WO1987000574A1

WO1987000574A1 - Rotating valve device for internal combustion engines

Info

Publication number: WO1987000574A1
Application number: PCT/IT1986/000054
Authority: WO
Inventors: Luis Maria Antonello
Original assignee: Luis Maria Antonello
Priority date: 1985-07-17
Filing date: 1986-07-16
Publication date: 1987-01-29
Also published as: EP0229147A1; IT8548367A0; IT1184288B

Abstract

A rotating valve device for internal combustion engines in which at least one piston (12) reciprocates inside a cylinder (10), an admission duct (20) carries the gas to be admitted into the cylinders, and an exhaust duct (22) carries the exhaust gases procuded by combustion inside the cylinder. This rotating valve device for internal combustion engines is characterized in that at least one rotating valve (28) provided with apertures for passage of gas, is moved by an electric stepper motor (56), responding to commands received from a central processing unit, and at once is moved to one of several positions where it will either open or close ports through which fresh gas is admitted into the cylinder and/or will either open or close burned gas exhaust ports.

Description

ROTATING VALVE DEVICE FOR INTERNAL COMBUSTION ENGINES

This invention relates to a rotating valve device for internal combustion engines and, in particular refers to a device comprising a disc-shaped valve which is Dositively rotated to permit the opening and closing of fresh gas admitting ports or burned gas exhausting ports into and out of, respectively, the cylinder of an internal combustion engine. Conventional devices based on reciprocating poppet valves are known to have several drawbacks, the main one being the inertia and the delays proper to mechanical actuators, which may eventually cause damages in an internal combustion engine when it is running at a combaratively high number, of revolutions.

Actually, the valves and the piston, while moving bad and forth, alternately fill the same soace, that is when the piston is rising it will fill the space previously tilled bv the valves when they were down. Since this principle of operation is based on precisely synchronized motions of the valves and the piston, and synchronization is mureasingly lost as the engine number of revolutions increases, at the time rotation exceeds a given speed, the amount of mechanical delay will be such that the piston will knock against the valve head and cause it to break thus seriously damaging vital parts in the engine. One further drawback is the functional rigidity of mechanical drive means normally employed to give motion to conventional valves, which is reflected in rigid engine performance characteristics, that is such characteristics cannot be changed in real time. Attempts have been made to overcome those drawbacks by developing improved valves and valve control devices in which the valve return time was shortened by using specially designed springs and devices that forced the valve to return to the closed position.

Those devices, however, have so far failed to significantly increase the maximum useable rotation speed of internal combustion engines while on the other hand requiring a considerable waste of energy to operate.

The main object of this invention is, therefore, to provide a. rotating valve device for internal combustion engines allowing the rotating valve to be moved to the desired position in a very short time, which is negligible as compared with the time needed to move the other engine mechanical parts, the valve to be kept in that position for as long as desired, and then the valve be moved in either direction to reach a new working position, and so on.

Another object of this invention is to provide a rotating valve device requiring negligible power to move. One further object of this invention is to provide a rotating valve device having a simplified and low-cost structure suitable for mass production.

According to this invention, a rotating valve device for internal combustion engines is characterized in that at least one rotating valve, provided with ports for passage of gas, is controlled by a stepper motor responding to commands received from a central processing unit and is at each step moved to one of several positions where it will either open or close ports through which fresh gas is admitted into the cylinder or either open or close burned gas exhaust ports.

The main object of this invention is, therefore, to provide a rotating valve device for internal combustion engines allowing the rotating valve to be moved to the desired position in a very short time, which is negligible as compared with the time needed to move the other engine mechanical parts, the valve to be kept in that position for as long as desired, and then the valve be moved in either direction to reach a new working position, and so on.

Another object of this invention is to provide a rotating valve device requiring negligible power to move. relevant data are processed by the central processing unit (CPU), in order to change the admission and exhaust ports opening times and modes, either in real time or according to predetermined operating modes, since the stepping time of a stepper motor is by all means a negligible fraction of the rotation period of an internal combustion engine.

One further advantage is that the rotating valve can be easily set to one position or a series of positions to obtain a so-called neutral operation of the cylinder, that is to say no explosive mixture will flow into the cylinder and no compression will occur; by this method, the engine will be running with one or more cylinders in idle mode which will result in lower fuel consumption and less air pollution.

One more advantage of this device is that by using a rotating valve, turbulence areas are easily created. This will facilitate the distribution of fuel-air mixture and eventually speed up the diffusion of explosion in the mixture.

In the following, the present invention will be further clarified by the description of two practical embodiments of the rotating valve device for internal combustion engines, a description made out in a purely illustrative and not limitative way, with reference to the accompanying drawings, in which: figure 1 is a cross-section view of an internal combustion engine provided with a rotating valve device according to this invention; figure 2 is a bottom cross-section view taken along line II-II of figure 1; figure 3 is a partial cross-section view similar to figure 1 showing another embodiment of the rotating valve device according to this invention; and figure 4 is a bottom cross-section view taken along line IV-IV of figure 3.

Referring to the accompanying drawings, and in particular to figure 1, an internal combustion engine includes a cylinder 10, in which slides a piston 12 that actuates a cran. shaft 14 through a connecting rod 16. The engine can conventionally include several Cylinders in which as many pistons, phase-shιfted by appropriate angles, will slide with alternate motion. Above cylinders 10 there is a head 13 in which a fuel-air mixture admission du ct 20 and a burned gas exhaust duct 22 have been machined.

The fuel-air mixture is combined in a conventional carburetor 24, and exhaust duct 22 is terminated with conventional mufflers for exhausting the gas into the air.

A rotating valve 28, float-mounted around a hollow shaft 30, rotates against the precisely levelled off surface 23 of head 18 that faces cylinder 10.

Rotating valve 28 is constrained to rotate integral with shaft 30 by means of transport teeth, however it is free to oscillate around it in order that its precisely levelled off top surface can adhere to surface 23 of head 18, to ensure tightness.

On hollow shaft 30 is mounted a toothed pulley 32, secured to shaft 30 by means of key 34, while a backlash compensating spring 36, working between pulley 32 and a retaining washer 33 kept in place by a locking ring 40, serves to make hollow shaft 30 freely rotate, with no end play, within two guide bushings 42 and 44. An antifriction washer 46 separates pulley 32 from head 18.

Inside hollow shaft 30 there is a spark plug consisting of a dielectric or insulator 48 and an electrode 50, connected to the ignition electric power system through a leaf spring 52, attached to head 13 through an isolator 54,.

An electric stepper motor 56, having the function of actuating the rotating valve 23, is provided with a toothed pulley 58 that in turn actuates toothed pulley 32 through a cogged belt 60.

Stepper motor 56 is connected to a central processing unit (not shown) which contains appropriate sensors that constantly detect motor characteristic values such as the driving sha.ft position, the temperature of various parts, and the like. The CPU also contains one ar more microprocessors to process data and provide commands tα be sent to the actuators. The CPU is, therefore, able to control stepper motor 56 in order to move, as needed, rotating valve 23 at chosen optimal directions and speeds. The techniques required to implement the CPU are well known and are not described further.

As is better shown in Figure 2, rotating valve 28 has three apertures 62 through which the gas is let in, while head 18 has on its surface 26 a total of six apertures or por ts for the passage of gas.

Of the ports on the head, represented by dashed lines in figure 2, three, 64, are connected with admis sion duct 20 and are used for admitting the fuel-air mi xture, and three, 66, connected with exhaust duct 20 , are used for burned gas exhaust.

Apertures 62 are circul ar in shape and are located at the vertices of an equilateral triangle.

Ports 64 and 66 are circular in shape too and are t hree- by-th ree located at the vertices of an equilateral triangle .

The center s of ports 64 and 66 lie on a circle and are 40- and 80-degree a lternateIy spaced.

By that arrangement, when, for instance, valve 28 is rotating c lockwise (as seen in figure 2), in 40-degree steps, it will first open admission ports 64, will then set to the position shown in figure 2, i.e. with both ports 6A and 66 closed, and finally, at the next step, it will open exhaust ports 66. Let us now refer to figures 3 and 4 which show the second embodiment of the device according to this invention. Here head 18 is provided with injectors 63 for fuel admission, and with conventional spark plugs 70 normally used with Otto cycle engines. In Diesel cycle engines, spark plugs 70 are replaced by heater plugs for starting the engine. In that case only air will flow through the admission duct.

Rotating valve 72 in figures 3 and 4 has two gas ports 74, and head 76 has two admission ports 78 and two exhaust ports 80.

Ports 74 are roughly trapezoidal in shape and are diametrically opposite with respect to valve 72 center of rotation. Similarly, ports 78 and 80 are two-by-two diametrically opposite, have a roughly trapezoidal shape, and are 60- and 120-degree alternately spaced along a circle.

As the valve rotates by one 60-degree step, communications will be established between the cylinder and the outside exactly as was previously described with reference to figures 1 and 2.

Referring to figure 2, let us now suppose that the device is at the beginning of the suction phase with the piston at the top dead center; at that point, the CPU will actuate motor 56 in steps until ports 62 of rotating valve 28 are in line with admission ports 64. In that position, the fuel-air mixture is sucked inside the cylinder while the piston is moving towards the bottom dead center.

With the piston in that position, Lhe CPU will move rotating valve 28 to the position shown in figure 2 where all ports in head 13 are closed, after choosing the proper leads or lags on the basis of sensor-supplied data. The rotating valve will be maintained in that position all along the compression, explosion and expansion phases, up to the next bottom dead center position of the piston.

After it has reached the latter position, the rotating valve will be moved, with leads or lags determined αy the CPU, to a position where ports 62 are in line with exhaust ports 66, and will be maintained in that position throughout the exhaust phase, until the piston reaches the top dead center thus allowing the burned gases to escape.

The device has thus been brought bad to the initial condition and the cycle begins again, with rotating valve 28 being moved to the position where the next suction phase will start,.

If an engine mode of operation has been preset such as to have one cylinder inactive, the CPU will move rotating valve 28 to the position where ports 62 are in line with exhaust ports 66, and will maintain it in that position for as long as necessary to permit the cylinder to remain inactive. If, however, the cylinder should be required to work again for the engine to deliver more power, then the CPU will move rotating valve 28 as previously described, and the engine thermodynamic cycle will be resumed.

The rotating valve device shown in figures 3 and 4 operates in the same way as that shown in figures 1 and 2, except that, as an additional feature, the cylinder can be made inactive by opening exhaust ports 80 during the compressi on phase , and admi ssi on ports 78 duri ng the expansi on phase, obviously with no fuel injected through injector 68; this will cause only air to circulate between the admission duct and the exhaust duct, with no fuel supply and no waste of energy as would be necessary to effect compression.

The opening and/or closing lags and/or leads can of course be easily changed dynamically during the internal combustion engine operation so that the engine operating characteristics, especially the engine torque, may be such as to meet new engine power requirements in real time.

It should be noted that although two possible embodiments of this device provided with a single rotating valve per cylinder have been shown and described, each cylinder can be provided with more than one appropriately sized valve.

In addition, both the number and shape of the ports on the head can be changed, and so can the shape and number of ports.

Besides that, the number of ports and apertures can be increased to form a grid of holes for passaqe of gas, which will be opened and closed by rotating the valve through just a few degroes.

It is obvious that other numerous and different change s a nd modific at ions c an be performed by the sk illed in die art on the embadiments of the present invention hereinbefore duscri bad, without departing from its scope, It is intended, therefore, that all those changes and m odif ications a re encompassed in the field of this inve nt ion.

PCT WORLD INTELLECTUAL PROPERTY ORGANIZATION International Bureau

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)

(51) International Patent Classification 4 (11) International Publication Number: WO 87/ 005 FOIL 9/04, 7/06 Al

(43) International Publication Date: 29 January 1987 (29.01.

(21) International Application Number: PCT/IT86/00054 Published

With international search report.

(22) International Filing Date: 16 July 1986 (16.07.86) Before the expiration of the time limit for amending claims and to be republished in the event of the rec of amendments.

(31) Priority Application Number: 48367 A/85

(32) Priority Date: 17 July 1985 (17.07.85)

(33) Priority Country: IT

(71X72) Applicant and Inventor: ANTONELLO, Luis, Maria [AR/IT]; Via XXI Aprile, 12, 1-00162 Roma (IT).

(81) Designated States: AT (European patent), BE (European patent), CH (European patent), DE (European patent), FR (European patent), GB (European patent), IT (European patent), JP, LU (European patent), NL (European patent), SE (European patent), US.

(54) Title: ROTATING VALVE DEVICE FOR INTERNAL COMBUSTION^'ENGINES

(57) Abstract

A rotating valve device for internal combustion engines in which at least one piston (12) reciprocates inside a cylinder (10), an admission duct (20) carries the gas to be admitted into the cylinders, and an exhaust duct (22) carries the exhaust gases pro- cuded by combustion inside the cylinder. This rotating valve device for internal combustion engines is characterized in that at least one rotating valve (28) provided with apertures for passage of gas, is moved by an electric stepper motor (56), responding to commands received from a central processing unit, and at once is moved to one of several positions where it will either open or close ports through which fresh gas is admitted into the cylinder and/or will either open or close burned gas exhaust ports.

FOR THE PURPOSES OF REFORMATION ONLY

Codes used to identify States party to the PCT on the front pages of pamphlets publishing international appli- cations under the PCT.

AT Austria GA Gabon MR Mauritania

AU Australia GB United Kingdom MW Malawi

BB Barbados HU Hungary NL Netherlands

BE Belgium rr Italy NO Norway

BG Bulgaria JP Japan RO Romania

BR Brazil KP Democratic People's Republic SD Sudan

CF Central African Republic of Korea SE -.Sweden

CG Congo KR Republic of Korea SN Senegal

CH Switzerland LI Liechtenstein SU Soviet Union

CM Cameroon LK Sri Lanka TD Chad

DE Germany, Federal Republic of LU Luxembourg TG Togo

DK Denmark MC Monaco US United States of America

Fl Finland MG Madagascar

FR France ML Mali

ROTATING VALVE DEVICE FOR INTERNAL COMBUSTION ENGINES

This invention relates to a rotating valve device for internal combustion engines and, in particular refers to a device comprising a disc-shaped valve which is Dositively rotated to permit the opening and closing of fresh gas admitting ports or burned gas exhausting ports into and out of, respectively, the cylinder of an internal combustion engine. Conventional devices based on reciprocating poppet valves are k nown to have several drawbacks, the main one being the inertia and the delays proper to mechanical actuators, which may eventually cause damages in an internal combustion engine when it is running at a combaratively high number, of revolutions.

Actually, the valves and the piston, while moving bad and forth, alternately fill the same soace, that is when the piston is rising it will fill the space previously tilled bv the valves when they were down. Since this principle of operation is based on precisely synchronized motions of the valves and the piston, and synchronization is mureasingly lost as the engine number of revolutions increases, at the time rotation exceeds a given speed, the amount of mechanical delay will be such that the piston will knock against the valve head and cause it to break thus seriously damaging vital parts in the engine. One further drawback is the functional rigidity of mechanical drive means normally employed to give motion to conventional valves, which is reflected in rigid engine performance characteristics, that is such characteristics cannot be changed in real time.

Attempts have been made to overcome those drawbacks by developing improved valves and valve control devices in which the valve return time was shortened by using specially designed springs and devices that forced the valve to return to the closed position.

Those devices, however, have so f ar failed to significantly increase the maximum useable rotation speed of internal combustion engines while on the other hand requiring a considerable waste of energy to operate.

Several advantages are , therefore, achieved with the device according to this invention, the main one being that the pi ston and valves do not slide along the same path which prevents the val es from being broken because of delayed motion at an excessively high speed of engine rotation, and consequently the engine useable rotation speed can b e increased as required.

Another adv antage lies in the considerable reduction of power necessary to move the valves since the efficiency of the stepper motor and of the l inear transmission of motion to the rotating valve is by far greater than that of conventional valve drive methods.

A further advantage is that the engine characteristic curve can be easily modified because all relevant data are processed by the central processing unit (CPU), in order to change the admission and exhaust ports opening times and modes, either in real time or according to predetermined operating modes, since the stepping time of a stepper motor is by all means a negligible fraction of the rotation period of an internal combustion engine.

One further advantage is that the rotating valve can be easily set to one position or a series of positions to obtain a so-called neutral operation of the cylinder, that is to say no explosive mixture will flow into the cylinder and no compression will occur; by this method, the engine will be running with one or morecylinders in idle mode which will result in lower fuel consumption and less air pollution.

One more advantage of this device is that by using a rotating valve, turbulence areas are easily created. This will facilitate the distribution of fuel-air mixture and eventually speed up the diffusion of explosion in the mixture .

In the following, the present invention will be further clarified by the description of two practical embodiments of the rotating valve device for internal combustion engines, a description made out in a purely illustrative and not limitative way, with reference to the accompanying drawings, in which: fiαure 1 is a cross-section view of an internal combustion engine provided with a rotating valve device according to this invention; figure 2 is a bottom cross-section view taken along line II-II of figure 1; figure 3 is a partial cross-section view similar to figure 1 showing another embodiment of the rotating valve device according to this invention; and figure 4 is a bottom cross-section view taken along line IV-IV of figure 3.

Rotating valve 28 is constrained to rotate integral with shaft 30 by means of transport teeth, however it is free to oscillate around it in order that its precisely levelled off top surface can adhere to surface 28 of head 18, to ensure tightness.

On hollow shaft 30 is mounted a toothed pulley 32, secured to shaft 30 by means of key 34, while a backlash compensating spring 36, working between pulley 32 and a retaining washer 38 kept in place by a locking ring 40, serves to make hollow shaft 30 freely rotate, with no end play, within two guide bushings 42 and 44. An antifriction washer 46 separates pulley 32 from head 18.

Inside hollow shaft 30 there is a spark plug consisting of a dielectric ar insulator 43. and an electrode 50, connected to the ignition electric power system through a leaf spring 52, attached to head 18 through an isolator 54.

An electric stepper motor 56, having the function of actuating the rotating valve 23, is provided with a toothed pulley 58 that in turn actuates toothed pulley

32 through a cogged belt 60.

Stepper motor 56 is connected to a central processing unit (not shown) which contains appropriate sensors that constantly detect motor characteristic values such as the driving shaft position, the temperature of various parts, and the like. The CPU also contains one or more microprocessors to process data and provide commands to be sent to the actuators. The CPU is, therefore, able to control stepper motor 56 in order to move, as needed, rotating valve 28 at chosen optimal directions and speeds. The techniques required to implement the CPU are well known and are not described further.

By that arrangement, when, for instance, valve 28 is rotating c lockwise (as seen in figure 2), in 40-degree steps, it will first open admission ports 64, will then set to the position shown in figure 2, i.e. with both ports 64 and 66 closed, and finally, at the next step, it will open exhaust ports 66. Let us now refer to figures 3 and 4 which show the second embodiment of the device according to this invention. Here head 18 is provided with injectors 68 for fuel admission, and with conventional spark plugs 70 normally used with Otto cycle engines. In Diesel cycle engines, spar! plugs 70 are replaced by heater plugs for starting the engine. In that case only air will flow through the admission duct.

Rotating valve 72 in figures 3 and 4 h a s two gas ports 74, and head 76 has two admission ports 73 and two exhaust ports 80.

Porte 74 are roughly trapezoidal in shape and are diametrically opposite with respect to valve 72 center of rotation. S imilar y, ports 78 and 80 are two-by-two. diametrically oppcsite, have a roughly trapezoidal shape, and are 6 0 and 120-degree alternately spaced along a circle.

As the valve rotates by one 60-deqree step, communications wiII be established between the cylinder and the outside exactly as was previously described with reference to figur es 1 and 2.

Referring to figure 2, let us now suppose that the device is at the beginning of the suction phase with the piston at the top dead center; at that point, the CPU will actuate motor 56 in steps until ports 62 of rotating valve 28 are in line with admission ports 64 . In that position, the fuel-air mixture is sucked inside the cylinder while the piston is moving towards the bottom dead center.

With the piston in that position, the CPU will move rotating valve 28 to the position shown in figure 2 where all ports in head 18 are closed, after choosing the proper leads or lags on the basis of sensor-supplied data. The rotating valve will be maintained in that position all along the compression, explosion and expansion phases, up to the next bottom dead center position of the piston.

After it has reached the latter position, the rotating valve will be moved, with leads or lags determined b y the CPU, to a position where ports 62 are in line with ex haust ports 66 , and will be maintained in that posit ion throughout the exhaust phase, until the piston reaches the top dead center thus allowing the burred qases to escape.

The device has thus been brought bad to the initial condition and the cycle begins again, with rotating valve 25 being moved to the position where the next suction phase will st art.

If an engine mode of op eration has been preset such as tα have one cylinder inactive, the CPU will move rotating valve 28 to the position whore ports 62 are in line with exhaust ports 06, and will maintain it m that position for as long as necessary to permit the cylinder to remain inactive. If, however, the cylinder should be required to worl again for the engine to deliver more power, then the CPU will move rotating valve 28 as previously described, and the engine thermodynamic cycle will be resumed.

The rotating valve device shown in figures 3 and 4 operates in the same way as that shown in figures 1 and 2, except that, as an additional feature, the cylinder can be made inactive by opening exhaust ports 80 during the compression phase, and admission ports 78 during the expansion phase, obviously with no fuel injected through injector 68 : this will cause only air to circulate between the admission duct and the exhaust duct, with no fuel supply and no waste of energy as would be necessary to effect compression.

The opening and/or closing lags and/or leads can of course be easily changed dynamically during the internal comb ustion engine operation so that the engine operating characteristics, especially the engine turque, may be sυch as to meet new engine power requirements in real time.

It should be noted that although two possible embodiments of this device provided with a single rotating valve per cylinder have been shown and described, each cylinder can to provided with more than one appropriately sized valve.

Besides that, the number of ports and apertures can be increased to form a grid of holes for passage of gas, which will be opened and closed by rotating the valve through just a few degrees.

It is obvious that other numerous and different changes an d modιfications can be performed by the sk iIled in the ar t on the embodiments of the present invention hereinbefore de scribed, without departing from its scope. It is intended, therefore, that all these changes and modifications ar e encompassed in the field of this invontion.

Claims

CLA IMS

1. A rotating valve device for internal combustion engines in which at least one piston reciprocates inside a cylinder, an admission duct carries the gas to be admitted into the cylinders and an exhaust duct carries the exhaust gases produced by combustion inside the cylinder, characterized in that at least one rotating valve (23, 72), provided with apertures (62, 74) for passage of gas, is moved by an electric stepper motor (56), responding to commands received from a central processing unit, and at once is moved to one of several positions where it will either open or close ports (64, 78) through which fresh gas is admitted into the cylinder and/or will either open or close burned gas exhaust ports (66, 30).

2. A device according to Claim 1, characterized in that said rotating valve (28, 72) is float-mounted to a shaft (30) revolving inside the internal combustion engine head (18), the arrangement being such that the head (18) surface (26) facing the cylinder cooperates with rotating valve (28, 72) to ensure gas tightness.

3. A device according to Claim 2, characterized in that said rotating valve (28, 72) is constrained to rotate integral with said shaft (30) which in turn is imparted motion by said electric motor (56) through appropriate drive means.

4. A device according to Claim 3, characterized in that said drive means consist of two toothed pulleys (32, 58) and a cogged belt (60).

5. A device according to any one of Claims 2, 3, or 4, characterized in that said shaft (30) is hollow and inside it there is a spart plug comprising an electrode (50) insulated by means of an appropriate dielectric (48).

6, A device accord my to any one of Claims 1 through 4, characterized in that one spar k plug (70) is loc at ed on head (18) wh er e it will be uncovered by a port (62, 74 ) of rutating valve (28, 72) when the valve is in the position in which it closes all gas ports.

7. A device according to any one of the preceding Claims, characterized in that said internal combustionengine is provided with a carburetor (24) and the fuel-air mixture flows through the admission duct.

8. A device accordiny to any one of Claims 1 through 6 , charactorized in that said internal combustion engine is provided with an injection system and each injector (63) is located on head (18) where it will be uncovered by a port (62, 74) of rotating valve (28, 72) when the valve is in the position in which it closes all gas ports.

9. A device according to any one of the preceding Claims, characterized in that the ports ( 6 2 ) of said rotating valvce (28, 72) are circular in shape.

10. A device according to any one of Claims 1 through 8, characterized in that the ports (74) of said rotating valve (28, 72) have a roughly trapezoidal shape.

11. A device according to any one of the preceding Claims, characterized in that the ports (62) of said rotating valve (28) are three and are located at the vertices of an equilateral triangle whose center is in line with the valve center of rotation.

12. A device according to any one of Claims 1 through 10, characterized in that the ports (74) of said rotating valve (72) are two and are diametrically opposite with respect to the valve center of rotation.

13. A device according to any one of Claims 1 through 10, characterized in that the ports on the rotating valve comprise a grid of holes.