JP2010096105A - Cam drive device - Google Patents

Abstract

An object of the present invention is to reduce tension applied to a timing chain by a tensioner in an engine cam drive device and reduce friction in a camshaft and a crankshaft.
A cam drive device (1) is provided with a crankshaft (5) and a drive sprocket (7), a first intermediate shaft (6) that is rotated by transmission of power from the crankshaft (5), and a second intermediate (3) provided with a driven sprocket (9). A timing chain 10 that is stretched between the shaft 8, the drive sprocket 7, and the driven sprocket 9, transmits power from the drive sprocket 7 to the driven sprocket 9, and a camshaft 11 that rotates by receiving power from the second intermediate shaft 8. , 12.
[Selection] Figure 1

Description

  The present invention relates to a cam drive device that transmits power from a crankshaft of an engine to a camshaft disposed on a cylinder head side.

  As a valve operating mechanism that opens and closes an intake / exhaust valve of an engine, an OHC (Overhead Camshaft) type mechanism is used. In such a valve mechanism, a drive sprocket is provided on the crankshaft, a driven sprocket is provided on the camshaft, and the rotation of the crankshaft is transmitted to the camshaft by connecting both sprockets with a timing chain. Further, a pulley using a pulley instead of a sprocket and a timing belt instead of a timing chain is also employed.

  The timing chain may be stretched and slackened with use or deformed when a load is applied. In order to solve this problem, a guide and a tensioner are provided in the valve mechanism. The tensioner applies appropriate pressure to the timing chain to keep the tension of the timing chain constant. Even when the timing belt is employed, the timing belt is given a constant tension by the tensioner. An improved valve mechanism is disclosed in Patent Document 1.

JP 2005-180550 A

  By the way, in the valve operating mechanism, the timing chain and the timing belt may receive a variable load in accordance with the opening / closing operation of the intake / exhaust valve. Such a fluctuating load may cause the timing chain and the timing belt to vibrate. In order to suppress this, a method of applying a larger tension to the tensioner to suppress the fluctuating load is employed.

  However, when a large tension is applied to the tensioner, a force is applied in the rotational radius direction of the camshaft or the crankshaft, which causes a deflection of the camshaft or the crankshaft. Such deflection causes friction loss between the camshaft and the bearing supporting the camshaft and between the crankshaft and the bearing supporting the crankshaft.

  Therefore, an object of the present invention is to suppress the deflection of the camshaft and the crankshaft and reduce the friction in the camshaft and the crankshaft.

  The cam drive device of the present invention that solves such a problem is provided with a crankshaft, a drive sprocket, a first intermediate shaft that rotates by transmission of power from the crankshaft, and a second sprocket provided with a driven sprocket. An intermediate shaft, a timing chain or a timing belt that is stretched between the drive sprocket and the driven sprocket and transmits power from the drive sprocket to the driven sprocket, and rotates by receiving power from the second intermediate shaft And a camshaft.

  With such a configuration, transmission of the fluctuating load to the timing chain due to the opening / closing operation of the intake / exhaust valve is suppressed. Thereby, the tensioner can suppress the tension applied excessively to suppress the fluctuating load. Thereby, the deflection of the intermediate shaft provided with the sprocket can be suppressed. Further, since the load applied by the tensioner does not directly reach the camshaft or the crankshaft, the camshaft or the crankshaft is restrained from being deflected and the friction at the bearing portion can be reduced.

  In such a cam drive device, the rotation ratio between the crankshaft and the first intermediate shaft is a rotation ratio at which the first intermediate shaft rotates 360 ° while the crankshaft rotates 720 °. It can be. Further, the second intermediate shaft can be made slower in rotation speed than the crankshaft rotation speed. By setting it as such a structure, the cam gear provided in the cam shaft can be made into a small diameter. Thereby, a cylinder head can be reduced in size and an engine can be made compact.

  The cam drive device of the present invention can suppress the deflection of the camshaft and the crankshaft and reduce the friction in the camshaft and the crankshaft.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a schematic configuration of an engine 100 incorporating the cam drive device 1 of the present invention. FIG. 1 (a) is an explanatory view showing a state of the engine 100 with the side cover removed, and FIG. 1 (b) is a side view of FIG. 1 (a). The engine 100 includes four cylinders and has a DOHC (Double Over Head Camshaft) type valve operating structure that transmits the rotation of the crankshaft 5 to the camshafts 11 and 12.

  The engine 100 includes a cam drive device 1, a crankcase 2, a cylinder block 3, and a cylinder head 4. A cylinder block 3 is disposed above the crankcase 2, and a cylinder head 4 is disposed above the cylinder block 3. The cam drive device 1 is provided with a crankshaft 5 and a drive sprocket 7, a first intermediate shaft 6 that is rotated by transmission of power from the crankshaft 5, a second intermediate shaft 8 that is provided with a driven sprocket 9, and a drive sprocket 7. And a timing chain 10 that transmits power from the drive sprocket 7 to the driven sprocket 9 and camshafts 11 and 12 that rotate by receiving power from the second intermediate shaft 8. The cam drive device 1 is configured such that the camshafts 11 and 12 rotate once while the crankshaft 5 rotates twice.

  The crankshaft 5 is connected to a connecting rod of the engine 100 and is rotated by a vertical movement of a piston provided in the engine 100. The crankshaft 5 is disposed on a mating surface with the crankcase 2 and the cylinder block 3 via a bearing and is rotatably supported. The crankshaft 5 is provided with a crank gear 5a, and the crankshaft 5 and the crank gear 5a rotate together.

  The first intermediate shaft 6 is rotatably supported on the cylinder block 3 via a bearing above the crankshaft 5. The first intermediate shaft 6 is provided with a first transmission gear 6a together with the drive sprocket 7, and the first shaft 6, the first transmission gear 6a, and the drive sprocket 7 rotate together. Further, the first transmission gear 6a is arranged so as to mesh with the crank gear 5a. The gear ratio between the first transmission gear 6 a and the crank gear 5 a is 1: 1, and the first shaft 6 rotates at the same rotational speed as the crankshaft 5.

  The second shaft 8 is rotatably supported on the cylinder block 3 via a bearing above the first shaft 6. The second shaft 8 is provided with a second transmission gear 8 a together with a driven sprocket 9. The second shaft 8, the second transmission gear 8a, and the driven sprocket 9 rotate together.

  The timing chain 10 is stretched between the drive sprocket 7 and the driven sprocket 9, and transmits power from the drive sprocket 7 to the driven sprocket 9. The timing chain 10 is given a certain tension by the chain tensioner 10a and the chain guide 10b, and is prevented from being loosened or deformed. The gear ratio between the drive sprocket 7 and the driven sprocket 9 is 1: 2, and the second shaft 8 rotates 360 ° while the first shaft 6 rotates 720 °.

  Instead of the drive sprocket 7 and the driven sprocket 9, a pulley may be used, a timing belt may be used instead of the timing chain 10, and a timing belt tensioner may be used instead of the chain tensioner 10a and the chain guide 10b. good.

  The camshaft 11 opens and closes an intake valve by a cam and a rocker arm. The camshaft 12 opens and closes an exhaust valve by a cam and a rocker arm. The camshaft 11 and the camshaft 12 are rotatably supported by the cylinder head 4 via bearings. Further, the camshaft 11 is provided with a cam gear 11a, and the camshaft 11 and the cam gear 11a rotate together. The camshaft 12 is provided with a cam gear 12a, and the camshaft 12 and the cam gear 12a rotate together. The cam gear 11a and the cam gear 12a are respectively arranged so as to be engaged with the second transmission gear 8a. The gear ratio between the second transmission gear 8 a and the cam gear 11 a is 1: 1, and the camshaft 11 rotates at the same speed as the second intermediate shaft 8. Similarly, the gear ratio between the second transmission gear 8 a and the cam gear 12 a is 1: 1, and the camshaft 12 rotates at the same rotational speed as the second intermediate shaft 8.

  In addition, the cam drive device 1 includes a connection member 13 that connects the distal end portion of the first intermediate shaft 6 and the distal end portion of the second intermediate shaft 8. The connecting member 13 is a beam-like member that connects the distal end sides of the first intermediate shaft 6 and the second intermediate shaft 8, and is a member that fixes the distal end sides of the first intermediate shaft 6 and the second intermediate shaft 8. Any shape is acceptable.

  The cam drive device 1 configured as described above transmits the rotation of the crankshaft 5 to the first intermediate shaft 6, transmits the rotation of the first intermediate shaft 6 to the second intermediate shaft 8, and The rotation is transmitted to the camshafts 11 and 12. The camshafts 11 and 12 rotate 360 ° while the crankshaft 5 rotates 720 °. That is, the camshafts 11 and 12 rotate once while the crankshaft 5 rotates twice.

  In the cam drive device 1, the timing chain 10 is not directly stretched between the cam gears 11 a and 12 a, so that the fluctuating load due to the intake and exhaust valves is not transmitted to the timing chain 10. Conventionally, the tension applied by the chain tensioner has been increased in order to suppress fluctuation load due to the intake / exhaust valve from being transmitted to the timing chain and vibration of the timing chain. However, in the cam drive device 1 of the present embodiment, since the fluctuating load due to the intake / exhaust valve is not transmitted to the timing chain 10, the tension applied by the chain tensioner 10a can be reduced as compared with the conventional case.

  Further, the fluctuation due to the phase difference between the intake valve and the exhaust valve is absorbed by the second transmission gear 8a and does not reach the timing chain. Thereby, the tension | tensile_strength by the chain tensioner 10a is suppressed. Furthermore, since the first intermediate shaft 6 and the second intermediate shaft 8 are fixed by the fixing member 13, the shaft is supported at both ends. For this reason, the force of the rotation radial direction which the 1st intermediate shaft 6 and the 2nd intermediate shaft 8 receive with the timing chain 10 is reduced, and a bending is suppressed. Thereby, the friction in the bearings of the first intermediate shaft 6 and the second intermediate shaft 8 is reduced.

  Further, since the timing chain 10 is not directly stretched between the crank gear 5a and the cam gears 11a and 12a, it is not affected by the tension applied to the timing chain 10. Therefore, the crankshaft 5 and the camshafts 11 and 12 do not receive the force in the rotational radius direction by the timing chain 10 and the deflection is suppressed. For this reason, the friction in the bearings of the crankshaft 5 and the camshafts 11 and 12 is reduced.

  Next, a modification of the cam drive device of the present invention will be described with reference to FIGS. 2 and 3 are explanatory views showing a schematic configuration of an engine incorporating a cam drive device. FIG. 2 is an explanatory view showing a modified example different from the first embodiment, and FIG. It is explanatory drawing which showed the further different modification. The cam drive device 21 in FIG. 2 and the cam drive device 31 in FIG. 3 have substantially the same configuration as the cam drive device 1 in the first embodiment. This is different from the cam drive device 1 of Example 1. The cam drive device 21 and the cam drive device 31 have a gear ratio between the crank gear 5a and the first transmission gear 6a and a sprocket diameter ratio so that the cam shafts 11 and 12 rotate once while the crank shaft 5 rotates twice. The gear ratio between the second transmission gear 8a and the cam gears 22 and 23 can be arbitrarily set. 2 and 3 indicate the cylinder head 4 and the cam gears 11a and 12a of the first embodiment.

  In the cam drive device 21, the gear ratio between the crank gear 5a and the first transmission gear 6a is 1: 2, and the rotation ratio between the crankshaft 5 and the first intermediate shaft 6 is 2: 1. That is, the rotation ratio between the crankshaft 5 and the first intermediate shaft 6 is a rotation ratio at which the first intermediate shaft 6 rotates 360 ° while the crankshaft 5 rotates 720 °. Moreover, in the cam drive device 21, the radius of the drive sprocket 7 and the driven sprocket 9 is the same, the rotation ratio of the first intermediate shaft 6 and the second intermediate shaft 8 is 1: 1, and the first intermediate The shaft 6 and the second intermediate shaft 8 rotate at the same rotational speed. Further, the gear ratio between the second transmission gear 8a and the cam gears 22 and 23 is the same, and the rotation ratio between the second intermediate shaft 8 and the camshaft 11, and between the second intermediate shaft 8 and the camshaft 12 are both 1. The second intermediate shaft 8, the camshaft 11, and the camshaft 12 rotate at the same rotational speed. Therefore, in the cam drive device 21, the camshafts 11 and 12 rotate 360 ° while the crankshaft 5 rotates 720 °.

  The cam drive device 31 is characterized in that the rotation speed of the second intermediate shaft 8 is made slower than the rotation speed of the crankshaft 5. An example of a specific gear will be described below. In the cam drive device 31, the gear ratio between the crank gear 5a and the first transmission gear 6a is 1: 1, and the rotation ratio between the crankshaft 5 and the first intermediate shaft 6 is 1: 1. The crankshaft 5 and the first intermediate shaft 6 rotate at the same rotational speed. The radius of the driven sprocket 9 is 2.5 times the radius of the drive sprocket 7, and the rotation ratio between the first intermediate shaft 6 and the second intermediate shaft 8 is 2.5: 1. That is, the rotation ratio between the first intermediate shaft 6 and the second intermediate shaft 8 is a rotation ratio at which the second intermediate shaft 8 rotates 360 ° while the first intermediate shaft 6 rotates 900 °. The gear ratio between the second transmission gear 8a and the cam gear 32 is 1.25: 1, the gear ratio between the second transmission gear 8a and the cam gear 33 is 1.25: 1, and the second intermediate shaft 8 The rotation ratio of the cam shaft 11 and the second intermediate shaft 8 to the cam shaft 12 is 1: 1.25. That is, the rotation ratio between the second intermediate shaft 8 and the camshafts 11 and 12 is a rotation ratio at which the camshafts 11 and 12 rotate 450 ° while the second intermediate shaft 8 rotates 360 °. Therefore, in the cam drive device 31, the camshafts 11 and 12 rotate 360 ° while the crankshaft 5 rotates 720 °.

  The cam drive device 21 has a gear ratio between the crank gear 5a and the first transmission gear 6a, a ratio of sprocket diameters, a second transmission gear so that the camshafts 11 and 12 rotate once while the crankshaft 5 rotates twice. 8a and cam gears 22 and 23 are set in a gear ratio, and the cam gears 22 and 23 have a smaller diameter than the cam drive device 1 of the first embodiment, so that the cam drive device 21 lowers the cylinder head 24. can do. Similarly, since the cam driving device 31 has a gear and sprocket configuration that makes the cam gears 32 and 33 smaller, the cylinder head 34 can be lowered. Thus, the engine 100 can be made compact by lowering the cylinder head. The combination of the gear and the sprocket of the present embodiment may be adjusted so that the rotation speed of the second intermediate shaft 8 is slower than the rotation speed of the crankshaft 5.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

  For example, the cam drive device does not include the first intermediate shaft, and the crankshaft is provided with a driven sprocket instead of the crank gear, and the timing chain transmits the rotation of the crankshaft to the second intermediate shaft. There may be. Further, the cam drive device does not include the second intermediate shaft, and the camshaft is provided with a driven sprocket instead of the cam gear, and the timing chain transmits the rotation of the first intermediate shaft to the camshaft. There may be.

It is explanatory drawing which showed schematic structure of the engine incorporating a cam drive device, Comprising: (a) is explanatory drawing which showed the state of the engine which removed the side cover, (b) is (a). It is a side view. It is explanatory drawing which showed schematic structure of the engine incorporating a cam drive device, Comprising: It is explanatory drawing which showed the modification different from Example 1. FIG. It is explanatory drawing which showed schematic structure of the engine incorporating a cam drive device, Comprising: It is explanatory drawing which showed the further different modification.

Explanation of symbols

1, 21, 31 Cam drive device 5 Crankshaft 6 First intermediate shaft 7 Drive sprocket 8 Second intermediate shaft 9 Driven sprocket 10 Timing chain 11, 12 Camshaft

Claims (5)

A crankshaft,
A drive sprocket is provided, and a first intermediate shaft that is rotated by receiving power from the crankshaft;
A second intermediate shaft provided with a driven sprocket;
A timing chain or a timing belt that is stretched between the drive sprocket and the driven sprocket and transmits power from the drive sprocket to the driven sprocket;
A camshaft that is rotated by receiving power from the second intermediate shaft;
A cam drive device comprising: The cam drive device according to claim 1, wherein
A first fixing member for fixing a tip portion of the first intermediate shaft;
A second fixing member for fixing the tip of the second intermediate shaft;
A cam drive device comprising: The cam drive device according to claim 1, wherein
A first fixing member for fixing a tip portion of the first intermediate shaft;
A second fixing member for fixing the tip of the second intermediate shaft;
With
The first fixing member and the second fixing member are connecting members that connect a tip portion of the first intermediate shaft and a tip portion of the second intermediate shaft. apparatus. The cam drive device according to claim 1, wherein
The cam drive apparatus according to claim 1, wherein a rotation ratio between the crankshaft and the first intermediate shaft is a rotation ratio in which the first intermediate shaft rotates 360 ° while the crankshaft rotates 720 °. The cam drive device according to claim 1, wherein
The cam drive device according to claim 1, wherein a rotation speed of the second intermediate shaft is adjusted to be slower than a rotation speed of the crankshaft.

Images