JP6513555B2 - Hydraulic circuit of swash plate type variable displacement pump - Google Patents

Description

  The present invention relates to a hydraulic circuit of a swash plate type variable displacement pump used in a hydraulic machine.

  Conventionally, a swash plate type variable displacement pump which is driven by an engine and whose discharge flow rate is adjusted according to the amount of tilt of a swash plate is known as a hydraulic pump used for a hydraulic machine such as a hydraulic shovel. In the swash plate type variable displacement pump, the pump discharge flow rate is controlled in accordance with the pump discharge pressure so that the horsepower (pump output) becomes constant. For example, when a load acts on the actual machine actuator and the pump discharge pressure is increased, the pump discharge flow rate is reduced when the set horsepower is about to be exceeded, and is maintained at substantially equal horsepower.

  According to Patent Document 1, when another device such as an air conditioner driven by the output of the engine operates, the horsepower of the swash plate type variable displacement pump can be secured so that the horsepower of the engine for driving the other device can be secured. Discloses a horsepower control regulator that lowers

JP 2008-280942 A

  By the way, Patent Document 1 is described as a swash plate type variable displacement pump which can lower the horsepower (mode control: hereinafter also referred to as "power reduction function") when other accessories such as an air conditioner operate. Some are equipped with means other than a conventional horsepower control regulator. FIG. 4 shows the fluid pressure supplied according to the on / off state of the gear pump oil pressure Pg1 and the accessory besides the first piston 361 and the second piston 363 which receive the discharge pressures P1 and P2 of the swash plate type variable displacement pump respectively. (Signal pressure) A hydraulic circuit of a swash plate type variable displacement pump provided with a stepped third piston 365 that receives pressure Pi.

  In such a hydraulic circuit, the gear pump hydraulic pressure Pg1 is introduced into the pressure chamber 357 around the end of the small diameter portion of the third piston 365, and the signal pressure Pi supplied according to the on / off state of the accessory is introduced. It is introduced into the pressure chamber 359 around the stepped portion of the third piston 365 via the port Z. The third piston 365 receives the gear pump hydraulic pressure Pg1 at the end face of the small diameter portion, receives the signal pressure Pi at the stepped surface, and assists the control of the amount of tilt of the swash plate according to the received pressure. Reduce

  FIG. 15 shows an example of the horsepower characteristic of the swash plate type variable displacement pump. The solid line shows the flow-pressure characteristic when the gear pump hydraulic pressure Pg1 is low and the signal pressure Pi is zero. When the gear pump oil pressure Pg1 is low, when the accessory is turned on, the swash plate is tilted at a pump discharge pressure lower than that in the case where the signal pressure Pi is zero due to the auxiliary force obtained by receiving the signal pressure Pi. As the pump discharge flow rate starts to decrease, the horsepower decreases (dotted line). Further, the dashed-dotted line indicates the flow-pressure characteristic when the gear pump hydraulic pressure Pg1 is high and the signal pressure Pi is zero. When the gear pump hydraulic pressure Pg1 is high, when the accessory is turned on, the swash plate is tilted at a pump discharge pressure lower than that when the signal pressure Pi is zero by the auxiliary force obtained by receiving the signal pressure Pi. Because the pump discharge flow rate starts to decrease, the horsepower decreases (two-dot chain line).

  However, while the signal pressure Pi supplied according to the on / off state of the accessory is a relatively low pressure, the pressure receiving area of the signal pressure Pi at the third piston 365 is relatively small. Therefore, it is difficult to increase the amount of horsepower reduction. In particular, the signal pressure Pi is based on the discharge pressure Pg2 of the gear pump (second gear pump 118) connected to the drive shaft of the swash plate type variable displacement pump, and it is not easy to make the pressure high. Further, in the swash plate type variable displacement pump having the circuit configuration shown in FIG. 4, the space for incorporating a new component such as a horsepower control regulator as described in Patent Document 1 is limited, and a drastic change is required. It will

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to increase the pressure receiving area of the hydraulic pressure supplied according to the on / off state of the accessory, and to operate the accessory It is an object of the present invention to provide a swash plate type variable displacement pump capable of increasing the amount of horsepower reduction of a swash plate type variable displacement pump at the time.

  In order to solve the above-mentioned problems, according to one aspect of the present invention, a swash plate type first pump portion, which discharges hydraulic oil to a first discharge oil passage, which is driven by a drive source, a second discharge, respectively. A second swash plate type pump portion that discharges hydraulic fluid to an oil passage, a third pump portion that discharges hydraulic fluid to a third discharge oil passage, a first pump portion, a second pump portion, and A tilt amount control unit that changes the tilt amount of the swash plate based on the discharge pressure of the third pump unit and the signal pressure supplied according to the operation state of the accessory, and a branch from the first discharge oil passage A first control oil passage provided with a first orifice, a second control oil passage branched from a second discharge oil passage and provided with a second orifice, a first control oil passage and a first control oil passage The two control oil paths merge and are connected, and the discharge pressure of the first pump portion and the second port are connected to the first pressure receiving surface of the displacement amount control portion. And a third control oil passage for introducing a first control hydraulic pressure based on the discharge pressure of the pump portion, and a third pressure receiving surface branched from the third discharge oil passage A fourth control oil path for supplying a second control oil pressure based on the discharge pressure of the pump unit, and a fifth control oil path for supplying a third control oil pressure based on a signal pressure to the third pressure receiving surface of the displacement amount control unit A hydraulic circuit of a swash plate type variable displacement pump is provided, comprising: a control oil passage of the second control oil passage; and a third orifice provided in the third control oil passage.

  The tilting amount control unit has a first piston capable of pressing the swash plate at one end and a first piston, a second piston, and a second pressure receiving surface which is the first pressure receiving surface, the second pressure receiving surface, or the third pressure receiving surface. A third piston may be provided.

  The displacement amount control unit includes an oil passage member in communication with an oil passage formed in the cover and having an axial oil passage that constitutes a part of a third control oil passage, and the third orifice is It may be provided in a radial oil passage that communicates the side surface of the oil passage member with the axial oil passage.

  The signal pressure may be a pressure generated using the discharge pressure of the fourth pump unit driven by the drive source.

  As described above, according to the present invention, the pressure receiving area of the hydraulic pressure supplied is increased according to the operating state of the accessory, and the amount of decrease in horsepower of the swash plate type variable displacement pump during operation of the accessory is increased. be able to.

It is a sectional view showing an example of composition of a swash plate type variable displacement pump concerning an embodiment of the invention. It is an explanatory view showing a hydraulic circuit of a swash plate type variable displacement pump concerning the embodiment. It is sectional drawing which shows the structural example of the amount control part of inclinations which concerns on the embodiment. FIG. 7 is an explanatory view showing a hydraulic circuit of a (conventional) swash plate type variable displacement pump according to Comparative Example 1; FIG. 6 is an explanatory view showing the characteristics of the swash plate type variable displacement pump according to the first embodiment. FIG. 6 is an explanatory view showing the characteristics of a swash plate type variable displacement pump according to Comparative Example 1; FIG. 8 is an explanatory view showing a hydraulic circuit of a swash plate type variable displacement pump according to Comparative Example 2; FIG. 8 is an explanatory view showing the characteristics of a swash plate type variable displacement pump according to Comparative Example 2; FIG. 10 is an explanatory view showing a hydraulic circuit of a swash plate type variable displacement pump according to Comparative Example 3; FIG. 10 is an explanatory view showing the characteristics of a swash plate type variable displacement pump according to Comparative Example 3; FIG. 10 is an explanatory view showing a hydraulic circuit of a swash plate type variable displacement pump according to Comparative Example 4; FIG. 16 is an explanatory view showing the characteristics of a swash plate type variable displacement pump according to Comparative Example 4; FIG. 16 is an explanatory view showing a hydraulic circuit of a swash plate type variable displacement pump according to Comparative Example 5; FIG. 16 is an explanatory view showing the characteristics of a swash plate type variable displacement pump according to Comparative Example 5; FIG. 6 is an explanatory view showing a power reduction function of the swash plate type variable displacement pump.

  The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

<1. Overall Configuration Example of Swash Plate Type Variable Displacement Pump>
First, a configuration example of a swash plate type variable displacement pump to which a hydraulic circuit according to an embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 shows a cross-sectional view of a swash plate type variable displacement pump 100. The swash plate type variable displacement pump 100 is mounted and used on hydraulic equipment such as a hydraulic shovel operated by, for example, a plurality of hydraulic actuators. The swash plate type variable displacement pump 100 is a piston pump capable of adjusting a pump discharge flow rate by controlling an amount of tilt which is an inclination of the swash plate 30.

  In the swash plate type variable displacement pump 100, the configuration other than the oil passage configuration and the displacement amount control unit 50 can be configured in the same manner as the conventionally known swash plate type variable displacement pump. Hereinafter, the entire configuration of the swash plate type variable displacement pump 100 other than the oil passage configuration and the displacement amount control unit 50 will be briefly described.

  The swash plate type variable displacement pump 100 includes a pump housing 5 and a cover 10. A drive shaft 8 rotationally driven by an engine (not shown) is inserted into the pump housing 5 and the cover 10. The swash plate type variable displacement pump 100 according to the present embodiment is a dual pump having two discharge ports not shown. Further, a first gear pump and a second gear pump (not shown) are connected to the drive shaft 8. The first gear pump pumps a predetermined hydraulic pressure (hereinafter also referred to as “first gear pump hydraulic pressure”) by rotation of the drive shaft 8. In addition, the second gear pump pressure-feeds a low-pressure hydraulic pressure (hereinafter also referred to as “second gear pump hydraulic pressure”) by the rotation of the drive shaft 8. The second gear pump hydraulic pressure is supplied to the other end face of the third piston (not shown) of the tilting amount control unit 50 in order to reduce the horsepower of the swash plate type variable displacement pump 100 at the time of operation of auxiliary equipment such as an air conditioner. It becomes the source pressure of the signal pressure.

  The swash plate 30 and the cylinder block 40 are accommodated in an internal space formed by the pump housing 5 and the cover 10. The cylinder block 40 is connected to the drive shaft 8 and rotationally driven by the rotation of the drive shaft 8. The cylinder block 40 includes a plurality of cylinders 41 along the axial direction of the drive shaft 8. Each cylinder 41 holds a pressure piston 45 so as to be capable of reciprocating in the axial direction.

  One end side of each pressing piston 45 is in contact with the swash plate 30. While the cylinder block 40 makes one rotation due to the rotation of the drive shaft 8, the pressurizing piston 45 reciprocates in the cylinder 41, and suction and discharge of hydraulic oil are performed. The stroke amount of the pressure piston 45 during one rotation of the cylinder block 40 is variable by the inclination (tilt amount) of the swash plate 30 with respect to the plane orthogonal to the direction of the reciprocation of the pressure piston 45. That is, the pump discharge flow rate is variable according to the amount of displacement of the swash plate 30.

  The swash plate 30 is biased by a coil spring 35 at the upper side in the figure. The coil spring 35 is sandwiched by the cover 10 and the swash plate 30. On the other hand, the swash plate 30 is in contact with one end surface of the piston (first piston 61) of the tilting amount control unit 50 at the lower side in the drawing. The first piston 61 is slidably supported in the axial direction of the drive shaft 8 by a guide sleeve 51 fixed to the cover 10. Although only the first piston 61 is shown in FIG. 1, in practice the second and third pistons are also arranged in parallel, and one end face of each piston is in contact with the swash plate 30. .

  The other end surface of the first piston 61 of the tilt amount control unit 50 is a pressure receiving surface of the first control oil pressure Pc, and the other end surface of the second piston is a second control oil pressure (first gear pump oil pressure The pressure receiving surface of Pg1 is provided, and the other end surface of the third piston is a pressure receiving surface of a third control hydraulic pressure (signal pressure) Pi. Therefore, the lower side of the swash plate 30 is pressed by the first control oil pressure Pc, the second control oil pressure Pg1 and the third control oil pressure Pi loaded via the respective pistons.

  When the control oil pressure is small, the swash plate 30 is biased by the coil spring 35, and the amount of tilt is maximized. From this state, as the control hydraulic pressure increases, the lower side of the swash plate 30 is pressed against the biasing force of the coil spring 35, and the amount of tilting decreases. In the swash plate type variable displacement pump 100, as the pump discharge pressure increases, the first control oil pressure Pc increases and the pump discharge flow rate decreases. Further, the swash plate type variable displacement pump 100 assists the control of the amount of tilt of the swash plate 30 according to the discharge pressure Pg1 of the first gear pump (not shown), and to the signal pressure Pi supplied according to the on / off state of the accessory. Accordingly, the control of the amount of tilt of the swash plate 30 is assisted.

  In the swash plate type variable displacement pump 100 according to the present embodiment, the control hydraulic pressure is guided to the other end surface of each piston of the tilting amount control unit 50 via an oil passage configuration (not shown).

<2. Configuration example of hydraulic circuit>
Next, a configuration example of the hydraulic circuit 110 of the swash plate type variable displacement pump 100 according to the present embodiment will be described. FIG. 2 is a circuit diagram of the hydraulic circuit 110 according to the present embodiment. The hydraulic circuit 110 includes a first pump unit 112, a second pump unit 114, a third pump unit 116, and a fourth pump unit 118. Among them, the first pump unit 112 and the second pump unit 114 correspond to the pump units which are discharged from the two discharge ports A1 and A2 by the suction and pressure feeding operation of the pressure piston 45 of the swash plate type variable displacement pump 100. . The third pump portion 116 and the fourth pump portion 118 correspond to the above-described first gear pump and second gear pump, respectively.

  The first pump unit 112 supplies the hydraulic pressure P1 to the actuator or the like of the hydraulic device from the first discharge port A1 via the first discharge oil passage 122. The second pump unit 114 supplies the hydraulic pressure P2 from the second discharge port A2 to the actuator or the like of the hydraulic device via the second discharge oil passage 124. The third pump unit 116 supplies the first gear pump hydraulic pressure Pg1 from the third discharge port A3 via the third discharge oil passage 126. The fourth pump unit 118 supplies the second gear pump hydraulic pressure Pg2 from the fourth discharge port A4 via the fourth discharge oil passage 128.

  The first control oil passage 132 is branched and connected to the first discharge oil passage 122. Further, a second control oil passage 134 is branched and connected to the second discharge oil passage 124. The first control oil passage 132 and the second control oil passage 134 merge and are connected to the third control oil passage 135. The third control oil passage 135 introduces a first control oil pressure Pc, which is an average pressure of the discharge pressures P1 and P2, into the pressure chamber 53 of the first piston 61 of the displacement amount control unit 50. The first control oil passage 132 is provided with a first orifice 142, and the second control oil passage 134 is provided with a second orifice 144. The diameters of the first orifice 142 and the second orifice 144 are the same, so that the first control hydraulic pressure Pc introduced into the pressure chamber 53 of the first piston 61 is the average pressure of the discharge pressures P1, P2. It is assumed.

  A fourth control oil passage 136 is branched and connected to the third discharge oil passage 126. The fourth control oil passage 136 introduces a first gear pump hydraulic pressure (hereinafter also referred to as "second control hydraulic pressure") Pg1 into the pressure chamber 55 of the second piston 63 of the displacement amount control unit 50. . Further, a signal based on the second gear pump hydraulic pressure Pg2 which is the discharge pressure of the fourth pump unit 118 to the pressure chamber 57 of the third piston 65 of the displacement amount control unit 50 via the signal pressure introduction port Z A pressure (hereinafter also referred to as “third control hydraulic pressure”) Pi is introduced. The third control hydraulic pressure Pi is controlled to an appropriate value by a signal pressure control unit (not shown) according to the on / off state or the output of an auxiliary device such as an air conditioner.

  In the displacement amount control unit 50, the first piston 61, the second control oil pressure Pc, the second control oil pressure Pg1 and the third control oil pressure Pi introduced into the pressure chambers 53, 55, 57 respectively, the first piston 61, the second The swash plate 30 is pressed via the piston 63 and the third piston 65 of the above. Thereby, the amount of tilt of the swash plate 30 is controlled. As a result, the discharge flow rate of the first pump unit 112 and the second pump unit 114 changes, and the horsepower is controlled.

  The third control oil pressure Pi is set to an appropriate pressure in accordance with the on / off state of an auxiliary device such as an air conditioner. In the ON state of the auxiliary machine, since the horsepower for driving the auxiliary machine is required, the third control hydraulic pressure Pi having a larger value than the OFF state is introduced into the pressure chamber 57, The amount of tilt of the swash plate 30 is smaller. For example, when the operation switch of the air conditioner is turned on, the signal pressure control unit (not shown) may switch the signal pressure Pi to increase.

  Here, in the hydraulic circuit 110 according to the present embodiment, the first control hydraulic pressure Pc, which is the average pressure of the discharge pressures P1 and P2 of the first pump portion 112 and the second pump portion 114 A third orifice 145 is provided in the third control oil passage 135 leading to the pressure chamber 53. The third orifice 145 has a function of suppressing the transmission of the vibration of the swash plate 30 generated by the drive of the swash plate type variable displacement pump 100 to the third control oil passage 135 and the pressure from the third orifice 145 It has a function of suppressing the vibration of the swash plate 30 according to the volume of the third control oil passage 135 up to the chamber 53 and the volume of the pressure chamber 53.

  As the pressure pulsation in the pressure chamber 53 and the third control oil passage 135 increases, the vibration of the swash plate 30 also increases, and the pump discharge flow rate by the first pump portion 112 and the second pump portion 114 is not sufficient. Become stable. As a result, it becomes difficult to control the swash plate type variable displacement pump 100 with equal horsepower. The third orifice 145 suppresses the pressure pulsation to enable equal horsepower control.

  At this time, the third orifice 145 is preferably provided at a position where pressure pulsation can be suppressed, that is, a position where the fluctuation range of the pump discharge flow rate is smaller. That is, since the suppression effect of the pressure pulsation due to the provision of the third orifice 145 may differ depending on factors such as the position of the pressure pulsation node or the belly, the appropriate position is selected and the third orifice 145 is selected. It is preferable to provide.

<3. Tilt amount control unit>
FIG. 3 is a partial cross-sectional view showing a configuration example of the tilting amount control unit 50. As shown in FIG. The tilt amount control unit 50 includes a guide sleeve 51 fixed to the cover 10 by a bolt 81. The guide sleeve 51 has a first guide portion 51a, a second guide portion 51b, and a third guide portion 51c. The first piston 61 is slidably held by the first guide portion 51a. The second piston 63 is slidably held by the second guide portion 51b. The third piston 65 is slidably held by the third guide portion 51c.

  The first guide portion 51 a is open at the end opposite to the cover 10, and the other end faces the holding hole 12 of the oil passage member 70 formed in the cover 10. An oil passage member 70 having an axial hole (axial oil passage) 71 forming a part of the third control oil passage 135 and a third orifice 145 is inserted in the holding hole 12. The third orifice 145 is provided on an oil path extending in a radial direction perpendicular to the axial hole 71. An annular groove 73 is provided on the outer peripheral surface of the oil passage member 70 at a position where the third orifice 145 is formed, and a third control oil passage 135 (not shown) formed in the cover 10 is provided in the annular groove 73. It is in communication.

  The first control oil pressure Pc supplied via the third control oil passage 135 flows through the axial hole (axial oil passage) 71 via the third orifice 145, and into the first guide portion 51a. be introduced. The first piston 61 receives the first control oil pressure Pc introduced into the first guide portion 51 a and moves in the first guide portion 51 a. That is, in the displacement amount control unit 50 of the swash plate type variable displacement pump 100 according to the present embodiment, the discharge pressures P1 and P2 of the first pump unit 112 and the second pump unit 114 are one first piston 61. The pressure is received and used to control the swash plate 30.

  Since the third orifice 145 is formed in the oil passage member 70, the distance from the third orifice 145 to the first piston 61 is shortened. Therefore, pressure pulsations generated in the third control oil passage 135 are suppressed, and the pump discharge flow rate can be stabilized more.

  The second guide portion 51 b is open at the end opposite to the cover 10, and the other end communicates with the oil passage 83 communicating with the fourth control oil passage 136 formed in the cover 10. The second piston 63 is inserted into the second guide portion 51b, receives the second control oil pressure Pg1 introduced from the fourth control oil passage 136, and moves in the second guide portion 51b.

  The third guide portion 51 c is open at the end opposite to the cover 10, and the other end communicates with the oil passage 85 communicating with the fifth control oil passage 138 formed in the cover 10. The third piston 65 is inserted into the third guide portion 51c, receives the third control oil pressure Pi introduced from the fifth control oil passage 138, and moves in the third guide portion 51c. That is, in the swash plate type variable displacement pump 100 according to the present embodiment, the discharge pressures P1 and P2 of the first pump portion 112 and the second pump portion 114 are received by one first piston 61. Accordingly, the signal pressure (third control hydraulic pressure) Pi can be independently received by the third piston 65. Therefore, the pressure receiving area of the signal pressure Pi can be increased.

  Also in the case of the conventional hydraulic circuit shown in FIG. 4, the displacement amount control unit 350 is provided with three pistons that receive the control hydraulic pressure introduced to control the swash plate 30. In the conventional hydraulic circuit, three pistons respectively receive the discharge pressure P1 of the first pump portion 112, the discharge pressure P2 of the second pump portion 114, or the first gear pump hydraulic pressure Pg1 and the signal pressure Pi. It was

  On the other hand, in the hydraulic circuit according to the present embodiment, the first piston 61 receives the average pressure Pc of the discharge pressures P1, P2 of the first pump portion 112 and the second pump portion 114. Therefore, it is possible to independently receive the first gear pump hydraulic pressure Pg1 and the signal pressure Pi by the second piston 63 and the third piston 65, respectively. Therefore, the pressure receiving area of the signal pressure Pi can be increased without significantly changing the overall size of the displacement amount control unit 50. As a result, it is possible to increase the amount of reduction in horsepower at the time of operation of the accessory without largely changing the design of the swash plate type variable displacement pump 100 having the hydraulic circuit configuration shown in FIG.

<4. Summary>
As described above, the hydraulic circuit 110 of the swash plate type variable displacement pump 100 according to the present embodiment has the discharge pressures P1 and P2 of the first pump portion 112 and the second pump portion 114 as one first piston 61 The third piston 65 can independently receive the signal pressure Pi supplied according to the operating state of the accessory while the pressure is received by the third piston 65. Therefore, even if the signal pressure Pi is relatively low, the signal pressure Pi can be received by the large pressure receiving surface to assist the displacement amount control. Thereby, the amount of horsepower reduction at the time of operation of the accessory can be increased.

  Further, the hydraulic circuit 110 of the swash plate type variable displacement pump 100 according to the present embodiment uses the average pressure Pc of the discharge pressures P1 and P2 of the first pump unit 112 and the second pump unit 114 as the displacement amount control unit 50. A third orifice 145 is provided in the third control oil passage 135 leading. Therefore, pressure pulsations in the pressure chamber 53 and the third control oil passage 135, which are caused by the vibration of the swash plate 30, are suppressed, and variations in the pump discharge flow rate are reduced. This makes it possible to execute equal horsepower control with less variation.

  Hereinafter, examples of the present invention will be described. In the following examples, differences in horsepower characteristics due to differences in hydraulic circuit configuration and orifice positions were evaluated. In the following embodiment, the difference in horsepower characteristics is evaluated using a motor instead of the engine, and the motor rotational speed is substituted for the engine rotational speed.

(Example)
As an example, the horsepower characteristic was evaluated using the hydraulic circuit 110 shown in FIG. In the hydraulic circuit 110, the tilting amount control unit 50 used the one shown in FIG. The hydraulic oil used is VG46, and the discharge pressure P1, P2 of the first pump part 112 and the second pump part 114 is 25MPa when the motor rotational speed (engine rotational speed) N is 2200 rpm, and the third pump part The discharge pressure (first gear pump hydraulic pressure) Pg1 of 116 was set to 1.5 MPa, and the signal pressure Pi based on the discharge pressure of the fourth pump portion 118 was set to 3.2 MPa. Thereafter, the pump discharge flow rate Q1, Q2 (L / min), pressure P1, P2, Pg1, Pi (MPa) when the motor rotational speed (engine rotational speed) N is reduced from 2200 rpm to 900 rpm and then returned to 2200 rpm again The fluctuation of the torque T (N · m) was observed.

  The obtained result is shown in FIG. The horizontal axis in FIG. 5 indicates the motor rotational speed (engine rotational speed) N (rpm). According to the hydraulic circuit 110 of the embodiment, the pump discharge flow rates Q1 and Q2 increase proportionally with the increase of the motor rotation number (engine rotation number) N, and the torque T changes without largely fluctuating.

(Comparative example 1)
As Comparative Example 1, using the hydraulic circuit shown in FIG. 4 described above, the horsepower characteristics were evaluated by the same method as in the example. In the first comparative example, the first orifice 342 is provided upstream of the pressure chamber 353 of the first piston 361 (the same position as the third orifice 145 in FIG. 3), and the second orifice 344 is the second. It is provided immediately before the pressure chamber 355 of the piston 363 (the position of the oil passage 83 in FIG. 3). The obtained result is shown in FIG. According to the hydraulic circuit of Comparative Example 1, the pump discharge flow rates Q1, Q2 increase proportionally with the increase of the motor rotation number (engine rotation number) N, and can be controlled with the substantially constant torque T. However, since the hydraulic circuit of Comparative Example 1 is configured to receive the signal pressure Pi on the stepped surface of the third piston 365, there is a limit to the amount of horsepower reduction at the time of operation of the accessory.

(Comparative example 2)
As Comparative Example 2, using the hydraulic circuit shown in FIG. 7, the horsepower characteristics were evaluated by the same method as in the example. In the hydraulic circuit shown in FIG. 7, the first orifice 342 and the second orifice 344 provided in the first control oil passage 332 and the second control oil passage 334 in the hydraulic circuit shown in FIG. 4 are omitted. It is. The obtained result is shown in FIG. According to the hydraulic circuit of Comparative Example 2, the pump discharge flow rates Q1 and Q2 largely vary with the change of the motor rotation number (engine rotation number) N, and the torque T also largely fluctuates. Further, since the hydraulic circuit of Comparative Example 2 is configured to receive the signal pressure Pi on the stepped surface of the third piston 365, there is a limit to the amount of horsepower reduction at the time of operation of the accessory.

(Comparative example 3)
As Comparative Example 3, using the hydraulic circuit shown in FIG. 9, the horsepower characteristics were evaluated by the same method as in the example. The hydraulic circuit shown in FIG. 9 is one in which the second orifice 344 provided in the second control oil passage 334 in the hydraulic circuit shown in FIG. 4 is omitted. The obtained result is shown in FIG. According to the hydraulic circuit of Comparative Example 3, the pump discharge flow rates Q1 and Q2 increase proportionally with the increase of the motor rotation number (engine rotation number) N, and can be controlled with a substantially constant torque T. However, since the hydraulic circuit of Comparative Example 3 is configured to receive the signal pressure Pi on the stepped surface of the third piston 365, there is a limit to the amount of horsepower reduction at the time of operation of the accessory.

(Comparative example 4)
As Comparative Example 4, using the hydraulic circuit shown in FIG. 11, the horsepower characteristics were evaluated in the same manner as in the example. The hydraulic circuit shown in FIG. 11 is obtained by omitting the first orifice 342 provided in the first control oil passage 332 in the hydraulic circuit shown in FIG. The obtained result is shown in FIG. According to the hydraulic circuit of Comparative Example 4, the variation between the pump discharge flow rates Q1, Q2 becomes large, and the torque T also fluctuates significantly. The difference from the hydraulic circuit of Comparative Example 3 is considered to be due to the difference in the positions of the first orifice 342 and the second orifice 344. In addition, since the hydraulic circuit of Comparative Example 4 is configured to receive the signal pressure Pi on the stepped surface of the third piston 365, there is a limit to the amount of horsepower reduction at the time of operation of the accessory.

(Comparative example 5)
As Comparative Example 5, using the hydraulic circuit shown in FIG. 13, the horsepower characteristics were evaluated by the same method as in the example. The hydraulic circuit shown in FIG. 13 is obtained by omitting the third orifice 145 provided in the third control oil passage 135 in the hydraulic circuit shown in FIG. The obtained result is shown in FIG. According to the hydraulic circuit of Comparative Example 5, the variation between the pump discharge flow rates Q1 and Q2 becomes large, and the torque T also largely fluctuates.

(Comparison of Example and Comparative Example)
Table 1 shows the evaluation results of the horsepower characteristics according to the example and the comparative examples 1 to 5. In Table 1, the horsepower characteristic result shows the ratio when the fluctuation range of the torque T in the example is 1.

  As shown in Table 1, in the embodiment and the comparative example 5 in which the average pressure Pc of the discharge pressures P1, P2 of the first pump portion 112 and the second pump portion 114 is received by the first piston 61, It was found that equal horsepower control can not be maintained when the third control oil passage 135 is not provided with the third orifice 145 (Comparative Example 5). Therefore, to increase the average pressure Pc of the discharge pressures P1 and P2 of the first pump portion 112 and the second pump portion 114 with one first piston 61 in order to increase the power reduction function, It can be appreciated that a third orifice 145 may be provided in the control oil passage 135 of the second embodiment.

  Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 pump housing 30 swash plate 40 cylinder block 41 cylinder 45 pressurization piston 50 tilting amount control part 51 guide sleeve 53, 55, 55 pressure chamber 61 1st piston 63 2nd piston 65 3rd piston 70 oil-path member 71 Axial hole (axial oil passage)
100 swash plate type variable displacement pump 110 hydraulic circuit 112 first pump portion 114 second pump portion 116 third pump portion 118 fourth pump portion 132 first control oil passage 134 second control oil passage 135 third Control oil passage 136 Fourth control oil passage 138 Fifth control oil passage 142 First orifice 144 Second orifice 145 Third orifice

Claims (4)

A swash plate type first pump unit for discharging hydraulic fluid to a first discharge oil passage, driven by a drive source, and a swash plate type second pump unit for discharging hydraulic fluid to a second discharge oil channel, And a third pump unit that discharges hydraulic oil to a third discharge oil passage,
The displacement amount of the swash plate is changed based on the discharge pressure of the first pump unit, the second pump unit and the third pump unit, and the signal pressure supplied according to the operating state of the accessory. Tilt amount control unit,
A first control oil passage branched from the first discharge oil passage and provided with a first orifice;
A second control oil passage branched from the second discharge oil passage and provided with a second orifice;
The first control oil passage and the second control oil passage are joined together and connected, and the discharge pressure of the first pump unit and the second pressure unit are connected to a first pressure receiving surface of the displacement amount control unit. A third control oil passage for introducing a first control hydraulic pressure based on the discharge pressure of the pump unit;
Fourth control oil that branches from the third discharge oil passage and supplies a second control hydraulic pressure based on the discharge pressure of the third pump portion to the second pressure receiving surface of the displacement amount control unit Road,
A fifth control oil passage for supplying a third control hydraulic pressure based on the signal pressure to a third pressure receiving surface of the displacement amount control unit;
A third orifice provided in the third control oil passage;
The hydraulic circuit of a swash plate type variable displacement pump, comprising:   The tilting amount control unit has a first piston whose one end is capable of pressing the swash plate and whose other end is the first pressure receiving surface, the second pressure receiving surface, or the third pressure receiving surface, The hydraulic circuit of a swash plate type variable displacement pump according to claim 1, comprising a second piston and a third piston.   The tilt amount control unit includes an oil passage member in communication with an oil passage formed in a cover and having an axial oil passage that constitutes a part of the third control oil passage, The hydraulic circuit of a swash plate type variable displacement pump according to claim 1 or 2, wherein the orifice is provided in a radial oil passage communicating the side surface of the oil passage member with the axial oil passage. The hydraulic pressure of a swash plate type variable displacement pump according to any one of claims 1 to 3, wherein the signal pressure is a pressure generated using a discharge pressure of a fourth pump unit driven by the drive source. circuit.

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