the engine is in a starting mode, routine 400 proceeds
to 412 where the switching circuit 116 is adjusted (e.g., closed) to connect the battery 104
to the active rectifier 134 via the DC-to-DC converter 106.
[0044] At 414, various operating conditions may be determined. Operating
conditions may include one or more of the following, for example: battery system
conditions (voltage, current load, temperature), alternator characteristics, engine ratings
(e.g., HP rating, rated engine speed), number of cylinders, fuel type, engine operating
conditions (e.g., engine speed, engine airflow, and engine temperature), environmental
conditions, and/or system aging.
[0045] Once the operating conditions are determined, routine 400 continues to 416
where the desired torque for cranking the engine is determined. For example, the desired
alternator torque may be based on the engine speed, battery voltage, and number of
cylinders as determined at 514. In one example, the routine may utilize a desired engine
speed trajectory during cranking and run-up, and based on an error between the desired
trajectory and the actual engine speed trajectory, a desired battery voltage to achieve the
desired torque may be evaluated.
[0046] At 418 of routine 400, continuous adjustment of voltage boost is performed
so that output of the battery 104 is boosted to a desired level. In one example, based on
the engine speed error, the controller 102 sends a signal to the DC-to-DC converter 106
to adjust the battery voltage to the desired value as evaluated at 416. The boost may
increase the battery voltage to a predetermined value, and in another example, the boost
may reduce the battery voltage to a predetermined value.[0047] At 420 of routine 400, continuous adjustment of field shunting and engine
cranking torque is performed with boosted voltage. For example, with the boosted
voltage passing through the cranking circuit, the load current is generated, the alternator
torque increases, and as a result, engine speed increases. In one example, based on the
engine speed error or rate of change of speed error or power output of the battery, etc.,
the controller 102 may adjust a PWM signal to an IGBT to adjust the field shunting
resistance.
[0048] At 422 of routine 400, an engine speed check is performed. In one example,
if the engine speed has reached a predetermined speed, for example about 200 rpm, the
controller signals that the engine 112 has completed cranking and the alternator torque
supplied to the engine 112 is reduced. If the engine speed is below the predetermined
speed, then the engine cranking continues as explained at 420.
[0049] In some examples, a first engine speed check may be performed before the
engine speed check at 422. In one example, if the engine speed has reached a
predetermined speed, for example about 30 rpm, the cranking circuit may desire a lower
circuit impedance to maintain the desired load current, and therefore the controller may
send a signal to a switching circuit to close a switch and weaken the field via resistor, for
example. In such an example, when cranking mode of operation commences, and the
switch is open, the load current may be limited by integral resistance of the battery 104
and the field resistance of the traction alternator 120. As cranking proceeds and RPM
increases, the traction alternator back EMF limits the load current. Thus, the load current
and the torque tend to decrease with increasing speed. A short time after cranking begins,for example when RPM reaches about 30, closing the switch weakens the field resistance,
thereby permitting more load current to flow and higher torque to be developed.
[0050] Once the engine speed surpasses the threshold, voltage at the traction
alternator 120 is reduced at 424 of routine 400. For example, once cranking is complete,
the DC power supply from battery is shut down. Further, the alternator torque may not
be generated, and the alternator may be switched to an idle or generating mode depending
on operating conditions of the off-highway vehicle.
[0051] Once the voltage at the traction alternator 120 is reduced, or if it determined
at 410 that the engine is in a running mode, routine 400 of FIG. 4 proceeds to 426 where
the switching circuit 116 is adjusted (e.g., opened) to disconnect the battery 104 from the
active rectifier 134.
[0052] At 428 of routine 400, the battery 104 is charged via alternator and rectifier
114. At 430, it is determined if vehicle motion is desired. For example, the vehicle
operator may change a gear from Park to Drive. If it is determined that vehicle motion is
desired, routine 400 continues to 432 and the traction alternator 120 powers the traction
motors 148 to turn the wheels 136 and propel the vehicle. On the other hand, if it is
determined that vehicle motion is not desired, the routine ends.
[0053] Thus, FIG. 4 shows an example flow chart illustrating a method for operating
an engine with voltage boosting. As explained above, voltage boosting can enable the
desired variation in alternator torque among a plurality of torque levels during an engine
cranking operation.
[0054] Continuing to FIG. 5, it shows another example embodiment of an engine
system 500 with a battery 104 that may be boosted with a DC-to-DC converter 106.Engine system 500 is similar to engine system 100 described above with reference to FIG.
1, for example. The example shown in FIG. 5 further includes a secondary energy source,
electrical energy storage device 108. Electrical energy storage device 108 may be an
ultracapacitor, for example, or one or more of another suitable high capacity energy
storage device that outputs a higher voltage than the battery 104.
[0055] In the example of FIG. 5, electrical energy storage device 108 may be
isolated from the battery 104 by opening the switching circuit 138. In such an example,
electrical energy storage device 108 may be the sole source of energy supplied to the
traction alternator 120 to crank the engine. In other examples, both the electrical energy
storage device 108 and the battery 104 may be used to supply energy to the traction
alternator 120 for engine cranking. For example, by closing switching circuit 138 during
the engine starting mode of operation, the life of electrical energy storage device 108 may
be extended by the output from battery 104.
[0056] Further, in the example embodiment of FIG. 5, during the engine running
mode of operation, the electrical energy storage device 108 is charged by the engine 112
via alternator and rectifier 114 and battery 104.
[0057] Thus, FIG. 5 shows an embodiment of an engine system which has a
secondary energy source (e.g., electrical energy storage device 108), which may be
charged by a high voltage source (e.g., the traction alternator 120), in addition to a first
energy source (e.g., electric storage battery 104), which is charged by a relatively low
voltage source (e.g., alternator and rectifier 114). As described above, both the first
energy source and the secondary energy source are charged via the engine 112 when the
engine is in a running mode of operation.[0058] FIG. 6 shows a flow chart illustrating a control routine 600 for an engine
system which includes a secondary storage device, such as engine system 100 of FIG. 5 .
Specifically, the routine 600 determines an operating mode of the engine and adjusts the
circuitry accordingly.
[0059] At 610 of FIG. 6, it is determined if the engine is in a starting mode of
operation, such as a cranking mode, or a running mode of operation, such as a travelling
mode in which the vehicle is propelled. For example, the engine may already be running
or it may be shut down. If it is determined that the engine is in a starting mode of
operation, routine 600 proceeds to 612 where switching circuit 116 is adjusted to connect
electrical energy storage device 108 and battery 104 to active rectifier 134. For example,
switching circuit 116 may be closed in order to electrically connect the active rectifier
134 and the electrical energy storage device 108.
[0060] Once the switching circuit is adjusted, routine 600 continues to 614 where
operating conditions are determined. As described above, the operating conditions may
include one or more of the following, for example: battery system conditions (voltage,
current load, temperature), alternator characteristics, engine ratings (e.g., P rating, rated
engine speed), number of cylinders, fuel type, engine operating conditions (e.g., engine
speed, engine airflow, and engine temperature), environmental conditions, and/or system
aging.
[0061] Once the operating conditions are determined, routine 600 proceeds to 616
where desired alternator torque is determined. As described above, the desired level of
alternator torque may be based on the engine speed, battery voltage, and number of
cylinders. In one example, the routine may utilize a desired engine speed trajectoryduring cranking and run-up, and based on an error between the desired trajectory and the
actual engine speed trajectory, a desired torque may be evaluated.
[0062] At 618 of routine 600, engine cranking is performed with continuous field
shunting, as described above, and electrical energy storage device 108. In some
examples, both the boosted battery 104 and the electrical energy storage device 108 may
be used to crank the engine. For example, switching circuit 138 may be controlled based
on a threshold level of charge of the electrical energy storage device. The threshold level
may be close to a maximum charge of the electrical energy storage device 108. In other
examples, the threshold level of charge may be additionally or alternatively based on an
amount of energy needed to start the engine, for example. If the level of charge of the
electrical energy storage device is above the threshold level, the switching circuit may be
adjusted such the battery 104 is not electrically coupled to the electrical energy storage
device 108, and vice versa.
[0063] At 620 of routine 600, an engine speed check is performed. As an example,
if the engine speed has reached a predetermined speed, for example about 200 rpm, the
controller signals that the engine 112 has completed cranking and the alternator torque
supplied to the engine 112 is reduced. If the engine speed is below the predetermined
speed, then the engine cranking continues as explained at 618.
[0064] If it is determined that the engine speed is greater than the threshold speed at
620, routine 600 proceeds to 622 and the voltage supplied to the traction alternator 120
by the electrical energy storage device 108 is reduced. Further, the alternator torque may
not be generated, and the alternator may be switched to an idle or generating mode
depending on operating conditions of the off-highway vehicle.[0065] Once the voltage supplied to the traction alternator 120 is reduced or if it is
determined that a running mode of operation is desired at 610, routine 600 moves to 624
where switching circuit 116 is adjusted to disconnect electrical energy storage device 108
and the battery 104 (if connected to the electrical energy storage device 108) from the
active rectifier. For example, the switching circuit is opened such that the electric energy
storage device 108 and the active rectifier are no longer electrically coupled.
[0066] At 626 of routine 600, the battery 104 is charged by the engine via alternator
and rectifier 114. If it is not already connected, switching circuit 138 is adjusted (e.g.,
closed) to electrically connect the battery 104 to the electrical energy storage device 108
via the DC-to-DC converter 106. In this manner, the electrical energy storage device 108
is charged by the battery 104 during engine running operation.
[0067] At 630 of routine 600, it is determined if vehicle motion is desired. For
example, the vehicle operator may change a gear from Park to Drive. If it is determined
that vehicle motion is desired, routine 600 continues to 632 and the traction alternator
120 powers the traction motors 148 to turn the wheels 136 and propel the vehicle. On the
other hand, if it is determined that vehicle motion is not desired, the routine ends.
[0068] Thus, routine 600 shows an example flow chart illustrating a method for
operating an engine with voltage boosting and a secondary energy source (e.g., electrical
energy storage device 108). As explained above, the secondary energy source can be
used to power the traction alternator 120 to crank the engine during the engine starting
mode of operation. Further, the engine charges the battery 104 via the alternator 114, and
the battery 104, in turn, charges the secondary energy source.[0069] FIG. 7 shows another example embodiment of an engine system 700 that
includes a battery 104 (e.g., first energy source) that may be boosted with a DC-to-DC
converter 106 and an electrical energy storage device 108 (e.g., secondary energy source).
Engine system 700 is similar to engine system 500 described above with reference to FIG.
5, for example. The example illustrated in FIG. 7 further includes a switching circuit
electrically coupled between the active rectifier 134 and the electrical energy storage
device 108.
[0070] As depicted in FIG. 7, battery 104 is charged by the engine via alternator and
rectifier 114 by a first voltage when the engine is in a running mode of operation. During
the running mode of operation, the switching circuit 138 may be open or closed
depending on whether or not charging of the electrical energy storage device 108 via
battery 104 is desired. The electrical energy storage device 108 may be further charged
at a second, higher voltage by closing switching circuit 162. In such a configuration, AC
from the traction alternator 120 is converted to DC by active rectifier 134 and the DC is
allowed to flow to the electrical energy storage device 108 when the switching circuit 162
is closed, thus charging electrical energy storage device 108. Further, switching circuit
162 may include voltage limiting circuitry for charging electrical energy storage device
108. For example, switching circuit 161 may include a DC-to-DC converter. In this way,
a different voltage may be applied to electrical energy storage device 108 as compared to
the traction alternator 120, for example.
[0071] Thus, FIG. 7 shows an embodiment of an engine system which has a
secondary energy source (e.g., electrical energy storage device 108) in addition to a first
energy source (e.g., electric storage battery 104). As described above, both the firstenergy source and the secondary energy source may be charged via the engine 112 when
the engine is in a running mode of operation. Further, the secondary energy source may
be charged via the traction alternator 120 when the engine is in a running mode of
operation.
[0072] FIG. 8 shows a flow chart illustrating a control routine 800 for an engine
system which includes a secondary storage device which may be charged via a traction
alternator, such as engine system 100 of FIG. 5 . Specifically, the routine 600 determines
an operating mode of the engine and adjusts the circuitry accordingly.
[0073] At 810 of FIG. 8, it is determined if the engine is in a starting mode of
operation, such as a cranking mode, or a running mode of operation, such as a travelling
mode in which the vehicle is propelled. For example, the engine may already be running
or it may be shut down. If it is determined that the engine is in a starting mode of
operation, routine 800 proceeds to 812 where switching circuit 116 is adjusted to connect
electrical energy storage device 108 and battery 104 to active rectifier 134. For example,
switching circuit 116 may be closed in order to electrically connect the active rectifier
134 and the electrical energy storage device 108. At 814 of routine 800, switching circuit
162 is adjusted to disconnect the electrical energy storage device 108 from the traction
alternator 120. For example, switching circuit may be opened in order to electrically
disconnect the traction alternator 120 and the electrical energy storage device 108.
[0074] Once the switching circuits 116 and 162 are adjusted, routine 800 continues
to 816 where operating conditions are determined. As described above, the operating
conditions may include one or more of the following, for example: battery system
conditions (voltage, current load, temperature), alternator characteristics, engine ratings(e.g., HP rating, rated engine speed), number of cylinders, fuel type, engine operating
conditions (e.g., engine speed, engine airflow, and engine temperature), environmental
conditions, and/or system aging.
[0075] Once the operating conditions are determined, routine 800 proceeds to 818
where desired alternator torque is determined. As described above, the desired level of
alternator torque may be based on the engine speed, battery voltage, and number of
cylinders. In one example, the routine may utilize a desired engine speed trajectory
during cranking and run-up, and based on an error between the desired trajectory and the
actual engine speed trajectory, a desired torque may be evaluated.
[0076] At 820 of routine 800, engine cranking is performed with continuous field
shunting, as described above, and electrical energy storage device 108. In some
examples, both the boosted battery 104 and the electrical energy storage device 108 may
be used to crank the engine. For example, switching circuit 138 may be controlled based
on a threshold level of charge of the electrical energy storage device. The threshold level
may be close to a maximum charge of the electrical energy storage device 108. In other
examples, the threshold level of charge may be additionally or alternatively based on an
amount of energy needed to start the engine, for example. If the level of charge of the
electrical energy storage device is above the threshold level, the switching circuit may be
adjusted such the battery 104 is not electrically coupled to the electrical energy storage
device 108, and vice versa.
[0077] At 822 of routine 800, an engine speed check is performed. As an example,
if the engine speed has reached a predetermined speed, for example about 200 rpm, the
controller signals that the engine 112 has completed cranking and the alternator torquesupplied to the engine 112 is reduced. If the engine speed is below the predetermined
speed, then the engine cranking continues as explained at 820.
[0078] If it is determined that the engine speed is greater than the threshold speed at
822, routine 800 proceeds to 824 and the voltage supplied to the traction alternator 120
by the electrical energy storage device 108 is reduced. Further, the alternator torque may
not be generated, and the alternator may be switched to an idle or generating mode
depending on operating conditions of the off-highway vehicle.
[0079] Once the voltage supplied to the traction alternator 120 is reduced or if it is
determined that a running mode of operation is desired at 810, routine 800 moves to 826
where switching circuit 116 is adjusted to disconnect electrical energy storage device 108
and the battery 104 (if connected to the electrical energy storage device 108) from the
active rectifier. For example, the switching circuit is opened such that the electric energy
storage device 108 and the active rectifier 134 are no longer electrically coupled.
[0080] At 828 of routine 800, the battery 104 is charged by the engine via alternator
and rectifier 114. At 830 of routine 800, switching circuit 162 is adjusted (e.g., closed) to
connect the electrical energy storage device 108 to the traction alternator 120. As such,
the electrical energy storage device 108 is charged by the traction alternator 120 at 832 of
routine 800. In some examples, switching circuit 138 may be adjusted (e.g., closed) to
electrically connect the battery 104 to the electrical energy storage device 108 via the
DC-to-DC converter 106 such that the electrical energy storage device 108 is charged by
both the battery 104 and the traction alternator 120 during engine running operation.
[0081] At 834 of routine 800, it is determined if vehicle motion is desired. For
example, the vehicle operator may change a gear from Park to Drive. If it is determinedthat vehicle motion is desired, routine 800 continues to 836 and the traction alternator
120 powers the traction motors 148 to turn the wheels 136 and propel the vehicle. On the
other hand, if it is determined that vehicle motion is not desired, the routine ends.
[0082] Thus, routine 800 shows an example flow chart illustrating a method for
operating an engine with voltage boosting and a secondary energy source (e.g., electrical
energy storage device 108) which is charged by the traction alternator 120. As explained
above, the secondary energy source can be used to power the traction alternator 120 to
crank the engine during the engine starting mode of operation. Further, the engine
charges the battery 104 via the alternator 114, and the battery 104 may also charge the
secondary energy source.
[0083] FIG. 9 shows another example embodiment of an engine system 900 that
includes a battery 104 (e.g., first energy source) that may be boosted with a DC-to-DC
converter 106 and an electrical energy storage device 108 (e.g., secondary energy source)
which may be charged via a traction alternator 120. Engine system 900 is similar to
engine system 700 described above with reference to FIG. 7, for example. The example
illustrated in FIG. 9 further includes a hydraulic system which includes a hydraulic pump
180, a hydraulic accumulator 182, and an actuator 190. The hydraulic system may
control lifting of a loading arm 192 of the off-highway vehicle 10, for example.
[0084] As shown in the example illustrated in FIG. 9, the hydraulic pump 180 is
mechanically coupled to the engine 112 via a clutch 194 and mechanically coupled to the
alternator and rectifier 114 via a clutch 196. During an engine running mode of operation,
for example, clutch 194 between the engine 112 and hydraulic pump 180 is engaged such
that the hydraulic pump 180 is powered by the engine, and clutch 198 between the engine112 and the alternator and rectifier 114 may be engaged so that the engine supplies
energy to charge the battery 104. During an engine starting mode of the engine, clutch
194 may be disengaged, clutch 198 may be disengaged, and clutch 196 between the
hydraulic pump 180 and alternator and rectifier 114 may be engaged such that energy
from the hydraulic system may be used to charge the battery 104. For example, when
clutch 196 is engaged, a valve may be opened to release hydraulic oil from the hydraulic
accumulator 182 back to the hydraulic pump 180. The high pressure hydraulic oil from
the hydraulic accumulator 182 may cause hydraulic pump 180 to rotate thereby
generating a current in alternator and rectifier 114 which is sent to the battery 104.
[0085] Alternatively, a hydraulic pump 184 and hydraulic accumulator 186 may be
mechanically coupled to traction alternator 120. In such a configuration, traction
alternator 120 provides power to control the hydraulic system to actuate the loading arm
192 via actuator 190. Further a clutch 188 may be provided between the engine 112 and
the traction alternator 120 such that in a starting mode of operating, before engine
cranking begins, the traction alternator 120 can be decoupled from the engine and energy
from the hydraulic system may be supplied to the electrical energy storage device 108
when switching circuit 162 is closed. The engine is then started by supplying energy
from electrical energy storage device 108 to active rectifier 134 and traction alternator
120.
[0086] Thus, FIG. 9 shows an embodiment of an engine system which has a
secondary energy source (e.g., electrical energy storage device 108) in addition to a first
energy source (e.g., electric storage battery 104) as well as a hydraulic system for
controlling at loading arm 192 of the off-highway vehicle 10. As described above, inaddition to controlling the loading arm 192, the hydraulic system may be used to charge
the first energy source and/or the secondary energy source based on the location of the
hydraulic system.
[0087] FIG. 10 shows a flow chart illustrating a control routine 1000 for an engine
system which includes a secondary storage device and a hydraulic system, such as engine
system 900 of FIG. 9 . Specifically, the routine 1000 determines an operating mode of the
engine and adjusts the circuitry accordingly.
[0088] At 1010 of routine 1000, it is determined if the engine is in a starting mode of
operation, such as a cranking mode, a running mode of operation, such as a travelling
mode in which the vehicle is propelled, or a working mode of operation, such as when a
loading arm is in use. For example, the engine may already be running or it may be shut
down. The engine may be in the working mode and the running mode simultaneously.
For example, the engine may be running in an idle state while the loading arm is moving
so that the hydraulic system has power but the vehicle is not propelled.
[0089] If it is determined that the engine is in the starting mode of operation, routine
1000 proceeds to 1012 where clutch 194 is disengaged. In this way, the hydraulic system
is no longer mechanically coupled to the engine 112. At 1014 of routine 1000, clutch 198
is disengaged so that the alternator and rectifier 114 is no longer mechanically coupled to
the engine 112. At 1016 of routine 1000, clutch 196 is engaged. In this way, the
hydraulic system is mechanically coupled to the alternator and rectifier 114. As such,
energy from the hydraulic pump 180 can be used to generate a current in the alternator
and rectifier 114. In the embodiment in which the hydraulic system is coupled to the
traction alternator 120, clutch 188 may be disengaged such that the traction alternator isno longer mechanically coupled to the engine, and hydraulic pump 184 may generate
power in the traction alternator 120.
[0090] At 1018 of routine 1000, switching circuit 138 is closed such that battery 104
is electrically coupled to electrical energy storage device 108 and battery 104 may charge
electrical energy storage device 108 via DC-to-DC converter 106. In the embodiment in
which the hydraulic system is coupled to traction alternator 120, switching circuit 162
may be closed such that the traction alternator 120 is electrically coupled to the electrical
energy storage device 108. Switching circuit 162 may contain voltage control circuitry
(e.g., a DC-to-DC converter) so that electrical energy storage device 108 can be charged
at a different voltage than an output voltage from traction alternator 120, for example.
[0091] At 1020 of routine 1000, battery 104 is charged by the hydraulic system, and
because switching circuit 138 is closed, the electrical energy storage device 108 may also
be charged. As described above, the current generated in the alternator and rectifier 114
is directed to the battery 104. In this manner, battery 104 and electrical energy storage
device are charged. In the embodiment in which the hydraulic system is coupled to the
traction alternator 120, current generated in the traction alternator 120 is directed to the
electrical energy storage device 108 when the switching circuit 162 is closed. In this way,
the electrical energy storage device 108 is charged.
[0092] At 1022 of routine 1000, it is determined if a level of charge of the electrical
energy storage device 108 is greater than a threshold level of charge. The threshold level
of charge may be an amount of charge needed to supply an appropriate torque to crank
the engine, for example. If it is determined that the level of charge is less than thethreshold level, routine 1000 returns to 1020 and the hydraulic system continues to
charge the energy source.
[0093] On the other hand, if it is determined that the level of charge is greater than
the threshold level, routine 1000 continues to 1024 and routine 800 of FIG. 8 is carried
out from 812 to 824, as described above. In this way, the circuitry is adjusted such that
the engine may be started by the traction alternator 120, as described above with
reference to FIG. 8 . In the embodiment in which the hydraulic system is coupled to the
traction alternator 120, clutch 188 is engaged once the level of charge of the electrical
energy storage device 108 reaches the threshold level of charge so that the traction
alternator 120 may crank the engine at 1022.
[0094] Once the engine is started, or if it is determined that the engine is in the
running mode of operation at 1010, routine 1000 continues to 1026 where clutch 196 is
disengaged such that the hydraulic pump 180 is not longer mechanically coupled to the
alternator and rectifier 114. At 1028 of routine 1000, clutch 194 is engaged. In this way,
the engine 112 is mechanically coupled to the hydraulic system such that it may power
the hydraulic system. At 1030 of routine 1000, clutch 198 is engaged such that the
engine 112 is mechanically coupled to the alternator and rectifier 114 and the engine
provides energy to charge the battery 104.
[0095] At 1032 of routine 1000, routine 800 of FIG. 8 is carried out from 826 to 836,
as described above. In this way, the circuitry is adjusted such that the engine is running
and the electrical energy storage device 108 is charged by the traction alternator 120 and
battery 104 is charged by the alternator and rectifier 114, as described above with
reference to FIG. 8 .[0096] At 1034 of routine 1000, it is determined if loading arm 192 movement is
desired. In some examples, the loading arm may be controlled by an operator of the off-
highway vehicle, for example. In one example, the off-highway vehicle may be in a Park
gear so that the vehicle is not propelled while the loading arm 192 is moving. If it is
determined that loading arm 192 movement is not desired, routine 1000 ends.
[0097] On the other hand, if loading arm 192 movement is desired or if it is
determined that the engine is in a working mode of operation, routine 1000 moves to
1036 where clutch 196 is disengaged so that the hydraulic system is not coupled to the
alternator and rectifier 114. At 1038 of routine 1000, clutch 194 is engaged to
mechanically couple the engine 112 and the hydraulic pump 180 such that the engine 112
can provide power to the hydraulic system. At 1040 of routine 1000, clutch 198 may be
engaged to mechanically couple the engine 112 to alternator and rectifier 114 if charging
of the battery 104 is desired. For example, it may be desired to charge the battery 104 in
the working mode of operation if a level of charge of the battery 104 is less than a
threshold level.
[0098] At 1042 of routine 1000, movement of the loading arm 192 is controlled via
the actuator 190. For example, based on a desired motion of the loading arm 192,
actuator 190 is adjusted via the hydraulic pump 180 and the hydraulic accumulator 182 to
move the loading arm 192.
[0099] Thus, routine 1000 shows an example flow chart illustrating a method for
operating an engine with voltage boosting, a secondary energy source (e.g., electrical
energy storage device 108) which is charged by the traction alternator 120, and ahydraulic system. As explained above, the hydraulic system can be used to charge the
battery and the secondary energy source during the engine starting mode of operation.
[00100] FIG. 11 shows a flow chart illustrating a control routine 1100 for shutting
down an engine system, such as any of the engine systems described above with
reference to FIGS. 1-3, 5, 7, and 9 . Specifically, the routine 1100 determines if an engine
shut down is desired and controls the shut down based on conditions of the energy
storage devices.
[00101] At 1110 of FIG. 11, is it determined if an engine shut down is desired. For
example, it may be indicated that an engine shut down is desired if the vehicle operator
turns the key to an off position in the ignition. If it is determined that an engine shut
down is not desired, routine 1100 moves to 1118 and current engine operation is
continued and the routine ends.
[00102] On the other hand, if it is determined that engine shut down is desired,
routine 1100 proceeds to 1112 where it is determined if an estimated time of engine shut
down is greater than a threshold time. For example, the vehicle operator may have the
option to turn the key to various positions based on an estimated time of shut down. In
some examples, the threshold time may be a predetermined time, such as 24 hours. In
other examples, the threshold time may be based on a state of health of the battery. For
example, if the battery is degraded and is losing charge relatively quickly, for example,
the threshold time may be less than a situation in which the battery is not degraded.
[00103] If it is determined that the estimated time of shut down is greater than the
threshold time, routine 1100 continues to 1114 and the electrical energy storage device108 (e.g., secondary energy source) is discharged. Once the energy source is discharged,
routine 1100 proceeds to 1116 and the engine is shut down.
[00104] In contrast, if it is determined that the estimated time of shut down is less
than the threshold time at 1112, routine 1100 moves to 1120 where it is determined if the
charge level of the energy source is greater than a threshold level. For example, the
threshold charge level may be based on an amount of energy needed to crank the engine.
[00105] If it is determined that the level of charge is greater than the threshold level,
routine 1100 continues to 1122 and the electrical energy storage device 108 is left in the
ready to start state (e.g., the energy source is not discharged). Next, routine 1100 moves
to 1116 and the engine is shut down. In this way, a charge level of the electrical energy
storage device 108 is substantially maintained and the electrical energy storage device
108 will be ready to crank the engine during a subsequent start of the engine.
[00106] On the other hand, if it is determined that the charge level of the electrical
energy storage device 108 is less than the threshold level, routine 1100 moves to 1124
and the vehicle operator is notified that the engine should not be shut down. For example,
an indicator may be displayed on a dashboard of the vehicle which notifies the vehicle
operator of the low state of charge.
[00107] In examples where the engine is shut down and the energy source is
discharged or the charge level of the energy source is less than the threshold level, the
vehicle operator may have to wait for a length of time corresponding to the time needed
for the battery 104 to charge the electrical energy storage device 108, for example. As an
example, the time for the battery 104 to charge the secondary storage device may be
similar to a pre-lube time in which a pump pressurizes an oil system of the engine (e.g.,10 seconds). As another example, if a charge level of the battery 104 is low during
engine starting, it may be charged via the hydraulic system, as described above with
reference to FIGS. 9 and 10.
[00108] In this manner, shut down of an engine may be controlled based on an
estimated length of time the vehicle will be shut down. Control of engine shut down may
further be based on a charge level of the secondary storage device (e.g., electrical energy
storage device 108).
[00109] This written description uses examples to disclose the invention, including
the best mode, and also to enable a person of ordinary skill in the relevant art to practice
the invention, including making and using any devices or systems and performing any
incorporated methods. The patentable scope of the invention is defined by the claims,
and may include other examples that occur to those of ordinary skill in the art. Such
other examples are intended to be within the scope of the claims if they have structural
elements that do not differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from the literal languages of
the claims.CLAIMS:
1. A method of operating an engine, the engine coupled to a traction alternator for
vehicle travelling and an auxiliary alternator, comprising:
in an off-highway vehicle running mode of operation, charging a battery at a first
voltage from the auxiliary alternator while supplying current from the traction alternator
to a traction motor to propel the vehicle; and
in a starting mode of operation, generating a second, higher voltage, from stored
energy, to drive the traction alternator to at least assist in starting the engine.
2 . The method of claim 1, wherein the stored energy is stored electrical energy at the
first voltage stored in the battery, and the second, higher voltage is generated through a
DC-to-DC converter.
3 . The method of claim 1, wherein the stored energy is stored electrical energy at the
second voltage stored in a secondary electrical energy storage device.
4 . The method of claim 1, wherein in the running mode of operation, current is
supplied by a traction inverter to the traction motor to propel the vehicle, and during the
starting mode of operation, current is supplied at the second voltage to the traction
inverter to drive the traction alternator.5 . A method of operating an engine, the engine coupled to a traction alternator for
vehicle travelling, comprising:
in an off-highway vehicle running mode of operation, supplying current from the
traction alternator to a traction motor to propel the vehicle; and
in a starting mode of operation, supplying stored energy from a first energy source
and a secondary energy source to the traction alternator to start the engine.
6 . The method of claim 5, wherein the first energy source is a battery that outputs a
lower voltage than the secondary energy source, and further comprising, during the
running mode of operation, charging the battery via an auxiliary alternator mechanically
coupled to the engine.
7 . The method of claim 5, wherein the traction alternator is a three-phase alternator.
8 . The method of claim 7, further comprising, during the starting mode of operation,
adjusting torque supplied to the engine by continuous adjustment of a field shunting of
the traction alternator.
9 . The method of claim 7, further comprising, during the starting mode of operation,
adjusting torque supplied to the engine by adjusting DC voltage supplied to an inverter
coupled to the traction alternator.10. The method of claim 5, wherein output supplied by the first energy source is
boosted via a DC-to-DC converter.
11. The method of claim 5, wherein current is supplied to the traction alternator from
the secondary energy source via a traction inverter, and wherein current supplied to the
traction motor from the traction alternator is supplied via the traction inverter.
12. The method of claim 5, wherein current is supplied to the traction alternator from
the secondary energy source via an active rectifier.
13. The method of claim 5, wherein current is supplied to the traction alternator from
the secondary energy source via an inverter that is separate from a traction inverter which
supplies current from the traction alternator to the traction motor.
14. The method of claim 5, wherein the engine is further coupled to a hydraulic
system including a hydraulic pump, hydraulic accumulator, and a hydraulic actuator.
15. The method of claim 14, further comprising, in a working mode of operation,
supplying power from the engine to the hydraulic system for lifting a working arm
mechanically coupled to the vehicle.
16. The method of claim 14, further comprising, in the starting mode of operation,
decoupling the hydraulic system from the engine via a clutch, and charging the firstenergy source by electrically coupling the hydraulic system to the first energy source via
an auxiliary alternator.
17. A method of operating an engine in an off-highway vehicle, the engine coupled to
a traction alternator and an auxiliary alternator, comprising:
in a running mode of operation, supplying a traction motor with current from the
traction alternator via a traction inverter, charging a first energy source via the auxiliary
alternator, and charging a secondary energy source via the traction alternator; and
in a starting mode of operation, directing output from the first energy source
through a DC-to-DC converter and to the secondary energy source before directing
output of the secondary energy source to the traction alternator to assist in cranking the
engine, the secondary energy source outputting a higher voltage than the secondary
energy source.
18. The method of claim 17, wherein the first energy source is a battery, and the
battery is coupled to the secondary energy source via a switching circuit.
19. The method of claim 18, further comprising, during the starting mode of operation,
adjusting the switching circuit to disconnect the battery from the secondary energy source
when a level of charge of the secondary energy source is greater than a threshold level.
20. The method of claim 17, wherein the traction alternator is electrically coupled to
the traction inverter via an active rectifier.21. The method of claim 17, further comprising, during the starting mode of operation,
supplying current to the first energy source via a hydraulic system electrically coupled to
the auxiliary alternator, the hydraulic system including a hydraulic pump, a hydraulic
accumulator, and a hydraulic actuator.
22. The method of claim 17, further comprising, during an engine shut down,
discharging the secondary energy source if an estimated time of engine shut down is
greater than a threshold, and not discharging the secondary energy source if the estimated
time of engine shut down is less than the threshold.
23. A system for an off-highway vehicle, comprising:
an engine;
an auxiliary alternator mechanically coupled to the engine;
a traction alternator mechanically coupled to the engine;
a battery electrically coupled to the engine;
a secondary energy storage system electrically coupled to the engine, the
secondary energy storage system outputting a higher voltage than the battery;
a hydraulic system which includes a hydraulic accumulator; and
a controller for operating the auxiliary alternator to charge the battery during a
running mode of operation; the controller operating the traction alternator to charge the
secondary energy storage system during the running mode of operation; the controller
operating the hydraulic accumulator to charge the battery during a working mode ofoperation; and the controller operating the battery and the secondary energy storage
system to supply current to the traction alternator to start the engine during a starting
mode of operation.
24. The system of claim 23, wherein the traction alternator is a three-phase alternator,
and wherein the controller adjusts torque supplied to the engine by continuous adjustment
of a field shunting of the traction alternator during the starting mode of operation.
25. The system of claim 23, wherein an output of the battery is boosted by a DC-to-
DC converter, and wherein the controller estimates a state of health of the battery.