Extended compressor operation for auxiliary air supply

This patent disclosure relates generally to vehicle air systems and, more particularly to a compressor for supplying a primary vehicle air supply via a pump chamber and for supplying a secondary vehicle air supply via a secondary chamber associated with the pump chamber.

Large on-highway machines typically require pressurized air to operate properly. For example, the braking systems for such machines are typically air driven, using a source of pressurized air to drive a piston in a regulated maimer, providing the necessary force for braking the machine. The air driven systems, e.g., pistons, are often mechanically sensitive high tolerance devices, requiring that the pressurized air be essentially free of debris and contaminants. For this reason, the air delivery system for the machine may include an oil filter, desiccant filter, e.g., dryer, and/or other air cleaning device between the compressor and the air driven system.

Because the drag imposed by the compressor on the machine engine is related to the compressor size, it is typical to use a small compressor without significant additional capacity beyond that required by the braking system. Moreover, because of the packing requirements in and around the engine of such machines, a larger compressor is not suitable in most such machines.

However, there are increasingly other auxiliary machine systems, especially related to engine and emissions operations, that are air driven or that utilize pressurized air to perform a function. Because the main compressor of the machine is operating near capacity, it is not practical in most cases to bleed air from the main compressor to supply the auxiliary functions. Moreover, these functions often require clean air, and the compressor filter system may be located on the chassis, remote from the engine compartment.

There have been attempts to solve the problem of compressor capacity by using separate pumps. For example, U.S. Pat. No. 7,226,273 entitled “Method of Generating Compressed Air and Compressor Arrangement for Implementing the Method” describes a two-stage system for generating compressed air of sufficient flow rate and pressure for commercial vehicles. The system uses a compressor unit driven by an internal-combustion engine to generate low-pressure compressed air. The low-pressure compressed air is then used to generate higher-pressure compressed air via a separate auxiliary compressor unit. The compressor and auxiliary compressor unit are triggered based on the instantaneous pressure demand of the machine systems. However, the foregoing system is complex and cumbersome to operate, and requires an additional auxiliary compressor, thus complicating installation and maintenance as well.

This background section is presented as a convenience to the reader who may not be of skill in this art. However, it will be appreciated that this section is too brief to attempt to accurately and completely survey the prior art. The preceding background description is a simplified narrative and is not intended to replace the reference being discussed. Therefore, interested readers should refer directly to the U.S. Pat. No. 7,226,273 patent instead of relying upon the foregoing simplified narrative. Moreover, the resolution of deficiencies, noted or otherwise, of the prior art is not a critical or essential limitation of the disclosed principles.

In one aspect, the disclosure relates to a machine having a plurality of air-operated systems including at least one primary system and at least one secondary system. In this aspect, the machine comprises at least one air tank for containing a supply of compressed air for providing compressed air to the primary system and the secondary system. The machine includes a compressor for supplying compressed air to the air tank. The compressor is a reciprocating piston compressor having a primary air circuit including a compression chamber of the compressor and a secondary air circuit including a crankcase chamber of the compressor.

In a further aspect, the disclosure relates to a machine air supply system for providing compressed air to two or more air-operated features of a machine. In this aspect, the air supply system includes a primary air circuit for providing compressed air to one of the air-operated features of the machine and a secondary air circuit for providing compressed air to another of the air-operated features of the machine. In this aspect, the primary air circuit and the secondary air circuit share a single compressor while operating at different air pressures.

In another aspect, the disclosure relates to a method for managing an air supply in a machine having a high-pressure air circuit and a secondary air circuit, the secondary air circuit having a lower pressure than the high-pressure air circuit. In this aspect, the high-pressure air circuit and a secondary air circuit are driven by a single compressor. The method comprises sensing a pressure in the high-pressure air circuit to establish a first sensed pressure and holding open a first intake valve on the compressor if the sensed pressure exceeds a first deactivation threshold, and releasing the first intake valve if the sensed pressure is less than a first activation threshold. The method also comprises sensing a pressure in the secondary air circuit to establish a second sensed pressure, and holding open a second intake valve on the compressor if the sensed pressure exceeds a second deactivation threshold, and releasing the second intake valve if the sensed pressure is less than a second activation threshold.