JP3893707B2 - Variable discharge high pressure pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable discharge high pressure pump used for pumping and supplying a high pressure fluid, for example, in a common rail injection system of a diesel engine.
[0002]
[Prior art]
A common rail injection system is known as one of systems for injecting fuel into a diesel engine. In the common rail injection system, a common pressure accumulation pipe (common rail) communicating with each cylinder is provided, and the fuel pressure in the pressure accumulation pipe is kept constant by supplying high pressure fuel at a required flow rate by a variable discharge high pressure pump. is doing. The high-pressure fuel in the pressure accumulating pipe is injected into each cylinder by an injector at a predetermined timing (for example, JP-A-64-73166).
[0003]
FIG. 14 is a cross-sectional view of the main part along the central axis showing an example of a conventional variable discharge high-pressure pump used for such applications. In FIG. 14, a plunger 92 driven by a cam (not shown) is fitted into a cylinder 91 so as to reciprocate, and a pressure chamber 93 is formed by the interior surface of the cylinder 91 and the upper end surface of the plunger 92. An electromagnetic valve 94 is attached above the pressure chamber 93, and the electromagnetic valve 94 has a valve body 96 that opens and closes between the low-pressure channel 95 and the pressure chamber 93 formed therein.
[0004]
The valve body 96 is in the valve open position in the state shown in the figure where the coil 97 is not energized, and when the plunger 92 is lowered, the fuel is pressured from the low pressure supply pump (not shown) through the gap around the valve body 96 and the low pressure passage 95. It is introduced into the chamber 93. When the coil 97 is energized, the valve body 96 is attracted upward, and its substantially conical tip is seated on the seat portion 98 to close the valve. At the same time, as the plunger 92 rises, the fuel in the pressure chamber 93 is pressurized and fed to the pressure accumulating pipe from the flow path 99 provided on the side wall of the pressure chamber 93.
[0005]
[Problems to be solved by the invention]
By the way, since the force in the valve closing direction acts on the valve body 96 by the fuel pressure in the pressure chamber 93 while the plunger 92 is raised, once the valve body 96 is closed, the energization to the coil 97 is stopped. Do not open. For this reason, in the variable discharge high-pressure pump having the above-described configuration, the flow rate to be sent to the pressure accumulating pipe is controlled by so-called pre-stroke control that controls the valve closing timing. In other words, after the plunger 92 moves to the ascending stroke, the valve is not closed immediately, but the valve is kept open until the fuel in the pressure chamber 93 reaches a predetermined amount, and excess fuel is released to the low pressure passage 95 side. After that, by closing the valve and starting pressurization, a necessary amount of pressurized fluid is pumped to the pressure accumulating pipe.
[0006]
However, when the oil feed rate of the pump increases as the engine speed increases, there arises a problem that the valve body 96 closes (self-closes) regardless of the valve closing signal. This is because when the plunger 92 is lifted, the valve body 96 directly receives the dynamic pressure of the fuel in the pressure chamber 93 at the lower end surface, and flows from the gap between the valve body 96 and the seat portion 98 toward the low pressure channel 95. This is due to receiving a force in the valve closing direction due to the fuel throttling effect, and there is a risk that the flow rate control will not be performed properly.
[0007]
As measures against this, it is conceivable to increase the operating stroke of the valve body 96 or increase the return spring force of the valve body 96. In either case, the valve closing response is reduced. In order to maintain the valve closing response, it is necessary to increase the power supplied to the coil or to increase the attraction force of the solenoid valve by increasing the physique, which increases the power cost and production cost of the solenoid valve. There was a problem.
[0008]
Further, in the variable discharge high-pressure pump having the above-described configuration, the flow path to the pressure chamber 93 is opened and closed by the electromagnetic valve 94, and is constant until the valve body 96 is seated with respect to the valve closing signal and the flow path is closed. Therefore, this operation response time is usually calculated in advance to control the valve closing timing. However, when the engine speed increases and the oil feed rate of the pump increases, the opening / closing operation is not in time, and there is a risk that sufficient control cannot be performed.
[0009]
FIG. 13 shows a variable discharge high-pressure pump proposed by the present inventors in place of the conventional variable discharge high-pressure pump. FIG. 13A is a cross-sectional view along the central axis, and FIG. It is operation | movement explanatory drawing which shows a mode, a control method, the action | operation of a plunger and a cam roller, and the change of a pumping amount and a drive torque.
Therefore, the present inventors can easily and reliably control the flow rate of pressure feeding to the pressure accumulating pipe even when the engine speed is increased and the pump oil feed rate is high, and the apparatus is increased in size and electric power. In addition, in order to eliminate problems such as response delay caused by using an electromagnetic valve for opening and closing the flow path, the suction metering type pump shown in FIG. 13 has been proposed.
[0010]
However, in the case of the suction metering pump configured as shown in FIG. 13 (A), the cam roller and the cam collide in the normal operation state other than during full pressure feeding, that is, during metering, as shown in FIG. 13 (B). Therefore, there were noise problems and reliability problems.
Further, since the oil feed rate does not change even when metering with a small amount of pumping, the peak driving torque of the pump is the same as when pumping the entire amount.
[0011]
Therefore, the present invention makes it possible to easily and reliably control the flow rate of pressure feeding to the pressure accumulating pipe even when the engine speed increases and the pump oil feeding rate is high, and without increasing the size of the device and increasing the power. Another object of the present invention is to provide a pump that is free from problems such as a response delay of the flow control valve and that does not collide with the cam roller.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides claims 1 to. 7 The technical means described in is adopted.
According to the first aspect of the present invention, only the first check valve that allows the fluid to flow only in the direction from the low pressure flow path to the pressure chamber is provided between the pressure chamber and the low pressure flow path, and the plunger is reciprocated. The cam to be formed has a variable cam profile and is provided with a cam moving means, so that the flow control between the pressure chamber and the low-pressure channel is provided between the suction metering pumps proposed so far. There is no solenoid valve, etc., and all the amount is sucked in and all the amount is pumped, and the amount is controlled by the cam lift amount of the variable cam. There are no noise or reliability problems due to cam roller collision.
[0013]
Claim 1 to 7 According to the invention described in the above, the first throttle is provided between the low pressure flow path and the cam back pressure chamber, and the pump is connected to the cam back pressure chamber via the flow rate control valve that forms the cam moving means. Room Or connected to the return channel.
This is a cam moving means that moves the cam by changing the pressure of the low-pressure fluid flowing into the cam back pressure chamber (changing the cam lift). The pressure in the cam back pressure chamber is the flow rate that flows out of the flow control valve. To adjust the pressure of the cam back pressure chamber (adjust the pressure of the cam back pressure chamber by the balance between the amount flowing in from the low pressure flow path through the first throttle and the amount flowing out from the flow control valve) Is moved to control the suction amount (pressure feed amount).
[0014]
Therefore, since a high pressure does not act on the flow control valve, it may be small and low cost. Further, there is no need to increase the size of the device or increase the power.
Claim 2 According to the invention described in the above, the flow rate control valve that forms the moving means of the cam is provided between the low pressure flow path and the cam back pressure chamber, and the pump is passed through the second throttle from the cam back pressure chamber. Room Or connected to the return channel.
[0015]
This also moves the cam (changes the cam lift amount) by the pressure of the low-pressure fluid flowing into the cam back pressure chamber. The cam back pressure chamber is controlled by the flow rate flowing from the flow control valve. The pressure of the cam back pressure chamber is adjusted by the balance between the amount flowing in from the low-pressure channel via the flow control valve and the amount flowing out through the second throttle, and the cam is moved to suck The amount (pressure feed amount) is controlled.
[0016]
Claim 3 According to the invention described in (2), the second check valve that allows fluid to flow only in the direction from the low pressure flow path to the cam back pressure chamber immediately before the cam back pressure chamber, and the pump to the cam back pressure chamber Room A third aperture that communicates with is provided. Thereby, the movement of the cam (that is, fluctuation of the pumping amount) due to the reaction force of the cam roller at the time of pumping can be suppressed.
[0017]
Claim 4 According to the invention described in 1., the flow control valve is an electromagnetic valve. Since the flow rate control valve is low pressure only and high pressure does not act, the solenoid valve may be small and low cost, and controllability is good. Further, there is no need to increase the size of the device or increase the power.
Claim 5 According to the invention described in (1), the pressure difference acting on both end faces of the valve body is eliminated by providing the communication holes that communicate the both end faces of the valve body of the solenoid valve.
[0018]
Thereby, it can prevent that a fluid pressure acts on a solenoid valve, and can prevent a malfunction.
Claim 6 According to the invention described in the above, the flow control valve is an area throttle valve. Since this flow control valve is low pressure only and high pressure does not act, it can be small and low cost. Further, there is no need to increase the size of the device or increase the power.
[0019]
Claim 7 According to the invention described in (1), the electronic control unit serving as a control means for controlling energization to the flow control valve is provided, and the pressure in the cam back pressure chamber is controlled.
As a result, when the flow control valve is an electromagnetic valve, the drive frequency and duty ratio are controlled. When the flow control valve is an area throttle valve (operated by a linear solenoid or a stepping motor), the current value or excitation pattern (energization pattern) ) Can be adjusted to a desired pressure in the cam back pressure chamber.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment in which a variable discharge high pressure pump of the present invention is applied to a common rail injection system of a diesel engine will be described with reference to the drawings.
1 to 8 relate to the first embodiment of the present invention. FIG. 1 is a transverse sectional view along the central axis of the variable discharge high pressure pump, FIG. 2 is a sectional view taken along the line CC in FIG. FIG. 2 is a cross-sectional view of the cam 13 in which the cam surfaces 13a of the cam 13 in the AA cross-sectional view, the BB cross-sectional view, and the CC cross-sectional view in FIG.
[0021]
FIG. 4 is a system diagram in which the variable discharge high pressure pump P of the present invention is applied to a common rail injection system of a diesel engine.
FIG. 5 is a time chart showing the control status of the variable discharge high pressure pump P when the pumping amount is changed by the operation of the electromagnetic valve 6, the operation of the plunger by the cam lift, and the change of the pumping amount and the driving torque.
[0022]
FIG. 6 shows the operation along the central axis showing the operation of each part when the contact position between the cam roller 22 and the cam surface of the cam 13 is changed by moving the cam 13 in the left-right direction in the drawing by the operation of the electromagnetic valve 6. (A) is when the fuel pumping amount is full, (B) is when the fuel pumping amount is half, (C) is when the fuel pumping amount is small, ( D) each shows when the fuel pumping amount is zero.
[0023]
FIG. 7 is a flowchart showing an example of control of the variable discharge high pressure pump by the electronic control unit ECU.
8A and 8B are cross-sectional views along the central axis showing the operating state of the electromagnetic valve 6. FIG. 8A shows a state when the valve is closed, and FIG. 8B shows a state when the valve is opened.
In the system diagram of FIG. 4, the engine E is provided with a plurality of injectors I corresponding to the combustion chambers of the respective cylinders, and these injectors I are connected to a high-pressure accumulating pipe common to each cylinder, so-called common rail R. The injection of fuel from the injector I into each combustion chamber of the engine E is controlled by ON / OFF of the injection control electromagnetic valve B1, and while the electromagnetic valve B1 is open, the fuel in the common rail R is injected by the injector I. It is injected into the engine E. Therefore, it is necessary to continuously accumulate high predetermined pressure fuel corresponding to the fuel injection pressure in the common rail R. For this purpose, the variable discharge high-pressure pump P of the present invention passes through the supply pipe R1 and the discharge valve B2. Connected.
[0024]
This variable discharge high pressure pump P pressurizes the fuel sucked from the fuel tank T to a high pressure and controls the fuel in the common rail R to a high pressure. The common rail R is provided with a pressure sensor S1 for detecting the common rail pressure, and the electronic control unit ECU serving as a control means for controlling the system is configured so that the signal from the pressure sensor S1 has a preset optimum value. In addition, the discharge amount of the variable discharge amount high-pressure pump P is determined and a control signal is output to the discharge control device P2. The electronic control unit ECU further receives information on the engine speed, the TDC (top dead center) sensor S3, the throttle sensor S4, and the temperature sensor S5. The electronic control unit ECU outputs a control signal to the injection amount control electromagnetic valve B1 in accordance with the engine state determined by these signals.
[0025]
Next, details of the variable discharge high-pressure pump P will be described with reference to FIGS. In the figure, a drive shaft D is rotatably supported in the pump housing 1 via a bearing D2 and a bush D1, and the drive shaft D sucks up fuel from a fuel tank T (FIG. 4) and flows under a low pressure flow. A vane type feed pump P <b> 1 that supplies pressure to the feed flow path 11 is connected. A cam 13 that is slidable in the axial direction is provided at the right end of the drive shaft D. The cam 13 rotates with the drive shaft D at a speed that is ½ of the engine speed via a key W. It is supposed to do. When the cam 13 rotates, the rotor P12 of the feed pump P1 rotates through a half-moon-shaped plate P11, and by the rotation, fuel from the fuel tank T passes through a flow path (not shown) from an inlet valve (not shown). It is introduced into the P1 internal space (a space surrounded by the rotor P12, the casing P13, and the covers P14 and P15). The introduced fuel is pumped to the feed flow path 11 through a flow path (not shown) by the vane P16 disposed in the rotor P12 as the rotor P12 rotates.
[0026]
The low-pressure fuel (low-pressure fluid) in the feed flow path 11 is used not only for pressure feeding to the common rail as shown below, but also flows into the pump from the throttle flow path S and is used for lubrication inside the pump. Is done. The lubricated fuel exits from the valve V and is returned to the fuel tank T. Further, the pressure inside the pump is adjusted by the valve V so as to be almost atmospheric pressure.
[0027]
A head H is fitted into the right end opening of the pump housing 1, and the head H protrudes from the center of the left end and is inserted into the cam 13. A plurality of sliding holes 2a, which are cylinders, are provided at the center of the left end of the head H (FIG. 2). Plungers 21 are supported in the plurality of sliding holes 2a so as to be reciprocally movable and slidable. Has been. A shoe 21a is provided at the outer end of each plunger 21, and a cam roller 22 is rotatably held by each shoe 21a. The shoe 21a can be moved only in the radial direction by a guide 200, and the guide 200 is fixed to the head H by a bolt (not shown).
[0028]
The cam 13 is arranged so as to be slidable on the outer periphery of the cam roller 22, and a cam surface 13 a having a plurality of cam peaks arranged at equal intervals is formed on the inner peripheral surface of the cam 13. . As shown in FIG. 3, the cam surface 13a has a cam lift that changes depending on its position. A space formed between the inner end surface of each plunger 21 and the inner wall surface of each sliding hole 2 a is a pressure chamber 23. Thus, when the cam 13 rotates together with the drive shaft D, the plunger 21 reciprocates in the sliding hole 2a and pressurizes the fuel in the pressure chamber 23. FIG. 2 shows a state where the plunger 21 is at the lowest point.
[0029]
The pressurized fuel is a high-pressure channel, that is, a pressure accumulation pipe, through a discharge valve 24 corresponding to B2 in FIG. 4 fixed to the head H wall from a discharge hole 24 (FIG. 1) communicating with the pressure chamber 23. It is pumped to the common rail R (FIG. 4). The discharge valve 3 has a valve body 31 and a return spring 32 that urges the valve body 31 in the valve closing direction. When the pressurized fuel exceeds a predetermined pressure, the discharge valve 3 opens against the spring force of the return spring 32, and the high pressure flow. The pressurized fuel is discharged into the discharge flow path 33 which is a path.
[0030]
In FIG. 1, a space formed by the drive shaft D and the left end surface of the cam 13 is a cam back pressure chamber C, and the cam back pressure chamber C and the low pressure flow path (feed flow path) 11 are the first in the housing 1. Are communicated with each other through the diaphragm K1, the space 1a, the communication path D1a of the bush D1, the groove Da of the drive shaft D, and the flow paths Db and Dc. The cam back pressure chamber C and the electromagnetic valve 6 communicate with each other via the flow paths Db and Dc, the groove Da, the communication path D1a, the space 1a, the flow path 1b in the housing, and the fuel reservoir 1c. The flow path 1d on the lower surface of the solenoid valve is connected to the inside of the pump (atmospheric pressure) forming the pump chamber 201 or the return flow path 202 through a flow path (not shown).
[0031]
The cam 13 is provided with a spring SP that is biased in the left direction in FIG. 1, and the movement of the cam 13 is based on a balance between the rightward force in FIG. 1 due to the pressure in the cam back pressure chamber C and the spring force of the spring SP. The position is determined. That is, the cam lift amount varies depending on the position where the cam roller 22 and the inner peripheral surface of the cam 13 are in sliding contact with each other.
The cam 13 is in a state where the right end of the drive shaft D and the left end of the cam 13 are in contact with each other at the time of maximum pumping (the state shown in FIG. 1). When the pumping amount is zero (no pumping), the right end of the cam 13 is This is a time when it contacts the left end of the guide 200 (see FIG. 6D). The variable discharge high-pressure pump in FIG. 1 has a geometric maximum pumping amount of 226 mm per stroke. ^Three / St, the plunger diameter is 6 mm, and the cam lift is 2 mm.
[0032]
In FIG. 1, only the lock adapter 5 is assembled to the right end of the head H via a stopper 41 and a first check valve 4 that is a valve member. Up to 23, only the check valve 4 exists.
The electromagnetic valve 6 is disposed so as to open and close between the flow path 1d communicating with the pump chamber 201 or the return flow path 202 and the cam back pressure chamber C via the fuel reservoir 1c. The amount flowing out from the pressure chamber C is controlled. Then, the cam position, that is, the cam lift amount is controlled by adjusting the pressure of the cam back pressure chamber C in accordance with the balance of the amount of the outflow amount flowing from the low pressure passage 11 through the first restrictor K1. .
[0033]
As shown in FIG. 1, the first check valve 4 includes a flow path 43 that penetrates the housing 42 in the left-right direction and a valve body 44 that opens and closes the flow path 43. The flow path 43 is enlarged in the direction toward the pressure chamber 23 (leftward in the drawing) to form a conical seat surface 45, and the valve body 44 is moved to the right by a spring 46 held in the stopper 41. Energized and seated on the seat surface 45. As described above, the first check valve 4 is closed in the state shown in the figure, and is opened by the pressure of the fuel flowing into the pressure chamber 23 through the feed flow path 11. At this time, fuel flows into the pressure chamber 23 through the seat surface 45 of the check valve 4 and the flow path in the stopper 41. The valve body 44 closes when the pressurization of the pressure chamber 23 is started, and holds it until the end of fuel pressure feeding. The valve body 44 has a groove extending in the axial direction on the outer peripheral surface, and the fuel flows through the groove.
[0034]
As shown in FIG. 8, the electromagnetic valve 6 has a housing 61 containing a coil 62 and a valve body 71 fitted and fixed to the left end of the housing 61, and a pump housing is provided by a flange 63 provided on the outer periphery of the housing 61. 1 is fixed. A needle valve 73, which is a valve body, is slidably held in the valve body 71. An annular flow path 72 provided around the left end of the needle valve 73 and a flow path 74 to the left of the needle valve 73. It is designed to open and close between. As shown in FIG. 1, the annular flow path 72 includes a fuel reservoir 1c formed between the valve body 71 and the pump housing 1, and flow paths 1b, 1a, D1a, Da, Db, Dc in the pump housing 1. And the flow path 74 communicates with the interior of the pump or the return flow path via the flow path 1d. A substantially conical seat surface 75 is formed at the right end portion of the flow path 74, and a substantially conical tip end portion of the needle valve 73 is seated on the seat surface 75 to close between the flow paths 72 and 74. It is supposed to do.
[0035]
Here, the needle valve 73 is configured such that the diameter of the sliding portion is equal to the diameter of the seat edge portion (the contact edge with the seat surface 75 when the valve is closed). At this time, the force of the fuel supplied into the flow path 72 around the needle valve 73 balances the force pushing the needle valve 73 leftward and the force pushing rightward, so that no hydraulic action force is generated by the feed fuel. In addition, a filter is usually provided in the middle of the fuel flow path leading to the flow path 72 to prevent foreign matter from entering between the needle valve 73 and the seat surface 75 so that the valve is always open. The filter is made of, for example, a metal mesh, and the mesh opening may be smaller than the flow path area when the needle valve 73 is at the maximum lift.
[0036]
8A when the coil 62 is not energized, the tip end portion of the needle valve 73 is seated on the seat surface 75 of the valve body 71 and becomes a communication path to the inside of the pump or the return flow path. The flow path 1d is closed. As described above, the solenoid valve 6 is closed in a non-energized state, so that the cam 13 is moved to the rightmost position when the coil is broken to make the cam lift zero (see FIG. 6D), and the fuel There is an effect to prevent the pumping of. When the tip of the needle valve 73 is separated from the seat surface 75 by energization of the coil 62, fuel flows out from the seat surface 75 of the electromagnetic valve 6, the pressure in the cam back pressure chamber C decreases, and the cam 13 moves leftward. The cam lift increases and suction and pumping become possible.
[0037]
The electromagnetic valve 6 and the cam 13 constitute the discharge control device P2 in FIG.
Next, the operation of the variable discharge high pressure pump P configured as described above will be described.
The variable discharge high-pressure pump P is configured to perform suction and pumping four times per rotation of the cam 13, and the pumping amount is controlled by the amount of fuel sucked into the pressure chamber 23.
[0038]
However, the suction amount is controlled by changing the cam lift amount by the movement of the cam 13 in which the variable cam profile is formed, and the angle of the suction stroke does not change.
The cam 13 can be moved by the pressure in the cam back pressure chamber C (from atmospheric pressure to feed pressure), and can be adjusted by changing the drive frequency and duty ratio of the solenoid valve 6, so that the pressure in the cam back pressure chamber C can be increased. For example, the cam lift amount is small, that is, the suction amount and the pumping amount are small. If the pressure is low, the cam lift amount is large, that is, the suction amount and the pumping amount are large.
[0039]
In the time chart of FIG. 5, when the pumping amount is large, the energization period to the solenoid valve 6 is lengthened, the amount of outflow from the solenoid valve 6 is increased to lower the pressure in the cam back pressure chamber C, and the cam 13 To the left in the figure to increase the cam lift. On the contrary, when the pumping amount is small, the energization period to the solenoid valve 6 is shortened, the outflow amount from the solenoid valve 6 is reduced, and the pressure in the cam back pressure chamber C is increased (close to the feed pressure). Then, the cam 13 is moved to the right to reduce the cam lift amount.
[0040]
In the intake stroke, the plunger 21 is lowered by the feed pressure to suck in the fuel, and when the suction is completed, the first check valve 4 is closed. Then, the plunger 21 is raised in the pressure feed stroke, the fuel in the pressure chamber 23 is pressurized, and is sent to the pressure accumulation pipe (common rail R) which is a high pressure flow path.
Further, as shown in FIG. 5, the variable discharge high pressure pump P of this configuration is always in sliding contact with the cam. Therefore, in the suction metering pump as previously proposed (see FIG. 13). There are no noise or reliability problems due to the collision between the cam and the cam roller.
[0041]
Further, since the control of the pumping amount is performed by controlling the cam lift amount, the cam lift inclination, that is, the oil feeding rate is lowered at the time of small amount pumping, and the peak torque and average torque of the variable discharge high pressure pump P can be reduced.
Thus, in the said structure, control of the pumping amount shall be performed by changing a cam lift. That is, there is no flow rate control valve for controlling the amount of fuel sucked between the low pressure channel 11 (feed channel) and the pressure chamber 23, and only the first check valve 4 is provided and sucked into the pressure chamber 23. All fluid is pumped. Therefore, there is no problem of self-closing or electromagnetic valve responsiveness unlike the conventional prestroke control valve.
[0042]
Since the high pressure does not act on the solenoid valve 6 for controlling the pressure in the cam back pressure chamber C as means for changing the cam lift, that is, for moving the cam 13, the return spring 65 may be small and generate a suction force. Since the coil 62 to be made may be small, it can be made small.
Therefore, it is possible to easily and reliably control the flow rate of pumping to the high-pressure channel with a simple configuration, and there is no need to increase the size of the device or increase the power.
[0043]
FIG. 7 is a flowchart showing an example of control by the electronic control unit ECU. As shown in the system diagram of FIG. 4, various information is constantly input from the sensors to the electronic control unit ECU, and the engine (pump) is detected from the NE signal detected by the engine speed sensor S2. ) The rotational speed is calculated from the accelerator opening detected by the throttle sensor S4, and the target common rail pressure (CPTRG) and the injection amount (pumping amount) are calculated based on the previously input control map (step (1), step (1)). 2)). Subsequently, the drive frequency and duty ratio (energization period) of the solenoid valve 6 corresponding to the pump speed and the pumping amount are calculated (step (3)), and the solenoid valve 6 is energized.
[0044]
In addition, the electronic control unit ECU constantly detects the common rail R pressure (CPACT) by the pressure sensor S1, and compares the detected common rail R pressure (CPACT) with the target common rail pressure (CPTRG). (Step (4)), if different, correct. As a correction method, calculation of (CPACT-CPTRG) is performed to calculate a necessary increase in pumping amount (step (5)), and the driving frequency and duty ratio (energization period) corresponding to this increase are changed ( Step (6)). Next, it is determined again whether or not (CPACT = CPTRG) (step (7)). If not (CPACT = CPTRG), the process returns to step (5) and repeats feedback control until (CPACT = CPTRG). .
[0045]
9 and 10 relate to the second embodiment of the present invention, FIG. 9 is a cross-sectional view along the central axis of the variable discharge high pressure pump, and FIG. 10 relates to the electromagnetic valve 6 used in FIG. (A) shows a cross-sectional view along the central axis of the electromagnetic valve 6, and (B) shows a cross-sectional view along the central axis of the valve body 73 of the electromagnetic valve 6 of (A).
In FIG. 9, the low-pressure channel 11 (feed channel) is connected to a fuel reservoir 1c in which the electromagnetic valve 6 is installed by a channel (not shown).
[0046]
The electromagnetic valve 6 is disposed between the low pressure channel 11 and the cam back pressure chamber C, and the second throttle K2 is provided between the cam back pressure chamber C and the pump chamber 201 or the return channel 202. In this case, the second diaphragm K2 is provided at the center of the cam, but it is not always necessary to be here.
In this configuration, the pressure of the cam back pressure chamber C is controlled by the balance between the inflow amount from the electromagnetic valve 6 that forms the flow control valve and the outflow amount from the second throttle K2, and the cam 13 is controlled by the pressure in FIG. And move to the position where the rightward force and the leftward force of the spring SP are balanced.
[0047]
Then, the amount of suction, that is, the pressure feeding amount is changed by changing the lift amount of the cam roller 22, that is, the plunger 21.
FIG. 10A shows the configuration of the electromagnetic valve 6 of the variable discharge high pressure pump P having this configuration. The solenoid valve 6 has a normally open configuration. Therefore, when the coil 62 is disconnected, the solenoid valve 6 is always opened to increase the amount of inflow from the solenoid valve 6, increase the pressure in the cam back pressure chamber C, and It can be moved to the right in FIG. 9 so that the cam lift amount is zero, that is, neither suction nor pressure feeding is performed.
[0048]
Further, as shown in (B), the valve body 73 has a communication hole 76 communicating between the left and right end faces to prevent malfunction due to a pressure difference applied to the left and right end faces.
FIG. 11 is a cross-sectional view along the central axis of the variable discharge high-pressure pump of the third embodiment.
In the third embodiment of FIG. 11, in the pump of the first embodiment, a second check valve G1 is provided immediately before the cam back pressure chamber C, and the cam back pressure chamber C and the pump chamber 201 or return flow path are provided. A third diaphragm K3 is provided between the two.
[0049]
At the time of pressure feeding, the cam roller 22 and the plunger 21 are lifted (moved in the direction of the pump central axis) by the cam 13. At that time, the cam 13 receives the reaction force to the left in FIG. It may move and the pumping amount may change. Therefore, the second check valve G1 prevents the fuel in the cam back pressure chamber C from flowing out from the solenoid valve 6 when the solenoid valve 6 is opened, and the cam 13 is moved to the left in the figure, thereby changing the pumping amount. It is trying to suppress.
[0050]
However, when only the second check valve G1 is installed, the fuel in the cam back pressure chamber C cannot flow out through the solenoid valve 6 by the second check valve G1 when it is desired to increase the pumping amount. A third throttle K3 is provided between the pressure chamber C and the inside of the pump, and when the pumping amount increases (when the cam is moved to the left), the fuel in the cam back pressure chamber C passes through the third throttle K3. Spill.
[0051]
As another means for suppressing the movement of the cam 13 due to the reaction force during pressure feeding, instead of providing the second check valve G1, the energization of the electromagnetic valve 6 is synchronized with the rotation of the pump as shown in the flowchart of FIG. Thus, if the solenoid valve 6 is opened only during the suction stroke and is controlled so as to be closed during the pressure feed stroke, fuel in the cam back pressure chamber C does not flow out. Can be prevented.
[0052]
In addition, if the second check valve G1 and the throttle K3 are provided in this control method, the movement of the cam 13 due to the reaction force at the time of pressure feeding is further reliably suppressed.
FIG. 12 is a cross-sectional view taken along the central axis of the variable discharge high pressure pump of the fourth embodiment.
As shown in FIG. 12, an area throttle valve Y using a linear solenoid, a stepping motor, or the like as an actuator can be used as a flow control valve for controlling the pressure in the cam back pressure chamber C.
[0053]
In this case, the second check valve G1 used in the third embodiment may be provided.
Further, in each of the above-described embodiments, the inner cam pressure feed type pump is shown as an example. However, the present invention is not limited to this, and the present invention can also be applied to a ridge type or outer cam pressure feed type pump.
[Brief description of the drawings]
FIG. 1 relates to a first embodiment of the present invention, and is a cross-sectional view along a central axis of a variable discharge high-pressure pump.
FIG. 2 relates to the first embodiment of the present invention, and is a cross-sectional view taken along the line CC in FIG.
FIG. 3 relates to the first embodiment of the present invention, and is a cam in which the cam surface 13a of the cam 13 in the AA sectional view, the BB sectional view, and the CC sectional view in FIG. 13 is a cross-sectional view of FIG.
FIG. 4 relates to the first embodiment of the present invention, and is a system diagram in which the variable discharge high pressure pump P of the present invention is applied to a common rail injection system of a diesel engine.
FIG. 5 relates to the first embodiment of the present invention, and shows the control status of the variable discharge high pressure pump P when the pumping amount is changed by the operation of the solenoid valve 6, the operation of the plunger by the cam lift, the change of the pumping amount and the driving torque. It is a time chart which shows.
FIG. 6 relates to the first embodiment of the present invention, and changes the contact position between the cam roller 22 and the cam surface of the cam 13 by moving the cam 13 in the left-right direction in the figure by the operation of the electromagnetic valve 6; 4A is a cross-sectional view of the main part along the central axis showing the operation of each part of FIG. 2A, FIG. 3A is when the fuel pumping amount is full, FIG. 2B is when the fuel pumping amount is half, and FIG. Indicates when the fuel pumping amount is small, and (D) indicates when the fuel pumping amount is zero.
FIG. 7 relates to the first embodiment of the present invention, and is a flowchart showing an example of control of a variable discharge high pressure pump by an electronic control unit ECU.
FIG. 8 relates to the first embodiment of the present invention, and is a cross-sectional view along the central axis showing the operating state of the electromagnetic valve 6, (A) is a state when the valve is closed, and (B) is a valve opening. Each state is shown.
FIG. 9 relates to a second embodiment of the present invention, and is a cross-sectional view along the central axis of a variable discharge high pressure pump.
FIG. 10 relates to the second embodiment of the present invention, and relates to the electromagnetic valve 6 used in FIG. 9, in which (A) shows a cross-sectional view along the central axis of the electromagnetic valve 6, and (B) shows (A). ) Shows a cross-sectional view along the central axis of the valve body 73 of the electromagnetic valve 6.
FIG. 11 is a cross-sectional view along the central axis of a variable discharge high-pressure pump according to a third embodiment.
FIG. 12 is a transverse sectional view taken along the central axis of a variable discharge high pressure pump according to a fourth embodiment.
13A and 13B relate to a variable discharge high-pressure pump proposed by the present inventors in place of a conventional variable discharge high-pressure pump, wherein FIG. 13A is a cross-sectional view along the central axis, and FIG. 13B is a cam lift. It is an operation explanatory drawing which shows the change of a state, a control method, the action | operation of a plunger and a cam roller, a pumping amount, and a driving torque.
FIG. 14 is a cross-sectional view of a main part along the central axis showing an example of a conventional variable discharge high-pressure pump.
[Explanation of symbols]
2a Cylinder (sliding hole)
4 First check valve
6 Flow control valve
11 Low pressure channel
13 cams
21 Plunger
23 Pressure chamber
73 Disc
76 communication hole
201 Pump room
202 Return flow path
C cam back pressure chamber
ECU electronic control unit
G1 Second check valve
K1 first aperture
K2 Second aperture
K3 Third aperture
P Variable discharge high pressure pump
R High-pressure flow path (common rail)
Y area throttle valve

Claims (7)

A plunger is inserted and disposed in the cylinder so as to be able to reciprocate, a pressure chamber is formed by the inner wall surface of the cylinder and the end surface of the plunger, and a low-pressure fluid introduced into the pressure chamber from a low-pressure flow path is In a variable discharge high-pressure pump that is pressurized by a reciprocating movement of a plunger and pumped to a high-pressure channel, between the pressure chamber and the low-pressure channel, only in the direction from the low-pressure channel to the pressure chamber. Providing only a first check valve for flowing fluid, forming a variable cam profile in a cam for reciprocating the plunger, and comprising means for moving the cam ;
The cam is moved by the pressure of the cam back pressure chamber,
A first throttle is provided between the low pressure flow path and the cam back pressure chamber, and the cam back pressure chamber is connected to a pump chamber or a return flow path via a flow rate control valve that forms a means for moving the cam. Variable discharge high pressure pump characterized by A plunger is inserted and disposed in the cylinder so as to be able to reciprocate, a pressure chamber is formed by the inner wall surface of the cylinder and the end surface of the plunger, and a low-pressure fluid introduced into the pressure chamber from a low-pressure flow path is In a variable discharge high-pressure pump that is pressurized by a reciprocating movement of a plunger and pumped to a high-pressure channel, between the pressure chamber and the low-pressure channel, only in the direction from the low-pressure channel to the pressure chamber. Providing only a first check valve for flowing fluid, forming a variable cam profile in a cam for reciprocating the plunger, and comprising means for moving the cam;
The cam is moved by the pressure of the cam back pressure chamber,
A flow control valve that forms the cam moving means is provided between the low pressure flow path and the cam back pressure chamber, and the cam back pressure chamber is connected to the pump chamber or the return flow path via a second throttle. Variable discharge high pressure pump characterized by Provided immediately before the cam back pressure chamber is a second check valve that allows fluid to flow only in the direction from the low pressure channel toward the cam back pressure chamber, and a third throttle communicating with the pump chamber in the cam back pressure chamber. variable discharge high pressure pump of claim 1, characterized in that the. 4. The variable discharge high pressure pump according to claim 1, wherein the flow control valve is a solenoid valve . The variable discharge high-pressure pump according to claim 4 , wherein a pressure difference acting on both end faces of the valve body is eliminated by providing a communication hole that communicates both end faces of the valve body of the solenoid valve . 6. The variable discharge high pressure pump according to claim 1, wherein the flow control valve is an area throttle valve . The variable discharge high-pressure pump according to claim 4, further comprising an electronic control unit that serves as a control unit that controls energization of the flow control valve, and controls the pressure in the cam back pressure chamber .

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