GB1087213A - Diesel engine tachometer - Google Patents

Abstract

1,087,213. Tachometers. V.L. CHURCHILL & CO. Ltd. March 3, 1966 [Jan. 27, 1966], No.3775/66. Heading G1N. A tachometer for measuring the rotational speed of a diesel engine comprises a pressure sensitive detector which is clamped on to the fuel injection feed pipe in the engine's fuel system so that the dilation of the pipe by the injection of fuel stimulates the detector to provide an electrical signal representative of the dilation. A signal representative of the frequency of dilation of the pipe and therefore of the rotational speed of the engine is then derived from this. The detector comprises two stainless steel members 4, Fig. 2, mounted in a U-shaped alloy clamping member 1, which are held against opposite sides of the pipe by adjustment of screw 12. The outer faces of members 4 bear against the ends of Piezo-electric crystals 11, surrounded by sleeves 6 of insulating material. Contact screws 22 provide electrical connections to the outer ends of the crystals, through brass pads 5, and contact screw 23 provides an electrical connection to their inner ends. The voltage signal from the crystals is fed via a flexible cable (24), Fig. 1 (not shown), to a pre-amplifier (21), Fig. 3 (not shown), and then to an amplifier (14). A voltage representative of the frequency is finally read off from a meter (16), connected to the output of amplifier (14). A switch (20) is provided by which the device can be used for 2 or 4 stroke engines, an additional resistance being inserted in the meter circuit by the switch to halve the reading on the meter for a 2 stroke engine. The condition of a battery (15) supplying power to the amplifier (14) can be checked by connecting it to a meter (16), Fig. 1 (not shown), via a suitable resistance (not shown), when a button (19) is pressed.