JPH038976Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a crank angle sensor for controlling an internal combustion engine.

BACKGROUND ART In electronically controlled internal combustion engines, the rotational angular position of a crankshaft is electrically detected in some way, and ignition timing and fuel injection timing are controlled based on this detection signal. A crank angle sensor is used for this purpose. It is widely known that the conventional crank angle sensor is of the type placed inside the distributor, but in contrast, the applicant of the present application proposed a method in which a protruding rib was formed on the cam timing pulley in Utility Application No. 145022/1983. We are proposing a crank angle sensor.

Problems to be Solved by the Invention Various types of detection elements, such as photoelectric type or magnetic type, are used for detecting the passage of protruding blades formed in the shape of a slit ring on the rotor. For some types of these (for example, Hall elements), it is preferable to arrange the gap between the sensing blade and the sensing element as close as possible in order to obtain a large output voltage from the sensing element, and in reality, the dimensions of the parts The gaps are determined to the extent that each part does not interfere, taking into account tolerances and assembly tolerances. However, since such rotors are often made of metal, a problem has arisen in that in cold weather, moisture in the air condenses on the rotor and the resulting ice damages the detection elements.

Means for Solving the Problems The present invention is characterized in that a resin coating layer is provided on the metal blades for detection of the rotor. Resin is less susceptible to freezing than metal, and even if it freezes, it peels off easily, so damage to the detection element can be prevented.

Embodiment In FIG. 1, a camshaft 1 is supported on a cylinder head 2 by a bearing 3. As shown in FIG. A seal 4 is arranged adjacent to the bearing part 3. Although only one end portion of the camshaft 1 is shown in FIG. 1, it is clear that it extends long to the right and is equipped with a cam (not shown) for driving an intake valve or an exhaust valve. Dew.

A cam timing pulley 5 is attached to the end of the camshaft 1, and can be connected to a crankshaft of an engine by a belt or the like. The cam timing pulley 5 is fixed to the camshaft 1 with washers 6 and bolts 7. In this embodiment, the cam timing pulley 5 serves as a rotor for detecting the crank angle, and on one end surface of the cam timing pulley 5 there are blades 6 (see FIG. 2) arranged at equal intervals on a circle centered on the axis of the camshaft 1. is provided in a protruding manner, and furthermore, a blade 7 is provided in a protruding manner on a concentric circle and extends over an angular range of 180 degrees. These vanes 6 and 7 can be formed integrally with the cam timing pulley 5, or press-molded vanes can be fixed to the cam timing pulley 5 with bolts or the like. The equally spaced blades 6 are for detecting the position of the crankshaft at each predetermined angle, and the 180 degree blades 7 are for detecting the position of the crankshaft at each predetermined angle.
This is to detect a reference position every 720 degrees.

As shown in FIGS. 1 and 3, the surface of each of these blades 6, 7 is coated with a polytetrafluoroethylene resin layer 8. On the other hand, the blades 6 and 7 are made of a magnetic material such as iron in relation to detection Hall elements 10 and 11, which will be described later. The thermal conductivity of polytetrafluoroethylene resin is 6×10 ^-4 cal/cm.
s.°C, and the thermal conductivity of iron is 0.18 cal/cm. s.°C, and the difference is 1:300. Therefore, the blade 6,
Compared to the case where the iron material 7 is left exposed, the resin coating layer is less likely to form ice, and even if it forms, it can be easily peeled off.

Detection elements 10 and 11 are arranged to sandwich each blade 6 and 7, and these detection elements 1
0 and 11 are fixed to the cylinder head 2 by brackets 12 and bolts 13. FIG. 4 shows details of the detection element 10 for one blade 6, and the other blade 7 is configured in the same manner. The detection element main body 10 is made of resin and has a U-shaped cross section, and a permanent magnet 14 is inserted into one side of the main body, and a Hall element 15 is inserted into the other side so as to face each other. Yokes 16 and 17 are engaged with the permanent magnet 14 and the Hall element 15, respectively.
When the blade 6 is sandwiched within the detection element 10 as shown in FIG.
6 is formed, and at this time the magnetic force passing through the Hall element 15 is very small.

When the cam timing pulley 5 rotates and the blade 6 is not sandwiched between the detection element 10, the permanent magnet 14
From there, a magnetic circuit is formed that passes through the Hall element 15 and returns to the yokes 17 and 16 as shown by arrow C. At this time, the magnetic force passing through the Hall element 15 increases and the generated voltage increases. In this way, the position of the cam timing pulley 5, that is, the position of the crankshaft, can be detected every time the blade 6 appears. In the detection device having such a configuration, the relationship between the detection output voltage output from the Hall element 15 and the set gap between the detection elements 10, 11 and the blades 6, 7 is as shown in FIG. Therefore, in order to increase the detection output voltage and extract a clear signal, it is preferable to shorten the above-mentioned interval. If the gap is narrowed, it becomes easier for the two to come into contact, but since the gap is determined taking into account component dimensional errors and assembly tolerances, the two usually do not come into contact. However, when freezing occurs in cold weather, the ice hits the detection element, so the present invention eliminates the occurrence of such ice formation and prevents damage to the detection element.

Effects of the Invention As explained above, according to the present invention, the reliability of the detection device can be increased.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the crank angle sensor according to the present invention, Figure 2 is an end view of the cam timing pulley, Figure 3 is a partially enlarged view of Figure 1, Figure 4 is a detailed view of the detection element, and Figure 5. is a graph showing the relationship between the gap and the output voltage. 1...Camshaft, 5...Cam timing pulley, 6, 7...Blade, 8...Resin coating layer.

Claims (1)

[Scope of utility model registration request] In a crank angle sensor, a metal blade for detection is provided protruding from a rotor that rotates in synchronization with the crankshaft, and a detection element is fixedly arranged to sandwich the blade. A crank angle sensor characterized by providing a coating layer.