Diaphragm Carburetor

Abstract

Disclosed herein is a carburetor which includes two diaphragm chambers within the carburetor housing. One diaphragm chamber forms part of a pulse actuated fuel pump and the other diaphragm chamber is the main fuel metering diaphragm chamber. Both the fuel pump and the main diaphragm chamber are formed from opposed recesses in mating surfaces of a housing cover and a housing surface. The opposed recesses forming each diaphragm chamber are separated by a common diaphragm which extends between the mating surfaces of the cover and housing. The fuel pump is operated by pressure variations in the crankcase which communicate with the fuel pump through a passage in the carburetor housing.

Description

BACKGROUND OF INVENTION

In some prior carburetors a separate fuel pump is typically used to supply fuel to the fuel chamber portion of a diaphragm chamber. When the fuel pump is integral with the carburetor housing the main diaphragm chamber and fuel pump chamber are typically in a stacked array with the two chambers separated by an intermediate housing partition. This construction requires the use of several gaskets and close tolerances to insure alignment of connecting passages and results in high assembly time and manufacturing costs.

SUMMARY OF INVENTION

The invention provides a diaphragm carburetor which utilizes a common diaphragm for the main metering diaphragm chamber and a pulse actuated fuel pump or second diaphragm chamber located within the same carburetor housing. The use of a common diaphragm is made possible by a construction in which the two diaphragm chambers are located along the interface or mating surfaces of the housing and a housing cover. The common diaphragm separates two sets of opposed recesses in the cover and housing into fuel chamber portions and air chamber portions for both diaphragm chambers. The air chamber portion of the fuel pump communicates with the engine crankcase through a passage in the carburetor housing. Pressure variations from the crankcase cause a fluctuation of the diaphragm in the fuel pump to induce flow through a fuel conduit into the fuel chamber portion of the fuel pump and from the fuel pump to the main diaphragm chamber.

A flapper type check valve formed from the common diaphragm is provided for the main orifice to prevent back bleeding of air into the idle system when the engine is idling. The flapper type check valve eliminates the need for a special valve seat and housing assembly for the valve components, thus decreasing the cost of manufacture.

Further objects and advantages of the invention will become apparent from the following disclosure.

DRAWINGS

FIG. 1 is a fragmentary sectional view of a two cycle engine embodying the carburetor of the invention.

FIG. 2 is a schematic view of a carburetor in accordance with the invention.

FIG. 3 is an enlarged top view of the carburetor shown in FIG. 1 and a fragmentary view of the engine.

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3.

FIG. 5 is a top view of the carburetor housing with the cover removed.

FIG. 6 is a sectional view taken along line 6--6 of FIG. 5.

FIG. 7 is a sectional view taken along line 7--7 of FIG. 5.

FIG. 8 is a plan view of the diaphragm shown in FIGS. 3, 4, 5 and 6.

FIG. 9 is a sectional view taken along line 9--9 of FIG. 5.

FIG. 10 is a sectional view taken along line 10--10 of FIG. 5.

FIG. 11 is a sectional view taken along line 11--11 of FIG. 5.

FIG. 12 is an enlarged sectional view taken along line 12--12 of FIG. 13.

FIG. 13 is a plan view of the valve member shown in FIG. 12.

FIG. 14 is an enlarged sectional view taken along line 14--14 of FIG. 5.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a two cycle engine 106 having a crankcase 108 with a crankcase reed valve 110 located in a crankcase induction passage 112. A carburetor 114 is connected to the engine 106. As shown in the schematic diagram in FIG. 2, the carburetor 114 has a body 115 which includes a housing 118 and a housing cover 117. The housing 118 includes a fuel-air induction passage 116. The induction passage 116 communicates with the crankcase through the passage 112 and the reed valve 110. The carburetor also includes a venturi 120, a mixing chamber 122 which communicates with a high speed jet or fuel inlet 124, and a throttle shutter 126.

In accordance with the invention, means are provided defining a first or main metering diaphragm chamber 128 and a fuel pump or second diaphragm chamber 130 in the carburetor body 115. In the construction disclosed in FIG. 2, the first diaphragm chamber 128 is defined by a recess or relieved wall portion 132 in housing 118 and a complementary opposed recess or relieved wall portion 134 in the housing cover 117. The second diaphragm chamber 130 is defined by a relieved wall portion 138 in upper face 140 of housing 118 and a complementary opposed relieved wall portion 142 in the cover 117.

The location of the first and second diaphragm chambers 128 and 130 along the interface between the cover 117 and the adjacent housing surface affords the use of a single diaphragm 148 for both diaphragm chambers 128 and 130. The first diaphragm chamber 128 is separated into a fuel chamber portion 144 and an air chamber portion 146 by the diaphragm 148 which can extend the full length and width of the housing face or surface 140 and which has a diaphragm section 149 located between recesses 132 and 134. Air chamber portion 146 communicates with the atmosphere through a vent or passage 154.

The diaphragm 148 also has a section 151 which separates diaphragm chamber 130 into a fuel chamber portion 150 and an air chamber portion 152. The air chamber portion of the second diaphragm chamber 130 communicates with the crankcase 108 through a passage 156 which communicates pressure pulses or variations in the crankcase 108 to the air chamber portion 152, thus causing fluctuations of the diaphragm section 151 in the second diaphragm chamber 130 to pump fuel to the first diaphragm chamber as hereinafter described.

Fuel is supplied to the fuel chamber portion 150 through a fuel passage 160 which extends through housing 118 and which has a nipple 162 exteriorly of the housing 118 for connection to the fuel supply (not shown).

To minimize construction costs and eliminate conventional check valves requiring a valve seat and check member, the passage 160 is provided with a flap valve 164 which is formed from the diaphragm 148 by removal of an arcuate portion of the diaphragm by stamping or cutting, leaving a flap 164 in the form of a flexible tongue which is hinged along one edge to the diaphragm 148. The flap 164 is movable into a valve chamber 166 which communicates with the fuel chamber portion 150 of the second diaphragm chamber 130 by a passage 168. Valve 164 permits fluid flow into the fuel chamber portion but prevents fuel outflow from the fuel chamber portion 150 through conduit or passage 160, thus causing a pumping action to supply fuel to the first diaphragm chamber 128.

Fuel flow from the fuel chamber portion 150 to the fuel chamber portion 144 of the first diaphragm chamber 128 is provided by a passage 170. The passage 170 and the fuel chamber portion 150 are provided with an outlet valve in the form of a flap 172 which extends over an opening 174 which communicates with the fuel chamber portion 150. The flap valve 172 is movable in a valve chamber 176 which communicates with the passage 170.

In the alternative the valve 172 can be located at the interface between the cover 117 and the housing 118 and and formed from a portion of the diaphragm 148.

Fuel is emitted or metered into the fuel chamber portion 144 of the main diaphragm chamber by a valve member 179 which is located in a bore or valve chamber 180 in the housing 118 and which communicates with the fuel chamber portion 144. Valve member 179 is actuated by an arm 181 which is pivoted to the housing at 182 and spring biased into engagement with a button 183 on the diaphragm 148 by a spring 184 located in the fuel chamber portion 144. Fuel is supplied to the high speed nozzle or fuel outlet 124 by a passage 185 controlled by a metering valve 186. Fuel flow into the passage 185 is controlled by a flap valve 187 formed from a portion of diaphragm 148 which closes across the end of a passage 188 in housing 118. Passage 188 communicates with the fuel chamber portion 144 at 189.

Idle fuel is supplied to idling orifices 190 through a passage 192 which is located in the housing 118 and which is controlled by an idle metering valve 193.

A preferred embodiment of the invention is disclosed in FIG. 1 and FIGS. 3 through 13. As shown in FIGS. 4, 9 and 10, a carburetor 214 has a body 215 which includes a housing 218 and a housing cover 217. The housing 218 includes a fuel-air induction passage 216. The carburetor induction passage 216 has a venturi 220 (FIG. 4) and a mixing chamber 222 which communicates with a high speed jet or fuel inlet 224. A throttle shutter 226 regulates flow to the engine crankcase.

In the preferred embodiment, the means defining a first diaphragm chamber 228 in the housing 218 comprises a recess or relieved wall portion 232 (FIGS. 4, 11) in the housing 218 and a complementary opposed recess or relieved wall portion 234 in the housing cover 217 which is bolted or otherwise secured to the housing 218. The means defining a second diaphragm chamber 230 comprises a recess or relieved wall portion 238 (FIGS. 7, 11) in the upper face 240 of the housing 218 and a complementary recess or opposed relieved wall portion 242 in the cover 217.

The diaphragm chamber 228 is separated into a fuel chamber portion 244 and an air chamber portion 246 by a diaphragm 248 which extends the full length and width of face 240 and is sandwiched between the cover 217 and the housing 218. Diaphragm 248 has a diaphragm section 249 located between the recesses 232 and 234. The diaphragm 248 has a section 251 which separates the second diaphragm chamber 230 into a fuel chamber portion 250 and an air chamber portion 252. The air chamber portion 246 communicates with the atmosphere through a vent passage 254 (FIG. 11). The air chamber portion 252 of the second diaphragm chamber 230 communicates with the engine crankcase 108 through a passage 256 (FIGS. 3 and 5).

Fuel is supplied to the fuel chamber portion 250 of the second diaphragm chamber 230 by a fuel passage 260 (FIG. 7) which extends through a portion of housing 218 and has a nipple 262 adapted to be connected to a fuel line or to the fuel supply.

Passage 260 is provided with a fuel inlet valve 264 (FIGS. 5, 7) which comprises a flap 265 which is formed by cutting or stamping the diaphragm to remove a portion of the diaphragm, as shown in FIG. 8. The flap is movable within a valve chamber 266 (FIG. 7) to permit fuel inflow and prevent fuel outflow during pumping action of the diaphragm section 251 located within the diaphragm chamber 230.

Fuel is conveyed from the fuel chamber portion 250 to the fuel chamber portion 244 of the first diaphragm chamber 228 by a passage 270 (FIGS. 3, 6, 12). Fuel flow into the passage 270 is controlled by an outlet check valve 271 (FIGS. 12, 13) in the form of a flap 272 which extends over an aperture 274 which communicates with the fuel chamber portion 250. The flap 272 is movable between a support 273 and a downwardly extending boss 275 on the cover 217.

Fuel is metered into the fuel chamber portion 244 by a valve member 279 (FIGS. 6, 11) located in a bore or valve chamber 280 in the housing 218. The valve member 279 is actuated by an arm 281 which is pivoted to the housing at 282 and is spring biased into engagement with a button 283 on diaphragm 248 by a spring 284 located in the fuel chamber portion 244. Fuel flow from the fuel chamber portion 244 into the mixing chamber 222 through the outlet 224 is provided by a passage 285 (FIG. 9) controlled by a flap check valve 287 (FIGS. 8, 14). The metering valve 286 provides carburetor adjustment.

Idle fuel is supplied to idling orifices 290 (FIGS. 4, 10) through a passage 292 which communicates with the fuel chamber portion 232 and is controlled by a valve 293 (FIG. 10).

Various of the features of the invention are set forth in the following claims.

Claims

What is claimed is:

1. A carburetor comprising a carburetor body including a housing with a face having therein a fuel recess and a recess for gas under pulsating pressure, said housing also including an air induction passage provided with a fuel inlet, a first passage communicating between said fuel inlet and said fuel recess, a second passage communicating between said fuel recess and said face, a third passage communicating with said face and adapted to communicate with a source of fuel, and a fourth passage communicating with said recess for gas under pulsating pressure and adapted to communicate with a source of pulsating pressure gas, a single flexible diaphragm engaged with said housing face and having a first portion extending across said fuel recess, and a second portion extending across said recess for gas under pulsating pressure, a housing cover with a face having therein an air-chamber recess, and a fuel pumping recess adapted to communicate with a source of fuel, said housing cover also including a first passage communicating with said cover face and with said fuel pumping recess and a second passage communicating between said fuel pumping recess and said cover face, and means detachably connecting said cover to said housing with said fuel recess and said air-chamber recess in opposing relation to each other with said first diaphragm portion therebetween, with said recess for gas under pulsating pressure and said fuel pumping recess in opposing relation to each other with said second diaphragm portion therebetween, with said second passage in said housing communicating with said first passage in said cover and with said second passage in said cover communicating with said third passage in said housing.

2. A carburetor comprising a carburetor body including a housing with a face having therein a fuel recess and a recess for gas under pulsating pressure, said housing also including an air induction passage provided with a fuel inlet, a first passage communicating between said fuel inlet and said fuel recess, a second passage communicating between said fuel recess and said face, and a third passage communicating with said face and adapted to communicate with a source of fuel, a single flexible diaphragm engaged with said housing face and having a first portion extending across said fuel recess, a second portion extending across said recess for gas under pulsating pressure, and a third portion extending across the end of said third house passage at said face and including fapper valve means for permitting flow from and preventing flow to said third housing passage, a housing cover with a face having therein an air-chamber recess, and a fuel pumping recess adapted to communicate with a source of fuel, said housing cover also including a first passage communicating with said cover face and with said fuel pumping recess and a second passage communicating between said fuel pumping recess and said cover face, and means detachably connecting said cover to said housing with said fuel recess and said air-chamber recess in opposing relation to each other with said first diaphragm portion therebetween, with said recess for gas under pulsating pressure and said fuel pumping recess in opposing relation to each other with said second diaphragm portion therebetween, with said second passage in said housing communicating with said first passage in said cover, and with said second passage in said cover communicating with said third passage in said housing subject to the control of said flapper valve means.

3. A carburetor comprising a carburetor body including a housing with a face having therein a fuel recess and a recess for gas under pulsating pressure, said housing also including an air induction passage provided with a high speed fuel inlet, a first passage communicating between said high speed fuel inlet and said face, a second passage communicating between said fuel recess and said face, a fuel supply passage communicating between said fuel recess and said face, and a fourth passage communicating with said face and adapted to communicate with a source of fuel, a single flexible diaphragm engaged with said housing face and having a first portion extending across said fuel recess, a second portion extending across said recess for gas under pulsating pressure, a third portion extending across the end of said second housing passage at said face and including a flapper valve means adapted for permitting flow from and preventing flow to said second housing passage, and a fourth portion extending across the end of said fourth housing passage at said face and including second flapper valve means for permitting flow from and preventing flow to said fourth housing passage, a housing cover with a face having therein an air-chamber recess and a fuel pumping recess, said housing cover also including a first fuel passage communicating with said cover face, a second fuel passage communicating with said cover face and with said fuel pumping recess, and a third passage communicating between said fuel pumping recess and said cover face, means detachably connecting said cover to said housing with said fuel recess and said air-chamber recess in opposing relation to each other with said first diaphragm portion therebetween, with said recess for gas under pulsating pressure and said fuel pumping recess in opposing relation to each other with said second diaphragm portion therebetween, with said first passage of said cover communicating with said first and second passages of said housing subject to the control of said first flapper valve means, with said fuel supply passage in said housing communicating with said second passage in said cover and with said third passage in said cover communicating with said fourth passage in said housing subject to the control of said second flapper valve means, whereby said cover can be removed to afford access to said diaphragm without other disconnection.

4. A carburetor in accordance with claim 3 wherein said housing includes an idle fuel inlet, a fifth passage communicating between said fuel recess and said idle fuel inlet, and a sixth passage communicating with said recess for gas under pulsating pressure and adapted to communicate with a source of pulsating pressure.

5. A carburetor in accordance with claim 4 wherein said housing cover also includes an air vent extending through said cover and communicating with said air-chamber recess, and wherein said fuel pumping recess includes a recessed portion, and further including a flapper valve located in said recessed portion for permitting fuel flow from and preventing flow to said fuel pumping recess, and wherein said second fuel passage in said cover communicates with said face and with said recessed portion of said fuel pumping recess subject to the control of said flapper valve.