JPH1061525A - Cam for plunger pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a suction valve and a discharge valve in an invariably closing condition so as to prevent relief of a fluid from a discharging side to a suction side, and improve pump performance by forming a cam for performing reciprocating motion of a plunger in a shape formed in such a constitution that displacing speed and displacing acceleration of the plunger are set to 0 at the top dead point and the bottom dead point of the plunger. SOLUTION: When a cam 29 formed in a shape in which three crests are formed on a foundation circle starts rotation from a rotary angle 0 deg. positioned on a bottom dead point, a plunger 24 is lifted up, and fuel is pressurized in a pump chamber 33 in a cylinder. In this time, a fluid is discharged by closing a suction valve 39a as well as opening a discharging valve, and the plunger 24 reaches a top dead point at the time of rotating it by 48 deg.. When the plunger 24 falls down by changing the moving direction of the plunger 24 from the top dead point, the discharge valve 39b is closed as well as opening the suction valve 39a so as to supply fuel. In such suction and discharge strokes, since displacing speed and displacing acceleration are set to 0 at the top dead point and the bottom dead point of the plunger 24, the suction valve 39a and the discharging valve 39b are invariably closed so as to prevent relief of the fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cam used in a plunger pump which draws fluid from a suction valve and discharges pressurized fluid from a discharge valve by reciprocating a plunger sliding in a cylinder.

[0002]

2. Description of the Related Art Generally, a cylinder is provided with a suction valve for sucking a fluid and a discharge valve for discharging a pressurized fluid in the cylinder, and a plunger reciprocates in the cylinder to reduce pressure fluctuations in the cylinder. 2. Description of the Related Art A plunger pump that opens and closes a discharge valve and a suction valve by using the same is known.

In this type of plunger pump, the plunger is in circumferential contact with a cam at its lower end,
It moves up and down along the cam shape of the rotating cam.

For example, as disclosed in Japanese Patent Application Laid-Open No. 56-29056, in a fuel injection pump, a receiving portion is provided at a lower end portion of a plunger, and a roller is interposed below the receiving portion to surround a cam. A contacting technique is disclosed. In the technique disclosed in this publication, a roller that slides on a cam moves up and down to press a receiving portion of the plunger to move the plunger up and down. When the plunger moves downward, the discharge valve closes, and at the same time, the suction valve opens to introduce fuel into the pump chamber. When the plunger moves upward, the suction valve closes, and at the same time, the discharge valve opens and pressurizes. The discharged fuel is discharged.

There are various cam shapes of such cams. For example, an engine having a sine curve cam diagram as shown in FIG. 10 (sine cam) or an engine having a cam curve as shown in FIG. A polydan intercom used for the intake and exhaust valves of the above is known. In FIG. 10, (a)
11 shows a displacement (lift) diagram of the sine cam, (b) shows a velocity diagram, and (c) shows an acceleration diagram. Similarly, in FIG.
(A) shows a displacement diagram of the polydyne cam, (b) shows a velocity diagram, and (c) shows an acceleration diagram.

[0006]

However, in the case of the sine cam shown in FIG. 10, the absolute value of the acceleration is (c)
As is clear from FIG. 5, since it becomes maximum at the top dead center and the bottom dead center of the plunger, at the time of switching between discharge and suction,
In high-speed rotation, the suction valve starts to open before the discharge valve is fully closed, and fuel moves from the discharge port to the suction port (through).
Occurs, and the pump performance is disadvantageously reduced.

On the other hand, a polydyne cam having the characteristics shown in FIG. 11 is generally used for an intake / exhaust valve of a gasoline engine, and has a structure in which the valve is securely closed. The intake and exhaust valves of the pump may have the same configuration, and the intake and exhaust valves may have a camshaft. However, in the case of a pump, suction and exhaust are performed once, twice (double action), or three times (triple action) during one rotation. In contrast, gasoline engine intake and exhaust valves open early at the beginning of each intake and discharge process and close early at the end of each process. When the polydyne cam is applied to the pump as it is, the discharge valve opens quickly and closes slowly, but the suction valve opens slowly and closes quickly, causing pulsation, and there is a problem that the pump performance deteriorates.

Accordingly, an object of the present invention is to provide a cam of a plunger pump capable of improving pump performance.

[0009]

In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a reciprocating movement of a plunger sliding in a cylinder and a suction valve for sucking fluid and pressurization in the cylinder. In a plunger pump that opens and closes a discharge valve that discharges the discharged fluid, a cam shape of a cam that makes circumferential contact with the plunger and reciprocates the plunger,
This is a cam curve in which the plunger displacement speed and displacement acceleration are zero at the top dead center and the bottom dead center of the plunger.

According to the first aspect of the present invention, when the plunger rises due to the rotation of the cam, the fluid is pressurized in the cylinder, the suction valve is closed and the discharge valve is opened to discharge the fluid. When the plunger descends after reaching the top dead center, the discharge valve is closed and the suction valve is opened to suck the pressurized fluid. In such a suction and discharge process, the displacement speed and displacement acceleration of the plunger become zero at the top dead center and the bottom dead center of the plunger, so that the suction valve and the discharge valve are always closed, so that the fluid escapes from the suction side to the discharge side. There is no (through), and the pump performance is improved.

According to a second aspect of the present invention, in the first aspect of the present invention, the cam shape is such that the absolute value of the displacement acceleration after passing through the top dead center and the bottom dead center of the plunger is the top dead center. And a cam curve larger than the absolute value of the displacement acceleration toward the next bottom dead center and top dead center after passing through the bottom dead center.

According to the second aspect of the present invention, the opening and closing of each of the suction valve and the discharge valve is such that the valve opens quickly and closes slowly after passing near the top dead center and bottom dead center of the plunger. Therefore, high-pressure pulsation and low-pressure pulsation are reduced.

According to a third aspect of the present invention, in the first aspect, the plunger pump is a fuel supply pump for supplying fuel to a plurality of injectors, and each of the injectors is periodically shifted in time. It is configured to inject fuel, and the cam has a cam peak corresponding to the number of injectors.

According to the third aspect of the present invention, by forming the cam ridge for reciprocating the plunger in correspondence with the number of injectors of the fuel supply pump, fuel is injected from each injector at a staggered time. At this time, the discharge pressure in each injector becomes constant.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG.
An embodiment of the present invention will be described in detail with reference to FIG. A fuel injection device 3 using a high-pressure pump (plunger pump) 1 according to an embodiment of the present invention injects gasoline directly into a combustion chamber (cylinder) of a gasoline engine, and is used for a so-called direct injection gasoline engine. Things.

As shown in FIG. 5, the fuel injection device 3 includes a fuel tank 5, a low-pressure pump 7, a high-pressure pump 1, and an accumulator for accumulating fuel pumped from the high-pressure pump 1 disposed in the fuel tank 5. A circuit is configured by connecting a common rail 9, a high-pressure regulator 11, and a low-pressure regulator 13 as devices. The low pressure pump 7 includes a fuel tank 5
The internal fuel (gasoline) is pumped to the high-pressure pump 1, and a filter 15 is interposed between the fuel and the high-pressure pump 1.

The high-pressure pump 1 (plunger pump) pressurizes the fuel supplied from the low-pressure pump 5 to a high pressure, which will be described in detail later. The high-pressure pump 1 is driven by an engine and pressurizes the fuel to a high pressure. Feed it to the common rail 9.

The common rail 9 has first to sixth six injectors 17a, 17b, 17c, 17d, 17
e and 17f are connected, and the fuel accumulated at a high pressure by the common rail 9 is injected into the cylinder of the engine from the first to sixth injectors 17a to 17e in a uniform state.

Next, the configuration of the high-pressure pump 1 will be described with reference to FIG. The high-pressure pump 1 generally has a plunger 24
Main body 25 in which an inlet 21 for fuel (gasoline) and an outlet 23 are formed.
It comprises a lower body 31 containing a cam 29 according to the present invention.

The inlet 21 of the upper body 19 is adapted to receive the fuel supplied from the low-pressure pump 7.
Introducing passage 3 into pump chamber 33 formed in pump body 19.
5 are connected. The outlet 23 is connected to the pump chamber 3
3 through a lead-out passage 37, and the pump chamber 3
The fuel pressurized at 3 is discharged.

As shown in FIG. 3, the inlet passage 35 and the outlet passage 37 are interposed with leaf valves 39a and 39b, respectively. The leaf valve 39a opens,
The discharge side leaf valve 39b is closed. On the other hand, in the discharge step, the pump chamber 33 is pressurized to open the discharge side leaf valve 39b and close the suction side leaf valve 39a.

Referring again to FIG. 1, the pump body 19 is fixed to the upper body 25 by screws 41, and the plunger 24 slides along the barrel 43. The above-described pump chamber 33 is defined at the upper end of the plunger 24, and the lower end of the plunger 24 is in circumferential contact with the cam 29 via the receiving member 45 and the circumferential contact member 51.

Around the plunger 24, a bellows 53 for maintaining the periphery of the plunger in a liquid-tight manner is provided so as to be expandable and contractible in accordance with the reciprocating operation of the plunger 24. Reference numeral 55 denotes a port for communicating the bellows chamber with the tank 5 so that pressure is not applied to the bellows 53.

The lower main body 31 has a drive shaft 27 of the engine.
Is fixed, and the rotation of the cam 29 in conjunction with the rotation of the drive shaft of the engine reciprocates the plunger 24 as a driven member that is in circumferential contact with the cam.

Here, the cam shape of the cam 29 according to the present invention will be described. The cam 29 is, as shown in FIG.
The base circle 59 is formed with three peaks 61a, 61b, and 61c, which corresponds to a case where the number of cylinders of the engine is six, and is a so-called triple cam.

FIG. 4 shows a cam diagram of the cam 29. As shown in FIG. In FIG. 4, (a) is a displacement (lift) curve,
(B) is a velocity curve, and (c) is an acceleration diagram, showing one of the three peaks of the cam described above, in which the angle of the cam is from 0 to 120 °. In the cam curve of FIG. 4, A indicates the top dead center of the plunger 24, and B indicates the bottom dead center. FIG. 4 shows the rotation angle of the cam on the horizontal axis,
The left vertical axis shows the displacement amount, and the right vertical axis shows velocity and acceleration.

In the cam diagram shown in FIG. 4, the displacement speed and the displacement acceleration of the plunger become 0 at the top dead center A and the bottom dead center B of the plunger. In this embodiment,
The cam diagram is an asymmetrically deformed trapezoid. Also, 0 °
From 48 ° to the fuel discharge period (discharge process),
The range from 48 ° to 120 is an example of the inhalation period (inhalation step).

That is, the displacement curve (a) reaches the top dead center A at a rotation of 48 ° from the bottom dead center B (rotation angle 0), gradually descends from the top dead center A, and rotates at a 120 ° rotation. It reaches bottom dead center B. In this case, as shown by e and f in the figure, the width e of the rising portion is different from the width f of the falling portion, and the width of the rising portion e is smaller than f. That is, in the vicinity of the top dead center A, the rising is sharp and the falling is gentler than this.

On the other hand, the speed curve gradually rises from the bottom dead center B, reaches a maximum around a rotation angle of 18 °, gradually decreases, and becomes zero at a rotation angle of 48 ° at the top dead center. From the rotation angle of 48 °, the speed becomes minimum around 75 °, gradually increases from here, and becomes zero at 120 ° which is the bottom dead center.

The acceleration curve (c) has a rotation angle of 0 to 4 °.
Rapidly increases in the range, becomes constant around 4 ° to 15 °, decreases rapidly, reaches a minimum around 25 °, becomes constant again around 41 °, and then rises to 48 ° The acceleration becomes 0 at the top dead center A of. And 48 °
From 54 ° to 70 °, then stabilizes from 54 ° to 70 °, then rises, stabilizes from around 84 ° to 109 °, then drops from 109 ° to 120, bottom dead center At B, the acceleration becomes zero.

Next, the operation of the cam diagram will be described.

When the cam 29 starts rotating from a rotation angle of 0 °, which is the position of the bottom dead center B, the plunger 24 rises and pressurizes the fuel in the pump chamber 33 in the cylinder. in this case,
The suction valve 39a is closed, the discharge valve 39b is opened, and the fluid is discharged. Subsequently, the moving direction of the plunger 24 changes from the top dead center A and descends. When the plunger 24 descends, the discharge valve 39b is closed and the intake valve 39a is opened to suck the fuel from the intake port. In the suction process and the discharge process, the displacement speed and the displacement acceleration of the plunger 24 become 0 at the top dead center A and the bottom dead center B of the plunger 24, so that the suction valve 39a and the discharge valve 39b can be closed without fail. . Therefore, there is no escape of fluid from the suction side to the discharge side at the top dead center A and the bottom dead center B where the discharge and the suction are switched, and the pump performance is improved.

On the way to the top dead center A (or the bottom dead center B), a gentle curve is formed near the top dead center A (or the bottom dead center B). Because of the sharp curve, the opening and closing of each of the suction valve 39a and the discharge valve 39b is such that the suction valve (or discharge valve) opens early after passing near the top dead center A and the bottom dead center B of the plunger, In addition, since the shutter can be closed slowly, high-pressure pulsation and low-pressure pulsation are reduced.

In addition, the acceleration at the top dead center A and the bottom dead center B is set to 0, and the acceleration just before the top dead center A and the bottom dead center B is limited (made gentle). Jumping of each of the valve 39a and the discharge valve 39b can be prevented.

In this embodiment, since the acceleration immediately after the start of discharge (or immediately after the start of suction) is rapidly increased to be faster, the discharge valve (or the suction valve) is opened earlier to reduce the pressure at the start of discharge. The pressure rise is accelerated, and after a certain pressure rise, a gentle curve is formed. After reaching top dead center A (bottom dead center B), the discharge valve 39
Since b (or the suction valve) is closed and the suction valve 39a (or the discharge valve) is opened earlier, a rapid pressure drop can be prevented. Moreover, in the present embodiment, the acceleration does not have a discontinuity point, so that no jump or vibration occurs.

FIG. 6 shows another embodiment. In this embodiment, as in the case of FIG.
And the bottom dead center B, the displacement speed and the displacement acceleration of the plunger are set to be zero. Also in this embodiment, the cam diagram has an asymmetrically deformed trapezoidal shape, but the fuel discharge period (discharge step) is from 0 ° to 60 °,
The embodiment differs from the above-described embodiment in that up to 20 is the inhalation period (inhalation step).

That is, the displacement curve (a) rises from the bottom dead center B (at an angle of 0), and rotates at 60 ° to reach the top dead center A
, Descends from the top dead center A, and reaches the bottom dead center B when rotated by 120 °. In this case, similar to the above-described embodiment,
The width e of the rising portion is different from the width f of the falling portion,
The width of the rising portion e is wider than f. That is, in the vicinity of the top dead center A, the rising is gentle, and the falling is sharper than this.

On the other hand, the speed curve (b) gradually rises from the bottom dead center B, reaches a maximum around a rotation angle of 24 °, gradually decreases, and becomes zero at a top angle of a rotation angle of 60 °.
From the rotation angle of 60 °, the speed becomes minimum around 84 ° and gradually increases from here, and becomes zero at 120 ° which is the 120 bottom dead center.

The acceleration curve suddenly increases in the range of the rotation angle from 0 to 6 °, becomes constant around 6 ° to 18 °, rapidly decreases, reaches a minimum around 30 °, and then returns again. It becomes constant up to around 51 ° and then rises to zero acceleration at top dead center A. Then, it suddenly drops from 60 ° to around 66 °, becomes constant from 66 ° to 78 °, rises, becomes constant from around 93 ° to around 112 °, and falls from 112 ° to 120. At the bottom dead center B.

In the embodiment shown in FIG. 6, since the suction period and the discharge period are the same, low-pressure pulsation is likely to occur when the suction period is short, and high-pressure pulsation is likely to occur when the discharge period is short. Unevenness can be prevented.

In this embodiment, since a triple cam is used, there are three peaks, and as shown in FIG. 8, discharge is performed in three cycles from six injectors. In addition, since the pump pressure at the time of discharge from each injector can be made equal, the injection pressure of each injector (for example, the first injector 17a) is always constant.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention. For example, as shown in FIG. 7, the shape of the cam may be determined so that the state of acceleration 0 and velocity 0 has a constant width H at top dead center A and bottom dead center B, respectively.

Further, the present invention is not limited to the triple cam. For example, when the number of cylinders of the engine is four, a so-called double cam having two ridges of a cam curve is used, as shown in FIG. The injection pressure can be kept constant.

Further, in the present embodiment, the injection pump has been described as an example. However, the invention is not limited to this, and the invention can be similarly applied as long as the plunger is driven by a cam.

In addition, the same effect can be obtained even if the suction valve and the discharge valve are not limited to leaf valves but are configured to be biased in the closing direction by a spring.

[0046]

According to the first aspect of the present invention, the shape of the cam for reciprocating the plunger is such that the plunger displacement speed and displacement acceleration at the top dead center and the bottom dead center of the plunger become zero.
Since the suction valve and the discharge valve are closed without interruption, there is no escape (through) of the fluid from the discharge side to the suction side, and the pump performance is improved.

According to the invention described in claim 2, according to claim 1,
In addition to the effects of the present invention, the opening and closing of each valve of the suction valve and the discharge valve can be quickly opened after passing the vicinity of the top dead center and the bottom dead center of the plunger and can be closed slowly, so that high pressure pulsation can be achieved. And reduce low pressure pulsations.

According to the third aspect of the present invention, the cam ridge for reciprocating the plunger is formed in correspondence with the number of injectors of the fuel supply pump, so that when the fuel is injected from each injector at a staggered time, The discharge pressure at each injector becomes constant.

[0049]

[Brief description of the drawings]

FIG. 1 is a sectional view of a high-pressure pump using a cam according to the present invention.

FIG. 2 is a sectional view showing the cam shown in FIG.

FIG. 3 is a plan view of a leaf valve provided in a suction passage and a discharge passage.

FIG. 4 is a cam diagram of the cam shown in FIG.

5 is a circuit diagram of an injection device using the high-pressure pump shown in FIG.

FIG. 6 is a cam diagram of a cam according to another embodiment.

FIG. 7 is a cam diagram of a cam according to another embodiment.

FIG. 8 is a diagram showing a relationship between a pump pressure and an injection pressure of an injector when a triple cam is used.

FIG. 9 is a diagram showing a relationship between a pump pressure and an injection pressure of an injector when a double cam is used.

FIG. 10 is a cam diagram of a sine cam used for a conventional cam.

FIG. 11 is a cam diagram of a conventional polydyne cam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-pressure pump (plunger pump) 17a-17f Injector 24 Plunger 29 Cam 41 Cylinder 39a Suction side leaf valve (suction valve) 39b Projection side leaf valve (discharge valve) A Top dead center B Bottom dead center (a) Displacement curve (b) ) Velocity curve (c) Acceleration curve

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akinao Minegishi 3-13-26 Yayumicho, Higashimatsuyama-shi, Saitama Inside of Zexel Higashimatsuyama Plant

Claims (3)

[Claims] 1. A plunger pump which opens and closes a suction valve for sucking fluid and a discharge valve for discharging fluid pressurized in a cylinder by reciprocating motion of a plunger sliding in the cylinder. A cam for a plunger pump, wherein a cam shape of a cam that reciprocates the plunger in contact with the cam is a cam curve in which the plunger's displacement speed and displacement acceleration are zero at the top dead center and the bottom dead center of the plunger. 2. The cam shape is such that the absolute value of the displacement acceleration after passing through the top dead center and the bottom dead center of the plunger becomes the next bottom dead center and the top dead center after passing through the top dead center and the bottom dead center. The cam of the plunger pump according to claim 1, wherein the cam curve is larger than an absolute value of an oncoming displacement acceleration. 3. The plunger pump is a fuel supply pump for supplying fuel to a plurality of injectors, wherein each injector is configured to inject fuel periodically at staggered times, and the number of the cams is equal to the number of injectors. The cam of a plunger pump according to claim 1, wherein the cam has a corresponding cam peak.