JPS641612Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a knocking sensor vibration detector that is attached to a cylinder block or the like and extracts the vibration as an electrical signal in order to detect knocking in the combustion chamber of an internal combustion engine.

As a conventional vibration detector, there is one shown in FIG. 1, for example. To explain this, a pair of piezoelectric elements 3 holding a lead plate 2 between them, and a weight 4 for applying stress to the piezoelectric elements 3 by vibration acceleration are supported by bolts 5 at the inner bottom of the case 1 having a bottomed cylindrical shape. It is designed to do so. 6 is an insulator. Further, a cover 9 having a terminal 8 for extracting an electric signal generated in the piezoelectric element 3 from the lead plate 2 to the outside via a lead wire 7 is attached to the opening of the case 1. It is attached by crimping.

This vibration detector is attached to a cylinder block (not shown) or the like using a threaded portion 10 of a case 1, and upon receiving the vibrations, the piezoelectric element 3 generates an electric signal corresponding to the vibration acceleration, and this electric signal is controlled by an external device. The control unit outputs the signal to the unit, and this control unit detects knocking.

However, in such a conventional vibration detector, the weight 4 is used to apply stress to the piezoelectric element 3, and the vibration of the cylinder block is transmitted to the piezoelectric element 3 as the inertial force of the weight 4. Even after the vibration of the cylinder block has stopped, the weight 4 is subject to damped vibration, and this damped vibration causes the output signal of the piezoelectric element 3 to also undergo damped vibration. In particular, since the weight 4 has a relatively large mass, the decay time of the electrical signal outputted in response to the vibration of the cylinder block becomes long.

Furthermore, since the piezoelectric element 3 has a high impedance, it is easily affected by noise, and because it has good sensitivity, it may detect vibrations other than those that should be detected.Furthermore, the piezoelectric element 3 has a large temperature coefficient, so it can be used to detect vibrations such as cylinder blocks, etc. It is not a good idea to install it in a place where there are significant temperature changes.

The present invention was developed in view of the current situation, and instead of the conventional piezoelectric element, a packed layer is formed using lightweight carbon microscopic hollow spheres with low electric resistance, and vibrations of cylinder blocks, etc. are absorbed by the packed layer. The vibration is detected by changing the contact area between the carbon particles and the resistance change of this packed layer.

The present invention will be explained below based on an embodiment shown in FIGS. 2 to 5.

First, to explain the configuration, the bottomed cylindrical case 1
A cylindrical insulating member 12 that covers the inner peripheral wall of the case 1 is inserted into the case 1. Inside the insulating member 12, a filling layer filled with carbon minute hollow spheres (hereinafter referred to as a carbon balloon) is placed at the bottom of the case 11. layer) 13 is formed. An electrode plate 14 is mounted above the carbon balloon layer 13, and the electrode plate 14 is urged toward the carbon balloon layer 13 by a spring 15 with a predetermined pressure. Further, a terminal 16 is provided on the base end side of the spring 15.
is screwed into the insulating member 12, and the terminal 16 and the carbon balloon layer 13 are electrically connected via the electrode plate 14 and the spring 15.

Furthermore, a cover 17 made of an insulating material is attached above the terminal 16 by crimping the edge of the opening of the case 11.

By the way, carbon balloons (carbon micro hollow spheres) are hollow spheres made of carbonaceous material, with an outer diameter of approximately 0.1 mm, and are electrically conductive.
It has excellent heat resistance and light weight.

The vibration detector 18 having such a configuration is attached to a cylinder block or the like by means of a threaded portion 19 of the case 11. Then, as shown in FIGS. 3 to 5, a terminal of a DC power source 20 is connected to the case 11 and the terminal 16 to form a constant current circuit 21. The case 11, the carbon balloon layer 13, the electrode plate 14, and the spring 1
A constant current flows between the terminal 5 and the terminal 16. Furthermore, a terminal of a signal processing section 22 of the control unit is connected to the case 11 and the terminal 16 so that voltage changes of the carbon balloon layer 13 are outputted to the signal processing section 22.

Next, the functions of the vibration detector 18 having such a configuration will be explained based on FIGS. 4 and 5.

FIG. 4 shows a state in which the cylinder block etc. are not vibrating. At this time, each carbon balloon 13A maintains a substantially spherical shape and their contact is almost a point contact, and the resistance of the carbon balloon layer 13 is It's getting bigger.

Further, when the cylinder block or the like vibrates, the electrode plate 14 vibrates and presses the carbon balloon layer 13 by its inertial force. Therefore, the carbon balloons 13A are pressed by the inertial force of the electrode plate 14 and flatten as shown in FIG. 5, and the contact area between the carbon balloons 13A increases. Therefore, the resistance value of the carbon balloon layer 13 decreases, and the voltage output to the signal processing section 22 also decreases.

At this time, the signal processing section 22 may be configured to be able to confirm that knocking has occurred if the voltage value, which is the signal from the vibration detector 18, is below a predetermined value.

In this embodiment, as described above, the carbon balloon layer 1
3 to detect the vibrations of the cylinder block, etc. by the change in the resistance value of the carbon balloon layer 13, the sensitivity can be suppressed to some extent, and small vibrations (noise) other than the cylinder block can be detected by the resistance value of the carbon balloon layer 13. It no longer shows any change. Furthermore, since the carbon balloon layer 13 can be pressed by the inertia force of the electrode plate 14 having a small mass,
Since the inertia force can be made smaller than the inertia force of conventional weights, the damped vibration time of the electrode plate 14 after the cylinder block stops vibrating can be shortened, thereby reducing the cylinder block vibration time and the output signal time. It can be made compatible.

Moreover, since the resistance change of the carbon balloon with respect to temperature change is not so large, it is suitable even for locations with severe temperature conditions such as cylinder blocks.

As explained above, in the present invention, instead of the conventional piezoelectric element, carbon micro hollow spheres are used to form a packed layer, and the vibrations of the cylinder block etc. are detected by the resistance change of this packed layer. Since the sensitivity described above is lower than that of conventional piezoelectric elements, vibrations (noise) other than those of the cylinder block are no longer detected, and knocking can now be detected extremely well.

Furthermore, since the weight of the electrode plate as a weight can be made extremely light compared to the conventional one, its inertia force can be reduced, so that the damped vibration of the electrode plate after the vibration of the cylinder block etc. has disappeared can be reduced, and the cylinder block The vibration time and the output signal time can be made to almost match.

Furthermore, since the resistance change of carbon with respect to temperature changes is not so large, it is suitable even for locations with severe temperature conditions such as cylinder blocks.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional vibration detector for knocking sensor, FIG. 2 is a sectional view showing an embodiment of the present invention, FIG. 3 is a block diagram of the vibration detector shown in FIG. 2, and FIG. FIG. 5 is a state diagram explaining the operating state. 11... Case, 13... Carbon balloon layer, 13A... Carbon balloon, 14... Electrode plate, 15... Spring, 18... Vibration detector,
21... constant current circuit, 22... signal processing section.

Claims (1)

[Scope of utility model registration request] Forming a packed layer of carbon micro hollow spheres inside the case,
Vibration is detected by placing an electrode plate pressed against the layer with a predetermined pressure on the top surface of the filling layer, and by grounding the bottom surface of the filling layer and measuring the resistance change of the filling layer. Vibration detector for knocking sensor featuring features.