JPS5925905B2 - piston cup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston cup for an automobile.

Automobiles are equipped with various hydraulic systems.

That is, devices are often used in which a piston cup is inserted, a cylinder chamber is formed by the piston, a cylinder, and the piston cup, and the relative movement between the piston and cylinder presses oil to generate hydraulic pressure.

In particular, with respect to piston cups (hereinafter simply referred to as brake cups) in brake devices, which are considered most important from the viewpoint of automobile safety, various brake cups have been developed that improve the sealing effect from the viewpoint of safety.

As a result, today a brake cup with a satisfactory sealing effect has been developed, but users' demands have started to become more concerned with the feeling when stepping on the brake pedal.

That is, there has been a demand for a brake cup that allows the brake pedal to be depressed smoothly without any resistance when braking an automobile, and that enables the automobile to be reliably braked with as little pedal effort as possible.

Conventionally, brake cups called S t A, E j' Eve, and Opel Quip, as well as brake cups modified from these brake cups, have been widely used.According to experiments conducted by the present inventors, these brake cups have a good sealing effect. Although the oil film formed on the sliding surface is sometimes broken, the cup comes into direct contact with the metal wall of the cylinder etc., increasing the sliding resistance of the brake cup and masking the brake cup. There was a drawback that a large piston actuation force, that is, a large brake pedal depression force was required to slide the mask cylinder within the cylinder and generate a constant hydraulic pressure within the mask cylinder (the cylinder pressure increase efficiency was poor).

Also, sometimes when the brake cup slides inside the cylinder, vibrations similar to stick-slip vibrations occur.
In some cases, stable piston operation, that is, stable braking, was not ensured.

In order to eliminate the drawbacks of these conventional brake cups and other automotive hydraulic cylinders, the inventors of the present invention have conducted numerous experiments and theoretical analyzes to reduce the sliding resistance against the cylinder or piston, etc. We have invented a piston cup that increases the efficiency of increasing the hydraulic pressure inside the cylinder, enables stable piston operation, and improves the lifespan of the piston.

These piston cups by the present inventors are disclosed in Japanese Patent Application No. 52-85385 dated July 15, 1972 (Japanese Unexamined Patent Publication No. 54
-20261 Publication) and Utility Application No. 1982-95 dated the same date.
011 (Utility Model Application Publication No. 54-21785), the above-mentioned Japanese Patent Application No. 52-85385 is basically shown in FIG. A broken line groove 15 shown in FIG. 2 is formed by scraping the outer circumferential wall of the outer lip portion 11 on the seal circumferential wall surface 14 of the conventional SAE type piston cup 10 consisting of the piston cup 10, and a small amount of oil is poured into the groove. By holding and forming an appropriate oil film on the cylinder, the sliding resistance is reduced as shown in the third figure.

The above Japanese Patent Application No. 52-85385 is further incorporated by U.S. Patent Application No. 52-95.
As is also a feature of No. 011, by cutting the outer peripheral wall of the leading portion of the outer lip portion 11, the angle θ with respect to the cylinder axis in the free state of the leading portion is adjusted so that the remaining portion of the peripheral wall surface of the outer lip portion 11 is aligned with the cylinder axis. By making the angle smaller than the angle between the leading part and the cylinder as shown in the fourth figure, the leading part forms a wedge-shaped gap with respect to the cylinder, forming a wedge-shaped oil film, which improves fluid lubrication and protects the sliding surface. This promoted the formation of an oil film, thereby reducing the sliding resistance as shown in Figure 5.

The fact that the invention and device of the above-mentioned earlier application by the present inventors is extremely effective compared to the conventional piston cup is that the above-mentioned Japanese Patent Application No. 1983-1997 discloses detailed theoretical analysis and experimental results. This is clear from No. 85385 and Utility Model Application No. 52-95011.

This type of piston cup is disposed in a hydraulic brake device as shown in FIG. 6, and the internal structure of the brake device, particularly the master cylinder, will be briefly described below.

The cylinder CY generally includes a first piston P and a second piston P2.

The first piston P has a secondary cup SC and a primary cup PC1, and the second piston P2 has a primary cup PC2 and a floating cup FC, FC2.
are assembled respectively.

Next, the function of each cup within the cylinder CY will be explained.

First, when you step on the brake pedal BP, the bush rod PR
pushes the first piston P, and the primary cup PC assembled to the first piston P pushes the reservoir tank RT.
The compensation hole CH, which leads to the rear side pressure chamber RC, is closed, and internal pressure is generated in the rear pressure chamber RC.

Then, the second piston P2 moves due to the internal pressure of the pressure chamber RC, and the primary cup PC2 similarly moves to the reservoir tank R.
Close the compensation hole CH2 leading to T2 and close the front side pressure chamber FC.
Internal pressure is also generated.

The generated internal pressure is transferred via piping (not shown) to
The braking force is transmitted to the rear wheel cylinder and front wheel cylinder.

Secondary cup SC assembled to first piston P1
The primary cups PC, PC2 assembled to the first piston P and the second piston P2 generate internal pressure by self-sealing action.

Furthermore, the floating cups FC, FC2 have a role of separating the rear side pressure chamber RC and the front side liquid chamber FOC.

This is a type in which the contact width of the seal portion changes depending on the internal pressure of the cup or the sealing cap described above.

Therefore, in the piston cup configured and arranged as described above, the shape of the sliding surface of the piston cup is changed by frictional force, especially when the material is easily deformed in some parts, and
The piston cup is deformed by swelling or thermal deformation during braking, etc., and the fluid lubrication effect is likely to be lost.Furthermore, when the piston cup starts operating after the oil film between the piston cup and the cylinder has broken, the starting friction may A force in a direction opposite to the moving direction of the cup acts on the cup sliding surface, causing deformation of the sliding surface, and eventually the frictional force increases and the desired fluid lubrication effect may not be achieved.

Furthermore, the desired angle θ with respect to the cylinder axis or piston axis in the free state of the leading portion of the outer lip portion is set within a relatively narrow range, and therefore, there is a possibility that a sufficient fluid wedge effect cannot be expected due to manufacturing errors, etc. .

Therefore, an object of the present invention is to provide a new piston cup that eliminates the above-mentioned disadvantages.

Therefore, in the piston cup according to the present invention, by shaving the peripheral wall of the leading portion of the peripheral wall surface forming the sliding surface of the piston cup, the angle of this leading portion with respect to the cylinder axis can be adjusted so that the remaining portion of the peripheral wall surface with respect to the cylinder axis. When inserted between the cylinder and the piston at an angle smaller than the angle formed by the leading part, the leading part forms a wedge-shaped gap with respect to the cylinder or piston, and
In addition, an edge portion is formed by cutting the most tip of the leading portion at an angle toward the axis of the cylinder.

In this way, the most extreme part of the leading part, especially between the edge part and the most extreme part of the cup, is located in the direction of movement of the cup to the operating state and toward the axis of the cylinder, with respect to the inner peripheral surface of the cylinder. Form an inclined surface.

The inclined surface forms a triangular gap with the inner circumferential surface of the cylinder, and retains oil in the triangular gap, and
By guiding and supplying oil into the wedge-shaped gap, an oil film is constantly and reliably formed on the sliding surface, which reduces sliding resistance, enables smooth and stable operation of the piston, and improves braking. This improves the feel of the brakes.

Further, when the cup is operated, the inclined surface generates a fluid suction force between the cup and the cylinder, so that the inclined surface itself has fluid lubrication.

Therefore, even if the fluid wedge effect or fluid lubrication action is reduced or eliminated due to the above-mentioned factors, the fluid lubrication action is increased or restored due to the edge or inclined surface effect resulting from the formation of the edge portion, and therefore the cylinder or piston This ensures a more stable and reliable reduction in sliding resistance.

In this way, the present invention provides a piston cup that increases the efficiency of increasing the hydraulic pressure within the cylinder, enables stable piston operation, and has an improved lifespan.

Another object of the present invention is that the inclined surface acts as a guide surface when the piston cup is assembled into the cylinder and acts as an operating or sliding guide surface when the piston cup is inserted into the compensation hole. The purpose of this is to improve durability, prevent damage such as curling, and improve durability and lifespan.

A further object of the present invention is, in addition to the edge effect described above, to
A predetermined groove is formed on the peripheral wall surface of the piston cup to constantly retain oil in the groove, and an oil film is formed on the cylinder surface in response to the reciprocating movement of the piston, thereby further reducing sliding resistance and ensuring stable piston operation. The objective is to provide a piston cup that makes it possible.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 7, the piston cup 100 according to the present invention is
Outer lip part 101, inner lip part 102 and bottom part 1
It has 03.

One broken line groove 104 is formed on the peripheral wall surface 105, starting from point A, having the bottom at point 0, and ending at the lower point.

This groove is defined by a point H where a perpendicular line drawn from a point E, which is the intersection of the inner wall surface of the outer lip 101 and the bottom portion 103, to the inner wall line DE of the outer lip portion 101 intersects with the peripheral wall surface 105 in FIG. It is on the sealed seal surface AH.

This is based on the fact that when internal pressure is applied, a contact surface pressure (contact pressure greater than the internal pressure) that has a sealing effect is always generated within the seal surface AH.
4, the brake cup is inserted between the cylinder and the piston, and even when the cup slides on the cylinder during brake operation and internal pressure acts on the inner surface of the cup, the broken line groove 104 A portion where surface pressure lower than the internal pressure is reliably applied is formed between the curved line groove 104 and the cylinder, and the liquid in the cylinder is retained in the broken line groove 104, forming and maintaining an appropriate oil film on the cylinder, so that the sealing surface is In order to promote lubricity, sliding resistance is reduced, resulting in stable piston operation, improvement in cylinder pressure raising efficiency, and excellent effects of the tube, which improves the life of the cup.

Note 1. The contact surface pressure that has a sealing effect is the so-called sealing pressure, and the maximum sealing pressure is generated at point A, which is the maximum outer diameter part of the sealing surface (where the interference with the cylinder is maximum).

The leading portion 106 of the outer sealing surface of the outer lip 101 forms an angle θ with respect to a line parallel to the cylinder axis, which is smaller than the remaining portion angle α.

Also, as a matter of course, point A is located on the sealing surface 104 at a portion where the cup outer diameter is larger than the cylinder inner diameter.

When such a cup is inserted between the cylinder and the piston, the leading 106 separates from the cylinder wall at a relatively small angle of inclination.

Therefore, when the cup slides on the cylinder wall soil, the leading part 106 forms a wedge-shaped oil film on the cylinder wall surface to promote a so-called fluid wedge action, which provides a fluid lubrication effect. It acts to form a thin fluid film.

The piston cup according to the present invention is characterized in that the foremost part 107 of the leading part 106 is cut at a desired angle β from eight points, as clearly shown in FIGS.

The angle β is formed in the opposite direction to the angle α with respect to the cylinder axis, that is, from the 8 points toward the cylinder axis, and the 8 points form an edge, so that the piston cup is formed between the cylinder and the piston. When inserted, the tip 107 of the leading portion 106, in other words, the cut surface from the edge S point ensures an inclined surface that is spaced from the cylinder wall as desired.

This prevents the fluid lubrication effect from decreasing or disappearing due to the various factors mentioned above, and prevents the sliding resistance from increasing due to the fluid lubrication effect increased and generated by the edge effect itself.

In this way, the angle β may be formed in the direction opposite to the angle α with respect to the cylinder axis, preferably in the range of 15°≦β≦45°, and the above-mentioned edge effect can be expected. It is clear that any angle is sufficient.

In other words, the desired angles θ and β are set so that the points A and 8 of the piston cup are set at angles γ and δ, and the angles are γ-180°+θ-α.

It will be formed by δ-1806-θ-β.

Therefore, if β is formed in the range of 15°≦β≦45 and θ is formed in the range of -10°≦θ≦15° as described above, δ will be in the range of 120°≦δ≦175°. .

If the angle δ is particularly smaller than 120°, there is the disadvantage that the sealing pressure generated at the eight points increases if the eight points come into contact with the cylinder wall.

Therefore, in order to avoid the above disadvantages and achieve the edge effect, the angle δ needs to be set within the above range, and as a result, the angle β needs to be set to 15°≦β≦45°. .

The above-mentioned cut or inclined surface from the piston cup point S also acts as a guide surface when assembling the piston cup into the cylinder, making it possible to easily assemble the piston cup without damaging it. Even if the tip of the cup gets wedged in the compensation hole, the cut surface acts as an operating or finger guide surface, so that the tip of the cup will not be bent or damaged.

Hereinafter, the effect on the piston cup of the above-mentioned prior application or the conventional piston cup by the present inventors will be explained in detail by showing the results of analysis of the present invention.

In order to ensure the fluid wedge effect and reduce the sliding resistance, it is necessary that the sliding resistance in the absence of pressure be small and that the leading end of the leading portion be spaced apart from the cylinder.

FIG. 9 shows the piston cup according to the present invention in which the angle β of the leading end of the leading portion is cut at approximately 30°, and the piston cup of the prior application by the present inventors in which the leading portion is not cut, when no pressure is applied. Sliding resistance F.

, and the contact angle ψ of the leading portion with respect to the cylinder when the cup is placed in the cylinder, in relation to the above-mentioned angle θ.

From FIG. 9, it can be seen that the piston cup according to the present invention has an angle θ
, the sliding resistance is approximately constant at a sufficiently small value regardless of ψ,
It can be seen that this piston cup is much more effective than the prior art piston cup, in which the sliding resistance increases when the angle ψ decreases as the angle θ increases.

The contact angle ψ of the leading part is O. The angle θ−θ
Even in this case, the piston cup according to the present invention still has a small sliding resistance due to the above-mentioned edge effect.

In FIG. 10, the angle θ is the same as the angle θ.

FIG. 3 is a diagram showing the relationship between the piston stroke and sliding resistance of the piston cup of the present invention when the angle θ is 0° in comparison with a prior art piston cup and a conventional SAE piston cup where the angle θ is 0°.

It can be seen from this figure that the sliding resistance is sufficiently small over the entire range of the piston stroke.

Incidentally, FIG. 11 shows the relationship between the idle or port closing stroke (compensation hole closing stroke) with respect to the angle θ of the piston cup according to the present invention and the piston cup of the prior application.

In the figure, the solid line is the product of the present invention, and the broken line is the product of the prior application.

As is clear from the figure, in the piston cup according to the present invention having a cut surface at an angle β, the idle stroke is approximately constant regardless of the angle θ, and the braking force with respect to the stroke is stable, or the assembly is performed at a later stroke. This has the advantage that no adjustment is required.

As is clear from the above, in the piston cup according to the present invention, by shaving the peripheral wall of the leading portion of the peripheral wall surface that forms the sliding surface of the cup, the angle of this leading portion with respect to the cylinder axis is adjusted so that the remaining portion of the peripheral wall surface is aligned with the cylinder axis. By making the angle smaller than the angle formed by the leading part, it has a fluid wedge effect, and since the tip of the leading part is cut, it exhibits the edge effect mentioned above, completely guaranteeing and increasing the fluid lubrication effect, and reducing sliding resistance. This has the effect of reducing the amount of water, which ultimately increases the efficiency of increasing the hydraulic pressure within the cylinder and enables stable piston operation.

In addition, the piston cup of the present invention has the effect of ensuring fluid lubrication effect due to the edge effect even if a predetermined wedge-shaped gap is not formed between the leading portion and the cylinder due to thermal expansion of the cup, manufacturing error, etc. There is.

In addition, the cut surface acts as a guide surface when assembling the cup into the cylinder, making assembly easier.
In addition, even when the cup is inserted into the compensation hole, the inclined cut surface allows the cup to easily return to the desired cylinder, preventing the tip from curling.
As a result, there is an effect of preventing damage to the cup.

Further, by forming a broken line groove on the circumferential wall surface of the cup, an oil film can be stably and reliably formed and maintained on the sliding surface, and the sliding resistance can be further reduced.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional piston cup, Fig. 2 is a sectional view of a piston cup of a prior application by the present inventors, and Fig. 3 is a piston stroke and sliding resistance of the piston cup according to Figs. 1 and 2 above. FIG. 4 is a sectional view of another piston cup in the earlier application by the present inventors, FIG. 5 is a diagram similar to FIG. 3 relating to the piston cup in FIG. 4, and FIG. 7 is a sectional view of the piston cup according to the present invention, FIG. 8 is an enlarged view of the leading portion of the piston cup, and FIG. 9 is a diagram showing the piston cup of the present invention and the prior application. Fig. 10 shows the relationship between the piston stroke and sliding resistance of the piston cup of the present invention, the prior application, and the conventional piston cup. 11 and 11 are diagrams showing the relationship between the angle of the leading portion of the piston cup of the present invention and the prior application and the port closing stroke. 100: Piston cup, 101: Outer lip portion, 10
2: Inner lip part, 103: Bottom part, 104: Broken line groove, 1
05: Seal peripheral wall surface, 106: Leading part, 107
: Leading first edge, CY edge, P: Piston, P; Piston.

Claims (1)

[Scope of Claims] 1. By cutting the peripheral wall of the leading portion of the peripheral wall surface that forms the sliding surface of the piston cup fitted between the cylinder and the piston, the angle of this leading portion with respect to the cylinder axis can be adjusted by The leading portion forms a wedge-shaped gap with respect to the cylinder or piston when inserted between the cylinder and the piston by forming an angle smaller than the angle that the remaining portion makes with the cylinder axis, and By further cutting the tip of the leading portion, it is inclined toward the axis of the cylinder to form an edge portion, and when the leading portion is inserted between the cylinder and the piston,
A piston cup characterized in that the edge portion holds oil by forming a triangular gap with the sliding surface, and thus guides and supplies the oil to the wedge-shaped gap. 2. The angle of the leading part of the peripheral wall surface that forms the sliding surface of the piston cup inserted between the cylinder and the piston with respect to the cylinder axis is determined by By making the angle smaller than the angle that the leading part makes with the cylinder axis, when the leading part is inserted between the cylinder and the piston, the leading part forms a wedge-shaped gap with respect to the cylinder or piston, and the leading part By further cutting the tip of the part, it is tilted toward the axis of the cylinder to form an edge part, and when it is inserted between the cylinder and the piston, the edge part will be between the sliding surface and A bottom portion of the remaining portion of the peripheral wall surface that is close to the point where maximum sealing pressure is formed, retains oil by forming a triangular gap, and thus guides and supplies the oil to the wedge-shaped gap; A piston cup characterized in that a groove portion having the maximum depth is formed at a closer portion.