JP2001116106A - Tandem pump unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem pump unit allowing simplification of the operation of mounting it in a vehicle and a reduction in cost through a reduction in number of part items. SOLUTION: The tandem pump unit includes a common housing 20 accommodating first and second hydraulic pumps 10a, 10b, and first and second center sections 30a, 30b supporting the respective hydraulic pumps, the common housing having first and second openings 20a, 20b formed at both axial ends of a pump shaft for enabling the first and second hydraulic pumps to be inserted therein, and a bearing wall 20c formed in a portion intermediate between the first and second openings. The first and second center sections are connected to the common housing in such a way as to close the first and second openings while supporting the first and second pumps. The connections of the pump shafts of the first and second hydraulic pumps are supported by the bearing wall of the common housing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump unit for use in a vehicle in which first and second hydraulic motors are respectively connected to left and right drive wheels, wherein the first and second hydraulic motors are respectively connected to the first and second hydraulic motors. The present invention relates to a pump unit including first and second hydraulic motors connected via a pair of first hydraulic lines and a pair of second hydraulic lines.

[0002]

2. Description of the Related Art In a vehicle in which first and second hydraulic motors are respectively connected to left and right drive wheels, the first
And first and second hydraulic pumps respectively connected to the first and second hydraulic motors via a pair of first hydraulic lines and a pair of second hydraulic lines, and suction / discharge oil of the first and second hydraulic pumps. By manipulating the amount, the output of the first and second hydraulic motors is changed so that the rotation speed and the rotation direction of the left and right drive wheels can be controlled. It is publicly known as described in Japanese Patent No. 4920733.

[0003] However, in the vehicle described in the above-mentioned US Patent Publication, a first hydraulic pump cooperating with the first hydraulic motor and a second hydraulic pump cooperating with the second hydraulic motor are separated. Therefore, there are various inconveniences, such as the work of attaching the first and second hydraulic pumps to the vehicle and the work of piping, and the necessity of a housing for each hydraulic pump.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above prior art, and is used for a vehicle in which first and second hydraulic motors are respectively connected to left and right drive wheels. A tandem pump unit in which first and second hydraulic pumps connected to each of the first and second hydraulic motors by a pair of first hydraulic lines and a pair of second hydraulic lines are connected in series; An object of the present invention is to provide a tandem pump unit that can reduce the cost by simplifying the mounting operation and reducing the number of parts.

[0005]

According to the present invention, there is provided a tandem pump unit for use in a vehicle in which first and second hydraulic motors are connected to left and right drive wheels, respectively. A first and a second hydraulic pump connected to each of the first and second hydraulic motors via a pair of first hydraulic lines and a pair of second hydraulic lines, respectively, In a tandem pump unit in which respective pump shafts of a second hydraulic pump are coaxially connected in series with each other, a common housing for accommodating the first and second hydraulic pumps and each supporting the first and second hydraulic pumps are provided. And a first and a second center section, wherein the common housing can insert first and second hydraulic pumps respectively formed at both ends in the axial direction of the pump shaft. First and second openings, and a bearing wall formed at an intermediate portion between the first and second openings, wherein the first and second center sections support the first and second pumps, respectively. In this state, the first and second openings are connected to the common housing so as to close the first and second openings, and a connection portion of each pump shaft of the first and second hydraulic pumps is
A tandem pump unit is provided that is supported by a bearing wall of the common housing.

[0006] Preferably, the first and second hydraulic pumps have a connection joint which is externally non-rotatably connected to a connection portion between the pump shafts of the first and second hydraulic pumps.

[0007] The coupling joint may be rotatably supported by a bearing hole formed in the bearing wall via a bearing member.

When the first and second pumps are variable displacement axial piston pumps having a cradle-type movable swash plate, the bearing wall has a surface facing the first and second hydraulic pumps. A guide surface for slidably guiding the convex arc surface on the back side of the movable swash plate can be formed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the pump unit according to the present invention will be described below with reference to FIGS. FIG. 1 is a hydraulic circuit diagram of a vehicle to which the pump unit 1 according to the present embodiment is applied, and FIG. 2 is a vertical side view of the vicinity of the pump unit 1. FIG. 3 is a sectional view taken along line AA in FIG.

As shown in FIGS. 1 to 3, the pump unit 1 is used for a vehicle in which first and second hydraulic motors 120a and 120b are connected to left and right drive wheels 130a and 130b, respectively. And a first hydraulic pump 10a and a second hydraulic pump 10b connected to the first and second hydraulic motors 120a and 120b by a first and second pair of hydraulic lines 140a and 140b, respectively. First hydraulic pump 10a and second hydraulic pump 10
b is a tandem pump unit in which pump shafts 11a and 11b are coaxially connected in series with each other.
A common housing 20 for accommodating the first and second hydraulic pumps 10a, 10b;
The first and second center sections 30a and 30b respectively support the first and second center sections 10b.

The left and right drive wheels 130a, 130b
That the first and second hydraulic motors 120a and 120b are connected to each other means that each hydraulic motor is directly connected to each drive wheel, and that each hydraulic motor is connected via an appropriate power transmission mechanism. A mode in which the driving wheels are operatively connected is also included.

In the present embodiment, the pump unit 1 is a vertical type in which the first and second pump shafts 11a and 11b are arranged to extend in the vertical direction.
ype), the present invention is not limited to such a form, and the horizontal type (horizontalty) in which the first and second pump shafts 11a and 11b are arranged to extend in the horizontal direction.
of course, it is also possible. In FIG. 1, reference numeral 100 denotes a drive source, reference numeral 110 denotes a cooling fan, and reference numeral 150 denotes an oil tank.

As shown in FIGS. 2 and 3, the common housing 20 includes first and second hydraulic pumps 10a, 10a formed at both axial ends of the pump shaft.
b and the first and second openings 20a, 20 respectively into which
b and a bearing wall 20c formed in an intermediate portion between the first and second openings 20a and 20b.

The first and second openings 20a and 20b are
The first center section 30a and the second
The center section 30b is liquid-tightly closed. Thus, the housing 20
Is provided between the bearing wall 20c and the first center section 20a.
And a second hydraulic pump receiving chamber defined by the bearing wall 20c and the second center section.
It can also be used as 0.

FIG. 4 is a sectional view taken along the line BB in FIG. As shown in FIGS. 2 to 4, the first hydraulic pump 10a and the second hydraulic pump 10b are variable displacement axial piston pumps, which are arranged coaxially with each other and are connected to each other so that they cannot rotate relative to the axis. First and second pump shafts 11a and 11b, and a first piston unit 12a that reciprocates with the rotation of the pump shafts.
And a second piston unit 12b, and a first cylinder block 13a for supporting the piston unit reciprocally.
And the second cylinder block 13b and the inclination angle,
A first movable swash plate 14a and a second movable swash plate 14b for regulating the stroke length of the piston unit and changing the suction / discharge oil amount of the piston unit, and a first control for operating the inclination angle of the movable swash plate It has a shaft 15a and a second control shaft 15b.

The first control shaft 15a and the second control shaft 15
b is connected to the center of the tilting of the first movable swash plate 14a and the second movable swash plate 14b each having an inner end protruding into the first housing 21 and the second housing 22 and configured as a trunnion type. The outer ends of the pump shafts 11a, 1
The first and second housings 21 and 22 extend outward from the first and second housings 21 and 22 so as to be separated from each other in the left-right direction orthogonal to 1b. By arranging the first control shaft 15a and the second control shaft 15b in this manner, when the pump unit 1 is installed on a vehicle having a push-pull type operation lever, the first control shaft 15a and the second control shaft The rotation axis of the shaft 15b can be arranged parallel to the rotation fulcrum of the operation lever, and
The structure of the link mechanism that connects the first control shaft 15a and the second control shaft 15b to the operation lever can be simplified.

FIG. 5 is a sectional view taken along line CC in FIG. As shown in FIGS. 2, 3 and 5, the first center section 30 a is configured such that the first hydraulic pump 10 a is supported on a surface facing the common housing 20 (the upper surface in the present embodiment). The common housing 2 is closed so as to close the first opening 20a of the common housing 20.
Connected to 0. The first hydraulic pump 10a
The pump shaft 11a has a front end in the transmission direction (a lower end in the present embodiment) extending further downward from the first center section 30a. Input is made via an appropriate power transmission mechanism such as a transmission device, and the cooling fan 110 can be driven (see FIG. 1 and the like).

On the other hand, the second center section 30b
Is a surface facing the common housing 20 as shown in FIGS. 2, 3 and 5 (the lower surface in the present embodiment).
The second hydraulic pump 10b is connected to the common housing 20 so as to close the second opening 20b of the common housing 20 while supporting the second hydraulic pump 10b. The second pump shaft 11b of the second hydraulic pump 10b has a rear end in the transmission direction (an upper end in the present embodiment) extending further upward from the second center section 30b. Can drive a charge pump 50 described later.

The rear end (upper end) of the first pump shaft 11a in the transmission direction and the front end (lower end) of the second pump shaft 11b in the transmission direction are connected to each other so as not to rotate relative to the axis. The part is the bearing wall 20 of the common housing 20
The bearing is supported by c. In the present embodiment, a coupling joint 16 is externally non-rotatably connected to the upper end of the first pump shaft 11a and the lower end of the second pump shaft 11b, and the coupling joint 16 is attached to the bearing wall 20c. The formed bearing hole 20d is supported via a bearing member 17, thereby connecting the upper end of the first pump shaft and the lower end of the second pump shaft to the bearing wall such that they cannot rotate relative to each other around the axis. In the present embodiment, two ball bearings are used as the bearing member 17 and the two ball bearings are juxtaposed. However, the coupling joint 16 can be supported by only one ball bearing. It is.

FIGS. 6 and 7 are sectional views taken along lines DD and EE in FIG. 3, respectively. As shown in FIGS. 1 and 7, the first center section 30a has an open end on one side (upper surface) in the axial direction of the pump so that one end thereof communicates with a suction / discharge port of the first piston unit 12a. A pair of first oil passages 31a for the first hydraulic pump whose ends are open outward on the other surface are formed. The other end openings of the pair of first oil passages 31a form a pair of first suction / discharge ports 32a serving as connection ports of a pair of first hydraulic lines 140a with the first hydraulic motor 120a. At four corners of the first center section 30a, mounting bosses are formed integrally so as to fix the first center section to a chassis of a vehicle (see FIG. 7).

On the other hand, as shown in FIGS. 1 and 6, one end of the second center section 30b is connected to the other surface (lower surface) in the pump axial direction so as to communicate with the suction / discharge port of the second piston unit 12b. A pair of second hydraulic passages 3 for the second hydraulic pump that are open and the other end is open outward on the other surface
1b is formed. The other end openings of the pair of second oil passages 31b form a pair of second suction / discharge ports 32b that serve as connection ports with the pair of second hydraulic lines 140b with the second hydraulic motor 120b. .

Further, one end of the second center section is opened to the upper surface of the second center section 30b to form a charging suction port 34, and the other end is connected to the pair of second oil passages 31b. Communicating with the second
The first branch branched to open into the hydraulic pump room storage space
A perforated portion 33a is formed. The charge suction port 34 communicates with a discharge port 51 of the charge pump 50 installed on the upper surface of the second center section 30b, and is configured to directly receive pressure oil from the charge pump 50. .

As shown in FIG. 5, one end of a pipe portion 33b is connected to the other end opening of the first perforated portion 33a. The pipe portion 33b penetrates through the second hydraulic pump accommodating chamber, the bearing wall 22c and the first hydraulic pump accommodating chamber, and is disposed in the pump unit such that the other end reaches the first center section 30a. I have. In addition, the second hydraulic pump accommodating chamber and the first
By forming an oil circulation hole 22f communicating with the hydraulic pump housing chamber and inserting the pipe portion 33b into the communication hole 22f, the pipe portion 33b can penetrate the bearing wall 22c (FIG. 4). And FIG. 5).

The first center section 30
In a, a second perforated portion 33c having one end connected to the other end of the pipe portion 33b and the other end communicating with each of the pair of first oil passages 31a is formed.

As described above, the first perforated portion 33a, the pipe portion 33b, and the second perforated portion 33c supply the oil supplied from an appropriate oil supply means (in this embodiment, the charge pump) with the pair of oils. The pair of first hydraulic lines 14 are provided via a first oil passage 31a and the pair of second oil passages 31b.
0a and a common charge line 33 for replenishing the pair of second hydraulic lines 140b (FIG. 1).
reference). In addition, it is also possible to form a perforated part in the housing and the center section instead of the pipe part 33b.

As described above, in the present embodiment,
The charge line 33 is formed in the pump unit 1, and the following effects can be obtained. That is, only by supplying oil from the oil supply means such as a charge pump to the charging suction port 34, the oil is supplied through the pair of first suction / discharge ports 32a and the pair of second suction / discharge ports 32b. 1st hydraulic line 1
Since oil can be supplied to the 40a and the pair of second hydraulic lines 140b, the piping structure for supplying oil can be simplified, thereby reducing the number of parts and improving assembly efficiency to reduce costs. be able to.

Further, since the charge line 33 is disposed in the pump unit 1, there is no danger that the charge line 33 will be in contact with an external member and be damaged, and there is a risk that oil will leak from the charge line 33 to the outside. Can be effectively prevented. The point that such leakage of oil can be prevented is, in particular, when used in a vehicle running on a lawn such as a lawnmower,
It is valid.

The discharge port 5 of the charge pump 50
1 communicates with the charge suction port 34 as described above, and further communicates with a pressure regulating line 53 in which a charge relief valve 52 is interposed (see FIGS. 1 and 5 and the like). ). Thereby, the charge relief valve 52
Thereby, the oil pressure of the charge line 33 can be set (see FIG. 1). The pressure regulating line 5
The downstream end of No. 3 communicates with the inside of the housing 20 also serving as the oil tank 150 via a drain port 35 formed in the second center section 30b (see FIGS. 1 and 5). Reference numeral 55 in FIG. 2 denotes a charge pump inlet. Reference numeral 56 denotes a suction port that communicates with the suction port, and is connected to the oil tank 150.

Further, as shown in FIGS. 1, 5 and 6, the rear end of the first perforated portion 33a constituting a part of the charge line 33 is respectively connected to each of the pair of first oil passages 31b. They are communicated via check valves 61c and 61d.
Similarly, a second part of the charge line 33
As shown in FIGS. 1, 5 and 7, the rear end of the perforated portion 33c is connected to each of the pair of first oil passages 31a via check valves 61a and 61b, respectively. The check valves 61a, 61b, 61c, and 61d supply pressure oil from the charge line 33 to the low-pressure sides of both the pair of first hydraulic lines 140a and the pair of second hydraulic lines 140b, and vice versa. This is to prevent oil from spilling.

A throttle valve is provided between at least one of the pair of first oil passages 31a and the charge line 33 and between at least one of the pair of second oil passages 31b and the charge line 33. Bypass line 62a, 62
b is formed (see FIGS. 1, 6 and 7).

The bypass lines 62a and 62b are for ensuring a stable neutral state of the hydraulic pumps 10a and 10b. That is, when the movable swash plates 14a, 14b of the hydraulic pumps 10a, 10b are slightly inclined from the neutral position, a pressure difference is generated between the pair of first hydraulic lines 140a and / or between the pair of second hydraulic lines 140b. Thereby, the hydraulic motors 130a and 130b rotate. Therefore, the movable swash plates 14a, 14b
If the neutral position is slightly deviated from the set position, the hydraulic motors 130a and 130b rotate against the user's will. On the other hand, as described above, when the bypass lines 62a and 62b are provided, the hydraulic lines 140a and 140b are connected via the bypass lines 62a and 62b.
Pressure oil leaks from the first hydraulic line 140a even when the movable swash plates 14a and 14b are to be in the neutral position and inclined due to a manufacturing error or the like.
And / or a pressure difference generated between the pair of second hydraulic lines 140b is effectively suppressed, and the hydraulic motors 120a,
0b can be effectively prevented from rotating.

The leakage of the pressure oil from the pair of hydraulic lines 140a and 140b by the bypass lines 62a and 62b is caused by the hydraulic pumps 10a and 10b and the hydraulic motor 120.
a, 120b, the bypass line is only provided between the charge line 33 and one of the pair of first oil passages 31a and one of the pair of second oil passages 31b. It is preferred to provide.

Further, preferably, as best shown in FIGS. 6 and 7, the check valves 61a, 61b, 61
Opening means 63 is provided for each of the first and second oil passages 31 and c and 61d.
1b can be forcibly communicated. By providing such an opening means 63, when the drive source 100 and the hydraulic pumps 10a and 10b are out of order and the vehicle needs to be forcibly moved by human power or the like (forced rotation of the wheels), it can be easily performed. The vehicle can be moved. That is, when the pair of first oil passages 31a and / or the pair of second oil passages 31b are closed, the hydraulic motor 12
When the wheels connected to the motors 0a and 120b are forcibly rotated, the rotation of the hydraulic motors 120a and 120b causes
A pressure difference is generated between the pair of first hydraulic lines 31a and between the pair of second hydraulic lines 31b, making it difficult to move the vehicle (rotate the wheels). On the other hand, if the opening means is provided, all the check valves 61a, 61b,
61c and 61d can be forcibly mechanically opened to allow communication between the pair of first oil passages 31a and between the pair of second oil passages 31b, thereby facilitating forced movement of the vehicle. It becomes possible.

By arranging all the opening means 63 on the same surface side of the center section 30 as shown in FIG. 4, a link mechanism linked to the opening means 63 can be easily constituted. Can be.

In this embodiment, a pair of first hydraulic lines 140a and a pair of second hydraulic lines 140
a charge pump 50 as an oil supply member for b.
Although the pressure oil is forcibly supplied to the charge suction port 34, the charge suction port 34 is connected to an oil tank without a charge pump, and a low pressure side line of a pair of hydraulic lines is provided. It is also possible to adopt a configuration in which the oil is naturally sucked when the oil pressure falls below a predetermined value.

As described above, in the tandem pump unit 1 according to the present embodiment, the first hydraulic pump 10a and the second hydraulic pump 10b are configured to be housed in the common housing 20, so that the first hydraulic pump 10a The cost can be reduced by reducing the number of parts as compared with the related art in which a dedicated housing is required for each of the second hydraulic pump 10b and the second hydraulic pump 10b.

Further, a single common housing 20 accommodating the first hydraulic pump 10a and the second hydraulic pump 10b.
By simply mounting the first hydraulic pump 10a to the vehicle, both the first hydraulic pump 10a and the second hydraulic pump 10b can be installed in the vehicle, so that the efficiency of assembling the vehicle can be improved.

Further, the common housing 20 is provided with the first hydraulic pump 10 on one side and the other side in the axial direction of the pump.
a and second insertable first and second hydraulic pumps 10b
It has openings 20a and 20b, and has a bearing wall 20c between the first and second openings 20a and 20b for bearing-supporting a connecting portion of the first pump shaft 11a and the second pump shaft 11b. The first center section 3 having the first opening 20a and the second opening 20b respectively supporting the first hydraulic pump 10a and the second hydraulic pump 10b
0a and the second center section 30b, so that the first hydraulic pump 10a and the second hydraulic pump 10b can be closed by the first center section 30a, respectively.
And after being supported by the second center section 30b,
The first hydraulic pump 10a and the second hydraulic pump 10b can be housed in the common housing 20 from one side and the other side of the pump shaft, respectively. Therefore, the efficiency of assembling the tandem pump unit can be improved.
Further, one or both hydraulic pumps can be easily removed while the casing 20 is attached to the vehicle. Therefore, work efficiency at the time of maintenance or the like can be improved.

Further, the first center section 30a and the second center section 30b are connected to the common housing 20.
Are arranged so that the center section is not located between the first hydraulic pump 10a and the second hydraulic pump 10b, so that the connecting portion of the first pump shaft 11a and the second pump shaft 11b is provided. , The degree of freedom in design can be improved. That is, when the center section is disposed between the first hydraulic pump and the second hydraulic pump, the first pump shaft and the second pump shaft are connected so as not to interfere with the oil passage formed in the center section. It is necessary to connect them, and this may impair the degree of freedom of design and possibly increase the size of the pump unit itself. However, this inconvenience does not occur in the present embodiment.

In the present embodiment, the movable swash plate of the first hydraulic pump 10a and the second hydraulic pump 10b is a trunnion type. However, the present invention is naturally applicable to a cradle type movable swash plate. It is. 8 and 9 are a vertical front view and a vertical side view of a tandem pump unit according to the present invention including a hydraulic pump having a cradle type movable swash plate.

As shown in FIG. 9, in the case of a hydraulic pump having a cradle type movable swash plate, a bearing wall 20c 'is provided.
The piston unit 1 of the cradle type movable swash plate is provided on the surface facing the hydraulic pumps 10a 'and 10b'.
Convex arc surface 1 on the side (rear side) away from 2a, 12b
8, a concave arc surface 20e corresponding to 8 can be formed,
As a result, the convex arc surfaces 18 of the movable swash plates 14a and 14b
Can be guided stably. Therefore, the positions of the movable swash plates 14a and 14b can be set stably.

Further, in the present embodiment, the outer peripheral surface of the coupling joint 16 externally non-rotatably mounted on the coupling portion between the first pump shaft 11a and the second pump shaft 11b, and a bearing formed on the bearing wall 20c. A bearing member 17 is interposed between the first pump shaft 1 and the inner peripheral surface of the hole 20d.
Although the connecting portion between the first pump shaft 11a and the second pump shaft 11b is connected so as to be relatively non-rotatable about the axis, the bearing can be supported. However, as shown in FIG.
It is also possible to interpose bearing members 17 between the outer peripheral surface of the pump shaft 11b and the bearing hole 20d.

Further, in the present embodiment, the bearing wall 20c is formed integrally with the housing 20, but may be separately mounted on the housing 20 instead.

[0044]

According to the tandem pump unit of the present invention, there is provided a tandem pump unit used for a vehicle in which first and second hydraulic motors are respectively connected to left and right driving wheels, wherein the first and second hydraulic motors are connected to each other. First and second hydraulic pumps connected to each of the second hydraulic motors via a pair of first hydraulic lines and a pair of second hydraulic lines are integrally provided. In a tandem pump unit in which respective pump shafts are coaxially connected in series, a common housing for accommodating the first and second hydraulic pumps, and first and second centers for supporting the first and second hydraulic pumps, respectively. Section, the first hydraulic pump and the second hydraulic pump each require a dedicated housing. Kadoka can be achieved. further,
Since only the single common housing in which the first hydraulic pump and the second hydraulic pump are housed is mounted on the vehicle, both the first hydraulic pump and the second hydraulic pump can be installed on the vehicle. Can also be improved.

The common housing has a first hydraulic pump and a second hydraulic pump on one side and the other side in the axial direction of the pump, respectively.
It has a first and a second opening into which the hydraulic pump can be inserted, and has a bearing between the first and the second opening for bearing-supporting a connecting portion between the first pump shaft and the second pump shaft. Each of the first opening and the second opening is a first opening.
The first and second hydraulic pumps can be closed by the first and second center sections respectively supporting the hydraulic pump and the second hydraulic pump, so that the first and second hydraulic pumps can be closed by the first and second center sections, respectively. , The first hydraulic pump and the second hydraulic pump can be housed in the common housing from one side and the other side of the pump shaft, respectively. Therefore, the assembling efficiency of the tandem pump unit can be improved. Further, one or both hydraulic pumps can be easily removed while the casing is attached to the vehicle. Therefore, work efficiency at the time of maintenance or the like can be improved.

Further, the first center section and the second center section
Arrange the center section on both ends of the common housing,
Since the center section is not located between the first hydraulic pump and the second hydraulic pump, it is possible to improve the degree of freedom in designing the connecting portion between the first pump shaft and the second pump shaft. .

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a vehicle to which an embodiment of a tandem pump unit according to the present invention is applied.

FIG. 2 is a vertical sectional side view of the tandem pump unit shown in FIG.

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

FIG. 4 is a sectional view taken along line BB in FIG. 3;

FIG. 5 is a sectional view taken along line CC in FIG. 4;

FIG. 6 is a sectional view taken along line DD in FIG. 3;

FIG. 7 is a sectional view taken along line EE in FIG. 3;

FIG. 8 is a partial longitudinal front view of another embodiment of the tandem pump unit according to the present invention.

FIG. 9 is a partial vertical sectional side view of the tandem pump unit shown in FIG. 8;

FIG. 10 is a cross-sectional view showing another embodiment of a connection portion between the first and second pump shafts.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pump unit 10a, 10b 1st hydraulic pump, 2nd hydraulic pump 11a, 11b 1st pump shaft, 2nd pump shaft 16 Connection joint 17 Bearing member 20 Common housing 20a, 20b 1st opening, 2nd opening 20c Bearing wall 20e Bearing holes 30a, 30b First center section, second center section 31a, 31b A pair of first oil passages, a pair of second oil passages 32a, 32b First suction / discharge port, second suction / discharge port 33 Charge line 120a , 120b First hydraulic motor, second hydraulic motor 130a, 130b Left and right drive wheels 140a, 140b First hydraulic line, second hydraulic line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D042 AA06 AB11 BA02 BA05 BA08 BA10 BB05 BC03 BC17 3H071 AA03 BB01 BB12 BB13 CC32 CC36 DD45 DD83

Claims (4)

[Claims] 1. A tandem pump unit for use in a vehicle in which first and second hydraulic motors are respectively connected to left and right drive wheels, wherein each of the first and second hydraulic motors and a pair of first and second hydraulic motors are provided. First and second hydraulic pumps connected via a hydraulic line and a pair of second hydraulic lines are integrally provided, and the pump shafts of the first and second hydraulic pumps are coaxially connected in series with each other. A tandem pump unit comprising: a common housing that houses the first and second hydraulic pumps; and first and second center sections that support the first and second hydraulic pumps, respectively, wherein the common housing A first and a second opening formed respectively at both ends in the axial direction of the pump shaft, into which a first and a second hydraulic pump can be inserted, and an intermediate portion between the first and the second opening. And the first and second center sections support the first and second pumps, respectively, while the first and second center sections support the first and second pumps, respectively.
The tandem pump unit is connected to the common housing so as to close an opening, and a connecting portion of each pump shaft of the first and second hydraulic pumps is supported by a bearing wall of the common housing. 2. The tandem pump unit according to claim 1, further comprising a connecting joint that is externally non-rotatably connected to a connecting portion between the pump shafts of the first and second hydraulic pumps. 3. The tandem pump unit according to claim 2, wherein the connection joint is rotatably supported by a bearing hole formed in the bearing wall via a bearing member. 4. The first and second pumps are variable displacement axial piston pumps having a cradle type movable swash plate, and the bearing wall has a surface facing the first and second hydraulic pumps. The tandem pump unit according to any one of claims 1 to 3, wherein a guide surface for slidably guiding the convex arc surface on the rear side of the movable swash plate is formed.