JPH0442483Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a support structure for a camshaft in a valve train of an internal combustion engine.

[Conventional technology]

Conventionally, in a valve train system in which multiple intake and exhaust valves are operated synchronously by two camshafts, one camshaft is rotationally driven by a crank using a timing belt or chain, and its rotation is controlled by a helical gear. Camshaft structures in which the transmission is transmitted to the other camshaft via the camshaft are already known. In this way, especially in valve train systems that use helical gears to transmit rotational force from one camshaft to the other, a component force in the thrust direction is generated, and this thrust force fluctuates. As a result, there was a problem in that the bearing portion and the camshaft produced a hammering sound.

Such hitting noise of the camshaft is caused by interference between a bearing portion that supports the camshaft and a flange of the camshaft. Therefore, by reducing the clearance between the bearing portion and the flange, this hitting noise can be reduced. However, in order to reduce such a clearance, it is necessary to greatly improve the machining accuracy of the camshaft and bearing, which causes problems such as increased costs and man-hours due to changes in machining equipment. By reducing the clearance, the efficiency of camshaft assembly will decrease.
Furthermore, a problem arises in that the friction on the thrust surface increases.

In an attempt to solve the above-mentioned problems, the present applicant coaxially attaches a shaft member of an auxiliary component attached to a fixed frame such as a cylinder head to the end of at least one of the two camshafts. and a spring member is provided between the camshaft and the shaft member to bias the camshaft in the axial direction.
Devised a support structure for the camshaft.
(see issue).

[Problem that the invention attempts to solve]

The above-mentioned Utility Application No. 172292 (Sho 62-79907)
The camshaft support structure devised in JP-A No. 2003-110020) has made it possible to reduce the hammering noise of the camshaft while keeping the gap between the camshaft and the bearing the same as before. However, since this device has a structure in which a spring is interposed between the camshaft and the shaft member of the auxiliary machine, a new problem arises in that the spring causes a resonance phenomenon as the camshaft rotates.

The present invention aims to provide a camshaft support structure that reduces the hitting noise of the camshaft while keeping the gap between the camshaft and the bearing portion constant and does not cause resonance.

[Means for solving problems]

In order to solve the above problems, the camshaft support structure according to the present invention has a driving camshaft and a driven camshaft rotatably supported by bearings formed in a fixed frame, and each of these camshafts A cam configured to be interconnected through provided gears, and to engage a flange formed at an end of the driven camshaft with the bearing portion to restrict displacement of the driven camshaft in the thrust direction. In the shaft support structure, a shaft member of an auxiliary machine attached to the fixed frame is coaxially connected to a shaft end of the driven camshaft, and the auxiliary machine side end of the driven camshaft and the A flange is formed at each end of the shaft member of the auxiliary machine, and an electrostrictive element is interposed between these two flanges, and the fixed frame has a gap between the flange of the driven camshaft and the fixed frame. A gap sensor is provided to detect the gap, and the sensor and the electrostrictive element are connected to an electronic control device, and the electrostrictive element is expanded and contracted in accordance with the movement of the flange of the driven camshaft in the thrust direction. The feature is that the gap between the frame and the fixed frame is kept constant.

[Effect]

According to the present invention, the gap sensor provided on the fixed frame detects the movement of the driven camshaft in the thrust direction based on a change in the distance between the gap sensor and the flange of the driven camshaft, and the output of the sensor is electronically transmitted. A control device processes and controls the current applied to the electrostrictive element, thereby expanding and contracting the electrostrictive element in the thrust direction to maintain a constant gap between the driven camshaft and the fixed frame.

Therefore, the hitting noise of the camshaft is reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a driving camshaft 1 and a driven camshaft 2 are arranged parallel to each other on a cylinder head (fixed frame) 3, and are rotated by bearings 4, 4 provided on the cylinder head 3, respectively. freely supported.

Large diameter portions 5 are located on both sides of the portion of the camshafts 1 and 2 that are inserted into the bearing portion 4 located at the left end in the figure.
Alternatively, a flange 6 is formed. These large diameter portions 5 or flanges 6 can engage with the end surface of the bearing portion 4, thereby making it possible to restrict displacement of the camshafts 1 and 2 in the axial direction. A cam 7 formed in the middle of each camshaft 1, 2 engages with an intake/exhaust valve (not shown) to open and close them.

The end of the drive camshaft 1 projects outward from the side of the cylinder head 3, and a timing pulley 8 is fitted onto the projecting end. The timing pulley 8 is connected to a crankshaft (drive source) via a timing belt (not shown), and transmits rotation of the crankshaft. Each camshaft 1, 2 is provided with a helical gear 11, 12, and these helical gears 11, 12 mesh with each other to transmit driving and rotation between the driven camshafts 1, 2. The driving and driven camshafts 1, 2 thus rotate synchronously.

The distributor 13 is attached to the outer wall surface of the cylinder head 3. Day distributor 13
The shaft member 14 is supported by the bearing 4 at the right end.
Further, referring to FIG. 2, the end 15 of the shaft member 14 fits into a recess 17 formed in the end 16 of the driven camshaft 2 and is coaxially connected thereto.

A flange 18 is formed at the end of the driven camshaft 2 on the side of the auxiliary machine 13, and a flange 19 is also formed at the end of the shaft member 14 of the auxiliary machine 13. A laminated electrostrictive element 20 is interposed between these flanges 18 and 19, and this electrostrictive element 20 is attached to both flanges 18 and 19.
The driven camshaft 2 is urged to the left in FIG. 1 by its elastic force, and the gap between the driven camshaft 2 and the bearing portion is kept constant. Therefore, the large diameter portion 5 of the driven camshaft 2 is always in contact with the end face of the left end bearing portion 4, and the flange 6 is always separated from the bearing portion 4.

The cylinder head 3 further includes a driven camshaft 2.
A gap sensor 21 is provided facing the flange 18 formed at the end of the flange 18 . This gap sensor 21 detects the distance between the gap sensor 21 and the flange 18, and is connected to a central electronic control unit (CPU) 23 via an amplifier 22, and the CPU 23 is connected to an AC power source 24. This AC power supply 24 is connected to the electrostrictive element 20, and the detection signal of the gap sensor 21 is sent to the CPU 2 through voltage amplification by the amplifier 22.
3, and the CPU 23 is configured to send a control current from the AC power supply 24 to the electrostrictive element 20 based on this input.

The operation of this embodiment having the above configuration will be explained. When the driven camshaft 2 is driven by the driving camshaft 1 and moves in the thrust direction, this movement is controlled by the fixed frame,
That is, the gap sensor 21 fixed to the cylinder head 3 is connected to the flange 1 of the driven camshaft 2.
8 is detected as a change in the distance between the
Input to CPU23. The CPU 23 sends a control current corresponding to this voltage from the AC power supply 24 to the electrostrictive element 20 to expand and contract the electrostrictive element 20 in the thrust direction.

For example, when the movement of the driven camshaft 2 in the thrust direction is large and the distance between the flange 18 and the gap sensor 21 becomes small, a large current is applied to the electrostrictive element to extend the electrostrictive element and the driven camshaft 2 is moved. Push it back to the left in Figure 1. On the contrary, flange 1
When the distance between the gap sensor 8 and the gap sensor 21 increases, the current to the electrostrictive element 20 is controlled to cause the electrostrictive element 20 to contract. In this way, the movement of the driven camshaft 2 in the thrust direction is captured as the movement of the flange 18 in the left-right direction, and by expanding and contracting the electrostrictive element, the distance between the driven camshaft 2 and the bearing portion 4 of the cylinder head 3 is increased. Always keep the gap constant.
Therefore, the hitting noise of the driven camshaft is reduced.

[Effect of idea]

As described above, according to the present invention, the gap between the driven camshaft and the bearing part can be kept constant at all times, and the occurrence of resonance can be avoided, so the hitting noise of the camshaft can be efficiently reduced. Furthermore, seizure of the thrust surface can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, and FIG. 2 is an enlarged view of the main parts of the same embodiment. 1... Drive camshaft, 2... Driven camshaft, 3...
... Cylinder head (fixed frame), 4 ... Bearing section, 7
...Cam, 11, 12...Helical gear, 13...
Distributor (auxiliary equipment), 14...shaft member,
18, 19...flange, 20...electrostrictive element, 2
1...Gap sensor, 23...CPU, 24...
…AC source.

Claims (1)

[Scope of utility model registration request] A driving camshaft and a driven camshaft are rotatably supported by a bearing portion formed on a fixed frame, and are interconnected via gears provided on each of these camshafts. In the camshaft support structure configured to engage a flange formed in the bearing portion with the bearing portion to restrict displacement of the driven camshaft in the thrust direction, the fixed frame is attached to the shaft end of the driven camshaft. A shaft member of an auxiliary machine attached to the camshaft is coaxially connected, a flange is formed on the auxiliary machine side end of the driven camshaft and an end of the shaft member of the auxiliary machine, and both flanges An electrostrictive element is interposed between the two, and the fixed frame is provided with a gap sensor that detects a gap between the flange of the driven camshaft and the fixed frame, and the sensor and the electrostrictive element are connected to an electronic control device. The camshaft is connected to the camshaft, and the electrostrictive element is expanded and contracted in response to movement of a flange of the driven camshaft in a thrust direction to maintain a constant gap between the driven camshaft and the fixed frame. supporting structure.