The present invention relates to a hydraulic actuator preferably used for controlling braking fluid of an anti-lock braking system (hereinafter, abbreviated by ABS) installed in an automotive vehicle.
In the anti-lock braking system, the hydraulic actuator is operated to precisely and promptly increase and decrease the hydraulic pressure of each wheel cylinder in accordance with rotational conditions of each wheel to prevent the wheel from locking during the braking operation.
An object of the present invention is to secure a sufficient damper capacity for an ABS actuator to reduce the noise caused during an ABS operation.
To accomplish the above and other related objects, the present invention provides a first ABS actuator comprising a housing having a first predetermined surface where a bore is formed. A damper, defined in the bore, has an axis extending in a depth direction of the bore. A cup-shaped diaphragm, disposed in the bore, divides an inside space of the bore into a first chamber and a second chamber. The cup-shaped diaphragm has an opening at one axial end and a bottom at an opposed axial end. The opening of the cup-shaped diaphragm becomes a leading side when the cup-shaped diaphragm is inserted into the bore. A plug-like wall member closes an opening of the bore. A damper chamber is constituted by the first chamber and includes an inside space of the cup-shaped diaphragm. The housing has a second predetermined surface where a control valve is installed. The second predetermined surface is substantially perpendicular to the first predetermined surface. The housing has a third predetermined surface where a first port is formed. The third predetermined surface is substantially perpendicular to the first predetermined surface and is opposed to the second predetermined surface. And, a main conduit line connects the first port to the control valve.
In this first ABS actuator, the plug-like wall member has a protruding portion for pushing the bottom of the cup-shaped diaphragm. The protruding portion is spaced from a cylindrical wall of the bore. An annular space is formed between the protruding portion and the cylindrical wall of the bore. The annular space constitutes the second chamber. And, a first conduit line has its inlet opened to the annular space provided around the protruding portion and extends from the annular space as part of the main conduit line.
With this arrangement, the damper diameter can be increased to a level equivalent to the diameter of the bore. This realizes a large damper capacity. Thus, it becomes possible to reduce the noise caused during the ABS operation.
Furthermore, the present invention provides a second ABS actuator comprising a housing having a first predetermined surface where a bore is formed. A damper, defined in the bore, has an axis extending in a depth direction of the bore. A cup-shaped diaphragm, disposed in the bore, divides an inside space of the bore into a first chamber and a second chamber. The cup-shaped diaphragm has an opening at one axial end and a bottom at an opposed axial end. The opening of the cup-shaped diaphragm becomes a leading side when the cup-shaped diaphragm is inserted into the bore. A plug-like wall member closes an opening of the bore. A damper chamber is constituted by the first chamber and includes an inside space of the cup-shaped diaphragm. The housing has a second predetermined surface where a control valve is installed. The second predetermined surface is substantially perpendicular to the first predetermined surface. The housing has a third predetermined surface where a first port is formed. The third predetermined surface is substantially perpendicular to the first predetermined surface and is opposed to the second predetermined surface. A second port is formed on the first predetermined surface where the damper is installed. And, a main conduit line is formed in the housing so as to communicate with the second chamber. The main conduit line connects the first port to the second port via the control valve.
In this second ABS actuator, the first port is offset from the control valve in an axial direction of the damper. The control valve is located far from the first predetermined surface compared with the first port. And, the main conduit line connects the second chamber to the control valve via a first conduit line extending obliquely with respect to the axis of the damper from a cylindrical wall of the bore.
In this manner, providing the first conduit line extending obliquely with respect to the axis of the damper from the cylindrical wall of the bore makes it possible to connect the second chamber to the control valve under a condition where the first port is offset from the control valve in the axial direction of the damper and the control valve is located far from the first predetermined surface compared with the first port. Accordingly, in addition to the above-described effect of the first ABS actuator, it becomes possible to downsize the housing in the axial direction of the damper.
In the above-described second ABS actuator, It is preferable that the plug-like wall member has a protruding portion for pushing the bottom of the cup-shaped diaphragm. And, the protruding portion is spaced from the cylindrical wall of the bore. An annular space is formed between the protruding portion and the cylindrical wall of the bore constitutes the second chamber. The first conduit line has its inlet opened to the annular space provided around the protruding portion. With this arrangement, it becomes possible to fix the position of the cup-shaped diaphragm by the protruding portion.
According to a preferred embodiment of the present invention, the protruding portion of the plug-like wall member is a circular protruding portion formed at an inner end of the plug-like wall member. A diameter of the circular protruding portion is smaller than that of a main body of the plug-like wall member. The circular protruding portion presses the bottom of the cup-shaped diaphragm when the plug-like wall member is inserted into the bore, so that an insertion amount of the circular protruding portion substantially determines an axial position of the cup-shaped diaphragm in the bore.
Preferably, the cylindrical protruding portion is spaced from the cylindrical wall of the bore when the plug-like wall member is inserted in the bore so as to close the opening of the bore, so that the second chamber surrounds the cylindrical protruding portion of the plug-like wall member.
According to the preferred embodiment of the present invention, the main conduit line further comprises a second conduit line which extends from the control valve in a direction substantially perpendicular to the second predetermined surface and is connected to the first conduit line.
The pressurizing control valve is offset from the annular space provided around the protruding portion of the plug-like wall member in a direction normal to the first predetermined surface. The first conduit line extends straight and obliquely from the annular space and is connected to the second conduit line.
For example, two control valves are installed adjacent to each other on the second predetermined surface. One of the two control valves is directly connected to the first conduit line via the second conduit line. And, the other of the two control valves is connected to the first conduit line via the second conduit line and a third conduit line connecting the two control valves.
In this manner, when two control valves are disposed adjacent to each other, it is desirable that one of two control valves is directly connected to the first conduit line via the second conduit line. The other control valve can be connected to the first conduit line via the second and third conduit lines.
Furthermore, it is preferable that a through-hole is opened on the bottom of the cup-shaped diaphragm. The through-hole serves as an orifice connecting the first chamber to the second chamber.
In this case, it is further preferable that a region where the through-hole is opened is thin in thickness compared with the remaining portion of the bottom of the cup-shaped diaphragm. For example, a recessed region is formed on the bottom so as to surround the through-hole. The recessed region has a sufficient depth so that a burr formed around the through-hole remains in a retracted position with respect to a surface of the bottom.
Although the burr is inherently produced along an annular periphery of a through-hole during a formation of the through-hole, the above-described arrangement prevents the burr from protruding from the surface of the bottom. Thus, it becomes possible to prevent the burr from peeling off the cup-shaped diaphragm.
Furthermore, it is preferable that the cup-shaped diaphragm has a press-fitting portion partly formed on a cylindrical wall thereof. The press-fitting portion has an enlarged diameter larger than the diameter of other portion of the cup-shaped diaphragm. And, the cup-shaped diaphragm is firmly fixed in the bore by the press-fitting portion.
Preferably, the press-fitting portion protrudes radially outward from a surface of the cylindrical wall of the cup-shaped diaphragm. The press-fitting portion extends in a circumferential direction of the cylindrical wall of the cup-shaped diaphragm.
In this manner, forming the press-fitting portion on the cylindrical wall of the cup-shaped diaphragm makes it possible to firmly fix the cup-shaped diaphragm in the bore.
Moreover, it is preferable that an opening periphery of the cup-shaped diaphragm is squeezed in diameter compared with other portion of the cup-shaped diaphragm.
Preferably, the opening periphery of the cup-shaped diaphragm is curled radially inward so as to have a smaller diameter compared with a cylindrical wall of the cup-shaped diaphragm, so that the cup-shaped diaphragm can be easily inserted into the cylindrical bore from the opening periphery of the cup-shaped diaphragm.
In this manner, squeezing the diameter of the opening periphery of the cup-shaped diaphragm makes it possible to easily insert the cup-shaped diaphragm in the bore.
Preferably, the cup-shaped diaphragm has a diameter substantially identical with that of the bore. The cup-shaped diaphragm has an axis identical with that of the bore.