Valvetrain testing using instrumented pushrod
A technique for testing a pushrod valvetrain in an engine includes replacing an original pushrod with an instrumented pushrod (IPD) which includes a sensor configured to measure strain and/or motion. The engine is then operated, and the output of the sensor is monitored for anomalies. Diagnosis and repair of identified defects may then follow.
1. A method of testing a pushrod valvetrain of an internal combustion engine, comprising:
replacing a pushrod of the engine with an IPD (instrumented pushrod) that includes a sensor configured to measure strain and/or motion, the IPD configured to move back and forth within a tube and including a guide configured to move back and forth within a slot of the tube;
operating the engine in a fired arrangement with the IPD in place; and
monitoring the output of the sensor to identify anomalies.
2. The method of claim 1 , wherein monitoring the output of the sensor to identify anomalies includes comparing output from the sensor with that of a modeled, ideal valvetrain and identifying discrepancies.
3. The method of claim 1 , further comprising receiving electrical signals from sensor, digitizing the electrical signals, and recording the electrical signals for analysis and/or viewing.
4. The method of claim 1 , wherein the tube includes a proximity sensor, and wherein the method further comprises monitoring, by the proximity sensor, a position of the guide as the guide moves back and forth within the slot.
5. The method of claim 1 , wherein the sensor includes a first strain gauge oriented axially with the IPD to measure axial strain, wherein the IPD further includes a second strain gauge oriented perpendicularly to the first strain gauge, and wherein the method further comprises applying strain measurements from the second strain gauge to compensate output of the first strain gauge for variations in temperature.
6. The method of claim 1 , further comprising replacing a second pushrod of the engine with the IPD, operating the engine in a fired arrangement with the IPD in place of the second pushrod, and monitoring the output of the sensor to identify additional anomalies.
7. The method of claim 1 , wherein the IPD is one of a plurality of IPDs that replace respective pushrods of the engine, each of the plurality of IPDs having a sensor, and wherein the method further comprises:
operating the engine in a fired arrangement with the plurality of IPDs in place; and
monitoring the output of the sensor of each of the plurality of IPDs to identify anomalies.
8. The method of claim 1 , wherein the sensor is configured to communicate wirelessly with a test station, and wherein monitoring the output of the sensor includes receiving, by the test station, wireless signals from the sensor.
9. An apparatus for testing a pushrod valvetrain of an internal combustion engine, comprising:
an IPD (instrumented pushrod) that includes a guide that extends radially outwardly from the IPD and a sensor configured to measure strain and/or motion;
a tube within which the IPD is constructed and arranged to move back and forth when the engine is operated; and
a measurement station constructed and arranged to receive measurements from the sensor and to identify anomalies in the measurements,
wherein the tube includes a slot within which the guide is constructed and arranged to move back and forth when the engine is operated.
10. The apparatus of claim 9 , wherein the measurement station constructed and arranged to receive measurements from the sensor is further constructed and arranged to receive the measurements in wireless signals transmitted by the sensor.
11. The apparatus of claim 9 , further comprising a set of wires that extends through the slot from the sensor to the measurement station.
12. The apparatus of claim 9 , wherein the tube includes a proximity sensor constructed and arranged to measure a position of the guide as the guide moves back and forth within the slot.
13. The apparatus of claim 12 , wherein the guide comprises a metallic material, and wherein the proximity sensor comprises an inductive sensor.
14. The apparatus of claim 12 , wherein the guide comprises a non-metallic material, and wherein the proximity sensor comprises a capacitive sensor.
15. The apparatus of claim 9 , wherein the sensor includes a first strain gauge, wherein the IPD includes a second strain gauge oriented perpendicularly to the first strain gauge, and wherein the apparatus further includes a second set of wires extending through the slot between the second strain gauge and the measurement station.
16. An instrumented pushrod (IPD), comprising:
an elongated rod;
a sensor attached to or integral with the elongated rod, the sensor constructed and arranged to measure strain and/or motion; and
a guide that extends radially outwardly from the elongated rod, the guide constructed and arranged to resist rotation of the elongated rod during engine operation.
17. The IPD of claim 16 , wherein the sensor is bonded to the elongated rod using epoxy.
18. The IPD of claim 16 , further comprising:
a set of wires that attach to the sensor, the set of wires extending axially over a portion of the elongated rod; and
a retainer constructed and arranged to hold the set of wires against the elongated rod over the portion of the elongated rod.
19. The IPD of claim 16 , wherein the sensor includes a first strain gauge, and wherein the IPD further comprises a second strain gauge oriented perpendicularly to the first strain gauge.
20. The IPD of claim 16 , wherein the guide is attached to or integral with the elongated rod.