JP2970356B2 - Braking energy regeneration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator-type braking energy regenerating device used in automobiles and the like, and more particularly to a technique for smoothly stopping a vehicle while preventing generation of abnormal noise in a drive system at the end of braking. .

[0002]

2. Description of the Related Art Hitherto, a braking energy regenerating apparatus has been developed which is mounted on a vehicle such as a route bus and collects kinetic energy at the time of braking and uses it at the time of starting or accelerating. As the braking energy regenerating device, there are a flywheel type, a power generation type and the like.
The accumulator type described in Japanese Patent Publication No. 168 or the like has become mainstream in terms of performance and cost. This braking energy regenerating device is provided with a swash plate type hydraulic pump and the like via a low-pressure oil passage and a high-pressure oil passage to a hydraulic oil tank and an accumulator, respectively.
A motor (hereinafter simply referred to as a pump / motor) is connected. The pump / motor is connected to the power transmission system member via a dog clutch, and operates as a pump during braking of the vehicle to pump hydraulic oil in the hydraulic oil tank to the accumulator. Thereby, kinetic energy is converted into pressure energy and stored in the accumulator.
When the vehicle starts or accelerates, high-pressure hydraulic oil is supplied from the accumulator to the pump / motor, and the pump / motor is operated as a motor. As a result, the pressure energy is converted back to the kinetic energy, and the drive wheels of the vehicle are driven via the power transmission member.

In this type of braking energy regenerating device, when the pump / motor is operated with the pump during braking, the hydraulic pressure in the high-pressure oil passage becomes extremely high, so that when the brake is stopped or during normal running, the connection portion of the pipe or Hydraulic oil leaks from the seal of the pump / motor. The leaked hydraulic oil is once collected in a drain tank and then returned to the hydraulic oil tank by an electric pump or the like. However, when leaked, dust and the like are mixed into the hydraulic oil, and there is a problem that power consumption is increased. Therefore, in the conventional device, a shutoff valve acting as a check valve is attached to the accumulator, and the low-pressure oil passage and the high-pressure oil passage are connected by a bypass oil passage that bypasses the pump / motor. High-pressure hydraulic oil is discharged from the road to a low-pressure oil passage. Hydraulic oil is discharged by an electromagnetic unload valve provided in the bypass oil passage.For example, if the unload valve is opened immediately before the vehicle stops, the drive torque applied to the pump / motor suddenly disappears. Drive system backlash noise (so-called "sound") is generated. For this reason, the ECU opens the unload valve before the vehicle completely stops, for example, when the vehicle speed becomes equal to or lower than a predetermined value (for example, 1 km / H), thereby preventing generation of a noise.

[0004]

However, when the unloading valve is opened before the vehicle stops as described above, although the generation of a noise can be prevented, an appropriate braking force cannot be obtained. That is, when the unload valve is rapidly opened, the load on the pump / motor side is lost at that point, and the source of the braking force is only the service brake. Generally, during operation of the braking energy regeneration device, the driver does not depress the brake pedal with a large pedaling force, and the braking force of the service brake is also reduced in proportion thereto. Therefore, there is a possibility that the braking force becomes insufficient after the opening of the unload valve, and as shown in the graph of FIG. Note that the brake flow occurs in a range a in FIG. 4, and thereafter, the driver recognizes the brake flow and stops the vehicle by strongly depressing the brake pedal. Further, when the unload valve is suddenly opened, the hydraulic oil flows into the low-pressure oil passage from the bypass oil passage at a stretch, and there is a problem that abnormal noise is generated due to oil hammer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a braking energy regenerating apparatus capable of smoothly stopping a vehicle while preventing noise of a drive system at the end of braking.

[0006]

In order to achieve this object, according to the present invention, a hydraulic oil tank and an accumulator are connected via a low-pressure oil passage and a high-pressure oil passage, respectively. A hydraulic pump / motor coupled to the transmission system member via a clutch, and when braking the vehicle, operating the hydraulic pump / motor as a pump;
While the hydraulic oil in the hydraulic oil tank is pressurized and supplied to the accumulator for storage, when the vehicle starts or accelerates, the hydraulic pump / motor is operated as a motor to operate the high-pressure operation stored in the accumulator. In a braking energy regenerating device that uses oil as starting / acceleration energy, a vehicle speed detecting unit that detects a vehicle speed of the vehicle and the low-pressure oil passage and the high-pressure oil passage that bypass the hydraulic pump / motor. a bypass oil passage is disposed in the bypass oil passage, and the unloading valve to perform opening and blocking of the bypass oil passage, at the time of braking, the vehicle speed detected by the vehicle speed detecting means is equal to or less than a predetermined value In this case, there is provided an unload valve drive control means for duty-driving the unload valve.

[0007]

According to the present invention, when the vehicle is braked and decelerated to a predetermined vehicle speed, the unload valve drive control means duty-drives the unload valve at a predetermined duty ratio. Then, the working oil in the high-pressure oil passage is gradually discharged to the low-pressure oil passage, and accordingly, the load on the pump / motor gradually decreases. As a result, the braking force by the braking energy regenerating device is also gradually reduced, and the vehicle is smoothly stopped.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a braking energy regeneration device according to the present invention mounted on a large rear engine bus (hereinafter simply referred to as a bus) will be described below with reference to the drawings. As shown in FIG. 1, in the bus of the present embodiment, a through-shaft type differential unit 4 is connected via a propeller shaft 3 to the front ends of an engine 1 and a transmission 2 arranged vertically, and The driving force of the engine 1 is transmitted to the wheels 5.

A gear box 8 of a braking energy regenerating device 7 is connected to a front end of the differential unit 4 via a drive shaft 6. Then, when a differential carrier (that is, the drive wheel 5) (not shown) rotates in the differential unit 4, the speed increasing gears 9 and 10 built in the gear box 8 also rotate.
Further, a dog clutch 11 is built in the gear box 8, and the torque of the speed increasing gear 10 is transmitted to the swash plate type axial plunger type pump / motor 12 via the dog clutch 11.

The dog clutch 11 is driven and controlled by the ECU 13 to enter a connected or disconnected state. Moreover, Pont <br/>-up motor 12 also changes the tilting angle of the swash plate 14 with a built-biased to tilt cylinder which is driven and controlled to ECU 13 (not shown), function between pump and motor And the discharge amount is changed. The ECU 13 includes an accelerator sensor 15 for detecting an accelerator opening, a brake pressure sensor 16 for detecting a brake pressure, a vehicle speed sensor 17 for detecting a vehicle speed,
Various types of information are input from a pressure accumulation sensor 18 that detects the amount of accumulated pressure, a governor control unit 19 that controls the engine 1, and the like. The ECU 13 performs arithmetic processing on these pieces of information to determine the operation mode of the braking energy regeneration device 7, and controls the driving of the dog clutch 11, the pump / motor 12, and the like.

On the other hand, the pump / motor 12 is connected via a low-pressure pipe 20 and a high-pressure pipe 21 to a hydraulic oil tank 22 for storing hydraulic oil and a nitrogen gas-filled accumulator 23, respectively. An electromagnetic shutoff valve 24 is provided in the pipeline of the high-pressure pipe 21 adjacent to the accumulator 23. Normally, the shut-off valve 24 operates as a check valve that allows hydraulic oil to flow only from the pump / motor 12 side to the accumulator 23 side. However, when the ECU 13 is energized, the shut-off valve 24 also moves from the accumulator 23 side to the pump / motor 12 side. Distribute hydraulic oil.

The high-pressure pipe 21 is connected to the pump / motor 1
2 and a shut-off valve 24 are connected to a low-pressure pipe 20 via a bypass pipe 25 bypassing the pump / motor 12, and the pipe of the bypass pipe 25 has an electromagnetic ON / O
An FF type unload valve 26 is provided. The unload valve 26 is a normally-open type that closes when energized by the ECU 13, and communicates the high-pressure pipe 21 and the low-pressure pipe 20 via the bypass pipe 25 when deactivated. In FIG. 1, reference numeral 27 denotes a duty ratio adjustment volume provided in the ECU 13. By manually rotating the volume 27 forward and reverse, the drive duty ratio Dul when the unload valve 26 is duty-driven is set. It can be set to a desired value.

The operation of this embodiment will be described below. When a predetermined condition is satisfied at the time of braking, the ECU 13 puts the braking energy regenerating device 7 into the braking mode in order to convert the braking energy into the pressure energy. That is, the gear box 8
Gear 10 the dog clutch 11 of the driven and pump
The motor 12 is connected, and at the same time , the tilt angle of the swash plate 14 in the pump motor 12 is changed to function as a pump. Then, the differential carrier and the speed increasing gear 9,
10, the rotational force of the drive wheel 5 is transmitted ,
The motor 12 rotates. Thereby, the hydraulic oil tank 22
The hydraulic oil in the pump / motor 12
Is suctioned and pressurized, and is fed to the accumulator 23 through the high-pressure pipe 21. The pumped hydraulic oil is stored in the accumulator 23 and compresses the enclosed nitrogen gas.
The backflow is prevented by a shut-off valve 24 operating as a check valve.

On the other hand, when predetermined conditions are satisfied at the time of starting and accelerating, the ECU 13 sets the braking energy regenerating device 7 to the starting and accelerating mode in order to convert pressure energy into braking energy again. That is, the gear 10 and the pump / motor 12 are connected by the dog clutch 11, the tilt angle of the swash plate 14 is changed, the pump / motor 12 functions as a motor, and the shutoff valve 24 is further energized. Then, high-pressure hydraulic oil from the accumulator 23 is pumped from the high-pressure pipe 21 to drive the pump / motor 12. Pump / motor 1
The rotational force of No. 2 is transmitted to the driving wheels 5 via the speed increasing gears 9 and 10 and the differential carrier, and assists starting or accelerating, contrary to the braking force. Hydraulic oil pump
After driving the motor 12, it flows back to the hydraulic oil tank 22 via the low-pressure pipe 20.

Now, the braking energy regenerating device 7 of this embodiment
Then, at the end of braking, the hydraulic oil in the high pressure pipe 21 is
It is discharged to 0, and the procedure will be described below with reference to the flowchart of FIG. In this embodiment, when an ignition switch (not shown) is turned on, the unload valve drive control subroutine shown in FIG. 2 is executed at a predetermined control interval (for example, 50 ms). When the control is started, the ECU 13 first determines whether or not the braking energy regeneration device 7 is in the braking mode in step S1. This determination is affirmative (YES) when various conditions such as that the transmission 2 is not at the reverse position, that the dog clutch 11 is in the engaged state, and that the brake pressure is greater than a predetermined value are satisfied. move on.

In step S2, the ECU 13 determines whether the vehicle speed detected by the vehicle speed sensor 17 has fallen below a predetermined threshold (3 km / H in this embodiment). If this determination is negative (NO), step S3
Then, based on the detection results of the brake pressure sensor 15 and the pressure accumulation sensor 18, etc., the pump / motor 12
The tilt angle control value ELP of the proportional solenoid valve (not shown) for driving the swash plate 14 is set, and then the swash plate 14 is driven in step S4.

On the other hand, if the determination in step S2 is affirmative (YE
In S), the ECU 13 proceeds to step S5, sets the tilt angle control value ELP to 0, and outputs a drive signal to the proportional solenoid valve. With this drive signal, the pressure oil is gradually discharged from the tilt cylinder, the swash plate 14 becomes the neutral position, and the pump / motor 12 shifts to the non-operation mode. Next, the ECU 13
Goes to step S6, and turns off a two-port valve (not shown) for supplying pressure oil for driving the tilt cylinder.

Next, in step S7, the ECU 13 reads the set value for driving the unload valve set by the volume 27, and based on the read value, the unload valve 26
Is determined. In addition, volume 2
7 is individually adjusted at the time of vehicle manufacture or maintenance, etc., according to the loaded weight, the type of vehicle, etc., and the drive duty ratio Dul can be set to an optimum value that does not cause brake flow at the end of braking.

Next, in step S8, the ECU 13 duty-drives the unload valve 26 on the basis of the determined drive duty ratio Dul, and supplies high-pressure hydraulic oil in the high-pressure pipe 21 to the low-pressure pipe 20 through the bypass pipe 25. Discharge slowly to the side. Then, the hydraulic pressure acting on the pump / motor 12 gradually decreases, and accordingly, the pump / motor 12
The load on the side, that is, the braking force by the braking energy regeneration device 7 also decreases. As a result, as shown in the graph of FIG. 3, the deceleration of the vehicle gradually decreases, the vehicle speed gradually decreases, and the vehicle stops smoothly. The ECU 13 duty-drives the unload valve 26 until the vehicle stops or for a predetermined cycle (for example, 20 cycles). Thereafter, the ECU 13 deenergizes the unload valve 26 and fully opens the bypass pipe 25. . The predetermined cycle described above may be set to a value that does not cause abnormal noise in the drive system or oil hammer in the hydraulic piping.

On the other hand, if the determination in step S1 described above is negative (NO), that is, if the braking energy regenerating device 7 is not in the braking mode, this means that the brake pedal is once stopped during running and then the brake pedal is stopped. In Although,
The ECU 13 proceeds to step S5. And step S
5 to the pump / motor 12 through the procedure of step S8.
To the non-operation mode, and the unload valve 26
And the hydraulic oil in the high pressure pipe 21 is discharged to the low pressure pipe 20 side. Also in this case, since the hydraulic oil is gradually discharged, occurrence of an oil hammer in the hydraulic piping is prevented.

Although the description of the specific embodiment has been completed above, embodiments of the present invention are not limited to this embodiment. For example, in the above embodiment, the drive duty ratio is determined by the duty ratio adjustment volume. However, the drive duty ratio may be calculated and determined based on the detection result of a self-weight meter or the like. Further, the unload valve may not be driven at a constant drive duty ratio, but may be changed according to the detected value of the vehicle speed. Furthermore, ON / OF as unload valve
Instead of using the F type, a proportional solenoid valve or the like may be used. In this case, the opening of the unload valve may be gradually increased.

[0022]

In the braking energy recovery device of the present invention exhibits, when the vehicle speed during braking is equal to or less than a predetermined value, due to so as to duty drive the unloading valve, pump
The hydraulic pressure acting on the motor gradually decreases, and the load on the pump / motor side, that is, the braking force by the braking energy regenerating device also decreases accordingly. As a result, the noise of the drive system due to the rapid discharge of the hydraulic oil from the high-pressure oil passage is prevented, while the vehicle stops smoothly.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the entire structure of an embodiment of a braking energy regeneration device according to the present invention.

FIG. 2 is a flowchart showing an unload valve drive control subroutine.

FIG. 3 is a graph showing the relationship between deceleration, unload valve opening, and vehicle speed in the example.

FIG. 4 is a graph showing a relationship between a deceleration, an unload valve opening, and a vehicle speed in a conventional device.

[Explanation of symbols]

11 Dog Clutch 12 Pump / Motor 13 ECU 22 Hydraulic Oil Tank 23 Accumulator 24 Shutoff Valve 25 Bypass Circuit 26 Unload Valve 27 Volume

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B60K 25/00 B60T 1/10

Claims (1)

(57) [Claims] 1. A hydraulic oil tank and an accumulator are connected via a low-pressure oil passage and a high-pressure oil passage, respectively.
A hydraulic pump / motor connected to a power transmission system member of the vehicle via a clutch, and when braking the vehicle, the hydraulic pump / motor is operated as a pump to pressurize hydraulic oil in the hydraulic oil tank and A braking energy regenerating device that supplies the hydraulic fluid to an accumulator and stores it, while starting or accelerating the vehicle, operates the hydraulic pump / motor as a motor and uses the high-pressure hydraulic oil stored in the accumulator as starting and acceleration energy. , A vehicle speed detecting means for detecting a vehicle speed of the vehicle, a bypass oil passage bypassing the hydraulic pump / motor and communicating the low pressure oil passage and the high pressure oil passage, and a bypass oil passage provided in the bypass oil passage. the unloading valve to perform opening and blocking of the bypass oil passage, at the time of braking, the vehicle speed detected by the vehicle speed detecting means predetermined An unload valve drive control means for duty-driving the unload valve when the value becomes equal to or less than the value.