JPS632582Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wheel shaft for a turbocharger, and more particularly to a wheel shaft for a relatively small turbocharger used in internal combustion engines for automobiles.

A relatively small turbocharger used in an automobile internal combustion engine, etc. has a wheel shaft that supports a compressor wheel and a turbine wheel at both ends, and the wheel shaft is generally attached to the housing of the turbocharger. The wheel mounting shaft has a support shaft supported by a bearing device, and a wheel mounting shaft that is coaxially connected to the support shaft at one end of the support shaft and has a smaller diameter than the support shaft. A compressor wheel is supported at one end, and a turbine wheel is connected to the other end by upset welding or the like.

The wheel shaft as described above has a step at the connection between the support shaft and the wheel mounting shaft, and this step receives the thrust force of the wheel shaft and controls the axial mounting position of the wheel shaft and compressor wheel. When a stepped shaft like this rotates at high speed, the difference in rigidity between the support shaft and the wheel mounting shaft causes vibrations at the stepped section, which causes the mounting shaft to swing and cause the wheel to mount. The compressor wheel attached to the shaft causes an oscillating motion. This oscillating motion becomes large at resonance, creating the risk that the compressor wheel will come into contact with the turbocharger housing.

The object of the present invention is to provide an improved wheel shaft for a turbocharger that has a low vibration level during high-speed rotation and reduces the oscillating motion of the compressor wheel compared to the prior art.

According to the present invention, this purpose is to provide a support shaft supported by a bearing device, and a wheel mounting shaft portion coaxially connected to the support shaft at one end of the support shaft and having a smaller diameter than the support shaft. This is achieved by a wheel shaft of a turbocharger having a wheel shaft having a small diameter shaft portion having substantially the same diameter as the wheel mounting shaft portion at an axially intermediate portion of the support shaft portion.

According to this configuration, since the support shaft portion has a small diameter shaft portion having substantially the same diameter as the wheel attachment shaft portion in the axially intermediate portion thereof, the rigidity of the support shaft portion and the wheel attachment shaft portion is increased. As a result, the vibration caused by the stepped part of the connection between the two shafts becomes smaller than that of the conventional type which does not have a small diameter shaft as described above, and the neck of the compressor wheel decreases accordingly. Swinging motion is reduced compared to conventional ones. Additionally, by providing a small-diameter shaft section in the axially intermediate portion of the support shaft section, the rigidity of the entire wheel shaft is lower than before, which lowers the resonance frequency of the wheel shaft and reduces vibration during resonance. This also reduces the oscillating movement of the compressor wheel and eliminates the risk of the compressor wheel coming into contact with the housing of the turbocharger.

The diameter and axial length of the small diameter shaft provided in the support shaft are determined in order to satisfy the required mechanical strength of the wheel and to equalize the rigidity of the support shaft and the wheel mounting shaft. may be approximately equal to the diameter of the wheel attachment shaft portion, and the axial length may be an axial length extending over substantially the entire region of the support shaft portion that does not engage with the bearing device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below by way of example with reference to the accompanying drawings. In the figure, 1 indicates the housing of the turbocharger, and 2 indicates the wheel shaft.

The wheel shaft 2 has a support shaft portion 3 and a wheel mounting shaft portion 4 coaxially connected to the support shaft portion at one end of the support shaft portion 3 and having a smaller diameter than the support shaft portion. The support shaft portion 3 has a small diameter shaft portion 5 at its axial center, and bearing shaft portions 6 on both sides of the small diameter shaft portion.
have. The wheel shaft 2 has two bearing shafts 6
It is rotatably supported by the housing 1 by a floating bearing device 7, and a turbine wheel 8 is integrally connected to the other end of the support shaft portion 3 by upset welding.

The wheel mounting shaft portion 4 includes a thrust collar member 10 having an annular outer circumferential groove 9 and a spacer member 11.
and a compressor wheel 12 are mounted in order, and these are connected to the support shaft 3 and the wheel mounting shaft 4 by a nut 14 screwed into a threaded part 13 provided at the tip of the wheel mounting shaft 4. The nut 14 is sandwiched between an annular stepped portion 15 existing at the connecting portion of the wheel and the nut 14, and is fixedly supported on the wheel mounting shaft portion 4. A thrust plate 16 fixed to the housing 1 is provided in the outer peripheral groove 9 of the thrust collar member 10.
are engaged, thereby restricting the reception of the thrust force of the wheel shaft 2 and the axial mounting position with respect to the housing 1.

The small-diameter shaft portion 5 provided at the center in the axial direction of the support shaft portion 2 is provided in order to equalize the rigidity of the support shaft portion and the wheel mounting shaft portion.
Its diameter is approximately equal to the diameter of the wheel mounting shaft portion 4. Incidentally, sleeves 17 are fitted into the small-diameter shaft portion 2 to restrict movement in the axial direction of the two floating bearing devices 7 located on both sides thereof.

FIGS. 2 and 3 are graphs comparing the vibration characteristics of a wheel shaft according to the present invention and a conventional wheel shaft, respectively. Figure 2 shows the vibration acceleration characteristics with respect to the rotational speed of the wheel shaft, and Figure 3 shows the amplitude characteristics with respect to the vibration frequency of the wheel shaft. In both graphs, A indicates the vibration of the wheel shaft according to the present invention. B shows the vibration characteristics of a conventional wheel shaft.

From the graph shown in Figure 2, it can be seen that the wheel axle that has a small diameter part in the axial middle part of the support shaft has a lower vibration level than the conventional wheel axle that does not have a small diameter part in the support shaft. is understood.

The excitation force of the vibration of the wheel shaft is the unbalanced weight of the rotating part, and the higher the rotation speed, the greater the excitation force. Therefore, the resonance frequency of the entire wheel shaft is in a lower frequency range where the excitation force is weaker, that is, in a lower rotational speed range of the wheel shaft, the smaller the resonance vibration can be suppressed. When a small-diameter shaft portion is provided in the support shaft portion, the rigidity of the entire wheel shaft decreases, and as is clear from the graph in FIG. 3, the resonance frequency of the wheel shaft decreases. The amplitude of the vibration caused by the vibration is reduced, the oscillation of the compressor wheel during resonance is reduced, and there is no risk of the compressor wheel coming into contact with the housing.

Although the present invention has been described in detail with respect to specific embodiments above, it will be appreciated by those skilled in the art that the present invention is not limited to this and that various embodiments are possible within the scope of the present invention. It should be obvious.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing the main parts of an embodiment of a turbocharger having a wheel shaft according to the present invention, Fig. 2 is a graph showing the vibration acceleration characteristics with respect to the rotational speed of the wheel shaft, and Fig. 3 is a graph showing the vibration acceleration characteristics of the wheel shaft. 3 is a graph showing amplitude characteristics with respect to frequency. 1...Housing, 2...Wheel shaft, 3...
Support shaft section, 4...Wheel mounting shaft section, 5...Small diameter shaft section, 6...Bearing shaft section, 7...Floating bearing device, 8...Turbine wheel, 9...Outer circumferential groove, 10...Thrust Collar member, 11... Spacer, 12... Compressor wheel, 13...
Threaded part, 14... Nut, 15... Stepped part, 16...
...Thrust plate, 17...Spacer.

Claims (1)

[Scope of utility model registration request] A wheel shaft for a turbocharger having a support shaft supported by a bearing device, and a wheel mounting shaft having a smaller diameter than the support shaft and coaxially connected to the support shaft at one end of the support shaft, A wheel shaft having a small diameter shaft portion having substantially the same diameter as the wheel mounting shaft portion at an axially intermediate portion of the support shaft portion.