Apparatus for indicating the degree of dirtiness of a filter

• US 5,681,988 A
• Filed: 08/09/1995
• Issued: 10/28/1997
• Est. Priority Date: 08/23/1994
• Status: Expired due to Fees

• Current Assignee: FILTERWERK Mann & HUMMEL GmbH
• Original Assignee: FILTERWERK Mann & HUMMEL GmbH
• Inventors: Schnabel, Werner, Koch, Volker
• Primary Examiner(s): Dombroske, George M.
• Application Number:
  US08/512,905
• Time in Patent Office: 811 Days
• Field of Search: 73/118.1, 73/38, 73/118.2, 340/607, 340/451
• US Class Current: 73/114.31
• CPC Class Codes: B01D 46/46 automatic

Abstract

An apparatus for indicating the extent to which an air filter in an internal combustion engine is fouled. For this purpose the apparatus includes a pressure sensor, a sensor to detect the rotational speed of the engine, and an additional sensor which determines the load state of the engine. The signals of the three sensors are combined and serve to produce an air filter dirtiness indicating signal.

Claims

1. An apparatus for indicating the degree of dirtiness of an air filter of an internal combustion engine, comprising a sensor which detects air pressure downstream of the filter, a sensor which detects engine speed, a sensor which detects engine load, and means for combining signals emitted by said sensors to yield a filter dirtiness indicator signal, wherein said signal combining means is an electronic circuit which comprises an EPROM programmed to produce said dirtiness indicator signal when the pressure sensor detects a pressure below a pressure threshold value, the engine speed sensor detects an engine speed above an engine speed threshold value, and the engine load sensor detects an engine load below an engine load threshold value.

2. An apparatus according to claim 1, wherein the electronic circuits includes an iteration circuit which counts the number of occurrences when said dirtiness indicator signal is produced and which triggers a dirtiness indicator after a selected number of said occurrences.

3. An apparatus for indicating the degree of dirtiness of an air filter of an internal combustion engine, comprising a sensor which detects air pressure downstream of the filter, a sensor which detects engine speed, a sensor which detects engine load, and an electronic circuit for combining signals emitted by said sensors to produce a filter dirtiness indicator signal, wherein each of the sensors produces a signal when the internal combustion engine is under partial load, and the electronic circuit comprises an extrapolation circuit which determines a reduction of air throughput through the filter at full load due to dirtiness of the filter.

4. An apparatus for indicating the degree of dirtiness of an air filter of an internal combustion engine, comprising a sensor which detects air pressure downstream of the filter, a sensor which detects engine speed, a sensor which detects engine load, and means for combining signals emitted by said sensors to produce a filter dirtiness indicator signal when the pressure sensor detects a pressure below a pressure threshold value, the engine speed sensor detects an engine speed above an engine speed threshold value, and the engine load sensor detects an engine load below an engine load threshold value.

5. An apparatus according to claim 4, wherein at least one of the pressure sensor, the engine speed sensor and the engine load sensor produces a digital signal.

6. An apparatus according to claim 4 wherein the threshold pressure value is adjustable.

7. An apparatus according to claim 4, wherein said signal combining means comprises an electronic circuit which produces said dirtiness indicator signal.

8. An apparatus according to claim 7, wherein the electronic circuit includes an iteration circuit which counts the number of occurrences when said dirtiness indicator signal is produced and which triggers a dirtiness indicator after a selected number of said occurrences.

9. An apparatus according to claim 7, wherein each of the sensors produces an output signal when the internal combustion engine is under partial load, and the electronic circuit comprises an extrapolation circuit which determines a reduction of air throughput through the filter at full load due to dirtiness of the filter.