JPH0312522A - Resonance detector - Google Patents

Abstract

PURPOSE:To securely and easily detect resonance generated in a duct as temperature variation by providing a temperature sensor which is disposed on a position where gas particles are in large motion through the resonance in the duct and a heating part or cooling part which is disposed close to the temperature sensor and relatively high or low in temperature to the temperature in the duct. CONSTITUTION:The temperature sensor 3 is disposed on the node of the resonance mode of an exhaust pipe 2 and a heater 4 is disposed close to the temperature detection point of the sensor 3. The heater 4 is held at temperature higher than the temperature of exhaust gas close to the sensor 3 and positioned on the downstream side of the sensor 3. When no resonance occurs, the detected temperature of the sensor 3 depends upon the exhaust gas temperature. Then when a resonance mode having its node close to the resonance detection sensor 1 at certain rotating frequency occurs, the behavior of exhaust gas particle becomes active to accelerate the heat exchanger between the sensor and heater 4 and the detected temperature rises temporarily. At the time of deceleration, the detected temperature rises temporarily in resonance similarly. The generation of resonance can be detected from this temperature variation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a resonance detection device for detecting intra-pipe resonance, such as a resonance phenomenon in the exhaust system of an automobile engine.

BACKGROUND OF THE INVENTION For example, when an automobile engine suddenly accelerates when it is not very warm, a very loud metal-like noise may be temporarily generated during the acceleration. This abnormal noise is a high-frequency sound of about 1=10k) Iz, and although the mechanism by which it occurs has not been strictly elucidated, it is known that it occurs when resonance occurs in the exhaust system. It is being In addition, it is particularly likely to occur in exhaust systems with low back pressure suitable for high-output engines. Note that depending on various conditions, this may occur when the engine is decelerating.

To deal with abnormal noises caused by such resonance during transient periods, an exhaust system is designed to suppress the resonance in the exhaust system and prevent the generation of the above abnormal noises by providing a throttle at the node of resonance vibration. A noise reduction device has been proposed by the present applicant and is publicly known (Japanese Utility Model Publication No. 6382022). This is a butterfly valve type throttling mechanism that can be opened and closed at a predetermined position in the exhaust system.By narrowing down the passage area at the nodes of resonance vibration, resistance is provided to the movement of exhaust gas particles, suppressing resonance. be done.

Problems to be Solved by the Invention However, in the conventional example described above, it is not possible to actually detect whether or not resonance is occurring within the exhaust system. Therefore, if the engine rotational speed at which resonance occurs changes due to temperature conditions in the exhaust system, etc., the throttle mechanism cannot be operated at an appropriate timing.

Although it is experimentally possible to detect the presence or absence of actual resonance using a high-precision pressure sensor, it is difficult to detect pressure changes in an exhaust pipe through which high-temperature, high-pressure exhaust flows.
Due to its durability and component cost, it cannot be put to practical use.

Means for Solving the Problems Accordingly, the present invention uses a temperature sensor to detect resonance within a pipe. In other words, the resonance detection device according to the present invention includes a temperature sensor disposed at a position where gas particles move significantly due to resonance in the pipe, and a temperature sensor disposed close to the temperature sensor and whose temperature is lower than the temperature inside the pipe. It is also configured to include a relatively high-temperature heating section or a relatively low-temperature cooling section.

Function: The resonance detection device described above is provided, for example, at a position in the conduit that is a node of the resonance mode. In the absence of resonance,
The influence of the heating section or the cooling section on the temperature sensor is relatively small.

On the other hand, when resonance occurs, gas particles actively move due to resonance at the nodes of the resonance mode. Therefore, heat exchange between the heating section or the cooling section and the temperature sensor is promoted, and the temperature detected by the temperature sensor increases or decreases. This detects that the inside of the pipe is in a resonant state.

Alternatively, a Helmholtz type resonance element may be connected near the position that becomes the antinode of the resonance mode, and the above-mentioned resonance detection device may be provided in the tube.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows an embodiment in which the present invention is configured as a resonance detection sensor 1 for an engine exhaust system, in which a temperature sensor 3 consisting of a thermocouple or a thermistor is placed at a node of the resonance mode of an exhaust pipe 2. An electric heater 4 serving as a heating section is also provided close to the temperature detection point of the temperature sensor 3. The electric heater 4 is always kept at a higher temperature than the exhaust gas temperature near the temperature sensor 3, and is located downstream of the temperature sensor 3 with respect to the flow of exhaust gas indicated by the arrow.

In the above configuration, when resonance is not occurring, the influence of the electric heater 4 on the temperature sensor 3 is very small. Therefore, the temperature detected by the temperature sensor 3 is controlled by the temperature of the exhaust gas flowing from the engine side. Therefore, for example, during acceleration, the detected temperature gradually increases as the rotational speed increases, as shown in FIG. 2(B). If a resonance mode with a node near the resonance detection sensor 1 occurs at a certain rotation speed R1 (see (A) in the same figure), the movement of exhaust gas particles becomes active and the temperature sensor 3 and electric heater 4 heat exchange between the two is promoted, and the detected temperature temporarily increases. Similarly, in the case of deceleration, the detected temperature temporarily increases during resonance. Therefore, the occurrence of resonance can be detected from this temperature change.

In particular, it can be detected before the resonance peak is reached, that is, at the time the resonance starts.

Next, in FIGS. 3 and 4, a small diameter sensor metal tube 5 with both ends open is fixed inside the exhaust pipe 2, and a temperature sensor 3 and an electric heater 4 are housed inside this sensor metal tube 5. An example is shown below.

According to this embodiment, since the heat of the electric heater 4 is not widely diffused, the heat 1 transferred from the electric heater 4 to the temperature sensor 3 during resonance increases, and the detection sensitivity of resonance can be improved accordingly.

In the embodiment shown in FIG. 5, a part of the exhaust pipe 2 is provided with a
A bypass passage 6 is formed in parallel with the
A temperature sensor 3 and an electric heater 4 are housed inside.

In this embodiment, the temperature sensor 3 and the electric heater 4 are not directly affected by shock waves caused by foreign objects, afterburn, etc. flowing through the exhaust pipe 2, thereby preventing damage thereto.

Next, FIG. 6 shows an embodiment in which the tip of a heat pipe 7 serving as a cooling section is disposed close to the temperature sensor 3. The other end of the heat pipe 7 protrudes to the outside of the exhaust pipe 2 and is designed to be cooled by outside air.

Therefore, in this embodiment, when a resonance mode with a node near the temperature sensor 3 occurs, the temperature sensor 3 receives a cooling action, and the occurrence of resonance is detected in the form of a temperature drop.

Furthermore, the embodiment shown in FIG. 7 has a configuration in which a first temperature sensor 3A is arranged at a position extremely upstream of the electric heater 4, and a second temperature sensor 3B is arranged at a position slightly away from this on the upstream side. There is. According to this configuration, the detected temperature of the first temperature sensor 3A increases at a stage when the strength of resonance is relatively weak;
When the resonance becomes strong to a certain extent, the temperature detected by the second temperature sensor 3B increases. Therefore, at the same time as resonance is detected, its strength can be easily determined.

Further, in the embodiment shown in FIG. 8, a Helmholtz type resonance element consisting of a resonance chamber 8 and a front pipe 9 is connected to a position near the antinode of the resonance mode of the exhaust pipe 2, and the front pipe 9 is
It has a configuration in which a resonance detection sensor 1 consisting of a temperature sensor 3 and an electric heater 4 adjacent to the temperature sensor 3 is disposed.

In the above configuration, resonance in the exhaust pipe 2 causes severe sound pressure fluctuations in the vicinity of the antinode position, and therefore particles violently reciprocate within the cylindrical pipe 9 due to the resonance effect of the resonance chamber 8. Therefore,
As in each of the embodiments described above, the temperature detected by the temperature sensor 3 rises, thereby making it possible to detect the occurrence of resonance.

Next, an embodiment in which the resonance detection sensor 1 described above is utilized in an exhaust noise reduction device for an automobile engine will be described with reference to FIG. 9.

In the same figure, IH is the engine, and 12 is this engine 1.
1 is a front tube connected to the exhaust manifold 13 of 1, I4 is a catalytic converter connected to the upper 8 front tube 12 via a flexible tube 15, and 16 is a catalytic converter connected to the above catalytic converter 1 via a first center tube 17.
The main muffler 18 is connected to the pre-muffler 16 via the second center tube 19, and the main muffler 18 includes a main tail tube 20 with a long pipe length and a sub-tail tube 21 with a short pipe length. are connected. A switching valve 22 for opening and closing the subtail tube 21 is interposed in one subtail tube 2I.

The switching valve 22 is driven to open and close by an actuator (not shown). That is, the switching valve 2
2 is closed, the exhaust gas is discharged only from the main tail tube 20, and when the switching valve 22 is open, the exhaust gas is discharged from both the main tail tube 20 and the sub tail tube 2I. Therefore, different exhaust systems will be constructed for each, and the resonance conditions will be different.

Then, the resonance detection sensor 1 having the configuration shown in FIG. 8 is disposed together with the Helmholt type resonance element at an appropriate position of the second center tube 19, that is, at a position that does not form a node as much as possible in each resonance mode that may occur. The switching valve 22 is controlled based on the detection signal. Specifically, the temperature signal output from the temperature sensor 3 is differentiated twice, and the presence or absence of resonance is determined from the differential value, and -
When resonance is detected in one exhaust system, the switching valve 22 is controlled to switch to the other exhaust system.

FIG. 10 (A) shows the characteristics of the exhaust noise generated in the above exhaust system during acceleration. When the switching valve 22 is "closed", the characteristic is shown by the broken line A, and when the switching valve 22 is "open", the characteristic is shown by the solid line. Becomes a characteristic. In other words, resonance occurs at a certain rotation speed in either exhaust system, but the rotation speeds are different for the two exhaust systems.

Here, since the resonance detection sensor l can detect this resonance before it reaches its peak, the switching pulse signal based on the above-mentioned differential signal is activated at the point when resonance starts to occur in one exhaust system. (B), and based on this, the exhaust system is alternately switched to the other exhaust system. Therefore, an exhaust system in which resonance does not occur is always selected, and the actual noise characteristics are as shown by the solid line in FIG. Thereby, resonance during acceleration is suppressed to a low level, and an increase in noise due to resonance can be prevented.

Incidentally, although not shown in the drawings, since the exhaust system is similarly selected during deceleration, an increase in noise during deceleration can also be prevented.

Further, in the above embodiment, the length of the tail tube is changed by the switching valve 22, but instead of this, a movable throttle mechanism may be provided at an appropriate position in the exhaust system to change the passage area. It is also possible to suppress resonance. FIG. 11 shows one embodiment of this, in which a movable throttle mechanism 3 is installed upstream of the main muffler 18 of the exhaust system.
1 is interposed. As shown in FIG. 12, this throttle mechanism 31 includes a cylindrical valve case 32 and a butterfly valve type valve body 33 that can be opened and closed. A hole 34 is formed as an opening. That is, in the above configuration, the throttle ratio changes by opening and closing the valve body 33, and two exhaust systems having mutually different resonance modes are formed.

In this embodiment, the resonance detection sensor 1 consisting of the temperature sensor 3 and the electric heater 4 described above is disposed at a position immediately before the upstream of the main muffler 18 and a position immediately before the upstream of the bridge muffler 16, respectively. The opening and closing of the valve body 33 is controlled based on the detection.

The main muffler 18 and the bridge muffler 16 act as expansion parts in the exhaust system.
Sound mode resonance is likely to occur.

Effects of the Invention As is clear from the above description, the resonance detection device according to the present invention can easily and reliably detect resonance occurring in a pipe as a temperature change. In particular, since resonance detection can be performed using a simple temperature sensor, it can be easily applied to engine exhaust pipes through which high-temperature, high-pressure exhaust flows, and is excellent in terms of durability and cost.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the resonance detection sensor according to the present invention, Fig. 2 is a characteristic diagram showing changes in detected temperature, etc., and Fig. 3 is a sectional view showing different embodiments of the resonance detection sensor. 4 is a sectional view taken along the line Ml-Ml, FIG. 5 is a sectional view showing an embodiment in which a bypass passage is provided, FIG. 6 is a sectional view showing an embodiment in which a cooling section is provided, and FIG. FIG. 7 is a sectional view showing an embodiment having a plurality of temperature sensors, FIG. 8 is a sectional view showing an embodiment combined with a Helmholtz type resonance element,
Fig. 9 is a configuration explanatory diagram showing an example of an exhaust noise reduction device equipped with a resonance detection sensor, Fig. 10 is a characteristic diagram showing the detected temperature etc. of the resonance detection sensor in this configuration, and Fig. 11 is an exhaust noise reduction A configuration explanatory diagram showing different embodiments of the device, 12th IC is a sectional view of the main part thereof. l... Resonance detection sensor, 3... Temperature sensor, 4...
- Electric heater (heating section), 7... heat pipe (cooling section). Fig. 1 3--J, l support 4--f gift heater (Torisuke B mourning) Fig. 2 3 people outside Fig. 6 Fig. 6 7-e - Ia at the tonneau (41 ≦) Figure 7 154-

Claims (1)

[Claims] (1) A temperature sensor placed in a position where gas particles move significantly due to resonance in the pipe, and a heating section that is placed close to this temperature sensor and whose temperature is relatively higher than the temperature inside the pipe. Or a resonance detection device equipped with a relatively low-temperature cooling section.