JPH11247765A - Compound gear pump and hydraulic circuit of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of abrasion and seizure in an outer rotor or the like which may be caused by foreign materials contained in oil. SOLUTION: In a compound gear pump, external teeth 26 are formed on an outer periphery of an outer rotor 23 of an internal gear pump 1 composed of an inner rotor 22 and the outer rotor 24. An external gear pump 2 is composed of an independent first rotor 30 provided with external teeth which are externally fitted to the teeth 26. One more second rotor 51 is arranged between the first rotor 30 composing the external gear pump 2 and an intake passage 6 of the internal gear pump 1, which rotor 51 has external teeth 52 meshed with the external teeth 26 of the outer rotor 24 of the internal gear pump 1. Each one side of the external teeth 52 of the second rotor 51 and the external teeth 26 of the outer rotor 24 is faced into the intake passage 6 of the internal gear pump 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound gear pump and a hydraulic circuit for an engine using the same.
A compound gear pump suitable for supplying hydraulic pressure as a drive source of a so-called valve control device that controls the opening / closing timing of intake and exhaust valves and their valve lifts according to the operating state of the engine, and a hydraulic circuit of an engine using the same. About.

[0002]

2. Description of the Related Art Conventionally, as such a compound type gear pump, one described in Japanese Utility Model Laid-Open Publication No. 50-114705 is known. FIG. 5 is a sectional view of a conventional compound gear pump.

[0003] This conventional compound type gear pump has a crescent C between an inner rotor 22 and an outer rotor 24.
So-called crescent type (inner rotor 22
(The difference in the number of teeth between the outer gear 24 and the outer rotor 24 is 2 or more). The external gear pump 2 is configured.

More specifically, the number of internal teeth 31 eccentrically arranged and inscribed in the inner rotor 22 having 24 external teeth.
The outer rotor 24 (tooth difference 7) is
0 is rotatably provided in a large-diameter circular concave portion 41, and the outer teeth 26 having 31 teeth provided on the outer circumference over the entire width in the axial direction are provided with the large-diameter circular shape. The small-diameter circular concave portion 42 formed continuously with the concave portion 41 is rotatably provided so as to mesh with the external teeth 31 of the separately provided rotor 30 having 12 external teeth. And the outer rotor 24
Is rotatably held by the top of the external teeth 26 provided over the entire width in the axial direction sliding on the wall surface of the large-diameter circular concave portion 41.

FIG. 6 shows a known hydraulic circuit of an engine using the compound gear pump.

In the hydraulic circuit, the internal gear pump 1 supplies oil from an oil pan 7 sucked from a suction passage 6 to a main gallery 5 of an engine having an oil filter 10.

The external gear pump 2 sucks oil from a suction passage 13 in the main gallery 5 downstream of the oil filter 10 and supplies the oil to a valve control device.

[0008]

However, in such a conventional compound gear pump, in order to rotatably hold the outer rotor, the outer rotor is provided with the top of the external teeth provided over its entire width in the axial direction and a large-diameter circular shape. Since the contact surface pressure depends on the sliding contact with the wall surface of the concave portion, the contact surface pressure at the top increases, and the abrasion between the casing and the outer tooth top of the outer rotor is likely to occur,
In particular, when foreign matter or the like contained in the oil enters between the casing and the external teeth of the outer rotor, abrasion is more likely to occur, and in the worst case, seizure may occur.

[0009] An object of the present invention is to provide a composite capable of suppressing the occurrence of abrasion and seizure caused by foreign substances or the like contained in oil entering between the casing and the external teeth of the outer rotor. SUMMARY OF THE INVENTION An object of the present invention is to provide a type gear pump.

In the above-described conventional hydraulic circuit of the engine, the internal gear pump 1 supplies the oil in the oil pan 7 sucked from the suction passage 6 to the main gallery 5 of the engine having the oil filter 10. In addition, the external gear pump 2 draws oil from the suction passage 13 of the main gallery 5 downstream of the oil filter 10 and supplies the oil to the valve control device. Are transported to the suction passage side of the external gear pump 2 while being sandwiched between the external teeth 26 of the outer rotor 24 of the internal gear pump 1 and the inner wall of the concave portion 41. When the foreign matter is discharged again into the oil, the foreign matter does not pass through the oil filter 10 but flows through the suction passage 13 downstream of the oil filter 10. Will be sent to the valve control device side with Le, there is a problem that malfunction or wear of the valve control device generates.

An object of the present invention is to prevent foreign matters from entering between outer teeth of an outer rotor and a casing when oil in an oil pan sucked into a suction passage of an internal gear pump contains such foreign matters. By pushing out the foreign matter from between the external teeth of the outer rotor and pushing it back into the oil on the suction passage side, the oil containing the foreign matter always passes through the oil filter so that the foreign matter can be removed from the valve control device. It can be prevented from being sent to.

[0012]

SUMMARY OF THE INVENTION External teeth are provided on the outer periphery of an outer rotor of an internal gear pump having an inner rotor and an outer rotor, and a separate first rotor having external teeth meshing with the external teeth is provided. An external gear of an outer rotor of the internal gear pump is provided between a first rotor configuring the external gear pump and a suction passage of the internal gear pump, in a compound gear pump configured to form an external gear pump. A second rotor having external teeth meshing with the second gear is provided, and one end of a meshing portion between the external teeth of the second rotor and the external teeth of the outer rotor faces the suction passage of the internal gear pump. As a result, foreign substances such as dust contained in the oil sucked into the suction passage of the internal gear pump and entering between the external teeth of the outer rotor are removed from the outer rotor. It is pushed out to the suction passage side from between the outer teeth in the external teeth of the external and the second rotor of the rotor is meshed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail based on embodiments shown in the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a crankshaft 21.
FIG. 2 is an internal gear pump described in detail later, which is arranged to be driven (see FIG. 2). The internal gear pump 1 sucks oil in an oil pan 7 through an oil strainer 12 and a suction passage 6 and supplies the oil to a main gallery 5 having an oil filter 10. Reference numeral 3 denotes a first relief valve set to a first relief set pressure, which is provided in communication with a main gallery 5 which supplies oil to a sliding portion requiring lubrication of the engine, and a relief passage 8 of which is provided with a suction passage. 6 is connected.

Reference numeral 2 denotes an external gear pump driven by an outer rotor of the internal gear pump, as will be described later in detail. The suction passage 13 is connected to the oil filter 1.
0 is connected to the main gallery 5 downstream of the discharge passage 1
1 is connected to a valve control device described later. 4 is the second
A second relief valve set to a relief set pressure, which is provided in communication with a discharge passage 11 that supplies operating oil to the valve control device, and whose relief passage 9 is connected to a suction passage 13 that communicates with the main gallery 5. Are in communication. The first relief set pressure of the first relief valve 3 is set lower than the second relief set pressure of the second relief valve 4.

Here, the above-mentioned external gear pump 1 and internal gear pump 2 are, as shown in FIGS.
It is configured as a compound gear pump.

That is, the external gear pump 1 is driven by being connected to a crankshaft 21 and has an inner rotor 2 having a predetermined number of teeth (9 in the illustrated example).
2, and an outer rotor 24 having eccentrically arranged and meshing with the inner rotor 22 and having inner teeth 25 having the number of teeth one more than the predetermined number of teeth (ten in the illustrated example), The outer rotor 24 is
Is rotatably accommodated in a large-diameter circular outer rotor accommodating recessed portion 41 formed therein. Further, the casing 40 has a first suction port 29 communicating with the suction passage 6 and a first discharge port 28 communicating with the main gallery 5.

The external gear pump 2 comprises an external tooth 31 which meshes with an outer rotor 24 of the internal gear pump 1 and external teeth 26 formed partially on the outer periphery thereof in the axial direction.
Consists of a separate first rotor 30 formed in the outer peripheral portion, and the first rotor 30 is fixed to the casing in a small-diameter circular first recess 42 formed in the casing 40. It is constituted by being rotatably accommodated by the shaft 32. Furthermore, in the casing 40,
A second suction port 33 communicating with the aforementioned suction passage 13 and a second discharge port 34 communicating with the discharge passage 11 are formed.

A second rotor 51 is arranged between the first rotor 30 constituting the external gear pump 2 and the suction passage 6 of the internal gear pump 1.

On the outer peripheral portion of the second rotor 51, external teeth 52 meshing with the external teeth 26 of the outer rotor 24 of the internal gear pump 2 are provided.

One end of the meshing portion between the external teeth 52 of the second rotor 51 and the external teeth 26 of the outer rotor 24 faces the suction passage 6.

The second rotor 51 includes a casing 40
Is rotatably accommodated in a small-diameter second concave portion 53 formed by a shaft 54 fixed to the casing 40.

As shown in FIG. 3, the outer peripheral portion of the outer rotor 24 is axially adjacent to the external teeth 26 formed partially in the axial direction, and has a large-diameter circular shape of the casing 40. A guide surface 27 that slides on the inner wall of the concave portion 41 is provided, and the outer diameter of the guide surface 27 is set slightly smaller than the outer diameter of the adjacent external teeth 26.

Reference numeral 43 denotes a pump cover, in which the inner rotor 22 and the outer rotor 24 are accommodated in a large-diameter circular recess 41 and the first rotor 30 is formed in a small-diameter circular shape so as to form a required pump chamber. In the first recess 42, the second rotor 51 is joined to the casing 40 that accommodates the second rotor 51 in the small-diameter circular second recess 53, respectively.

Next, a valve opening / closing timing control device as an example of the valve control device will be described with reference to FIG.

The valve timing control apparatus according to the present embodiment mainly includes a rotation phase change section 100 and a hydraulic control section 200.
And

The rotation phase changing unit 100 includes the camshaft 10
The camshaft 102 is provided at one end of the camshaft 2 and transmits the rotational torque of a crankshaft (not shown) to the camshaft 102 and changes the rotational phase of the camshaft 102. An intake and / or exhaust valve (not shown) is engaged with the camshaft 102, and opens and closes as the camshaft 102 rotates.

That is, the rotation phase changing section 100 includes a sprocket section 110 disposed so as to be rotatable relative to the camshaft 102, an end member 120 fixed to the end of the camshaft 102 by bolts, The movable member 130 interposed in the space formed between the member 120 and the member 120 is a main component.

The sprocket portion 110 has a cylindrical main body 111.
A tooth forming member 112 formed with sprocket teeth secured to the cylindrical body by bolts and having an outer peripheral portion meshed with a timing chain driven by a crankshaft; and a cover member 113 secured to the cylindrical member 111 by caulking. Have. A helical spline 114 is formed on a part of the inner peripheral surface of the cylindrical main body 111 near the cover member.

The end member 120 has a substantially stepped cylindrical shape, and has an insertion hole 122 for the bolt 121 penetratingly formed at the center thereof, and an annular recess 123 for accommodating the head of the bolt 121 is formed. ing. Further, a helical spline 124 is formed on a part of the outer peripheral surface of the end member 120 near the cover member 113. Reference numeral 125 denotes a coil spring provided to prevent a collision between the cover member 113 of the sprocket portion 110 and the end member 120.

In the present embodiment, the movable member 130 has a helical spline 124 of the end member 120 and a helical spline 1 of the cylindrical main body on the inner and outer peripheral surfaces.
14 has a ring member 131 formed with helical splines 132 and 133 meshing with each other, and a ring-shaped piston 134 connected by a pin 135 to drive the ring member 131 in the axial direction. Note that the ring member 131 is composed of a first ring member 131a and a second ring member 131b that are divided into two in the axial direction in order to eliminate backlash in spline meshing, and are elastically connected to each other by pins 136. A first hydraulic chamber 137 is provided between the front of the ring-shaped piston 134 and the cover member 113, and a second hydraulic chamber is provided between the back of the ring-shaped piston 134 and the tooth forming member 112 of the sprocket 110. Each of the chambers 138 is defined in a liquid-tight state to constitute a hydraulic actuator, and a ring-shaped piston 134 is provided in the second hydraulic chamber 138.
Further, a coil spring 139 having a relatively large spring constant is provided for pressing and holding the ring member 131 at an initial position (the left end position in the drawing).

The hydraulic control unit 200 is provided with a spool valve 22 for switching and controlling an oil passage described later formed in an oil passage constituting member 210 attached to the engine block.
0, and an electromagnetic actuator 230 that drives the spool valve.

The spool valve 220 has a cylindrical valve body 221 fitted in a hole 211 formed in the oil passage constituting member 210 and a spool 222 slidably provided in the inside thereof for switching a flow path. , The spool 2
22 is urged by a spring 224 in the direction of the initial position (the left end position in the figure). Further, the spool 222
Is driven against the urging force of the spring 224 by the operating rod 231 of the proportional solenoid type electromagnetic actuator 230 fixed to the rocker cover 232.

An oil supply port 234, a first oil supply / discharge port 235, and a second oil supply / discharge port 236 are formed in the oil passage constituting member 210 and the valve body 221 in a corresponding positional relationship. And
The oil supply port 234 communicates with the discharge passage 11 via the oil supply passage 212 and the first oil supply / discharge port 23
5 is connected to the second hydraulic chamber 137 via the first oil supply / discharge passage 213 (including the passage formed in the cover member 113), and the second oil supply / discharge port 236 is connected to the second oil supply / discharge passage 214
(Including the passage formed in the bolt 121 and the end member 120), each is communicated with the second hydraulic chamber 138. The spool 222 has an annular groove 223, and controls the relative positional relationship between the oil supply port 234 and the first oil supply / discharge port 235 and the second oil supply / discharge port 236 so that the first oil supply / discharge port 235 The opening area of the oil supply / discharge port 236 is variably controlled to control the hydraulic pressures of the first and second hydraulic chambers, respectively.

Incidentally, both ends of the spool valve 220 are opened so that oil can be drained. The drained oil falls into the oil pan 7.

The electromagnetic actuator 230 includes a crank angle sensor (not shown), an air flow meter, a water temperature sensor,
Based on input signals from various sensors such as a throttle valve switch, the current operation state of the engine is detected and controlled by a controller 300 that outputs a control signal, and the amount of advance of the operating rod 231 is changed.

In this embodiment having the above-described structure, the inner rotor 22 of the internal gear pump 1 is driven to rotate in synchronization with the crankshaft 21 when the engine is started, and the outer rotor 24 meshing with the inner rotor 22 has a difference in the number of teeth. Because of 1, the inner rotor 22 is driven at substantially the same rotation speed. Then, the oil in the oil pan 7 is sucked in through the suction passage 6 and the first suction port 29 by the volume change of the space caused by the difference 1 in the number of teeth, and is discharged to the main gallery 5 through the first discharge port 28. When the rotation of the crankshaft 21, that is, the engine speed increases and the hydraulic pressure of the main gallery 5 exceeds the set pressure of the first relief valve 3, the first relief valve 3 opens and excess oil is discharged through the relief passage 8. As a result of being escaped, Main Gallery 5
Is maintained at a predetermined oil pressure.

On the other hand, the external gear pump 2 is also driven by the outer rotor 2 driven at substantially the same rotational speed as the inner rotor 22.
4 is driven to rotate together with the first rotor 30, from the main gallery 5 downstream of the oil filter 10 to the suction passage 13.
And sucks oil through the second suction port 33,
Oil is supplied to the discharge passage 11 connected to the valve timing control device as a valve control device via the second discharge port 34. When the oil pressure in the discharge passage 11 exceeds the set pressure of the second relief valve 4, the second relief valve 4 is opened, and excess oil is released through the relief passage 9, so that the discharge passage 11 is set to a predetermined oil pressure. Will be maintained.

As shown in FIG. 2, foreign matter 60 such as dust is contained in the oil sucked into the suction passage 6 of the internal gear pump 1, and the foreign matter is formed outside the outer rotor 24. When the outer teeth 24 of the outer rotor 24 and the outer teeth 52 of the second rotor 51 mesh with each other,
0 is pushed into the suction passage 6 from between the external teeth 26 of the outer rotor 24, supplied to the main gallery 5 together with the oil, and captured by the oil filter 10 provided in the main gallery 5. (The second rotor 5
1 is not provided, the outer rotor 2
Foreign matter 60 that has entered between the external teeth 26 of the
1 may cause abrasion or seizure by contacting the inner wall, or the second suction port 3 of the circumscribed gear pump 2
3, when it comes out of the space between the external teeth 26 of the outer rotor 24 and is discharged again into the oil, the foreign matter 6
0 is sucked together with oil from the suction passage 13 provided downstream of the oil filter 10 without being captured by the oil filter 10, and is supplied to the valve control device side. At this time, the outer rotor 24 rotates while being in sliding contact with the inner wall of the large-diameter circular concave portion 41 of the casing 40 by the guide surface 27 formed on the outer peripheral portion thereof.
0 rotates while being guided by the shaft 32 fixed to the casing 40. Therefore, since the external teeth 26 formed on the outer peripheral portion of the outer rotor 24 do not need to contact the inner wall of the concave portion 41, wear is significantly reduced.

When it is not necessary to change the opening / closing timing of the valve, the operating rod 231 and the spool 222 of the electromagnetic actuator 230 are in the initial positions shown in FIG. 2, that is, the oil supply port 234 and the second oil supply / discharge port 236. And the ring-shaped piston 134 and the ring member 131 are urged by the coil spring 139 to be in the initial position and the second hydraulic chamber 138 in the maximum capacity state and the discharge passage. 1
1 is in communication. At this time, the second hydraulic chamber 138 of the hydraulic actuator forms a closed circuit, and the discharge passage 1
The first oil pressure is maintained at a predetermined relief set pressure as a result of excess oil being released through the relief passage 9.

To change the opening / closing timing of the valve, a predetermined signal is sent from the controller 300, and the operating rod 231 of the electromagnetic actuator 230 advances by a predetermined amount to move the spool 222 rightward from the initial position shown in FIG. Move to For example, the camshaft 102 and the sprocket unit 1
When changing the phase with the maximum, the spool 2
22 is moved to the rightmost end within the allowable range, and the oil supply port 234 and the first oil supply / discharge port 235 are
23, and the second supply / discharge port 236 is opened. Then, oil is supplied from the discharge passage 11 to the first hydraulic chamber 137 via the first supply / discharge passage, and oil in the second hydraulic chamber 138 is drained via the second supply / discharge passage 214 to form a ring. Piston 134
As a result, the ring member 131 is moved rightward against the urging force of the spring 139. At this time, the first hydraulic chamber 138 of the hydraulic actuator forms a closed circuit, and the ring member 131 adjusts the force applied to the ring-shaped piston 134 by the relief set pressure of the discharge passage 11 and the spring 13.
The first hydraulic chamber 138 is maintained at the maximum volume state in which the urging force of the first hydraulic chamber 9 is balanced.

When the ring member 131 moves, the helical spline 12 of the end member 120 meshing with the helical splines 132 and 133 on the inner and outer peripheral surfaces, respectively.
4 and the helical spline 114 of the cylindrical main body 111 are displaced in the axial direction so that the sprocket 110
And the phase of the camshaft 102 are changed. As a result, the opening / closing timing of the intake and / or exhaust valves is maximally changed.

When changing the opening / closing timing of the intake and / or exhaust valves to an intermediate level, the spool 222
Is moved to a predetermined position, and the first oil supply / discharge port 235 is
Is partially connected to the oil supply port 234 via the annular groove 223 and is partially drained, while the second supply / drain port 236 is partially opened. Of the operating rod 231 is controlled. Then, the oil from the discharge passage 11 is regulated while being partially drained, and the first oil is discharged.
The oil in the second hydraulic chamber 138 is supplied to the first hydraulic chamber 137 via the supply / discharge passage 213, and the oil in the second hydraulic chamber 138 is supplied to the second supply / discharge passage 2.
14 is partially drained through the ring-shaped piston 1
Thus, the ring member 131 is held at a position where the ring member 131 is moved rightward by a predetermined amount against the urging force of the spring 139.

Here, the hydraulic actuator of the valve opening / closing timing control device as a valve control device substantially forms a closed circuit, and the volume changes only during the moving operation. At the time of non-moving operation (the moving operation of the hydraulic actuator is performed instantaneously, the hydraulic actuator is in the non-moving operation state during most of the operation of the engine), regardless of the rotation speed of the crankshaft, the engine rotates. As long as the pressure is maintained, the oil pressure in the discharge passage 11 immediately rises and is maintained at a predetermined oil pressure by the set pressure of the second relief valve 4. At this time,
Excess oil is sucked into the external gear pump 2 again or returned to the main gallery 5 via the relief passage 9.

Therefore, during the non-moving operation of the hydraulic actuator, the entire oil flow Q2 discharged from the external gear pump 2 is returned to the main gallery 5, so that the hydraulic pressure of the main gallery 5 does not decrease, and the external gear pump 1
It suffices if there is an ability to discharge only the flow rate Q1 necessary for lubrication of the sliding portion of the engine.

When the ring-shaped piston 134 of the hydraulic actuator moves, the oil returns from the discharge passage 11 and the hydraulic pressure in the main gallery 5 drops momentarily. However, as described above, the hydraulic actuator is substantially Since a closed circuit is formed and the operation time is extremely short, the hydraulic pressure of the main gallery 5 is immediately recovered, and does not adversely affect the engine sliding portion.

As described above, by connecting the relief passage 9 of the external gear pump 2 to the main gallery 5,
Even when the internal gear pump and the external gear pump are used in combination, the discharge capacity of the internal gear pump must be higher than the flow rate Q1 required for lubricating the sliding parts of the engine, as in the related art. Therefore, it is possible to prevent the internal gear pump 1 from increasing in size. Therefore, an increase in power consumption can be avoided by that amount, and fuel efficiency can be reduced.

[0048]

The present invention has the following effects.

(1) In the compound gear pump according to the first aspect, foreign matter such as dust contained in oil sucked into the suction passage of the internal gear pump and entering between the external teeth of the outer rotor. Are the outer teeth of the outer rotor and the second
When the external teeth of the rotor engage with each other, the rotor is pushed out from between the external teeth toward the suction passage. Accordingly, the foreign matter is caught between the outer rotor and the inner wall of the concave portion of the casing which rotatably accommodates the rotor, thereby promoting the wear thereof and preventing the seizure between them. .

(2) In the hydraulic circuit of an engine using the compound gear pump according to the second aspect, foreign matter such as dust that has entered between the external teeth of the outer rotor of the internal gear pump is removed from the external teeth of the outer rotor. When the external teeth of the second rotor mesh with each other, the external teeth are pushed out from between the external teeth to the suction passage side, so that the foreign matter passes between the outer rotor and the inner wall of the concave portion for accommodating the outer rotor of the casing, and It can be prevented from being sucked from the suction passage downstream of the oil filter of the type gear pump and supplied to the valve control device together with the oil. The foreign matter pushed out to the suction passage side by the second rotor is supplied to the main gallery side together with the oil, is captured and removed by an oil filter provided in the main gallery, and only the oil is transmitted to the valve control device. Supplied. Therefore, the malfunction of the valve control device can be prevented, and the reliability can be improved. Further, wear of each component of the valve control device can be prevented.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.

FIG. 2 is a plan view showing an embodiment of the compound gear pump according to the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a cross-sectional view showing a part of an embodiment of the valve timing control apparatus to which the present invention is applied.

FIG. 5 is a sectional view of a conventional compound gear pump.

FIG. 6 is a hydraulic circuit diagram using a conventional compound gear pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal gear pump 2 ... External gear pump 6 ... Suction passage of the 1st gear pump 22 ... Inner rotor of internal gear pump 24 ... Outer rotor of internal gear pump 26 ... External tooth of internal gear pump outer rotor 30 ... Separate first rotor 31 ... Separate first rotor outer teeth 51 ... Separate second rotor 52 ... Separate second rotor outer teeth

Claims (2)

[Claims] An external gear is provided on an outer periphery of an outer rotor of an internal gear pump having an inner rotor and an outer rotor, and the external gear is pumped by a separately provided first rotor having external teeth meshing with the external teeth. In the compound gear pump, the outer gear meshing with the outer teeth of the outer rotor of the inner gear pump is provided between the first rotor constituting the outer gear pump and the suction passage of the inner gear pump. A second rotor having teeth is provided separately, and one end side of a meshing portion between the external teeth of the second rotor and the external teeth of the outer rotor faces the suction passage of the internal gear pump. Features a compound gear pump. 2. An internal gear pump having an inner rotor having an inner rotor and an outer rotor driven by a crankshaft, external teeth are provided on an outer periphery of an outer rotor, and a separate first tooth having external teeth circumscribing the external teeth is provided. A compound gear pump configured to form an external gear pump by a rotor, wherein the internal gear pump supplies oil from an oil pan sucked from a suction passage to a main gallery of an engine having an oil filter via a discharge passage. The external gear pump is a hydraulic circuit of an engine using a compound gear pump adapted to suck oil from a suction passage downstream of the oil filter in the main gallery and supply the oil to a valve control device. A front rotor is provided between the first rotor constituting the gear pump and the suction passage of the internal gear pump. A separate second rotor having external teeth circumscribing the external teeth of the outer rotor of the internal gear pump is provided, and one end of a meshing portion between the external teeth of the second rotor and the external teeth of the outer rotor is provided. A hydraulic circuit for an engine using a compound gear pump, wherein the hydraulic circuit faces a suction passage of the internal gear pump.