GB1254164A - Improvements in or relating to fuel injection systems - Google Patents

Abstract

1,254,164. I.C. engine fuel injection systems. ROBERT BOSCH G.m.b.H. Feb. 6, 1969 [Feb. 13, 1968; Sept.30, 1968J, No.6492/69. Heading G1N. [Also in Division F1 In an I.C. engine fuel injection control system, the duration of solenoid operable injection valve opening pulses, from a multi-vibrator 28, Fig. 1, is determined as a function of the absolute pressure in the intake manifold 12 and the difference between the intake manifold pressure and the environmental barometric pressure, the construction of the pressure transducer being such that the valve opening period is controlled to provide maximum engine performance at all speeds and at all altitudes, less fuel being required at higher altitudes. The transducer 37, Fig. 4, includes a housing divided by a diaphragm 86 into two chambers 104, 105, chamber 104 being connected to atmosphere via passage 106, and chamber 105 being connected to the intake manifold via passage 38. The diaphragm is movable between two steps 87, 102. At low speeds i.e. low intake manifold pressure, diaphragm 86 abuts step 87 and a core 129 is positioned relative to two coils 118, 119 which control the multi-vibrator 28. As the engine speed increases, the intake manifold pressure increases thus causing pressure in chamber 105 to compress vacuum-diaphragm box 138 to move core 129 downwardly and thus increase the inductance of coils 118, 119 to increase the pulse duration. At a predetermined pressure, diaphragm 86 moves away from step 87 to further increase the inductance of coils 118, 119 and thus the pulse duration, the movement being limited by step 102. At the maximum speed the intake manifold pressure equals the atmospheric pressure. In Figs. 7 and 8 (not shown), the difference between the graphs of intake manifold pressure v pulse duration at sea level and at high altitude is illustrated. The shape of these graphs are also dependent upon the shape of core 129, the characteristics of diaphragm boxes 138, 140 and the spring rate of spring 146, leaf-springs 123, 124, which centre the core 129, and diaphragm 86. For altitude compensation at low engine speeds, the step 87 may be replaced by a resilient disc (160) having holes therethrough so that the pressure in chamber 105 acts on diaphragm 86, and the step 102 may be omitted, Figs. 9 to 12 (not shown). Further the diaphragm 86 may be omitted, Fig. 3 (not shown). The pulse duration may be additionally dependent upon engine speed and temperature.