JP5866225B2 - Hydraulic pumps, especially fuel pumps - Google Patents

Description

  The present invention relates to a hydraulic pump, particularly a fuel pump. In particular, the present invention has been developed with respect to a hydraulic pump provided with a device for adjusting the flow rate.

  In the technical field of hydraulic pumps, in particular fuel pumps, it is necessary to adjust the flow rate of the fluid discharged by the pump to the user in a manner that is substantially independent of the rotational speed of the pump shaft.

In particular, in the field of compression-ignited internal combustion engines (road vehicle engines or large stationary engines used at sea), in fact, all known solutions are all accumulators of pressurized fluids (generally “common rails” Assume a hydraulic connection of the fuel pump to the rail). Also, the adjustment of the flow rate discharged to the common rail by the pump can be substantially obtained by two different methods. That means
A method with a control valve that stacks the excess flow that was discharged by the pump and supplied through the common rail but was not consumed by the fuel injector, or
A method by a laminating valve set at the inlet of the pump to cause controlled cavitation in the fluid drawn by the pump itself.

  Obviously, the latter method is aimed at reducing the mass of liquid sucked into the pump.

  However, despite the unmistakable simplicity, the above adjustment method presents a clear disadvantage.

  The first method of conditioning is energetically very expensive as long as the resulting fluid stack is accompanied by high energy losses.

  The second method of adjustment represents a major problem of wear related to cavitation induced in the fluid at the inlet of the pump. Furthermore, the above solution requires the use of an electric stacked valve with an expensive proportional solenoid so that the continuity and accuracy of the flow rate of fluid drawn by the pump can be varied.

  The object of the present invention is to solve the technical problems mentioned above.

  In particular, it is an object of the present invention to regulate the flow rate delivered to the user by the hydraulic pump in an energetically convenient manner and not to compromise the useful life of the pump or pump components.

  The object of the invention is achieved by a hydraulic pump having the features forming the subject of the claims. The following claims form an integral part of the technical disclosure provided herein in connection with the present invention.

  The invention will now be described with reference to the accompanying drawings, given purely by way of non-limiting example.

1 is a schematic view of a hydraulic pump according to various embodiments of the present invention. It is the schematic of the hydraulic pump which concerns on one Embodiment of this invention. 1 is a schematic view of a hydraulic pump according to a preferred embodiment of the present invention. It is a graph for showing the various characteristic operation amount of the hydraulic pump which concerns on suitable embodiment of this invention. It is a graph for showing the various characteristic operation amount of the hydraulic pump which concerns on suitable embodiment of this invention. It is a graph for showing the various characteristic operation amount of the hydraulic pump which concerns on suitable embodiment of this invention. It is a graph for showing the various characteristic operation amount of the hydraulic pump which concerns on suitable embodiment of this invention. It is a graph for showing the various characteristic operation amount of the hydraulic pump which concerns on suitable embodiment of this invention.

  In FIG. 1, the symbol HP indicates a hydraulic pump according to various embodiments of the present invention. The pump HP includes a suction port IP, a discharge port DP, and at least one cylinder CY. A piston P that reciprocates by a mechanism K (for example, a cam mechanism or a crank mechanism) is provided in the cylinder CY. This mechanism K is also driven by the input shaft IS. Each piston P reciprocates between top dead center TDC and bottom dead center BDC.

  The intake port IP is arranged for connection to an intake environment (not shown) and is in fluid communication with the cylinder CY via a known intake valve IV.

  The cylinder CY is further fluidly connected to the discharge port DP via the discharge line DL. The discharge line DL is provided with a discharge valve DV that can be controlled by a regulation assembly R.

  The discharge valve DV has an open position, that is, a position where fluid can flow between the cylinder CY and the discharge port DP, and a closed position, that is, a position between the cylinder CY and the discharge port DP. It is possible to operate between positions that prevent fluid from flowing between them. The pump HP is further arranged for hydraulic connection to the user. Here, the user is schematically represented and indicated by the letter U. In one embodiment, the user U may be a fuel pressure injection system well known as a “common rail fuel injection system”.

  The operation of the pump HP is as follows.

The piston P that reciprocates between the top dead center TDC and the bottom dead center BDC describes a work cycle having a sequence of five strokes. That is,
Inhalation (inhalation) of fluid, particularly liquid, from the intake port IP into the cylinder CY,
Compression (compression) of the liquid in the cylinder CY,
Discharge (discharge) of liquid to the discharge line DL;
Reflux of liquid from the discharge line DL to the cylinder CY (reflux),
This is expansion (expansion) of the remaining liquid existing in the cylinder CY.

  Of the five strokes, the compression stroke and the discharge stroke substantially occur while the piston rises from the bottom dead center BDC to the top dead center TDC. In contrast, the reflux stroke, the expansion stroke, and the suction stroke substantially occur while the piston descends from the top dead center TDC to the bottom dead center BDC. In the following description, the former is referred to as “up stroke” and the latter is referred to as “down stroke”.

  During the expansion stroke, the piston P descends to the bottom dead center BDC, whereby the pressure in the cylinder CY decreases, and the suction valve IV is opened by the decrease in the pressure. Therefore, as a result, the fluid flows into the cylinder CY itself, and the suction stroke starts. The intake valve IV is substantially closed again at the end point of the downward stroke of the piston P.

  Then there is a compression stroke. When the pressure in the cylinder CY reaches such a value that the adjusting device R opens the discharge valve DV, this compression stroke ends. Therefore, the pressurized fluid can be sent to the discharge port DP through the discharge line DL.

  For this purpose, the adjusting device is designed to receive the first drive signal PS1. The adjusting device preferentially corresponds to the discharge pressure immediately downstream of the cylinder CY, and transmits a drive signal AS1 to the discharge valve DV in response to the drive signal PS1. Here, the drive signal AS1 is an acting force generated by, for example, a mechanical actuator or hydraulic means. Due to the acting force acting on the discharge valve DV, the discharge valve DV is opened. As a result, the fluid passes through the discharge line DL and can be discharged to the user U through the discharge port DP.

  At the end of the discharge stroke, the adjusting device R can stop issuing the drive signal AS1 and close the discharge valve DV.

  When the flow rate of the fluid sent to the user U by the pump HP exceeds the latter requirement, the pressure of the fluid in the user U (and the discharge port DP) increases due to fluid accumulation.

The adjusting device R receives the second drive signal PS2 corresponding to the pressure of the fluid in the user U. If the detected pressure in the user U is greater than the threshold value p _REF , the adjusting device R will maintain the force acting on the discharge valve DV and, similarly, after the discharge stroke has ended, The drive signal AS1 is continuously output so as to keep the valve DV in the open position. That is, the adjusting device R keeps the discharge valve open during at least a part of the downward stroke of the piston P.

  Thus, the fluid can recirculate from the discharge port DP to the cylinder CY through the discharge valve DV. It should be noted that while the fluid is recirculating to the cylinder CY, this recirculation is the driving force for the work on the piston P and substantially returns to the compression work previously accumulated by the fluid. As a result, the adjustment mechanism assumes that the maximum flow rate of the fluid is discharged and causes an excessive amount of return to the cylinder CY, which is not detrimental to the overall energy efficiency of the pump.

  In effect, the recirculation stroke performed by the piston P (substantially undesirable result due to the inertia of the system (especially the discharge valve) in the state of operation at the maximum flow rate) Over and over the wider angular range (with respect to the rotation angle of the input shaft IS) that extends within the limits to the bottom dead center BDC, resulting in the resulting and resulting consequences (and therefore with a delay in the intake stroke and substantial reduction) A substantial extension of the reflux process is revealed).

Thus, the pressure of the fluid in the user U decreases (similar to the pressure at the discharge port DP) and returns to the vicinity of the value of the threshold value p _REF . Therefore, when the pressure of the fluid in the user U decreases until it becomes smaller than the threshold pressure p _REF , the adjusting device R is designed to stop maintaining the drive signal AS1 of the discharge valve DV, and as a result, the valve The DV can be closed again.

  The operation of the adjustment device R is an adjustment state in which the pressure of the fluid in the user U oscillates with respect to a reference value by repeating the adjustment process just described. In this way, it can be continuously ensured that a flow value equal to the desired flow value reaches the user U.

  With reference to FIG. 2, in one embodiment, the pump HP comprises an actuator A1 adapted to drive the discharge valve DV and an elastic positioning element S that tends to bring the discharge valve DV to the closed position. Yes.

  The operation is the same as described above. This is because the adjusting device R takes the discharge valve DV to the open position during the discharge stroke (in response to the drive signal PS1), and during the return stroke, the drive signal PS2, that is, the user U's It is designed to control the actuator A1 in order to keep the discharge valve DV open according to the pressure.

  With reference to FIG. 3, reference numeral 1 generally indicates a hydraulic pump according to a preferred embodiment of the present invention.

  A schematic diagram represented by a broken line and a two-dot chain line shows the main body of the hydraulic pump 1. The hydraulic pump 1 includes a suction port 2 and a discharge port 4.

  The first manifold channel 6 is fluidly connected to the suction port 2. In this embodiment, the first suction line 8, the second suction line 10, and the third suction line 12 branch from the first manifold 6, which are connected to the manifold 6 and the fluid. Connected.

  The suction lines 8, 10, and 12 are provided with a first suction valve 14, a second suction valve 16, and a third suction valve 18, respectively. The intake valves 14, 16, 18 allow fluid connection between the corresponding intake lines 14, 16, 18 and each of the first cylinder 20, the second cylinder 22 and the third cylinder 24, or It is supposed to be impossible.

  The movable ones in the cylinders 20, 22, 24 are a first piston P1, a second piston P2, and a third piston P3. Each piston P1, P2, P3 is driven to reciprocate by a certain mechanism.

  In the particular case analyzed here, the three cams C1, C2, C3 (with corresponding tappets) are given a uniform offset in a certain angular direction.

  In an alternative embodiment, a pump 1 with a piston driven by a crank mechanism can be supplied.

  It should be further noted that the embodiment of the pump 1 described here is by way of example a three-piston type, but those skilled in the art will recognize that the present invention applies regardless of the number of pistons in the pump 1. Will understand. Here, the number of pistons of the pump 1 may be one instead of three.

  In addition to fluid connection with the corresponding intake lines 8, 10, 12 and corresponding intake valves 14, 16, 18, each cylinder 20, 22, 24 has a first discharge valve 26, a second discharge, respectively. The valve 28 and the third discharge valve 30 are fluidly connected. Each of the first discharge valve 26, the second discharge valve 28, and the third discharge valve 30 is movable between a closed position and an open position.

  Each discharge valve 26, 28, 30 is fluidly connected to a second manifold channel 38 by discharge channels 32, 34, 36, respectively, and the second manifold channel 38 is similarly fluidly connected to the discharge port 4. .

  Each discharge valve 26, 28, 30 is normally in the closed position. When each discharge valve 26, 28, 30 is in the open position, the corresponding cylinder 20, 22, 24 in fluid communication with each discharge valve 26, 28, 30 is fluidly connected to the corresponding discharge channel 32, 34, 36. Designed to be able to. Therefore, the fluid can flow from the corresponding cylinder 20, 22, 24 to the discharge port 4. In the closed position, each discharge valve blocks the fluid flow.

  Each discharge valve 26, 28, 30 is regulated by a number of drive signals, resulting in a corresponding drive force. In the embodiment described here, the driving force is obtained by a hydraulic drive line or, more simply, a drive line. In other embodiments, the drive can be obtained by an actuator acting mechanically (instead of hydraulic pressure) on the corresponding discharge valve.

  With respect to the embodiment illustrated in FIG. 3, each discharge valve 26, 28, 30 includes a first hydraulic drive line U1, U2, U3 fluidly connected to a corresponding cylinder 20, 22, 24, respectively, 2 hydraulic drive lines CV1, CV2, CV3 and third hydraulic drive lines D1, D2, D3 fluidly connected to the corresponding discharge channels 32, 34, 36. It should be noted that the drive line is incidental. As a result, in some embodiments, for example as described herein, the pump 1 comprises drive lines D1, D2, D3, while in other embodiments the drive lines U1, U2, U3 and Only CV1, CV2 and CV3 exist.

  Each discharge valve 26, 28, 30 is further provided with each elastic element S1, S2, S3. The action of each elastic element S1, S2, S3 is aimed at maintaining the corresponding discharge valve in the closed position. The force generated by each elastic element S1, S2, S3 is selected in such a way that the force generated by the hydraulic drive line can be substantially ignored.

  In this specification, as will be apparent to those skilled in the art, the terms “hydraulic drive line” or “drive line” are used to collectively indicate a hydraulic line having a drive function. That is, the hydraulic line can generally handle a negligible flow rate of fluid. In the hydraulic line, the pressure of the fluid in the hydraulic line is used as a hydraulic type signal in a component or circuit.

  The first and second drive lines U1, U2, U3 and D1, D2, D3 (if present) open the corresponding discharge valves 26, 28, 30 and therefore the corresponding discharge valves 26, 28. , 30 acting on each surface of influence.

  The hydraulic drive lines CV1, CV2, and CV3 are intended to maintain the corresponding discharge valve in the closed position, as in the elastic elements S1, S2, and S3 (not so much as described above). Produce.

  Furthermore, each hydraulic drive line CV1, CV2, CV3 is the affected area where the remaining hydraulic drive lines of the corresponding discharge valve, ie, drive lines U1, U2, U3 and D1, D2, D3 (if present) act. It acts on each affected area that has been preferentially chosen to be substantially equal to the sum of.

  Hydraulic drive lines CV1, CV2, and CV3 branched from the adjustment channel CV0 are fluidly connected to the control volume CV. The control volume CV is fluidly connected to the second manifold channel 38 and the discharge port 4 by a hydraulic control line 39, and acts on a choke 40 having a shape fixed with priority. The choke 40 is provided upstream of the hydraulic system of the control volume CV.

  The control volume CV is further connected to the first manifold channel 6 and the suction port 2 by a control valve 42 provided fluid-dynamically downstream of the return channel 43 fluidly connected to the suction port 2. Is fluidly connected.

  The control valve 42 is functionally a pressure regulating valve. The pressure regulating valve in this embodiment is maintained in the closed position by the elastic element S4. Furthermore, in this embodiment, the control valve 42 can be driven by a solenoid 44 operably connected to an electrical control unit 46.

  In other embodiments, a hydraulic or mechanically driven control valve 42 may be employed.

  Thus, in this embodiment there is a defined adjustment device of the pump 1 comprising a hydraulic control line 39, a choke 40, a control volume CV and a control valve 42 (and in this embodiment also a control unit 46). This adjustment device allows the pump 1 to vary the flow rate delivered to the user connected to the discharge port 4, as will become clear from the following description.

  The operation of the pump 1 is described below.

  The following description will be made with particular reference to the application of a hydraulic pump 1 to a fuel injection system of an internal combustion engine, in particular a high pressure pump for a stored fuel injection system (so-called “common rail” fuel injection system). Of course, it is possible to carry out what is described here even for a general user connected to the discharge port 4.

  The suction port 2 is fluidly connected to a low pressure environment LPE that is fluidly arranged upstream. The low pressure environment LPE contemplated for this application comprises, for example, a hydraulic inflow line, in which the fuel is gently pressurized by a low pressure pump that draws fuel directly from the tank.

  The discharge port 4 is one or more fuel injectors (not shown) instead of being fluidly connected to a fuel accumulator commonly referred to as a “common rail” (represented schematically and indicated by the reference CR). Are fluidly connected. With respect to the mode of operation of the injector in the common rail fuel injection system, reference shall be made to a specific document, as long as the operation of this subsystem is widely known to those skilled in the art.

  During the operation of the pump 1, the input shaft IS is rotationally driven and drives the pistons P1, P2, P3 by reciprocating movements thanks to the cams C1, C2, C3.

  Operation without adjusting the total flow rate, i.e., the flow rate discharged to the common rail CR, is a prejudice to the fact that the operation of the further piston and the operation of the same type of activatable parts associated with the piston are identical. It will be described with particular reference to parts related to P1.

References are further described in the diagrams shown in FIGS. Each of FIGS. 4 to 8 shows an evaluation of the feature quantity related to the operation of the pump 1 as a function of the rotation angle of the input shaft IS, as indicated by CA _IS . More details are as follows.

The graph of FIG. 4 has three distinct curves, which are plots of the position S of each piston (respectively P1, P2, P3) shown as a percentage of the total stroke (denoted S _MAX ). Represents. Accordingly, each curve is given the same reference number as the corresponding piston reference number.

The graph of FIG. 5 has three distinct curves that represent the opening DVL (shown as a percentage of the maximum opening value DVL _MAX ) of each discharge valve 26, 28, 30. Yes. Accordingly, each curve is given the same reference number as that used for the corresponding discharge valve.

The graph of FIG. 6 has three distinct curves that are shown as a percentage of the flow rate Q _DV passing through each discharge valve 26, 28, 30 (maximum flow rate value Q _{DV, MAX} ). Represents the plot. Accordingly, each curve is given the same reference number as that used for the corresponding discharge valve.

The graph in FIG. 7 shows a plot of the pressure in the common rail CR, expressed as p _CR (expressed as a percentage of the threshold pressure p _REF ). This _pCR is further substantially equal to the pressure at the discharge port 4.

The graph of FIG. 8 shows a plot of the instantaneous flow rate Q _P passing through the discharge port 4 (that is, the flow rate discharged to the common rail CR).

  Each piston P1, P2, P3 represents a work cycle having 5 strokes in the same manner as described above for piston P. Each piston P1, P2, P3 reciprocates to change the volume of the fluid chamber defined by the corresponding cylinder 20, 22, 24, and moves between top dead center TDC and bottom dead center BDC. Is possible.

  The angle range of the observation is a method having an origin coinciding with the top dead center TDC of the piston P1, and a lot of work sufficient to show the transition from the full flow rate operating state to the operating state in the flow rate regulation (regime) A method is selected that covers the cycle.

  Starting from the origin of the axis of the graph of FIG. 4, the piston P1 is in a position corresponding to the top dead center TDC. Here, the reflux stroke starts. These conditions are due to the inertia of the discharge valve causing a delayed closure of the discharge valve with respect to top dead center TDC. The expansion stroke follows, causing a pressure drop in the cylinder 20 while the piston P1 is lowered to the bottom dead center BDC. When the pressure reaches a value lower than the pressure inside the low pressure environment LPE, the intake valve 14 opens, so that the cylinder 20 passes from the low pressure environment LPE through the first manifold channel 6 and the first intake channel 8. Fluid flows into the.

  When the piston P1 reaches the bottom dead center BDC, the suction stroke is substantially finished. When the suction valve 14 is closed, the capacity 20 is isolated from the low pressure line 8 and the piston rises to the top dead center TDC causes the fluid in the cylinder 20 to be compressed (compression stroke). Referring to FIG. 6, the point that should be noted is that the flow rate through the discharge valve 26 is zero during the compression stroke.

  The compression of the fluid in the cylinder 20 causes the discharge valve 26 to open in the manner described below (the start of the discharge stroke).

The discharge valve 26 depends on the action of the first drive line U1, the second drive line CV1, and the possible third drive line D1. The drive line U1 is the corresponding region of influence, the pressure in the cylinder 20 _{(hereinafter,} represented by _{p 20. Similarly, p 22} and _{p 24} are. For use in the cylinder 22, 24) substantially corresponds to the Transmit pressure signal to That is, information about the discharge pressure of the cylinder 20 immediately downstream and immediately upstream of the corresponding discharge valve 26 is substantially transmitted.

The drive line CV1 transmits a pressure signal corresponding to the pressure in the control volume CV (hereinafter, indicated by p _CV ) to the corresponding influence region.

If present, the drive line D1 transmits a pressure signal corresponding to the pressure acting on the discharge port 4 to the corresponding affected area. In this case, this pressure is the pressure in the common rail CR (hereinafter, indicated by p _CR.) Substantially equal. The common rail CR is actually fluidly connected to the discharge port 4. Similarly, the discharge port 4 is fluidly connected to the discharge line 32 by the second manifold channel 38.

  It should be noted that the actuation force associated with the hydraulic drive line D1, in some embodiments, can exert a force on the fluid within the discharge valve, which can exert a force on the moving element of the discharge valve itself. That can result in the geometry of the discharge valve that feeds to.

  As long as there is no flow through the hydraulic control line 39, the control volume CV is in a stagnant environment in this operating state. This is because the control valve 42 is in a completely closed position.

  Thus, there is a static pressure transmission between the common rail CR and the control volume CV. This is because the choke 40 does not cause any pressure drop. There is almost no passage through the choke 40 to the control volume CV.

This means that the pressure p _CV is equal to the pressure p _CR , so that the pressure signal transmitted by the drive line CV1 is identical to the pressure signal transmitted by the drive line D1.

In effect, at full flow operating conditions, the discharge valve 26 can be incorporated into a conventional check valve. That is, the discharge valve 26 has a pressure p _CV (which is equal to the pressure p _CR in these conditions) by an amount sufficient for the pressure in the cylinder 20 (p ₂₀ ) to overcome the contrast effect of the elastic element S1. Will remain open until exceeded. Here, the certain amount can be represented by an equivalent pressure, as is well known. That is, the difference between the pressure p _20, equivalent pressure associated with the elastic element S1 is must be greater than the pressure p _CR.

  The operation of the discharge valves 28 and 30 is the same. Of course, the above matters are out of phase with respect to the discharge valves including the discharge valve 26 due to the timing of the pistons P1, P2, P3 set by the cams C1, C2, C3.

  With respect to FIG. 5, it can be further seen in the graph how the discharge valves 26, 28, 30 open.

  The opening of each discharge valve starts at the end point of the compression stroke performed by the corresponding piston, and ends at some point after the top dead center TDC at the end point of the reflux stroke.

Once the first work cycle in the range of angles considered for this description is complete, the pressure _pCR increases and becomes very close to the threshold value _pREF (FIG. 7).

  Basically, the excess flow discharged to the common rail CR by the pump 1 is not consumed by the injector connected to the common rail CR, and the fluid that raises the pressure level in the common rail CR and finally the discharge port 4 It becomes accumulation of.

Referring to FIGS. 4 to 8, particularly FIG. 7, the threshold pressure p _REF is exceeded at the rotation angle _{CAIS, R.}

Exceeding the threshold pressure p _{REF in} the common rail CR is detected in this embodiment by the electrical control unit 46, that is, by a known type of pressure sensor portion operatively connected to and attached to the common rail CR ( The functional representation schematically showing the operable connection between the sensor part and the control unit 46 is represented by a dashed line and a dash-dot line added to the control unit 46 and the common rail CR as well as the reference symbol PRS. Indicated by.)

In the situation described above, flow paths are provided in the control line 39 from the discharge port 4 through the choke 40 to the control volume CV and from the control volume CV through the return line 43 to the manifold channel 6. By the flow path through the choke 40, to lower the value of the pressure p _CV to below to ensure the value of the pressure p _CR.

  The presence of the choke 40 allows the adjustment to be made with a very small discharge flow compared to the flow through the pump, which is advantageous for the hydraulic efficiency of the pump itself.

When the pressure _{p CR} in the common rail CR exceeds a threshold pressure _{p REF,} adjusting device of the pump 1, the pressure _{p CV} in the control volume CV adjusts the valve 42 so as not to exceed the threshold pressure _{p REF.} That is, once the threshold pressure p _REF in the user (in this case, the common rail CR) connected to the discharge port 4 of the pump 1 is exceeded, the pressure in the control volume CV is adjusted and is at most the same as p _REF. In order to limit the pressure in the control volume CV to be a value, the control valve 42 is provided.

In general, any known means designed to adjust the pressure in the control volume CV can be used to increase the pressure in the control volume CV to activate the adjustment mechanism described herein. The threshold (p _REF in this embodiment) is prevented from exceeding.

The discharge valve 30 is always affected by the action of the hydraulic drive lines U3, D3 (if present) and CV3. However, now, the pressure signal transmitted to the valve 30 by the drive line CV3 is drive line U3 (and, if D3 is present if) (always equal to the pressure p _CR.) Transmitted pressure signal by less than. Accordingly, the conditions for balancing the discharge valve 30 change, and as a result, the discharge valve 30 is kept open even when the pressure p ₂₄ drops below the pressure (p _CR ) in the discharge environment. That is, the discharge valve 30 is maintained in the open position during at least a part of the downward stroke of the piston P3.

This leads to reflux of fluid from the discharge port 4 to the cylinder 24 and ultimately causes a decrease in pressure p _CR in the common rail CR for reduction of fluid accumulation.

  When the pressure in the common rail CR reaches a pressure level in the control volume CV, the discharge valve 30 is closed, and in the corresponding cylinder 24, the expansion stroke of the fluid contained in the cylinder 24 is before the suction stroke. To start.

Therefore, the adjusting device of the pump 1 is configured to substantially maintain the discharge valve 30 (and the discharge valves 26 and 28 at the scheduled timing) in an open state following the discharge stroke. That is, the adjusting device of the pump 1 adjusts the pressure p _CV (related to the drive lines CV1, CV2, CV3) during at least a part of the downward stroke of the piston P3, and in particular, the threshold pressure p _REF is the discharge port. If the pressure is exceeded in a user fluidly connected to 4 (in this case the common rail CR), the pressure p _CV is limited to the value of the threshold pressure p _REF .

  That is, with the regulation system proposed here, during full flow operating conditions, each discharge valve essentially corresponds to the discharge stroke (the return stroke is virtually negligible), and less than half the work cycle. Maintain the open state for a while. In the adjustment state, the closing instant is instead clearly delayed, resulting in an additional angular range of the open state. Here, it can be seen that the recirculation of the flow rate through the discharge valve 30 increases (the point of the curve with a negative ordinate), which means that a considerable amount of recirculation of fuel returning to the cylinder 24 has occurred. Show.

  During this stroke, as described above, excessive work of compression that occurred in the previous discharge stroke, i.e., the fluid returns to the pump, thus ensuring a good level of energy efficiency of the overall system.

  Of course, the same applies to the discharge valves 26 and 28 at the scheduled timing. Basically, adjustment of the flow rate delivered by the pump 1 is obtained by the return of fluid (especially fuel) to the discharge of each piston.

ここで、Δｐは、コモンレールＣＲ内の過剰圧力、Ｖ_cylは、ポンプのユニット変位、Ｖ_railは、コモンレールＣＲの内部容量、Ｅは、流体の弾性係数である。 With respect to FIG. 7, the following should be further noted. In other words, the adjustment method described in this specification functions under the condition that it can withstand an excessive pressure in the common rail CR (or generally in a user connected to the discharge port 4). By simplifying the process (which is important for the purpose of the description to understand what the contained physical quantity is), the maximum overpressure that is to be tolerated is equal to :

Here, Δp is an excess pressure in the common rail CR, V _cyl is a unit displacement of the pump, V _rail is an internal capacity of the common rail CR, and E is an elastic coefficient of the fluid.

Finally, with respect to Figure 8, plotted as a function of angle CA _IS, curves of instantaneous flow rate Q _P discharged by the pump 1 through the discharge port 4 is shown. The value of the flow rate Q _P is, Q _P, are expressed as percentage of the maximum flow rate value indicated by _MAX. It should be noted here that with respect to FIG. 6, as already pointed out on the other hand, a significant increase in the angular range (see angle _{CAIS, R} ), the value of the flow has a negative sign, ie during adjustment. Backflow and fluid return to the cylinder (s) operatively associated with the discharge valve.

  The pump 1 according to the invention thus provides a series of considerable advantages over known types of pumps.

  First of all, the pump 1 makes it possible to eliminate the need for expensive regulation by stacking in the discharge part, or the need for dangerous regulations by stacking in the suction part. It is the cause of the problems leading to cavitation in the fluid caused by it.

  Furthermore, the control device of the pump 1 is easy to manage and can also adjust the threshold pressure in the common rail CR in a simple manner by acting on the open calibration / threshold of the control valve 42.

  The flow consumed by the control system is much smaller and substantially negligible compared to the flow typically flowed by the pump 1. This minimizes the impact of the operation of the control system on the operation of the pump 1 itself.

  Of course, as defined by the appended claims, the details of the configuration and the embodiments may differ significantly from those described and illustrated herein as non-limiting examples.

Claims (6)

A suction port (IP; 2);
A discharge port (DP; 4) arranged for hydraulic connection to the user (U; CR);
At least one cylinder (CY; 20, 22, 24),
The cylinder (CY; 20, 22, 24) has a corresponding piston (P; P1, P2, P3) that is movable in the cylinder, and this piston is at top dead center (TDC) during pump operation. ) And bottom dead center (BDC)
A discharge valve (DV; 26, 28, 30) for the cylinder (CY; 20, 22, 24) hydraulically connected to the cylinder (CY; 20, 22, 24);
The discharge valve (DV; 26, 28, 30) is movable between a closed position and an open position. In the open position, the discharge valve (DV; 26, 28, 30) is moved to the cylinder (CY). 20, 22, 24) and the discharge port (DP; 4) so that fluid can flow, and in the closed position, the discharge valve (DV; 26, 28, 30) The fluid is prevented from flowing between the cylinder (CY; 20, 22, 24) and the discharge port (DP; 4).
During pump operation, the discharge valve is in the open position in part during the movement of the piston (P; P1, P2, P3) from the bottom dead center (BDC) to the top dead center (TDC), In the hydraulic pump (HP; 1), which is closed after the top dead center (TDC) of the reciprocating motion of the piston (P; P1, P2, P3),
The hydraulic pump (HP; 1) includes an adjusting device (R; 39, 40, 42, 43, 44, 46), and the adjusting device (R; 39, 40, 42, 43, 44, 46) The piston from the top dead center (TDC) to the bottom dead center (BDC) when the threshold pressure (p _REF ) in the user (U; CR) hydraulically connected to the discharge port (DP; 4) is exceeded The discharge valve (DV, 26, 28, 30) is maintained in the open position during at least part of the movement of the valve, thereby delaying the closing of the discharge valve (DV; 26, 28, 30), the discharge port (DP; 4) fluid from into the cylinder (20, 22, 24) are adapted to allow for reflux,
The discharge valves (26, 28, 30) are controlled by hydraulic drive lines (U1, U2, U3; D1, D2, D3; CV1, CV2, CV3),
The adjusting device (R; 39, 40, 42, 43, 44, 46)
A control volume (CV) fluidly connected to the discharge port (4) by a hydraulic control line (39), and a choke (40) is provided on the hydraulic control line (39),
The control valve (42) includes a control valve (42 ) for adjusting the pressure (p _CV ) in the control volume (CV), and the control volume (CV) and the suction port ( 2) operable to allow fluid connection between
The hydraulic pump (HP; 1) , wherein the choke (40) is provided upstream of the hydraulic pressure of the control volume (CV ). The hydraulic pump (1) according to claim 1 ,
The hydraulic drive line is
A first signal transmitting to the discharge valve (26, 28, 30) a pressure signal substantially corresponding to the pressure (p20, p22, p24) in the at least one cylinder ( ₂₀ , ₂₂ , ₂₄ ); Hydraulic drive lines (U1, U2, U3);
Second hydraulic drive line for transmitting a pressure signal that substantially corresponds to the pressure _{(p CV)} within the control volume (CV) to the discharge valve (26,28,30) (CV1, CV2, CV3) and the A hydraulic pump (1) characterized by comprising. The hydraulic pump (1) according to claim 2 ,
The control valve (42), the pressure in the control volume (CV) _{(p CV)} is, the discharge port (DP; 4) is fluidly connected to the user (U; CR) in the threshold pressure ( The hydraulic pump (1) is characterized in that when the pressure exceeds (p _REF ), the pressure (p _CV ) is substantially limited to the threshold pressure (p _REF ). The hydraulic pump (1) according to claim 2 ,
The discharge valve (26, 28, 30) transmits a pressure signal substantially corresponding to the pressure (p _CR ) of the discharge port (4) to the discharge valve (26, 28, 30). The third hydraulic drive line (D1, D2, D3) has a drive line (D1, D2, D3) and brings the discharge valve (26, 28, 30) to the open position. A hydraulic pump (1) characterized in that The hydraulic pump (1) according to claim 1 ,
The control valve (42) is operated by an electric control unit (46) adapted to cooperate with a sensor unit for detecting the pressure in the user (U; CR) connected to the discharge port (4). A hydraulic pump (1) characterized in that it is controlled. In the hydraulic pump (1) according to any one of claims 1 to 5 ,
A first piston (P1), a second piston (P2), and a third piston (P3);
Each of these pistons is operatively associated with a first discharge valve (26), a second discharge valve (28), and a third discharge valve (30),
The first, second and third pistons (P1, P2, P3) are driven to reciprocate via the input shaft (IS) of the hydraulic pump (1). Pump (1).

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