JP2572213Y2 - Screw pump - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw pump in which a male rotor and a female rotor meshing with the male rotor are rotatably supported by a housing, and more particularly to a screw pump having a variable internal compression ratio. Related to pumps.

[0002]

2. Description of the Related Art A screw pump having a variable internal compression ratio is already known, for example, from Japanese Utility Model Publication No. 53-40727.

[0003]

[Problem to be solved by the present invention]
In the screw type pump disclosed in Japanese Patent Publication No. 727, in order to change the internal compression ratio, a piston provided on the side of the housing is driven by hydraulic pressure switching of a hydraulic control device provided outside, and the capacity is changed. A special external control mechanism is required to change the value.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a screw-type pump which can change an internal compression ratio with a simple configuration without an external control mechanism.

[0005]

According to the present invention, a suction port is provided at one axial end of a housing, and a suction port is provided at the other axial end of the housing. A guide tube portion provided with a lead-out portion and extending in a direction substantially orthogonal to the axis of both rotors at a portion near the other end in the axial direction is continuously provided, and a high compression position on the inner side and a low compression position on the outer side are provided. A piston which is movable between the two and forms a discharge port in cooperation with the outlet portion is slidably fitted to the guide tube portion, and the piston is at a high compression position at an inner end of the piston. In the state, the first and the substantially continuous with the inner surface of the housing
A second inner end surface and a third inner end surface substantially continuous with the inner surface of the outlet portion are provided, and a passage is formed in the piston to communicate a back pressure chamber formed facing the back of the piston to the discharge port.
The piston is spring-biased toward the low compression position ,
Biasing force, pressure acting on the first and second inner end faces and third inner end
Low compression on piston based on pressure acting on surface
Force to the position side and the back through the passage from the discharge port.
High compression applied to piston based on pressure acting on pressure chamber
Piston position by balance with force toward the position side
Is determined .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 to 6 show an embodiment of the present invention. FIG. 1 is a view showing an intake system of an engine, FIG. 2 is a cutaway longitudinal side view of a mechanical supercharger, and FIG. FIG. 4 is a sectional view taken along line 3-3 of FIG. 2, FIG. 4 is a sectional view taken along line 4-4 of FIG. 2, FIG. 5 is a view for explaining the force acting on the piston, and FIG. It is a figure which shows the direction of the load to.

First, in FIG. 1, an intake passage 1 and an exhaust passage 2 are connected to an engine body E.
An air cleaner A is connected to an upstream end of the air cleaner A. Moreover in the middle of the intake passage 1, the mechanical supercharger SC as a screw pump in order from the upstream side, the intercooler IC and a throttle valve V _TH and is interposed, the mechanical supercharger SC and the intercooler A bypass passage 3 bypassing the IC is connected to the intake passage 1. Thus, the bypass passage 3
Bypass valve V _BP is interposed in.

In FIGS. 2, 3 and 4, the mechanical supercharger SC comprises a male rotor 7 and a female rotor 8 meshing with each other and rotatably supported by a housing 6. Both rotors 7, which are rotationally driven by the main body E,
8, the suction port 4 on one axial side of the housing 6
Is sucked out from the outlet port 5 at the other end in the axial direction.

The housing 6 includes a cylindrical body 9 formed in a cylindrical shape with one end closed at one end by an end wall 9a, and an end wall member 10 attached to the cylindrical body 9 so as to cover an open end thereof. And the suction port 4 is bored in the end wall 9a. In addition, cylindrical body 9
Are formed in a cross-sectional shape corresponding to the rotation locus drawn by the radially outer ends of the rotors 7 and 8. That is, the cylindrical body 9 includes an arc-shaped first inner surface 9 b facing the outer periphery of the male rotor 7,
An arc-shaped second inner surface 9c facing the outer periphery of the female rotor 8 is provided.

The rotors 7, 8 are fixed to rotating shafts 11, 12, respectively.
One end of 2 is supported on the end wall 9a of the cylinder 9 via bearings 13 and 14, respectively. Further, a cover 15 that forms a gear chamber 16 between the end wall member 10 and the end wall member 10 is connected. The other ends of the two rotation shafts 11 and 12 pass through the end wall member 10. It is protruded into the gear chamber 16. Thus, a seal member 17 and a pair of bearings 18 are interposed between the rotating shaft 11 and the end wall member 10, and the rotating shaft 12 and the end wall member 10 are provided.
A seal member 19 and a pair of bearings 20 are interposed between them.

Gears 22 and 23 meshing with each other are fixed to both rotating shafts 11 and 12 in the gear chamber 16, and a gear 24 is fixed to the rotating shaft 11 in addition to the gear 22.
On the other hand, one end of a shaft 25 having an axis parallel to the rotating shafts 11 and 12 is rotatably supported on the end wall member 10 via a bearing 26. The shaft 25 extends through the cover 15 and extends outward. Protrude into. Thus, a seal member 27 and a pair of bearings 28 are interposed between the shaft 25 and the cover 15. Further, a gear 29 meshing with the gear 24 is fixed to the shaft 25 in the gear chamber 16, and a pulley 30 is fixed to an outer end of the shaft 25 protruding from the cover 15. Power from the crankshaft 21 (see FIG. 1) of the engine body E is transmitted to the pulley 30 via an endless belt (not shown), whereby the male rotor 7 and the female rotor 8 mesh with each other. It will be driven to rotate.

At a position corresponding to the meshing portion of the male rotor 7 and the female rotor 8, a side of the cylindrical body 9 in the housing 6 has a moving direction 32 substantially orthogonal to the axis of the rotors 7, 8.
And a low compression position on the outer side along the moving direction 32 (a position indicated by a solid line in FIGS. 2 and 3). A piston 31 is provided so as to be movable between the two. That is, a guide cylinder 33 having a circular cross section extending in a direction perpendicular to the axes of the rotors 7 and 8 is integrally provided on the side of the cylinder 9, and the piston 31 can move in the movement direction 32. And is slidably fitted to the guide tube portion 33.

The piston 31 is formed in a bottomed cylindrical shape with its closed end facing the inside of the housing 6, and has a flange portion 31 a extending outward in the radial direction at its open end, that is, the outer end. On the other hand, a large-diameter hole 33a is provided on an inner surface of the guide cylinder 33 near the outer end in the axial direction through a step 33b facing outward so as to enable the flange 31a to move along the moving direction. The axial position of the piston 31 is regulated by the case 40 coupled to the outer end of the guide cylinder 33 and the step 33b. An axially extending groove 34 is provided at one circumferential position of the flange 31 a of the piston 31, and a positioning pin 37 that engages with the groove 34 is fitted into the guide cylinder 33. Therefore, the piston 31 is prevented from rotating around its axis and slides along the movement direction 32.

The discharge port 5 is connected to the male rotor 7
And a leading portion 35 provided at the other end in the axial direction of the housing 6 at a position corresponding to the meshing portion of the female rotor 8, and is formed in cooperation with the piston 31. A protruding portion 9d provided at the other end of the cylindrical body 9 in the housing 6 so as to have a larger protruding amount outward from the first and second inner surfaces 9b and 9c toward the other end in the axial direction; And a lead-out cylinder 36 provided in the member 10. Meanwhile, inner end along the moving direction 32 of the piston 31, the distance from the intake port 4 of the ejection start position P _E of the discharge port 5 when the piston 31 is in the high compression position is in the low compression position The discharge start positions P _E ′ and P _E ′ are formed so as to be larger than the distance from the suction port 4 at the time of the discharge start position. 1 inner end surface 31b and second inner end surface 31 substantially continuous with second inner surface 9c
c and a third inner end surface 31 d substantially continuous with the inner surface 35 a of the lead-out portion 35 are provided at the inner end of the piston 31. That is, when the piston 31 is at the high compression position, the portion indicated by the slant chain line on the lower right in FIG. 4 becomes the discharge port 5 and becomes the first and second inner end surfaces 31b and 31c and the third inner end surface 31d.
When the piston 31 is at the low compression position, the first and second inner end surfaces 31 are connected to the discharge start position _PE .
b, 31c are the first and second inner surfaces 9b,
9c, the portions indicated by oblique dashed lines on the lower left and lower right in FIG. 4 become the discharge ports 5, and the grooves of both rotors 7, 8 communicate with the discharge ports 5 first according to their rotation. These two positions are the discharge start positions P _E ′ and P _E ′. Thus, when the piston 31 is set at the low compression position and the discharge start positions P _E ′ and P _E ′ are closer to the suction port 4, the internal compression ratio ε becomes 1.0, and the discharge start position is set at the high compression position of the piston 31. the internal compression ratio ε is, for example 1.3 when allowed to separate the P _E from the intake port 4.

The outer end of the guide cylinder 33 is closed by a case 40 forming a back pressure chamber 39 with the piston 31. The case 40 forms an atmospheric pressure chamber 45 therebetween. A pair of case members 43 and 44 are connected to each other, and an open hole 50 for opening the atmospheric pressure chamber 45 to the outside is formed in the case member 43.

In the case 40, a through hole 47 is formed in the center of a case member 44 which divides the back pressure chamber 39 and the atmospheric pressure chamber 45. A cylindrical bearing sleeve 48 is formed in the through hole 47. It is fitted and fixed. On the other hand, the piston 31
Is integrally provided with a connecting rod 31e extending along the moving direction 32. The connecting rod 31e slidably penetrates the bearing sleeve 48 and protrudes into the atmospheric pressure chamber 45. Moreover, the connecting rod 3 in the atmospheric pressure chamber 45
1e, a retainer 41 is fixedly attached to the end of the connecting rod 31 between the retainer 41 and the case member 44.
The spring 42 is contracted around e. This spring 42
The spring exerts a direction of separating the retainer 41 from the case member 43, that is, a spring force for urging the piston 31 toward the low compression position.

A communication hole 49 as a passage communicating with the back pressure chamber 39 is formed in the piston 31 so as to open to the third inner end face 31d. Communicates with the discharge port 5.

[0019] In FIG. 1, operation of the bypass valve driving means 55 for opening and closing the bypass valve V _BP is intended to be controlled by the control means C including a microcomputer, the control means C, the throttle valve V _TH of the throttle opening theta _TH, engine speed N _E, to control the operation of the bypass valve driving means 55 in accordance with the bypass opening theta _BP of the bypass valve V _BP, and the supercharging pressure P _2. The order control unit C, the rotation speed sensor S _NE for detecting the engine speed N _E,
Throttle opening detecting sensor S _TH for detecting the throttle opening theta _TH, as well as from the supercharging pressure detection sensor S _P2 provided in the intake passage 1 at the merging portion of the bypass passage 3 on the downstream side of the intercooler IC Each signal is input.

Next, the operation of this embodiment will be described with reference to FIG. 5. A force F _L toward the low compression position and a force F _H toward the high compression position are applied to the piston 31. And the balance of the forces F _L and F _H causes the position of the piston 31, that is, the internal compression ratio ε of the mechanical supercharger SC.
Is determined.

Here, the projected area of the first and second inner end faces 31b and 31c of the piston 31 is A _R , the projected area of the third inner end face 31d of the piston 31 is A _P , and the back pressure of the piston 31 is A _P. The area facing the chamber 39 is A _U , the pressure acting on the third inner end face 31d and the pressure acting on the back pressure chamber 39 via the communication hole 49, that is, the supercharging pressure of the mechanical supercharger SC is P ₂ , When the pressure acting on the first and second inner end surfaces 31b and 31c is P ₂ ′, and the spring load of the spring 42 is F _S , the force FL toward the low compression position and the force F _L toward the high compression position And the force F _H toward

Force F _H toward the high compression position side: P ₂ × A _U Force F _L toward the low compression position side; A _R × P ₂ ′ + A _P × P ₂ + F _S Thus, F _H If> F _L , the piston 31 moves to the high compression position, and if F _L > F _H , the piston 31 moves to the low compression position, so that A _R , A _P , A _U , and F _S are appropriately set. With this setting, the position of the piston 31, that is, the internal compression ratio ε can be switched according to the supercharging pressure P ₂ .

The change in the force acting on the piston 31 in accordance with the change in the supercharging pressure P ₂ will be described. First, FIG.
In the state where the supercharging pressure P ₂ = 0, only the load F _{S of the} spring 42 is acting on the piston 31 and the piston 3
1 is stably at the low compression position.

When the piston 31 is in the low compression position, internal compression occurs between the first and second inner end surfaces 31b and 31c of the piston 31 and the outer circumferences of the rotors 7 and 8. but not extent has occurred gap enough to create a pressure loss due to flow of air, the supercharging pressure P ₂ is FIG. 5 (b), the when increases as shown by (c), first and second inner end face 31b in the portion corresponding to 31c has a supercharging pressure P ₂ before the pressure reaches the third inner end surface 31 _d to rise toward the third inner end surface 31d side, the first and second inner end surface 31b, The average value of the pressure P ₂ ′ acting on 31c is lower than the supercharging pressure P ₂ . On the other hand, the back pressure chamber 39 supercharging pressure P ₂ is acting entirely. For this reason, in the process of increasing the boost pressure P ₂ , the force F _H (P
₂ × A _U ) is the force _FL (A _R × P) toward the low compression position.
₂ ′ + A _P × P ₂ + F _S ) (F _H > F _L ), and the piston 31 moves to the high compression position side.

When the piston 31 moves to the high compression position, the pressure distribution acting on the inner end of the piston 31 is as shown in FIG.
(D), the first and second inner end surfaces 31
b, 31c, internal compression occurs,
The pressure is gradually increased toward the third inner end face 31d, and the average value of the pressure P ₂ ′ is considerably smaller than the supercharging pressure P ₂ , so that the high compression position of the piston 31 is stably maintained. Is done.

With the piston 31 in the high compression position,
When the supercharging pressure P ₂ decreases as shown by FIG. 5 (e), the first
And the second inner end face 31b, which occurs inside the compression remains at the portion corresponding to 31c, the boost pressure P ₂ 5
As shown in (f), when the temperature is further reduced, the first and second
The average value of the pressure P ₂ ′ acting on the inner end faces 31b and 31c becomes larger than the supercharging pressure P ₂ . Therefore the force F _L (A _R × in reduction process of the supercharging pressure P ₂ toward the low compression position side
P ₂ '+ A _P × P ₂ + F _S ) is larger than the force F _H (P ₂ × A _U ) toward the high compression position (F _L > F _H ),
The piston 31 is moved to the low compression position side.

When the piston 31 moves to the low compression position, the pressure distribution acting on the inner end of the piston 31 becomes as shown in FIG. 5 (g), and the pressures acting on the inner end and the outer end of the piston 31 become equal. Therefore, the piston 31 is stably maintained at the low compression position by the load F _S of the spring 42.

[0028] Here, becomes as shown in FIG. 6 when showing the change of the load acting on the piston 31 in accordance with the change of the supercharging pressure P _2, for example, when the supercharging pressure P ₂ is P ₂₀ kg / cm ² or more Among the forces acting on the piston 31, the force toward the low compression position becomes large, and when the supercharging pressure P ₂ is less than P _{2 O} kg / cm ² , the force acting on the piston 31 toward the high compression position becomes small. It will be great. Thus, in the supercharged compressor SC,
And eliminates the need to provide a mechanism for varying the internal compression ratio ε to the outside, it is possible to automatically change the internal compression ratio ε in accordance with the supercharging pressure P _2.

In the above embodiment, the communication hole 49 for communicating the back pressure chamber 39 with the discharge port 5 is provided in the piston 31. However, the communication hole 49 may be provided in the guide cylinder 33. Further, the piston 31 and the guide cylinder 33 may be disposed at positions shifted from the meshing portion of the rotors 7 and 8.

[0030]

As described above, according to the present invention, a suction port is provided at one axial end of the housing, and a lead-out portion is provided at the other axial end of the housing. A guide cylinder portion extending in a direction substantially orthogonal to the axis of both rotors at a portion near the other end in the direction is continuously provided, and is movable between a high compression position on the inside and a low compression position on the outside. A piston forming a discharge port in cooperation with the lead-out portion is slidably fitted to the guide cylinder, and the inner end of the piston is attached to the inner surface of the housing while the piston is at the high compression position. first and second inner end surface substantially continuous, deriving section inner surface is provided with a substantially continuous third inner end face of the causes to face the back of the piston communicating the back pressure chamber formed in the discharge port
Passage is formed in the piston and acts constantly on the piston
Low compression position spring bias the first and second inner end surface of the置側 that
Based on the pressure acting on the third inner end face
Force applied to the piston to the low compression position and discharge
Based on the pressure acting on the back pressure chamber from the port through the passage
With the force applied to the piston toward the high compression position
Since the piston can be operated so that the piston position is determined by the bias , the internal compression ratio can be automatically switched according to the supercharging pressure. Besides, the piston
Is simply discharged through a passage provided in the piston.
It is enough to introduce the supercharging pressure at the output port, and
Since there is no need to control separately, it controls unwanted next from outside for changing the internal compression ratio, for example above
Special control valve mechanism for back pressure control and external connection
Since tubes and the like are not required, the overall structure is simple,
Greatly contributes to cost savings and improved maintenance workability
can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing an intake system of an engine.

FIG. 2 is a cutaway longitudinal side view of the mechanical supercharger.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 2;

FIG. 5 is a diagram for explaining a force acting on a piston.

FIG. 6 is a diagram showing a change in a direction of a load on a piston according to a change in a supercharging pressure.

[Explanation of symbols]

4 ... Suction port 5 ... Discharge port 6 ... Housing 7 ... Male rotor 8. ········ Female rotor 9b, 9c ······················ Piston 31b , 31c ··· First and second inner end faces 31d of the piston . ····· Third inner end surface 33 of the piston ············································· Inner surface 39 ··· ····· Back pressure chamber 42 ····· Spring 49 ······ Communication hole F _H as passageway ··········· toward high compression position side as spring load SC ········ screw pump as a force F _S ········ spring bias towards the force F _L ········ low compression position side Mechanical Supercharger

Claims (1)

(57) [Scope of request for utility model registration] A male rotor (7) and said male rotor (7)
In a screw type pump in which a female rotor (8) meshing with a housing is rotatably supported on a housing (6), a suction port (4) is provided at one axial end of the housing (6), and the housing (6) is provided with a suction port (4). ), A guide portion (35) is provided on the other end side in the axial direction, and a guide cylinder portion extending in a direction substantially orthogonal to the axis of both rotors (7, 8) at a portion near the other end in the axial direction. (33) are connected to each other, and are movable between a high compression position on the inner side and a low compression position on the outer side, and form a discharge port (5) in cooperation with the outlet section (35). The piston (31) is slidably fitted to the guide cylinder (33), and the inner end of the piston (31) has a housing (6) with the piston (31) in the high compression position.
The first and second inner end surfaces (31b, 31c) substantially continuous with the inner surfaces (9b, 9c) of the lead portion and the inner surface (35) of the lead-out portion (35).
a) and a third inner end surface (31d) substantially continuous with
A passage (49) for communicating a back pressure chamber (39) formed facing the back of the piston (31) to the discharge port (5 ).
Is formed on the piston (31), and the piston (31) is biased toward the low compression position by a spring (42) , and the spring biasing force is applied.
(F _S) and the first and second inner end face (31b, 31c) to create
Pressure (P ₂ ′) and the third inner end face (31d)
To the piston (31) based on the pressure (P ₂ )
Force (F _L ) toward low compression position and discharge port
Acts on back pressure chamber (39) from (5) via passage (49)
To the piston (31) based on the pressure (P ₂ )
By balance with force (F _H ) toward high compression position
A screw pump wherein the position of the piston (31) is determined .