JPS6056670B2 - How to set shim thickness for bearing preload adjustment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is aimed at determining the optimal thickness of a shim used to adjust the preload of a bearing that pivotally supports a worm shaft that is rotatably supported in a housing in the process of assembling a steering gear of a vehicle such as an automobile. It relates to a method that can automatically calculate and display the

First, the structure of a conventional general steering gear and its assembly method will be explained with reference to FIGS. 1 and 2.
In the figure, 1 is a housing, 2 is a worm shaft, 3 is a sector shaft, and worm shaft 2 is rotatably supported on the housing 1 by two bearings 4, 4, perpendicular to the longitudinal direction of the housing 1. A worm shaft cap 12 is attached to the housing 1 at one end thereof with bolts 14 via a shim 13. A steering shaft 5 is attached to the end portion 2a of the worm shaft 2 that protrudes outward from the housing 1 in a subsequent process. Note that 2b is a cutout for neutral positioning of the worm shaft 2. The worm shaft main body portion 2c within the housing 1 has a threaded groove 6, and a ball nut 8 is supported via a large number of balls 7. A rack 9 is carved in a part of the ball nut 8, and its rotation is prevented by meshing with a sector gear 11, which will be described later, so that the ball nut 8 moves in the axial direction on the worm shaft 2 in accordance with the rotation of the worm shaft 2'. do. The sector shaft 3 is rotatably supported in the longitudinal direction of the housing 1 by two bearings 10, 10, and a sector gear 11 is carved in a position facing the rack 9 of the ball nut 8. By the way, the worm shaft 2 is connected to the steering shaft 5 and rotated, and since this rotational force is transmitted to the front shaft via the ball nut 8 and the sector shaft 3, a load acts in the axial direction of the worm shaft. Bearings 4, 4 supporting 2
It is necessary to optimize the support rigidity of the worm shaft 2 by setting the clamping force, that is, the preload applied to the bearings 4, 4 within a predetermined value or range. This preload is set by appropriately adjusting the thickness of a shim 13 interposed between the housing 1 and the cap 12. If the thickness of the shim 13 is too thick, the preload will be too small and the worm shaft 2 will have loose play.On the other hand, if the thickness of the shim 13 is too thin, the axial load on the worm shaft 2 will become large, resulting in a smooth This makes rotation difficult and results in premature bearing fatigue. In the conventional method of adjusting the shim thickness, the operator adjusts the number of shims 13 according to his/her intuition.
, tighten the bearing cap 12 with the bolt 14 with a predetermined tightening force, then rotate the worm shaft 2, measure the torque, and if this measured torque is not within the predetermined range, Remove the bearing cap 12, reinstall the shim 13, and then reinstall the bearing cap 1.
It was an extremely troublesome method, such as tightening 2.

For this reason, there is a problem that the number of man-hours is large, the efficiency is extremely low, and the work requires skill. The present invention automatically calculates the optimal shim thickness for each steering gear so that the preload of the worm shaft can be quickly set to a predetermined value when assembling the steering gear! There is also an attempt to propose a method that can also display the information. Hereinafter, the present invention will be explained in detail with reference to embodiments shown in FIGS. 3 to 5.

FIG. 3 shows an apparatus for carrying out the method of the invention.

In the figure, 1A is the steering gear before the sector shaft 3 is attached, and only the worm shaft 2 is attached by bearings 4, 4. That is, housing 1
A plurality of shims 13A in a predetermined combination are usually used as a reference before adjusting the shim thickness (for convenience of explanation below) between the The bearing gap 12 is pressed against the housing 1 by the ram x of the hydraulic cylinder device, and is attached to the housing 1 with the bolt 14 with the reference shim 13A interposed. The condition is maintained. A is a torque detection device for the worm shaft 2, and is a torque detection device for the reversible motor 20.
A socket 22 that is spline-fitted to the end 2a of the worm shaft 2 is formed on the rotating shaft 21, and a torque sensor 23 and an angle sensor 24 are interposed therein.

A motor drive circuit 25 and a sequence circuit 26 are connected to the reversible motor 20, an amplification circuit 27 and an A/D converter 28 are connected to the torque sensor 23, and a rotation angle counting circuit 30 is connected to the angle sensor 24. are connected to each other. 15 is an actuator, after placing the worm shaft 2 of the steering gear 1A in the neutral position,
2 to prevent the rod end 15 from shifting when mating.
A is fitted into the notch 2b and fixed, and is activated by a signal from the sequence circuit 26.

These are the computer 3 which is the arithmetic unit B as a whole.
Connected to 1. As this calculator 31, a minicomputer having a storage function, a comparison function, an arithmetic function, etc. is used. C is a reference signal input device for inputting predetermined information to the arithmetic device B, and includes a reference shim thickness setting signal source 32 and a torque shim thickness correlation characteristic signal source 33, details of which will be described later. Further, D is a display device, which includes a torque display section 34 that displays the measured torque on a memory scope, and a shim change display section 35 that displays the number of shims increased or decreased by type relative to the standard shim when changing the shim thickness. It has. The method of the present invention using the apparatus having the above-mentioned configuration will be described below. (1) As shown in Fig. 3, after placing the housing 1 on the base Y and setting only the worm shaft 2, the bearing cap 12 is attached via the reference shim 13A.
is fitted into the housing 1, and further pressed against the housing 1 by the ram X of a hydraulic cylinder (not shown) with the same load as when the bearing cap 12 is bolted.

A ball nut 8 is screwed onto the worm shaft 2, but the sector shaft 3 is not set. Also,
The reference shim 13A includes several types of shims 13A each having a different thickness.
1, 13A2..., select an appropriate number of shims from these, and create a plurality of shims 13A1, 13A2...
The total thickness is set to a predetermined thickness. In this example, (t1=0.762), (T2=0.254), (T
3=0.127), (T4=0.05) Ugly and four different thicknesses of shims are available. In addition, each of these shims Tl, t
Each number of sheets 2, t3, and t4 is a reference shim thickness setting signal. source 32
The signal is input to the computer 31 as a shim thickness setting signal. In the case of Fig. 3, the standard shim thickness is.

(2) Next, the actuator 15 is operated to retract the rod end 15a, and the reversible motor 20 is operated to rotate the rotary shaft 21 by a predetermined number of rotations in forward and reverse directions, thereby rotating the worm shaft 2 via the socket 22. .

At the same time, the angle sensor 24 detects the rotation angle of the worm shaft, and the torque sensor 23 detects the torque. The reversible motor 20 is controlled by a sequence circuit 26 and a motor drive circuit 25, while the detected torque signal and angle signal are transmitted by an amplification circuit 27 and an A/D converter 28, respectively.
is inputted into the calculator 31 by the rotation angle counting circuit 30. (3) The calculator 31 directly visually displays the angle signal and torque signal based on the angle signal and the torque signal, and also performs predetermined comparisons and
Perform calculations and display the results.

That is, the measured torque is displayed on the torque display section 34 as a graph showing the rotation angle of the worm shaft 2 on the horizontal axis and the measured torque on the vertical axis as shown in FIG. At this time,
The torque is the set torque. Or, whether or not the torque is within the allowable range is also displayed. Then, if the measured torque is acceptable, the shim adjustment operation is completed, and the steering gear 1A is transported to the next process as it is, and the bearing cap 12 is tightened with the bolts 14. (4) If the measured torque is unacceptable, an average value of the measured torque is determined.

Then, from this average value, the optimum shim thickness that produces an allowable torque is adjusted by the following method. That is, the calculator 31 includes a standard housing 1 and a bearing cap 1.
2. Torque shim thickness correlation characteristics obtained in advance through experiments for the combination of the worm shaft 2 are inputted as a signal from the signal source 33. Note that in the signal source 33,
This torque shim thickness characteristic is set in the form of a plot of torque values for each minute interval of shim thickness, also for convenience of automatic correction to be described later. This characteristic shows the relationship between the selected shim thickness and the torque (in this example, the average value) normally obtained by the selected shim thickness, as shown in detail in Fig. 4, and the torque from the shim thickness is The shim thickness can be determined from the torque. Now, as shown in Figure 4, the tolerance range z
The average value of the measured torque T. ．． and the set torque value L, and from this difference ΔT, the correction shim thickness Ts for correcting the torque to the set torque value Ts and the allowable shim thickness T2 corresponding to the torque allowable range Z are calculated. .
This corrected shim thickness Ts and allowable shim thickness T2 are shim t1...
...This is the target value of the correction operation amount of T4, and if the measured torque is smaller than the set torque value, the shim thickness is reduced,
If it is large, increase it. When the corrected shim thickness Ts is determined, the various shims currently installed Tl. , t2, t3
, t4 is displayed on the shim display section 35 as shown in FIG. 3. Based on the thicknesses of the various shims t1 to T4 set by the shim thickness setting signal source 33, the calculator 31 calculates the combination and number of shims t1 to ζ that fall within the allowable shim thickness Ts using the corrected shim thickness Ts as a target value. For example, when Ts=1.063Tm and T2=0.005Tm, the shim T
It is only necessary to increase the number of shims ζ by one while decreasing the number of shims ζ by two, and as a result, the optimal shim thickness is as follows.

Note that when determining the number of shims for correction, it is preferable to use as few shims as possible.
A program that preferentially determines the number of shims is preferable.

5) The shim thickness is adjusted by the above action, and after adjusting the shim according to the instructions displayed on the shim display section 35, it is checked in step (3) above whether the torque is set within the allowable range again. Confirmation is done in almost the same way.

As a result, if the measured torque is within the allowable range, the adjustment is completed, and if it is within the allowable range, the adjustment is performed again. (6) On the other hand, it may be difficult to set the optimum shim thickness even after re-adjustment. This is housing 1, cap 1
This is because the torque shim thickness correlation characteristic input to the computer 31 may not match the actual characteristic of the steering gear due to variations in manufacturing dimensions of the worm shaft 2 or the worm shaft 2. Especially when manufacturing steering gears, the machining blades etc. are replaced every time a predetermined number of machining operations are completed.
This is because the manufacturing dimensions and characteristics of these processed rods differ slightly between them. In order to prevent incorrect adjustment due to such causes, it would be possible to reset the characteristic signal for each rod, but this is troublesome, so the method of the present invention performs automatic correction as follows. As shown in FIG. 5, the torque difference ΔT is determined as described above from the average torque value Tm obtained with the reference shim, and the corrected shim thickness Ts is determined.
Furthermore, the average value TM of the torque measured again is determined from the corrected thickness and thickness.

This average value TM should originally be on the characteristic curve and approximately equal to the set value L, but because the characteristics are different, it becomes a value that deviates from the characteristic curve, as at point TM1 or point TM2 in the figure. In other words, this means that the characteristics of the steering gear that is currently being adjusted are characteristics that pass through point TM1 or point TM2, and therefore the characteristics of other steering gears on the rod to which this steering gear belongs are also similar. Since the characteristics are approximated, the characteristics stored in the computer 31 are calculated as the average torque value T. The correction is made for n or less. Figure 5.
is a case where the torque setting value Ts is smaller than the average value Tm of the actually measured torque, but conversely, the average value Tm of the actually measured torque
Therefore, when the torque setting value L is large, similar corrections are made in the range equal to or greater than the torque average value Tm. As a result, from now on. The adjustment of the shim thickness is made based on the corrected characteristics, so that the adjustment is accurate. In this automatic correction, as shown in FIG.
In order to deal with the case where a mistake is made in inserting the wrong number of shims in response to the display of No. 5, it is preferable to provide a canceling circuit to return to the initial characteristics. In the automatic correction, as a result of repeating several measurements with a small correction amount, TMl or TM
If the measurement is made to pass through 2, the influence of incorrect shim insertion can be eliminated. It should be noted that all of these functions can be easily accomplished based on the configuration shown in FIG. 3 by configuring the program of the computer 31 appropriately, so a description of the device will be omitted.

As is clear from the above explanation, according to the method of the present invention, the optimal shim thickness for each steering shaft is automatically calculated and displayed, making it extremely easy to adjust the shim thickness. Since the shim thickness can be adjusted by automatically correcting the torque shim thickness correlation characteristics, it becomes easy to set the optimum shim and assemble a steering gear with the optimum preload.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the steering gear, Fig. 2 is a sectional view taken along the line FIG. 5 is a graph for explaining the method for determining the Torque shim thickness correlation characteristic. 1... Housing, 2... Worm shaft, 4... Bearing, 12...
Bearing cap, 13...Shim, 20...
... Reversible motor, 23... Torque sensor, 31.
...Calculator, 32 ... Reference shim thickness setting signal source, 33 ... Torque shim thickness correlation characteristic signal source,
35...um display unit, A...torque detection device, B...computing device, C...reference signal input device, D...display device .

Claims (1)

[Claims] 1 In a shaft bearing assembly in which a shaft is attached to a housing via a bearing, when adjusting the preload of the bearing with a shim, fit a reference shim prepared in advance and then apply the same load as the tightening load of the bearing. While pressing the bearing, the shaft is rotated and the torque is actually measured, and the torque-shim thickness correlation characteristic obtained by pre-measuring the torque corresponding to the change in shim thickness in a standard steering gear is stored in the computer. Based on this characteristic, calculate the shim thickness that reaches the set torque from the actually measured torque, determine the corrected shim thickness for the standard shim, change the standard shim by this corrected shim thickness, and then re-measure the torque. A method for setting shim thickness for preload adjustment of a bearing, characterized in that the torque-shim thickness characteristic is corrected based on the re-measured torque.