Abstract:
A method of controlling the speed of an engine includes positioning a throttle at an operating position between an idle position that reduces the engine speed to an idle speed, and a normal speed position at which the engine runs at a speed greater than the idle speed, collecting a fluid within a manifold, sensing a pressure within the manifold, and adjusting the operating position of the throttle in response to the sensed pressure. When the sensed pressure is low, the throttle is moved toward the idle position and when the pressure is high, the throttle is moved toward the normal speed position. The method further includes positioning an unloader downstream of the manifold, the manifold configured in one of a first position in which the unloader directs fluid from the manifold to the pump, and a second position in which the unloader directs fluid to a point of use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 11/729,692 filed Mar. 29, 2007, now U.S. Pat. No. ______, which claims the benefit of U.S. Provisional Patent Application No. 60/831,330 filed Jul. 17, 2006, the entire contents of each are hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to an idle down control for an engine. More particularly, the present invention relates to an idle down control for an engine that provides power for a pressure washer. 
         [0003]    Pressure washers use high-pressure liquid, typically water, to clean surfaces such as driveways, decks, walls, and the like. Generally, the pressure washer includes an engine that provides power to a pump. The pump operates to provide high-pressure fluid to a wand or a gun that includes a trigger mechanism that is actuated by the user to discharge the high-pressure fluid. Generally, the user squeezes the trigger with one hand and supports the discharge end of the gun with the other hand during use. 
         [0004]    During periods when high-pressure water is not required, the user releases the trigger and high-pressure water from the pump discharge is directed back to the pump intake. 
       SUMMARY 
       [0005]    The invention provides an idle down control that includes a pressure sensor that detects a pressure downstream of a pump. An actuator moves in response to the detected pressure between a first position in which the engine throttle is forced to an idle position, and a second position in which the engine throttle is free to move between the idle position and a wide open position. The pressure sensor measures the pressure at the pump outlet manifold such that a drop in pressure results in movement of the actuator to the first position. The position of the sensor is such that it detects a drop in pressure when fluid is being bypassed from the pump outlet to the pump inlet. 
         [0006]    In one construction, the invention provides a method of controlling the speed of an engine that powers a pressure washer pump. The method includes positioning a throttle at an operating position between an idle position that reduces the engine speed to an idle speed, and a normal speed position at which the engine runs at a speed greater than the idle speed. The method also includes collecting a fluid within a manifold immediately as it is discharged from the pump, sensing a pressure within the manifold, and adjusting the operating position of the throttle in response to the sensed pressure. When the sensed pressure is low, the throttle is moved toward the idle position and when the pressure is high, the throttle is moved toward the normal speed position. The method further includes positioning an unloader downstream of the manifold and configuring the unloader in one of a first position in which the unloader directs fluid from the manifold to the pump such that the sensed pressure is low, and a second position in which the unloader directs fluid from the manifold to a point of use and the sensed pressure is high. 
         [0007]    In another construction, the invention provides a method of controlling the speed of an engine that powers a pressure washer pump. The method includes configuring a throttle to operate between an idle position that reduces the engine speed to an idle speed, and a normal speed position at which the engine runs at a speed greater than the idle speed. The method also includes providing a pressure sensor at a manifold to sense pressure of the fluid immediately as it is discharged from the pump and providing a linkage between the pressure sensor and the throttle to adjust the operating position of the throttle in response to the sensed pressure. When the sensed pressure is low, the throttle is moved toward the idle position and when the sensed pressure is high, the throttle is moved toward the normal speed position. The method further includes providing an unloader downstream of the manifold and the pressure sensor. In a first position, the unloader directs fluid from the manifold back to the pump, and in a second position, the unloader directs fluid from the manifold to a point of use. 
         [0008]    In yet another construction, the invention provides a pressure washer configured to output a pressurized fluid to a point of use. The pressure washer includes an engine having a throttle movable between an idle position that reduces the engine speed to an idle speed, and a normal speed position at which the engine runs at a speed greater than the idle speed. The pressure washer also includes a pump having an inlet and an outlet that discharges fluid, said pump powered by the engine to pressurize the fluid and a manifold positioned to immediately receive the fluid discharged from the pump outlet such that a manifold pressure is substantially equal to a pump discharge pressure. An unloader is positioned between the manifold and the point of use. The unloader is configurable in a first configuration in which fluid flows from the manifold to the point of use and a second configuration in which fluid flows from the manifold to the pump inlet, and wherein the manifold pressure is high when the unloader is in the first configuration and is low when the unloader is in the second configuration. A pressure sensor is configured to continuously detect the manifold pressure without flow passing through the sensor and an actuator is responsive to the detected manifold pressure to move between a first position when the detected manifold pressure is low, and a second position when the detected manifold pressure high. A linkage is connected between the actuator and the throttle to move the throttle to the idle position when the actuator is in the first position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a pressure washer including a gun; 
           [0010]      FIG. 2  is a top view of another pressure washer including an engine, a pump, and an idle down control; 
           [0011]      FIG. 3  is a top view of a portion of the engine of  FIG. 2 ; 
           [0012]      FIG. 4  is a perspective view of the pump and a portion of the engine of  FIG. 2 ; 
           [0013]      FIG. 5  is a perspective view of the idle down control of  FIG. 2  on the engine of  FIG. 2 ; 
           [0014]      FIG. 6  is a perspective view of the idle down control of  FIG. 2  on the engine of  FIG. 2 ; 
           [0015]      FIG. 7  is a perspective view of the idle down control of  FIG. 2 ; 
           [0016]      FIG. 8  is a bottom view of the idle down control of  FIG. 2 ; 
           [0017]      FIG. 9  is a partially broken away view of an exemplary unloader valve and regulator of the type that could be used with the present invention; and 
           [0018]      FIG. 10  is a section view of the idle down control of  FIG. 2  taken along line  10 - 10  of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0020]      FIG. 1  illustrates one possible pressure washer  10  that employs the invention. As one of ordinary skill will realize, the invention described herein is suitable for use with most pressure washers that output a pressurized liquid. As such, the invention should not be limited only to pressure washers  10  similar to the one illustrated in  FIG. 1 . The pressure washer  10  is a mobile pressure washer that includes a trigger-actuated gun  15 , an internal combustion engine  20 , and a pump  25 . The engine  20  drives the pump  25 , which draws fluid, typically water, from a source (e.g., an onboard reservoir, a garden hose, an external tank, etc.) and selectively delivers the fluid to the gun  15 , via a hose  30 , under pressure. 
         [0021]    The gun  15  includes a trigger assembly  35  that allows the user to selectively discharge a flow of water from the gun  15 . Typically, the user squeezes the trigger  35  to open a valve (not shown) and begin the discharge of high-pressure fluid. When the user disengages the trigger  35 , the valve closes, and high-pressure flow is inhibited from exiting the gun  15 . 
         [0022]      FIG. 2  illustrates a pressure washer  10   a  that includes the engine  20  supported by a frame  40  having wheels  45  to allow for movement. In the illustrated construction, a one-cylinder horizontal shaft internal combustion engine is employed. Of course, other arrangements may employ a vertical shaft engine and/or a multi-cylinder engine if desired. In addition, other engine types (e.g., diesel, rotary, etc.) could also be employed. 
         [0023]    With reference to  FIG. 3 , the engine  20  includes a throttle  50  that is movable between an idle position and a wide open position to vary the flow of fuel and air to the engine  20 . When the throttle  50  is in the idle position the engine  20  operates at an idle speed, and when the throttle  50  is in the wide open position the engine  20  operates at a desired engine speed. 
         [0024]    The engine  20  also includes a crankcase  55 , a piston (not shown), a crankshaft (not shown), and one or more cam shafts (not shown). The crankshaft rotates in response to reciprocation of the piston to produce usable shaft power. The cam shaft or shafts are coupled to the crankshaft such that they rotate at one-half the crankshaft speed to actuate intake and exhaust valves for the engine  20 , as is well known in the art. 
         [0025]    A governor  60  is coupled to the throttle  50  to control the throttle position to maintain the engine  20  at the desired engine speed during operation. The governor  60  includes a speed sensor (not shown) that senses the actual operating speed of the engine  20 . If a typical mechanical governor is used, flyweights rotate in response to the rotation of the engine crankshaft or cam shaft such that the flyweights rotate at the engine speed, or one-half the engine speed (the cam shaft speed). In the illustrated construction, the speed sensor engages a governor shaft  65  that extends out of the crankcase  55  and engages a governor arm  70 . The governor arm  70  moves through an arc in response to changes in speed of the engine  20 . 
         [0026]    A link arm  75  includes a first end  80  that connects to the governor arm  70  and a second end  85  that is coupled to the throttle  50 . Thus, movement of the governor arm  70  produces a corresponding movement of the throttle  50 . A governor spring  90  is connected to the engine  20  and to the governor arm  70  to bias the arm  70  toward a first or wide open throttle direction. 
         [0027]    The governor arm  70  includes an extension  95  that defines a plurality of apertures  100 . A second spring  105  includes a first end  110  that is coupled to the extension  95  using one of the apertures  100 , and a second end  115  coupled to an idle control lever  120 . The spring  105  can be connected to any one of the apertures  100  to adjust the effect of the spring  105 . 
         [0028]    The idle control lever  120  is pivotally coupled to the engine  20  such that it rotates substantially freely about an axis. An idle lever  125  is coupled to the idle control lever  120  and an idle down controller  130 . 
         [0029]    With reference to  FIGS. 7 ,  8 , and  10 , the idle down controller  130  includes a housing  135 , a spring  140 , and an actuator  145  positioned within the housing  135 . In the illustrated construction, a one-piece housing  135  is employed, with other constructions employing multi-piece housings. The housing  135  includes a threaded aperture  150  (shown in  FIG. 8 ) that provides for fluid communication to a sensor aperture  155 . The sensor aperture  155  allows for the communication of the fluid pressure from the threaded aperture  150  to the actuator  145 . The sensor aperture  155  is about one-quarter of an inch in diameter, with larger or smaller apertures  155  also being suitable. The relatively large size of the aperture  155  reduces the likelihood of clogging in the controller  130 . The housing  135  also includes a shoulder portion  160  and a groove  165  that cooperate to attach the idle down controller  130  to the engine  20 , as will be described in more detail with regard to  FIG. 5 . 
         [0030]    The actuator  145  is movably supported by the housing  135  such that it can move between an idle position (shown in  FIGS. 7 and 8 ) and a normal speed position. When the actuator  145  is in the idle position, it overrides the governor  60  and forces the throttle  50  toward the idle position. When the actuator  145  is in the normal speed position, the idle down controller  130  allows the governor  60  to control the speed of the engine  20 . The actuator  145  includes a piston portion  170  and a connecting portion  175  that extends outside of the housing  135 . The connecting portion  175  engages the idle lever  125  to connect the actuator  145  to the throttle  50 . The piston portion  170  is in fluid communication with the sensor aperture  155  to allow the fluid pressure to act on the piston  170 . The spring  140  is positioned within the housing  135  to bias the actuator  145  into the normal speed position (illustrated in  FIGS. 7 and 8 ). 
         [0031]      FIG. 5  illustrates the attachment of the idle down controller  130  to the engine  20 . The engine  20  includes a support bracket  180  that defines an aperture sized to receive a portion of the housing  135 . The shoulder portion  160  engages one side of the bracket  180  such that the groove  165  extends through the aperture. An e-ring  185  engages the groove  165  to lock the idle down controller  130  in its operating position. Also visible in  FIG. 5  is a small breather aperture  190  formed in the end of the housing  135  opposite the actuator  145 . The breather aperture  190  provides an air flow path into and out of the housing  135  to allow the actuator  145  to move freely. 
         [0032]    As shown in  FIG. 4 , the pump  25  is coupled to the engine  20  such that rotation of the engine  20  produces a corresponding rotation of the pump  25 . In some constructions, a gearbox or other speed changing device is positioned between the engine  20  and the pump  25 , with preferred constructions employing a direct connection such that the pump  25  rotates at the same speed as the engine  20 . In the illustrated arrangement, a triplex pump is employed with other types of pumps  25  also being suitable for use. 
         [0033]    The pump  25  discharges high-pressure fluid to a manifold  195  attached to the outlet of the pump  25 . The manifold  195  (manifold  195   a  in the example shown in  FIG. 9 ) collects the fluid and directs it through an unloader valve  200  ( FIG. 9 ) and a pressure regulator  205  before the flow passes through the hose  30  to the gun  15 . One possible arrangement of the unloader valve  200  and pressure regulator  205  is illustrated partially broken away in  FIG. 9 . 
         [0034]    Returning to  FIG. 4 , a pressure line  210  provides fluid communication between the manifold  195  (upstream of the unloader valve  200  and the pressure regulator  205 ) and the sensor aperture  155  ( FIG. 8 ) of the idle down controller  130 . Thus, the pressure applied to the piston portion  170  ( FIG. 8 ) is substantially equal to the pressure at the manifold  195 , which is substantially equal to the outlet pressure of the pump  25 . 
         [0035]    The operation of the idle down controller  130  will be described with reference to  FIGS. 3 and 4 . The user starts the engine  20  to begin operation of the pump  25 . The pump  25  draws low-pressure fluid from the source, increases the pressure of the fluid, and delivers the fluid to the manifold  195 . The user grasps the gun  15  and aims it at the surface to be cleaned, then pulls the trigger  35  to open the valve and initiate the flow of high-pressure fluid out of the gun  15 . The engine  20  operates at a desired speed during the discharge of water from the gun  15  to produce a flow of high-pressure fluid that collects in the manifold  195  and then passes through the unloader valve  200  ( FIG. 9 ) and the pressure regulator  205 . The pressure regulator  205  reduces the pressure of the fluid to the desired operating pressure of the system. The manifold pressure is transferred to the sensor aperture  155  of the idle down controller  130  via the pressure line  210 . Because there is no flow through the idle down controller  130 , little or no flow passes through the pressure line  210 . Rather, the pressure simply increases or decreases with the manifold pressure. 
         [0036]    The high-pressure within the idle down controller  130  forces the actuator  145  inward against the biasing spring  140  toward the normal speed position such that the governor  60  can control the engine speed. As illustrated in  FIG. 6 , one or more washers  215  can be positioned between the shoulder portion  160  and the idle lever  125  to limit the travel of the actuator  145  as may be required to adjust the system. 
         [0037]    When the user releases the trigger  35 , a pressure increase occurs within the hose  30  and the gun  15 . The pressure increase forces the unloader valve  200  ( FIG. 9 ) to move to an open position to bypass the high-pressure fluid from the outlet of the pump  25  to the inlet of the pump  25 . Once the flow is bypassed, the pressure within the manifold  195 ,  195   a  drops substantially. The pressure drop is transmitted to the sensor aperture  155  of the idle down controller  130  via the pressure line  210 . The reduced fluid pressure on the system is such that the spring  140  within the housing  135  biases the actuator  145  outward to the position illustrated in  FIGS. 3 and 4 . In this position, the governor  60  is biased or forced toward the idle position and the engine speed is reduced to the idle speed. 
         [0038]    The ability to reduce the engine speed when high-pressure fluid is not required reduces wear on both the engine  20  and the pump  25 . In addition, reducing the engine speed can improve the fuel economy of the engine  20  in some situations. 
         [0039]    The positioning of the idle down controller  130  results in a very simple system. The idle down controller  130  is directly coupled to the engine  20  with a single pressure line  210  between the pump  25  and the controller  130 . In addition, the operation of the controller  130  is such that the controller  130  need not be overly sensitive because the difference in pressure between the high-pressure fluid (during discharge) and the low-pressure fluid (during bypass) is typically in excess of 1000 psi. For example, many types of pressure washers operate with a manifold pressure of between about 2000 psi and 4000 psi during fluid discharge. After the trigger  35  is released and the unloader valve  200  ( FIG. 9 ) moves to the unloaded position, the manifold pressure drops substantially, for example to about 300 psi for a 2000 psi rated pressure washer. Thus, the pressure difference between the high-pressure fluid and the low-pressure fluid is about 1700 psi or greater. The large pressure difference between the two operating pressures of the system allows for the use of a less sensitive or less finely tuned idle down controller  130 , thus reducing the cost of the system. The simplicity of the system further reduces the cost of manufacturing and assembling the various components. 
         [0040]    In addition, the present device moves the engine throttle  50  to the idle position in response to a drop in pressure, rather than an increase in pressure. Thus, should the pressure line  210  develop a leak or a clog, the pressure drop would likely result in the engine  20  idling rather than operating at full speed. 
         [0041]    It should be noted that while the foregoing describes the invention as being applied to an engine powered pressure washer, other constructions may be applied to motor driven pressure washers. In these arrangements, the idle down controller  130  actuates a device that is operable to reduce the rotational speed of the motor or stop the motor. For example, in one construction, the idle down controller  130  moves a switch that opens a circuit between the motor and the power supply to stop rotation of the motor. In other constructions, the idle down controller  130  moves a device that varies the flow of power to the motor. For example, a variable capacitor or a variable resistor could be employed. In still other constructions a frequency varying device is used to reduce the frequency of the electrical current provided to the motor, thereby slowing the motor. 
         [0042]    Thus, the invention provides, among other things, an idle down controller  130  that responds to pressure changes within the manifold  195  to reduce the engine speed to an idle speed in response to the closure of a valve in a pressure washer gun  15 .