RU1778584C - Device for measuring pressure in cylinder of internal combustion engine - Google Patents

Abstract

Usage: in measuring technique for measuring rapidly varying gas pressures in a cylinder of a reciprocating internal combustion engine (ICE). Purpose: improving the accuracy of pressure measurement. Summary of the invention: the device comprises a piezoelectric pressure sensor connected in series, a charge converter in the form of an operational amplifier with a measuring capacitor and a key between its inverting input and output, a measuring unit, as well as an operational amplifier, a key and a memory unit connected in series between the output and the non-inverting input of the converter charge. In addition, the device contains a serially connected converter of the angle of rotation of the crankshaft, a pulse shaper and a pulse delay circuit, the output of which is connected to the control input of the key, and the input to the control input of the key of the charge converter, the output of which is connected to the inverting input of the operational amplifier. Positive effect: reduction of errors caused by the zero drift of the operational amplifier. 3 ill. ё

Description

The invention relates to a measuring technique and can be used for measuring rapidly varying gas pressures in a cylinder (indexing) of a reciprocating internal combustion engine (ICE) when the pressure is cyclic in nature and has sections with a zero value.

An object of the invention is to increase the accuracy of pressure measurement. In addition, the invention allows not to select (match) transistors in the input differential cascade of the operational amplifier of the charge converter, which makes the device cheaper.

Fig. 1 is a functional diagram of a device for measuring pressure in an internal combustion engine cylinder; Figures 2 and 3 show diagrams as functions of the angle of rotation of the crankshaft explaining the operation of the device.

A device for measuring the pressure of gases in the cylinder of a piston internal combustion engine (Fig. 1) comprises a piezoelectric pressure sensor 1. connected in series 1. Charge converter 2, which is an operational amplifier 3 with a measuring capacitor 4 and a key 5 between its inverting input and output. a house, and a measuring unit 6, as well as a series-connected operational amplifier, a key8 and a memory unit9 between

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the output and non-inverting input of the charge converter 2. In this case, the output of the charge-transfer converter 2 is connected to the inverting input of the operational amplifier 7, the non-inverting input of which is connected to a common point of the circuit (case). In addition, the device contains a series-connected converter of the rotation angle of the crankshaft 10, the pulse shaper 11 from the pulse delay circuit 12, the output of which is connected to the control input of the key 8, and the input to the control input of the key 5 of the charge converter 2.

The device operates as follows. When the measured pressure P of gases, which has a cyclic nature, acts on the piezoelectric sensor 1, electric charges proportional to the pressure occur at the output of the latter, i.e. with the same form of variation in function of the angle of rotation as the gas pressure. By the charge converter 2, the electric charges are converted to the 11th electrical voltage. which is measured by measuring unit 6. However, errors may occur during the measurement process, i.e. the shape of the output voltage of the converter 2 may not correspond to the shape of the change in gas pressure due to the occurrence of spurious (uninformative) charges, the appearance of an uninformative component of the 11th voltage. Spurious charges can occur when a high cyclic temperature of combustion of gases in the internal combustion engine cylinder acts on the pressure sensor, bending and vibration of the cable connecting the pressure sensor 1 to the charge converter 2; an uninformative component of the output voltage Uwih may occur due to the non-identical characteristics of the transistors of the input differential stage of the operational amplifier 3 of the charge converter 2 when the ambient temperature changes, and also due to a change in the mode of the operational amplifier 3 when the key 5 is switched and the charge ( discharge) of the measuring capacitor 4 through spurious communications and from spurious sources (for example, thermoelectromotive force in the contacts of electrical circuits, sources of control signals, etc. ) The apertures illustrate how these errors are eliminated in the claimed device. Figure 2 indicates: Usad - output signal of the pulse delay circuit; AI - error due to spurious charges of the sensor and

cable Јu error due to the non-identical characteristics of the transistors of operational amplifiers. With temperature changes; Az is the error due to spurious communications and changes in the operational amplifier mode.

When the crankshaft reaches the angle of rotation p, the pulse shaper 11 generates an IFI voltage pulse from the signals from the converter of the angle of rotation of the crankshaft 10. which ends at a rotation angle (pi. Ifi pulse. acting on the control input of key 5, closes its contacts, as a result of which the measuring capacitor 4 is discharged, while the output charge of pressure sensor 1 is also zero. Thus, the error due to spurious charges at the input of the charge converter is eliminated.

When the angle of rotation of the crankshaft rz at the output of the pulse delay circuit 12, a voltage pulse 1) ead arises, which, acting on the key 8, causes it to close. When key 8 is closed, the output signal correction circuit is restored 1) Output: output of the operational amplifier 3 - inverting input of the operational amplifier 7 - key 8 - storage unit 9 - non-inverting input of the operational amplifier 3 - output of the operational amplifier 3. As a result of correction at the non-inverting input of the operational amplifier 3, a correction voltage UK is generated, which compensates the output voltage to zero (more precisely, to a value equal to

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0, where K is the gain of the operational amplifier 7). At a rotation angle of {%, the charge converter switches from the charge reset state to the charge conversion state as a result of opening the contacts of the reed switch 5. This transition is accompanied by the appearance of an uninformative component of the output voltage caused by the charge (discharge) measuring capacitor 4 through spurious connections between the control circuit of key 5 and the inverting input of operational amplifier 3 from spurious sources; ifi control signal and voltage arising from the movement of the reed switch contact in a magnetic field, as well as changing the operational amplifier 3 mode by constant current (the mode with the minimum feedback resistance when the switch 5 is closed, to the maximum feedback resistance mode, when key 5 is open). However, due to

of the fact that up to the time rz the output signal correction circuit is activated Uh, these arising uninformative voltage components are compensated. At an angle of rotation p $, the correction circuit breaks with and the device enters the measurement mode, but the correction voltage UK due to the storage unit is stored until the next reset and correction cycle. The torque rz is chosen so that it coincides or is close to the moment when the measured pressure and, consequently, the charge are equal or close to zero, for example, at the bottom dead center of the piston (BDC). Thus, when the device enters the measurement mode, the input zero signal of pressure corresponds to a zero output signal 1) output, i.e. conversion accuracy (measurement) is improved.

Claims (1)

Claims A device for measuring the pressure in a cylinder of a reciprocating internal combustion engine, comprising a piezoelectric pressure sensor in series, a charge transducer, which is an operational amplifier with a measuring capacitor and a key between its inverting input and output, and a measuring unit, as well as a series-connected converter of the angle of rotation of the crankshaft and a pulse shaper, the output of which is connected to the control input of the key of the charge converter, characterized in that that, in order to increase the accuracy of pressure measurement, it is equipped with a storage unit, a second key and an additional operational amplifier, as well as a pulse delay circuit, the inverting input of the additional operational amplifier is connected to the output of the charge converter, the output of the additional operational amplifier through a second key and a memory block connected in series is connected to the non-inverting input of the operational amplifier of the charge converter, and the output of the pulse former through the pulse delay circuit is connected to the control input of the second the key. phage th fc - 35 W-% 1778584 About 12 SHGZ  X 48 VO