JPH0732992A - Braking energy regeneration device - Google Patents

Abstract

PURPOSE:To prevent the temperature of working oil from being excessively increased by interposing an oil cooler between a hydraulic pump motor and an accumulator. CONSTITUTION:Instead of making a braking energy regeneration device inoperative, working oil is cooled by an oil cooler 80 provided in the halfway of a pipe line 32 extended between a pump motor 10 and an accumulator 40, so that the temperature of hydraulic oil is prevented from being increased. When the motor of the braking energy regeneration device is operated as a vehicle is started or accelerated, hydraulic oil flows from the pump motor 10 to the accumulator 40 or reversely along the pipe line 32. During the period of the time, hydraulic oil passes through the oil cooler 80 disposed at the halfway of a pipe line 329 so as to be thereby cooled. As a result, an increase in oil temperature due to the operation of the pump motor can be prevented, and a deterioration of sealing due an excessive increase in oil temperature can thereby be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking energy regenerating device which utilizes braking energy accumulated during braking of a vehicle for starting the vehicle.

[0002]

2. Description of the Related Art Generally, braking of a vehicle is performed by converting kinetic energy of the vehicle into frictional energy. Therefore, energy is dissipated in the atmosphere during vehicle braking. 2. Description of the Related Art In recent years, as interest in global environmental problems such as air pollution has increased, a vehicle that reuses braking energy, such as a pressure-accumulation braking energy regenerative vehicle, has been proposed.

The braking energy regenerative device for a vehicle typically includes a hydraulic pump / motor and an accumulator, which has a piston and two chambers arranged on both sides of the piston. This type of device fills the other chamber of the accumulator by pumping it by driving the pump motor with the drive wheels of the vehicle to pump the hydraulic oil to one chamber of the accumulator when the vehicle is braking. The generated gas is compressed via the piston, and thereby the braking energy is stored. Then, when the vehicle starts, the compressed gas is expanded during vehicle braking to supply hydraulic oil from the accumulator to the hydraulic pump / motor to operate the pump / motor to drive the drive wheels of the vehicle. Reusing braking energy.

As described above, in the braking energy regeneration device, the working oil is used as the working medium for storing and releasing the braking energy, and the seals for preventing the leakage of the working oil are arranged in the respective parts of the device. There is. However, if the energy storage and discharge operations are repeated, the temperature of the hydraulic oil rises, and if the oil temperature rises excessively, the seal deteriorates. Therefore, before the oil temperature rises excessively, the hydraulic pump / motor is drivingly shut off from the drive system of the vehicle in order to stop the energy storage operation of the device.

[0005]

As described above, when the energy storage operation of the braking energy regenerator is stopped in order to prevent the deterioration of the seal caused by the increase in the oil temperature, the braking of the vehicle is stopped.
It will be done by the service brakes of the vehicle.
The oil temperature rise typically occurs at the time of a steep descending slope where hydraulic pressure accumulation is rapidly performed. Therefore, if the energy regeneration device is deactivated at this time, the load on the service brake becomes large. That is, the service brake temperature easily rises excessively, and the life of the brake line becomes short.

[0006] Therefore, an object of the present invention is to provide a braking energy regenerating device which prevents the hydraulic oil temperature from excessively rising.

[0007]

A hydraulic pump / motor connected to a drive system of a vehicle via a clutch converts braking energy into hydraulic energy and accumulates the hydraulic energy in an accumulator, and the accumulated energy also serves as a hydraulic pump / motor. The present invention is characterized in that an oil cooler is provided between a hydraulic pump / motor and an accumulator in a braking energy regenerative device that drives a vehicle and uses it as starting energy for a vehicle.

[0008] Preferably, the braking energy regenerator includes a first direct connection of the hydraulic pump / motor to the accumulator.
An oil passage, a second oil passage connecting a hydraulic pump / motor to an accumulator via an oil cooler, a switching valve for selectively switching between the first oil passage and the second oil passage, and an oil temperature of hydraulic oil is detected. When the oil temperature detecting means for performing the braking energy recovery detects that the oil temperature detected by the oil temperature detecting means exceeds a predetermined value, the hydraulic pump / motor and the accumulator are connected via the second oil passage. And a control means for operating the switching valve.

[0009] Preferably, the braking energy regenerator includes a first direct connection of the hydraulic pump / motor to the accumulator.
An oil passage, a second oil passage that connects a hydraulic pump / motor to an accumulator via an oil cooler, a switching valve that selectively switches between the first oil passage and the second oil passage, and a braking energy recovery for a predetermined time. When it is detected that the operation is continuously executed, the control means operates the switching valve so that the hydraulic pump / motor and the accumulator are connected via the second oil passage.

More preferably, the braking energy regenerator has a check valve provided between the oil cooler and the accumulator, which allows only the flow of the hydraulic oil from the oil cooler side to the accumulator side. The control means actuates the switching valve so that the hydraulic pump / motor and the accumulator are always connected via the first oil passage when the energy is released.

[0011]

[Operation] During operation of the braking energy regeneration device, the hydraulic pump
Hydraulic fluid flows between the motor and the accumulator. The hydraulic oil is cooled by an oil cooler provided between the pump / motor and the accumulator, and the hydraulic oil temperature is prevented from excessively rising. Therefore, it is not necessary to stop the operation of the braking energy regenerating device in order to prevent the deterioration of the seal caused by the increase in the oil temperature. In this way, since the braking function of the braking energy regenerating device is achieved, the load applied to the service brake is reduced.

According to a particular aspect of the present invention, if the oil temperature detected by the oil temperature detecting means does not reach a predetermined value, the pump / motor and the accumulator are directly connected by the switching valve operated under the control of the control means. The first oil passage to be connected is selected. In this case, the hydraulic oil flows between the pump / motor and the accumulator without passing through the oil cooler. That is,
Compared with the case where the oil is passed between the pump / motor and the accumulator via the oil cooler, the volume of the hydraulic oil flow path becomes smaller, and the output torque generated by the motor-operated pump / motor rapidly rises.

On the other hand, when the oil temperature reaches a predetermined value, the switching valve selects the second oil passage that connects the pump / motor and the accumulator via the oil cooler, and the operation that flows between the pump / motor and the accumulator. The oil flows through the oil cooler and is cooled at this time so that the oil temperature does not rise excessively. In another aspect, if the braking energy is not continuously collected for a predetermined period of time, the first value is set by the switching valve.
An oil passage is selected, which prevents a delay in pump / motor torque rise. On the other hand, when the braking energy is continuously collected for a predetermined time, the switching valve causes the second
An oil passage is selected, whereby the hydraulic oil is cooled by the oil cooler.

In the mode in which the check valve is provided between the oil cooler and the accumulator, the hydraulic oil pressurized by the pump / motor is cooled in the oil cooler when energy is accumulated if the oil temperature is equal to or higher than a predetermined value. Later it flows into the accumulator via the check valve and contributes to energy storage. On the other hand, when energy is released, that is, when the motor is operating,
The first oil passage is selected by the switching valve while blocking the inflow of the hydraulic oil from the accumulator to the oil cooler by the check valve, which prevents the rise of the pump / motor torque from rising even during the cooling of the hydraulic oil.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a vehicle equipped with a pressure-accumulation type braking energy regenerating apparatus according to a first embodiment of the present invention includes an engine 3 for driving drive wheels 1 via a transmission 2. . The braking energy regenerating device is a swash plate type variable displacement piston pump / motor 1 as a hydraulic pump / motor that operates a pump when the vehicle is braked to recover the braking energy, and also operates a motor when the recovered energy is reused.
0 and accumulator 40 for storing recovered energy
It has and.

The drive shaft 10a of the pump / motor 10 includes a gear box 22 and is connected to a drive system of the vehicle connected to the drive wheels 1 via a clutch 21 so that the drive shaft 10a can be freely connected and disconnected. Further, the pump / motor 10 includes a swash plate 10b fitted to the drive shaft 10a so as to be rotatable integrally therewith, and a swash plate 10b.
And a piston 10c that reciprocates in accordance with the rotation, and the pump / motor capacity is changed according to the angle of the swash plate 10b with respect to the drive shaft 10a, that is, the tilt angle.

As shown in FIG. 2, the tilt cylinder 11 for variably controlling the tilt angle includes a piston 11a connected to a swash plate 10b and chambers 11b defined on both sides of the piston 11a. 11c, the swash plate 10b is driven to the pump operating side when the pilot hydraulic pressure from the pilot hydraulic pressure source 12 is supplied to one chamber, for example, the chamber 11b, and the pilot hydraulic pressure is supplied to the other chamber, for example, the chamber 11c. The swash plate 10b is driven to the motor operating side.

The pilot oil pressure source 12 cooperates with the proportional solenoid valve 13 interposed between the pilot oil pressure source 12 and the tilt cylinder 11 to variably control the supply of the pilot oil pressure from the pilot oil pressure source 12 to the tilt cylinder 11. It constitutes a pilot pressure supply circuit. When one solenoid 13a of the proportional solenoid valve 13 is energized, an amount of pilot oil pressure according to the energization amount is supplied to the chamber 11b of the tilt cylinder 11 via the proportional solenoid valve 13, and the other solenoid 13 is supplied.
When the b is energized, the pilot hydraulic pressure is supplied to the chamber 11c, which causes the piston 11a of the tilt cylinder 11 to move.
The operating position, and thus the tilt angle of the swash plate 10b, are variably controlled.

Solenoids 13a, 13 of the proportional solenoid valve 13
The energization to b is stopped and the proportional solenoid valve 13 turns the spring 1
When the pilot pressure supply to the tilt cylinder 11 is cut off by taking the neutral position by the spring force of 3c and 13d, the piston 11a of the tilt cylinder 11 moves into the chambers 11b and 11b.
The springs 11d and 11e respectively arranged in c are set to the neutral position. When the piston 11a moves, the pilot oil in the tilt cylinder 11 is discharged through a pipe line (not shown). In FIG. 2, reference numerals 16, 17 and 18 represent relief valves, respectively.

As shown in FIGS. 1 and 2, the pump / motor 10 communicates with the hydraulic oil tank 30 via a pipe line 31 and with an accumulator 40 via a pipe line 32. A switching valve 50 is provided on the side of the accumulator 40 of the pipeline 32, and the switching valve 50 allows or blocks the flow of hydraulic oil between the pump / motor 10 and the accumulator 40.

More specifically, as shown in FIG. 3, a pipe line 3 connecting the pump / motor 10 and the accumulator 40.
The reference numeral 2 includes a high pressure hose 71 having one end connected to the pump / motor 10 and a conduit 72 having the other end of the hose 71 connected thereto. The conduit 72 is a frame of the vehicle (not shown)
It is provided on the manifold block 60 that is fixed to and is connected to the accumulator 40. A logic valve 51 is arranged in the middle of the pipe line 72, and the valve 51 cooperates with a poppet valve 52 fixed to a sub plate 61 fixed to the block 60 to form the above-mentioned switching valve 50.

The poppet valve 52 has a first port branched from the branch line 7 from the logic valve 51 side of the line 72.
3 and the second port communicates with the drain pipe 78 that communicates with the hydraulic oil tank 30. The first port is adapted to communicate with the control port of the logic valve 51 via the conduit 74 communicating with the third port of the poppet valve 52 when the solenoid 52a of the poppet valve 52 is deenergized. There is. That is, when the solenoid 52a is deenergized, the operating hydraulic pressure in the branch conduit 73 is applied to the control port of the logic valve 51 via the poppet valve 52 to close the logic valve 51.

Further, a half of the line 72 on the pump / motor side of the logic valve 51 is connected to the three-way switching valve 53 via lines 76 and 77. Switching valve 53
When the solenoid 53a of the
Is connected to the drain line 78 via the line 76 and the switching valve 53.
The pressurized hydraulic oil remaining in the high pressure hose 71 and in the half of the conduit 72 on the pump / motor side is returned to the tank 30, and when the solenoid 53a is energized, the conduits 76, 77 are communicated. They are connected to each other. The pump / motor-side end of the conduit 72 communicates with the drain conduit 78 via a valve 54 that opens when the hydraulic pressure applied to the input port exceeds a certain pressure.

As shown in FIG. 1, the accumulator 40
Has a hollow cylindrical accumulator body 41 and a piston 42 slidably arranged in the accumulator body 41. With respect to the piston 42, the first chamber 43 is defined by the inner surface of the accumulator body 41 and the end surface of the piston 42 on the switching valve 50 side, and the second chamber 44 is defined by the inner surface of the accumulator body and the piston end surface on the side opposite to the switching valve 50. Is defined. The second chamber 44 is filled with nitrogen gas.

In FIG. 1, reference numeral 4 represents a controller as a control means including a processor, a memory, an input / output circuit, etc. The controller 4 performs various conventionally known engine controls and works in conjunction with an accelerator pedal 5. The operations of the proportional solenoid valve 13, the switching valve 50, etc. are controlled in accordance with sensor outputs from various sensors including an accelerator pedal opening sensor and a brake sensor that responds to the operation of the brake pedal 6.

As described above, when the braking energy recovery and braking energy recovering and releasing operations are repeated and the operating oil temperature rises excessively, seals (not shown) arranged to prevent operating oil leakage are provided in various parts of the apparatus. It will deteriorate. In order to prevent this, the conventional braking energy regenerative device shuts off the pump / motor 10 from the drive system of the vehicle to prohibit the energy storage operation when the oil temperature rises.
However, if the braking action of the braking energy regenerating device is prohibited in this way, a load is added to the service brake of the vehicle during vehicle braking.

Therefore, in this embodiment, instead of deactivating the braking energy regenerator, the hydraulic oil is cooled by the oil cooler 80 provided in the middle of the pipe 32 extending between the pump / motor 10 and the accumulator 40. This prevents the oil temperature from rising. Hereinafter, the operation of the braking energy regenerating device having the above-described configuration will be described.

During the operation of the braking energy regeneration device, the controller 4 is performing the braking operation, the starting operation or the acceleration operation operation of the vehicle based on the outputs from various sensors such as the accelerator pedal opening sensor and the brake switch. Determine whether or not. If the vehicle is not being braked, started, or accelerated, it is determined that the vehicle is in a steady running state. During steady running of the vehicle, the solenoid 52a of the poppet valve 52 is deenergized under the control of the controller 4,
The hydraulic pressure in the branch line 73 communicating with the line 72 is applied to the control port of the logic valve 51 via the poppet valve 52 and the line 74. Although the same hydraulic pressure as the hydraulic pressure applied to the control port is applied to the hydraulic oil distribution port of the logic valve 51, the pressure receiving area on the same port side is smaller than that on the control port side. The switching valve 50) is closed. As a result, the flow of hydraulic oil between the pump / motor 10 and the accumulator 40 is blocked.

Further, the solenoid 53a of the direction switching valve 53 is deenergized so that the pressurized hydraulic oil in the high pressure hose 71 and in the pump / motor side half of the conduit 72 is transferred to the tank 30 via the drain conduit 78. By returning, the residual pressure in the hose and the pipeline is released. As a result, the pump / motor 1
0 does not operate the motor and the vehicle does not move carelessly.

Further, the solenoid 13 of the proportional solenoid valve 13
When the energization of a and 13b is stopped and the proportional solenoid valve 13 is in the neutral position, the supply of pilot hydraulic pressure to the tilt cylinder 11 via the solenoid valve is cut off, and the swash plate 10b of the pump / motor 10 is tilted. The pump / motor 10 is deactivated by setting it to the inoperative position such that the turning angle becomes zero.
Further, under the control of the controller 4, the electric power supply from the clutch drive unit 82 to the clutch 21 is cut off and the clutch 21
Is turned off, which causes the pump / motor drive shaft 1
0a is cut off from the drive system of the vehicle.

Therefore, during steady running of the vehicle, the braking energy regenerative vehicle operates in the same manner as a normal vehicle. When the brake switch is turned on while the vehicle is traveling, it is determined that the vehicle has been braked. During this vehicle braking,
Since the force acting on the hydraulic oil distribution port is larger than the force applied to the control port of the logic valve 51, the logic valve 51 (more generally, the switching valve 50) can be opened.
Therefore, the flow of hydraulic oil between the pump / motor 10 and the accumulator 40 is allowed.

At the same time, one solenoid of the proportional solenoid valve 13, for example, the solenoid 13a is energized under the control of the controller 4, and the pilot hydraulic pressure is supplied to the chamber 11b of the tilt cylinder 11 via the proportional solenoid valve 13. Then, the swash plate 10b of the pump / motor 10 is set to the pump operating position shown in FIG. Also, the clutch drive unit 8
Electric power is supplied from 2 to the clutch 21 to bring the clutch 21 into a contact state, and the pump / motor drive shaft 10a is connected to the drive system of the vehicle.

As a result, the pump / motor 1 is connected to the drive wheel 1 via the clutch 21 and the gear box 22.
0 is driven by the drive wheel 1 to operate the pump, and the regenerative brake works. That is, the hydraulic oil from the tank 30 is
As indicated by the middle arrow, the pump / motor 10 causes the first chamber 43 of the accumulator 40 to pass through the conduit 32 (FIG. 1) including the high-pressure hose 71 and the conduit 72 (FIG. 2) including the logic valve 51. The nitrogen gas that has been pumped into the inside and filled in the second chamber 44 of the accumulator 40 is compressed. As a result, the kinetic energy of the vehicle is stored in the accumulator 40.

When the vehicle is started, that is, when the start operation by the driver is detected based on the outputs of various sensors representing the truss transmission gear position, the clutch pedal depression amount, the accelerator pedal opening, etc., the controller 4 opens the switching valve 50. , The solenoid 13b of the proportional solenoid valve 13 is energized, whereby the pilot hydraulic pressure is supplied to the chamber 11c of the tilt cylinder 11 via the proportional solenoid valve 13 and the swash plate 10b of the pump / motor 10 is moved to the position shown in FIG. It is set to a motor operating position that tilts to the side opposite to the side shown. or,
The controller 4 drives and controls the clutch drive unit 82 so that the clutch 21 is in a contact state.

As described above, when the switching valve 50 (logic valve 51) is opened, the nitrogen gas expands in the second chamber 44 of the accumulator 40, and the working oil in the first chamber 43 is accumulated by the piston 42 in the accumulator. It is discharged from the pump 40 and is pressure-fed to the pump / motor 10 through the pipe 32 including the conduit 72 including the logic valve 51 and the high pressure hose 71, and the pump / motor 10 operates to generate torque. The output torque of the pump / motor 10 is transmitted to the drive wheels 1 via the clutch 21 and the gear box 22 to drive the drive wheels 1.

When the vehicle is accelerated, that is, when the driver depresses the accelerator pedal, the pump / motor 10 starts to operate under the control of the controller 4 under a medium load of the engine 3 or more, similarly to when the vehicle starts. , Torque assist the engine 3. When the braking, starting or accelerating operation of the vehicle ends, the controller 4 causes the switching valve 50
And the solenoids 13a, 1 of the proportional solenoid valve 13 are closed.
The power supply to 3b is stopped, the pump / motor 10 is deactivated, and the clutch 21 is disengaged.

As described above, during the pump operation of the braking energy regeneration device associated with the braking operation of the vehicle and the motor operation of the braking energy regeneration device associated with the vehicle starting or acceleration operation, the hydraulic oil is the pump / motor. 10 to the accumulator 40 or vice versa.
Flowing along. During this time, the hydraulic oil passes through the oil cooler 80 arranged in the middle of the pipeline 32 and is cooled at this time. As a result, the oil temperature rise due to the operation of the pump / motor 10 is prevented, which prevents the seal deterioration due to the excessive rise of the oil temperature.

Unlike the conventional device, according to the braking energy regeneration device of the present embodiment, it is not necessary to prohibit the operation of the device from the viewpoint of preventing the oil temperature from excessively rising, and the braking action of the braking energy regeneration device is exerted during vehicle braking. Played. Therefore, the service brake of the vehicle is not overloaded, and the life of the brake lining can be extended. Hereinafter, a braking energy regeneration device according to a second embodiment of the present invention will be described with reference to FIG.

The apparatus of this embodiment is characterized in that the output torque of the pump / motor 10 can be quickly raised. In connection with this point, in the present embodiment, the pump / motor 10 and the accumulator 40 are directly connected to each other in addition to the conduit 32 as an oil passage connecting the pump / motor 10 and the accumulator 40 via the oil cooler 80. A pipeline 33 is provided as an oil passage to be connected, and one of the pipelines 32 and 33 is selected using a switching valve 34. The switching valve 34 is, for example, an electromagnetic switching valve, and its solenoid 34 a is connected to the controller 4.

The electromagnetic switching valve 34 is the solenoid 3
When the solenoid 4a is deenergized, the pump / motor 10 and the accumulator 40 are connected to each other via the oil cooler 80, and when the solenoid 34a is energized, the pump / motor 10 and the accumulator 40 are directly connected to each other. It takes a switching position to connect. In addition, the line 3 is provided between the oil cooler 80 and the accumulator 40.
2 is provided with a check valve 35. With this check valve 35,
Only the flow of hydraulic oil from the oil cooler 80 to the accumulator 40 is allowed.

Further, an oil temperature sensor 81 for detecting the actual temperature of the hydraulic oil is attached to the accumulator body 41, and the oil temperature sensor 81 is connected to the controller 4 so that the actual oil temperature data can be supplied to the controller 4. ing. The rest of the configuration and the basic operation of the device of this embodiment are the same as those of the above-mentioned first embodiment, and therefore a further description of the structure and part of the operation will be omitted.

The operation of the braking energy regenerating device having the above-mentioned structure will be described below. During operation of the braking energy regeneration device, the controller 4 periodically reads the output of the oil temperature sensor 81, which represents the actual temperature of the hydraulic oil as the working medium of the device. Then, every time the output of the oil temperature sensor is read, the controller 4 sets a predetermined value of the oil temperature, which is set in advance to a value equal to or smaller than the upper limit allowable value of the oil temperature.
Is read from the built-in memory, and the actual oil temperature is compared with a predetermined value.

When it is determined that the oil temperature is lower than the predetermined value,
The controller 4 determines that cooling of the hydraulic oil by the oil cooler 80 is unnecessary, and the solenoid 3 of the electromagnetic switching valve 34 is determined.
Energize 4a. As a result, the pump / motor 10 and the accumulator 40 are directly connected to each other via a part of the conduit 32 and the conduit 33, and the oil cooler 80 is not interposed between the elements 10 and 40.

Next, as in the case of the first embodiment, the controller 4 operates on the basis of the outputs from various sensors such as the accelerator pedal opening sensor and the brake switch to perform the braking operation, the starting operation or the acceleration operation operation of the vehicle. It is determined whether or not is performed, and each unit of the apparatus is controlled according to the determination result, as in the case of the first embodiment. That is, during steady running of the vehicle, under the control of the controller 4, the flow of hydraulic oil between the pump / motor 10 and the accumulator 40 is blocked, and the pump / motor drive shaft 10a is disconnected from the drive system of the vehicle. To be done.

When the vehicle is being braked, the pump / motor 1
0 and the accumulator 40 are allowed to flow through the hydraulic oil, the pump / motor drive shaft 10a is connected to the vehicle drive system, and the swash plate 10b of the pump / motor 10 is further connected.
Is set to the pump operating position. As a result, pump motor 10 pumps and braking energy is stored in accumulator 40. At this time, the oil cooler 80 is provided between the pump / motor 10 and the accumulator 40.
Therefore, the efficiency of collecting the braking energy is improved.

When the vehicle is starting or accelerating, braking energy is released from the accumulator 40 while the swash plate 10b is set at the motor operating position, the pump motor 10 operates as a motor, and the output torque of the pump motor 10 is increased. The drive wheel 1 is driven by. Since the oil cooler 80 does not exist between the accumulator 40 and the pump / motor 10, and therefore the volume of the hydraulic oil flow path is small, the output torque of the pump / motor 10 becomes smaller when the vehicle starts to start or accelerates. Get up quickly.

As described above, when the oil temperature does not reach the predetermined value, the pump / motor 10 and the accumulator 40 are connected through the conduit 33 to drive the respective parts of the device, and thereby the braking is performed. The energy recovery efficiency and the rising characteristics of the output torque of the pump / motor 10 at the time of releasing the braking energy are improved. On the other hand, when the oil temperature is equal to or higher than the predetermined value, the connection path between the pump / motor 10 and the accumulator 40 is selected according to the braking energy recovery or the braking energy release.

When it is determined that the oil temperature is equal to or higher than the predetermined value based on the output of the oil temperature sensor for this connection path selection, the controller 4 further determines whether or not the braking operation of the vehicle is being performed. When the vehicle is being braked, the controller 4 deactivates the solenoid 34a of the electromagnetic switching valve 34, judging that the cooling of the operating oil by the oil cooler 80 is required. As a result, the pump / motor 10 and the accumulator 40 are connected by the line 32, and the oil cooler 80 is interposed between the elements 10 and 40.

Therefore, when the vehicle is braked while the oil temperature is at or above the predetermined value, the hydraulic oil pressurized by the pump / motor 10 flows into the accumulator 40 after being cooled by the oil cooler 80. To do. This cooling of the hydraulic oil prevents a further increase in the oil temperature. On the other hand, if the vehicle is not being braked, the controller 4
Energizes the solenoid 34a of the electromagnetic switching valve 34 to connect the pump / motor 10 and the accumulator 40 by the conduit 33.

As a result, even if the oil temperature is higher than the predetermined value, when the vehicle is started or accelerated, the pressurized hydraulic oil in the accumulator 40 is oiled by the check valve 35. Since the inflow to the cooler 80 is blocked, the oil is directly supplied to the pump / motor 10 without passing through the oil cooler 80. Therefore, the output torque of the pump / motor 10 rises quickly when the vehicle starts to start or accelerates.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the second embodiment, the oil temperature sensor 81 is used to detect an increase in the oil temperature.
It is not essential to detect the oil temperature rise based on the detected oil temperature. For example, it may be determined that the oil temperature has risen when the braking energy recovery operation by the braking energy regeneration device is continuously executed for a predetermined time. In this case, for example, a timer (not shown) built in the controller 4 measures the execution time of one braking energy recovery operation or a plurality of braking energy recovery operations performed successively. Then, if the timed time is less than the predetermined time, the conduit 33 of FIG. 4 is selected as the hydraulic oil distribution path, and the pump / motor 10 and the accumulator 40 are directly connected. After that, when the timed time exceeds a predetermined time, the pipeline 3 is replaced with the pipeline 3
2 is selected as the hydraulic oil distribution path, and the hydraulic oil is cooled by the oil cooler 80 provided in the middle of the pipeline 32. According to this modification, the oil temperature sensor is unnecessary, and therefore the device configuration is simplified.

In the second embodiment, the accumulator 40 and the pump motor 10 are directly connected to each other when the braking energy is released when the oil temperature is equal to or higher than the predetermined value.
Although the rise characteristics of the motor output torque are improved, it is not essential to select the connection path between the accumulator and the pump / motor in this way. For example, when the oil temperature is equal to or higher than a predetermined value, the accumulator and the pump / motor may be kept connected via the oil cooler regardless of whether the braking energy is collected or released.

[0053]

As described above, the braking energy is converted into hydraulic energy by the hydraulic pump / motor connected to the drive system of the vehicle through the clutch and accumulated in the accumulator, and the accumulated energy is used by the hydraulic pump / motor. In the braking energy regeneration device that drives the motor and uses it as the starting energy of the vehicle, since the present invention provides the oil cooler between the hydraulic pump / motor and the accumulator, it is possible to prevent the operating oil temperature from excessively rising. . As a result, it is not necessary to deactivate the braking energy regeneration device in order to prevent the deterioration of the hydraulic oil leakage prevention seal due to the increase in the oil temperature,
Therefore, the braking action of the braking energy regenerator can always be made effective, so that an excessive load is not applied to the service brake of the vehicle, and the brake life is extended.

According to a particular aspect of the present invention, one of the first oil passage connecting the hydraulic pump / motor directly to the accumulator and the second oil passage connecting both through an oil cooler,
It is selected by the switching valve according to the detected oil temperature or the execution time of the braking energy recovery. According to this aspect, not only the oil cooler can be used to cool the hydraulic oil when the oil temperature rises, but when the oil temperature rise does not occur, the pump / motor and the accumulator are directly connected to each other, and the oil cooler is connected between them. Can be eliminated. For this reason, when the oil temperature does not rise, the volume of the hydraulic oil flow passage can be reduced, so that the braking energy recovery efficiency can be improved and the rising characteristics of the pump / motor output torque at the time of releasing the braking energy can be improved.

According to the preferred embodiment of the present invention, the check valve is provided between the oil cooler and the accumulator, and the pump / motor and the accumulator are directly connected to each other when the energy is released. Also, the rise delay of the pump / motor output torque at the time of releasing the braking energy can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of a braking energy regeneration device according to a first embodiment of the present invention together with peripheral elements.

FIG. 2 is a hydraulic circuit diagram showing the swash plate type variable displacement piston pump / motor of FIG.

FIG. 3 is a hydraulic circuit diagram showing the switching valve of FIG.

FIG. 4 is a view similar to FIG. 1, showing a braking energy regeneration device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive wheel 4 Controller (control means) 10 Swash plate type variable displacement piston pump / motor 21 Clutch 22 Gear box (vehicle drive system) 32, 33 Pipe line 34 Electromagnetic switching valve 35 Check valve 40 Accumulator 50 Switching valve 80 Oil cooler 81 Oil temperature sensor

Claims (4)

[Claims] 1. A hydraulic pump / motor connected to a drive system of a vehicle through a clutch converts braking energy into hydraulic energy and stores the hydraulic energy in an accumulator, and the accumulated energy drives the hydraulic pump / motor. A braking energy regeneration device for use as starting energy of a vehicle, wherein an oil cooler is provided between the hydraulic pump / motor and the accumulator. 2. A first oil passage directly connecting the hydraulic pump / motor to the accumulator, a second oil passage connecting the hydraulic pump / motor to the accumulator via the oil cooler, and the first oil. Switching valve for selectively switching between the oil passage and the second oil passage, oil temperature detecting means for detecting the oil temperature of the hydraulic oil, and oil temperature detected by the oil temperature detecting means at the time of braking energy recovery is a predetermined value or more. The control means for activating the switching valve so that the hydraulic pump / motor and the accumulator are connected via the second oil passage is detected. The braking energy regeneration device described. 3. A first oil passage for directly connecting the hydraulic pump / motor to the accumulator, a second oil passage for connecting the hydraulic pump / motor to the accumulator via the oil cooler, and the first oil. A switching valve for selectively switching between a passage and the second oil passage, and when it is detected that the braking energy is continuously collected for a predetermined time, the hydraulic pump / motor is connected via the second oil passage. The braking energy regeneration device according to claim 1, further comprising: a control unit that operates the switching valve so that the accumulator is connected. 4. A check valve is provided between the oil cooler and the accumulator, the check valve allowing only a flow of hydraulic oil from the oil cooler side to the accumulator side, and the control means always releases the energy when the energy is released. The braking energy regeneration device according to claim 2 or 3, wherein the switching valve is operated so that the hydraulic pump / motor and the accumulator are connected via one oil passage.