JP2016061218A - Turbocharger rotation speed detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbocharger rotation detection device capable of always accurately and surely detecting an instantaneous rotation speed, regardless of difference even when the shapes and characteristics of vanes of the turbocharger are different.SOLUTION: A turbocharger rotation speed detection device for detecting a rotation speed of a turbocharger mounted on an engine includes: a peak detection circuit for detecting a peak of a detection signal from a turbo sensor disposed so as to approach a compressor vane of the turbocharger; and an instantaneous rotation speed calculation circuit for calculating an instantaneous rotation speed of the turbocharger on the basis of a peak signal detected by the peak detection circuit.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a turbocharger rotation speed detection device having a small and inexpensive configuration for detecting the rotation speed of a turbocharger (supercharger) mounted on an engine, and particularly, disposed near a compressor vane of the turbocharger. The present invention relates to a turbocharger rotation speed detection device capable of accurately and reliably detecting an instantaneous rotation speed of a turbocharger based on a detection signal from a turbo sensor without being affected by a machine difference.

  In an internal combustion engine such as an automobile, the output is related to the mass of air that can be provided to the engine for combustion and the corresponding amount of fuel, and more if you want to improve the output of the internal combustion engine. Combustion air and more fuel must be supplied. A turbocharger provided with a turbocharger is known as a supercharger for improving output without increasing the size. The turbocharger mainly includes a fluid compressor and a turbine, and the fluid compressor and the turbine are coupled by a common shaft and rotate at the same rotational speed. The turbine converts the energy of the exhaust gas that normally disappears without being used into rotational energy, and drives the compressor. The compressor draws in fresh air and pumps precompressed air into the individual cylinders of the engine. The larger air mass in the cylinder can be supplied with an increased amount of fuel. As a result, the internal combustion engine releases more output.

  FIG. 1 shows an example of the structure of a general turbocharger 10 including a turbine 20 and a compressor 30. A compressor wheel 31 is rotatably supported in the compressor 30 and is coupled to the turbo shaft 11. ing. The turbo shaft 11 is also rotatably supported and is connected to the turbine wheel 21 at the other end. High-temperature exhaust gas is caused to flow from the internal combustion engine (not shown) into the turbine 20 through the turbine inlet 22 to rotate the turbine wheel 21. The exhaust gas stream exits from the turbine 20 through the turbine outlet 23. Since the turbine wheel 21 is coupled to the compressor wheel 31 via the turbo shaft 11, the turbine 20 drives the compressor 30 thereby. Air is sucked into the compressor 30 through the air inlet 32 (FIG. 3), compressed, and supplied to the internal combustion engine through the air outlet 33.

  FIG. 2 shows the coupling relationship between the turbine wheel 21, the turbo shaft 11, and the compressor wheel 31, and the turbine wheel 21 is generally made of a heat-resistant austenitic nickel compound. The component part which consists of the turbine wheel 21 and the turbo shaft 11 is called a rotor or a rotary body. The compressor wheel 31 is manufactured from, for example, an aluminum alloy by a precision casting method or the like. The compressor wheel 31 is fixed to the compressor-side end 12 of the turbo shaft 11 by a fixing element 34. The fixing element 34 may be a cap nut 35, for example. The cap nut 35 firmly tightens the turbine wheel 21 against the turbo shaft collar with the seal bush, the bearing collar, and the spacer bush. Therefore, the rotating body forms a rigid unit with the compressor wheel 31.

  FIG. 3 shows a compressor 30 having an air inlet 32 and an air outlet 33, and a cylindrical adapter 36 is arranged at the air inlet 32. The adapter 36 is coupled to a helical compressor housing 37 by, for example, screws 38.

  The rotation speed of the turbocharger is necessary for engine control, but the rotation speed of the turbocharger reaches 200,000 to 500,000 rpm, the temperature is 500 to 1000 ° C., and the measurement environment is severe. Or it is very difficult to directly measure the rotational speed of the turbine wheel.

  For this reason, in Japanese Patent Application Laid-Open No. 2008-506074 (Patent Document 1), as an apparatus for detecting the rotational speed of the turbo shaft, an element for changing the magnetic field is provided at the end of the turbo shaft on the compressor side. Change is caused in relation to the rotation of the turboshaft, the sensor element is arranged close to the element for changing the magnetic field, so that the sensor element detects the change of the magnetic field. It has become.

  However, in the detection of the rotational speed of the turboshaft according to Patent Document 1, an element for changing the magnetic field must be mounted on the compressor side end of the turboshaft, and the element is enlarged because the shaft diameter of the turboshaft is small. As a result, the magnetic field change cannot be detected with high sensitivity. Further, since the sensor element obstructs the air flow, the performance of the turbocharger is degraded. For this reason, there is a problem in terms of detection accuracy as well as an increase in cost in manufacturing the turbocharger.

  In JP 2007-89336 A (Patent Document 2), a sensorless permanent magnet synchronous motor is provided on a turbo shaft, and the rotation of the sensorless permanent magnet synchronous motor during driving is based on the motor drive current detected by the drive current detecting means. The rotation state estimation means for estimating the state and the rotation state detection means for detecting the rotation state during non-driving are switched and used. In the apparatus of Patent Document 2, there is a problem that a large sensorless permanent magnet synchronous motor is provided as an apparatus, and means necessary for the control must be separately installed.

  Japanese Patent Application No. 2012-522305 (Patent Document 3) by the present applicant has been proposed as a turbocharger rotation detection device for solving such a problem. In Patent Document 3, a protruding eddy current sensor 100B is used as a rotation sensor of a turbocharger, and this eddy current sensor 100B is mounted on a compressor 30 of the turbocharger as shown in FIGS. That is, the eddy current sensor 100 </ b> B is attached to the air inlet 32 of the compressor 30 so as to face the blade rotation surface of the compressor wheel 31. The eddy current sensor 100B is mounted by, for example, forming a predetermined hole in the vicinity of the air inlet 32 of the compressor 30 and fitting the outer tube of the eddy current sensor 100B into the hole, screwing, or fixing by welding. .

  As shown in FIG. 5, the turbocharger 10 includes a turbine 20 that is rotationally driven by the exhaust gas flow of the engine, a compressor 30 that is rotationally driven by the rotation of the turbine 20 and pressurizes intake air, and the turbine 20 and the compressor 30. And a turbo shaft 11 connecting the two. The housing 13 accommodates a bearing 14 that supports the turbo shaft 11 so as to be rotatable in the radial direction. The turbine 20 includes a turbine wheel 21 having a plurality of turbine blades, and a turbine housing 24 that is a portion of the housing 13 that houses the turbine wheel 21. The compressor 30 includes a compressor wheel 31 having a plurality of (for example, 5 to 12) compressor blades (vanes) and a compressor housing 37 that is a part of the housing 13 that accommodates the compressor wheel 31. . The eddy current sensor 100B penetrates the compressor housing 37 and is attached by fitting, screwing or welding, and the sensor top is attached in the vicinity of the blade rotation surface. When the turbine wheel 21 is rotated by the exhaust gas, the compressor wheel 31 is rotated together with the turboshaft 11, and the air taken into the intake passage in the compressor housing 37 is compressed and sent to the combustion chamber.

FIG. 6 shows an example of a detection circuit connected to the eddy current sensor 100B to detect the turbo rotational speed. As described above, the eddy arranged in the vicinity of the vane (blade) rotation surface of the compressor wheel 31. The current sensor 100B is driven by a resonance circuit 110, and is connected to a detection circuit 111 that extracts a signal component that changes corresponding to the displacement caused by the rotation of the vane. Signal component extracted by the detection circuit 111 is amplified by an amplifier 112, it is binarized by the binarization circuit 113 of the comparator or the like having a threshold TH _0, binary pulse signal P1 is at the frequency divider 114 The frequency is divided and converted so that, for example, one pulse is output by one rotation of the turbine. Thus, by counting the frequency-divided pulse P2, the rotation speed detection circuit (counter) 115 can detect the turbine rotation speed RN and measure the average rotation speed by time conversion.

Here, the output waveform of the sensor 100B is as shown in FIG. 7, for example, as shown in Figure 6, is binarized by the threshold value TH ₀ lower than all waveform peak value.

JP 2008-506074 A JP 2007-89336 A Japanese Patent Application No. 2012-522305

However, the output waveform of the sensor 100B is not the same based on the variation in the thickness of the compressor vane, the difference in the shape and material of the vane, the eccentricity of the turbo shaft, and the like. As shown in detail, the pulse widths Wb1, Wb2,... Corresponding to the vane thickness with respect to the threshold Th ₀ and the wavelength intervals ΔT1, ΔT2,. However, the value is different for each turbocharger. Therefore, the pulse waveform binarized with respect to the threshold Th ₀ is not uniform as shown in FIG. 9, and the pulse intervals ΔT1, ΔT2,. As a result, when measuring the instantaneous rotation speed, there is a problem that accurate measurement cannot be performed. In recent years, the instantaneous rotation speed of a turbocharger has become an important factor in engine control.

  FIG. 10 shows the variation (tolerance) of the instantaneous rotational speed {rpm} measured for each blade number (No. 0 to No. 42), and the accurate instantaneous rotational speed measured with little tolerance. Is required for advanced engine control.

  The present invention has been made under the circumstances described above. The object of the present invention is to always instantaneously and accurately rotate regardless of the difference in the shape and characteristics of the vanes of the turbocharger. An object of the present invention is to provide a turbocharger rotation detection device capable of detecting a speed.

The present invention relates to a turbocharger rotation speed detection device for detecting the rotation speed of a turbocharger mounted on an engine, and the above object of the present invention is from a turbo sensor disposed in the vicinity of a compressor vane of the turbocharger. This is achieved by including a peak detection circuit that detects the peak of the detection signal, and an instantaneous rotation speed calculation circuit that calculates the instantaneous rotation speed of the turbocharger based on the peak signal detected by the peak detection circuit.

  The object of the present invention is that the turbo sensor is an eddy current sensor, or that the instantaneous rotational speed is calculated each time the peak is detected, or that the peak of the detection signal is detected. The detection is performed based on the comparison of the time series sampling values with respect to the detection signal, or the time series sampling values are compared at least three times to determine the peak. This is achieved more effectively.

  According to the turbocharger rotational speed detection device of the present invention, the peak of the waveform corresponding to each vane of the compressor is detected, and the instantaneous rotational speed is detected based on the pulse interval of the pulse train corresponding to the peak. The instantaneous rotation speed of the turbocharger can be accurately and reliably detected without being affected by the tolerance.

It is a partial cross section figure showing an example of structure of a general turbocharger. FIG. 3 is a structural diagram showing a connection relationship among a turbine wheel, a turbo shaft, and a compressor wheel. It is a perspective view which shows an example of the compressor provided with the air inlet and the air outlet. It is a perspective view which shows the attachment structure of a turbocharger rotation sensor. It is sectional drawing which shows the attachment structure of a turbocharger rotation sensor. It is a block diagram which shows an example of the detection circuit of a turbocharger rotation sensor. It is a wave form diagram which shows an example of the output waveform of a turbocharger rotation sensor. It is a schematic diagram which shows a part of relationship between the output waveform of a turbocharger rotation sensor, and a threshold value in detail. It is a wave form diagram which shows an example of the binarized waveform. It is a characteristic view which shows an example of the machine difference of the output waveform of a turbocharger rotation sensor. It is a wave form diagram explaining the measurement principle of this invention. It is a wave form diagram which shows an example of the binarized waveform. It is a block diagram which shows the structural example of this invention. It is a flowchart which shows the operation example of this invention. It is a flowchart for demonstrating the detection of a peak. It is a characteristic view which shows an example of the tolerance of this invention.

  In the present invention, the detection waveform of the compressor vane of the turbocharger is binarized using a predetermined threshold value, and the instantaneous rotation speed is not measured from the pulse interval, but the detection waveform corresponding to each vane as shown in FIG. .., And the instantaneous rotational speed is detected based on the pulse interval ΔTn of the pulse train as shown in FIG. 12 corresponding to the peaks PK1, PK2, PK3,. That is, by measuring the time interval between the peaks PK1, PK2, PK3,..., The waveform until the vane detection waveform for detecting the instantaneous rotational speed for each vane reaches the peaks PK1, PK2, PK3,. Are affected by differences in vane thickness and shape, but the positions of the peaks PK1, PK2, PK3,... Are not affected by tolerances. Therefore, the instantaneous rotation speed of the turbocharger can be accurately detected by measuring the time interval between the peaks PK1, PK2, PK3,.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 13 shows a configuration example of the present invention corresponding to FIG. 6. A peak detection circuit 120 for detecting the peak of the vane detection signal AM from the amplifier 112 and a peak train of peaks detected by the peak detection circuit 120 are shown. And an instantaneous rotation speed calculation circuit 130 for calculating the instantaneous rotation speed SR for each peak based on PS. That is, in the present invention, the instantaneous rotational speed SR can be obtained for each peak of the vane detection signal AM, and this instantaneous rotational speed SR can be used for engine control and turbocharger control.

  In such a configuration, an operation example of the present invention will be described with reference to the flowchart of FIG. 14 and the waveform diagram of FIG.

  First, waiting for the vane detection signal AM to become positive (step S1), the previous sampling value stored in the memory (not shown) is cleared (step S2), and until a predetermined time, that is, the sampling time is reached. Wait (step S3).

  When the predetermined time has elapsed and the sampling time is reached (time t1 in FIG. 15), the vane detection signal AM is sampled (step S10), and the sampling value P1 is stored in the memory (step S11). Then, it is determined whether or not the sampling value P1 is equal to or greater than the previous sampling value (step S12), but since the sampling value P1 is equal to or greater than the previous sampling value this time, the next sampling time (in FIG. 15). Sampling is performed at time t2) (step S13), and the sampling value P2 is stored in the memory (step S14). Then, the process returns to step S12, and it is determined whether or not the sampling value P2 is equal to or more than the previous sampling value P1 (step S12). Such a sampling and the comparison of the previous value are repeated.

  In comparison with such sampling, the sampling value P6 at the time point t6 is larger than the sampling value P5 at the time point t5, and the sampling value P7 at the time point t7 is smaller than the sampling value P6 at the time point t6. The peak value is confirmed (step S20), and the peak value P6 (including time) is stored in the memory (step S21).

  In this example, when the current sampling value is smaller than the previous sampling value, the previous sampling value is determined to be the peak value in this example, but the detected waveform is once reduced and then increased again. Is also envisaged. for that reason. If the number of times the current sampling value is smaller than the previous sampling value continues, for example, n (integer greater than or equal to 2) times, if the previous sampling value is determined as the peak value, more accurate peak detection is possible. . It is desirable to determine the peak with at least three samplings.

When the peak of the detected waveform is determined, the time ΔTn [s] between the peaks is obtained, and the instantaneous rotational speed SR is calculated from the known number of vanes M by the following formula 1 (step S30).
(Equation 1)
60 / (ΔTn · M) [rpm]

The instantaneous rotational speed SR is calculated every time a new peak is determined. The instantaneous rotational speed SR is used for controlling the engine and the turbocharger.

  According to the present invention, the peak of the waveform corresponding to each vane of the compressor is detected, and the instantaneous rotation speed is detected based on the pulse interval of the pulse train corresponding to the peak, so that it is not affected by the tolerance. The instantaneous rotation speed of the turbocharger can be detected accurately and reliably. By detecting the peak, the tolerance becomes substantially uniform for each vane as shown in FIG.

  In the above description, the peak of the pulse is detected on the positive side of the detected waveform, but the same applies to the negative side.

DESCRIPTION OF SYMBOLS 10 Turbocharger 11 Turbo shaft 13 Housing 14 Bearing 20 Turbine 21 Turbine wheel 22 Turbine inlet 23 Turbine outlet 24 Turbine housing 30 Compressor 31 Compressor wheel 32 Air inlet 33 Air outlet 37 Compressor housing 100B Projection type eddy current sensor 110 Resonance circuit 111 Detection circuit 112 Amplifier 113 Binary circuit (A / D conversion circuit)
114 Dividing circuit 115 Rotation speed detecting circuit (counter)
120 peak detection circuit 130 instantaneous rotation speed calculation circuit

Claims (5)

In a turbocharger rotation speed detection device that detects the rotation speed of a turbocharger attached to an engine,
A peak detection circuit for detecting a peak of a detection signal from a turbo sensor disposed close to the compressor vane of the turbocharger;
An instantaneous rotation speed calculation circuit for calculating an instantaneous rotation speed of the turbocharger based on a peak signal detected by the peak detection circuit;
A turbocharger rotation speed detection device comprising: The turbocharger rotation speed detection device according to claim 1, wherein the turbo sensor is an eddy current sensor. The turbocharger rotation speed detection device according to claim 1 or 2, wherein the instantaneous rotation speed is calculated each time the peak is detected. The turbocharger rotation speed detection device according to any one of claims 1 to 3, wherein detection of a peak of the detection signal is performed based on a magnitude comparison of time-series sampling values with respect to the detection signal. The turbocharger rotation speed detection device according to claim 4, wherein the peak is determined by comparing the time-series sampling values at least three times.