Abstract:
An axial engine includes a cam assembly housing moveable away from a cylinder head to reduce a compression ratio during conditions giving rise to detonation and movable towards the cylinder head to raise the compression ratio when operation allows the higher compression ratio. Piston rod ends ride in counter rotating slots balancing lateral forces on the piston rods. Piston dwell at Top Dead Center (TDC) provides for constant volume combustion and extended piston travel during the power stroke allows for over-expansion. Rotary valves improve volumetric efficiency and water injection supports increased compression ratio leading to improved thermodynamic efficiency.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority of U.S. Provisional Patent Application Ser. No. 62/123,710 filed Nov. 11, 2014, which application is incorporated in its entirety herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to internal combustion engines and in particular to a crankless over-expanded variable-compression engine with regenerative internal-cooling using constant-volume combustion and rotary-valves. 
     The thermodynamic efficiency of an internal combustion engine is strongly related to a compression ratio of the engine. Typical automotive engines have compression ratios of 8.5:1 to 12:1 for street driven automobiles, and sometimes higher for racing engines using special racing fuel in racing conditions. Higher compression ratios for street driven automobiles would increase the thermodynamic efficiency, and thus the gas mileage, but also results in detonation in the combustion chambers of the engines resulting in damage and eventual failure. 
     The energy distribution chart for a conventional four stroke, Spark Ignition (SI) engine, is about 30 percent usable work, 35 percent into the cooling system (which includes heat generated by friction between moving parts), and 35 percent goes out the exhaust. The first 30 percent corresponds to the engine&#39;s overall efficiency, and based on this value, one may assume that it&#39;s running at Wide Open Throttle (WOT). Internal Combustion Engines (ICE) are theoretically less efficient at partial throttle settings then when running wide open due to parasitic losses, etc. 
     Thermodynamic theory suggests, that a heat engine of this type may achieve an efficiency factor of about 60-65 percent at best, but known engines are far from that, and 70 percent of the energy available in a gallon of gasoline is wasted. Automobile manufacturers continue their efforts to improve the situation, and they have been succeeding, as the average miles per gallon has been steadily rising. Improvements include reducing vehicle weight, better aerodynamics, operating hybrid engines at their most efficient speeds, turbo chargers to recapture some of the exhaust&#39;s wasted heat, and engines running with higher compression ratios and therefore, more thermodynamically efficient. However, these small incremental changes have become few and far between and more costly. 
     Known four stroke, spark ignited engine include a series of pistons, in a line, move up and down in cylinder sleeves capped by a header. The pistons connect to a crankshaft, via connecting rods, which controls the piston&#39;s motion (stroke). In a first stroke (intake), the crankshaft pulls the piston down, from Top Dead Center (TDC) creating a vacuum inside the corresponding cylinder, and with the intake valve open, draws an Air/Fuel Mixture (AFM) into the cylinder. At Bottom Dead Center (BDC) the cylinder is at its largest volume and the intake valve closes trapping in the ingested AFM. Next, the piston starts up on the second stroke (compression) back to TDC. The compression stroke compresses and heats the AFM according to the physical parameters of the engine. Since the piston&#39;s up and down strokes are controlled by the crankshaft, they are all exactly the same length, and the compression ratio is set as a fixed value during the engine&#39;s design phase. Compressing the AFM takes a large amount of energy which reduces the power output. To get the maximum amount of energy out of known engines, the AFM half burn must be completed by about 10 degrees of crankshaft rotation after TDC and ignition must take place from 10 to 60 degrees before TDC because the fuel burn takes 20 to 70 degrees of crankshaft rotation to complete. So the AFM is burning before TDC and is getting hotter and pressure in the cylinder is rising over and above that caused by the compression process itself, which increases the negative work. 
     The third stroke (expansion or power) begins after TDC of the compression stroke. Gas engines are limited in the compression ratio because of a phenomenon called detonation or knock. Detonation occurs because the compression ratio is so high and the combustion chamber wall so hot that the self-ignition temperature of the AFM is reached causing combustion. These are untimed events that often seriously damage the engine. The fourth and final stroke is the exhaust stroke. During the exhaust stroke, upward movement of the piston pushes engine exhaust out through the open exhaust valve. The power stroke is the only stroke which produces mechanical energy, and energy remaining in the cylinder at the end of the power stroke is lost as heat into the exhaust gases. 
     In summary, most of the energy in a gallon of gasoline is wasted. Even an ideal known SI engine will only recover another third of the energy in the gasoline burned by the engine, two revolutions of the crankshaft are required to produce ½ revolution of power, the piston strokes (all of them) are of equal and fixed length, wasting energy remaining in the cylinder at the end of the power stroke, and higher compression ratios which provide greater thermodynamic efficiency are not possible due to detonation. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention addresses the above and other needs by providing an axial engine which includes a cam assembly housing moveable away from a cylinder head to reduce a compression ratio during conditions giving rise to detonation and movable towards the cylinder head to raise the compression ratio when operation allows the higher compression ratio. Piston rod ends ride in counter rotating slots balancing lateral forces on the piston rods. 
     In accordance with one aspect of the invention, there is provided an axial engine having counter rotating inner and outer barrel type cams, the inner cam coaxial with and inside the outer cam. The inner and outer cams counter rotate at the same angular speed and are moveable parallel to an engine shaft towards and away from a cylinder head, and the inner and outer cams are radially spaced apart providing room for piston connecting rods. The inner cam and outer cam include inner and outer cam tracks respectively. The cam tracks comprise two walls and a floor, forming a channel for guiding connecting rod cam followers, and the connecting rods include wings on both sides of the cam followers to align the cam followers with the channels and to absorb shear forces imparted to the connecting rod by the counter-rotating cams. The inner cam tracks comprise two diverging-converging, generally sinusoidal channels on the outside surface of the inner cam, one having a greater amplitude than the other, but converging at peaks at 0 deg, 180 degrees and again at 360 degrees. The outer cam track comprises a single generally sinusoidal channel on an inside surface of the outer cam with an intake and compression portion having a lesser amplitude than a power and exhaust portion. The cam tracks face each other and a single cam follower engages both the inner and outer cam tracks simultaneously. Each node includes a near sinusoidal segment of the cam tracks, and corresponding portions of the inner and outer cam tracks are adjacent, allowing the cam followers to simultaneously engage both the inner and the outer cam tracks at all times. 
     In accordance with another aspect of the invention, the pistons and connecting rods are mounted around an output shaft and move parallel to the output shaft. The parallel configuration results in the piston&#39;s components moving in a parallel, linear and reciprocal motion, minimizing piston side loads, friction and vibration. 
     In accordance with yet another aspect of the invention, there is provided an axial engine providing isochoric (constant volume) combustion. Due to piston dwell at Top Dead Center (TDC), the combustion occurs in a fixed volume during most of the combustion duration. The fixed volume eliminates negative work caused by spark advance in convention Spark Ignition (SI) engines, and also increases combustion efficiency. The dwell at TDC is preferably 10 degrees of Engine Shaft Angle (ESA) but may vary between 0 and 30 degrees of ESA. 
     In accordance with still another aspect of the invention, there is provided an axial engine providing a variable compression ratio having improved thermodynamic efficiency compared to known engines. The piston and cam assembly is movable towards and away from the cylinder head thus changing the combustion chamber volume at TDC. The variable compression ratio allows the compression ratio to be varied, for example, between 8:1 and 20:1 and anywhere in between during engine operation. The variable compression ratio allows the compression ratio to be increased under light loads providing higher thermodynamic efficiency at the light loads. 
     In accordance with another aspect of the invention, there is provided an axial engine having an over expansion power stroke. The cam tracks descend farther on the power stroke than on the intake stroke. As result, residual energy residing in the high pressure hot gases inside the cylinder at the end of the power stroke, and normally exhausted, may be used to provide additional shaft work. An example of the expansion and exhaust strokes ratio to the intake and compression strokes is 1.7:1. 
     In accordance with yet another aspect of the invention, there is provided an axial engine including rotary valves. A modified Bishop rotary valve is used in lieu of the standard poppets. These Bishop rotary valves provide improved volumetric efficiency, optimized turbulence, and much faster opening and closing times. Also, the rotary valve allows much higher compression ratios than those allowed by poppet valves during valve overlap. The Bishop rotary valve design in described in U.S. Pat. No. 4,852,532 issued Aug. 1, 1989, incorporated herein by reference in its entirety. 
     In accordance with another aspect of the invention, there is provided an axial engine having up to three direct (in-cylinder) water injection cycles and a further possible extra injection into the intake manifold for each cylinder during each four stroke events. A first water injection occurs during compression wherein the water is used to cool the air/fuel mixture. This reduces compression work and allows an increase in the compression ratio. A second water injection takes place during combustion (start of piston dwell at TDC) and is used to cool the combustion process itself. This eliminates the need for Exhaust Gas Recirculation (EGR) and enables higher compression ratios. A third water injection (onto the various walls) takes place during expansion (after combustion occurs) and provides for the internal cooling of the combustion chamber, piston and the rotary valves. This allows for what we call internal regeneration, where part of the heat that would be lost to the engine walls is retrieved to produce work by the expansion of the liquid water into vapor. Also the wall temperature inside the engine will be decreased and controlled by the water fuel ratio and water injection duration. This eliminates hot spots reducing the onset of knock. 
     The water injection into the intake manifold reduces air temperature and increases its density, increasing volumetric efficiency. The net effect of the total water injection is an increase in fuel efficiency, through compression work reduction, compression ratio increase and regeneration of the heat transferred to the walls. The interior of the combustion walls should be maintained between 250 to 300 degrees Centigrade to provide adequate vapor pressure for the regenerative cooling. The calculated water to fuel ratio is preferably 4.3:1 at idle and 1.4:1 at Wide Open Throttle (WOT) but may vary from 0:1 to 7:1. While this is an open loop process (the water is lost via the exhaust) a substantial amount, up to 66% of the total water in the exhaust, may be recovered and recycled via, for example, a capillary condensation pore process as described in U.S. Pat. No. 8,511,072, issued Aug. 20, 2013 and herein incorporated by reference in its entirety. 
     In accordance with the combined aspects of the invention, there is provided an axial engine having improved thermodynamic efficiency. A thermodynamic analysis using Converge CFD and MATLAB® SIMULINK® engine models predict an increase in fuel efficiency ranging from 50 percent to 72 percent, achieving a 45 percent mark in overall efficiency. In particular, compared to a conventional SI engine with a 30 percent efficiency at WOT, the axial engine according to the present invention may reach an efficiency of 45 percent, which is a 50 percent improvement, the improvement provided given by water injection (21 percent), Constant Volume Combustion (CVC) (7 percent), over-expansion (12 percent), improved combustion/compression ratio (5 percent), and reduced friction losses (5 percent). Further, compared to a conventional SI engine with a 25 percent efficiency at partial load, the axial engine according to the present invention may reach an efficiency of 43 percent, which is a 72 percent improvement, given by water injection (17 percent), CVC (13 percent), over-expansion (7 percent), improved combustion/compression ratio (27 percent), and reduced friction losses (8 percent). Further, compared to a conventional SI engine, which has a 180 degree power stroke for 720 degrees of output shaft revolution, the axial engine has a 90 degree power stroke for 90 degrees of output shaft revolution. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1  is a top and side perspective view of an axial engine according to the present invention. 
         FIG. 2  is a bottom and side perspective view of the axial engine according to the present invention. 
         FIG. 3A  is a first side view of the axial engine according to the present invention. 
         FIG. 3B  is a second side view of the axial engine according to the present invention. 
         FIG. 4  is a perspective view of an inner cam of the axial engine according to the present invention. 
         FIG. 5  is a perspective view of an outer cam of the axial engine according to the present invention. 
         FIG. 6  shows pistons and connecting rods engaging the inner cam of the axial engine according to the present invention. 
         FIG. 7  shows inner and outer cam gears of the axial engine according to the present invention. 
         FIG. 8A  shows an inner cam channel of the axial engine according to the present invention. 
         FIG. 8B  shows an outer cam channel of the axial engine according to the present invention. 
         FIG. 9  shows a first cross-sectional view of a cam assembly and block of the axial engine according to the present invention. 
         FIG. 10  shows a second cross-sectional view of a cam assembly and block of the axial engine according to the present invention taken along line  10 - 10  of  FIG. 9 . 
         FIG. 11  shows a top perspective view of a piston of the axial engine according to the present invention. 
         FIG. 12  shows a first bottom perspective view of the piston of the axial engine according to the present invention. 
         FIG. 13  shows a second bottom perspective view of the piston of the axial engine according to the present invention. 
         FIG. 14A  shows a first side view of the piston of the axial engine according to the present invention. 
         FIG. 14B  shows a second side view of the piston of the axial engine according to the present invention. 
         FIG. 15  shows a top perspective view of a cylinder head of the axial engine according to the present invention. 
         FIG. 16  shows a bottom perspective view of the cylinder head of the axial engine according to the present invention. 
         FIG. 17A  shows a first side view of the cylinder head of the axial engine according to the present invention. 
         FIG. 17B  shows a second side view of the cylinder head of the axial engine according to the present invention. 
         FIG. 18  shows a pair of rotary valves of the axial engine according to the present invention. 
         FIG. 19  shows an example of drive structure for the rotary valves according to the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
     A top and side perspective view of an axial engine  10  according to the present invention is shown in  FIG. 1 , a bottom and side perspective view of the axial engine  10  is shown in  FIG. 2 , a first side view of the axial engine  10  is shown in  FIG. 3A , and a second side view of the axial engine  10  is shown in  FIG. 3B . The axial engine  10  includes a head  14  fixed to a cylinder block  56 . An engine housing  12  is fixed to the cylinder block  56  opposite to the head  14 . The cylinder head  14  includes air intakes  16 , exhaust headers  18 , spark plugs  20 , and a rotary valve drive gear  24 . Other preferred elements of the head  14  are shown in  FIGS. 15-18 . Servo motors  26  below the engine housing  12  are provided to move a cam assembly  38  (see  FIG. 9 ) towards and away from the cylinder head  14 . Such movement of the cam assembly  38  further moves the piston  50  towards and away from the cylinder head  14  thus varying the Compression Ratio (CR). 
     The CR is the ratio of the volume of the cylinder at Bottom Dead Center (BDC) to the volume at Top Dead Center (TDC) for the compression stroke. Common engines have a fixed CR limited by detonation. Because detonation occurs under known conditions, and generally not under a light load, such as a vehicle at cruising speed, an engine may safely operate at a higher compression ratio under such light loads. Further, a higher CR increases the thermodynamic efficiency of an engine, converting more of the thermal energy produced by combustion into useful mechanical energy. The variable compression ratio of the axial engine  10  may be varied between 8:1 CR and 20:1 CR, increasing the engine&#39;s thermodynamic efficiency by as much as 27 percent. 
     A perspective view of an inner cam  30  of the axial engine  10  is shown in  FIG. 4 . The inner cam  30  includes an inner cam trajectory (or channel)  36  on a cylindrical outside surface which guides a cam follower  54  (see  FIGS. 6 and 8A ) at the bottom end of a connecting rod  52 . An inner cam shaft spline  34  engages the engine shaft  48  to couple to rotation of the inner cam  30  to valves in the cylinder head  14 , and to couple the axial engine  10  to a load. An inner cam gear  32  couples the inner cam  30  to an outer cam  40 . 
     A perspective view of the outer cam  40  of the axial engine according to  10  is shown in  FIG. 5 . The outer cam  40  includes an outer cam trajectory (or channel)  44  (see  FIG. 8B ) in a cylindrical inside surface. The inner cam  30  and outer cam  40  counter rotate at the same angular speed and are part of a cam assembly  38  (see  FIG. 9 ) moveable parallel to the engine shaft  48  towards and away from the cylinder head  14 . 
     Pistons  50  and connecting rods  52  engaging the inner cam  30  are shown in  FIG. 6 . The inner cam  30  and outer cam  40  are radially spaced apart providing room for piston connecting rods  52  between the inner cam  30  and outer cam  40 . Cam followers  54  engage both the inner cam channel  36  (see  FIG. 8A ) and outer cam channel  44  (see  FIG. 8B ) to transform rotation of the cams into reciprocal motion of the pistons  50 , replacing the crankshaft in common engines. The torque applied to the output shaft by the pressure in the combustion chamber is now applied at a 90 degree angle by a fixed length displacement arm defined by the center line of the output shaft  48  and the center line of the connecting rod  52  through 90 degrees of rotation. This is different from the common engine where the effective displacement arm varies from zero to ½ the stroke length and back to zero through 180 degrees of rotation of the crankshaft. 
     The inner cam gear  32  having inside teeth  32   a  and outer cam gear  42  having inside teeth  42   a  are shown rotationally coupled by pinion gears  64  in  FIG. 7 . The arrangement and ratio of the gears  32 ,  42 , and  64  provides the counter rotation of the inner cam  30  and outer cam  40  and couple rotation of the outer cam  40  to the engine shaft  48 . 
     The inner cam channel  36  is shown in  FIG. 8A  and the outer cam channel  44  is shown in  FIG. 8B . Because the expansion and exhaust strokes are longer than the intake and compression strokes, the inner cam channel  36  must split into first inner channel  36   a  (having node  36   a ′ corresponding to Bottom Dead Center (BDC) on following the intake stroke), and second inner channel  36   b  (having a node  36   b ′ corresponding to BDC on following the expansion stroke), between Top Dead Center (TDC) events to stay aligned with the outer cam channel  44  (having nodes  44 ′ and  44 ″) through 360 degrees of engine shaft  48  rotation. The nodes  36   a ′ and  44 ′ are aligned and the nodes  36   b ′ and  44 ″ are aligned to concurrently guide the cam followers  54  (see  FIG. 6 ). The cam channels  36  and  44  further include a flat combustion segment C when the pistons  50  are at TDC between the compression and power strokes of the axial engine  10 . The segment C provides Constant Volume Combustion (CVC) eliminating negative work produced by combustion produced pressure before TDC in common crankshaft reciprocating engines. The segment C may be between 0 and 30 degrees of Engine Shaft Rotation (ESR) and is preferably about 10 degrees of engine shaft rotation. 
     The channels  36  and  44  further provide a short stroke A for the compression and intake, and a longer stroke B for exhaust and power strokes. The longer stroke B of the power stroke permits the axial engine  10  to extract more energy from combustion than crankshaft engines which must have same length strokes. An example of a preferred ratio of B to A is 1.7:1. 
     A first cross-sectional view of the cam assembly  38  and cylinder block  56  and cylinder bores  46  of the axial engine  10  is shown in  FIG. 9  and a second cross-sectional view of the cam assembly  38  and cylinder block  56  taken along line  10 - 10  of  FIG. 9  is shown in  FIG. 10 . Servo screws  28  preferably engage the cam casing  58  to move the cam assembly  38  towards and away from the cylinder head  14 , but those skilled in the art will recognize various apparatus for moving such structures, and any axial engine moving a cam assembly towards and away from a cylinder head is intended to come within the scope of the present invention. The cam assembly  38  is preferably keyed to the engine housing  12  to resist rotation of the cam assembly  38 . The keying may be, for example, by the cooperation of a slot  62  and pin  60 , but those skilled in the art will recognize various structure for rotationally coupling such structures, and an axial engine having other rotational coupling is intended to come within the scope of the present invention. 
     A top perspective view of the piston  50  and connecting rod  52  of the axial engine  10  is shown in  FIG. 11 , a first bottom perspective view of the piston  50  and connecting rod  52  is shown in  FIG. 12 , a second bottom perspective view of the piston  50  and connecting rod  52  is shown in  FIG. 13 , a first side view of the piston  50  and connecting rod  52  is shown in  FIG. 14A , and a second side view of the piston  50  and connecting rod  52  is shown in  FIG. 14B . The piston  50  and connecting rod  52  are preferably a single piece connecting at the rod top end  52   a . The rod bottom end  52   b  includes both opposing cam followers  54  and wings  66  which slide between the inner cam  30  and outer cam  40  maintaining a proper alignment of the connecting rod  52  and the cam followers. 
     A top perspective view of the cylinder head  14  of the axial engine  10  is shown in  FIG. 15 , a bottom perspective view of the cylinder head  14  is shown in  FIG. 16 , a first side view of the cylinder head  14  is shown in  FIG. 17A , and a second side view of the cylinder head  14  is shown in  FIG. 17B . The axial engine  10  includes fuel or water injectors  68  and preferably fuel and water injectors  70 . The fuel or water injectors  68  may be supported by injector brackets  69  to aim a spray of fuel or water into the air intakes  16  or the fuel injectors  68  may be mounted to the cylinder head  14  and spray into the ports between the air intake  16  and rotary valves  72   a  and  72   b , or may be direct injection fuel and water injectors  70 , and spray directly into the combustion chamber  76 . 
     The water injectors  70  preferably spray directly into the combustion chamber  76 . The water injection preferably includes three phases per cycle. For example, a first water injection phase may occur during the compression stroke where the water is used to cool the air/fuel mixture. This reduces pressure and as a result, compression work, in the cylinder and allows an increase in the compression ratio. A second water injection phase may occur during combustion (start of the combustion segment C) and is used to cool the combustion process. This eliminates the need for Exhaust Gas Recirculation (EGR) and further enables higher compression ratios. A third water injection phase may occur during expansion (after combustion occurs) and provides for the internal cooling of the combustion chamber  76 , piston  50  and the rotary valves  72   a  and  72   b . This allows internal regeneration, where part of the heat that would be lost to the engine walls is retrieved to produce work by the expansion of the liquid water into vapor. Also, the wall temperature inside the engine may be decreased and controlled by the water fuel ratio and water injection duration. This eliminates hot spots reducing the onset of knock. The net effect of the three phases of water injection is an increase in fuel efficiency, through compression work reduction, higher thermodynamic efficiency from compression ratio increase, and regeneration of energy otherwise lost to the heat transferred to the cylinder walls. Combustion chamber surfaces should preferably be between 250 and 300 degrees Centigrade to provide adequate vapor pressure for the regenerative cooling. 
     The water to fuel ratio may vary from 0:1 to 7:1, and is preferably 4.3:1 at idle and 1.4:1 at Wide Open Throttle (WOT). The water injection may be an open loop process (the water is lost via the exhaust), or a substantial amount, up to 66% of the total water in the exhaust, may be recovered and recycled via, for example, a capillary condensation pore process as described in U.S. Pat. No. 8,511,072, issued Aug. 20, 2013 and herein incorporated by reference above in its entirety. 
     The axial engine  10  preferably utilizes a rotary valve cylinder head including rotary valves  72   a  and  72   b  shown in  FIG. 18  and an example of drive structure for the rotary valves  72   a  and  72   b  is shown in  FIG. 19 . The rotary valves  72   a  and  72   b  provide fast opening and closing, a simple system without camshafts and/or rockers, and much wider opening than known poppet valves. The rotary valves are cylindrical and rotate at a speed proportional to the engine shaft speed, preferably driven through bevel gears  49   a  and  49   b  and the valve gear shaft  25 . The rotary valves  72   a  and  72   b  include passages  74  connecting the combustion chambers  76  with the air intakes  16  and exhaust headers  18 . The instantaneous angular positions of the rotary valves  72   a  and  72   b  determining which passages are open to the combustion chambers  76 . Each rotary valve  72   a  and  72   b  cooperates with two cylinders of the axial engine  10 . The intake valve is timed to open at the end of top dwell and to close at the end of bottom dwell to ensure maximum AFM is ingested during the intake stroke. The exhaust valve is timed to open at the beginning of bottom dwell and close at the beginning of top dwell to minimize pumping losses during the exhaust stroke. 
     An example of a preferred rotary valve is a modified Bishop rotary valve. The Bishop rotary valves provide improved volumetric efficiency, optimized turbulence, and much faster opening and closing times. The Bishop rotary valve design in described in U.S. Pat. No. 4,852,532 issued Aug. 1, 1989, incorporated above by reference in its entirety. 
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.