JP4821555B2 - Simulated combustion shaker - Google Patents

Description

  The present invention relates to a simulated combustion vibration device, and more particularly to a vibration device for artificially creating engine noise.

  Engine noise is a phenomenon in which vibrations generated by various excitation sources in an engine component are propagated from the engine surface to air as a medium and radiated as sound waves.

  The excitation source in this case can be broadly classified into a combustion excitation force acting by combustion in the cylinder and a mechanical excitation force. Here, the noise generated by the combustion excitation force is referred to as combustion noise, and the noise generated by the mechanical excitation force is referred to as machine noise.

  When reducing combustion noise, there are two methods: a method of reducing the combustion excitation force itself and a method of improving the vibration response of the engine structure to the combustion excitation force. When experimentally examining the improvement of vibration response, which is the latter method, the main engine component for the radiation characteristics of combustion noise is the cylinder block. As a result, a method of obtaining an evaluation result based on an integrated value of block surface vibrations and a vibration visualization result by mode analysis is employed.

This hammering test is a method of measuring vibration generated by a vibration meter attached to an object by hitting the object (engine) with a hammer having a force sensor at the tip. The output signal of the force sensor and the output signal of the vibrometer are taken into the analysis device, and the transfer function between the applied force and the actually generated vibration (generally vibration acceleration) is measured. This can be thought of as a vibration response normalized by unit input (for example, 1 (m / s ² ) / N). By integrating the transfer function measured over the entire surface of the object, the noise radiation of the object is obtained. It can be considered a characteristic. This is an index indicating whether the noise is easily emitted.

  However, in the case of such a hammering test, during actual operation, engine internal components such as pistons and crankshafts and peripheral components such as cylinder heads and oil pans are combined to form an engine assembly. However, the vibration characteristics of the cylinder block differ between the single product state and the assembly state, and the improvement effect studied in the single product state may not be sufficiently exhibited in the actual operation performed in the assembly state.

  In addition, when performing a vibration test for combustion noise in the engine assembly state, it is appropriate to vibrate the piston upper surface and the cylinder head lower surface on which the combustion pressure acts during actual operation. It was virtually impossible to vibrate the bottom of the head with a hammer.

  Therefore, there is a known power train transmission characteristic measurement method and device that seeks high-accuracy transmission measurements that are close to the actual operating state of the power train, and that achieves both a reduction in powertrain weight and reduction of radiated sound at a high level. (For example, see Patent Document 1).

  In Patent Document 1, the power train is composed of at least a cylinder block and a cylinder head. The cylinder block includes a piston, a connecting rod, a crankshaft, and a lower block, and the cylinder head includes a cylinder block. An injector insertion hole penetrating from the top to the bottom of the head is provided, and in the state where the cylinder head is mounted above the cylinder block, the piston is set at a position near the top dead center, and a vibration device Is mounted in the injector insertion hole to vibrate the piston head, and the transfer characteristic of any part of the powertrain is obtained based on the vibration acceleration measured by the acceleration sensor when the piston head is vibrated.

On the other hand, in order to be able to reproduce the vibration noise characteristics of the engine basic structure with respect to combustion excitation input in a systematic, efficient and safe manner, a hydraulic excitation type is used by a control signal stored in advance for the combustion chamber of the engine filled with liquid There is known a simulated combustion excitation device that vibrates by both an actuator and a piezoelectric excitation type actuator and reproduces the actual in-cylinder pressure in a pseudo manner (see, for example, Patent Document 2).
JP 2004-53485 A JP-A-11-94690

  In Patent Document 1 described above, only the upper surface of the piston is vibrated. In other words, the main vibration transmission path is transmitted through the piston, connecting rod, crankshaft, and cylinder block. However, it is known that the cylinder head affects the vibration characteristics of the engine assembly depending on the engine. Such a phenomenon is not considered.

  In the case of this Patent Document 1, a relatively large vibration exciter is supported from the outside of the engine with respect to the components of the main vibration transmission path described above, and is vibrated while being pressed against the piston with a constant load. For this reason, there is a problem that the influence of adding the excitation device to the vibration characteristics is relatively large, and the error becomes large with respect to reproduction of the actual characteristics.

  Furthermore, in the case of the above-mentioned Patent Document 1, since the vibration force is detected inside the vibration device, the vibration characteristic of the vibration rod between the vibration device and the engine is not taken into consideration. However, it is impossible to accurately detect the excitation force applied to the engine, and the transfer function between the applied excitation force and vibration cannot be measured accurately.

  Further, Patent Document 1 has a problem that since the rotation is fixed by the flywheel, the influence on the vibration of the assembly including the flywheel and the crank pulley is relatively large.

  In addition, Patent Document 2 described above uses both a hydraulic shaker and a piezoelectric element to perform pressure excitation using light oil filled in the combustion chamber as a working fluid, and uses a physically large hydraulic shaker. There was a problem that had to be done.

  Further, the above-mentioned Patent Document 2 has an actuator arranged on the cylinder head, the hydraulic exciter and the fixed block are relatively large, and the scale of change due to the arrangement of the exciting piston is relatively large. was there.

  Accordingly, the present invention has a small vibration portion, can vibrate not only the upper surface of the piston but also the lower surface of the cylinder head, and has excellent response characteristics that can detect the vibration force by the amount of contact with the engine. An object of the present invention is to provide a simple pseudo combustion excitation device.

[1] In order to achieve the above object, a simulated combustion excitation apparatus according to the present invention is first provided in a combustion chamber of a piston, and includes an excitation unit composed of a piezoelectric element and a force sensor, An excitation signal generator for applying an excitation signal of an in-cylinder pressure waveform for exciting the bottom surface of the cylinder head covering the bottom portion and the combustion chamber in the vertical direction of the piston to the piezo element. sometimes the output signal from the force sensor is indicative of the combustion vibration force.

  That is, the present invention is an apparatus that makes it possible to evaluate and analyze the response characteristics of an engine assembly with respect to a combustion excitation force, and is a piezo that has a small and good responsiveness in the excitation portion and has a large and stable excitation force. It is characterized by using an element. Changes in engine parts for installing this piezo element are limited to the combustion part of the piston, and the main structural parts such as the connecting rod, crankshaft, cylinder block, cylinder head, oil pan, etc., which are the transmission path of the combustion excitation force Can be left unchanged.

  Then, when the excitation signal of the in-cylinder pressure waveform is given to the piezo element from the force sensor that constitutes the excitation unit together with the piezo element (when oscillating), the output signal from the force sensor indicates the combustion excitation force Is.

[2] In the above case, the rotation of the crankshaft at the rear end of the distant transmission is provided by further providing a stopper for fixing the piston at a position near its top dead center by restricting the rotation of the crankshaft at the rear end of the transmission Is restrained, the influence on the crank system vibration is reduced, and a response characteristic closer to that in actual operation can be obtained .

[3] The piezo element in [2] is placed on the bottom of the combustion chamber and coupled to the force sensor via an adapter, and the piezo element and the force sensor are attached to the bottom of the combustion chamber and the cylinder head. By being sandwiched and fixed, it is not necessary to bond the excitation unit to the upper surface of the piston and the lower surface of the cylinder head.

 [4] Furthermore, a preload applied to the piezo element during the fixing is adjusted between the bottom of the combustion chamber and the excitation unit by adjusting an amount of projection of the excitation unit from the upper surface of the piston. A member for adjustment can also be provided.

 [5] Further, in the above case, a plurality of vibration sensors attached around the engine, and output signals at the time of excitation of the force sensor and the vibration sensor are inputted, and combustion excitation force / And an arithmetic unit for obtaining acoustic power.

  As a result, the excitation force is detected at the contact portion with the engine, and the force sensor and piezo element have sufficient rigidity (hard), so the forces acting on the cylinder head side and the piston side are equal, It is possible to accurately detect the excitation force actually applied to the engine with the installed force sensor. Therefore, it is possible to accurately measure, evaluate and analyze the transfer function (response characteristic) of the engine assembly due to the applied excitation force and vibration.

  According to the present invention, it is possible to reproduce the transmission characteristics of the combustion excitation force during actual operation inside the engine and the noise radiation characteristics due to vibrations on the outer surface of the engine.

  Therefore, the vibration characteristics of the engine component in the engine assembly state can be investigated, or the vibration reduction effect by changing the vibration characteristics of the engine component can be confirmed. In particular, since the moving parts inside the engine are stopped, it is relatively easy to measure data on these engine parts, which are difficult to measure in the actual work test.

  Further, the noise generated as a result of applying the combustion excitation force to the engine assembly is close to the actual engine noise in terms of hearing, and can also be used for analysis of sound quality with respect to the combustion noise. In particular, the combustion excitation force given can be applied not only to the actually measured in-cylinder pressure waveform, but also to the in-cylinder pressure waveform obtained from numerical simulation as an excitation signal. Can be realized without.

  FIG. 1 shows an embodiment of a simulated combustion excitation apparatus according to the present invention. FIG. 1A is a schematic cross-sectional view of the engine 1, in which a cylinder head 3 is coupled to a cylinder block 2 with a head bolt 3a. In addition, the piston 4 moves up and down in the cylinder block 2, and the excitation unit 5 is installed in the combustion chamber 4 a provided in the upper part of the piston 4. The piston 4 is coupled to the crankshaft 7 via a connecting rod 6. A crank arm 8 is provided between adjacent connecting rods 6. An oil pan 9 for engine oil is provided below the cylinder block 2.

  FIG. 1 (2) is an enlarged view of the vibration portion 5 provided in the combustion chamber 4a of the piston 4 shown in FIG. 1 (1). In other words, the vibration unit 5 has an expansion / contraction type piezo element 11 bonded to the adapter 12, and a force sensor 13 and a preloading disk 14 are further fixed to the adapter 12 with bolts 15. The side is placed on the bottom of the combustion chamber 4a. The bottom of the combustion chamber 4a is provided with a recess 4b for preventing the piezo element 11 from shifting as shown, and when the vibration unit 5 is placed on the combustion chamber 4a, a preloading disk 14 is provided. Since the upper surface of the cylinder head 3 protrudes slightly from the upper surface of the cylinder head gasket 16, when the cylinder head 3 is put on the preloading disk 14 as shown in FIG. Since it is tightened, the piezo element 11 is practically fixed even if it is not bonded to the piston 4.

  When the cylinder head 3 is mounted between the piston 4 and the vibration part 5 by adjusting the amount of protrusion of the vibration part 5 from the upper surface of the cylinder head gasket 16 by inserting a shim (not shown). The load (preload) applied to the piezo element 11 can be adjusted.

  That is, the preload to the piezo element 11 by adjusting the protrusion amount of the vibration unit 5 is actually performed by the force sensor 13 attached to the vibration unit 5 when the head bolt 3a of the cylinder head 3 is fastened with a regular assembly torque. By monitoring the load acting on the piezoelectric element 11, it can be arbitrarily set within a range not exceeding the maximum compressive load of the piezo element 11.

  In such a simulated combustion excitation device, it is necessary to prevent the crankshaft 7 from rotating, but in order to minimize the influence on the vibration characteristics of the crankshaft 7, as shown in FIG. A restraining lever 23 is attached to a flange 22 provided on the rear surface 21 of the transmission far from the shaft 7, and the positive rotation of the restraining lever 23 is restrained by a stopper 25 provided on a stopper fixing jig 24. The crank angle at the time of fixing may be a typical ignition timing of the test engine, but can be arbitrarily changed within a range of realistic ignition timing.

  FIG. 3 shows a system for determining response characteristics with respect to the simulated combustion excitation force by actually driving the simulated combustion excitation device shown in FIG.

  Therefore, a personal computer 31 and a drive amplifier 32 are connected to the piezoelectric element 11 of the vibration unit 5 shown in FIG. 1 (2), and a spectrum analyzer (FFT) 33 is connected to the force sensor 13. Note that the wiring is led out of the engine 1 from a valve guide (not shown) of the cylinder head 3.

  That is, a signal corresponding to the in-cylinder pressure waveform of the piston 4 is stored in the personal computer 31, and this is given to the drive amplifier 32 as an analog signal SIG1. Receiving this, the drive amplifier 32 amplifies the analog signal SIG1 and supplies it to the Piedo element 11 as the excitation signal SIG2. As this excitation signal S1G2, a signal obtained by converting an in-cylinder pressure waveform measured by an actual engine or obtained from a numerical simulation into a voltage value that can be input to the drive amplifier 32 is used. In this manner, the bottom of the combustion chamber 4a of the piston 4 and the lower surface of the cylinder head 3 are vibrated in the vertical direction of the piston by the piezo element 11 that expands and contracts in proportion to the supply voltage.

  At this time, the combustion excitation force signal SIG3 output from the force sensor 13 is given to the spectrum analyzer 33, and vibration acceleration from vibration sensors (for example, 127 pieces) provided around the engine 1 is supplied to the spectrum analyzer 33. By inputting the signal, the spectrum analyzer 33 can output a response characteristic SA (Structure Attenuation: combustion excitation force / acoustic power) with respect to the combustion excitation force in an engine assembly state equivalent to that during actual operation.

  FIG. 4 (1) shows an installation diagram of the above vibration sensor. In this example, on the right side of the engine shown in FIG. 4 (a), 9 × 5 = 45 vibration sensors 10 with respect to the cylinder block 2. The cylinder head 3 is provided with nine vibration sensors 10, and the oil pan 9 is also provided with two vibration sensors 10. The engine right side is the same as the engine left side shown in FIG.

  Further, as shown in FIG. 4B, ten vibration sensors 10 are provided on the cylinder block 2 and one vibration sensor 10 is provided on the oil pan 9 on the front surface of the engine. Furthermore, as shown in FIG. 4 (c), two vibration sensors 10 are provided in the shallow oil pan 9_1 on the bottom surface of the engine, and two vibration sensors 10 are provided in the direction shown in the figure in the deep oil pan 9_2. The sensor 10 is provided, and a total of 127 vibration sensors 10 are provided in the engine 1.

Therefore, in this way, the spectrum analyzer 33 that receives the combustion excitation force signal SIG3 from the force sensor 13 and 127 actually measured surface vibration accelerations from the vibration sensor 10 is expressed by the following equation:
Sound power = σ * ρc * V ² * S ・ ・ ・ ・ ・ ・ Equation (1)
σ: Radiation efficiency ρc: Characteristic impedance of air [Pa · s / m]
V: Measured surface vibration velocity [m / s] (integrated acceleration detected by the sensor)
S: Engine surface area [m ² ]
Thus, the sound power can be obtained. Therefore, the response characteristic SA can be obtained as the combustion excitation force / acoustic power using the combustion excitation force signal SIG3 of the force sensor 13 and the measured surface vibration acceleration from the 127 vibration sensors 10.

  When obtaining the response characteristic SA in the conventional practical test, as shown in FIG. 4 (2), the five microphones provided on the side of the measurement rectangular parallelepiped 40 of 2a × 2b × 2h with respect to the engine 1 From 1 to # 5, acoustic power = average sound pressure in 5 directions * surface area of the measurement cuboid and combustion excitation force = measured in-cylinder pressure * calculation of combustion excitation force / acoustic power by calculating bore cross-sectional area is doing.

  As a result, as shown in the graph of FIG. 5, in contrast to the SA response characteristic of the present invention using the vibration sensor shown in FIG. 4 (1), the SA response characteristic by the conventional operation shown in FIG. It was confirmed that the combustion pseudo noise according to the present invention can be reproduced well including the frequency characteristics.

  It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent that various modifications can be made by those skilled in the art based on the description of the scope of claims.

It is a schematic sectional drawing of the engine part used with the simulated combustion vibration apparatus which concerns on this invention. FIG. 2 is a front view showing a state in which a stopper is provided at a rear end portion of a distant transmission with respect to the engine assembly of the present invention shown in FIG. FIG. 2 is a view showing a system system for actually applying an excitation signal to the pseudo combustion excitation apparatus according to the present invention shown in FIG. It is the figure which showed the example of installation of the vibration sensor used when calculating | requiring the response characteristic in the pseudo | simulation combustion vibration apparatus which concerns on this invention, and the example of the conventional actual test. It is the graph which compared the SA response characteristic by this invention and the conventional actual driving | operation.

Explanation of symbols

1 engine
2 Cylinder block
3 Cylinder head
4 piston
4a Combustion chamber
5 Excitation unit
6 Connecting rod
7 Crankshaft
8 Crank arm
9 Oil pan
10 Vibration sensor
11 Piezo elements
12 Adapter
13 Force sensor
14 Preloading disc
15 volts
16 Cylinder head gasket
21 Rear of transmission
22 Transmission rear flange
23 Restraint lever
24 Stopper fixing jig
25 Stopper
31 PC
32 drive amplifier
33 Spectrum analyzer In the figure, the same symbols indicate the same or corresponding parts.

Claims (4)

An excitation unit provided in the combustion chamber of the piston and configured by a piezoelectric element and a force sensor;
An excitation signal generator for giving an excitation signal of an in-cylinder pressure waveform to the piezoelectric element for exciting the bottom of the combustion chamber and the lower surface of the cylinder head covering the combustion chamber in the vertical direction of the piston;
An output signal from the force sensor at the time of the excitation indicates a combustion excitation force ,
A pseudo combustion excitation device , further comprising a stopper for restraining the rotation of the crankshaft at the rear end of the transmission to fix the piston at a position near its top dead center . In claim 1,
The piezo element is mounted on the bottom of the combustion chamber and coupled to the force sensor via an adapter, and the piezo element and the force sensor are sandwiched and fixed between the bottom of the combustion chamber and the cylinder head. A simulated combustion vibration device. In claim 1 or 2,
A member for adjusting a preload applied to the piezo element at the time of fixing between the bottom portion of the combustion chamber and the vibration portion by adjusting an amount of protrusion of the vibration portion from the upper surface of the piston. A pseudo combustion excitation device characterized by further comprising: In any one of Claims 1-3,
A plurality of vibration sensors attached to the periphery of the engine, and an arithmetic device for obtaining combustion excitation force / acoustic power as an excitation response characteristic by inputting each output signal at the time of excitation of the force sensor and the vibration sensor pseudo combustion vibration device characterized by comprising.

Images