JPH01100323A - Variable-discharge high-pressure pump - Google Patents

Abstract

PURPOSE:To adjust the target fuel pressure precisely and quickly by providing a cam reciprocating a plunger and pressurizing and discharging the fuel in a pressure chamber and having a cam curve that the cam speed is made low in the initial stage of the advance movement of the plunger and the cam speed is made high in the later stage of the advance movement. CONSTITUTION:A variable-discharge high-pressure pump 5 has a cam chamber 31 provided at the lower end of a pump housing 30 and a plunger 37 reciprocatably inserted in a cylinder 32. The low-pressure fuel is fed to a pump chamber 38 formed at the upper section of the plunger 37 of the cylinder 32 from a low-pressure feeding pump via a guide pipe 33, a fuel reservoir 41, and a solenoid valve 34, the fuel pressurized in the pump chamber 38 is discharged via a discharge valve 9. In this case, a cam 36 arranged in the cam chamber 31 and reciprocating the plunger 37 is formed so that the cam curve has the nonuniform-speed characteristic that the cam speed is made low in the initial stage of the advance movement of the plunger 37 and the cam speed is made high in the later stage of the advance movement.

Description

DETAILED DESCRIPTION OF THE INVENTION Purpose of the Invention [Field of Industrial Application] The present invention relates to a variable discharge amount used in a so-called common rail fuel injection device, which is equipped with a high pressure accumulation pipe, among fuel injection devices for diesel engines. Regarding high pressure pumps.

[Prior Art] In recent years, injection characteristics such as fuel injection amount, fuel injection pressure, fuel injection pressure, and fuel injection rate have been effectively improved in order to improve the fuel consumption efficiency, exhaust gas quantification rate, and operating performance of diesel engines. As a controllable fuel injection control device, a device has been developed that is equipped with a so-called common rail, a high-pressure accumulation pipe that accumulates high-pressure fuel in a fuel supply system, and injects fuel from the common rail to a diesel engine via a fuel injection valve. ing. As such a technique, for example, "Electromagnetic Control Injection System for Diesel ◆ Engine" (Japanese Unexamined Patent Publication No. 165858/1983) has been proposed. That is, as shown in FIG. 8, the fuel pressurized by the high-pressure supply pump J1 is fed to the common rail J2, and the fuel accumulated in the common rail J2 is released from the injection valve J4 by opening and closing the fuel injection solenoid valve J3. This is injected into each cylinder of diesel engine J5. As shown in Fig. 9, the system operates by maintaining the common rail pressure Pc inside the common rail J2 at a substantially constant pressure, and injecting a predetermined amount of high-pressure fuel when the fuel injection solenoid valve J3 opens. In order to increase the common rail pressure Pc which has decreased due to the injection, a predetermined amount of high pressure fuel is discharged from the high pressure supply water tube J1 to the common rail J2.

[Problems to be Solved by the Invention] By the way, the above-mentioned conventional high-pressure fuel supply pump generally has the following problems:
When the time to start pressurizing and pumping fuel is early, the amount of high-pressure fuel discharged increases and the fuel pressure tends to rise; on the other hand, when the time to start pressurizing and pumping fuel is late, the amount of high-pressure fuel discharged decreases, and Fuel pressure tended to be difficult to rise. For this reason, if the pressurization/pumping start time is early, the accumulated fuel pressure will rise excessively, and if the pressurization/pumping start time is late, the accumulated fuel pressure will drop, so the accumulated fuel pressure will be reduced. There was a problem in that it was difficult to maintain the fuel pressure at the target fuel pressure.

For example, when applied to a vehicle-mounted diesel engine, if the target fuel pressure to be accumulated changes depending on the operating state of the diesel engine, it will not be able to follow the desired pressure under various operating conditions. It is not possible to maintain the fuel pressure of the diesel engine, which adversely affects the operating performance of the diesel engine.
This was a particularly important problem in practical use.

Further, as described above, when the amount of fuel discharged is large, that is, when the pressurization and pumping start time is early, the driving torque of the high-pressure fuel supply pump becomes large, resulting in a large energy loss.

For this reason, for example, when applied to the fuel system of an automotive diesel engine, the negative aspects of the diesel engine increase, and
Fuel consumption efficiency and driving performance also deteriorate.

Furthermore, the responsiveness and followability of the control that maintains the accumulated fuel pressure at the target fuel pressure are still insufficient, and the accuracy of the fuel pressure control is low. In addition to this, the reliability of fuel pressure control by the high-pressure supply pump was also reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a variable discharge amount high-pressure pump that can quickly adjust the fuel pressure of accumulated fuel to a target fuel pressure that changes depending on the operating state of a diesel engine with good accuracy. .

1 Bean L 1 Dish [Means for Solving the Problems] The present invention, which was made to solve the above problems, includes a cylinder, which is reciprocally and slidably fitted into the cylinder, and which applies fuel during forward movement. a plunger for pressurizing and force-feeding, and a shutoff valve that cuts off communication between a pressure chamber formed from an inner circumferential surface of the cylinder and an upper surface of the plunger and a low-pressure side according to an externally commanded pressurization and force-feeding start time; A variable discharge amount high-pressure pump that pressurizes and delivers fuel to a high-pressure accumulation pipe that accumulates pressure of high-pressure fuel to be supplied to a diesel engine. The cam is characterized in that the cam has a cam curve with non-uniform velocity characteristics, in which the cam speed is low at the beginning of the forward movement of the plunger, and the cam speed is high at the end of the forward movement of the plunger. The gist of this paper is a variable discharge amount high pressure pump.

A cylinder includes, for example, a suction boat that communicates with a low-pressure fuel supply source, a discharge boat that is connected to a high-pressure accumulation pipe and has a discharge valve, and a communication passage that connects the inside of the cylinder with the suction boat that is on the low-pressure side. This can be realized using a cylindrical member.

The plunger is fitted into the cylinder so that it can reciprocate and slide freely, and pressurizes and pumps fuel during forward movement. For example, it can be realized by a rod-shaped piston or a ram having an upper surface that can cooperate with the inner peripheral surface of the cylinder to form a pressure chamber and a lower surface that becomes a contact with a cam or the like. Further, for example, it is preferable to form the cylinder into a cylindrical shape without leads, since the oil-tightness is improved.

The shutoff valve is a valve that shuts off communication between the pressure chamber formed from the inner circumferential surface of the cylinder and the upper surface of the plunger and the low-pressure side in accordance with the pressurization and pressure feeding start timing commanded from the outside. For example, when energized, the valve body closes a low-pressure passage bored inside the valve body that communicates with the low-pressure side, and the valve body receives the fuel pressure in the pressure chamber as a pressing force in the valve-closing direction. This can be achieved using the expression Gaijinben.

A cam has a cam curve with non-uniform velocity characteristics, where the cam speed is low at the beginning of the plunger's forward movement, and the cam speed is high at the end of the plunger's forward movement, and the driving force is transmitted from the outside. The plunger rotates to cause the plunger to reciprocate. For example, this can be realized by a cam that is fixed to a camshaft that is rotated by a driving force transmitted from a diesel engine and comes into contact with a contact on the lower surface of a plunger, and that has a modified constant velocity curve that has an acceleration/deceleration portion added to the constant velocity curve. Further, for example, the cam may have a sinusoidal composite curve such as a modified trapezoidal curve or a modified sine curve, or a cam curve such as a universal cam curve.

[Function] The variable discharge amount high pressure pump of the present invention uses a cutoff valve to cut off communication between the pressure chamber formed from the inner circumferential surface of the cylinder and the upper surface of the plunger and the low pressure side according to the pressurization/pressure feeding start timing commanded from the outside. When the engine is shut off, a plunger that reciprocates in cooperation with a cam that rotates by external driving force pressurizes and pumps fuel into the high-pressure accumulation pipe that accumulates high-pressure fuel to be supplied to the diesel engine. In this case, the cam having a cam curve with non-uniform velocity characteristics works to make the cam speed low at the beginning of the forward movement of the plunger, and to increase the cam speed at the latter stage of the forward movement of the plunger.

That is, when the pressurization and pressure feeding of fuel starts early, the pressure and pressure feeding starts from the beginning of the forward movement of the plunger, so the cam speed is slowed down to reduce the fuel pressure and the amount of high-pressure fuel discharged per unit time. When the pressurization and pressure feeding start time is late, the pressure and pressure feeding starts at the end of the forward movement of the plunger, so the cam speed is increased to increase the fuel pressure and the amount of high-pressure fuel discharged per unit time.

Therefore, the variable discharge amount high pressure pump of the present invention works to maintain the pressure of the accumulated fuel at a desired pressure even if the fuel pressurization and pumping period changes.

The technical problems of the present invention are solved by each component of the present invention acting as described above.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail based on the drawings. FIG. 2 shows a system configuration of a common rail fuel injection control device equipped with a variable discharge amount high pressure pump, which is an embodiment of the present invention.

As shown in the figure, a common rail fuel injection control device 1
a four-cylinder diesel engine 2; a fuel injection valve 3a for injecting fuel into each cylinder of the diesel engine 2;
3b, 3c, 3d, the fuel injection valves 3a, 3b,
3c and 3d, a high-pressure accumulation pipe that accumulates pressure of high-pressure fuel, a so-called common rail 4, and a variable discharge amount high-pressure pump 5, which is a high-pressure supply pump that pumps high-pressure fuel to the common rail 4.
and an electronic control unit (hereinafter simply EC) that controls them.
Call it U. )6.

The fuel injection characteristics such as the fuel injection amount and fuel injection characteristics from the fuel injection valves 3a, 3b, 3c, and 3d to each cylinder of the diesel engine 2 are transmitted from the ECU 6 to the fuel injection solenoid valve 7a,
It is controlled by energizing/de-energizing 7b, 7c, and 7d.

High-pressure fuel is fed under pressure from a variable discharge amount high-pressure pump 5 via a supply pipe 8 and a discharge valve 9 to the common rail 4 where the high-pressure fuel is stored.

The variable discharge amount high-pressure pump 5 pressurizes the fuel taken in from the fuel tank 10 via the low-pressure supply pump 11 to a high pressure, and then pumps it to the common rail 4 to increase the fuel pressure inside the common rail 4, that is, the common rail pressure. Maintain high pressure.

The common rail fuel injection control device 1 includes, as detectors, a rotation speed sensor 21 that detects the rotation speed of the diesel engine 2, an accelerator operation amount sensor 22 that detects the accelerator pedal operation amount corresponding to the load, and a common rail pressure inside the common rail 4. A pressure sensor 23 for detecting the rotation angle of the camshaft of the variable discharge amount high pressure pump 5 is provided.

The signals of each of the above sensors are input manually to the ECU 6, and the ECU 6
controls the fuel injection valve 3 and the variable displacement high pressure pump 5.

The ECU 6 is configured as a logic operation circuit centering around a CPU 6a, ROM 6b, RAM 6C, and timer 6d, and outputs a human output M! via a common bus 6e. Connected to J6f and performs human output with the outside. The detection signals of each of the above-mentioned sensors are manually inputted to the CPU 6a from the human output section 6f. On the other hand, the CPU 6a, via the human output section 6f, controls the fuel injection solenoid valve 7a,
7b, 7c.

7d and a control signal to the variable discharge amount high pressure pump 5.

Next, the structure of the variable discharge amount high pressure pump 5 will be explained based on FIG. 1. The variable discharge amount high pressure pump 5 includes a cam chamber 31 provided at the lower end of the pump housing 30, a cylinder 32 provided inside the pump housing 30, and communicates with the cylinder 32, and is connected to the low pressure supply pump 11 described above. It is comprised of an introduction pipe 33 that receives low pressure fuel supply from the cylinder 32, and a solenoid valve 34 that is screwed to face the upper end surface of the cylinder 32.

A cam shaft 35 that rotates at 1/2 the rotation speed of the diesel engine 2 is inserted into the cam chamber 31, and the cam shaft 35 has a cam 36 that follows a deformed constant velocity cam curve.
It is equipped with The nuclear force J336 causes the cam 1li135 to perform two upward strokes in one revolution.

A plunger 37 is fitted into the cylinder 32 so as to be reciprocally and slidably movable. The plunger 37 has a cylindrical shape without any leads, and a pump chamber 38 is formed by the upper end surface of the plunger 37 and the inner peripheral surface of the cylinder 32. Further, the cylinder 32 is provided with a feed hole 39 that communicates with the pump chamber 38 and a discharge hole 40 that communicates with the pump chamber 3 at a position above the feed ball 39. The above feed ball 39
communicates with a fuel reservoir 41 formed between the cylinder 32 and the pump housing 30, and low pressure fuel from the low pressure supply pump 11 is supplied to the fuel reservoir 41 via the introduction pipe 33. .

A discharge valve 9 is disposed in the cylinder 32, and the discharge valve 9
communicates with the pump chamber 38 mentioned above via the discharge hole 40. The fuel pressurized inside the pump chamber 38 pushes open the valve body 43 of the discharge valve 9 against the biasing force of the return spring 44, and is forcefully sent to the common rail 4 from the discharge hole body 45 via the supply piping 8 described above. be done.

The lower end of the plunger 37 described above is connected to a valve seat 46, which is pressed against a tappet 48 by a plunger ring 47. The tappet 4 is equipped with a cam roller 49, and the cam roller 49 is connected to the cam chamber 31 described above.
It is in sliding contact with the internal cam 36. For this reason, the camshaft 35
As the plunger 37 rotates, the plunger 37 reciprocates via the cam roller 49 that moves up and down following the cam profile of the cam 36 and the valve seat 46. Note that the displacement and speed of the reciprocating movement of the plunger 37 with respect to a predetermined rotation angle of the cam 36 are determined by a cam profile corresponding to the deformation constant velocity curve characteristic of the cam 36. Therefore, the plunger 37
When the plunger 37 reciprocates inside the cylinder 32, the outer circumferential surface of the plunger 37 opens and closes the feed hole 39, and when the outer circumferential surface of the plunger 37 does not close the feed hole 39, low pressure is supplied via the three feed balls. Fuel is supplied to the pump chamber 38.

A solenoid valve 34 is screwed onto the cylinder 32 at a position opposite to the upper end surface of the plunger 37 . As shown in FIG. 3, the electromagnetic valve 34 has a negative end connected to the pump chamber 3.
When the body 51 is energized via the lead wire 52, the magnetic force of the trenoid 53 causes the biasing force of the spring 54 (as shown by the arrow in the figure). The armature 5 is attracted in the direction shown by arrow A in the same figure against the
5. The bomb chamber 3 moves integrally with the armature 55.
It is comprised of a mushroom-shaped valve body 57 which is an outer valve that connects and blocks the low pressure passage 50 by attaching and detaching to a seat portion 56 formed at the opening to the sun. The valve body 57 receives the fuel pressure inside the pump chamber as a pressing force in the valve closing direction (direction indicated by arrow A in the figure). When the electromagnetic valve 34 is energized at a predetermined time after the outer circumferential surface of the plunger 37 closes the feed hole 39, the valve body 57 is applied to the seat portion 56 to set the timing for starting pressurization of the plunger 37. This is a pre-stroke control type solenoid valve. Therefore,
By controlling the timing of energization to the solenoid valve 34, the amount of discharge to the common rail 4 can be adjusted. Note that, as shown in FIG. 1, the low pressure passage 50 is connected to a gear rally 58 and a passage 59.
It communicates with the above-mentioned fuel reservoir 41 via.

In order to control the solenoid valve 34, FIGS.
As shown in the figure, a pulse gear 61 having a number of protrusions corresponding to the number of cylinders of the diesel engine 2 (four in this embodiment) is fixed coaxially with the above-mentioned camshaft 35, and is closely opposed to the pulse gear 61. A cam angle sensor 24 consisting of an electromagnetic pickup is provided. Every time the protrusion of the pulse gear 61 passes near the cam angle sensor 24, a cam angle signal is transmitted to the ECU 6. Here, pulse gear 6
The mounting phase for each cam shaft 35 is as follows:
It is set to approach the cam angle sensor 24 at a rotational phase near each bottom dead center of 6b.

Next, the basic operation of the variable discharge amount high pressure pump 5 having the above configuration will be explained based on FIG. 1.

As shown in the figure, when the plunger 37, which reciprocates as the camshaft 35 rotates, opens the foot hole 39 when descending, fuel is sucked into the pump chamber through the feed hole 39, and - On the other hand, if the feed hole 39 is closed during the ascent, a pressing force is exerted on the fuel sucked into the pump chamber. However, at this time, if the electromagnetic valve 34 is not energized, the valve body 57 of the electromagnetic valve 34 is open, so the fuel inside the pump chamber is transferred to the low pressure passage 50,
The fuel reservoir 41 is sequentially connected to the fuel reservoir 41 via the gear rally 58 and the passage 59.
Rinse with water and do not apply pressure.

In this manner, when the electromagnetic valve 34 is energized while fuel is overflowing inside the pump chamber, the valve body 57 seats on the seat portion 56 and the low pressure passage 50 is closed.

Therefore, the fuel inside the pump chamber 3 starts to be pressurized due to the rise of the plunger 37, and the fuel pressure inside the pump chamber 3 is combined with the biasing force of the return spring 44 of the discharge valve 9, the pressure of the common rail 4, and the pressure of the valve body 43. When the resultant force determined by the pressure receiving area is exceeded, the fuel pumped through the discharge hole 40 pushes open the discharge valve 9 and is discharged to the common rail 4 through the discharge port body 45.

As described above, since the cam 36 has a characteristic of having a constant velocity curve of deformation, the displacement of the plunger 37 at the beginning of forward movement is small and the speed is low with respect to a predetermined rotation angle of the cam 36. The displacement in the latter half of the forward movement is large and the speed is high. , Therefore, at the beginning of the forward movement of the plunger 37, the solenoid valve 3
4 is energized, since the average cam speed is low, the discharge amount of the pumped fuel per unit time, the so-called oil delivery rate, is low, and the fuel pressure is also relatively low. When the solenoid valve 34 is energized in the late stage of operation,
Since the average cam speed is high, the discharge amount of the pumped fuel per unit time, the so-called oil feed rate, becomes high, and the fuel pressure also becomes relatively high.

Next, the operation of the common rail fuel injection control device 1 using the variable discharge amount high pressure pump 5 will be explained based on the flowchart shown in FIG.

This variable discharge amount high pressure pump control process is executed in conjunction with the activation of the ECU 6. First, in step 100, a process of reading the load α, rotational speed Ne, and common rail pressure PC is performed. In the following step 110, a process is performed to calculate the target common rail pressure PCO from the load α and the rotational speed Ne read in the above step 100 using an arithmetic expression or a map. Next, proceed to step 120, and calculate the fuel discharge amount Q from the target common rail pressure pco calculated in step 1 The calculation process is performed. In the subsequent step 130, a process is performed to calculate the control time TN from the discharge ff1Q calculated in the step 120 and the rotational speed Ne read in the step 100, based on an arithmetic expression or a map.

Next, the process proceeds to step 140, in which it is determined whether or not a cam angle signal has been detected. If the judgment is affirmative, the process proceeds to step 150; on the other hand, if the judgment is negative, the process waits while repeating the same steps until the cam angle signal is detected. do. Step 15
At 0, the timer T is reset and started.

In the following step 160, it is determined whether or not the time value of the timer T that started counting in the step 150 is equal to or greater than the control time TN calculated in the step 130, and if an affirmative determination is made, the process proceeds to step 170; , if a negative determination is made, the process waits while repeating the same steps until the control time TN has elapsed. In step 170, the solenoid valve 34
A process is performed to output a control signal to close the valve. Through the process of step 170, pressurization and pressure feeding of fuel is started. In the following step 180, it is determined whether or not a cam angle signal has been detected, and if an affirmative determination is made, step 190 is performed.
On the other hand, if the determination is negative, the process waits while repeating the same steps until a cam angle signal is detected. In step 190, the timer T is reset and started. In the following step 200, it is determined whether or not the clock value of the timer T that started counting in step 190 is a predetermined waiting time of 10 or more,
If a positive determination is made, the process proceeds to step 210, whereas if a negative determination is made, the process waits while repeating the same steps until the waiting time TO has elapsed.

In step 210, a process of outputting a control signal to open the solenoid valve 34 is performed. Through the process of step 210, the fuel to be discharged next time can be sucked. After executing step 210, the present variable discharge amount high pressure pump control process is ended. Thereafter, this variable discharge amount high pressure pump control process is executed by repeating steps 100 to 210 at predetermined time intervals.

Next, an example of the above control will be explained with reference to the timing chart of FIG. 7. As shown by the solid line in the figure, if the pressurization/force feeding start time is early, a control signal to close the solenoid valve 34 is output at time t2 after a short control time T1 has elapsed from time t1 when the cam angle signal is detected. The fuel is then pressurized and pumped. At time t2, the lift amount S of the plunger 37 is a small value, so the pumping stroke amount becomes a large value S1, and the discharge amount Q also becomes large.

Eventually, at time t5, after a standby time TO has elapsed from time t4 when the next cam angle signal is detected, a control signal is output to open the solenoid valve 34.

On the other hand, as shown by the broken line in the figure, if the pressurization/force feeding start time is late, at time t3 after a long control time T2 has elapsed from time t1 when the cam angle signal is detected,
A control signal is output to close the valve, and pressurization and pressure feeding of fuel is started. At the time t3, the lift amount S of the plunger 37 is
Since - is a large value, the pumping stroke amount becomes a small value S2, and the discharge amount Q also becomes small. In this way, when the control time TN is shortened, the pumping stroke amount increases, and on the other hand, when the control time TN is extended, the pumping stroke amount decreases. Therefore, by adjusting the control time TN, the discharge amount Q can be controlled to a desired value.

By the way, the cam 36 described above is set so that its cam speed is small at the beginning of the forward movement of the plunger 37, and becomes high at the latter stage of the forward movement. Therefore, when the control time TN is a short time T1, that is, when the discharge amount Q is large, the average cam speed during pressurization and pumping of fuel is the speed Vl (indicated by the #i line in the figure).

) becomes low. Therefore, the discharge amount per unit time, the so-called oil feeding rate, decreases, and the pumping pressure also decreases. On the other hand, when the control time TN is a long time T2, that is, when the discharge amount Q is small, the average cam speed during pressurization and pressure feeding of fuel becomes high as speed V2 (indicated by a dashed line in the figure).

Therefore, the discharge amount per unit time, the so-called oil feeding rate, increases, and the pumping pressure also increases. In this way, the variable discharge amount high pressure pump 5 is equipped with the cam 36 having a cam profile in which the cam speed changes, so when the discharge i-Q is large, the oil feeding rate is reduced and the pumping pressure is prevented from increasing excessively. On the contrary, when the discharge amount Q is small, the oil feeding rate is increased to suppress a drop in the pumping pressure.

In this embodiment, the cylinder 32 corresponds to the cylinder of the present invention, the plunger 37 corresponds to the plunger of the present invention, the solenoid valve 34 corresponds to the cutoff valve of the present invention, and the cam 36 corresponds to the cam.

As explained above, according to this embodiment, when the control time TN is short, that is, when the pressurization and pressure feeding start timing is early, a sudden increase in the common rail pressure PC can be suppressed, and when the control time TN is long, That is, when the pressurization/pumping start timing is late, it is possible to suppress a sudden drop in the common rail pressure PC, so that the actual common rail pressure PC can be stably maintained at the target common rail pressure PCO.

Therefore, even if the target common rail pressure PCO changes depending on the operating condition of the diesel engine 2, the actual common rail pressure PC can be quickly followed, so that the optimum common rail pressure PC can be determined under various operating conditions of the diesel engine 2. This is especially effective because it can be maintained.

In addition, as described above, when the fuel discharge ff1Q is large, that is, when the control time TN is short, pressurization and pressure feeding starts from the beginning of forward movement of the plunger 37, so the cam speed becomes low, so the variable discharge amount high pressure The driving torque of the pump 5 can be reduced, and energy waste can be suppressed.

As a result, the external load on the diesel engine 2 can be reduced, and the fuel consumption efficiency and driving performance of the diesel engine 2 can also be improved.

Furthermore, the responsiveness and followability of the control that maintains the common rail pressure PC at the target common rail pressure PCO is improved, so the control accuracy of the common rail pressure control is improved.
The stability of the control for maintaining the common rail pressure PC at the target common rail pressure P"Co is improved, and the reliability of the generation of the common rail pressure PC by the variable discharge amount high pressure pump 5 is also improved.

In addition, since the structure is effective due to the simple mechanical part consisting of the cam 36, the reliability of the variable discharge amount high pressure pump 5 is also increased.

Further, the valve body 57 of the solenoid valve 34 is configured to receive the fuel pressure inside the pump chamber as a pressing force in the valve closing direction. Therefore, since the valve body 57 is finished to sit on the seat portion 56 with high precision, when the valve body 57 is seated on the seat portion 56, the valve body 57 is placed on the plunger 37.
During the pressurization and pumping stroke, the fuel pressure inside the pump chamber receives a pressing force in the valve closing direction, maintaining extremely excellent sealing performance.

Furthermore, since the plunger 37 has a cylindrical shape with no leads, the high-pressure fuel inside the pump chamber formed by the inner peripheral surface of the cylinder 32 and the upper end surface of the plunger 37 does not leak to the low-pressure side. Therefore, leakage of high-pressure fuel to the low-pressure side during the pressurization and pumping stroke of the plunger 37 can be reduced.

Further, since only the feed hole 39 and the discharge hole 40 are bored in the cylinder 32 as passages communicating with the pump chamber 3, leakage of high pressure fuel inside the pump chamber 3 to the low pressure side can be reduced.

Although the embodiments of the present invention have been described above, the present invention is not equally limited to these embodiments, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

Nizu Rinwata! As detailed above, the variable discharge amount high pressure pump of the present invention has the following features:
When pressurizing and pumping fuel starts early, pressurizing and pumping starts from the beginning of forward movement of the plunger, so the cam speed is slowed down to reduce the fuel pressure and the amount of high-pressure fuel discharged per unit time. - When the pressure feeding start time is late, pressurization and pressure feeding starts in the latter half of the forward movement of the plunger, so the cam speed is increased to increase the fuel pressure and the amount of high-pressure fuel discharged per unit time. Therefore, when pressurization and pressure feeding start time is early, it is possible to prevent the accumulated fuel pressure from increasing excessively, and when pressurization and pressure feeding start time is late, it is possible to suppress a drop in the accumulated fuel pressure, so that the pressure accumulation This has the excellent effect of stably maintaining the fuel pressure at the target fuel pressure at all times.

For example, when applied to a diesel engine installed in a vehicle, this means that even if the accumulated target fuel pressure changes depending on the operating condition of the diesel engine, it can be sufficiently followed, and it can be adjusted to suit the conditions under various operating conditions. This is particularly effective as it is possible to maintain a constant fuel pressure.

In addition, as mentioned above, when the amount of fuel discharged is large, that is, when the pressurization and pressure feeding start time is early, the cam speed is set to a low speed because the pressure and pressure feeding starts from the beginning of the forward movement of the plunger. The drive torque of the high-pressure pump can be kept low, and energy loss can be minimized.

Therefore, for example, when applied to the fuel system of an on-vehicle diesel engine, the load on the diesel engine can be reduced, and fuel consumption efficiency and driving performance can also be improved.

Furthermore, since the responsiveness and followability of the control that maintains the accumulated fuel pressure at the target fuel pressure increases, the control accuracy of the fuel pressure control improves, so the control that maintains the accumulated fuel pressure at the target fuel pressure improves. As well as improving stability,
The reliability of the fuel pressurization and pumping function using the variable discharge volume high-pressure pump is also increased.

Further, since each of the above effects is achieved by the cam having a predetermined characteristic curve, the reliability and performance of the variable discharge amount high pressure pump are also improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a variable discharge amount high pressure pump according to an embodiment of the present invention, FIG. 2 is a system configuration diagram of a fuel injection control device equipped with the same variable discharge amount high pressure pump, and FIG. 3 is the same. A cross-sectional view showing the structure of a solenoid valve installed in the variable discharge amount high-pressure pump, and FIG.
5 is a CC end view of FIG. 4, FIG. 6 is a flowchart showing the control, FIG. 7 is a timing chart showing the control, and FIG. 8 is a schematic diagram showing the configuration of the prior art. The apparatus configuration diagram, FIG. 9, is a timing chart showing the control of the prior art. 5... Variable discharge amount high pressure pump

Claims (1)

[Claims] 1. A cylinder, a plunger that is reciprocally and slidably fitted into the cylinder and pressurizes and pumps fuel during forward movement, and a plunger that pressurizes and pumps fuel according to externally commanded timings to start pressurizing and pumping. a shutoff valve that cuts off communication between a pressure chamber formed from the inner peripheral surface of the cylinder and the upper surface of the plunger and the low pressure side; a cam that rotates by a driving force transmitted from the outside and reciprocates the plunger; A variable discharge amount high-pressure pump that pressurizes and delivers fuel to a high-pressure accumulation pipe that accumulates high-pressure fuel to be supplied to a diesel engine. A variable discharge amount high-pressure pump characterized in that the pump has a cam curve with non-uniform velocity characteristics that increases the cam speed in the latter half of forward movement of the plunger.