JP3554839B2 - Power cylinder for power steering device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a power cylinder used as a source of a steering assist force in a power steering apparatus for an automobile.
[0002]
[Prior art]
2. Description of the Related Art In recent years, automobiles are widely equipped with a power steering device (power steering device) in order to reduce the labor required for steering (steering wheel) operation for steering and to obtain a comfortable steering feeling. This power steering device is roughly classified into a hydraulic type and an electric type according to a source of a steering assist force.
[0003]
In a hydraulic power steering device, a power cylinder, which is a source of a steering assist force, slides a piston supported by a support shaft in an axial direction inside a cylinder chamber formed in a part of a steering mechanism. This is a hydraulic cylinder which is movably fitted and has a pair of oil chambers which are liquid-tightly sealed on both sides of the piston. Hydraulic oil corresponding to the operation of the steering wheel is selectively supplied and discharged to both oil chambers of the power cylinder, and an oil pressure (steering assist force) corresponding to a pressure difference between the two oil chambers is steered through the piston. Steering is assisted by being added to the steering mechanism.
[0004]
The specific configuration of the power cylinder differs depending on the type of the steering mechanism. For example, in a rack-and-pinion type steering mechanism that converts the rotation of a steering wheel shaft according to the rotation of a steering wheel into sliding of a rack shaft via a pinion connected thereto, and performs steering by this sliding, With the rack shaft as a support shaft, a piston is fixedly mounted in the middle of the rack shaft, and a power cylinder is formed by being inserted into a cylinder chamber formed in a part of a housing surrounding the rack shaft, and a steering assist force applied to the piston is provided. Are designed to act directly on the rack shaft to assist steering.
[0005]
On the other hand, a ball screw shaft is continuously provided on the tip side of the steering wheel shaft connected to the steering wheel, and the rotation of the steering wheel is converted into sliding of a ball nut screwed into the ball screw shaft, and this sliding is formed outside the ball nut. In the ball screw type steering mechanism that converts the rotation of the sector gear to the rotation of the sector gear through the rack teeth and transmits the rotation to a link mechanism for steering to perform steering, the ball screw shaft is used as a support shaft, In addition, a power cylinder is configured using the ball nuts as pistons and a housing of the ball nuts as a cylinder chamber, and a steering assist force applied to the piston is converted into a steering force via the sector gear and the link mechanism. It is done so.
[0006]
In the power cylinder of the power steering apparatus configured as described above, in order to obtain a desired steering assist force, it is important to maintain a good liquid-tight state between the oil chambers on both sides of the piston. In particular, there is a sliding portion between the outer periphery of the piston and the inner periphery of the cylinder chamber. Further, in a power cylinder of a ball screw type power steering device, in addition to the sliding portion, a ball screw shaft is provided. There are sliding rotation parts that rotate relative to each other with sliding between the outer circumference and the piston, and in these parts, it is necessary to maintain liquid tightness on both sides without hindering each movement. A sealing means as shown in FIG. 5 is widely used.
[0007]
FIG. 5 shows the configuration of the sealing means between the outer periphery of the piston 1 and the inner periphery of the cylinder chamber 2. In the conventional sealing means, a seal groove 1a having an appropriate width is formed on the outer peripheral surface of the piston 1, a backup ring 1b is wound inside the seal groove 1a, and a seal ring 1c is wound around the outside thereof. to the inner peripheral surface of the cylinder chamber 2 to be sealing surfaces are brought into close contact with the outer peripheral surface of the seal ring 1c, has a configuration to maintain the liquid-tightness between the oil on both sides of the piston 1 chamber S _1, S _2.
[0008]
The backup ring 1b is an O-ring having a circular cross section made of a material having a high elasticity such as rubber. As shown in the figure, the backup ring 1b is deformed into an oval shape between the bottom surface of the seal groove 1a and the seal ring 1c. Has the effect of pressing the seal ring 1c outwardly by the elastic restoring force of. The seal ring 1c is a ring having a rectangular cross section having substantially the same width as the seal groove 1a. One surface of the seal groove 1a side is pressed by the backup ring 1b to expand the diameter, and the other surface is formed on the inner peripheral surface of the cylinder chamber 2. It is in a pressed state.
[0009]
Thus, the sliding of the piston 1 due to the pressure difference between the oil chambers S ₁ and S ₂ on both sides occurs with the sliding contact of the seal ring 1 c with the inner peripheral surface of the cylinder chamber 2, and the two oil chambers S ₁ , liquid tight S ₂ is maintained by the adhesion of the seal ring 1c of the inner circumferential surface of the cylinder chamber 2. The seal ring 1c is formed of a material having a low frictional resistance and excellent abrasion resistance, such as a fluororesin (Teflon), in order to maintain a close contact state without hindering the sliding of the piston 1.
[0010]
[Problems to be solved by the invention]
However, in the conventional power cylinder provided with the sealing means as described above, during the operation of the piston 1, particularly when the internal pressures of the oil chambers S ₁ and S ₂ on both sides are reversed and the sliding direction of the piston 1 is reversed. In addition, there is a possibility that the liquid tightness at the sliding contact portion of the seal ring 1c is temporarily broken, and a phenomenon that the hydraulic oil blows out from the high pressure side to the low pressure side, a so-called blow-through phenomenon, may occur. When the blow-by phenomenon occurs, a response delay occurs when the piston 1 is reversed, and when the steering direction is suddenly changed, a sufficient steering assist force may not be obtained in the initial stage of the change.
[0011]
FIG. 6 is an explanatory diagram of a generation mechanism of the blow-by phenomenon. The piston 1 in FIG. 6 (a), by the hydraulic action directed from one oil chamber S ₁ to the other oil chamber S _2, are slid in the direction indicated by outline arrow in the figure, this time sealing ring. 1c, the hydraulic action of the oil chamber S ₁ side, inside of the sealing groove 1a, in the position by the oil chamber S ₂ side within the both fitting gap.
[0012]
Reversal of pressure occurs in this state, when the internal pressure of the oil chamber S ₂ is higher, as indicated by outline arrow in FIG. 6 (b), the with the sliding direction of the piston 1 is reversed, the above-mentioned A pressing force in the same direction is also applied to the seal ring 1c in the state. However this time, the opposite side of the seal ring 1c (oil chamber S ₁ side), sealed from the gap is formed between the side walls of the sealing groove 1a, the sealing ring 1c by the action of the pressing force 6 (b), and the other surface of the seal ring 1c comes into line contact with the inner peripheral surface of the cylinder chamber 2, resulting in a liquid-tight state. It becomes difficult to maintain and a blow-by phenomenon occurs.
[0013]
This blow-through phenomenon is configured to maintain the liquid-tightness of the sliding rotation part between the outer periphery of the ball screw shaft and the piston in the power cylinder of the ball screw type power steering device configured as described above. The same applies to the sealing means.
[0014]
The present invention has been made in view of such circumstances, and eliminates the phenomenon of hydraulic oil blow-through due to reversal of the sliding direction of the piston, and obtains sufficient steering assist force with high responsiveness when changing the steering direction. It is an object of the present invention to provide a power cylinder of a power steering device capable of performing the following.
[0015]
[Means for Solving the Problems]
In the power cylinder of the power steering device according to the present invention, the piston supported by the support shaft is slidably fitted in the axial direction inside the cylinder chamber, and both sides of the piston are liquid-tightly sealed by sealing means. A pair of oil chambers are provided for selectively supplying and discharging pressure oil according to the operation of the steering wheel to each of these oil chambers, and a steering mechanism for sliding the piston caused by the action of the pressure oil. In a power cylinder of a power steering apparatus configured to assist steering by transmitting to a seal groove , the seal means includes a seal groove provided around the piston with an appropriate width, and a seal groove provided on an inner side of the seal groove. comprising a wound backup ring, Yes by winding superposed on said backup ring, the inner circumferential surface of the cylinder chamber, or sliding contact with the seal ring to the inner and outer peripheral surfaces of the support shaft, wherein The backup ring has a circular cross section That juxtaposed a pair of ring portions has a cross-sectional shape comprising, in the each of the ring portion is elastic contact at two positions in the width direction and the seal ring and the bottom surface of the seal groove, the seal ring It is characterized by being configured to be pressed against the sliding contact surface.
[0016]
[Action]
In the present invention, the inner peripheral surface of the cylinder chamber, or a seal ring that slides on the inner peripheral surface and the outer peripheral surface of the support shaft to maintain a liquid-tight state between the oil chambers on both sides, wound on the inner side, is pressed against the more sliding surfaces backup ring formed by juxtaposed a pair of ring portions having a circular cross-section. This pressing is the width direction of the seal groove, ie upon two of the sliding direction of the piston, made by the action of the bottom surface and the seal ring and elastically contact the ring portion of the seal groove, the sliding direction of the piston At the time of conversion, the collapse of the seal ring accompanying this is effectively suppressed by elastically deforming the ring portion elastically contacting with the bottom of the seal groove on the downstream side in the sliding direction, and the blow-through phenomenon caused by this collapse To prevent outbreaks.
[0017]
【Example】
Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments. FIG. 1 is a side sectional view showing an application example of a power cylinder of a power steering apparatus according to the present invention to a ball screw type steering apparatus, and FIG. 2 is an enlarged sectional view of a main part thereof.
[0018]
Figure H ₁ is a gear housing, in the interior of the gear housing H _1, the cylinder chamber 2 has an inner peripheral surface of the circular finished with high accuracy is formed, also the middle of the cylinder chamber 2 The gear chamber 20 is continuously provided so as to face the inside. A ball screw shaft 3 is rotatably supported on the axial center of the cylinder chamber 2, and a cross shaft 4 is supported on the gear chamber 20 so as to be substantially orthogonal to the ball screw shaft 3. The projecting end of the cross shaft 4 to the outside of the gear chamber 20 is connected to a steering mechanism via a link mechanism (not shown) so as to perform steering according to the rotation.
[0019]
A piston 1 is inserted into the cylinder chamber 2 so as to be slidable in the axial direction. As shown in the figure, the piston 1 is a cylindrical member formed by connecting large-diameter portions 10 and 11 at both ends to be fitted to the inner peripheral surface of the cylinder chamber 2 by an intermediate portion 12 having a smaller diameter than these. Inside the ball screw shaft 3, a nut portion 13 screwed to the ball screw shaft 3 via a large number of balls 30, 30,... Is formed over an appropriate length to form a ball screw mechanism. That is, the piston 1 is supported by a ball screw shaft 3 as a support shaft, and is slidably fitted in the cylinder chamber 2 in the axial direction.
[0020]
The cylinder chamber 2 has openings on both sides. One opening is liquid-tightly closed by a lid member 21, and a part of the valve housing H < _b > ₂ coaxially fits into the other opening. are wearing, the ball screw shaft 3, a ball bearing 31 held by the lid member 21 is supported by a ball bearing 32 held in the valve housing H _2.
[0021]
One large-diameter portion 11 of the piston 1 has a notch in a part of the peripheral surface, and the outside of the intermediate portion 12 including the notch portion has rack teeth 14 over an appropriate length range. The rack teeth 14 mesh with a sector gear 40 coaxially fitted to the cross shaft 4. Thus, when the ball screw shaft 3 rotates and the piston 1 slides by screwing with respect thereto, the sliding is converted into rotation of the cross shaft 4 via the sector gear 40 meshing with the rack teeth 14. This rotation is applied to the steering mechanism via the link mechanism to perform steering.
[0022]
The other large diameter portion 10 of the piston 1 is fitted into the cylinder chamber 2 over the entire circumference, and the outer circumference of the large diameter portion 10 is in sliding contact with the inner peripheral surface of the cylinder chamber 2. Are formed in a liquid-tight manner on both sides. Further, a seal ring 6a is fitted and fixed to an opening edge of the inner periphery of the piston 1 on the side of the large diameter portion 10, and the inside of the seal ring 6a is slidably in contact with the outer peripheral surface of the ball screw shaft 3. Sealing means 6 for sealing both sides of the sliding contact portion in a liquid-tight manner is provided.
[0023]
That is, the inside of the cylinder chamber 2, said outer seal means 5 of the large diameter portion 10, fluid-tightly sealed by the sealing means 6 provided on the inside of the sealing ring 6a, the oil chamber S ₁ and the oil chamber S ₂ and is divided into, these oil chamber S _1, S _2, by later-described operation of the hydraulic control valve 7, which is configured in the interior of the valve housing H _2, the operation of the steering wheel (not shown) (steering wheel) The corresponding pressure oil is supplied. This feed pressure oil is applied to both sides of the piston 1, and an axial pressing force (steering assist force) corresponding to the pressure difference between the two surfaces acts on the piston 1. As described above, the rotation is converted into the rotation of the cross shaft 4 via the sector gear 40 to assist the steering.
[0024]
The hydraulic control valve 7 that supplies and discharges pressure oil to and from the oil chambers S ₁ and S ₂ utilizes torsion generated in a shaft connected to the steering wheel by operating the steering wheel for steering. It is configured. That is, the end portion of the ball screw shaft 3 projecting into the valve housing H ₂ is coaxially butted to the end of the input shaft 34 inserted from the other side, they are internal to the hollow portion of the ball screw shaft 3 It is connected coaxially by the inserted torsion bar 35. The inside of the valve housing H _2, valve body 7a of the rotatable cylindrical coaxially is supported, the valve body 7a is are brought into engagement to projecting end of the ball screw shaft 3. The input shaft 34 is inserted into the valve body 7a for a predetermined length, and a valve spool 7b is integrally formed on the outer periphery of the insertion portion, and constitutes the hydraulic control valve 7 together with the valve body 7a.
[0025]
Hydraulic control valve 7 configured as described above, the hydraulic pump P via a pump port 70 which opens to the outside of the valve housing H _2, are also respectively connected to the oil tank T through the tank port 71, The valve the interior of the ball bearing 32 for supporting the ball screw shaft 3 at the housing H ₂ side as a passage, in one of the oil chambers S ₁ of the inner cylinder chamber 2, further other oil chamber S ₂ via the connecting pipe (not shown) The hydraulic oil supplied from the hydraulic pump P via the pump port 70 is selectively supplied to _{one of} the oil chambers S ₁ and S ₂ according to the relative angular displacement between the valve body 7a and the valve spool 7b. Sent to
[0026]
The other end of the input shaft 34 projecting to the other side of the valve housing H ₂ is Yes coupled to a steering wheel, not shown, to the input shaft 34, joined by a steering torque in accordance with the operation of the steering wheel for steering, At this time, the torsion bar 35 connecting the input shaft 34 and the ball screw shaft 3 is twisted. Therefore, between the valve body 7a engaged with the ball screw shaft 3 and the valve spool 7b integrally formed on the outer periphery of the input shaft 34, a relative position corresponding to the magnitude in the direction of the steering torque. The angular displacement occurs, and the pressure oil supplied from the hydraulic pump P is selectively supplied to _{one of} the oil chambers S ₁ and S ₂ in accordance with the direction of the relative angular displacement. And the steering assist force is obtained as described above. At this time, the hydraulic oil in the other oil chambers S ₁ and S ₂ is pushed out by the sliding of the piston 1 and returns to the hydraulic control valve 7, is distributed to the oil tank T side, recirculates, and is reused. You.
[0027]
In the above operation, the sliding of the piston 1 due to the action of the supply pressure oil to the oil chambers S ₁ and S ₂ is caused by the sliding contact with the inner peripheral surface of the cylinder chamber 2 and the outer peripheral surface of the ball screw shaft 3. It occurs with sliding contact. A feature of the power cylinder according to the present invention lies in the configuration of the sealing means 5 and 6 interposed in these sliding contact portions, respectively, in order to maintain the liquid tightness between the oil chambers S ₁ and S ₂ .
[0028]
In order to maintain the liquid tightness between the inner circumference of the cylinder chamber 2 and the outer periphery of the piston 1 (large diameter portion 10), a sealing means 5 is provided on the outer circumference of the large diameter portion 10 as shown in FIG. A seal groove 50 is formed with a width of, and a backup ring 51 is wound on the inner side of the seal groove 50, and a seal ring 52 is wound on the outer side of the backup ring 51 so as to form a sealing surface. The configuration is such that the outer peripheral surface of the seal ring 52 is pressed against the inner peripheral surface of the chamber 2 by the elasticity of the backup ring 51.
[0029]
The seal ring 52 is a ring having a rectangular cross section having substantially the same width as that of the seal groove 50. The elastic ring of the backup ring 51 presses the entire width substantially evenly against the inner peripheral surface of the cylinder chamber 2 so that the oil chambers on both sides are formed. It functions to maintain good liquid tightness between S ₁ and S ₂ . The seal ring 52 is made of a resin such as a fluororesin (Teflon) having a low frictional resistance and excellent abrasion resistance. The seal ring 52 follows the sliding of the piston 1 generated while maintaining the pressed state without resistance, and is in a liquid-tight state. Is maintained.
[0030]
On the other hand, the backup ring 51 is a ring made of an elastic material such as rubber in order to apply a sufficient pressing force to the seal ring 52, and as shown in FIG. It has a cross-sectional shape in which a pair of ring portions having a cross section are connected by a thin connecting portion. The seal ring 52 is provided so as to straddle both of the pair of ring portions, and the pressing by the backup ring 51 is performed at two places in the width direction by both ring portions. .
[0031]
The sealing means 6 configured to maintain liquid tightness with the outer peripheral surface of the ball screw shaft 3 is formed on the inner surface of the seal ring 6 a facing the outer peripheral surface of the ball screw shaft 3, similarly to the sealing means 5. A seal groove 60, and a backup ring 61 and a seal ring 62 wound around the seal groove 60 inward and outward, respectively. The entire surface is pressed against the outer peripheral surface of the shaft 3 to perform a sealing action.
[0032]
The backup ring 61 of the sealing means 6 also has a cross-sectional shape in which a pair of ring portions having a circular cross section arranged in the width direction are connected by a thin connecting portion, as shown in the drawing, and the pressure of the seal ring 62 is reduced. This is performed at two places in the width direction by the two ring portions.
[0033]
In the sealing means 5 and 6 configured as described above, the internal pressures of the oil chambers S ₁ and S ₂ on both sides are reversed during the operation of the piston 1 and the high pressure side generated when the sliding direction of the piston 1 is reversed. Blow-through of hydraulic oil to the low pressure side can be effectively prevented. FIG. 3 is an explanatory diagram of the operation of preventing the blow-by phenomenon in the sealing means 5.
[0034]
3 (a) is, for example, by the hydraulic action of the oil chamber S ₁ side shows a state in which the piston 1 is slidably, sealing ring 52 at this time, the seal groove 50 by the action of the hydraulic pressed against the oil chamber S ₂ side inside, in a state where a gap occurs between the side edges of the opposite side (oil chamber S ₁ side).
[0035]
FIG. 3B shows a state in which the internal pressures of the oil chambers S ₁ and S ₂ are reversed in the above state, and the pressure on the oil chamber S ₂ side is increased. Sliding in the opposite direction starts due to the reversal of the working pressure on both surfaces of No. 10, and a pressing force from the oil chamber S < _b > ₂ side is also applied to the seal ring 52.
[0036]
At this time, the opposite side of the seal groove 50 (the oil chamber S ₁ side), as described above, since the gap is formed between the seal ring 52, seal ring 52 upon the action of the pressing force, FIG. As shown by the broken line in FIG. However the seal ring 52, inside the seal groove 50, is in a pair state, supported the two places in the width direction by the ring portion of the backup ring 51 which forms the above-mentioned shape, the ring portion of the oil chamber S ₁ side The elasticity serves to prevent the above-mentioned fall.
[0037]
Therefore, the seal ring 52, without taking the tilt attitude shown by the dashed line, is pushed to the inner circumferential surface while the reverse side keeping the close contact to the cylinder chamber 2 (oil chamber S ₁ side), 3 ( b) as shown by the solid line in, a state of being pressed to the oil chamber S ₁ side in the interior of the seal groove 50, during which the low pressure side from the high pressure side, i.e., blow from the oil chamber S ₂ to the oil chamber S ₁ is Almost no occurrence.
[0038]
Such an operation occurs in the same manner in the sealing means 6 which performs a sealing action between the piston 1 and the outer peripheral surface of the ball screw shaft 3 serving as a support shaft thereof. As described above, in the power cylinder according to the present invention, it is possible to effectively prevent the hydraulic oil from flowing from the high pressure side to the low pressure side during the reversal operation of the piston 1 due to the reverse rotation of the internal pressures of the oil chambers S ₁ and S _2. . Accordingly, when the steering direction is suddenly changed, the reversal of the piston 1 corresponding to this suddenly occurs, and a sufficient steering assist force is obtained from the initial stage of the change.
[0039]
FIG. 4 is an enlarged sectional view of a main part showing another embodiment of the present invention. In the present embodiment, the sealing means 5 formed on the outer periphery of the large diameter portion 10 winds two O-rings 53, 53 having a circular cross-section side by side in the width direction inside the sealing groove 50, and winds these O-rings. The configuration is such that the seal ring 52 is pressed outward at two places in the width direction by 53 and 53 and pressed against the inner peripheral surface of the cylinder chamber 2 serving as a seal surface.
[0040]
Similarly, the sealing means 6 formed on the inner periphery of the seal ring 6a inside the large-diameter portion 10 also has two O-rings 63, 63 arranged side by side in the width direction and wound around the inside of the seal groove 60. The configuration is such that the seal ring 62 is pressed inward and pressed against the outer peripheral surface of the ball screw shaft 3 serving as a seal surface. In this configuration, similarly to the configuration shown in FIG. 2, the occurrence of the blow-by phenomenon can be prevented.
[0042]
Further, in the present embodiment, an example of application to a ball screw type power steering device has been described, but the present invention is also applied to other types of power steering device such as a rack and pinion type power steering device. It is needless to say that a similar effect can be obtained.
[0043]
【The invention's effect】
As described in detail above, in the power cylinder of the power steering apparatus according to the present invention, the power cylinder is wound around the seal groove formed in the piston, and the inner peripheral surface of the cylinder chamber, or the inner peripheral surface and the outer peripheral surface of the support shaft. A seal ring is formed by winding a backup ring having a pair of ring portions having a circular cross section on the inner rear side of the seal ring that slides on and maintains a liquid-tight state between the oil chambers on both sides. The seal ring is pressed against the sliding contact surface by the action of the ring portions which resiliently contact the bottom surfaces of the seal ring and the seal groove at two positions separated in the width direction of the seal groove, that is, in the sliding direction of the piston . since was, inverted working pressure from both sides of the oil chamber, when the sliding direction of the piston is converted, the seal ring inclination of is suppressed by the elasticity of the ring portion elastically contacts the sliding direction downstream side due to this, High due to this fall Can effectively prevent the occurrence of a blow-by phenomenon from the side to the low-pressure side, and it is possible to obtain sufficient steering assist force with high responsiveness when changing the steering direction, leaving room for sudden steering operation The present invention has excellent effects, such as being able to follow with the user and obtaining a good steering feeling.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a power cylinder of a power steering device according to the present invention.
FIG. 2 is an enlarged sectional view of a main part of FIG.
FIG. 3 is an explanatory diagram of an operation for preventing a blow-by phenomenon.
FIG. 4 is an enlarged sectional view of a main part showing another embodiment of the power cylinder of the power steering apparatus according to the present invention.
FIG. 5 is an enlarged sectional view of a main part of a power cylinder of a conventional power steering device.
FIG. 6 is an explanatory diagram of a generation mechanism of a blow-by phenomenon.
[Explanation of symbols]
Reference Signs List 1 piston 2 cylinder chamber 3 ball screw shaft 5 sealing means 6 sealing means 7 hydraulic control valve 7a valve body 7b valve spool 50 seal groove 51 backup ring 52 seal ring 53 O ring 60 seal groove 61 backup ring 62 seal ring 63 O ring H ₁ gear housing H ₂ valve housing S ₁ oil chamber S ₂ oil chamber

Claims (1)

A piston supported by a support shaft is slidably fitted in the axial direction inside the cylinder chamber, and a pair of oil chambers which are liquid-tightly sealed by sealing means are provided on both sides of the piston. A power steering system that selectively supplies and discharges pressure oil according to the operation of the steering wheel to each of the oil chambers, and transmits the sliding of the piston generated by the action of the pressure oil to a steering mechanism to assist steering. In the power cylinder of the device, the sealing means includes a seal groove provided around the piston with an appropriate width, a backup ring wound inside the seal groove, and a backup ring. And a seal ring slidably contacting the inner peripheral surface of the cylinder chamber, or the inner peripheral surface and the outer peripheral surface of the spindle.The backup ring includes a pair of ring portions having a circular cross section. Has a cross-sectional shape that is juxtaposed , Power steering, characterized in that said the respective ring portion is elastic contact at two positions in the width direction and the seal ring and the bottom surface of the seal groove, it is constituted to press the sealing ring on the sliding surface Power cylinder of the picking device.

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