Self-centering return mechanism

An auxiliary lean control system is provided for controlling a lean angle of at least a portion of a vehicle. The auxiliary lean control system includes an energy storage device for storing energy to actuate the lean control system, a stabilizing mechanism coupled to the energy storage device and to the at least a portion of the vehicle for applying energy received from the energy storage device to the at least a portion of the vehicle to adjust the lean angle of the at least a portion of a vehicle, and a linkage coupled to the energy storage device and to the stabilizing mechanism for transferring energy from the energy storage device to the stabilizing mechanism. The auxiliary lean control system controls the lean angle of the portion of the vehicle in an absence of control of the lean angle by a primary lean control system. In another aspect, the present invention provides a vehicle including a vehicle suspension apparatus and a vehicle lean control system coupled to the vehicle suspension apparatus for controlling a lean of at least a portion of the vehicle, the suspension apparatus being operable independent of the vehicle lean control system.

BACKGROUND

The present invention relates to vehicles with lean control systems. In particular, the present invention relates to vehicles with primary and auxiliary lean control systems coupled to a vehicle leaning suspension system for enhancing vehicle stability.

Certain types of vehicles are unstable (e.g., more prone to rolling over) in certain modes of operation. For example, a three-wheeled vehicle that permits roll axis articulation may be unstable when the vehicle center of gravity is located above the roll axis. Under normal operation, many such instabilities are compensated for by using a closed loop control system (for example, an electro-hydraulic or electro-mechanical system) including or coupled to elements of the vehicle systems (for example, elements of the vehicle suspension system) which are actuatable in response to a signal from a control unit. Based on feedback to the control unit from vehicle system elements and sensors, signals from the control unit actuate the responsive vehicle system elements to stabilize the configuration of the vehicle. For example, vehicle lean control systems may cause the body of the vehicle to lean into a turn, thereby increasing the stability of the vehicle during turning.

In hydraulically-actuated lean control systems, the lean control system may fail to function properly in the event of loss of hydraulic control (due to normal system shutdown, vehicle or hydraulic system power loss, hydraulic fluid leakage, etc.) In this instance, it is desirable that the vehicle is returned to and maintains an upright (no lean) configuration until hydraulic control can be restored. It is also desirable that the configuration of the vehicle, in the absence of hydraulic control, be as stable as possible.

SUMMARY

In accordance with the present invention, an auxiliary lean control system is provided for controlling a lean angle of at least a portion of a vehicle. The lean control system includes an energy storage device for storing energy to actuate the lean control system, a stabilizing mechanism coupled to the energy storage device and to the portion of the vehicle for applying energy received from the energy storage device to the portion of the vehicle to adjust the lean angle of the portion of a vehicle, and a linkage coupled to the energy storage device and to the stabilizing mechanism for transferring energy from the energy storage device to the stabilizing mechanism. The auxiliary lean control system controls the lean angle of the portion of the vehicle in an absence of control of the lean angle by a primary lean control system.

In another aspect, the present invention provides a vehicle including a vehicle suspension apparatus and a vehicle lean control system coupled to the vehicle suspension apparatus for controlling a lean of at least a portion of the vehicle, the suspension apparatus being operable independent of the vehicle lean control system.

DETAILED DESCRIPTION

FIGS. 1 and 2illustrate a three-wheeled motorcycle or trike10having an engine12, handlebars14, a frame16, a single rear wheel20, first and second front wheels22,24, and an auxiliary lean control system26. The rear wheel20is rotatably mounted to a rear portion of the frame16, and the front wheels22,24are coupled to the frame16via a leaning suspension system18. The frame16includes a front bulkhead40and a main bulkhead42defining the front portion of the frame16. The front bulkhead40is connected to the main bulkhead42to stiffen and strengthen the entire suspension system18. The engine12is coupled to the rear wheel20through a drive assembly (not shown) to propel the trike10. The handlebars14are pivotally coupled to the front portion of the frame16and coupled to the front wheels22,24through a steering system to controllably turn the front wheels22,24.

The illustrated embodiment is for a trike10having two steerable front wheels22,24and a single, driven rear wheel20. It should be noted that it is within the scope of the invention to employ the suspension system and lean control systems of the present invention in a vehicle having two rear wheels and a single front wheel. Also, in other embodiments, the suspension system and lean control systems can be used for the front wheels, the rear wheels, or both the front and rear wheels in a vehicle having four wheels, such as an ATV.

FIG. 3illustrates a front view of the trike10ofFIG. 1, showing the leaning suspension system18in an upright position. This position illustrates the orientation of the suspension system18while the trike10tracks a straight line on a flat surface.FIG. 4illustrates the front view of the trike10in a leaning configuration. This view shows how the suspension system18is oriented when the trike10is turning, or tracking an arcuate path. It should be noted that in order to highlight the different positions of the suspension system18betweenFIGS. 3 and 4, the handlebar14and wheel22,24positions are illustrated in the same center straightforward position for bothFIGS. 3 and 4. Although this position is correctly illustrated inFIG. 3the handlebar14position and the wheel22,24positions inFIG. 4should he pivoted and turned, respectively, toward or into the direction of the turn.

As used herein, the term “leaning suspension system” is defined as a suspension system that permits and/or facilitates leaning of a portion of the vehicle, wherein the leaning is initiated in response to forces exerted on the vehicle during turning of the vehicle by an active or passive lean control system installed in the vehicle.

FIGS. 5 and 6illustrate a perspective view and an exploded perspective view of the leaning suspension system18, respectively. The leaning suspension system18includes a transverse beam30, upper control arms32, lower control arms34, spring dampers36, and spindles44. The spindles44each include upper and lower pins102,100, as well as means for rotatably coupling to one of the front wheels22,24, such as a hole101for receiving a wheel axle103. The structure of the spindle44is well known to those skilled in the art.

The transverse beam30is rigid and remains substantially horizontal during operation of the trike10. The transverse beam30has a center pivot point60, end pivot points62, and intermediate pivot points64. In the embodiment shown inFIGS. 5 and 6, transverse beam30is pivotally coupled to a portion of the main bulkhead42at the center pivot60using a keyed shaft61(FIG. 9). However, other methods of coupling beam30to main bulkhead42are also contemplated. The center pivot60is positioned to coincide with a longitudinal centerline of the trike10and defines a pivot axis that is parallel to the vehicle centerline. The end pivot points62are pivotally coupled to upper pivots70on the spring dampers36.

The lower control arms34have trunnions80rotatably coupled to one end and adapted to rotatably receive the lower pin100on the spindles44. These trunnions80allow the suspension to operate independent of wheel steering by permitting the spindles44to pivot and turn regardless of the position of the lower control arms34. The two remaining ends of the lower control arms34include front and rear pivot points82,84that are pivotally connected to the main bulkhead42. Central pivot86is located centrally on the lower control arms34and is adapted to pivotally couple to lower pivot points72on the spring dampers36.

The upper control arms32also have trunnions80rotatably coupled to one end adapted to rotatably receive the upper pin102on the spindles44. These trunnions80allow the suspension to operate independent of wheel steering. The two remaining ends of the upper control arms32include front and rear pivot points90,92that are pivotally connected to the main bulkhead42.

In the illustrated embodiment, the transverse beam30is positioned between the front and rear pivots90,92on the upper control arms32. In other embodiments, the transverse beam30could be positioned in front of the front pivots90, behind the rear pivots92, or coupled to a different location than the upper control arms32(i.e. coupled to a different bulkhead).

As mentioned above, the spring dampers36include upper and lower pivot points70,72connecting the transverse beam30to the lower control arms34. The spring dampers36include a shock-absorbing member surrounded by a biasing member. This style of spring damper36is well known to those skilled in the art, and will not be discussed in further detail. Alternative embodiments may utilize a different method of biasing and shock absorbing, such as leaf springs, coil springs, or air springs.

A first or primary vehicle lean control system affects the attitude or orientation of vehicle bulkheads40and42with respect to the ground on which the vehicle rests. Referring again toFIG. 6, the primary lean control system includes hydraulic actuators38,39having upper and lower pivot points110,112. The illustrated embodiment shows the upper pivot points110of the hydraulic actuators38,39are pivotally coupled to the intermediate pivot points64on the transverse beam30at a location between the center pivot point60and one of the end pivot points62. Other embodiments could include the hydraulic actuators38,39pivotally coupled to the end pivot points62and the spring dampers36pivotally coupled to the transverse beam30at a location between the center pivot point60and one of the end pivot points62. The hydraulic actuators38,39and spring dampers can also be pivotally coupled to other points along the transverse beam30.

The hydraulic actuators38shown in the illustrated embodiment include a cylinder having top and bottom fluid ports114,116. A piston (not shown inFIG. 6) exists at the end of a shaft118within each cylinder. When hydraulic fluid is forced into the top fluid port114by a hydraulic pump (not shown), the internal piston is forced down, and the shaft118retracts. While this is happening, hydraulic fluid is being forced out of the bottom fluid port116and into a reservoir (not shown inFIG. 6). When hydraulic fluid is forced into the bottom fluid port116, the internal piston is forced up, and the shaft118extends. While this is happening, hydraulic fluid is being forced out of the top fluid port114and into the reservoir.

The steering system includes spindles44, tie rods46, and the steering box48. The handlebars14are coupled to the steering box48such that when an operator turns the handlebars14, an output shaft (not shown) on the steering box48rotates. The output shaft is pivotally coupled to a first end of each tie rod46. The second end of each tie rod46is pivotally coupled to one of the spindles44. As the output shaft on the steering box48rotates, the tie rods46follow, pulling one spindle44and pushing the other. The spindles44are rotatably coupled to the upper and lower control arms32,34by upper and lower pins102,100. Thus the pushing or pulling action initiated by the tie rods46causes the spindles44, and thus the front wheels22,24, to rotate about the upper and lower pins102,100.

The hydraulic actuators38,39act to control the orientation of the trike10during normal vehicle operation. When entering a turn, one of the hydraulic actuators38,39extends in length while the other retracts, moving the trike10into a leaning position as illustrated inFIG. 4. When the trike10is leaving the turn, the hydraulic actuators38,39act to bring the trike10back to a vertical orientation as illustrated inFIG. 3.

The hydraulic actuators are controlled by an electronic control system or unit (ECU) (shown inFIG. 13). The configuration of the electronic control unit is known in the art. In one embodiment, the electronic control unit comprises a programmable digital computer apparatus having a processor, ROM, RAM and I/O apparatus coupled to sensor elements (not shown) and actuatable elements of the vehicle, for receiving input signals and delivering output signals. The electronic control unit stores and runs a control program while the vehicle is in use. The sensor elements supply control-related data to the ECU. The ECU receives input signals from the vehicle sensors (for example, signals indicative of vehicle road speed, the steering angle of the trike handlebars, etc.) and delivers output control signals to the actuatable elements of the vehicle responsive to the input signals. Examples of ECU outputs include a current for energizing a solenoid used to actuate one or more of valves PCV1-PCV4, or a control signal resulting in the supply of desired currents to the solenoids. A typical control unit is described in U.S. Pat. No. 6,564,129, incorporated herein by reference.

The substantially horizontal orientation of the transverse beam30is maintained by the influence of the spring dampers36. The lower control arms34are connected to the front wheels22,24through the spindles44and to the transverse beam30by the spring dampers36. The front wheels22,24, and thus the lower control arms34, remain substantially parallel to the road during normal operation. The road is generally substantially planar for the width of the trike10, meaning that as long as both front wheels22,24are in contact with the road, whether cornering or tracking a straight line, the spring dampers36will bias the transverse beam30to an orientation substantially parallel to the road. The hydraulic actuators38,39connect the frame16to the transverse beam30, and control the lean of the trike10. As the hydraulic actuators38,39extend, they push the frame16away from the transverse beam30, initiating lean. The biasing force from the spring dampers36acting on the transverse beam creates a larger moment about the central pivot86than the hydraulic actuators38,39, so extension of the hydraulic actuators38,39moves the frame16with respect to the beam30.

Using hydraulic actuators38,39as discussed affords some major advantages to trikes. First, since the lean of the trike10is controlled by the hydraulic actuators38,39, the upper and lower control arms32,34, spring dampers36, and steering components are free to act normally, regardless of the trikes lean. This allows the trike10to absorb bumps while tracking an arcuate path in the same manner it would if it were tracking a straight line, making for a consistent suspension action, even while turning.

As stated previously, upon failure, deactivation, or malfunctioning of the primary lean control system, it is desirable that the vehicle is returned to and maintains an upright (no lean) configuration until hydraulic control can be restored. It is also desirable that this upright configuration of the vehicle, in the absence of hydraulic control, be as stable as possible.

Instability in the configuration of the vehicle may be characterized as a relatively greater amount of potential energy stored within the configuration of the vehicle system.FIG. 7is a graphical representation of a potential energy function describing the vehicle state during operation of the primary vehicle lean control system. InFIG. 7, the stability is expressed as a potential energy function of the vehicle system in a static case (i.e., when the vehicle velocity is zero), with a lower system potential energy reflecting a more stable orientation of the vehicle. InFIG. 7, the potential energy of the vehicle system is shown as a function of the lean angle of the vehicle provided by the vehicle lean control system. As seen inFIG. 7, the potential energy of the vehicle system is relatively lower at greater lean angles, due to a shift of the vehicle center of gravity to a position of lesser elevation. In contrast, a relatively less stable vehicle configuration is represented inFIG. 7by a relative maximum potential energy of the system, which occurs when the vehicle is in the upright or on-center position. At a lean angle of zero degrees (i.e., when the vehicle is in an upright position), the vehicle center of gravity is at its highest point, and the vehicle system potential energy is relatively high.

In view of the above, upon failure, malfunction, or deactivation of the primary lean control system, it is desirable to achieve a predetermined vehicle lean angle which is closest to an upright position of the vehicle and at which the vehicle system has a relatively low potential energy. In the present invention, this is accomplished by employing an auxiliary lean control system which brings the vehicle body to a desired, predetermined lean angle upon failure, malfunction, or deactivation of the primary lean control system. In general, the energy applied by the auxiliary lean control system to adjust the lean angle to a predetermined value necessary for maximum stability will depend on the difference between the current lean angle of the vehicle and the desired predetermined lean angle of the vehicle. The auxiliary lean control system stores a quantity of energy sufficient to return a portion of the vehicle to the desired predetermined lean angle for stability.

In a particular embodiment illustrating the principles of the present invention, it is desirable that the vehicle system have a relatively low potential energy when the vehicle is in an upright position (i.e., when the vehicle has a lean angle of approximately zero) and resting on a substantially flat surface.FIG. 8is a graphical representation of a potential energy function of an auxiliary lean control system in accordance with the present invention.FIG. 8illustrates the energy input into the vehicle system by the auxiliary lean control system to adjust the lean angle of a portion of the vehicle to approximately zero, as a function of the lean angle of the portion of the vehicle when the primary lean control system becomes inactive. As seen inFIG. 8, the potential energy input by the auxiliary lean control system is greatest at the largest vehicle lean angle shown because the greater the difference between the existing vehicle lean angle and the desired predetermined lean angle for vehicle stability (in this case zero degrees), the greater the energy that must be expended by the auxiliary system in returning the vehicle to the desired predetermined lean angle.

The force required to adjust the vehicle lean angle (or other vehicle orientation parameter) can be transmitted to the suspension system via any of a variety of known alternative means (for example, using a crank mechanism). The actual structure utilized will depend on the specifics of the application and the interface of the articulation system hydraulics.

FIG. 9is an exploded view of one embodiment of an auxiliary lean control system26in accordance with the present invention, coupled to transverse beam30. Auxiliary lean control system26generally includes an energy storage device for storing energy to actuate the lean control system, a stabilizing mechanism coupled to the energy storage device and to the leanable portion of the vehicle for applying energy received from the energy storage device to the leanable portion of the vehicle, and a linkage coupled to the energy storage device and to the stabilizing mechanism for transferring energy from the energy storage device to the stabilizing mechanism.

In the embodiment shown inFIG. 9, the energy storage device comprises a power cylinder132coupled to a portion of the main bulkhead42below the frame130, the linkage comprises a shaft134, and the stabilizing mechanism comprises a roller assembly136and a cam138. Referring toFIG. 9, a frame130is coupled to a portion of the main bulkhead42adjacent the transverse beam30and includes two parallel plates140extending vertically from a base142. The plates140are substantially identical, but one of the plates includes a clearance cut148to allow full rotation of an angle sensor150connected to the cam138. Both plates140define a central aperture144aligned with the center pivot point60of the transverse beam30and a guide slot146for the roller assembly136. The central aperture144defined by each plate140is adapted to rotatably support the keyed shaft61using a bushing152. The guide slot146extends vertically below the central aperture144, and provides a limiting path of travel for the roller assembly136.

The power cylinder132is coupled to a portion of the main bulkhead42below the frame130, and is coupled to the base142of the frame130. The power cylinder132includes a housing154, first and second cylinders156,158, a piston160movable inside the first cylinder156, and a cap162sealing the second cylinder158. The cylinders156,158are in fluid communication through an aperture (not shown) at the bottom of the cylinders156,158. The circumference of the piston160forms a seal with the inner wall of the first cylinder156. The volume of the first cylinder156above the piston160is in fluid communication with a hydraulic system200of the trike10, and the second cylinder158(and thus the volume of the first cylinder156below the piston160), is filled with a compressible fluid, such as a pressurized gas. Although the energy source for the embodiment of the auxiliary lean control system described herein comprises a compressible fluid, alternative energy sources are also contemplated, for example, a hydraulic sub-system or a spring system.

The shaft134is coupled to the piston160at a first end, and coupled to the roller assembly136at a second end, such that linear movement of the piston160along an axis defined by the first cylinder156will cause the roller assembly136to move in the same fashion.

The power cylinder132includes a hydraulic port164, a pressure sensor166, and a gas fitting168. The hydraulic port164allows the first cylinder156to be placed in fluid communication with the hydraulic system200of the trike10. The pressure sensor166allows the pressure in the first cylinder156to be monitored by the electronic control system. The gas fitting168allows the second cylinder158to be filled with the pressurized gas.

The roller assembly136includes three individual rollers174,176connected by a roller shaft170. A roller body172is coupled to the second end of the shaft134and is adapted to rotatably support the roller shaft170. The rollers174at the ends of the roller shaft170move within the guide slots146in the frame130. The center roller176is adapted to move toward the cam138when the piston160moves upward in the first cylinder156, and move away from the cam138when the piston160moves downward in the first cylinder156.

The cam138includes a central aperture178, a roller recess180, and two protruding lobes182. The keyed shaft61extends through the aperture178to support the cam138between the two parallel plates140of the frame130. The roller recess180is positioned between the protruding cam lobes182, and has a profile matching that of the center roller176. The lobes182are angularly offset from each other, and include substantially identical inner profiles adapted to engage the center roller176.

FIGS. 10 and 11are section views of the auxiliary lean control system26illustrating the trike10in a leaning position and an upright position, respectively. Since the transverse beam30and the cam138are both supported by the keyed shaft61, they will not rotate with respect to one another. As the trike10leans, the transverse beam30and the cam138remain substantially horizontal. From the perspective of the cam138, the rest of the trike10appears to rotate about the keyed shaft61. This is illustrated best inFIG. 10, where it is clear that when the trike10leans, the auxiliary lean control system26appears to rotate about the keyed shaft61.

When the primary lean control system is functioning properly, the pressure from the hydraulic fluid in the first cylinder156is greater than the pressure of the compressed gas in the second cylinder158. This forces the piston160downward, and disengages the roller assembly136from the cam138, placing the auxiliary lean control system26into an unengaged position (FIG. 10). When any of the above mentioned hydraulic system failures occur, pressure is also lost to the first cylinder156. This allows the compressed gas in the second cylinder158to expand and push the piston160up, placing the auxiliary lean control system26into an engaged position, where the roller assembly136is in contact with the cam138(FIG. 11). The pressure from the compressed gas is large enough that the center roller176pushes on the inner profile of one of the cam lobes182with enough force to drive the center roller176into the cam recess180, bringing the trike10to an upright position. As long as the hydraulic system is not pressurized, the pressure in the second cylinder158will be greater than the pressure in the first cylinder156. This will keep the center roller176engaged with the cam roller recess180and will prevent the trike10from leaning.

In the event that a failure occurs other than hydraulic system pressure loss, the electronic control unit controlling the hydraulic system200is capable of eliminating hydraulic fluid pumping, and thus hydraulic pressure. This also relieves the pressure in the first cylinder156, allowing the auxiliary lean control system26to function. When the hydraulic system is pressurized again, the pressure in the first cylinder156will again be greater than the pressure in the second cylinder158. This forces the piston160downward, disengaging the roller assembly136from the cam138and allowing the bike10to function normally.

The embodiment just described is adapted for bringing a portion of the trike to a lean angle of approximately zero degrees (corresponding to an upright position) when the trike resides on a substantially level road surface. In this case, piston160forces roller assembly136to rollingly engage the contoured surface of cam138until the roller assembly is centered along the contoured surface of the cam. The rollers become nested and locked within the grove formed in the cam surface when a lean angle of approximately zero degrees is achieved. Pressure applied by piston160holds the rollers in place, which locks the auxiliary lean control system in the zero-degree lean angle configuration and prevents the vehicle from leaning away from this position, thereby providing an upright vehicle configuration having a relatively low potential energy.

FIG. 12shows a resultant potential energy function derived by applying the energy stored in the second lean control system to bring the vehicle body to an upright configuration in which the lean angle to approximately zero (on a substantially level road surface), effectively combining the potential energy function shown inFIG. 7with the potential energy function shown inFIG. 8. In addition, when the vehicle body is brought to an upright position, the vehicle body is locked in the upright position by the auxiliary lean control system to prevent the vehicle body from leaning in either lateral direction while the first lean control system is non-functioning and while the second lean control system is engaged. It may be seen fromFIG. 3that the upright configuration of the vehicle with the leaning suspension system locked in a zero or near-zero lean angle configuration is a relatively stable configuration of the vehicle, since a non-zero vehicle lean angle may only be achieved by tilting or rolling the entire vehicle, thereby creating a vehicle configuration at a state of relatively higher potential energy than that provided by the upright, zero lean-angle configuration.

The shape of the auxiliary system potential function ofFIG. 8may be controlled by a combination of accumulator pressure and system mechanics (cam dimensions, etc.). The optimum shape of the function will be determined by factors such as the configuration of the vehicle upon deactivation or malfunction of the primary lean control system, and the desired final configuration of the vehicle. A potential function representing the final vehicle configuration (and combining the potential functions shown inFIGS. 7 and 8) is shown inFIG. 12. The shape of the combined function in any particular application will be determined by the desired final configuration of the vehicle.

FIG. 13is a schematic illustrating the hydraulic system200of the trike. The hydraulic system200includes a pump201, a filter202, four proportional control valves PCV1-PCV4, a centering valve204, a centering enable valve206, a pressure sensor208, a temperature sensor250, and a reservoir220.FIG. 10also shows that the hydraulic actuators38,39include top fluid chambers210,211and bottom fluid chambers212,213, respectively. These fluid chambers are defined by a movable piston214rigidly connected to a shaft216.

The pressurized hydraulic fluid supplied to the system200by the pump201passes through the filter202first to remove any contaminants. After passing through the filter202, hydraulic fluid is supplied to valves PCV1, PCV2, and centering valve204. Each of the valves PCV1-PCV4receives instructions to either open or close from electronic control unit217. Each of the valves may be closed or open individually to any degree, however, to simplify explanation, the valves PCV1-PCV4will be referred to as being either completely open or completely closed.

First, to cause the trike10to lean to the right, valves PCV1and PCV4are completely closed while PCV2and PCV3are completely open. This situation permits the pumping of fluid through PCV2and into hydraulic actuator chambers211and212. This will cause the left actuator38to extend in length while the right actuator39retracts. At the same time, fluid from hydraulic actuator chambers210and213is forced out of the hydraulic actuators38,39by the pistons214. The fluid exiting the chambers210,213is forced through open valve PCV3and to the reservoir220. In the second condition, causing the trike10to lean to the left, valves PCV2and PCV3are completely closed while PCV1and PCV4are completely open. This situation permits the pumping of fluid through PCV1and into hydraulic actuator chambers210and213. This will cause the right actuator39to extend in length while the left actuator38retracts. At the same time, fluid from hydraulic actuator chambers211and212is forced out of the hydraulic actuators38,39by the pistons214. The fluid exiting the chambers211,212is forced through open valve PCV4and to the reservoir220.

Referring to the auxiliary lean control system26, it is mechanically controlled, and is only operable when the trike10needs assistance maintaining an upright position (i.e., when the hydraulic system200is no longer able to supply enough pressure to properly utilize the hydraulic actuators38,39). Loss of hydraulic system pressure can occur in a number of different ways. When the trike10is parked and turned off, the hydraulic pump201is no longer applying pressure to the hydraulic system200, so the hydraulic actuators38,39will not be capable of supporting the trike10. If the hydraulic system200fails in any way (i.e. pump failure, ruptured hose, punctured hydraulic actuator, etc.), pressure will also be lost, even if the engine12is still running and the trike10is still operable. Yet another potential failure could occur if the electronic control system for the hydraulic actuators38,39malfunctions. It should be noted that this list of failure modes is not complete and can include other programmed faults, even unrelated to the hydraulic system. Regardless of how hydraulic pressure is lost, the auxiliary lean control system26will return the trike10to an upright and safe position.

As explained above, hydraulic fluid is supplied to the centering valve204. When the hydraulic system200is functioning properly, the centering valve204is open, allowing fluid to be pumped into the first cylinder156of the auxiliary lean control system26. The pressure from the hydraulic fluid in the first cylinder156is greater than the pressure of the compressed gas in the second cylinder158. This forces the piston160downward, and disengages the roller assembly136from the cam138, placing the auxiliary lean control system26into an unengaged position. When the pressure in the first cylinder156reaches a predetermined level measured by the pressure sensor166, the ECU217instructs the centering valve204to close. While the centering valve204is closed, pressure is maintained in the first cylinder156. This ensures that the auxiliary lean control system26will remain in the unengaged position, even if hydraulic system pressure fluctuates. However, if hydraulic system pressure falls to a predetermined level, the ECU217will instruct the centering valve204to open. This will bring the first cylinder156back into fluid communication with the hydraulic system200, and consequently allow the fluid contained in the first cylinder156to be forced back into the de-pressurized hydraulic system200due to the pressure from the compressed gas in the second cylinder. At the same time, the auxiliary lean control system26will to move to an engaged position, where the roller assembly136is engaged with the cam. The pressure from the compressed gas is large enough that the center roller176pushes on the inner profile of one of the cam lobes182with enough force to drive the center roller176into the cam recess180, bringing the trike10to an upright position. As long as the hydraulic system200is not re-pressurized, the pressure in the second cylinder158will be greater than the pressure in the first cylinder156. This will keep the roller assembly136engaged with the cam roller recess180and will prevent the trike10from leaning.

If a failure occurs other than hydraulic system pressure loss, the ECU217is capable of eliminating hydraulic fluid pumping, and thus hydraulic pressure. This also relieves the pressure in the first cylinder156, allowing the auxiliary lean control system26to function. When the hydraulic system200is pressurized again, the pressure in the first cylinder156will again be greater than the pressure in the second cylinder158. This forces the piston160downward, disengaging the roller assembly136from the cam138and allowing the trike10to function normally.

Referring toFIG. 13, a hydraulic system failure may occur in which hydraulic fluid is trapped between either hydraulic actuator chambers210and213, or between chambers211and212. This could occur if, for example, the ECU217malfunctions and doesn't allow valves PCV3or PCV4to open. If this occurs, the hydraulic actuators38,39may become locked in whatever their current state is, thereby possibly locking the trike in a leaning position. This would prevent the auxiliary lean control system26from operating, as the auxiliary lean control system would be incapable of exerting enough force to overcome the force exerted on the transverse beam30by the trapped hydraulic fluid. To remedy this situation, the centering enable valve206is opened when the centering valve204is opened. This allows hydraulic fluid to flow between any of the hydraulic actuator chambers210-213and prevents any hydraulic fluid from getting trapped between the hydraulic actuators38,39.

Unless otherwise noted, elements of the vehicle lean control systems described herein may be fabricated and interconnected using methods known in the art. It will also be understood that the foregoing descriptions of embodiments of the present invention are for illustrative purposes only. As such, the various structural and operational features herein disclosed are susceptible to a number of modifications commensurate with the abilities of one of ordinary skill in the art, none of which departs from the scope of the present invention as defined in the appended claims.