SOUCIE, Wayne (9450 East Bowling Lane, Columbia, Missouri, 65201, US)
| CLAIMS: 1 . A clutch assist system for a vehicle, the vehicle having an fluid supply and a mechanical clutch system comprising a clutch pedal, a clutch arm, and a cable extending between the clutch pedal and the clutch arm, the clutch assist system comprising: a clutch pedal sensor; the clutch pedal sensor transmitting a signal indicative of the position of the clutch pedal or pressure exerted on the clutch pedal; a clutch assist actuator having connectable to the clutch arm to exert a force on the clutch arm; a controller electrically connected to the valve module and the pedal sensor; the controller configured to control the valve module in response to the signal received from the clutch pedal position sensor. 2. The clutch assist system of claim 1 wherein the clutch pedal sensor senses the amount of travel or angle of the clutch pedal as the clutch pedal is pressed. 3. The clutch assist system of claim 1 wherein the clutch pedal sensor is a pressure sensor. 4. The clutch assist system of claim 1 wherein the clutch assist system further includes a valve module having an inlet in fluid communication with the fluid supply and an outlet in fluid communication with the clutch assist actuator via a supply hose; the valve module comprising a supply valve controlled by said controller. 5. The clutch assist system of claim 4 wherein the valve module further comprises a release valve; said release valve having an inlet in communication with said piston device and an outlet to exhaust fluid from the piston device, each said valve being individually controlled by said controller. 6. The clutch assist system of claim 5 wherein the valves are proportional valves. 7. The clutch assist system of claim 4 further comprising a pressure sensor; said pressure sensor being in fluid communication with the clutch assist actuator to sense the pressure within the clutch assist actuator; said pressure sensor generating an output indicative of the pressure within the clutch assist actuator; said controller being operatively connected to said pressure sensor to receive the output from the pressure sensor; said pressure sensor comprising a feedback loop; said controller being adapted and configured to control the control valve module in response to the output of the pressure sensor in addition to the output of the pedal sensor. 8. The clutch assist system of claim 1 wherein the clutch assist actuator is connected to the clutch arm to exert a force on the clutch arm in the same direction as the force exerted on the clutch arm by the clutch cable. 9. The clutch assist system of claim 1 wherein the clutch assist actuator is connected to the clutch arm to exert a force on the clutch arm in the opposite direction as the force exerted on the clutch arm by the clutch cable. 10. The clutch assist system of claim 1 wherein the pedal sensor output is non-linear. 1 1 . The clutch assist system of claim 1 wherein including a microcontroller, said micro-controller receiving the signal from said pedal sensor; said micro-controller containing software which a non-linear algorithm to said position sensor output. 12. The clutch assist system of claim 1 1 wherein said algorithm is chosen from the group consisting of a parabolic algorithm, an exponential algorithm, and a polynomial algorithm. 13. The clutch assist system of claim 1 1 including an input in communication with the micro-controller; the input enabling an operator to selectively alter the algorithm to change the shape of a curve defined by the algorithm. 14. The clutch assist system of claim 1 wherein the controller includes an OPamp circuit; said OPamp circuit and a voltage divider; said voltage divider being connected to an input of the OPamp circuit; said voltage divider being configured and adapted to enable selective adjustment of the output of the voltage divider to selectively alter the input to the OPamp circuit. 15. The clutch assist system of Claim 14 wherein the voltage divider comprises a variable resistor. 16. The clutch assist system of 16 wherein said voltage divider comprises a DIP switch block containing a desired number of DIP switches. 17. A method for reducing the mechanical force required to operate a clutch system of a vehicle, the clutch system having a clutch pedal and a clutch mechanism operated by depressing the clutch pedal; the method comprising: sensing a position of, or pressure applied to, the clutch pedal; and regulating a clutch assist actuator based on the sensed position of, or pressure applied to, the clutch pedal, the clutch assist actuator being operatively connected to the clutch mechanism to exert a force on the clutch mechanism to assist the operator in engaging the clutch mechanism. 18. The method of claim 17 wherein the clutch assist actuator is a fluid operated actuator; the method further comprising the step of sensing the pressure within the clutch assist actuator; the step of regulating the fluid flow to the clutch assist actuator further comprising regulating the fluid flow based on the sensed pressure within the clutch assist actuator. 19. The method of claim 17 wherein a valve module is positioned between a source of fluid and the clutch assist actuator; said step of regulating fluid flow to the clutch assist actuator comprising controlling the valve module. 20. The method of claim 19 wherein the valve module comprises a supply valve and a release valve; the supply valve having an inlet in communication with the fluid supply and an outlet in communication with the clutch assist actuator; the release valve having an inlet in communication with the clutch assist actuator and an outlet; the method comprising individually controlling said supply valve and release valve in response to the sensed position of, or pressure applied to, the clutch pedal. 21 . A clutch assist system for a vehicle, the vehicle having a fluid supply and a mechanical clutch system comprising a clutch pedal, a clutch arm, and a cable extending between the clutch pedal and the clutch arm, the clutch assist system comprising: a clutch pedal sensor; the clutch pedal sensor transmitting a signal indicative of the position of the clutch pedal or pressure applied to the clutch pedal; an clutch assist actuator connected to the clutch arm to exert a force on the clutch arm; a controller electrically connected to the valve module and the clutch pedal sensor; the controller configured to control the control valve module in response to the signal received from the clutch pedal sensor; and means for adjusting an assist ratio of said clutch assist system. 22. The clutch assist system of claim 21 wherein said assist ratio adjusting means comprises means for adjusting the signal of said pedal sensor prior to said valve module receiving said signal. 23. The clutch assist system of Claim 22 wherein said signal adjusting means comprises said pedal sensor; said pedal sensor being adapted to program the output signal of the pedal sensor to create a nonlinear response. 24. The clutch assist system of Claim 22 wherein assist ratio adjusting means comprises a micro-controller positioned between said pedal sensor and said valve module; said micro-controller receiving the signal from said pedal sensor; said micro-controller containing software to apply an algorithm to said pedal sensor output and including an input operable by an operator to selectively alter a constant of the algorithm. 25. The clutch assist system of claim 24 wherein said algorithm is a nonlinear algorithm chosen from the group consisting of a parabolic algorithm, an exponential algorithm, and a polynomial algorithm. 26. The clutch assist system of claim 21 wherein the controller includes an OPamp circuit and a voltage divider; said voltage divider being connected to an input of the OPamp circuit; said voltage divider being configured and adapted to enable selective adjustment of the output of the voltage divider to selectively alter the input to the OPamp circuit; said assist ratio adjusting means comprising means for altering the output of the voltage divider received by the OPamp circuit. 27. The clutch assist system of Claim 26 wherein said ratio adjusting means comprising the variable resistor. 28. The clutch assist system of 26 wherein said ratio adjusting means comprising said block of DIP switches. |
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the non-provisional application of, and claims priority to, US Provisional Application Number 61 /249,038, which entitled Electro/Pneumatic Clutch Assist, which was filed on October 6, 2009, and which is incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
This application relates to systems which reduce the effort required to engage the clutch of a motor vehicle, and, in particular to a clutch assist system for trucks.
Traditional clutch systems include a mechanical linkage which couples the clutch pedal located in the operator compartment to the clutch mechanism which, in turn, is coupled to the vehicle's transmission. Such linkages include a combination of one or more mechanical arms connected between the clutch pedal and to the clutch mechanism. An arm connected to the clutch pedal is connected to one of the arms on the clutch mechanism via a cable. Typical clutch mechanisms include a pressure plate which is spring-loaded to apply an engagement force on the clutch friction materials thereby transmitting torque for the engine to the drive train. The function of the clutch linkage system is to disengage the clutch to facilitate gear changes and disconnect the engine from the rest of the drive train. To disengage the clutch, the driver must push on the clutch pedal with sufficient force to overcome the spring force and any other resistance present in the clutch mechanism. In the case of trucks, the force that must be exerted by the driver to overcome the spring force may be significant. Under typical driving conditions, the driver must repetitively engage and disengage the clutch mechanism, leading to driver fatigue due to the significant force the driver must apply to the pedal.
Devices which supply forces in parallel to the force provided by the driver, lessening the force that must be provided by the driver, are known in the art. Such devices may provide a constant assist force or a force which varies based on the travel of the clutch pedal. An assistance where the force provided varies based on the travel of the clutch pedal is commonly referred to as the assist profile. These systems exhibit many disadvantages, including manufacturing and maintenance expense, components which wear out and require replacement and lack the ability to provide varying amounts of assistance without changing the system components. Additionally, known systems are not readily programmable or re-programmable, and are not readily adaptable to the user.
Accordingly, it would be desirable to provide a clutch assist system that allows the assist ratio and shape of the assist curve to be reprogrammed without changing the actuating mechanism, eliminates the need to manage nonfunctional air in or out of the system, and has an actuating mechanism which eliminates the need to run the cable through the actuator to provide a non-assist failsafe function.
BRIEF SUMMARY OF THE INVENTION
Briefly stated, a clutch assist system for a vehicle is provided which reduces the problem of operator fatigue and the great effort required by the operator to engage the vehicle clutch. Additionally, the clutch assist ratio for the clutch assist system can be selectively varied. Further, the clutch assist system can be installed in or retrofitted in most vehicles without much difficulty.
As is typical, the vehicle includes an fluid supply and a mechanical clutch system. The fluid supply can be an air (pneumatic) system or a liquid (hydraulic) system. The mechanical clutch system comprises a clutch pedal, a clutch arm, and a cable extending between the clutch pedal and the clutch arm. The clutch assist system comprises a clutch pedal sensor which outputs a signal indicative of the position of the clutch pedal or the pressure being applied by the operator to the clutch pedal. A control module is in operative communication with the position sensor and receives the signal from the clutch pedal sensor or a modified signal from the clutch pedal sensor. The control module controls a valve module in response to the signal from the clutch pedal sensor. The valve module has an inlet in fluid communication with the fluid supply of the vehicle and an outlet in fluid communication with a clutch assist actuator via a supply hose. The clutch assist actuator, in turn, is operatively connected to the clutch arm to exert a force on the clutch arm. The clutch assist actuator can be connected to the clutch arm to exert a force on the clutch arm in the same direction as the force exerted on the clutch arm by the clutch cable, or to exert a force on the clutch arm in the opposite direction as the force exerted on the clutch arm by the clutch cable.
The clutch pedal sensor can be a sensor which senses (or monitors) the amount of travel of the clutch pedal as the clutch pedal is pressed. For example, the sensor can monitor the angle of the clutch pedal. Alternatively, the sensor can be a pressure sensor, which is responsive to the spring pressure of a spring in the clutch pedal assembly. The output from the clutch pedal sensor is received by the control module to monitor either the position of the clutch pedal or the force applied to the clutch pedal by the driver. This signal or output from the clutch pedal sensor is thus used as the input to the control module to modulate the pressure in the clutch assist actuator.
The valve module can include a supply valve and a release valve. The supply valve has an inlet in fluid communication with the fluid supply and an outlet in communication with the clutch assist actuator to supply fluid to the clutch assist actuator. The release valve has an inlet in communication with the clutch assist actuator and an outlet to exhaust fluid from the piston device. In accordance with one aspect of the system, each valve is individually controlled by the control module. The valves can be proportional valves, in which case, the valves are opened and controlled by a proportional solenoid, the solenoid being controlled by the control module.
In accordance with another aspect of the system, the system can include a feedback loop to help modulate the pressure in the clutch assist actuator. This feedback loop includes pressure sensor which senses the pressure of the fluid in the clutch assist actuator and which outputs a signal indicative of the pressure within the clutch assist actuator. This signal is received by the control module, and the control module in turn uses the input from the pressure sensor as additional input (in addition to the input from the clutch pedal sensor) to control the valve module.
In accordance with another further aspect of the system, the assist ratio of the system can be either linear or non-linear. If non-linear, the assist ratio can define a parabolic, exponential or polynomial curve. In the case of a non-linear assist ratio, the output signal of the position sensor could be programmed to create a nonlinear response. Alternatively, a micro-controller could be positioned between the position sensor and the valve control module. The micro-controller would contain software which would apply a non-linear algorithm to the position sensor output. The micro- controller would then generate an output of the modified signal and the modified signal would be received by the valve control module.
In accordance with yet another aspect of the system, the assist ratio can be selectively adjusted. In the case of a non-linear assist ratio, wherein the system includes the above-noted micro-controller, the system can include an input device in communication with the micro-controller which would allow for adjustment of a constant of the algorithm applied by the micro-controller, to change the shape of a curve defined by the algorithm.
In the instance where the assist ratio is linear, the system can include an OPamp circuit which applies a gain to the position sensor output. The gain is defined by the equation G=a(1 +R2/R1 ) where a is a constant, and R1 and R2 are biasing resistors for the OPamp circuit. In this instance, the assist ratio is adjusted by adjusting or altering the ratio R2/R1 . This can be done by replacing the biasing resistors with a variable resistor. Alternatively, the OPamp circuit can be provided with a DIP switch block containing a desired number of DIP switches in combination with one of the biasing resistors. In the former case, the assist ratio is adjusted by altering the variable resistor. In the latter case, the assist ratio is altered by selectively opening and closing one or more of the DIP switches of the block of DIP switches. The use of the variable resistor provides a continuous adjustment, whereas the DIP switches allow for discrete assist ratios. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
Fig. 1 is a schematic view of a prior art mechanical clutch system;
FIG. 2 is a schematic view of a clutch assist system constructed in accordance with the present disclosure (with fluid lines shown as dotted lines, electrical lines shown as solid lines, and the clutch cable shown as a wide solid line);
FIG. 3 is an enlarged schematic view of the controller of the of the clutch assist system (with fluid lines shown as dotted lines and electrical lines shown as solid lines);
FIGS. 4A-B are two alternate electrical schematics of the circuitry of the clutch assist system;
FIG. 4A1 and 4A2 are schematics substantially similar to the schematic of FIG. 4A, but where a biasing resistors are replaced with a DIP switch bank and a variable resistor, respectively, to enable selective adjustment of the assist ratio produced by the assist system;
FIGS. 4C-D are electrical schematics of OPamp circuits used in the schematics of FIGS. 4A and 4B, respectively;
FIG. 5 is a enlarged schematic view of an air spring as used a clutch assist actuator in the clutch assist system; and
FIG. 6 is a schematic view of an alternate embodiment of the clutch assist system.
Corresponding reference numerals will be used throughout the several figures of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
The following detailed description illustrates the claimed invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what I presently believe is the best mode of carrying out the claimed invention. Additionally, it is to be understood that the claimed invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The claimed invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
Fig 1 illustrates a prior art mechanical clutch system 10. The clutch system
10 includes a clutch pedal 12 which is positioned within the cab of a vehicle near the driver's feet. The clutch pedal 12 is mounted such that when it is depressed, a pivot 16 causes a pedal arm 14 to rotate about the point where the pedal arm 14 is attached to the pivot 16.
The clutch system 1 0 also includes a clutch mechanism 28 which is connected to the pedal arm 14 by means of a cable 18. When in a disengaged state, the clutch mechanism provides a direct mechanical connection between the vehicle's drive shaft and transmission input shaft, so that the drive shaft and the transmission input shaft rotate at the same rate. When the clutch mechanism 28 is engaged by pressing on the clutch pedal 12, the transmission input shaft is decoupled from the engine drive shaft, allowing the drive shaft and the transmission input shaft to rotate at different rates and facilitating the selection of a different gear within the transmission. Once a new gear is selected, the clutch is disengaged by releasing the clutch pedal 12 and the drive shaft and the transmission input shaft are re-synchronized to rotate at the same rate. The construction of the clutch mechanism 28 is such that both the engagement and disengagement of the mechanism require a precise mechanical force to be applied to ensure proper synchronization between the drive shaft and the transmission input shaft.
The clutch mechanism 28 is selectively engaged and disengaged by a clutch arm 26, which is connected to a link arm 22 through a pivot 20. One end of the clutch cable 18 is mechanically connected to the link arm 22 while the opposite end of the clutch cable 18 is operatively connected to the pedal arm 14. In operation, when the driver of the vehicle applies pressure to the clutch pedal 12, the pedal arm 14 rotates about the point where the pedal arm is attached to the pivot 16, pulling on the clutch cable 18 which in turn pulls the link arm 22 and the clutch arm 26 (causing the link arm and clutch arm to pivot about a pivot point 24), thereby engaging the clutch mechanism 28. When the clutch pedal 12 is engaged, the transmission and engine drive shaft are decoupled, and the driver is able to select a new gear. Once a new gear has been selected, the driver releases pressure from the clutch pedal 12, allowing the clutch cable 18 to return to its initial position, which causes the link arm 22 and the clutch arm 26 to also return to their initial positions, disengaging the clutch mechanism 28.
Turning now to Fig. 2, a clutch assist system 30 is schematically shown. The clutch assist system 30 operates in parallel or in series with the mechanical clutch system 10, to reduce the pedal force required to engage and disengage the clutch mechanism 28. In the schematics, fluid lines are shown as dotted or dashed lines, electrical lines are shown as solid lines, and mechanical cables are shown as thick solid lines.
The clutch assist system 30 includes a control portion 32 and a clutch assist actuator 40 which is controlled by the control portion 32. The control portion 32 is in fluid communication with a control fluid system 34 of the vehicle and which is electrically connected to the vehicle's electrical supply 36. The control fluid system can be a pneumatic system or a hydraulic system. In the Figures, the control portion 32 is illustratively shown to be in communication with the vehicle's pneumatic system or air supply. The air supply of the pneumatic system 34 provides the control portion 32 with a source of unregulated compressed air, typically having a pressure of 550 - 689 kPa (approximately 80-1 00 pounds per square inch). The electrical supply 36 provides the controller 32 with electrical power typically between 5.5 and 24 VDC.
The control portion 32 is electrically connected to a pedal sensor 38. The pedal position sensor 38 is mounted relative to the pedal arm 14 such that the sensor 38 is able to sense the location of the pedal arm 14 or clutch pedal 12 as it is moved when the vehicle operator presses on, or releases, the clutch pedal 12. Alternatively, the pedal sensor 38 can sense the pressure exerted by the operator on the clutch pedal 12. The sensor 38 may provide an analog or digital output in various formats, as is well-known in the art. These formats include, but are not limited to, proportional analog voltages, pulse width modulation (PWM) or Digital.
The control portion 32 supplies pressure-regulated fluid to the clutch assist actuator 40 via a regulated supply hose 42 and monitors the fluid pressure present via return hose 44. Illustratively, the clutch assist system 30 is connected to the vehicle's pneumatic system. Hence, the clutch assist actuator is a pneumatic device, such as an air spring; and it is the air pressure that the control portion 32 monitors. Although the clutch assist actuator 40 is shown to be an air spring, a pneumatic piston could also be used. The control portion 32 is adapted to vent pressurized air from the air spring 40 through the air supply hose 42 into the atmosphere via a vent 46. Many components in mechanical control systems are suitable for water, oil, or gas applications. The distribution and control system described is intended to control pressure and or volume of material (i.e., water, fluid or gas) delivered to the clutch assist actuator 40. The type of fluid or gas delivered to provide assist is independent of the function. Thus, as noted above, although the clutch assist system is described as using a vehicle's pneumatic system, the clutch assist system could use alternatively a vehicle's hydraulic system.
The air spring 40 is adapted to produce translational motion of its piston arm 48 when pressure-regulated air is supplied to the air spring 40 through the regulated air supply hose 42. The piston arm 48 is connected to the link arm 22 via a pivot 20 in parallel or series with the clutch cable 18. In this arrangement, the clutch assist system 30 through the piston arm 48 and the mechanical clutch system 1 0 through the clutch cable 18 are both able to exert a mechanical force on the link arm 22, thereby selectively engaging and disengaging the clutch mechanism 28. This arrangement is advantageous since in the event of a failure of the clutch assist system 30, the mechanical clutch system 10 allows the continued, safe operation of the vehicle, simply without the force assist provided by the clutch assist system 30.
Turning to Fig. 3, the control portion 32 includes an input voltage regulator 50, a pedal position/pressure regulation integration circuit ("control circuit") 52, and a valve module 54, a pedal sensing circuit 56, and a pressure sensing (or feedback) circuit 58. The input voltage regulator 50 produces electrical signals having a constant voltage level from the electrical signals provided by electrical supply 36. Any suitable voltage regulator known in the art may be used. As shown in FIG 4A, the voltage regulator 50 produces a voltage level of 5VDC.
The control circuit 52 is electrically connected to the pedal sensing circuit 56, a pressure sensing circuit 58 and the valve control module 54. The pedal sensing circuit 56 receives and conditions the electrical signal produced by the pedal sensor 38, such that it is suitable for use by the control circuit 52. The pressure circuit 58 produces an electrical signal representative of the pressure in air spring 40.
The valve module 54 includes an supply control valve 60 and a release control valve 62, each of which are in communication with the supply hose 42. At least the supply control valve 60 is in fluid communication with the vehicle's source of control fluid (the vehicles air supply 34, as illustrated). The air supply 34 is in communication with the inlet to the supply control valve 60 and the supply hose 42 is in communication with the outlet for the control valve 60. The inlet of the release control valve 62 is in communication with the supply hose 42 and the outlet of the release control valve 62 is in communication with the atmosphere through a vent 46. If the assist fluid was hydraulic fluid, rather than pressurized air, the release control valve outlet would be in communication with a hydraulic fluid tank and the vent 46 would be replaced with a hose connecting the release control valve outlet to the hydraulic fluid tank. The control valves 60 and 62 can be proportional solenoid valves, in which case they would include proportional solenoids 61 (FIGS. 4A,B) which control the position of the valves to regulate the pressure and flow of fluid through the respective valve. Proportional solenoid valves (which are well known in the art) are preferred, but other types of valves could be used if desired. The proportional valves can be controlled by the controller 52 to control and/or modulate the fluid pressure delivered to the clutch assist actuator 40. By controlling the fluid pressure
Representative electrical schematics of the circuitry of the control portion 32 are shown in Figs. 4A and 4B. As seen in FIGS. 4A and 4B, the control circuit 52 and the pedal sensing circuit 56 is shown as a combined circuit. The control circuit 52/pedal sensing circuit 56 includes an OPamp circuit 53,53'. Representative circuitry for OPamp circuits 53,53' are shown in FIGS. 4C and 4D. The OPamp circuit 53 of FIG. 4C is used in the circuit of FIG. 4A; and the OPamp circuit 53' of FIG. 4D is used in the circuit of FIG. 4D. The circuitry of FIGS. 4A and B include biasing resistors 51 which set the input to the OPamp circuit 53,53', and thus the gain produced by the OPamp circuit. As one skilled in the art can appreciate, all or part of the analog circuitry shown in FIGS. 4A-D could be replaced by a suitably programmed microprocessor or micro-controller. The microprocessor or micro- controller would be programmed to provide the assist ratio and shape of the assist curve as described below.
Referring to Fig. 5, the clutch assist actuator (air spring) 40 receives air at a regulated pressure from the supply control valve 60 of the valve module 54 and through the air supply hose 42. The air enters the spring valve 40 at an air input port 64, flows through an air input tube 66 and fills an air bladder 68 to which a piston 70 is operatively connected. The piston arm 48, in turn, is operatively connected at one end to the piston 70. As described above, the piston arm 48 is operatively connected at its opposite end to the clutch mechanism 28. As seen in FIG. 5, the piston 70 is secured to a central point of the air bladder 68, such that when the piston 70 is in the retracted position, as seen in FIG. 5, the air bladder will be folded in on itself. As the pressure in the air bladder 68 increases, the air bladder 68 expands, the forcing piston 70 (and hence the piston arm 48) to displace or translate (from right to left with reference to Fig. 5), in turn displacing the piston arm 48, thereby moving the link arm and clutch arm and engaging the clutch mechanism 28. Disengagement of the clutch mechanism 28 is accomplished by stopping air flow through the input port 64 and allowing air to flow from the air bladder 68 and reducing pressure by opening the release control valve 62 to exhaust air through the supply tube 42 and out the vent 46. As the pressure in the air bladder 68 decreases, the air bladder 68 contracts, allowing the piston 70 to move toward its initial position (from left to right with reference to Fig. 5), which in turn moves the piston arm 48 toward its initial position, disengaging the clutch mechanism 28. As can be appreciated, when the air control valve 60 (which supplies air to the air spring 40) is opened, the release control valve 62 (which controls venting of the air spring) is closed, and vice versa.
In operation, to engage the clutch mechanism 28, the driver of the vehicle begins to apply force to the clutch pedal 12, causing the clutch cable 18 to pull on the link arm 22. Simultaneously, pedal sensor 38 will transmits a signal indicative of the position of the pedal arm 14 or pressure applied to the pedal 12 to the pedal position sensing circuit 56. The output of the pedal sensing circuit 56 is received by the controller 52. The control circuit 52 sends a signal, based on the signal from the pedal sensing circuit 56 (and hence from the pedal sensor 38) to the supply valve 60 allowing air to flow from the vehicle's air supply 34 and into the air input port 46 of the air spring 40 through the air supply hose 42. As the air bladder 68 begins to expand, the piston 70 begins to translate, causing the piston arm 48 to push on the link arm 22, thereby reducing the effort the driver must exert on the clutch pedal 12 to engage the clutch mechanism 28. Throughout this process, the control circuit 52 monitors the air pressure present at the air spring 40 through the air return hose 44 and the pressure sensing circuit 58. The control circuit 52 adjusts the position of supply valve 60 in response to the signals from the pedal position sensor 38 and the pressure sensing circuit 58 to achieve the desired pressure determined by the position of the clutch pedal 12. The return hose 44 and pressure sensing circuit 58 provide a feedback loop which is used by the controller 32 to help regulate the control valve 60, and thus the flow of air to the air spring 40. However, if desired, the pressure sensing circuit 58 and the return air hose 44 could be omitted.
When the control circuit 52 senses that the driver has driver has let up or released the clutch pedal 12 (based on the signals from the pedal sensor 38), the controller 32 reduces the air pressure in the air spring 40 by sending an electrical signal to the supply valve 60 to supply less air into the air supply hose 42 or sending an electrical signal to the release control valve 62 to vent air from the air spring 40 into the atmosphere through the vent 46. By precisely controlling the position of the proportional valves 60 and 62, the control circuit 52 is able to vary the amount of assist force provided based on the position of the clutch pedal 12 or pressure applied to the clutch pedal.
As can be appreciated by one skilled in the art, a variety of assist profiles can be produced by the control circuit 52. The assist profile refers to the amount of assist force provided by the system based on the amount of pedal travel. A "flat assist" is provided where a fixed assist force is provided whenever the clutch pedal is pressed to, for example, 50% or greater of its total travel. The assist force provided can also vary throughout the range of pedal travel, allowing independent control of the force required to engage the clutch mechanism or to reduce the force required to hold the clutch mechanism in an engaged position. This would be referred to as an assessed or changeable profile, as compared to the fixed or flat assist profile initially described. The control circuit 52 can also be configured or programmed to provide an increased assist force near the point at which the clutch engages, providing an increased feeling of control for the driver.
Device reprogramming or tailoring of the assist ratio can be accomplished several different ways depending upon the circuit alternatives utilized in the control board. The assist ratio can be either linear or non-linear. Adjusting the ratio of a linear assist curve changes the slope of the curve, whereas adjusting the ratio of a non-linear assist ratio changes the shape of the curve (which may be parabolic, exponential, polynomial, etc.)
The gain of the OPamp circuit is controlled via biasing resistors 51 (R1 and R2), with reference to FIGS. 4A and 4B. The biasing resistors 51 divide the voltage, to control the voltage which is received by the input of the OPamp. The OPamp circuit then applies a gain to the input voltage to produce an OPamp circuit output voltage. The output voltage is used to control the valves 60,62. Thus, the voltage supplied to the proportional solenoid valves can be reprogrammed by rebalancing the biasing resistors 51 to alter the voltage that is received by the OPamp circuit 53,53'. This rebalancing can be accomplished by incorporating DIP switch block 55 (FIG. 4A1 ) in combination with the resistor array as part of the OPamp circuitry of FIGS. 4C or 4D. Thus, for example, the biasing resistors can be replace with the DIP switch block 55. The use of DIP switches would provide for a plurality of set assist ratios. For example, two banks of 3 DIP switches, as shown in FIG. 4A1 would allow for 14 possible slopes, and thus fourteen possible assist ratios. As seen in FIG. 4A1 , the biasing resistor R1 is replaced with DIP switch resistors A, B and C, and biasing resistor R2 is replace with DIP switch resistors D, E and F. A switch is associated with each resistor A-F. The operator selects or adjusts the assist ratio by selecting one or more of the resistors A-B and one or more of the resistors D-F. Although the DIP switch block 55 has two banks of DIP switches, the DIP switch block 55 could be provided with a single bank of DIP switches. Alternatively, the rebalancing can be accomplished by using a variable resistor 55' (FIG. 4A2). In this instance, the biasing resistors 51 are be replaced with the variable resistor 55'.
For a non-linear assist ratio, the input into the OPamp must be non-linear. One method of providing a non-linear input to the OPamp would be to program the output signal of the pedal sensor 38 to create a nonlinear response. A second method would be to use a micro-controller to interpret the pedal sensor output and apply an nonlinear algorithm to tailor the system response to operator preferences. In this second method, the micro-controller would incorporate software, as is known, which would apply a output from the pedal sensor as input to non-linear algorithm or a non-linear table to produce a non-linear output. The algorithm, as noted above, could be a parabolic, exponential, polynomial, etc. algorithm. Further, the microcontroller could be provided with a user input device which would allow the shape of the curve defined by the algorithm to be altered.
A test was set up to simulate actuation of a linkage operating a spring pack to simulate a system operating against a clutch pressure plate. In the setup the linkage could be operated with or without assist turned on. In this concept demonstration, a pedal was adapted with a noncontact position sensor as the input to the control circuit with a proportional solenoid and an air cylinder to serve as the assist actuator. The control circuitry in the test was the circuitry of FIG. 4A. The assist was set up in parallel with the spring pack, to be analogous to the embodiment of FIG. 2. In this test, the force to apply the pedal with assist turned off was 23.9 lbs. In applications with the assist system turned on the apply force was 1 1 .4 lbs. Basically this configuration demonstrated that the clutch assist system can successfully provide controlled actuation assist.
An alternative embodiment of the clutch assist system 30' is shown in Figure 6. In this embodiment, the clutch cable 18 is connected to the piston arm 48, which remains operatively connected to the pivot 20. Hence, the clutch assist actuator 40 and the mechanical clutch system 1 0 are connected in series, rather than in parallel (as in FIG. 2). The clutch cable 18 and the piston arm 48 each exert a pulling force on the pivot 20, to engage and disengage clutch mechanism 28. In contrast, in the clutch assist system 30 (Fig. 2), the air spring 40 and cable 18 exert forces in opposite directions (that is, one pulls on the piston arm and the other pushes). In the event of a failure of the clutch assist system 30', the clutch cable 18 is still able to exert force on the piston arm 48 to engage and disengage the clutch mechanism 28. However, the driver must provide pedal force sufficient to overcome mechanical resistance naturally present in the air spring 40, in addition to the force required to operate the clutch mechanism 28.
In another alternative embodiment, the release valve 62 can be a simple on- off valve rather than a proportional valve. This results in a system which costs less to manufacture and maintain, but which also offers less control over the position of the piston 70 and therefore the amount of assist force being provided in parallel to the force provided by the driver's pedal effort. Additionally, the valves 60 and 62 could be replaced by a single three-way valve.
The goal of the assist system 30 is to convert/multiply a driver input to a mechanical output device. In the clutch assist implementation described above, the input is the clutch pedal 12 and the output is the clutch linkage 18. Using the pedal sensor 38 from an electronic accelerator pedal provides a correlation/reference voltage for pedal position/pressure to the assist circuitry or controller 52. That is, the pedal sensor 38 senses the amount of travel or angle of the clutch pedal as the clutch pedal is pressed. An alternate method of providing a reference signal would be via a pressure sensor like a pressure sensitive resistor. The pressure on the pedal is the result of the spring rate of the clutch pressure plate and mechanical linkage. In this control logic the control algorithm could modulate voltage to the proportional solenoids 61 to maintain a constant pedal effort (pressure sensor value) over the full pedal travel.
As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Although the system is described to utilize the vehicle's fluid (i.e., pneumatic or hydraulic) system, the clutch assist system could be configured to provide clutch assistance without relying on the vehicle's fluid system. In one possibility, the air spring 40 could be replaced with a solenoid, and the solenoid would be controlled by the controller 52. This would eliminate the need for the valve module 54. Another possibility is to utilize a stepper motor controlled by a DC servo controller or by pulse width modulation. In this variation, the valve module 54 would be replaced by the DC servo controller and the air spring would be replaced by the stepper motor. In these instances, the clutch assist actuator would be the solenoid or the stepper motor. These examples are merely illustrative.