JPH01213535A - Inside-cylinder pressure detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To stabilize pressure signals by providing a current-voltage converting function element in a piezo-electric type inside-cylinder pressure sensor. CONSTITUTION:The pressure-electric charge quantity converting factor of a piezo-electric type inside-cylinder pressure sensor 1 has a positive temperature characteristic and, when the temperature rises, the quantity of the electric charge outputted from the sensor 1 increases and correction is required to the temperature change in order to obtain correct inside-cylinder pressure values. Therefore, a thermistor 6 is assembled in the sensor 1. When the thermistor 6 is assemble in the sensor 6 as part of the feedback resistance of an operational amplifier 51 so that a change in the resistance value caused by the temperature change of the thermistor 6 can immediately change the current-voltage converting factor, the sum of the resistance values of a resistance 53 and the thermistor 6 becomes smaller because of the change in the resistance value of the thermistor 6, even when the temperature of the sensor 1 rises and the quantity of its output electric charge increases and, as a result, the output signal of the amplifier 51 tends to become larger. Therefore, stable inside-cylinder pressure signals can be obtained always regardless of the temperature change of the sensor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cylinder pressure detector for an internal combustion engine that measures pressure information within a combustion cylinder of an internal combustion engine.

[Conventional technology]

In order to measure the combustion state of an internal combustion engine and the IJ operation for each rotation cycle, the pressure within the combustion cylinder is generally measured. A piezoelectric cylinder pressure sensor is often used as the cylinder pressure sensor used for this constant squeezing. This piezoelectric cylinder pressure sensor outputs an amount of charge according to the applied pressure by directly or indirectly applying pressure within the cylinder to a piezoelectric element that generates a charge in response to pressure. For example, an example of a piezoelectric cylinder pressure sensor is shown in FIG. In Fig. 4, (1υ is a piezoelectric element, an electrode sandwiched between the astrss piezoelectric elements and leads the output signal to the lead wire circle, and 04 is a case that covers the internal structural parts of the sensor. This piezoelectric cylinder pressure sensor has a ring-like shape, and is installed between the cylinder head +21, which forms one of the combustion cylinders of the engine, and the spark plug 131, as shown in Fig. 5.Then, the pressure inside the combustion cylinder is Pressure 1 is transmitted through the mastication plug to the piezoelectric element Oυ of the shaped section internal pressure sensor, and an electric charge corresponding to the cylinder pressure is output.

By the way, since the output signal corresponding to the in-cylinder pressure of the piezoelectric in-cylinder pressure sensor is an amount of electric charge, it is necessary to convert this electric charge itt' into a voltage value that can be easily processed by 'Jft'. Therefore, a charge amplifier has generally been used as a means for converting the voltage into a total voltage value of 1. Figure 86 shows the basic circuitry of the charge amplifier. In FIG. 6, it is an operational amplifier and a vItvi capacitor. The output of the piezoelectric type front internal pressure sensor is connected to the inverting input of the operational amplifier (inverter), and the capacitor is connected between the inverting input and output of the operational amplifier ha. Further, the non-inverting input of the operational amplifier 4υ is grounded. Now, the output is controlled so that the inverting and non-inverting input voltages to the operational amplifier (6) are at the same level, and the charge Q is output from the piezoelectric cylinder pressure sensor Il+.
When is input, the operational amplifier (converter) conducts a control operation such that all the charges Q and 1 are photoelectrically applied to the capacitor.

Therefore, if the capacitance of capacitor 4 is 1c, then V =
A voltage called Q/C appears at the central voltage of the operational amplifier.

Since the charge 1itQ#- is proportional to the in-cylinder pressure, the output voltage V of the operational amplifier takes into account the in-cylinder pressure, and during engine operation, the combustion pressure as shown in Figure 7 Outputting a signal @ [The problem to be solved by the invention] However, in the above-mentioned piezoelectric cylinder pressure sensor, there is a change in the piezoelectric charge acid characteristic due to temperature change, and the piezoelectric element There is a characteristic of charge generation called the pyro effect in response to temperature changes. In particular, when it is installed near the combustion chamber as shown in Figure 2, the temperature of the cylinder head (2) and spark plug; The output signal waveform of the charge amplifier described above is greatly affected by the temperature change, making it impossible to accurately measure the internal pressure. Further, even if some form of temperature compensation is attempted, there is a problem in that the charge amplifier circuit directly converts the output charge into a voltage value at a single capacitor, making it complicated.

The present invention has been made in view of the above-mentioned problem in VC, and when obtaining a signal corresponding to the cylinder pressure from the output signal of the cylinder pressure sensor, it is possible to obtain an accurate cylinder pressure signal that is not affected by temperature changes of the cylinder pressure sensor. Pressure gauge I! The purpose is to realize 1ll11fr.

[Means to solve the problem]

The in-cylinder pressure detection device for an internal combustion engine according to the present invention receives an output current signal of a piezoelectric in-cylinder pressure sensor, and receives the output current signal from the piezoelectric cylinder pressure sensor.
A signal related to internal pressure information is obtained by converting fm into a voltage value, and in particular, an electric-voltage conversion functional element is included in the piezoelectric cylinder pressure sensor.

[Effect]

In the present invention, changes in the output of the piezoelectric cylinder pressure sensor due to temperature changes are corrected by a 1M current-voltage conversion function element.

〔Example〕

FIG. 1 shows an embodiment of the present invention. In Figure 1, 1. )
υ and F12+ are operational amplifiers, ・4, whisper, 571 is a resistor,
I41 and +1 are capacitors. The output of the piezoelectric cylinder pressure sensor 1 is connected to the inverting input of the operational amplifier 5υ and one end of the thermistor 16) embedded in the piezoelectric cylinder pressure sensor +l+, and the resistor is connected to the output of the operational amplifier Jυ and the other end of the thermistor (61). The capacitor I and the resistor are connected in parallel between the output of the operational amplifier I and the inverting input of the operational amplifier (2), and the resistor and the resistor are connected in parallel to the inverting input of the operational amplifier (2). and the output. Further, the non-inverting inputs of the operational amplifier 60 and the detector are both grounded.

Next, the operation of the embodiment shown in FIG. 5 will be explained.

Now, when a charge Q is output from the output of the piezoelectric cylinder pressure sensor corresponding to the cylinder pressure, the feedback control of the operational amplifier 6υ causes a current of −””/(lt to flow from the operational amplifier 5υ to the resistor i3. Then, if the voltage between the resistor 53 and the thermistor (61 is one year lower), the output voltage V of the operational amplifier 60 is the sum of the resistance value of the resistor t+i and the thermistor 16), then R1, vl-- R1 ball t.That is, the output current of the piezoelectric part internal pressure sensor is 4.
t is expressed as a voltage value.

This operational amplifier has an output voltage v1 of 1υ and is a modified r second
Ial l/(shown in the figure). This waveform corresponds to the pressure in the building that is time-differentiated.

Next, a current flows from the output of the operational amplifier 50 to the inverting input VC of the operational amplifier 50 via the capacitor and the resistor 5@.

Here, capacitor A is used for current coupling, so its capacitance is set sufficiently large so that X
The impedance becomes pitifully small with respect to the current electrification rate VC. Therefore, the current flowing there is determined by the output voltage v1 of the operational amplifier 5υ and the resistance value R1, as shown in the following equation.

VIR + dQ I, -1 - 1 yen, and a tIIL current flows from the output of the operational amplifier 4IZ by the feedback IIIJ#. Here, Tokun and Tsukasa are operational amplifiers) Force output - pressure Vs k *
It is used as a resistance to return to zero point with time and number.

The resistance equation is #
The resistance value is set to a high value such that tItfIt can be reached at t@degrees. frl, the output voltage of operational amplifier -5z is V! is determined by the output current - engineering and the capacitance c3 of the capacitor 6, as shown in the following equation.

That is, the output '1 voltage V1 of the operational amplifier is proportional to the output '-load Q of the piezoelectric part internal pressure sensor +11,
As shown in tb+vc in Fig. 46, the output number 1 corresponds to the inward pressure itself.

By doing this, it is possible to obtain an rtJ internal pressure of 1 g.

By the way, piezoelectric type 1! I] The internal pressure sensor has a positive temperature characteristic, and when the -temperature becomes too low, the output increases. Therefore, the Boomister +6
The output f1 of the 4-way operational amplifier ^υ without 1 is shown in Figure 2 1&
The pressure increases as shown by the temporary line I, and in order to overcome the previous pressure which is a stopper, it is necessary to correct the temperature change of the piezoelectric high internal pressure sensor I11. Therefore, in the embodiment, one thermistor 16) is installed inside the pressure '1 type cylinder pressure sensor +l+ as shown in FIG. It is incorporated. In FIG. 3, an insulating plate a51 and an electrode tank are added to the thermistor 16) as compared to FIG. 1. The thermistor 161 itself is made to become part of the feedback resistance of the operational amplifier jl. Therefore, the thermistor (6) forms a part of the current-voltage conversion element, and a change in resistance due to a temperature change in the thermistor (61) immediately changes the current-voltage conversion coefficient.

6 Yes, the temperature of the piezoelectric cylinder pressure sensor Il+ rises,
Even if the output signal of the operational amplifier 5a increases as shown by the broken line in FIG. Because the sum becomes smaller, it is possible to obtain the signal shown by the solid line in FIG. 8 (ILl) regardless of the single-grade eclipse of the piezoelectric cylinder pressure sensor +l+, and the cylinder is always stable as shown in FIG. 2 1b+. An internal pressure signal can be obtained.

In the above embodiment, a thermistor was used as the temperature measuring device, but a method using a semiconductor or the like may also be used.

〔Effect of the invention〕

As explained above, according to the present invention, even if a temperature change occurs in the sensor due to the cylinder pressure, a stable cylinder pressure signal can be obtained without any fluctuations caused by the temperature change.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment according to the present invention, and FIG. 2 is a circuit diagram of an embodiment according to the present invention.
Figure 3 is a cross-sectional structural diagram of the piezoelectric cylinder pressure sensor according to the embodiment shown in Figure 1, Figure 4 is a cross-sectional structural diagram of the piezoelectric cylinder pressure sensor, and Figure 5 is 6 is an installation diagram of a piezoelectric cylinder pressure sensor, FIG. 6 is a circuit diagram of a conventional device, and FIG. 7 is an output waveform diagram of a conventional device.

Claims (1)

[Claims] It is composed of a piezoelectric pressure detector that detects the pressure in the combustion cylinder of an internal combustion engine, and a current-voltage converter that receives the output current signal of the piezoelectric pressure detector and converts the current value into a voltage value. An in-cylinder pressure detection device for an internal combustion engine, wherein the piezoelectric pressure detector includes a conversion function element of the current-voltage converter.