JPH0552233U - Engine idle gear shaft mounting structure - Google Patents

Abstract

(57) [Summary] [Object] To provide a simple and inexpensive structure in which an idle gear shaft, which rotatably supports an idle gear in a timing gear device, can be attached to a crankcase with high accuracy. A plug-shaped idle gear shaft that rotatably supports an idle gear of a timing gear device is fitted into a small-diameter mounting hole formed in a front end face of a crankcase at one axial end thereof. And a ring-shaped flat surface which is formed substantially concentric with the plug-like projection and is in contact with the front end surface of the crankcase. The idle gear shaft is clamped and fixed to the front end portion of the crankcase by a bolt that axially inserts the gear shaft in an annular plane portion.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a mounting structure for an idle gear shaft that supports an idle gear in an engine timing gear device.

[0002]

[Prior Art]

 In many vehicle engines, an idle gear shaft that rotatably supports an idle gear included in a timing gear device is attached to a front end portion of a crankcase extending in the crankshaft axis direction. Now, an example of a conventional idle gear shaft mounting structure will be described with reference to FIGS. 1 and 2 for the sake of convenience and FIGS. 1 and 2 showing an embodiment of the present invention.

Reference numeral 10 in the figure generally indicates a diesel engine for a truck, and the engine 10 includes a crankcase 12 and a cylinder head 14 mounted on an upper end of the crankcase 12, and the crankcase includes A ladder frame or underframe 16 having a substantially ladder-shaped plan is fixed to the lower end of the frame 12. A crank shaft 18 is rotatably supported by the crank case 12 and the ladder frame 16.

A front plate 20 is fixed to the front ends of the crankcase 12 and the ladder frame 16, and a crank gear 22 is attached to the front end of the crankshaft 18 which extends forward through the front plate 20. The crank gear 22 drives an injection pump drive gear 28 fixed to a drive shaft 26 of a fuel injection pump (not shown) via an idle gear 24. The idle gear 24 has one end fixed to the crankcase 12 and is rotatably supported on an idle gear shaft 30 extending in the crankshaft axis direction.

An example of a conventional structure in which the idle gear shaft 30 is mounted on the front end of the crankcase 12 is well shown in an enlarged sectional view of FIG. The idle gear shaft 30 has a large-diameter portion 30a and a small-diameter portion 30b formed at one end thereof, and the large-diameter portion 30a has a large-diameter mounting hole 32 recessed in the front end portion of the crankcase 12. It is fitted inside. A driving sprocket wheel 36 is rotatably supported on the small diameter portion 30b via a bearing 34, and the idle gear 24 is fixed to a hub 36a of the driving sprocket wheel 36 via a key 38. Furthermore, an oil hole 40 extending in the axial direction and a radial oil hole 42 communicating with the oil hole 40 and supplying oil to the bearing 34 are bored inside the idle gear shaft 30. The oil hole 40 communicates with an oil passage 44 formed at the center of the mounting hole 32, and the oil passage 44 is provided in the crankcase 12 as shown in FIG. It communicates with the main oil gear rally 48 via the oil passage 46.

A thrust plate 50 for positioning the driving sprocket wheel 36 in the axial direction in cooperation with the large diameter portion 30 a is arranged at the front end of the small diameter portion 30 b of the idle gear shaft 30. The idle gear shaft 30 is fastened and fixed to the crankcase 12 by two bolts 52 and 52 'which are inserted through the gear shaft in the axial direction. One of the two bolts 52 'is a central portion of a timing gear case 54 which covers the outside of the timing gear device including the crank gear 22, the idle gear 24, the injection pump drive gear 28 and the driving sprocket wheel 36. It is fastened and fixed to the crankcase 12 together. Further, the timing gear case 54 has its outer peripheral portion fixed to the crank case 12 by a large number of bolts 56.

On the other hand, a cam shaft 58 for opening and closing an intake valve and an exhaust valve is rotatably mounted on the cylinder head 14, and a driven sprocket wheel 60 and a drive sprocket wheel 36 described above fixed to the front end of the cam shaft 58. A timing chain 62 is wound between and.

In the conventional idle gear shaft mounting structure described above, a large-diameter mounting hole 32 for receiving the large-diameter portion 30a of the gear shaft 30 is provided in the front end portion of the crankcase 12, and the large-diameter portion 30a is formed. The bottom surface of the mounting hole 32 that comes into contact with the end surface of must be accurately processed. However, it is generally difficult to grind the wide bottom surface of the large-diameter mounting hole 32 with good plane accuracy within a reasonable processing cost range. Therefore, when the large-diameter portion 30a is fitted in the mounting hole 32 and is tightly fixed to the crankcase 12 by the bolts 52 and 52 ', the idle gear shaft 30 cannot be correctly mounted parallel to the axis of the crankshaft 18. It is often mounted at a slight inclination. If the idle gear shaft 30 is mounted so as to be inclined, the idle gear 24 and the crank gear 20 and the injection pump drive gear 28 are not properly meshed with each other, causing abnormal wear and vibration of the meshing teeth. . Further, since a large-diameter mounting hole 32 must be formed in the crankcase 12 and an oil passage 44 communicating with the oil passage 46 must be bored in the mounting hole 32, the mechanical processing cost further increases. There is a problem.

[0009]

[Problems to be solved by the device]

 An object of the present invention is to improve the above-mentioned drawbacks of the conventional idle gear shaft mounting structure and to provide a simple and inexpensive structure capable of accurately mounting the idle gear shaft to the crankcase. ..

[0010]

[Means for Solving the Problems]

 The present invention was devised to achieve the above object, and an idle gear shaft for rotatably supporting an idle gear of a timing gear device is provided at one end portion in the axial direction of the idle gear shaft at a front end face of a crankcase. And a ring-shaped flat surface that is formed substantially concentric with the plug-shaped projection and is in contact with the front end surface of the crankcase. An idle gear shaft mounting structure for an engine is proposed, characterized in that a portion is fastened and fixed to the front end portion of the crankcase by a bolt that axially inserts the gear shaft.

[0011]

Embodiment An embodiment of the present invention will be specifically described below with reference to FIGS. 1 to 3. (It should be noted that re-statement of the matters already described with reference to FIGS. 1 and 2 in relation to the conventional idle gear shaft mounting structure is omitted. Further, members and portions substantially the same as or corresponding to the conventional configuration are omitted. Are denoted by the same reference numerals, and duplicate description will be omitted.)

According to the present invention, a small-diameter plug-like projection 64 is coaxially bored at the end of the large-diameter portion 30a of the idle gear shaft 30, as shown in the enlarged sectional view of FIG. Has been done. On the other hand, the crankcase 12 is provided with a small-diameter mounting hole 66 into which the plug-like projection 64 fits, and the mounting hole 66 is directly communicated with the oil passage 46 in the crankcase 12. An oil hole 40 bored along the axis of the idle gear shaft 30 opens at the rear end surface of the plug-like protrusion 64.

As shown in the drawing, the bolts 52 and 52 ′ for mounting the idle gear shaft 30 on the crankcase 12 are provided on the axial rear end surface of the large diameter portion 30 a formed on the outside of the plug-like protrusion 64. A portion of the annular plane 68 is axially inserted, and the annular plane 68 directly abuts the front end surface 70 of the crankcase 12.

According to the above-described structure of the present invention, the idle gear shaft 30 can easily ensure the plane accuracy after the small-diameter plug-like protrusions 64 are simply fitted into the corresponding mounting holes 66. Since the ring-shaped flat surface 68 and the crankcase front end surface 70 are brought into contact with each other and the bolts 52 and 52 'are tightened, the idle gear shaft 30 can be mounted in parallel with the crank axis. Therefore, the correct meshing between the idle gear 24, the crank gear 22, and the injection pump drive gear 28 can be ensured. As a result, there is an advantage that abnormal wear and vibration of the meshing teeth can be reduced. Further, the fitting accuracy between the plug-like protrusion 64 and the mounting hole 66 can be easily ensured, and the mounting hole 66 is directly communicated with the oil passage 46 in the crankcase, so that the conventional structure shown in FIG. Since it also serves as the oil passage 44, it is not necessary to further drill the oil passage 44 in the mounting hole 66, and there is an advantage that the machining process can be reduced and the manufacturing cost can be reduced.

It is obvious that the present invention is not limited to the engine in which the ladder frame is attached to the lower end of the crankcase, and can be similarly applied to the deep skirt type engine having no ladder frame.

[0016]

[Effect of the device]

 As described above, in the idle gear shaft mounting structure of the engine according to the present invention, the idle gear shaft that rotatably supports the idle gear of the timing gear device has the front end surface of the crankcase at one end portion in the axial direction thereof. And a ring-shaped flat surface which is formed substantially concentric with the plug-shaped projection and abuts on the front end surface of the crankcase. It is characterized by being tightened and fixed to the front end of the crankcase by a bolt that inserts the gearshaft in the annular plane portion in the axial direction. It is practically useful because an inexpensive structure can be provided.

[Brief description of drawings]

FIG. 1 is a front view of the entire engine showing an embodiment of the present invention.

FIG. 2 is a front view of a crankcase in the engine shown in FIG.

FIG. 3 is an enlarged sectional view of an idle gear shaft mounting portion in the engine shown in FIG.

FIG. 4 is an enlarged sectional view similar to FIG. 3 showing a conventional idle gear shaft mounting structure.

[Explanation of symbols]

 10 Engine 12 Crank Case 16 Ladder Frame 18 Crank Shaft 22 Crank Gear 24 Idle Gear 30 Idle Gear Shaft 64 Plug-like Protrusion 66 Mounting Hole

Claims (1)

[Scope of utility model registration request] 1. An idle gear shaft, which rotatably supports an idle gear of a timing gear device, is fitted into a small-diameter mounting hole formed in a front end face of a crankcase at one axial end thereof. A bolt having a plug-like projection and an annular flat surface which is formed substantially concentrically with respect to the plug-like projection and abuts on the front end surface of the crankcase, and which inserts the gear shaft in the axial direction at the annular flat surface. The idle gear shaft mounting structure of the engine characterized by being tightly fixed to the front end of the crankcase by