Noise reduction apparatus and method

Abstract

An apparatus and method for operating an auxiliary hydraulic load at low noise levels. A pump having a capacity which is sufficiently large to supply the load with the necessary volume of hydraulic fluid at relatively low pump speeds is driven by an engine operating at a speed near its idling speed. Throttle control means control the fuel supply to the engine at a level sufficient to drive the pump while maintaining the engine speed near its idling speed. When the engine speed is increased to a predetermined level in excess of its idling speed, means are provided to maintain the output from the pump at or below a predetermined flow rate to not overload the pump means or the auxiliary load. The pump may include a variable displacement pump or a plurality of fixed displacement pumps with means to vary the pump output in response to the pressure demand from the auxiliary load to maintain the torque input requirements for the pump below a predetermined level. The throttle control means may be actuated in response to the pressure demands of the auxiliary load to vary the torque from the engine in response to the torque input required for operation of the pump while the engine is operating at a speed near its idling speed.

I claim: 
     
       1. In combination for reducing noise from an engine of a vehicle in driving an auxiliary mechanism disposed on the vehicle where the mechanism is auxiliary to the operation of the vehicle, first means operable to provide for an operation of the auxiliary mechanism,   second means responsive to the operation of the first means for maintaining the vehicle engine at a speed near the idling speed,   third means responsive to the operation of the vehicle engine at a speed near the idling speed for producing a flow of fluid under pressure at a controlled rate to obtain the operation of the auxiliary mechanism, and   fourth means responsive to the flow of fluid from the third means for providing for introduction of such fluid to the auxiliary mechanism to drive the auxiliary mechanism.   
     
     
       2. The combination as set forth in claim 1 wherein fifth means are responsive to the operation of the engine at a particular speed above idling to limit the operation of the third means in supplying fluid under pressure to the fourth means. 
     
     
       3. The combination as set forth in claim 2 wherein the third means and the fourth means are connected in an open loop to provide for an accumulation of fluid from the third means at particular times during the operation of the auxiliary mechanism to vary the fluid for driving the auxiliary mechanism in accordance with such accumulation. 
     
     
       4. The combination set forth in claim 3 wherein means are responsive to the operation of the engine at intermediate speeds between engine idling and the particular speed for obtaining a controlled supply of fluid under pressure from the third means to the fourth means.   
     
     
       5. In combination for reducing noise, an engine for driving a vehicle,   an auxiliary mechanism disposed on the vehicle for providing an auxiliary operation distinct from the driving of the vehicle,   first means operable to initiate an operation of the auxiliary mechanism,   second means responsive to the operation of the first means for maintaining the engine at a speed near the idling speed,   third means responsive to the operation of the engine at a speed near the idling speed, upon the operation of the first means, for supplying fluid under pressure to operate the auxiliary mechanism, and   fourth means responsive to the supply of fluid from the third means for operating the auxiliary mechanism in accordance with such supply.   
     
     
       6. The combination set forth in claim 5 wherein fifth means are responsive to the operation of the engine at a particular speed above idling speed for limiting the supply of fluid from the third means to the fourth means even upon an operation of the first means. 
     
     
       7. The combination set forth in claim 5 wherein the auxiliary mechanism required variable amounts of power during its operation and wherein fifth means are provided for producing a variable accumulation of fluid from the third means in accordance with the variable amounts of power required for the auxiliary mechanism and wherein the fourth means operates the auxiliary mechanism in accordance with the variable accumulation of fluid by the fifth means and in accordance with the variable amounts of power required for the auxiliary mechanism.   
     
     
       8. The combination as set forth in claim 7 wherein means are provided for controlling the amount of fluid supplied by the third means to the fourth means at engine speeds intermediate the idling speed and the particular speed.   
     
     
       9. The combination set forth in claim 7 wherein the third, fourth and fifth means and the auxiliary mechanism are connected in an open loop to provide for the variable accumulation of fluid by the fifth means from the third means.   
     
     
       10. A noise reduction apparatus for operating a variable volume and variable pressure auxiliary load; said apparatus comprising: pump means having a capacity which is sufficiently large to supply said load at a relatively low pump speed;   engine means operably connected to said pump means for supplying power to said pump means in performing a secondary work function at a speed near the idling speed of said engine means;   throttle control means governing the flow of fluid to the engine means to maintain its horsepower output at a level sufficient to operate the pump means while maintaining the speed of said engine means at a speed near its idling speed; and   means to maintain the flow rate from the pump means at a sufficiently low level to not exceed the capacity of the pump means or the auxiliary load when the engine speed is increased to a predetermined level in excess of its idling speed;   whereby the engine means operates in the low noise level region of speeds nears its idling speed or less when supplying power for the pump means in operating the variable volume and variable pressure load, and the pump means and auxiliary load are protected from use in excess of their capacity when the engine means is operating at increased speeds.   
     
     
       11. A noise reduction apparatus as defined in claim 10, including: a fluid reservoir in flow communication with the pump means and the variable load to provide a variable volume of hydraulic fluid for operation of the variable load.   
     
     
       12. A noise reduction apparatus as defined in claim 10 including means to vary the volume and pressure of the fluid discharge from the pump means in response to the demands of the hydraulic load. 
     
     
       13. A noise reduction apparatus as defined in claim 10, including: a variable displacement pump for supplying hydraulic fluid to the auxiliary load, and   means to control the displacement of the variable displacement pump in response to the demands of the auxiliary load.   
     
     
       14. A noise reduction apparatus as defined in claim 10 wherein the engine means operates at a speed of about 700 rpm. or less to about 1000 rpm. in performing its secondary work function. 
     
     
       15. A noise reduction apparatus for operating a variable volume and variable pressure auxiliary hydraulic load comprising: pump means;   engine means operable connected to the pump means for supplying power to the pump means in performing a secondary work function at speeds near the idling speed of the engine means;   a fluid reservoir in flow communication with the pump means and the auxiliary load to provide a variable volume of hydraulic fluid for operation of the variable load;   throttle control means governing the flow of fuel to the engine means to maintain the torque output of the engine means, even at low engine speeds at a level sufficient to operate the pump means under various loading conditions imposed by the variable load; and   means to maintain the flow rate of fluid to the variable load at or below a predetermined level dependent upon the particular capacity of the pump means.   
     
     
       16. A noise reduction apparatus as defined in cliam 15, including: a variable pressure and variable volume pump means, and   said throttle control means being actuated in response to the volume and pressure of fluid discharged by the pump means to the variable load.   
     
     
       17. The noise reduction apparatus of claim 16, including: means to vary the output pressure and volume of hydraulic fluid from the pump means in response to the demands of the variable load.   
     
     
       18. The noise reduction apparatus of claim 17 wherein the pump means includes a variable displacement pump whose output is controlled in response to the demands of the variable load. 
     
     
       19. In combination for reducing noise from an engine of a vehicle in driving an auxiliary mechanism disposed on the vehicle where the mechanism is auxiliary to the operation of the vehicle and provides a variable load during its operation, first means operable to provide for an operation of the auxiliary mechanism,   second means responsive to the operation of the first means for providing for the production of torque characteristics by the vehicle engine to obtain an engine speed approaching the idling speed of the engine,   third means responsive to the operation of the first means for producing a flow of hydraulic fluid with characteristics to obtain the operation of the auxiliary mechanism,   fourth means responsive to the flow of hydraulic fluid produced by the third means for providing for the introduction of the hydraulic fluid to the auxiliary mechanism to operate the auxiliary mechanism, and   fifth means for varying the operation of the second means in accordance with such variable load in the range of engine speed approaching the idling speed of the engine to provide variations in the torque characteristics of the engine in accordance with the variable load.   
     
     
       20. The combination as set forth in claim 19 wherein sixth means are responsive to the operation of the engine at a particular speed above idling to control the operation of the third means in producing the flow of hydraulic fluid.   
     
     
       21. The combination set forth in claim 20 wherein the third means include a reservoir for storing the hydraulic fluid to provide for the introduction of variable amounts of fluid at different times to the auxiliary mechanism in accordance with the variable load of the auxiliary mechanism. 
     
     
       22. In combination for reducing noise from an engine of a vehicle in driving an auxiliary mechanism disposed on the vehicle where the mechanism is auxiliary to the operation of the vehicle and provides a variable load during its operation, first means operable to provide for an operation of the auxiliary mechanism,   second means responsive to the operation of the first means for providing for the production of torque characteristics by the vehicle engine to obtain an engine speed near engine idling,   third means responsive to the operation of the first means for providing a flow of hydraulic fluid with characteristics to obtain the operation of the auxiliary mechanism,   fourth means responsive to variations in the load providing by the auxiliary mechanism at each instant to adjust the flow characteristics of the hydraulic fluid from the third means in accordance with such variations in the load,   fifth means responsive to the flow of hydraulic fluid from the third means for providing for the introduction of the hydraulic fluid to the auxiliary mechanism to obtain an operation of the auxiliary mechanism, and   sixth means for varying the production of torque characteristics by the vehicle engine in accordance to maintain the engine at a speed near idling.   
     
     
       23. The combination as set forth in claim 22 wherein the third means provides a flow of the hydraulic fluid with pressure and volume characteristics to obtain the operation of the auxiliary mechanism and the fourth means adjusts the pressure and volume characteristics of the hydraulic fluid from the third means in accordance with the variations in the load provided by the auxiliary mechanism and the sixth means varies the speed of the vehicle engine in accordance with the adjustments in the pressure and volume characteristics of the hydraulic fluid from the third means. 
     
     
       24. The combination as set forth in claim 22 wherein seventh means are resposive to the operation of the engine at a particular speed above idling to limit the operation of the third means in supplying the hydraulic fluid to the fourth means.   
     
     
       25. In combination for reducing noise, an engine for driving a vehicle,   an auxiliary mechanism disposed on the vehicle for providing an auxiliary operation distinct from the driving of the vehicle, the auxiliary mechanism being constructed to provide a variable load during its operation,   first means operable to initiate an operation of the auxiliary mechanism,   second means responsive to the operation of the first means for obtaining the production of torque characteristics from the engine to produce a speed near engine idling,   third means responsive to the operation of the vehicle engine for producing a flow of hydraulic fluid with characteristics dependent upon the speed of the engine,   fourth means responsive to the hydraulic fluid from the third means for providing for the introduction of the hydraulic fluid to the auxiliary mechanism to operate the auxiliary mechanism,   fifth means responsive to the variable load provided by the auxiliary mechanism for adjusting the flow characteristics of the hyraulic fluid from the third means in accordance with the variations in the load, and   sixth means for obtaining variations in the torque characteristics of the vehicle engine to maintain the engine at a speed near idling.   
     
     
       26. The combination set forth in claim 25 wherein the fourth means include a reservoir for storing the hydraulic fluid from the third means and for providing for the introduction of such hydraulic fluid to the auxiliary mechanism in accordance with the variable load from the auxiliary mechanism. 
     
     
       27. The combination set forth in claim 26, including: seventh means responsive to the operation of the vehicle engine at particular speeds above idling for limiting the introduction of the hydraulic fluid from the third means to the fourth means.   
     
     
       28. The combination set forth in claim 27 wherein the third means produces the flow of the hydraulic fluid with volume and pressure characteristics dependent upon the speed of the engine and the fifth means adjusts the volume and pressure characteristics of the hydraulic fluid from the third means in accordance with the variations in the load provided by the auxiliary mechanism and the sixth means varies the operation of the second means to adjust the torque characteristics of the engine in accordance with the adjustments in the volume and pressure characteristics of the hydraulic fluid from the third means.   
     
     
       29. In a system for reducing noise from a vehicle engine in driving an auxiliary mechanism disposed on the vehicle where the mechanism is auxiliary to the operation of the vehicle and provides a variable load during its operation and the vehicle engine produces torque characteristics providing for an engine speed approaching engine idling and the engine produces a flow of a hydraulic fluid with pressure and volume characteristics to obtain an operation of the auxiliary mechanism, first means responsive to the pressure characteristics of the hydraulic fluid for producing a first force representing such pressure characteristics,   second means responsive to the volume characteristics of the hydraulic fluid for producing a second force representing such volume characteristics,   third means having displaceable characteristics and responsive to the first and second forces to become displaced in accordance with such forces,   throttle means having adjustable characteristics for providing a control over the torque characteristics produced by the vehicle engine in accordance with the adjustments of the throttle means, and   fourth means responsive to the displacements of the third means and operatively coupled to the throttle means for adjusting the throttle means in accordance with the displacement of the third means to provide for variations in the torque characteristics of the vehicle engine in accordance with the displacements of the third means and to maintain the engine at a speed approaching engine idling.   
     
     
       30. In a system as set forth in claim 29, fifth means for biasing the third means against displacement in response to the first and second forces, and   sixth means including in the fifth means for providing variations in the adjustments imparted to the throttle means by the fourth means in response to the displacements of the third means.   
     
     
       31. In a system as set forth in claim 30, seventh means operatively coupled to the fourth means for limiting the adjustments provided in the throttle means in accordance with the displacements of the third means.   
     
     
       32. The combination set forth in claim 1 wherein fifth means are responsive to increases in fluid pressure above a particular value for limiting the rate at which fluid is supplied by the third means under pressure to the fourth means. 
     
     
       33. The combination set forth in claim 5 wherein fifth means are responsive to pressures above a particular value in the fluid for limiting the rate at which fluid is supplied from the third means to the fourth means.   
     
     
       34. A noise reduction apparatus as defined in claim 10 including means to vary the volume and pressure of the fluid discharge from the pump means. 
     
     
       35. The combination set forth in claim 19 wherein the fifth means are responsive to the variable load of the auxiliary mechanism for varying the operation of the second means in accordance with such variable load. 
     
     
       36. The combination set forth in claim 19 wherein the third means are responsive to engine speeds above a particular value for controlling the rate of flow of the hydraulic fluid. 
     
     
       37. The combination set forth in claim 24 wherein the sixth means are responsive to the adjustments in the flow characteristics of the hydraulic fluid from the third means and are operatively coupled to the second means for varying the production of torque characteristics by the vehicle engine in accordance with such adjustments to maintain the engine at a speed near idling. 
     
     
       38. The combination set forth in claim 26 wherein the third means are responsive to the pressures of the hydraulic fluid for controlling the rate at which the flow of the hydraulic fluid is produced. 
     
     
       39. The combination set forth in claim 38 wherein the sixth means are responsive to the adjustments in the flow characteristics of the hydraulic fluid from the third means and are operatively coupled to the second means for obtaining variations in the torque characteristics of the vehicle engine in accordance with such adjustments.