Measuring and testing – Internal combustion engine or related engine system or... – Compression
Patent
1981-06-10
1983-06-14
Myracle, Jerry W.
Measuring and testing
Internal combustion engine or related engine system or...
Compression
73168, G01M 1500
Patent
active
043875890
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention is related to test stands which have means for driving a drive shaft to drive a mechanism to be tested and calibrated and, in particular, to test stands for calibrating injection fuel pumps and governors associated therewith.
2. Background Art
Present test stands for testing injection fuel pump and governor arrangements and the like include a motor which drives a drive shaft and instrumentation for determining the rotational speed of the shaft. Apparatus is also provided for connecting the fuel injection pump to be tested with the drive shaft.
Present test stands are unable to maintain a constant drive shaft speed during the testing of the fuel injection pumps. The reason for this is inherent in the operation of the injection fuel pump itself. During a 360.degree. revolution of the fuel injection pump's cam shaft, the pump can, for example, inject six metered amounts of fuel into the appropriate cylinders of a six cylinder diesel engine. Each injection cycle takes up 60.degree. of the entire revolution of the shaft. Of these 60.degree., 12.degree. may be used to inject the fuel, which injection places a substantial jerk type load on the motor driving the test stand, and the remaining 48.degree. may be a no-load, coast condition. In some situations, it is possible for the speed of the drive shaft to drop up to 70 or 80 rpm during the load conditions and then return to the test speed, which can be, for example, in the range of from 700 rpm to 1,300 rpm, during no-load conditions. Thus, it can be seen that test results and calibrations are adversely affected by the inability of the present test stands to maintain a constant speed throughout the testing of the fuel injection pumps due to the intermittent jerk loads applied to the test stand.
Some prior art test stands have attempted to solve the problem of constant speed testing of the fuel pumps by providing a drive shaft which has substantial flywheel mass associated therewith to help stabilize the drive shaft for constant speed, fuel injection pump testing. However, the additional mass is a hindrance when the drive shaft must be instantaneously accelerated in order to test the reaction time of the governor associated with the fuel pump. Generally, with such an arrangement, in order to rapidly overcome the inertia associated with the drive shaft, the motor must deliver and the drive members transmit large forcing torques. If, on the other hand, nominal motor driving torque is applied to the high mass drive shaft, relatively slow speed changes will occur. The speed change from the lower to the higher final speed will be too slow to properly test the response time of the governor. It is to be understood that the above problems also exist when the governor response time is to be tested for a final speed which is lower than the initial speed.
Also, it is noted that due to the difficulty of accurately aligning the parallel shafts of test stand drive and fuel pump, undesirable side loading of the shaft bearing may occur. Thus, there is a need to relieve this loading by accommodating shaft misalignment.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF INVENTION
In one aspect of this invention, a test stand has a drive shaft and the improvements comprise an inertial weight operatively associated with the drive shaft and means for selectively engaging and disengaging the inertial weight from the drive shaft.
For constant speed tests of the injection fuel pump, the inertial weight can be engaged with the drive shaft to insure that only small design value changes occur in the drive shaft speed during the jerk loading placed on the drive shaft by the operation of the injection fuel pump. In order to check the governor response time, the inertial weight is selectively disengaged from the drive shaft and the drive shaft is rapidly accelerated or decelerated to a final desired speed without the necessity of overcoming the inertia of said inertial weight. Th
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Bacharach Instrument Company, Pittsburgh PA, "Calibration Stand Accessories for Caterpillar Pumps" 2/76 (New Prod. Bulletin).
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Caterpillar Tractor Co.
Myracle Jerry W.
Woloch Anthony N.
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