CENTRIFUGAL GOVERNOR

Abstract: The disclosure relates to a centrifugal governor for a prime mover, preferably an internal combustion engine, with a damping device (4) susceptible to influence the movement of an actuator rod (2), the damping device substantially only acting upon the throttle-up movement of the actuator rod (2), by the intermediary of means (12, 18, 51, 52, 61, 62) included in the damping device. The apparatus according to the invention is intended to prevent the prime mover from racing to dangerously high engine speeds in connection with fuel throttle-back if its load suddenly disappears.

Description: CENTRIFUGAL GOVERNOR TECHNICAL FIELD The present invention relates to a centrifugal governor for a prime mover, preferably an internal combustion engine, with a damping device susceptible to influence the movement of an actuator rod. BACKGROUND ART Centrifugal governors have been employed for many years within internal combustion engine technology. In, for example, the regulation of an injection pump for a diesel engine, resonance frequencies may be incorporated fortorsional vibration determined primarily by the moment of inertia of the rotary masses included in the injection pump, by the torsional rigidity in shafts and couplings and also by the overall function and construction of the governor system proper. This implies that, at certain speeds, the engine will jerk since its output will vary in accordance with the oscillations. Apparatuses have long been available in this Art for damping the oscillations in centrifugal governors. These generally operate hydraulically or frictionally. Attempts have also recently been made in the Art to damp such oscillations by electronic means. Frictional damping has proved to be less appropriate, since it creates an undesirable hysteresis effect on the governed engine speed. Prior art hydraulic dampers damp in both the increasing and decreasing throttle directions - by way of simplification hereinafter referred to as throttle-up and throttle-back. Since, hereby, throttle-back may be rendered difficult, the speed of the governed prime mover will race to dangerously high levels if the load on the engine suddenly disappears. This may, for instance, be the case if the prime mover is a diesel engine for vehicles in which the driving wheels suddenly slip on a skiddy surface. SUMMARY OFTHE INVENTION One characterising feature of the present invention is, therefore, that a piston included in the damping device and connected to the actuator rod is disposed in a recess and defines a first pressure medium chamber, throttle means being provided in at least one channel between the first pressure medium chamber and a second pressure medium chamber. The damping device is intended to avoid resonance frequencies incorporated in a governor system included in the internal combustion engine for governing an injection pump included in the engine and influences substantially only the throttle-up movement of the actuator rod, by the intermediary of single- acting devices included in the damping device. The single-acting devices included in the damping device consist of at least one channel with a non¬ return valve disposed therein, the channel placing the first and second pressure medium chambers in communication with each other. Using state-of-the-art apparatuses, throttle-up is too slow primarily from cold start and at large load increases. This is because of the cold damping oil present in the damper, which results in greater damping than normal. The present invention obviates this drawback and reduces damping of the throttle-up movement if the setting force of the governor exceeds a certain value but damps fully if the setting force is lower than the above-mentioned value. it has been noted that, in prior art governors of diesel engines, the engine may stall if throttle-back is abruptly engaged and if the damping is already operative at slight throttle-up, i.e. slight fuel supply volumes. Consequently, * according to the present invention damping is reduced on throttle-up in the region between idling and fuel supply shut-off. Furthermore, the apparatus according to the present invention is characterised by simple and economical design. The damping device may be applied with but minor modifications to centrifugal governors in a number of various contexts. BRIEF DESCRIPTION OFTHE ACCOMPANYING DRAWINGS The nature of the present invention and its further aspects, advantages and characterising features will be apparent from the appended Claims, the accompanying Drawings, and discussion of a number of preferred embodiments of the present invention with particular reference thereto. In the accompanying Drawings: Fig. 1 schematically illustrates a first embodiment of a centrifugal governor with a damping device according to the present invention adapted for regulating an injection pump in a diesel engine; Fig. 2 schematically illustrates a second embodiment of a centrifugal governor with a damping device according to the present invention; Fig.3 illustrates a third embodiment of a damping device included in a centrifugal governor according to the present invention; and Fig.4 illustrates a fourth embodiment of a damping device included in a centrifugal governor according to the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the Drawings, Fig. 1 shows a centrifugal governor 1 intended to govern a perse known injection pump 21 in a vehicle diesel engine. Two or more governor weights 5 are pivotally secured to a camshaft 47 included in the injection pump, in such a manner that, when the speed of the shaft 47 increases, they strive to increase their mass moment of inertia in relation to the shaft 47. The weights 5 are also connected, by linkages 23, to a first sleeve 7 coaxial with the shaft 47. The portion 24 of the sleeve 7 facing away from the weights 5 grasps about a flange 26 formed on a second sleeve 25 such that the second sleeve 25 accompanies the first sleeve 7 in its axial movement but not in its rotary movement. On its axial movement, the sleeve 25 slides on a permanently secured guide bolt 27 provided in a centre bore 28 drilled in the sleeve 25. A governor arm 8 is pivotally secured at the sleeve 25 and, when the sleeve 7 moves, pivots about a guide pin 9 and displaces an actuator rod 2 pivotally connected to the governor arm 8.ln the reciprocal movement, the actuator rod 2 revolves pump pistons included in the injection pump 21 for governing the injection volume of the pump (this operation is perse known in the Art and will not be described in greater detail here). In Fig. 1, an arrow to the left and a + sign indicate that the movement of the actuator rod to the left implies throttle-up, i.e. increased fuel supply, while its movementto the right is indicated by a corresponding arrow marked with a - sign which indicates throttle-back, i.e. reduced fuel supply. The governor arm 8 and actuator rod 2 are depicted by ghosted lines in a position for complete fuel supply shut-off, solid lines show a position for fuel supply for idling and broken lines depict the governor arm 8 and actuator rod 2 in an imaginary full-throttle position. The guide pin 9 is slidable in a guideway 29 disposed in the governor arm 8 and is secured to an accelerator arm 3 which isjournailed at a point 33 fixed in relation to the injection pump 21 and is operated, for example, manually or, by the intermediary of stays, by an accelerator pedal or corresponding manually actuable means (not shown). As a result of the sliding capability of the guide pin 9 in the guideway 29, the gear ratio of the governor arm may be modified. A damping device 4 is disposed at the lever of the governor arm 8 to which the actuator rod is secured. This damping device consists of a housing 17 with a cylindrical recess 30. A piston 11 is accommodated in this recess 30 and is, by the intermediary of a pre-tensioned extension spring 10, pivotally connected to the governor arm 8. The side of the piston 11 facing away from the spring 10 defines, together with the walls of the recess 30, a first pressure medium chamber 13. The damper 4 further includes single-acting damping means 12 and 18 which, in the embodiment according to Fig. 1, consist of a first channel 18 between the first pressure medium chamber 13 and a second pressure medium chamber 20, and a non-return valve 12 disposed in the channel 18 and closing when the piston 11 is retracted from the recess 30. Hydraulic oil is preferably employed as pressure medium. Hence, the single- acting function arises in that the movement of the piston is damped because of the dosed non-return valve 12 when the piston is retracted, but that this movement is not damped when the piston 11 is protracted into the recess 30, since the non-return valve 12 then opens the channel 18 and allows the passage of fluid from the chamber 13 to the chamber 20. The non-return valve 12 is, in this instance, of the ball type, but may of course, be of any other perse known design. The channel 18 is sufficiently wide to occasion, on the throttle-back movement of the actuator rod 2, as slight a pressure drop as possible. An adjustable throttle 14 is disposed in a second channel 19 between the chambers 13 and 20. The chamber 20 is intended to maintain a certain oil level and is, therefore, continuously fed with oil from an oil pump in a manner not shown here. An abutment member 15 which is movable in the direction of movement of the piston 11 is also provided in the housing 17, the abutment member preferably being in the form of a stub shaft pre- tensioned by a spring 16 disposed in a third oil-fitted chamber 48. The strut 15 comes into contact with the side of the piston 11 facing away from the spring 10 and counteracts, via the spring 16, the inward movement of the piston in the recess 30. Oil supply to the chamber 48 is effected from the chamber 13 by the intermediary of a channel 49. The apparatus shown in Fig. 1 functions as follows. It will, in this instance, be presupposed that the accelerator arm 3 operable by the vehicle driver remains at a certain setting and the purpose of the governor is to ensure that an engine speed corresponding to this position is maintained as far as is possible. Under load, it is often desirable that the engine work at an engine speed corresponding to a so-called full-throttle position on the actuator rod 2, depicted in Fig. 1 by a broken line. If, in such instance, the load on the engine increases, the speed of the engine decreases and the governor weights 5 are drawn in towards the shaft 47 by the spring 6. The sleeve 7 then moves to the right so that the governor arm 8 is revolved counter-clockwise about the guide pin 9 and urges the actuator rod 2 in the throttle-up direction to the left, with a view to readjusting the engine speed to the initial level. At the same time, the governor arm 8 strives to entrain the piston 11 in the damping device 4 by the intermediary of the pre-tensioned extension spring 10. When the piston 11 moves to the left and the non-return valve 12 is closed, a partial vacuum arises in the chamber 13 and a pressure drop occurs across the adjustable throttle 14. The force generated by the partial vacuum damps the throttle-up movement of the actuator rod 2 which thereby positively acts for re-establishment of the initial engine speed, with a view to avoiding the occurrence of oscillations in the regulation. The size of the damping force is determined by the speed of movement of the piston and the setting of the throttle 14. If, at desired full throttle, the load on the engine were instead to be reduced, the engine speed increases and the governor weights 5 move outwardly. In such an event, the sleeve 7 moves to the left so that the governor arm 8 is revolved clockwise about the guide pin 9 and draws the actuator rod 2 in the throttle-back direction to the right, with a view to reducing engine speed towards its initial value. The governor arm 8 strives to urge the piston 11 in the damping device 4 to the right. The non-return valve 12 then opens the channel 18 between the two chambers 13 and 20, so thatthe movement of the piston 11 is not damped, whereby the throttle- back effect may rapidly be translated into a reduction of the engine speed to initial level so that the risk of excessively high engine speeds is avoided. By such means will single-action damping in the throttle-up direction have been achieved. In order that fuel supply may reliably be shut-off completely, the actuator rod 2 may move a short distance to the right-hand end position represented by ghosted lines once the fuel volume has been adjusted down to zero. In snap throttle-back, it may happen that the actuator rod 2 unintentionally moves to this right-hand end position. Without an arrangement according to the present invention, there would then be a risk of the engine having time to stall, since the piston 11 would damp a subsequent throttle-up from the right-hand end position to that position where fuel begins to be supplied. Therefore, the abutment member 15 counteracts the damping in that it strives to urge the piston 11 to the left when the actuator rod 2 is located between the right-hand end position and that position where fuel begins to be supplied. Hereby, the above-mentioned risk of unintentional stalling may be substantially eliminated. When the throttle-up force exceeds the pre-tensioning force in the spring 10 so that this begins to stretch, rapid throttle-up takes place despite damping from the piston 11. This is of importance, for instance in cold engine start when the damping is large because of the high viscosity of the oil. When the throttle-up force is less than the pre-tensioning force of the spring 10, the spring 10 acts as rigid link and the actuator rod 2 follows the normal damped movement of the piston 11. Fig.2 shows a centrifugal governor 1 with a second embodiment of a damping device according to the present invention. Parts in Fig. 2 corresponding to parts in Fig. 1 have been given the same reference numeral in the figures. In Fig. 2, the centrifugal governor 1 is, as opposed to that illustrated in Fig. 1, secured to the same lever of the governor arm 8 as the actuator rod 2. No accelerator arm corresponding to that of Fig. 1 is shown in Fig. 2. Instead, this figure shows the operator's possible influence on the adjustment of the engine speed by double-headed arrows 22. The governor arm 8 and the actuator rod 2 are depicted by solid lines in a full-throttle position, by broken lines in an idling position and by ghosted lines in a position for complete fuel supply shut-off. The damping device 4 is secured to the other lever of the governor arm 8 and consists of a housing 17 with a cylindrical recess 30. A piston 11 is accommodated in the recess 30 and is, by means of a linkage 42, pivotally connected to the governor arm 8. The side of the piston 11 facing away from the linkage 42 defines, together with the walls of the recess 30, a first oil chamber 43. The side of the piston facing towards the linkage 42 defines, together with the walls ofthe recess 30, a second oil chamber 20. This is continuously supplied with oil in order to maintain a certain oil level. A non-return valve 12 is disposed in a first channel 18 between the chamber 43 and the chamber 20, the valve opening on pressure reduction (outward movement of the piston 11) and closing on pressure increase (inward movement of the piston 11) in the chamber 43. A throttle 44 is disposed in a second channel 19 between the chamber 43 and the channel 18 parallel with the non-return valve 12. A by-pass channel 31 with a valve 40 biased by spring means 41 is disposed in the piston 11 between the chambers 43 and 20. A by-pass channel 46 is disposed between the chamber 43 and the channel 18 parallel with the non¬ return valve 12, the by-pass channel 46 being exposed when the piston is retracted out of the recess 30 in a position which corresponds to low or no fuel supply. The apparatus illustrated in Fig. 2 functions as follows. When the engine speed reduces in relation to the initial value set by the operator (for example the full-throttle position shown in the figure by solid lines), as a result of increased load, the governor arm 8 strives to urge the piston 11 in the recess 30. Excess pressure is thereby created in the chamber 43, the non-return valve 12 closing and damping of the throttle-up movement being realised. The arrow with the - and + signs for movement ofthe actuator rod 2 has the same significance as disclosed for the corresponding arrow in Fig. I. On throttle-back movement, a partial vacuum is correspondingly created in the chamber 43 as a result of the outgoing movement of the piston 11 in. the recess 30, the non-return valve 12 opening and the damping being disengaged. In the region ofthe movement ofthe actuator rod 2 from the left-hand end position depicted by ghosted lines to the position depicted by broken lines where fuel begins to be supplied, the by-pass channel 46 is exposed by the piston 11, since it is then in the retracted position. Analogous with the embodiment illustrated in Fig. 1, the damping is thus disengaged in this regulation interval. At large setting forces, high pressure occurs in the chamber 43 as a result of the flow resistance in the throttle, this resulting in the spring-biased valve 40 opening. Once communication between the chambers 20 and 43 is established, the damping ceases and the throttle-up movement may be rapidly effected. Fig.3 shows a damping device according to a third embodiment ofthe present invention. It displays similarities with the damping device illustrated in Fig. 1, details and fittings in each respective damping device which directly correspond to one another having been given the same reference numeral in both of the figures. This damping device consists of a housing 17 with a cylindrical recess 30. A piston 11 is accommodated in the recess 30 and, by means of a linkage 42, is pivotally connected to a governor arm in a corresponding manner as the spring 10 in Fig. 1 is mounted. The side ofthe piston 11 facing away from the linkage 42 defines, together with the walls of the recess 30, a first oil chamber 13, and a non-return valve 52 is disposed in a second oil chamber 20 in a second recess. This valve consists of a cylindrical valve body which is urged towards closed position against a valve seat 54 by a slack spring 51 and opens when the compressive force in the chamber 13 overcomes the spring force and the compressive force in the chamber 20. In the cylindrical valve body, there is provided a valve member 55 whose disc¬ shaped valve body - pretensioned by a spring 50 - abuts against that side of the cylindrical valve body which is turned to face the first oil chamber 13. The disc-shaped valve body is provided with apertures 56 which act as throttle passages between the first oil chamber 13 and the second oil chamber 20. An abutment member 15 in accordance with Fig. 1 is also provided in the housing 17. The damping device illustrated in Fig.3 functions as follows, this also agreeing with that described above with reference to Fig. 1. On throttle-up occasioned by increased engine load, the piston 11 moves outwardly and the non-return valve 52 is closed. Pressure medium flowsthrough the apertures 56 in the valve member 55 and damping of this movement takes place. If the throttle-up force exceeds a certain level, the spring-biased valve member 55 opens and the damping is disengaged. Conversely, on throttle-back as a result of reduced engine load, the non-return valve 52 opens. The valve member 55 also accompanies this movement. Fig.4 shows yet a further embodiment ofthe centrifugal governor damping device according to the present invention. Corresponding parts in the embodiments according to this and preceding figures have been given the same reference numerals. The non-return valve 62 is opened like the non¬ return valve 52 in Fig. 3 on excess pressure in the chamber 13 against the action of a slack spring 61. Channels 66 are provided in the non-return valve body which connect the first and second chambers 13 and 20, respectively, and which function as throttles. A lifting device 60 is disposed in a second cylindrical recess 70 in the housing 17 and consists of a piston 63 and a rod 64 secured thereto and running, at its end facing the chamber 13, through a central aperture in the non-return valve body. This end is of a diameter which is larger than that ofthe central aperture in order to allow the piston 63 and the rod 64, on upward movement, to lift the non-return valve 62 from its seat. A third oil chamber 65 is provided above the end of the piston 63 facing away from the non-return valve 62, this third chamber being placed under a control pressure. When it is intended that the damping be disengaged on throttle-up, the chamber 65 is depressurized by an activation device 57 which is controlled by a signal from a temperature sensor 58 and/or a device 59 sensing the instantaneously injected fuel volume. The activation device 57 may be a thermostat or a microcomputer controlled solenoid valve. The lifting device 60 then lifts the non-return valve 62 from its seat with the aid of a pretensioned spring 67. Alternatively, the non-return valve may be directly controlled by a microcomputer with a solenoid, without any control pressure circuit. Th e present invention should not be considered as restricted to the embodiments described in the foregoing and shown on the Drawings. For example, such embodiments may be deemed to fall within the spirit and scope of the present invention as arise from combinations of solutions to the problems inherent in cold engine start and in idling, respectively, which were not disclosed above in the body of this specification. Moreover, the single- acting devices (12, 18, 51, 52, 61, 62) included in the damping device may consist of a plurality of channels each with one non-return valve means.

Claims: CLAIMS 1. A centrifugal governor (1) for a prime mover, preferably an internal combustion engine, with a damping device (4) susceptible to influence the movement of an actuator rod (2), characterised in that a piston (11) included in the damping device (4) and connected to the actuator rod (2) is disposed in a recess (30) and defines a first pressure medium chamber (13, 43), throttle means (14, 44, 56, 66) being provided in at least one channel (18, 19) between the first pressure medium chamber (13, 43) and a second pressure medium chamber (20); that the damping device (4) is intended to avoid resonance frequencies incorporated in a governor system included in the internal combustion engine for governing an injection pump included in the engine, and influences substantially only the throttle-up movement of the actuator rod (2) by the intermediary of single-acting devices (12, 18, 52, 62) included in the damping device; and thatthe single-acting devices (12, 18, 52, 62) included in the damping device (4) consist of at least one channel (18) with non-return valve means (12, 52, 62) disposed therein, said channel (18) connecting the first and second pressure medium chambers (13, 43, 20 respectively) with each other. 2. The centrifugal governor as claimed in Claim 1 , characterised in that the damping device (4) is provided with means (10, 15, 40, 46, 50, 55, 60) which reduce the damping if the throttle-up movement ofthe actuator rod (2) takes place rapidly or from a position in the interval between an idling position and a position for fuel supply shut-off. 3. The centrifugal governor as claimed in any one of Claims 1 or 2, characterised in thatthe piston (11) is, in a region between the idling position and the position for fuel supply shut-off, influenced by an abutment member (15) with spring means (16) for counteracting damping on throttle- up movement of the actuator rod (2). 4. The centrifugal governor as claimed in any one of Claims 1 or 2, characterised in thatthe piston (11), in a region between the idling position and the position for fuel supply shut-off, exposes a channel (46) which thereat connects the first chamber (43) with the second chamber (20). 5. The centrifugal governor as claimed in any one of Claims 1 or 2, characterised by valve means (60) between the first chamber (13) and the second chamber (20), an activation device (57) which, on a signal from a device (59) sensing the instantaneously injected fuel volume, causing said 5 valve means (60) to open when the injected fuel volume is less than a predetermined value. 6. The centrifugal governor as claimed in any one of Claims 1 to 5, characterised in that a spring (10) is secured at the side ofthe piston (11) o facing away from the first chamber (13), said spring acting, on large throttle up forces representing snap throttle-up, as an extension spring, but otherwise as a rigid link. 7. The centrifugal governor as claimed in any one of Claims 1 to 5, 5 characterised by a by-pass channel (31 ) disposed between the first (43) and the second chamber (20), and provided with a valve (40) which opens if the thrattle-up force exceeds a certain value. 8. The centrifugal governor as claimed in any one of Claims 1 to 5, 0 characterised by valve means (60) between the first chamber (13) and the second chamber (20), an activation device (57) which, on a signal from a temperature sensor (58), causing said valve means (60) to open when the temperature ofthe pressure medium is less than a certain value.

Inventors: MAGNUSSON GOERAN, MAGNUSSON, GOERAN
Applicants: SAAB SCANIA AB, SAAB-SCANIA AKTIEBOLAG
Application year: 1990
Main classification: F02D1
IPC codes: F02D1, G05D13