Patent Application
20200173391
The present invention relates a fuel pump which supplies fuel to an internal combustion engine, and more particularly to such a fuel pump which includes an inlet valve assembly.
Fuel systems in modern internal combustion engines fueled by gasoline, particularly for use in the automotive market, employ gasoline direct injection (GDi) where fuel injectors are provided which inject fuel directly into combustion chambers of the internal combustion engine. In such systems employing GDi, fuel from a fuel tank is supplied under relatively low pressure by a low-pressure fuel pump which is typically an electric fuel pump located within the fuel tank. The low-pressure fuel pump supplies the fuel to a high-pressure fuel pump which typically includes a pumping plunger which is reciprocated by a camshaft of the internal combustion engine. Reciprocation of the pumping plunger further pressurizes the fuel in order to be supplied to fuel injectors which inject the fuel directly into the combustion chambers of the internal combustion engine. During operation, the internal combustion is subject to varying demands for output torque. In order to accommodate the varying output torque demands, the mass of fuel delivered by each stroke of the pumping plunger must also be varied. One strategy to vary the delivery of fuel by the high-pressure fuel pump is to use a digital inlet valve which allows a full charge of fuel to enter the pumping chamber during each intake stroke, however, the digital inlet valve may be allowed to remain open during a portion of a compression stroke of the pumping plunger to allow some fuel to spill back toward the source. When the digital inlet valve is closed during the remainder of the compression stroke, the fuel is pressurized and the pressurized fuel is supplied to the fuel injectors. Examples of such an arrangement are disclosed in U.S. Pat. No. 7,401,594 to Usui et al. and in U.S. Pat. No. 7,707,996 to Yamada et al.
Digital inlet valves commonly include a check valve which is selectively held open during a portion of the compression stroke by a solenoid assembly to determine the fuel charge that is supplied to the fuel injectors. The solenoid assembly includes a pole piece which is stationary and an armature which is moveable based on application of an electric current to a coil. When the coil is energized with electricity, the armature is attracted to the pole piece. Conversely, when the coil is not energized, a return spring urges the armature away from the pole piece. In order to affect the state of the check valve, a control rod is rigidly fixed to the armature such that when the coil is not energized, the control rod urges the check valve to be held in an open position. Conversely, when the coil is energized, the control rod is moved to allow the check valve to open and close as a check valve normally functions based on the differential pressure across the check valve. When the coil is either energized or de-energized and the armature and control rod combination changes position, noise is generated when the combination of the armature and the control rod reaches a travel stop. Since the armature and the control rod are rigidly fixed to each other, the noise generated is a function of the total mass of the armature and the control rod and the impact velocity of the armature and control rod combination when the combination reaches the travel stop.
What is needed is a fuel pump and inlet check valve which minimizes or eliminates one or more of the shortcomings as set forth above.
Briefly described, a fuel pump includes a fuel pump housing with a pumping chamber defined therein; a pumping plunger which reciprocates within a plunger bore along a plunger bore axis such that an intake stroke of the pumping plunger increases volume of the pumping chamber and a compression stroke of the pumping plunger decreases volume of the pumping chamber; and an inlet valve assembly. The inlet valve assembly includes a check valve member which is moveable between 1) an unseated position which provides fluid communication between the pumping chamber and a fuel supply passage and 2) a seated position which prevents fluid communication between the pumping chamber and the fuel supply passage; and a solenoid assembly. The solenoid assembly includes a wire winding; a pole piece; an armature which is moveable along an inlet valve axis between 1) a first position when the wire winding is not energized with electricity and 2) a second position when the wire winding is energized with electricity; a return spring which biases the armature away from the pole piece; and a control rod which is moveable along the inlet valve axis independently of the armature. The first position of the armature urges the control rod to hold the check valve member in the unseated position and the second position of the armature allows the check valve member to move the control rod to allow the check valve member to move to the seated position. The fuel pump and inlet valve assembly as described herein minimize noise associated with operation of the inlet valve assembly by allowing the armature and the control rod to move independently of each other, thereby providing smaller, individual impacts when changing positions. Additionally, allowing the armature and the control rod to move independently of each other allows the armature to impact the pole piece with greater parallelism which helps to create a hydraulic damping effect that slows down the armature as it reaches the pole piece; thereby minimizing impact noise.
Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.
This invention will be further described with reference to the accompanying drawings in which:
In accordance with a preferred embodiment of this invention and referring initially to
As shown, low-pressure fuel pump 18 may be provided within fuel tank 14, however low-pressure fuel pump 18 may alternatively be provided outside of fuel tank 14. Low-pressure fuel pump 18 may be an electric fuel pump as are well known to a practitioner of ordinary skill in the art. A low-pressure fuel supply passage 22 provides fluid communication from low-pressure fuel pump 18 to high-pressure fuel pump 20. A fuel pressure regulator 24 may be provided such that fuel pressure regulator 24 maintains a substantially uniform pressure within low-pressure fuel supply passage 22 by returning a portion of the fuel supplied by low-pressure fuel pump 18 to fuel tank 14 through a fuel return passage 26. While fuel pressure regulator 24 has been illustrated in low-pressure fuel supply passage 22 outside of fuel tank 14, it should be understood that fuel pressure regulator 24 may be located within fuel tank 14 and may be integrated with low-pressure fuel pump 18.
Now with additional reference to
Outlet valve assembly 42 generally includes an outlet valve member 42a, an outlet valve seat 42b, and an outlet valve spring 42c. Outlet valve member 42a, illustrated by way of non-limiting example only as a ball, is biased toward outlet valve seat 42b by outlet valve spring 42c where outlet valve spring 42c is selected to allow outlet valve member 42a to open when a predetermined pressure differential between pumping chamber 38 and fuel rail 44 is achieved. Outlet valve assembly 42 is oriented such that fuel is allowed to flow out of pumping chamber 38 through outlet valve assembly 42, however, fuel is not allowed to flow into pumping chamber 38 through outlet valve assembly 42.
Pressure relief valve assembly 48 generally includes a pressure relief valve member 48a, a pressure relief valve seat 48b, and a pressure relief valve spring 48c. Pressure relief valve member 48a, illustrated by way of non-limiting example only as a ball, is biased toward pressure relief valve seat 48b by pressure relief valve spring 48c where pressure relief valve spring 48c is selected to allow pressure relief valve member 48a to open when a predetermined pressure differential between pumping chamber 38 and fuel rail 44 is achieved. Pressure relief valve assembly 48 is oriented such that fuel is allowed to flow into pumping chamber 38 through pressure relief valve assembly 48, however, fuel is not allowed to flow out of pumping chamber 38 through pressure relief valve assembly 48.
Inlet valve assembly 40 will now be described with continued reference to
Valve body 50 is centered about, and extends along, an inlet valve axis 56 such that valve body 50 extends from a valve body first end 50a to a valve body second end 50b. A valve body bore 58 extends into valve body 50 from valve body first end 50a and terminates at a valve body end wall 60 which extends to valve body second end 50b such that valve body bore 58 is preferably cylindrical. One or more valve body inlet passages 62 extend through valve body 50 such that valve body inlet passages 62 extend from a valve body outer periphery 50c of valve body 50 and open into valve body bore 58. As shown, valve body 50 may be of multi-piece construction or may alternatively be formed from a single piece of material.
A valve body central passage 66 extends through valve body end wall 60 such that valve body central passage 66 connects valve body second end 50b with valve body bore 58 and such that valve body central passage 66 is centered about, and extends along, inlet valve axis 56. A plurality of valve body outlet passages 68 is provided in valve body end wall 60 such that each valve body outlet passage 68 extends through valve body end wall 60 and such that each valve body outlet passage 68 connects valve body second end 50b with valve body bore 58. Each valve body outlet passage 68 is laterally offset from valve body central passage 66 and extends through valve body end wall 60 in a direction parallel to inlet valve axis 56.
Check valve 52 includes a check valve member 78 and a travel limiter 80. Check valve 52 is arranged at valve body second end 50b such that check valve member 78 is moved between a seated position which blocks valve body outlet passages 68 (shown in
Solenoid assembly 54 includes an inner housing 82, a pole piece 84 located within inner housing 82, an armature 85 located within inner housing 82, a return spring 86 which biases armature 83 away from pole piece 84, a control rod 87, a spool 88, a coil 90, an overmold 92, and an outer housing 94. The various elements of solenoid assembly 54 will be described in greater detail in the paragraphs that follow.
Inner housing 82 is hollow and is centered about, and extends along, inlet valve axis 56. The outer periphery of inner housing 82 sealingly engages the inner periphery of valve body bore 58.
Pole piece 84 is made of a magnetically permeable material and is received within inner housing 82 in fixed relationship to inner housing 82, for example by interference fit or welding, such that pole piece 84 is centered about, and extends along, inlet valve axis 56. A pole piece first end 84a of pole piece 84 includes a pole piece spring pocket 84b extending thereinto from pole piece first end 84a to a pole piece spring pocket bottom surface 84c such that pole piece spring pocket 84b may be cylindrical and centered about inlet valve axis 56 and such that a portion of return spring 86 is located within pole piece spring pocket 84b in abutment with pole piece spring pocket bottom surface 84c.
Armature 85 is made of a material which is attracted by a magnet and is received within inner housing 82 in a slidable relationship to inner housing 82 along inlet valve axis 56 such that armature 85 is centered about, and extends along, inlet valve axis 56. Armature 85 may be of two-piece construction as shown which includes an armature first portion 85a which is proximal to pole piece 84 and an armature second portion 85b which is fixed to armature first portion 85a, for example, by welding or mechanical fasteners and which is distal from pole piece 84. Armature first portion 85a includes an armature spring bore 85c extending thereinto from an armature first end 85d which is proximal to pole piece 84 and which is centered about, and extends along, inlet valve axis 56. A portion of return spring 86 is located within armature spring bore 85c and abuts against armature second portion 85b such that return spring 86 is held in compression between armature second portion 85b and pole piece spring pocket bottom surface 84c, thereby biasing armature 85 in a direction away from pole piece 84. Armature second portion 85b includes an armature control rod bore 85e extending axially therethrough such that armature control rod bore 85e is centered about, and extends along, inlet valve axis 56.
Control rod 87 extends from a control rod first end 87a which is proximal to armature 85 to a control rod second end 87b which is proximal to check valve member 78 such that control rod 87 is centered about, and extends along, inlet valve axis 56. Control rod 87 includes a control rod first shoulder 87c which is annular in shape and faces toward armature 85, and as shown, is transverse to inlet valve axis 56. A control rod first surface 87d extends from control rod first end 87a to control rod first shoulder 87c such that control rod first surface 87d is located at least partially within armature control rod bore 85e in a close sliding interface which allows control rod first surface 87d to freely move axially, i.e. along inlet valve axis 56, within armature control rod bore 85e while preventing radial movement, i.e. transverse to inlet valve axis 56, of control rod first surface 87d within armature control rod bore 85e. It is important to note that the close sliding interface between control rod first surface 87d and armature control rod bore 85e allows control rod 87 to move along inlet valve axis 56 independently of armature 85. Control rod first shoulder 87c limits the extent to which control rod first surface 87d is inserted into armature control rod bore 85e and control rod first shoulder 87c also provides a surface for armature 85 to react against in order to move control rod 87 toward check valve member 78 as will be described in greater detail later. Control rod 87 includes a control rod second shoulder 87e which is annular in shape and faces toward valve body end wall 60, and as shown, is transverse to inlet valve axis 56. A control rod second surface 87f extends from control rod second end 87b to control rod second shoulder 87e such that control rod second surface 87f is located at least partially within valve body central passage 66 in a close sliding interface which allows control rod second surface 87f to freely move axially, i.e. along inlet valve axis 56, within valve body central passage 66 while preventing radial movement, i.e. transverse to inlet valve axis 56, of control rod second surface 87f within valve body central passage 66. In use, control rod second end 87b is used to interface with check valve 52, and more particularly check valve member 78, as will be described in greater detail later.
As illustrated herein, control rod 87 may be of multi-piece construction which includes a control rod central portion 87g, a control rod first bushing 87h which is tubular and fixed to control rod central portion 87g, and a control rod second bushing 87i which is tubular and fixed to control rod central portion 87g. Control rod central portion 87g is preferably cylindrical and is centered about inlet valve axis 56 such that control rod central portion 87g extends from control rod first end 87a to control rod second end 87b. By way of non-limiting example only, control rod central portion 87g may be a roller bearing which is commercially available. Control rod first bushing 87h is preferably cylindrical on its outer periphery which is centered about, and extends along inlet valve axis 56 such that control rod first shoulder 87c is defined by one axial end of control rod first bushing 87h. Control rod first bushing 87h includes a control rod first bushing bore 87j extending axially therethrough such that control rod first bushing bore 87j is preferably cylindrical. In order to prevent relative movement between control rod first bushing 87h and control rod central portion 87g, control rod first bushing 87h is fixed to control rod central portion 87g, for example, by one or more of interference fit between control rod first bushing bore 87j and control rod central portion 87g and welding. Similarly, control rod second bushing 87i is preferably cylindrical on its outer periphery which is centered about, and extends along, inlet valve axis 56 such that control rod second shoulder 87e is defined by one axial end of control rod second bushing 87i. Control rod second bushing 87i includes a control rod second bushing bore 87k extending axially therethrough such that control rod second bushing bore 87k is preferably cylindrical. In order to prevent relative movement between control rod second bushing 87i and control rod central portion 87g, control rod second bushing 87i is fixed to control rod central portion 87g, for example, by one or more of interference fit between control rod second bushing bore 87k and control rod central portion 87g and welding. By making control rod 87 a multi-piece component, control rod central portion 87g may be provided as a roller bearing which is commercially available in high volumes at low cost with surface finishes and tolerances which are important to the close sliding fit needed between control rod 87 and valve body central passage 66 and between control rod 87 and armature control rod bore 85e. In an alternative arrangement, control rod first bushing 87h and control rod second bushing 87i may be combined to be a single bushing which minimizes the number of components, but has the drawback of increasing mass. In a further alternative, control rod 87 may be formed as a single piece of material in a turning operation.
Spool 88 is made of an electrically insulative material, for example plastic, and is centered about, and extends along, inlet valve axis 56 such that spool 88 circumferentially surrounds inner housing 82 in a close-fitting relationship. Coil 90 is a winding of electrically conductive wire which is wound about the outer periphery of spool 88 such that coil 90 circumferentially surrounds a portion of pole piece 84. Consequently, when coil 90 is energized with an electric current, armature 85 is magnetically attracted to, and moved toward, pole piece 84, and when coil 90 is not energized with an electric current, armature 85 is moved away from pole piece 84 by return spring 86. A more detailed description of operation will be provided later.
Outer housing 94 circumferentially surrounds inner housing 82, spool 88, and coil 90 such that spool 88 and coil 90 are located radially between inner housing 82 and outer housing 94. Overmold 92 is an electrically insulative material, for example plastic, which fills the void between spool 88/coil 90 and outer housing 94 such that overmold 92 extends axially from outer housing 94 to define an electrical connector 96 which includes terminals (not shown) that are connected to opposite ends of coil 90. Electrical connector 96 is configured to mate with a complementary electrical connector (not show) for supplying electric current to coil 90 in use. As shown, a coil washer 98 may be provided within outer housing 94 axially between coil 90 and overmold 92 in order to complete the magnetic circuit of solenoid assembly 54.
Operation of high-pressure fuel pump 20, and in particular, inlet valve assembly 40, will now be described with particular reference to
Now with particular reference to
High-pressure fuel pump 20 with inlet valve assembly 40 as described herein helps to minimize noise associated with operation of inlet valve assembly 40 by allowing armature 85 and control rod 87 to move independently of each other, thereby providing smaller, individual impacts when changing positions from energized to un-energized, i.e. individual impacts resulting from armature 85 and control rod 87 at different times, and also thereby providing a smaller impact when changing positions from un-energized to energized, i.e. impact resulting only from the mass of armature 85. Referring now to
While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
