Patent Application
20080173033
The present invention relates to a vehicle compressor. It finds particular application in conjunction with controlling a speed of the vehicle compressor and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
Air brake and other auxiliary systems requiring compressed air are known for tractor/trailer vehicles. In conventional tractor/trailer vehicles, the basic air system components include an air compressor with a governor valve, an air dryer, a supply reservoir tank, valves for controlling flow of the compressed air to the brake and other auxiliary systems, wheel mounted brakes and brake chambers, and other auxiliary systems. In an air brake system, for example, the compressor furnishes the compressed air for brake operation by taking free atmospheric air and compressing it to 100-120 psi. The compressed air passes from the compressor into the reservoir where it is stored until it is needed. The compressed air is held in the reservoir until it is released by the operator via the air brake control valves. When the operator utilizes the air brake control valves, air flows to the brake chambers where its energy is transformed into the mechanical force and motion necessary to apply the brakes.
As the compressed air is used, the air supply systems require periodic recharging of the air supply reservoir. Under normal operating conditions the air compressor control system has a low limit pressure of about 100 psi and a high limit pressure of about 120 psi. When the pressure in the supply reservoir tank drops below about 100 psi, the system “loads” the air compressor and opens the governor valve. When the pressure in the supply reservoir tank reaches about 120 psi the system “unloads” the air compressor and closes the governor valve.
In conventional systems, the compressor is driven by the engine and runs continuously along with the engine. As discussed above, the compressor is either loaded or unloaded as a function of the pressure in the air supply reservoir. While loaded, the compressor supplies compressed air to the compressed air system. While unloaded, the compressor continues to run, but vents the air it produces to atmosphere, or a separate volume, instead of supplying the compressed air to the compressed air system. Running the air compressor continuously with the engine contributes to additional wear and tear on the compressor. In addition, the speed at which the compressor runs at any point in time is determined as a fixed ratio of the speed at which the engine is running.
The present invention provides a new and improved apparatus and method which addresses the above-referenced problems.
A vehicle air compressor controller includes a compressor electronic control unit receiving a plurality of signals representing respective vehicle parameters. A variable torque transmitter is controlled by the compressor electronic control unit. The variable torque transmitter receives an engine speed from an engine of the vehicle and delivers a variable torque to a compressor of the vehicle for controlling a speed of the compressor. The variable torque is determined as a function of the engine speed and the vehicle parameters.
In the accompanying drawings which are incorporated in and constitute a part of the specification, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below, serve to exemplify the embodiments of this invention.
With reference to
The compressor ECU 14 receives a plurality of signals representing respective vehicle parameters. Respective inputs 18 (e.g., electrical inputs) on the compressor ECU 14 act as means for providing the vehicle parameter signals to the compressor ECU 14. For example, in one embodiment, the compressor ECU 14 receives electronic signals representing a speed at which an associated engine 20 is driving the variable torque transmitter 16 (i.e., the driving speed), an actual speed at which the compressor 12 is reciprocating (i.e., the actual speed), and a pressure in an associated air tank 22 that is filled with compressed air produced by the compressor 12. The speed at which the associated engine 20 is driving the variable torque transmitter 16 is proportional to a compressor drive ratio. More specifically, the driving speed is calculated by multiplying the engine speed by a compressor drive ratio. Other vehicle parameters that may be used in the present invention include, for example, transmission retarder status, engine brake status, engine load status, vehicle speed, engine torque, engine oil temperature, engine start sequence, air suspension status, emission control devices, and/or other vehicle parameters defined in the SAE J1939 Data Link standard.
The variable torque transmitter 16 receives the engine speed from the associated engine 20. The compressor ECU 14 controls the variable torque transmitter 16 to deliver a variable torque to the compressor 12 for controlling the actual speed at which the compressor 12 reciprocates. More specifically, the compressor ECU 14 transmits a control signal (e.g., an electronic signal) to the variable torque transmitter 16 to manage a proportion of the driving speed that is transmitted to the compressor 12. In other words, the actual speed is a function of the driving speed (engine torque). The actual speed is also a function of the compressor drive ratio. In addition to being determined as a function of the driving speed, the actual speed is also determined as a function of the vehicle parameters.
In one embodiment, the variable torque transmitter 16 is a clutch. An amount of the clutch engagement determines the proportion of the driving speed that is transmitted to the compressor 12. The amount of clutch engagement is determined as a function of the engine speed and the vehicle parameters. In one embodiment, it is contemplated that the clutch is a slipping (wet) clutch, while in another embodiment the clutch is a dry clutch.
With reference to
A first supply valve 36 is controlled by the compressor ECU 14 for delivering a cooling fluid to the clutch housing 30 for reducing heat generated between the clutch plates 34. It is contemplated that the compressor ECU 14 transmits an electronic signal for controlling the first supply valve 36; however, other signals (e.g., pneumatic signals) are also contemplated. In the illustrated embodiment, the cooling fluid is oil supplied from the engine 20, which is also recycled to the engine 20. However, it is also contemplated that the cooling fluid may be a gas (e.g., air), oil from a source independent of the engine, or some liquid that is not oil.
It is to be understood that viscous forces are created in the clutch housing 30 when a cooling fluid such as engine oil is present. Such viscous forces may be advantageous to help drive the compressor 12 when the clutch plates 34 are engaged. In other words, the viscous forces help increase the torque delivered to the compressor 12. However, the same viscous forces may create a drag on the engine 20 when the clutch plates 34 are disengaged from each other. Therefore, it is contemplated that the cooling fluid be reduced or drained from the clutch housing 30 when the clutch plates 34 are disengaged from each other. In that regard, a drain means 40 is used for controlling the removal of the cooling fluid from the clutch housing 30.
In one embodiment, the drain means 40 is a valve, which is controlled by the compressor ECU 14, for controlling the level of the cooling fluid in the clutch housing 30. More specifically, the compressor ECU 14 transmits a signal (e.g., an electronic or pneumatic signal) for opening/closing the drain valve 40 as a function of whether the clutch plates 34 are engaged/disengaged from each other.
In another embodiment, the drain means 40 is an orifice, which is always open and, therefore, not controlled by the compressor ECU 14. The orifice is sized for causing the cooling fluid to slowly and constantly bleed from the clutch housing 30.
A second supply valve 42, which is also controlled by the compressor ECU 14, delivers a fluid to a control cylinder associated with the clutch piston 32. The engagement/disengagement between the clutch plates 34 is controlled as a function of the amount of fluid in the clutch piston 32. More specifically, if the amount of fluid in the control cylinder of the clutch piston 32 is below a threshold level, the clutch plates 34 are disengaged from each other. Once the amount of fluid in the control cylinder of the clutch piston 32 reaches a threshold level, the clutch plates 34 become engaged with each other. However, at the threshold level of fluid, a maximum amount of slippage between the clutch plates 34 exists. The amount of slippage between the clutch plates 34 decreases as the amount of fluid in the control cylinder of the clutch piston 32 is increased.
In the illustrated embodiment, the fluid is oil supplied from the engine 20. However, it is also contemplated that the fluid may be a gas (e.g., air), oil from a source independent of the engine, hydraulic fluid, or some other liquid.
During use, if the pressure in the air tank 22 drops below a cut-in pressure (e.g., 110 psi), the compressor ECU 14 determines more pressure is needed in the air tank 22. Therefore, the compressor ECU 14 signals the second supply valve 42 to open so that the fluid flows into the control cylinder associated with the clutch piston 32. Once the fluid flows into the control cylinder, the clutch plates 34 begin to engage each other. As discussed above, the level of engagement between the clutch plates 34 (e.g., slippage) is a function of the level of the fluid in the control cylinder. At the same time, if the plates 34 are slipping, the compressor ECU 14 signals the first supply valve to open so that the cooling fluid flows into the clutch housing 32. If the drain means 40 is a valve, the compressor ECU 14 also closes that valve 40 to increase the cooling fluid level in the clutch housing 30; otherwise, the cooling fluid slowly begins to bleed from the clutch housing 30 via the orifice.
Once the plates 34 are no longer slipping, the compressor ECU 14 causes the first supply valve 36 to close (and the drain valve 40 to open) so that the cooling fluid drains from the clutch housing 30.
In one example, if the engine 20 is idling at 700 rpm and the compressor drive ratio is 2.5:1, the driving speed is 1,750 rpm (i.e., 700 rpm×2.5). If the actual speed of the compressor is less than a predetermined target speed of the compressor (e.g., 2,500 rpm), the compressor ECU 14 signals the second supply valve 42 to increase the level of fluid in the control cylinder of the clutch piston 32 to increase the torque transmitted to driving the compressor 12.
The amount of fluid in the control cylinder of the clutch piston 32 is increased until the target compressor driven speed is reached. However, in this case, even if the maximum amount of fluid is introduced into the control cylinder so that the pressure between the clutch plates 34 is maximized, the target compressor driven speed cannot be achieved because driving speed is less than the target compressor driven speed. Therefore, once the maximum amount of fluid flows into the control cylinder, no slippage exists between the clutch plates 34. Consequently, the cooling fluid is reduced in the clutch housing 30. The clutch remains engaged in this manner until the pressure in the reservoir tank reaches a governed pressure (e.g., 130 psi), at which time the second supply valve 42 is closed.
Because the clutch is capable of slipping to limit the actual driven speed of the compressor 12, higher compressor drive ratios (and driving speeds) may be used. Consequently, the compressor duty cycle at relatively low engine speeds (e.g., idling) may be minimized.
In another example, if the engine 20 is running at a higher speed than described above (e.g., the engine 20 is running at 2,100 rpm), and the pressure in the air tank 22 is again below the cut-in pressure, the compressor ECU 14 signals the second supply valve 42 to increase the level of fluid in the control cylinder to increase the torque transmitted to driving the compressor 12. Since the engine speed is 2,100 rpm, the driving speed is 5,250 rpm (i.e., 2,100 rpm×2.5). It is assumed that the actual compressor driven speed is initially less than the driving speed. Therefore, the compressor ECU 14 signals the second supply valve 42 to continue providing the fluid to the control cylinder so that the clutch control pressure increases until the target compressor driven speed (e.g., 2,500 rpm) is achieved.
It is to be understood that the driving speed is a function of engine speed (motor speed). The driving speed could also be determined via a power take-off from, for example, a transmission.
Since the driving speed (5,250 rpm) is greater than the target compressor driven speed (2,500 rpm), slippage between the clutch plates 34 is required to maintain the target compressor speed (so that the compressor 12 does not run too fast). Therefore, the first supply valve 36 is opened to maximize cooling fluid in the clutch housing 30. Operation in this manner is maintained until the pressure in the air tank 22 reaches the governed pressure, at which time the first and second supply valves 36, 42 are closed and the fluid drains from the control cylinder.
In one embodiment, the variable coupling 58 illustrated in
In another embodiment, the variable coupling 58 illustrated in
While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.
