Control for engine driven compressor
View Patent ↗A controller for a vehicle pneumatic system loads a compressor responsive to engine power absorption by the engine and air storage facility air pressure readings up to a pressure limit. The controller is responds to power demand on the engine in excess of an engine speed related global maximum and air pressure readings down to a global minimum for unloading the compressor. The controller provides for loading and unloading the compressor to maintain storage facility pressure within an operating maximum and an operating minimum which lie between the global maximum and global minimum pressures. The controller responds to air pressure readings reaching or falling below the global minimum for loading the compressor and to air pressure readings reaching or exceeding the global maximum for unloading the compressor.
1. A vehicle pneumatic system, comprising:
an engine having a predetermined idle speed, and having a maximum allowed fuel flow (MF_TOT) and a maximum fuel allowed for smoke limiting (MF_SLM);
an air compressor coupled to the engine to be driven by the engine;
an air storage facility connected to receive air pumped by the air compressor;
an air compressor unloader;
an air pressure sensor for reading air pressure in the air storage facility and sending signals representative thereof;
the air storage facility having a predetermined normal operating maximum pressure and a predetermined normal operating minimum pressure;
the air storage facility also having a predetermined global minimum pressure which is less than the predetermined normal operating minimum pressure, and having a predetermined global maximum pressure greater than the predetermined normal operating maximum pressure;
engine condition sensors for indicating power output from or absorption by the engine, power requested from the engine and engine speed and sending corresponding respective engine condition signals indicative thereof;
an engine control module operatively connected with the air pressure sensor and at least one of the engine condition sensors for receiving the air pressure signals and the engine condition signals, with the engine control module programmed to determine whether the engine is operating in one of: 1) a first engine state in which the engine speed is above the predetermined idle speed of the engine and the power requested from the engine is below a predetermined A minimum power; and 2) a third engine state in which the value of the difference between MF_SLM and MF_TOT is below a predetermined minimum; and 3) a second engine state which is a steady state indicated for all engine conditions not included in the first engine state and the third engine state;
the engine control module operatively connected with the unloader to control operation of the unloader;
when the engine is operating in the second engine state, the engine control module controls the unloader to cycle the unloader on and off to maintain the pressure in the air storage facility between the predetermined normal operating maximum pressure and the predetermined normal operating minimum pressure, with the pressure not allowed to exceed the predetermined normal operating maximum pressure or fall below the predetermined normal operating minimum pressure;
when the engine is operating in the first engine state, the engine control module controls the unloader to allow the pressure in the air storage facility to exceed the predetermined normal operating maximum pressure up to the predetermined global maximum pressure; and
when the engine is operating in the third engine state, the engine control module controls the unloader to allow the pressure in the air storage facility to fall below the predetermined normal minimum pressure down to the predetermined global minimum pressure.
2. The vehicle pneumatic system of claim 1 , further comprising:
the air compressor unloader being pneumatically powered; and
a three-way valve under the control of the engine control module for fluidically connecting the air compressor unloader to the compressed air facility or to an ambient environment.