JPS63267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a power steering device having a planetary gear mechanism in a control input section.

Conventionally, many power steering devices of this type have been proposed by the present applicant (for example, see Japanese Patent Application Laid-open No. 49-85728 and Japanese Patent Application Laid-open No. 50-64927, etc.).
The structure of these basic parts is as follows.

In Fig. 1, 1 is a cylinder housing, 2 is a cylinder housing, and 2 is a cylinder housing.
is a differential mechanism housing, and 3 is an input shaft connected to the handle. 4 is the sector gear, which is connected to the pitman arm of the steering wheel.
Finally, the sector gear 4 rotates (output) in proportion to the rotation (input) of the input shaft 3, and steers the steered wheels. A piston 5 that meshes with a sector gear 4 is disposed within the cylinder housing 1, and defines working chambers A and B on both sides. The cylindrical screw shaft 6 is screwed into the piston 5 through a row of balls arranged in a spiral groove on the inner peripheral surface thereof, and is connected to the input shaft 3 via a torsion bar 9 by pins 7 and 8. It has been done.

As the planetary gear mechanism C, input shaft 3
A circumferential stopper portion 10 is formed at the opposing end of the screw shaft 6, so that when the shafts 3 and 6 are in a predetermined relative rotation angle or more, they abut against each other to transmit rotational torque and restrict twisting of the torsion bar 9. At the same time, a common cylindrical sun gear 1 is provided on the outer periphery of the end of both shafts 3 and 6.
1 is rotatably fitted and arranged, and this sun gear 1
A plurality of planet gears 12a, 12b are formed on the outer periphery of the input shaft 3, and a plurality of planet gears 12a, 12b, which mesh with these toothed parts 11a, 11b, are connected to the input shaft 3 and the screw shaft, respectively, using pins 13a, 13b. Symmetrically arranged at each end of 6. These planet gears 12a, 12b
The outside of the rod 1 is meshed with a rotatable ring gear 14a and a fixed ring gear 14b, respectively, and one of the rotatably supported ring gears 14a is connected to the rod 1.
5 to the spool 16 of the control valve 17 shown in FIG. 2, and the other ring gear 14b is fixed to the housing 2. As the spool 16 moves, the control valve 17 connects the annular ports P, T, M _A M _B as appropriate, and selectively supplies pressure fluid to the working chamber A or B defined in the cylinder housing 1. do.

When the input shaft 3 is rotated by turning the steering wheel, the sector gear 4 connected to the steering wheel can be considered to be in a fixed state due to the large ground resistance of the wheel. 5. Further, the screw shaft 6 is stationary, and the sun gear 11 is also held in a fixed state like the ring gear 14b since the planet gear 12b cannot revolve. Therefore, since the sun gear 11 is in a fixed state, the planet gear 12a on the input shaft 3 side revolves while twisting the torsion bar 9 and rotates within the relative rotation angle range until the stopper portion 10 abuts, and the ring gear 14a Rotate to move the spool 16. The switched control valve 17 delivers pressurized fluid from the hydraulic pump to one of the compartmented working chambers A or B in the piston 5, while simultaneously returning the working fluid in B or A to the tank. Along with this, the piston 5 begins to move and rotates the sector gear 4. At the same time, the rotational force (steering force) of the input shaft 3 is transmitted to the other screw shaft 6 while twisting the torsion bar 9, so the movement of the piston 4 causes the screw shaft 6 to rotate in the same direction as the input shaft 3. Sun gear 11 begins
eventually begins to rotate at the same rotational speed as these with a slight rotational phase delay. The planet gear 12b that meshes with the sun gear 11 is connected to the ring gear 1.
4b is fixed, it starts to revolve, and on the other hand, the planet gear 12a that was rotating the ring gear 14a, due to the rotation of the ring gear 11, rotates and revolves in parallel in the same way as the planet gear 12b on the screw shaft 6 side. Result ring gear 1
4a is stopped at that position. That is, the control valve 17 is maintained in the switched state, and pressurized fluid continues to be supplied into the working chamber until the input shaft 3 is stopped.

As the screw shaft 6 rotates, the piston 5 that is engaged with it moves by a pitch proportional amount, but this movement is performed smoothly by the pressure fluid supplied to the working chamber A or B, and the operator rotates sector gear 4 with extremely little force,
It is possible to perform conversion operations. While the input shaft 3 is rotating, the piston 5 is moved by the working fluid by an amount proportional to this pitch and follows.

When the input shaft 3 is stopped, the sun gear 11 rotates in the opposite direction by an amount equivalent to the amount of twist applied to the torsion bar 9 and then stops. Since the planet gears 12a and 12b continue to rotate for a short time until they stop, the ring gear 14a, which has been stopped until now, rotates in the opposite direction and stops at the initial position. In other words, the ring gear 14a rotates by an amount equivalent to the amount of twist of the torsion bar 9 applied when the input shaft 3 rotates, and the spool 16 also returns to the neutral position accordingly.

As a result of the above configuration, the device has the advantage of being made more compact. However, on the other hand, when this type of planetary gear train is used, it is accompanied by backlash due to the meshing of the gears.According to experiments, it is shown in FIG. It has become clear that there is a problem in which minute fluctuations (so-called chatter) occur in the characteristic relationship between input and output as shown.

As for the cause of this chatter, when we investigate the relationship between the input angle and the chatter, we find that the angle of one pitch of chatter is approximately equal to the number of teeth Z of the ring gear, which is 360°/Z, and the meshing state of the gears in the planetary gear mechanism has a large influence. It has been confirmed that it will be given.

In other words, it is the ring gear 14a that operates the control valve 17, and due to the relationship between the valve stroke and the rotation amount of the ring gear, even if the ring gear 14a makes a small rotation, the flow rate change of the control valve 17 will be considerably large. After all, if the ring gear 14a were to undergo any rotational displacement, chatter would immediately occur in the input-output characteristics.

Since the ring gear 14a is driven via the planet gear 12a, if play or fluctuation occurs in the meshing state of these gears, or if the meshing ratio is low, stable rotation transmission support cannot be obtained. causes minute rotational displacement, which causes the chatter mentioned above.

In other words, even if the machining accuracy of each gear is good, if the meshing ratio is particularly low, for example, when only one pair of teeth mesh, the ring gear can be reversed until the next pair of teeth mesh. , the meshing becomes unstable and chatter occurs.On the other hand, if the meshing ratio of the gears is high, the ratio of multiple sets of teeth meshing at the same time increases accordingly, so the slippage between the contact teeth of each set increases. It is almost negligible, and since the ring gear is stably supported for rotation transmission, there is no reverse rotation and chatter is reduced accordingly.

By the way, the current planet gear 12a is
As is clear from the figure, in order to equalize the load distribution, three planet gears are arranged at equal intervals of Θ=120°, and in this state, each planet gear 12a is in exactly the same meshing state with each other. Since the sun gear 11 and the ring gear 14a are in mesh with each other, the overall meshing ratio is the same as that of a single planet gear 12a.

In other words, when the teeth of the planet gear 12a are meshing with the sun gear 11, the ring gear 14
For example, when the planet gear 12a meshes with the sun gear 11 with the teeth of the planet gear 12a, the ring gear 14a meshes with the ring gear 14a with the tooth valleys.
There is no difference in the meshing state with respect to 4a,
Such a relationship exists between the other two planet gears 12.
A is also maintained in the same way, so overall the sun gear 11 is controlled by three planet gears 12a.
Even though the meshing occurs between the ring gear 14a and the ring gear 14a, the meshing ratio is the same as that of a single planet gear 12a.

Now, the number of teeth of sun gear 11 Z ₁ = 42, ring gear 1
When calculating the meshing ratio with the number of teeth Z ₂ = 66 in 4a, it is approximately
However, the engagement ratio
1.48 means, for example, as shown in Figure 5A, if the time between a pair of teeth starts and ends meshing is 1, then the time between the beginning and end of meshing is 1.48.
Between 0.48 and 2 pairs of teeth are engaged, but the other
Between 0.52 and 0.52 means that only one pair of teeth are engaged, and as a result, only a low engagement ratio can be ensured, causing the above-mentioned problems in engagement and making it difficult to eliminate chatter. Additionally, the easiest way to increase the meshing ratio is to increase the number of teeth, but in order to increase the number of teeth without increasing the installation space, the only way to increase the number of teeth is to lower the module, which would result in significant changes and problems with strength. It's coming.

In view of the above, the present invention has been proposed by varying the arrangement angle intervals of the planet gears that mesh with the ring gear and the sun gear within a range where their mutual positional relationship does not significantly disturb load distribution, so as to adjust the meshing state of each planet gear with the sun gear and the ring gear. By setting them differently, the overall engagement rate is significantly increased and play in engagement is reduced.
The present invention provides a power steering device in which minute fluctuations in input-output characteristics are extremely small.

Examples will be described below based on the drawings.

FIG. 4 is a front view of the planetary gear mechanism, in which the number of teeth of the sun gear 11a is Z ₁ =42, the number of teeth of the ring gear 14a is Z ₂ =66, and three planet gears 12A, 12
B, 12C are arranged so that the meshing state of one of them is exactly opposite, and Θ= in the clockwise direction with respect to the first planet gear 12A as a reference.
The second planet gear 12B is located at the 90° position, and the angular spacing Θ ₂ between the second planet gear 12B and the planet gear 12B is between 210° and 240°, that is, 240° in the case of the present invention.
The third planet gear 12C is arranged at a position of =150° (Θ ₃ =120°). For reference, the conventional arrangement at equal intervals of 120 degrees is also shown.

In this case, according to the meshing theorem of planetary gears, the meshing state is reversed every 30 degrees with the planet gear 12A as a reference.

For example, when the standard planet gear 12A meshes with the sun gear 11a through its teeth, suppose that it also meshes with the ring gear 14a through its teeth.
At a position shifted by 30 degrees, the tooth meshes with the sun gear 11a at the tooth valley, and also meshes with the ring gear 14a at the tooth valley, and at a position shifted by 60 degrees, the gear returns to its original position and the teeth mesh together.

Therefore, this meshing state is 30° - reversed,
60° - same, 90° - reversed, 120° - same, 150° - reversed, etc.

Therefore, the second planet gear 12B is in an opposite meshing state to the meshing state of the reference planet gear 12A, and the third planet gear 12C is in a meshing state opposite to that of the reference planet gear 12A.
is in an intermediate state of engagement.

Therefore, planet gears 12A, 12B and 1
Even if the individual meshing ratios in 2C and 2C are the same as in the past, since the mutual meshing states are different, the overall meshing contact state increases accordingly, and in the present invention, the overall meshing ratio For example, as shown in Figure 5B, the area where two pairs of teeth mesh increases, so stable rotation transmission support can be obtained without play, and rotational deviation does not occur. It is possible to create a trowel that achieves a state extremely close to the minimum engagement ratio of 2.0.

Note that the planet gear 12C, which is in the intermediate meshing state, may be arranged at equal angles to the other planet gears 12A or 12B depending on the case. In this case, considering the load balance, the planet gears 12A and 12B may The angular interval between the planet gears 12A and 12C is preferably set to 90°, and the angular interval Θ ₃ =135° between the planet gears 12A and 12C.

As a result of the above configuration, the ring gear 14a
For planet gears 12A, 12B, 12
The overall meshing ratio of C is close to approximately 2.0, and there is extremely little backlash or slippage, and therefore no slight rotational displacement occurs.
It is possible to reliably prevent a minute stroke displacement of the control valve 17 due to a slight rotational displacement of the ring gear 14a caused by a meshing gap between one pair of teeth meshing and the next tooth meshing.

As a result, the flow rate controlled via the control valve 17 can be stabilized without fluctuations, so that the so-called chatter phenomenon can be eliminated to the extent that it can be practically ignored. In addition, the number of teeth of the ring gears 14a, 14b and the sun gear 11 is 3, which is the planet gear 12.
Since a, 12b, and 12c are set to multiples of 3, the planet can rotate at a predetermined position and is configured so that no feed in the revolution direction occurs.

As described above, according to the present invention, the angular spacing between the planet gears is made different, and the meshing states of the planet gears with respect to the ring gear and the sun gear are made different, thereby creating a meshing state with a large amount of meshing contact. However, it is possible to support stable rotation transmission of the ring gear and suppress minute stroke displacement of the control valve, thereby avoiding chatter in the power steering input-output characteristics and providing smooth proportional characteristics. It is possible to provide a power steering device with improved steering feel and to improve its steering feeling.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the conventional device, FIG. 2 is a sectional view taken along the line -- in FIG. 1, FIG. 3 is its output characteristic diagram, FIG. Figures A and B are graphs modeling the meshing state of the planetary gear portion. 3...Input shaft, 4...Sector gear,
5... Piston, 6... Screw shaft, 10...
Circumferential stopper part, 11... Sun gear, 12A, 12
B, 12C...Planet gear, 14a, 14b...
Ring gear, 16...spool, 17...control valve.

Claims (1)

[Claims] 1. A mutually common sun gear so that a control valve for controlling fluid supplied to the power cylinder is operated in response to a differential state between an input shaft and a screw shaft, which are linked via a torsion bar. In a power steering device in which switching is controlled via a ring gear on the input shaft side of two sets of planetary gear mechanisms combined in series via a A power steering device comprising at least three interposed planet gears arranged at different angular intervals so that at least one of the states of engagement with the sun gear and the ring gear is different from the others. 2 The meshing states of the planet gears with respect to the sun gear and ring gear are as follows: When the first planet gear is meshed with tooth ridges, the second planet gear is meshed with tooth troughs, and the third planet gear is in an intermediate mesh state. The power steering device according to claim 1, wherein the power steering device meshes with the power steering device so that