JP2015125074A - Cylinder block rigidity evaluation device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems in which, in a conventional hammering test, a cylinder block rigidity evaluation cannot be performed in an engine operation state, hence excessive strength must be applied to a cylinder block for safety, and the weight reduction and cost reduction are inhibited.SOLUTION: The cylinder block rigidity evaluation device includes: a pressure sensor for detecting an engine combustion pressure of an engine to be evaluated; a microphone for detecting the vibration of a cylinder block of the engine to be evaluated; and a controller for calculating a resonance frequency using an output from the pressure sensor as the input signal and an output from the microphone as the output signal.

Description

  The present invention relates to a cylinder block rigidity evaluation apparatus and a cylinder block rigidity evaluation method, and more particularly to an apparatus for evaluating the rigidity of a cylinder block of an operating engine.

  A cylinder block is a component that constitutes a combustion chamber that is exposed to the highest temperature and pressure among engine components, and is required to have high heat resistance and pressure resistance. Therefore, high rigidity is required to satisfy these characteristics. However, the relationship between the rigidity of the cylinder block and the heat resistance and pressure resistance is not clear. Safety side design has been carried out based on the past results and the result of the rigidity test of the cylinder block alone.

  Patent Document 1 discloses a test method using a cylinder block alone. In the invention disclosed herein, a test object such as a cylinder block to which an acceleration sensor is attached is vibrated by an impulse hammer to which a force detection sensor is attached, and a vibration test is performed. This is a vibration characteristic analyzer for identifying the mode characteristics (modal parameters such as natural frequency, mode damping ratio, natural mode shape) of the DUT.

  Patent Document 1 discloses a vibration characteristic analysis apparatus including an arithmetic unit that identifies a mode characteristic from frequency response function data obtained by receiving an output signal from a force detection sensor or the like. Is automatically divided into the target areas. As a result, there is a description that the number of eigenmodes in each divided region can be made equal to or less than the maximum number of eigenmodes defined so that the calculation time and storage capacity required for identification can be reduced.

Japanese Patent Laid-Open No. 10-0387748 (Patent No. 3601907)

  In the conventional cylinder block rigidity inspection, since it is necessary to attach a vibration device to the cylinder block, it is not possible to evaluate the rigidity of the cylinder block during operation at a high temperature and high pressure. Moreover, the bracket etc. which fix an auxiliary machine are attached at the time of actual use of an engine, and the hammering test like patent document 1 was not able to be performed. In the test with a single cylinder block, the actual use situation cannot be grasped, and therefore, an excessive strength is given to the cylinder block for safety reasons, and the weight reduction and cost reduction are hindered.

  The present invention is a cylinder block rigidity evaluation device and a cylinder block rigidity evaluation method conceived in view of the above-described problems, and uses combustion pressure as a vibration source.

More specifically, the cylinder block rigidity evaluation apparatus according to the present invention is:
A pressure sensor for detecting the engine combustion pressure of the engine under evaluation;
A microphone for detecting vibration of a cylinder block of the engine to be evaluated;
And a controller that calculates a resonance frequency using an output from the pressure sensor as an input signal and an output from the microphone as an output signal.

Further, the cylinder block rigidity evaluation method according to the present invention includes:
Detecting the engine combustion pressure of the engine under evaluation;
Detecting vibration of a cylinder block of the engine to be evaluated;
Calculating a resonance frequency using the signal due to the engine combustion pressure as an input signal and the signal due to the vibration of the cylinder block as an output signal;
The method includes evaluating a cylinder block rigidity of the engine to be evaluated based on a reference resonance frequency that is a resonance frequency of a reference engine and the resonance frequency.

  When using hammer excitation, the engine could not be inspected while it was running. However, according to the cylinder block rigidity evaluation apparatus according to the present invention, the combustion pressure of the combustion chamber itself is used as a vibration source, so that the cylinder block rigidity can be evaluated even when the engine is in operation. Further, by using this evaluation, the cylinder block strength can be tuned in a state where it is actually used. Therefore, as compared with the case where the tuning of the strength is performed with a single cylinder block, there is no need to increase the strength, and the engine can be reduced in weight and cost.

It is a figure which shows the structure of the cylinder block rigidity evaluation apparatus which concerns on this invention. It is a figure explaining the principle of the cylinder block rigidity evaluation method based on this invention.

  A cylinder block rigidity evaluation apparatus according to the present invention will be described below with reference to the drawings. The following description exemplifies an embodiment of the present invention, and changes within the scope of the present invention are included in the technical scope of the present invention without departing from the spirit of the present invention. Needless to say.

  FIG. 1 shows the configuration of a cylinder block stiffness evaluation apparatus 1 according to the present invention. The engine to be evaluated 9 to be inspected may be mounted only on the engine to be evaluated 9 on a fixed base with a vibration isolator, or may be fixed to the vehicle body chassis.

  A pressure sensor 10 is attached to the engine 9 to be evaluated in the combustion chamber 9a. A microphone 12 is arranged around the engine 9 to be evaluated. This is because the total engine radiated sound Aa generated by the engine 9 to be evaluated is measured. The microphone 12 may be a piezoelectric pickup sensor 12a or a G sensor 12b that is directly attached to the cylinder block 9b of the engine 9 to be evaluated. It may be understood that the microphone 12 includes these. This is because it is only necessary to detect the vibration of the cylinder block 9b. Moreover, the microphone 12 may not be only one place. The pressure sensor 10 and the microphone 12 are connected to the analysis device 20 via amplifiers 14a and 14b, respectively.

  Here, the principle of cylinder block rigidity evaluation according to the present invention will be described with reference to FIG. The outline of the rigidity evaluation according to the present invention uses that the signal of the knock component generated in the engine 9 to be evaluated becomes the total engine radiated sound via the cylinder block. In other words, if the transfer function of the cylinder block is applied to the knock component signal that has been subjected to Laplace conversion, the result is a Laplace conversion of the total engine radiated sound signal (FIG. 2A).

  Now, since the knock component signal Sn and the total engine radiated sound signal Sa can be measured, these signals are subjected to Laplace transform to obtain an input signal and an output signal, thereby obtaining the transfer function G of the cylinder block. The resonance frequency fr of the cylinder block is obtained from this transfer function G and used as the basis for evaluation.

  The details will be described below. The signal Sn of the pressure sensor 10 is a signal related to the combustion pressure in the combustion chamber 9a. This signal Sn includes a low-frequency pressure related to the explosion in the combustion chamber 9a. FIG. 2B shows a conceptual diagram of the pressure in the combustion chamber 9a. The horizontal axis is the crankshaft angle, and TDC (Top Dead Center) indicates the top dead center. The vertical axis represents pressure.

  The pressure in the combustion chamber 9a becomes maximum at the top dead center. When the ignition timing is adjusted so as to cause knocking, knocking starts after the top dead center. Here, a signal 50 corresponding to the knock component appears.

  Since the waveform as the excitation signal is a knock component, the signal Sn is passed through a high-pass filter (HPF). The cut-off frequency of the high-pass filter may be any frequency at which the frequency of the signal 50 corresponding to the knock component passes. More specifically, it is preferably set to about 5 kHz. A signal after passing through the high-pass filter is defined as a signal FSn. A conceptual diagram of the signal FSn is shown in FIG. The horizontal axis is the crankshaft angle, and the vertical axis is the pressure. In addition, TDC is shown with a dotted line like FIG.2 (b).

  Next, Laplace transform or Fourier transform is performed on the signal FSn. Since the rigidity evaluation apparatus according to the present invention is intended to obtain the resonance frequency fr, it may be a Fourier transform. Hereinafter, in this specification, the Laplace transform may include a Fourier transform. The Laplace converted signal FSn is defined as a signal LFSn. This signal LFSn becomes an input signal when the transfer function G is obtained.

  On the other hand, the signal Sa measured by the microphone 12 is a signal corresponding to the total engine radiation sound Aa. FIG. 2D shows a conceptual diagram of the signal Sa. The horizontal axis represents time, and the vertical axis represents sound pressure. Here, since the vibration related to the cylinder block rigidity is considered to exist in the high frequency component, the signal Sa is passed through the high-pass filter (HPF), and only the high frequency component is extracted. The signal after the high pass filter is defined as a signal FSa. FIG. 2E shows a conceptual diagram of the signal FSa. The horizontal axis represents time, and the vertical axis represents sound pressure.

  Next, Laplace transform is applied to the signal FSa. The converted signal is defined as a signal LFSa. The signal LFSa becomes an output signal when the transfer function G is obtained.

  Next, the transfer function G is obtained from the signal LFSn as an input signal and the signal LFSa as a response signal. Specifically, the transfer function G is obtained as “signal LFSa / signal LFSn”. Since this transfer function G is related to the frequency and the amplitude ratio, the frequency at the point of the peak value can be regarded as the resonance frequency fr. A conceptual diagram of the transfer function G is shown in FIG. The horizontal axis is frequency and the vertical axis is amplitude ratio.

  Further, for the reference engine, the resonance frequency fr obtained by performing the same measurement is prepared in advance as the reference resonance frequency sfr. Then, the cylinder block rigidity of the engine 9 to be evaluated is evaluated based on the resonance frequency fr of the engine 9 to be evaluated and the reference resonance frequency sfr.

  With reference to FIG. 1 again, the inside of the analyzer 20 will be described. The amplifier 14a is connected to the high pass filter 16a. The output of the amplifier 14a may be passed through the A / D converter 15a and the subsequent signal may be digitally processed. The input signal of the high pass filter 16a is a signal Sn. The output (signal FSn) of the high-pass filter 16a is connected to the calculator 22a. The computing unit 22a performs Laplace transform on the input signal. The output of the arithmetic unit 22a is the signal LFSn.

  On the other hand, the output of the amplifier 14b is connected to the high-pass filter 16b. Note that the output of the amplifier 14b may also be passed through the A / D converter 15b and the subsequent signal may be digitally processed. The output (signal FSa) of the high pass filter 16b is connected to the calculator 22b. The calculator 22b also performs Laplace transform on the input signal. The output of the calculator 22b is a signal LFSa. The outputs (signal LFSn and signal LFSa) of the calculator 22a and calculator 22b are connected to a divider 26.

  The output of the divider 26 is a transfer function G having the signal LFSn from the pressure sensor 10 as an input signal and the signal LFSa from the microphone 12 as an output signal. This transfer function G may be displayed on the display 28 as a frequency.

  When the transfer function G is obtained, a frequency having a peak value is obtained by the peak detector 32 and set as the resonance frequency fr. Further, in the analysis device 20, the reference resonance frequency sfr of the engine serving as a reference is stored in the memory 42. The reference engine is the resonance frequency fr when an engine with a proven track record as cylinder block stiffness is measured by the cylinder block stiffness evaluation apparatus 1 according to the present invention. The evaluation calculator 34 evaluates the cylinder block rigidity of the engine 9 to be evaluated based on the resonance frequency fr and the reference resonance frequency sfr.

  The evaluation method is not particularly limited. For example, the ratio between the resonance frequency fr and the reference resonance frequency sfr may be obtained and used as the evaluation value EV of the cylinder block rigidity of the engine 9 to be evaluated.

  When the A / D converters 15a and 15b are installed after the amplifiers 14a and 14b, the analysis apparatus 20 can be processed in software. Therefore, the high pass filters 16a and 16b, the calculators 22a and 22b, the divider 26, the peak detector 32, and the evaluation calculator 34 may be processed by the controller 40 as software. In particular, the controller 40 may determine that the resonance frequency fr is obtained and the evaluation value EV is calculated.

  As described above, the cylinder block stiffness evaluation apparatus 1 according to the present invention uses the knock component generated in the combustion chamber 9a as an excitation signal, so that it is assembled as an engine and an auxiliary machine is attached via a flange. It is possible to evaluate the cylinder block rigidity in a used state. Therefore, an excessively rigid cylinder block structure can be avoided, and a lighter and fuel-efficient engine can be provided.

  The present invention can be suitably used for the development of a lightweight and fuel-efficient engine.

DESCRIPTION OF SYMBOLS 1 Cylinder block rigidity evaluation apparatus 9 Evaluated engine 9a Combustion chamber 9b Cylinder block 10 Pressure sensor 12 Microphone 12a Piezoelectric pick-up sensor 12b G sensor 14a, 14b Amplifier 15a, 15b A / D converter 16a, 16b High pass filter 20 Analysis apparatus 22a, 22b calculator 26 divider 28 indicator 32 peak detector 34 evaluation calculator 40 controller 42 memory 50 signal corresponding to knock component fr resonance frequency sfr reference resonance frequency Aa total engine radiation sound signal Sn combustion pressure Signal signal FSn Signal Sn after high-pass filter
Signal LFSn Signal signal Sa obtained by Laplace conversion of signal FSn Signal signal FSa corresponding to total engine radiated sound Signal Sa after high-pass filter
Signal LFSa Signal FSa Laplace transformed signal G Transfer function

Claims (2)

A pressure sensor for detecting the engine combustion pressure of the engine under evaluation;
A microphone for detecting vibration of a cylinder block of the engine to be evaluated;
A cylinder block stiffness evaluation apparatus comprising: a controller for calculating a resonance frequency using an output from the pressure sensor as an input signal and an output from the microphone as an output signal. Detecting the engine combustion pressure of the engine under evaluation;
Detecting vibration of a cylinder block of the engine to be evaluated;
Calculating a resonance frequency using the signal due to the engine combustion pressure as an input signal and the signal due to the vibration of the cylinder block as an output signal;
A cylinder block stiffness evaluation method comprising: evaluating a cylinder block stiffness of the engine to be evaluated based on a reference resonance frequency that is a resonance frequency of a reference engine and the resonance frequency.