JPS60205080A - Linear solenoid valve - Google Patents

Abstract

PURPOSE:To solve a problem on the unbalance of flow force due to diversion in a pressure fluid flow, by forming a stepped surface in a damper sleeve to be fitly attached to the inner circumference of one end at the slit side of a spool. CONSTITUTION:A damper sleeve 50 having a central hole 50a is driven in a one end inner circumference 20a at the slit side of a spool 20. This damper sleeve 50 has its axial length being longer than the overall length of a slit 21 and consists of a large diametral part to be fitted in the spool 20, a small diametral part to be loosely fitted in the spool 20 with some clearance and a stepped surface 50b of taper form connecting these small and large diametral parts. A chamfer 50c takes place for an upper end of the central hole 50a so as to make a pressure fluid flow smooth and eliminate the instability of flow force due to turbulence.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention linearly controls the bypass amount of pressure fluid flowing from the high pressure side flow path to the low pressure side flow path in accordance with the control current applied to the solenoid 1'. This is related to Surinia solenoid valve.

<Prior Art> In general, a vehicle speed-sensitive power steering device is known that can control steering force according to the vehicle speed by disconnecting communication between both end chambers of a power cylinder by a linear solenoid valve controlled according to the vehicle speed. For example, as shown in FIG. 1, a linear solenoid valve used in this type of vehicle speed sensitive power steering device has a spool 20 slidably fitted in a valve body 10 with a slit 21 formed therein. 20 is subtracted by 1 by a solenoid to which a control current corresponding to the vehicle speed is applied, thereby changing the opening area of the slit 21, thereby bypassing the pressure fluid between the first flow path P1 and the second flow path P2. ing.

In such a linear solenoid valve, a flow source acts in a direction to narrow the opening area of the slit 21 due to the influence of the flow of pressure fluid passing through the slit 21. Therefore, the flow force Fl caused by the flow of pressure fluid from the second flow path P2 to the first flow path P1 is greater than the flow force Fl caused by the flow of the pressure fluid from the first flow path P1 to the second flow path 1)2. -Somese F2 is larger.

Such a difference in the magnitude of the flow force depending on the flow direction of the fluid causes an imbalance in the opening area of the slit 21 with respect to the current value applied to the solenoid.
In the steering characteristic during high-speed running, which is shown by the solid line in the figure, an imbalance occurs in the pressure (steering force) generated when the steering wheel is turned to the left and when the steering wheel is turned to the right.

In order to eliminate such an imbalance, a damper sleeve 22, which conventionally has a center hole, is driven into one end of the spool 20 on the slit side, so that when the fluid flows from the first flow path PI to the second flow path P2, the damper sleeve 22 has a center hole. A part of the damper sleeve 22 is diverted from the slit 21 of the spool 20 to the upper part of the damper sleeve 22, and bypassed through the center hole.

As a result, when the fluid flows from the first flow path P1 to the second flow path P2, the annular working surface 2 of the damper sleeve 22
3, a downward flow force Fα is applied to cancel the flow force imbalance described above. However, in practice, it is extremely difficult to optimally design the damper sleeve, and the flow force acting on the annular action surface 23 changes as the opening area of the sulin l-21 changes, and in some areas the annular shape of the damper sleeve changes. There was a problem in that the canceling force acting on the action surface became too large and the bypass flow rate decreased as shown by the solid line in FIG.

<Objective of the Invention> An object of the present invention is to maintain a constant flow force acting on the working surface of a damper sleeve and to eliminate an imbalance in flow force caused by conversion of the flow of pressure fluid.

<Structure of the Invention> In order to achieve the above object, the present invention makes a damper sleeve fitted on the inner periphery of one end of the spool on the slit side longer than the entire length of the slit, and A stepped surface is formed between the small diameter part and the large diameter part fitted to the inner periphery of the spool, and the inner end of the slit is opened at the small diameter of the spool.

<Embodiments> The best embodiments of the linear solenoid valve of the present invention will be described in detail below with reference to FIGS. 3 to 6.

In FIG. 3, reference numeral 30 indicates a power steering device, and this power steering device 30 is formed by integrally fixing a Harzo housing 31 housing a servo valve and a power cylinder 32 in which a piston is fitted. When the servoharp is activated by operation, the pressure oil supplied from the steering pump 40 through the supply port 33 is distributed to one chamber of the power cylinder 32, and the discharge surface of the other chamber of the power cylinder 32 is
It flows out into the tank 41 from the J1' outlet 34. The power cylinder 32 is equipped with a linear solenoid valve S of the present invention that communicates both the left and right oil chambers in the power cylinder 32 according to the vehicle speed.
v is attached.

Linear solenoid valve S■ has combination 9. L-Evening CP
A speedometer SM is connected via cb). The speedometer SM uses a magnet rotated by the output shaft of the transmission to generate an on/off signal proportional to the vehicle speed.
It incorporates a reed switch that generates an off signal. The computer CP calculates the on/off signal of the reed switch into a control current according to its frequency, that is, proportional to the vehicle speed, and supplies the control current to the linear solenoid valve SV.

Fig. 4 shows in detail the internal structure of the beam near solenoid valve S■, in which the valve body 10 made of a magnetic material has a through hole 32a provided in the peripheral wall of the power cylinder 32 in the radial direction.
The boat 12 has a protruding part jOa that is liquid-tightly fitted into the large diameter part of the boat 12, and the protruding part 10a has a first flow path l) opening -4' to the left chamber of the power cylinder 32. An inner hole 11 communicating with the inner hole 11 is provided. In addition, the protrusion 10
A union 24 h"Js4 made of a non-magnetic material such as stainless steel is attached to the inner end of the union 24, and the inner end of the union 24 is fitted into the small diameter part of the through hole 32a in a fluid-tight manner.
J.Nion 24 is provided with a boat 13 whose one end opens into the second passage P2 leading to the right chamber of the power cylinder 32 and whose other end opens into the inner hole 11.

Inside the sleeve 26, which is fixed to the outer end protrusion of the valve body 10 by a screw or the like, a ring 27 made of a magnetic material is fitted and fixed. A cylindrical portion 27a is formed at the inner end of the yoke 27. The cylindrical portion 27a accommodates the outer end of the cylindrical spool 20 with a predetermined tension.

A solenoid 29 wound around a bobbin 28 made of a non-magnetic material is provided on the outer periphery of the sleeve 26.
A cover 15 made of a magnetic material surrounding the knob body 9 and having an inner end joined to the knob body 10 is fixed to the upper end of the yoke 27 by bolts 16.

The cylindrical spool 20 is made of a magnetic material, and is fitted into the inner hole 11 of the valve body 10 with a force of 137 i+J, and is passed through by the bias of a spring 25 made of stainless steel housed in the inner hole 27b of the yoke 27. It is held at the descending end that joins the Fuyu J-on 24. However, this spool 2
As shown in FIG. 4, the inner end of the spool 20 is provided with radially cut bypass slits 21 and 21 having a predetermined length in the axial direction. cuts off the communication with the boat 12, and due to the upward displacement of the spool 20, the boat 12 and the boat 13
A bypass passage is formed between them.

Further, a damper sleeve 50 having a center hole 50a is driven into the inner periphery 20a of one end of the spool 20 on the slit side. The damper sleeve 50 has an axial length r = longer than the entire length of the slit 21, and includes a large diameter portion that fits into the spool 20, and a small diameter portion that fits loosely into the spool 20 with a gap. It consists of a tapered stepped surface 50b connecting the small diameter part and the large diameter part. The upper end of the center hole 50a is chamfered 50c to smooth the flow of the pressure fluid and eliminate instability of the flow force caused by turbulence.

In the structure described above, when a control current corresponding to the computer CP and III is applied to the solenoid 29 of the linear solenoid valve S, the solenoid 29 causes the cover 15,
Valve body 10, spool 20, yoke 27, cover 1
A magnetic flux is formed through the solenoid 29 and the solenoid 29, and an attractive force proportional to the current applied to the solenoid 29 acts on the spool 20. However, if the vehicle speed is lower than the predetermined speed, the spool 20 is not displaced by the force of the spring 25, and communication between the boats 12 and 13 leading to the left and right compartments of the power cylinder 32 is cut off. be.

When the vehicle speed exceeds a predetermined speed, the suction force of the solenoid 29 overcomes the biasing force of the spring 25 and the spool 2
0 begins to be displaced. As a result, the port I-21 is opened to the boat 12, and a bypass passage is formed between the boats 12 and 13. Furthermore, since the opening area of the slit 21 changes linearly according to the current applied to the solenoid 1'29, the bypass flow rate bypassed between the left and right compartments of the power cylinder 32 increases as the vehicle speed increases. As a result, the steering characteristic changes from the broken line to the solid line in FIG. 6, and the steering force changes linearly in accordance with the vehicle speed, resulting in high-speed stability.

By the way, by displacing the spool 20, the high pressure fluid in the boat 12 communicating with the left chamber of the power cylinder 32 is transferred to the power cylinder 3 via the bypass passage and the boat 13.
In the case of bypassing to the right ventricle of No. 2, the high-pressure fluid passing through the slit 21 passes through the limited annular gap between the small diameter part of the damper sleeve 50 and the inner circumferential surface 20a of the spool 20. flow, and thus flows out into the boat 13 through the central hole 50a of the damper sleeve 50. As a result, a canceling force Fα in the same direction as the flow force F1 acts on the single-step tapered surface 50b of the damper sleeve 50. Therefore, the pressure fluid is bypassed from the boat 12 to the boat 13.
- the force is increased and this flow force is approximately equal to the flow force F2 when the pressure fluid is bypassed from the boat 13 to the boat 12; Moreover, since the fluid pressure acting on the single-step tapered surface 50b of the damper sleeve 22 is not affected by the position of the spool 20, it is possible to prevent imbalance in the bypass flow rate when turning left and right due to the difference y4 in flow force. . The chamfer 50c formed at the upper end of the center hole 50a of the damper sleeve 50 smoothes the flow of the bypass flow (2) that flows into the center hole 50;1 from the annular gap between the small iY portion of the damper sleeve 50 and the spool 20. This is to prevent instability of the fumes Fα due to turbulent flow.

<Q Results of the Invention> As described above, the present invention provides a damper sleeve fitted to the inner periphery of one end of the spool on the slit side, which is longer than the entire length of the slit, and the inner end of the damper sleeve has a small diameter. A stepped surface is formed between the inner end of the damper sleeve and the large diameter part that is fitted onto the inner periphery of the spool, and the inner end of the slit is opened in this small diameter part. The pressure fluid flowing out from the annular gap between the damper sleeve and the spool is applied to the stepped surface, which applies a canceling force to the damper sleeve in the direction of narrowing the slit opening area, thereby reducing the imbalance of fluid pressure acting on the spool itself. This can be solved by the thrust force acting on the damper sleeve, and when applied to a vehicle speed sensitive power steering system, it is possible to eliminate the imbalance in steering force when turning the bundle to the left and right. There is an effect that can be done.

[Brief explanation of drawings]

Figure 1 is a sectional view of the main parts of a conventional Norinia solenoid valve.
Fig. 2 is a diagram showing the relationship of bypass flow (■) to applied current, Fig. 3 is a schematic diagram of vehicle speed sensitive power steering system 6 using the linear solenoid valve of the present invention, and Fig. 4 is a diagram showing the relationship between bypass flow (■) and applied current. 5 is an enlarged sectional view of the main part of FIG. 4, and FIG. 6 is a characteristic diagram showing the relationship between manual torque and steering pressure. 10...Valve body, 11...Inner hole, 12゜13.
...Boat, Pl, P2-...Channel, 2°...Spool, 21...Spool, To, 5o..., Damper sleeve, 50a...Center hole, 5°1)... tipper cross section,
50c... Chamfer. Patent applicant Toyota Machinery Co., Ltd.

Claims (2)

[Claims] (1) A valve body that has two boats that communicate with two channels through which high-pressure fluid and low-pressure fluid selectively flow, and that has inner holes that these boats open, and an inner hole in each valve body. A cylindrical spool that is slidably fitted inside the spool and has a slot cut out in the radial direction on one end side to form a bypass passage whose opening area changes according to axial displacement, and a cylindrical spool that is proportional to vehicle speed, etc. a solenoid to which a control current is applied and which attracts the spool with an attraction force corresponding to the control current; and a spring which biases the spool in a direction in which the slit closes the bypass passage. A damper sleeve that is longer than the entire length of the slit is fitted onto the inner periphery of one end of the spool on the slit side, and the inner end of the damper sleeve is a small diameter part and a large diameter part is fitted onto the inner periphery of the spool. and a step surface is formed between the damper sleeve and the inner end of the slit to open in a small diameter portion of the damper sleeve. (2) The linear solenoid valve according to claim 1, wherein a chamfer is formed on the open end of the damper sleeve on the small diameter side.