JPH0226775Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The invention consists of a pinion shaft connected to a handle shaft,
A gear housing with a rack shaft connected to the steering wheel and a cylinder tube with two power cylinder chambers are integrated, and the rack shaft is selectively power assisted in the steering direction. The present invention relates to a pinion type power steering device.

(Prior Art) A rack-and-pinion power steering device as shown in FIGS. 1 to 3 has been devised. Reference numeral 1 denotes a gear housing made of aluminum alloy, on which a pinion shaft 2 connected to a handle shaft is mounted so as to be rotatable, and a gear housing 1 is mounted so that a pinion shaft 2 connected to a handle shaft can rotate.
a and the pinion teeth mesh to allow the rack shaft 3 to slide. 4 is a cylinder tube formed from a steel pipe, and the outer periphery of the left end casting part has three holes 4a as shown in Fig. 2 or three protrusions 4b as shown in Fig. 3.
When the gear housing 1 is cast, the rack shaft 3 is slidably inserted into the cylinder tube 4, and the piston 5 is fixed to the rack shaft 3 at approximately the center of the cylinder tube 4, and two power cylinders on the left and right are formed. It forms chambers 6 and 7. 8,9
is a stopper, 10, 11 is a seal member, 12,
A pressure oil pipe 13 connects the power cylinder chambers 6, 7 and the valve housing 14.

Since the coefficient of thermal expansion of aluminum alloy is larger than that of steel, when the aluminum alloy of gear housing 1 solidifies, the outer periphery of cylinder tube 4 is tightly tightened, and the aluminum alloy or convex portion 4b that has entered hole 4a is tightened.
However, due to the generation of gas during casting, the shape of the holes, and the protrusions, the adhesion of the integrally cast part tends to be insufficient, and as a result, the large compression force and pull-out force due to hydraulic pressure are likely to be insufficient. If it acts repeatedly,
There was a drawback that it was easy to loosen and come off.

Further, as shown in Japanese Utility Model Application Publication No. 58-157868, in a power steering device in which one end of a cylinder tube made of steel is press-fitted into a gear housing made of aluminum and joined together, one end of the cylinder tube is press-fitted into a gear housing made of aluminum. A power steering device is known which is characterized in that a spiral groove is formed on the inner peripheral surface of the cylinder tube, and the gear housing is deformed by a portion other than the groove at one end of the cylinder tube to connect the cylinder tube and the gear housing. However, the coupling force is obtained by deforming the gear housing, which poses problems such as deteriorating the straightness of the cylinder tube and not being able to obtain sufficient coupling force.

(Purpose) This invention is a cylinder tube formed from a steel pipe that is cast into an aluminum alloy gear housing and integrated into it, so that it will not loosen or come off even if a large compression force or release force is applied by the pressure oil of the power steering. The aim is to reliably prevent this with simple means.

(Example) FIGS. 4 to 6 show an example of the present invention.
Reference numeral 21 is a gear housing made of aluminum alloy, and a pinion shaft 22 connected to the handle shaft is mounted so that it can rotate, and the rack teeth 23a of the rack shaft 23 mesh with the pinion teeth, so that the rack shaft 23 slides. It's getting old. Reference numeral 24 denotes a cylinder tube formed from a steel pipe, and the outer periphery of the cast part on the left end is provided with a rough surface 24a with many unevenness uniformly formed by knurling, threading, etc., and the rough surface 24a is formed into the gear housing 21 by casting When molded, it is integrated.
25 is a piston, 26 and 27 are two power cylinder chambers, 28 and 29 are stoppers, 30 and 31
is a sealing member, and 32 and 33 are pressure oil pipes that connect the power cylinder chambers 26 and 27 and the valve housing 34.

Next, the effect will be explained. When the handle is rotated, the handle shaft rotates, and the pinion teeth of the pinion shaft 22 fixed to the handle shaft and the rack shaft 23 are rotated.
The rack teeth 23a mesh with each other, and the rack shaft 23 slides in the axial direction as the handle rotates, thereby rotating the steering wheel. Now when turning to the left, the pinion shaft 22 rotates to the left,
Move the rack shaft 23 to the left. At this time, pressure oil from a pump (not shown) is switched by a known valve device according to the steering wheel switching resistance, and is sent from the pressure oil pump 33 to the power cylinder chamber 27 on the right side, and moves the piston 25 to the left side. power assist by sliding the rack shaft 23 to the left. At this time, a pullout load acts on the cylinder tube 24 in the direction of pulling it away from the gear housing 21 due to the reaction of the pressure oil. This pull-out load is normally received by the shrinkage force of the aluminum alloy at the length l and diameter d of the integrally cast part, and the frictional force caused by the pressing force during die casting, but the present invention further applies a large number of pull-out loads by knurling, threading, etc. The rough surface 24a formed of uniform irregularities has sufficient durability against pull-out loads because the irregularities have a small height and a large contact surface.

(Effects) According to the present invention, a rough surface with many uniform irregularities formed by knurling, threading, etc. is provided on the outer periphery of the cast part at one end of a cylinder tube formed from a steel pipe, and the rough surface is cast when casting the gear housing. Since it is an integral part, it can sufficiently withstand the large compressive force and withdrawal force caused by the power steering pressure oil that acts on the integrally cast part of the cylinder tube and gear housing.

[Brief explanation of the drawing]

Fig. 1 is a cutaway front view of the main part of the conventional device, Fig. 2 is a side sectional view of the main part of the conventional device of a first comparative example, Fig. 3 is a side sectional view of the second comparative example, and Fig. 4 is a side sectional view of the main part of the conventional device. FIG. 5 is a front cross-sectional view of the integrally cast part of FIG. 4, and FIG. 6 is a cross-sectional view taken along the line AA in FIG. 4. 21... Gear housing, 22... Pinion shaft, 23... Rack shaft, 24... Cylinder tube, 24a... Rough surface, 25... Piston, 2
6, 27...Power cylinder chamber, 32, 33...
...Pressure oil pipe, 34...Valve housing.

Claims (1)

[Scope of utility model registration request] The gear housing and cylinder tube are integrated, and the piston is fixed to a rack shaft that is arranged so that it can slide through the gear housing and cylinder, and both ends of the cylinder are sealed to provide two power outputs on both sides of the piston. forming a cylinder chamber,
A rack-and-pinion power steering system in which power assists the rack in the steering direction via a piston by selectively supplying and discharging pressure fluid to and from two power cylinder chambers using an operating valve in the valve housing. In the equipment, a rough surface part with many uniform irregularities formed by knurling, screw machining, etc. is provided on the outer periphery of the cast part at one end of the cylinder tube formed from a steel pipe, and the rough surface part is integrally molded when casting the gear housing. A rack-and-pinion power steering system.