The invention combines the features of a supercharger, a turbocharger and turbo-compounding into one system, utilizing a hydraulic or mechanical continuously variable transmission to drive the turbocharger up to a specific speed or intake manifold pressure and then holding the ideal speed to keep it at the right boost pressure for the engine condition. The benefits of a supercharger, which is primarily good for high torque at low speed, and a turbocharger, which is usually only good for high horsepower at high speeds are merged. Once the exhaust energy begins to provide more work than it takes to drive the intake compressor, the invention recovers that excess energy and uses it to add torque to the crankshaft. As a result, the invention provides the benefits of low speed with high torque and the added value of high speed with higher horsepower or better fuel economy all from one system.

FIELD OF THE INVENTION

This invention pertains to turbochargers, and more particularly to hydraulically driven turbochargers.

BACKGROUND OF THE INVENTION

Conventional turbochargers are driven by waste exhaust heat and gases, which are forced through an exhaust turbine housing onto a turbine wheel. The turbine wheel is connected by a common turbo-shaft to a compressor wheel. As the exhaust gases hit the turbine wheel, both wheels rotate simultaneously. Rotation of the compressor wheel draws air in through a compressor housing, which forces compressed air into the engine cylinder to achieve improved engine performance and fuel efficiency. Turbochargers for variable speed/load applications are typically sized for maximum efficiency at torque peak speed in order to develop sufficient boost to reach peak torque. However, at lower speeds, the turbocharger produces inadequate boost for proper engine transient response. Conversely, the turbocharger produces too much boost at rated speed and load. As a result, a wastegate is often used, which allows the use of a smaller turbocharger to reduce lag while preventing it from spinning too quickly at high engine speeds.

The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate is used to control the boost pressure. If the pressure gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down. This wasted energy reduces overall engine efficiency but prevents damage to the turbocharger from over-speed and prevents damage to the engine from over boosting.

Industry has recognized the wasted energy and has made attempts to harness the wasted energy. For example, U.S. Pat. No. 6,553,764 discloses a turbocharger system that mechanically couples a first motor/generator to the turbo-shaft of the turbocharger system wherein the first motor/generator is coupled to a second motor/generator that is coupled to a flywheel. During periods of excess turbocharger boost, the turbo-shaft drives the first motor/generator as a generator to provide power to drive the second motor/generator as a motor and store energy in the flywheel. During periods of insufficient boost, the energy stored in the flywheel is used to drive the second motor/generator as a generator to drive the first motor/generator as a motor, which drives the turbo-shaft, to accelerate the turbo-shaft more quickly. While this system is more efficient than conventional systems, the use of a flywheel creates additional problems. These problems include the flywheel failing destructively and damaging other components as it breaks apart into shrapnel-sized pieces, added weight to contain the flywheel, decreased stability during turns, increased control complexity to counter the forces generated by the flywheel, etc.

Another approach is illustrated in U.S. Pat. No. 5,113,658 that operates during periods of insufficient boost uses a hydraulic assist turbine mounted on the turbo-shaft between the compressor and turbine. During operation when the turbocharger does not provide sufficient boost, pressurized hydraulic fluid is supplied as high energy jets to the hydraulic assist turbine for rotating the hydraulic assist turbine, which in turn, drives the turbo-shaft. At periods of sufficient boost and excess boost, pressurized hydraulic fluid is not supplied to the hydraulic assist turbine. While this approach is more efficient than conventional turbocharger systems, this approach does not solve the problem of harnessing the wasted energy during periods of excess boost.

Another approach is illustrated in U.S. Pat. No. 6,343,473. In this approach, a supercharger is put in series with a turbocharger. During operation when the turbocharger does not provide sufficient boost, the supercharger is used to provide compressed air to the turbocharger compressor. At operational points where there would normally be excessive boost, the amount of air provided to pressurize the inlet is reduced by diverting the air flow, thereby reducing the amount of compressed air fed to the turbocharger compressor inlet. The problem with this approach is that the turbocharger is undersized and smaller than normal due to the supercharger providing compressed air to the turbocharger compressor. Should the supercharger fail since it is in series with the turbocharger, the turbocharger on its own is insufficient to provide the low speed torque required for starting and accelerating performance.

A further approach is illustrated in U.S. Pat. No. 5,729,978. In this approach, a turbocharger is used with a mechanical step-up transmission connected to the turbo-shaft to increase the torque during low speed operation. The step-up transmission includes a step-up gear (i.e., a two-stage change-speed gearbox) and a controllable hydrostatic coupling. To achieve shorter response times during transient operation, the hydrostatic coupling is locked up by a mechanical or electro mechanical clutch. The system decouples the exhaust gas turbine from the compressor at low rotational speeds so that the mechanical gearbox only has to drive the compressor. At higher speeds, the turbine is accelerated by exhaust gas flow and at a specified speed, it is coupled onto the turbocharger shaft by the clutch. The problems introduced with this system include the use of further components such as the step-up gear and the hydrostatic coupling, which reduces overall reliability. In the event that the hydrostatic coupling fails, the turbocharger operation may fail.

What is still needed is a system the increases efficiency that does not have the above-mentioned problems. The invention provides such a system. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

BRIEF SUMMARY OF THE INVENTION

The invention combines the features of a supercharger and a turbocharger utilizing a hydraulic pump to drive the turbocharger up to a specific speed or intake manifold pressure and then hold back the turbocharger to keep it at the right speed for the engine condition. The invention merges the benefits of a supercharger, which is primarily good for high torque at low speed, and a turbocharger, which is usually only good for high horsepower at high speeds. Once the exhaust energy begins to provide more work than it takes to drive the intake compressor, the invention recovers that excess energy and puts it to work turning the crankshaft. As a result, the invention provides both the benefits of low speed with high torque and the added value of high speed with high horsepower all from one system. The power available from an engine system with a super-turbocharger is greater than that of a turbocharged engine due to the elimination of the wastegate, the larger overall size of the turbocharger, vanes that make the compressor and turbine more efficient, and the ability of the system to hold the turbocharger at an optimum speed.

The invention provides a power take-off mechanism on the turbo-shaft of a turbocharger. The power take-off mechanism is connected to a variable speed transmission. The transmission can be in the form of a hydraulic motor/pump that is hydraulically connected to a variable displacement motor/pump such as a swashplate pump that is operatively connected to the crankshaft of the engine or it can be a mechanical continuously variable transmission like that used in some automobiles.

During engine operating conditions in which the turbocharger produces more energy than required for operation, the mechanism diverts the excess energy and drives the transmission, which in turn drives the crankshaft with more torque.

During engine operating conditions in which the turbocharger is incapable of meeting the boost demands of the engine (such as low speed high torque operation), the variable ratio transmission is driven, which results in the acceleration of the mechanism being driven, thereby increasing the speed of the turbo-shaft. As a result, the turbocharger delivers more pressure and airflow to the intake manifold of the engine to meet the boost demands.

The power take-off mechanism is in the form of a gear train such as a planetary gear system with a reduction gear or a speed-summing differential. The planetary gear system has three planetary gears within a stationary gear connected to the turbo-shaft. The three planetary gears rotate around outer ring gear as the gear connected to the turbo-shaft rotates with the turbo-shaft. Attached to the three planetary gears is an output gear with its gear diameter slightly larger than the super-turbocharger shaft. The output gear of the planetary gear set is in a gear mesh relation with to two equal size idler gears on either side of the gear attached to the three planetary gears. The two idler gears are connected to a reduction gear that takes the output of the two idler gears and feeds that to the hydraulic pump/motor. The speed-summing differential is used for very large engines where a purely hydraulic system could not handle the power requirements. The differential is connected to the hydraulic pump/motor. In a preferred embodiment, the hydraulic pump/motor is a variable displacement hydraulic pump/motor such as a swashplate pump that can also function as hydraulic motors depending on the angle of the swashplate.

DETAILED DESCRIPTION OF THE INVENTION

Turbocompounding is a way to harness excess exhaust energy that is not used by the turbine of the turbocharger. This is achieved by adding a second larger turbine attached to a transmission which is then attached to the output shaft of the engine. Turbocompounding can improve fuel economy by as much as 5%. This invention provide the best of both turbocompounding and supercharging all in one device. The invention provides a system that reduces turbocharger lag and harnesses excess exhaust energy from the turbocharger. The invention utilizes relatively inexpensive and commercially available components. The overall system cost of the system in accordance with the invention is believed to be equal to or less then that of a supercharger system and only slightly more expensive than a turbocharger system.

The invention combines the features of a supercharger and a turbocharger, utilizing a hydraulic pump to drive the turbocharger up to a specific speed or intake manifold pressure and then hold back the turbocharger to keep it at the right speed for the engine condition. Once the exhaust energy provides more work than it takes to drive the intake compressor the invention recovers that excess energy and puts it to work turning the crankshaft. As a result, the invention provides both the benefits of low speed with high torque and the added value of high speed with high horsepower all from one system. The invention merges the benefits of a supercharger, which is primarily good for high torque at low speed, and a turbocharger, which is usually only good for high horsepower at high speeds. Neither one are good at both at the same time.

Turning to the drawings, wherein like reference numerals refer to like elements, the invention is illustrated as being implemented in a suitable environment. With respect toFIG. 1, the exhaust gas from engine20travels through the turbocharger turbine22causing the turbine22to spin turbo-shaft24. The rotation of turbo-shaft24rotates turbocharger compressor26and planetary gear train28. The compressor26compresses inlet air, which is fed through optional cooler30and into the engine cylinders (not shown). The optional cooler30is an air cooler that cools compressed air after the compressor26to deliver cooler air to the engine. The planetary gear train28as discussed below is used to both drive the turbo-shaft24during low engine load operation and remove excess energy during high engine load operation. The wastegate that is part of traditional turbochargers is no longer needed on the exhaust side of the turbocharger. As will be explained below, a boost pressure control valve32is required on the intake side of the turbocharger to regulate pressure so that the intake system does not get too high for the engine to handle. In the description that follows, the term super-turbocharger refers to the turbocharger (turbine22, turbo-shaft24, and compressor26) and gear train28.

Turning now toFIGS. 2 and 3, the invention is shown in more detail. One of the key features of the invention is that the driving power that is provided from the crankshaft34needs to be delivered in a variable speed between the crankshaft of the engine and the super-turbocharger. Once the connection is made between the crankshaft34and the super-turbocharger it is possible to put energy into the super-turbocharger to spin it up to an appropriate speed level. Once the turbocharger has generated excess energy on the turbine side22to overcome the power required to perform the task of compressing the air on the compressor side26, additional energy is delivered back from the super-turbocharger to the crankshaft34. This recovered energy generates excess power that would normally be wasted by the exhaust wastegate in a typical turbocharger. The energy recovered to the crankshaft can improve fuel economy and the peak horsepower of the engine system. It combines the excess energy from the turbine as well as the energy from the pistons36, and delivers all of that to the transmission.

The super-turbocharger removes power from and adds power to the turbo-shaft24via the planetary gear reduction28through a speed reduction mechanism comprising planetary gears36,38feeding a hydraulic gear motor/pump40. The gear motor40is fed from a swashplate pump42attached to the crankshaft34. The swashplate pump42has a variable flow output based on the angle of the swashplate. Hydraulic energy would be put into the super-turbocharger at low speed via hydraulic circuit44, the motor/pump40and planetary gears36,38and gear reduction28. The hydraulic circuit44includes hydraulic lines46,48. The hydraulic motor/pump40turns into a hydraulic pump at high speed and pushes the swashplate pump42at high speeds thereby returning energy back to the crankshaft34in the same closed hydraulic circuit.

The hydraulic circuit44is fed by engine oil pressure through check valves50,52into each side of the system so that the hydraulic lines46,48in the closed loop system will always maintain a positive pressure, at least as high as in the oil pressure lines within the engine. This approach provides a replenishment of hydraulic fluid based on the fact that there will be some leakage in the shaft between the hydraulic motor40and the gear reduction28within the super-turbocharger, as well some potential leakage of the hydraulic pressure within the swashplate pump42. Note that the super-turbocharger may require an oil cooler54to prevent over heating of the engine oil that is used for hydraulic oil. The engine oil may also be used for lubrication within the super-turbocharger housing since it is already present. Alternatively, a separate hydraulic system can be used.

As previously indicated, the wastegate that is normally associated with turbochargers is no longer on the exhaust side of the turbocharger system. However, a boost pressure control valve (i.e., regulator32) is required on the intake side of the super-turbocharger in parallel with the turbocharger compressor26. The reason for this is that the hydraulic system prevents the super-turbocharger from overspeeding or going too fast (i.e., from going above an upper speed limit) from too much exhaust energy. To accomplish this, the intake requires pressure regulation so that the intake system does not reach a pressure that is too high for the engine. The regulator32will open and at that point the excess energy from the turbine22will pressurize the pump40within the super-turbocharger. The pump40will feed the excess energy back to the swashplate pump42, now being driven as a motor. The swashplate pump, in turn, drives the crankshaft34of the engine, thereby creating additional horsepower that would normally be wasted by dumping exhaust gas through a wastegate.

Note that the planetary gear reduction28provides one of the best methods of taking power off of the turbo-shaft24that spins at very high speed, typically on the order of between 50,000 and 100,000 rpm. The planetary gear reduction28has two or more gears around the shaft provide a high ratio gear reduction from the high-speed shaft. The typical three gears that rotate around the turbo-shaft24provide an even power take-off in three directions where the directional vectors of the three gears cancel each other out and provide no directional force to push the turbo-shaft24off center within its bearings. As a result, the design eliminates any power take-off vector that would have an adverse affect on the position of the high-speed shaft within the bearings of the super-turbocharger. The planetary gear reduction feeds a secondary gear reduction that feeds the hydraulic pump. This whole mechanism is designed to be within the length of a typical turbocharger bearing housing because it is undesirable that a turbocharger shaft be extended much longer in length than they already are due to their high rpm. The planetary configuration of gear reduction also improves the reliability of the power input and power take-off of the super-turbocharger system.

The design of the super-turbocharger of the invention is different from a conventional turbocharger. There are two major differences that increase the energy potential to be returned to the crankshaft34. The first difference is that there are permanent vanes on both the compressor and turbine side of the housings. Vanes on the intake side normally raise the peak efficiency at the expense of narrowing the speed range of the compressor in conventional turbochargers, which significantly limits the operational scenarios where the vanes could be used with conventional turbochargers. Permanent vanes on the exhaust side normally raise the peak pressure too high and over-speed the turbine in conventional turbochargers. However, the present invention controls the rotational speed of the super-turbocharger. As a result, vanes on both the intake side and exhaust side can be used and the invention makes use of this greater amount of available power.

The second difference is that slower speed, larger sized exhaust turbines can be used. Traditionally, higher speed, smaller sized turbochargers are used to reduce turbo lag. A slower speed, larger size turbine can be used because turbo lag will not be a problem due to the hydraulic boost spooling the super-turbocharger up to speed. The use of a larger turbine provides additional peak boost potential and additional energy recovery once boost is limited on the intake side.

Now that the overall system has been described, the control of the system shall be described. In the description that follows, a separate controller shall be used. It is recognized by those skilled in the art that the controller may also be part of another controller such as the engine management system. The use of a separate electronic device allows the system to be provided as an add-on system to any vehicle where the owner desires more horsepower potential than is available from either a supercharger or turbocharger.

The controller60requires a speed sensor62on the super-turbocharger at some point in the gear reduction system28for controlling the speed of the super-turbocharger. With knowledge of the ideal and optimum speed of the super-turbocharger, the controller60uses the speed at either the highest efficiency or highest boost pressure rpm of the turbocharger as the control point for the turbocharger speed. The controller60also controls regulator32to have electronic boost control over the intake side. The other input the controller60uses is the throttle position64to determine power delivery requests of the driver. With throttle position64, the speed of the super-turbocharger can be controlled to be at its optimum speed all the time while being sensitive to the power delivery requests of the driver.

The controller60controls the lever66on the swashplate pump42via motor or actuator68to control the angle of the swashplate. The angle of the swashplate varies the speed of the super-turbocharger during various modes of operation. When the engine is at idle speed, the controller60adjusts the control level to be at the minimum amount of angle for the swashplate. In one embodiment, the swashplate pump42will spin the super-turbocharger to some specific rpm well below the point where it creates any significant intake boost pressure when the control level is set to the minimum amount or angle. For example, with the engine running at idle of say 1,000 rpm, the super-turbocharger would be running at its idle speed of approximately 5,000 rpm.

Once the throttle70(represented in the figure as a throttle pedal) is depressed signifying that the driver requires more power, the super-turbocharger is sped up by the changing the angle of the swashplate pump42via motor68. Changing the angle of the swashplate pump42from its minimum angle increases the hydraulic pressure to the gear motor40, thereby increasing the speed of the turbo-shaft24. Pumping a significant hydraulic pressure to the gear motor40will rapidly accelerate the super-turbocharger up into the speed range where it produces significant pressure in the intake channel (i.e., through compressor26) making more power from the greater charge density in the cylinders72.

In one embodiment, the swashplate pump lever66is moved all the way in the maximum position until the point where the super-turbocharger reaches its optimum speed. At the maximum position, the hydraulic circuit44is at its highest pressure level, which causes hydraulic pump40to rotate faster, thereby accelerating the turbo-shaft24at a faster rate. Once the optimum speed is reached, the controller60commands the swashplate pump lever66to be pulled back to an interim position where the speed of the super-turbocharger is maintained at its optimum speed. As the engine continues to increase power output and produce more exhaust heat at higher speeds, the controller60commands the intake regulator32to open, thereby maintaining the appropriate level of pressure in the intake system.

The unused compressor energy requires the hydraulic system44to hold back the excess energy from the turbine22to maintain speed. The turbine22will keep putting additional energy into the hydraulic system44via planetary gear train28and hydraulic pump40and “push” the energy down to the swashplate pump42and on to the crankshaft34. As the crankshaft speed increases, the swashplate pump42is controlled to maintain the speed of the super-turbocharger at the desired level.

In one embodiment, a hydraulic brake80is added to the system. The controller60controls the hydraulic brake80to prevent the over speeding of the engine by preventing the turbine22from putting excess energy from the exhaust back to the crankshaft34as described above. The excess energy could over-speed the crankshaft34when there is no load such as a shift between gears, or there is no load because of a decelerating condition such as the clutch of the engine being disengaged. With permanent vanes in the turbine housing as previously described, under deceleration there may be far too much energy generated from the turbine blades. The addition of a hydraulic brake provides the capability to better control the excess energy from the exhaust heat whenever the driver removes his foot from the throttle. While other techniques can be used, the hydraulic brake allows a deceleration condition to be managed without another device. This brake will also insure that there is some level of engine braking effect during deceleration conditions.

In a further embodiment, an intercooler30is used. The use of an intercooler30provides a major advantage for the system as a compressor increases the heat in the intake system and increases the chances of detonation from hot and high-pressure intake manifold air. The intercooler30can be an air-to-air intercooler. Alternatively, the intercooler30can be an air-to-water intercooler where a water radiator is used and the cooling water is used in the intercooler30to cool the intake charge in a similar way as the air-to-air intercooler. The benefit of a water-based intercooler is there is a shorter path than air-to-air intercoolers as they are smaller then air-to-air intercoolers. Therefore, there is a shorter path between the compressor26and the cylinder72. The other added benefit of a water-cooled intercooler is its ability to be used as a heater by being able to divert the cool water away from the intercooler and put hot engine water into the intercooler as an alternative. The ability to variably control the charge cooling temperature provides a better control of a homogeneous charge compression ignition engine.

Turning now toFIGS. 4-6, in one embodiment, the planetary gear speed reduction power take-off28from the turbo-shaft24has three planetary gears90within a stationary gear92connected to the turbo-shaft24. The three planetary gears90rotate around outer ring gear94as gear92rotates with the turbo-shaft24. The outer ring gear94is connected to the housing. Attached to the three planetary gears90is an output gear98with its gear diameter slightly larger than the super-turbocharger shaft94. The output gear98of the planetary gear set is in gear mesh relation to two equal size idler gears100on either side of the gear98attached to the three planetary gears. The two idler gears100are connected to the large output gear38that takes the output of the two idler gears100and feeds that to the hydraulic drive motor40. The combination of the rotating planetary three-gear set attached to the output gear98to the two idler gears100insures that all forces are balanced in each direction. As a result, any driving force on the super-turbocharger shaft24should be equalized. It is critical to long term reliability that there be no up or down or side-to-side force that would push the high-speed turbocharger shaft24out of alignment with its bearings.

The hydraulic drive motor40would just be two more gears102,104with gear102attached to the main speed reduction gear38. The gears102,104are sized appropriately for the correct flow of hydraulic fluid. The hydraulic drive motor40is designed to match the ideal turbine speed and the hydraulic power required from the swashplate pump42and is also designed such that the pressure in the hydraulic system should not exceed design level.

During operation when there is insufficient boost to spin the turbine22and compressor26, the hydraulic circuit44flows through hydraulic pump40and causes gears102and104to rotate. The rotation of gear102rotates reduction gear38, which in turn rotates idler gears100. The rotation of idler gears100rotates output gear98, which in turn rotates the three planetary gears90. The rotation of the planetary gears90results in the rotation of gear92, thereby rotating turbo-shaft24(and the turbine22and compressor26). During periods of excessive boost, the drive pressure reverses direction where rotation of turbo-shaft24rotates gear92, which rotates planetary gears92and output gear98, which in turn rotates idler gears100, which in turn rotates reduction gear38, which in turn rotates hydraulic pump40. The rotational direction of all the components stays the same.

It is noted that on very large engines the cost and size of the turbocharger system and the efficiency required of the power delivery may be more significant than a purely hydraulic system can manage. The invention uses a speed-summing differential between the turbocharger and the engine for these very large engines. Turning now toFIG. 7, the invention replaces the hydraulic transmision with a speed-summing differential110. A variable displacement hydraulic pump114that is driven by the engine acts on the hydraulic motor112as an external hydraulic source in either direction such that the variable displacement pump114controls the speed and direction of motor112to vary the relative speed between the engine and the turbo-shaft. Note that variable displacement pump114is operably connected to crankshaft34. In a preferred embodiment, the variable displacement pump114is a swashplate pump that can put out hydraulic pressure in either direction (e.g., variable displacement pump114may be swashplate pump42).

In the description that follows, the term super-turbocharger refers to the turbocharger (turbine22, turbo-shaft24, and compressor26) and the internal gear reduction. The speed-summing differential110requires the variable displacement pump114to control the speed and direction of hydraulic motor112. During operation, the controller60senses engine speed and load, turbo-shaft speed, and the super-turbocharger boost pressure. Based on these factors, the controller60manages the flow of power into and out of the speed-summing differential110by controlling the variable displacement hydraulic pump114by adjusting its swashplate displacement.

During operating conditions in which the turbine side of the super-turbocharger produces more energy than required for boost, the speed-summing differential110diverts the excess energy to the crankshaft of the engine72by direct mechanical connection. The proper turbo-shaft24speed is maintained by the controller60by adjusting the hydraulic flow of the variable displacement motor/pump114to drive pump/motor112at a speed that sets the speed-summing differential to the correct ratio. As a result, the crankshaft34rotates with more torque and the engine drive train absorbs the excess power, thereby reducing fuel demand.

During operating modes where the compressor portion of the super-turbocharger is incapable of meeting the boost demands of the engine (e.g., at low speeds), the controller60adjusts the swashplate angle of pump114such that the crankshaft drives variable displacement motor/pump114as a pump. The motor/pump112operates as a motor and drives the speed-summing differential110, changing the gear ratio between the crankshaft and the turbo shaft, which drives turbo-shaft24to rotate faster than it would have been driven by the exhaust gas turbine alone. As a result, the super-turbocharger delivers sufficient air to the intake manifold to increase the boost to the engine.

As can be seen from the foregoing, a super-turbocharger has been presented that is economical to make and that overcomes the problems in the art. The gear train of the invention (planetary gear train28and speed-summing differential110) can operate at high temperatures and high speeds. The gear train is balanced such that it does not push the turbo-shaft off of its center of spin when power is applied or removed from the turbo-shaft. The high mechanical efficiency of the gear trains and hydraulic energy conversion increases efficiency of the system. Additionally, the sizing of the compressor and turbine can be decoupled since the invention provides flexibility in either consuming (and utilizing) excess turbine energy or creating additional compression energy otherwise not available from the exhaust gas driving the turbine. Furthermore, more exhaust energy is extracted from the turbocharger, which lowers exhaust temperatures and reduces EGR cooling load in low-pressure EGR systems. The added performance provided by the invention may eliminate the need for variable geometry turbochargers or series turbochargers presently used on truck engines.

One of the main benefits to the system described above is that the swashplate pump42, hydraulic gear motor40, and variable displacement pumps112,114are relatively inexpensive and are commercially readily available in the market place and are combined with the inherent lower cost of a turbocharger compared to a supercharger. The overall system cost of the invention should be equal or less then that of a supercharger system and only slightly more expensive than a turbocharger system. It is estimated that the invention provides a five to seven percent increase in fuel efficiency and a five to ten percent increase in peak power when compared to a conventional turbocharged engine system.