JP2015158099A - Industry vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industry vehicle capable of quickly increasing rotational speed on an engine at the time of lift speed up by using a pump for auxiliary machine.SOLUTION: An industry vehicle 1 includes a priority valve 33 which can be switched between a normal position for guiding an operational oil from an accessory pump 21 to an auxiliary machine 26 and a lift speed up position for guiding to a boom cylinder 24, and a control device 5 for controlling the priority valve 33. The control device 5, on the basis of a requested rotational speed of an engine, controls fuel jetting amount to an engine 12. The control device 5 decides a threshold value which is smaller than the requested rotational speed of an engine when a boom rising operation is performed, keeps the priority valve 33 at the normal position when an actual rotational speed of an engine is below the threshold value, and switches the priority valve 33 to the lift speed up position when the actual rotational speed of the engine exceeds the threshold value.

Description

  The present invention relates to an industrial vehicle such as a wheel loader.

  2. Description of the Related Art Conventionally, industrial vehicles are known that are used in a hydraulic drive system in which engine output is used for traveling and each part is driven. For example, Patent Document 1 discloses an industrial vehicle 100 as shown in FIG.

  In an industrial vehicle 100 shown in FIG. 9, an engine 101 is connected to four pumps of a wheel 114 and a hydraulic drive system 104 via an output distributor 102. A modulated clutch 110, a torque converter 111, a transmission 112, and an axle 113 are disposed between the wheel 114 and the output distributor 102.

  The hydraulic drive system 104 includes a loader pump 120, a switch pump 121, a steering pump 122, and an auxiliary machine pump 131. The loader pump 120 supplies hydraulic oil to the boom cylinder 128 and the bucket cylinder 129 via the main valve 123, and the steering pump 122 supplies hydraulic oil to the steering cylinder 130 via the load sensing valve 124. The auxiliary pump 131 supplies hydraulic oil to the auxiliary machine 132.

  The switch pump 121 is a pump for supplying hydraulic oil to any one of the boom cylinder 128, the bucket cylinder 129, and the steering cylinder 130. That is, the switch pump 121 is connected to the load sensing valve 124 via the first line 141, and the load sensing valve 124 is connected to the main valve 123 via the second line 142. The switch pump 121 assists the steering pump 122 during traveling, and assists the loader pump 120 during loading work. More specifically, the switch pump 121 supplies hydraulic oil to the boom cylinder 128 or the bucket cylinder 129 during the loading operation.

Japanese Patent No. 5044868

  In the industrial vehicle 100 shown in FIG. 9, as described above, the hydraulic oil from the switch pump 121 is supplied to the boom cylinder 128 during the loading operation. In other words, when the boom raising operation is performed, the boom raising speed is increased by the switch pump 121. Generally, increasing the boom raising speed is referred to as “lift acceleration”.

  By the way, it is desirable to omit the switch pump 121 from the viewpoint of reducing the number of pumps. In this regard, the auxiliary oil 132 can temporarily reduce the amount of hydraulic oil supplied. For this reason, it is conceivable to perform lift acceleration using the auxiliary pump 131. In this way, it is possible to increase the lift speed during traveling, which was not possible with the industrial vehicle 100 shown in FIG.

  However, when lift acceleration is performed using the auxiliary pump 131, there are the following problems. Since the load of the boom cylinder 128 is very large compared to the load of the auxiliary machine 132, when only the boom raising operation is performed, the required power of the loader pump 120 and the auxiliary machine pump 131 is increased. The engine speed decreases simultaneously with the operation. For this reason, the effect of lift acceleration cannot be obtained so much. Alternatively, when the boom raising operation is performed when the traveling speed is accelerated, the engine speed rises slowly and the acceleration performance is poor.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an industrial vehicle capable of rapidly increasing the engine speed when performing lift acceleration using an auxiliary pump.

  In order to solve the above problems, an industrial vehicle of the present invention includes an engine connected to a wheel, the number of rotations of which varies according to the amount of fuel injection, a main pump and an accessory pump driven by the engine, A boom cylinder that is supplied with hydraulic oil from the main pump to raise and lower the boom, an auxiliary machine that is supplied with hydraulic oil from the accessory pump, and a normal position that guides the hydraulic oil from the accessory pump to the auxiliary machine A priority valve that is switched between a lift acceleration position that leads to the boom cylinder, a rotational speed detector that detects the rotational speed of the engine, and a fuel injection amount to the engine based on the required engine rotational speed. A control device that controls the priority valve, and the control device performs a request engine when a boom raising operation is performed. A threshold value smaller than the engine speed is determined, and when the actual engine speed detected by the engine speed detector is lower than the threshold value, the priority valve is maintained at the normal position, and the actual engine speed is set to the threshold value. The priority valve is switched to the lift acceleration position when exceeding.

  According to the above configuration, lift acceleration is performed after the actual engine speed becomes sufficiently high. That is, the increase in the actual engine speed is prioritized over the lift acceleration. For this reason, an actual engine speed can be raised rapidly. For example, when only the boom raising operation is performed, only the required power of the main pump is initially increased. For this reason, a decrease in the actual engine speed at the same time as the boom raising operation is suppressed, and the actual engine speed can be quickly recovered to be close to the requested engine speed. Alternatively, when the boom raising operation is performed at the acceleration of the traveling speed, the actual engine speed can be raised smoothly.

  The control device may return the priority valve to the normal position when a predetermined lift acceleration permission condition is not satisfied after the priority valve is switched to the lift acceleration position. According to this configuration, it is possible to ensure safety and to effectively use the auxiliary machine.

  The control device stores, as the threshold value, a reference rotation speed for each of a plurality of rotation speed determination areas, and the control apparatus performs a reference rotation corresponding to the rotation speed determination area including the requested engine rotation speed. A number may be determined as the threshold. According to this configuration, the threshold value can be determined by simple selection.

  For example, the auxiliary machine may be a fan motor that cools a radiator for the engine.

  ADVANTAGE OF THE INVENTION According to this invention, when performing lift acceleration using the pump for auxiliary machines, an engine speed can be raised rapidly.

It is a figure which shows typically schematic structure of the industrial vehicle which concerns on one Embodiment of this invention. It is a block diagram of the electric control system in the industrial vehicle shown in FIG. It is a side view of the industrial vehicle shown in FIG. It is a flowchart of a lift acceleration operation. It is a graph which shows the relationship between a request | requirement engine speed and a threshold value. It is a graph which shows the relationship between an engine speed and torque when boom raising operation is performed simultaneously with depression of an accelerator pedal. It is a graph which shows a time-dependent change of an engine speed when boom raising operation is performed simultaneously with depression of an accelerator pedal. It is a graph which shows a time-dependent change of a boom angle when boom raising operation is performed simultaneously with depression of an accelerator pedal. It is a figure which shows typically schematic structure of the conventional industrial vehicle.

  FIG. 3 shows an industrial vehicle 1 according to an embodiment of the present invention, and FIG. 1 schematically shows a schematic configuration of the industrial vehicle 1. The industrial vehicle 1 shown in FIG. 3 is a wheel loader, but the present invention is also applicable to industrial vehicles such as excavator loaders and forklifts.

  As shown in FIG. 3, the industrial vehicle 1 includes a vehicle body 11 in which a front portion 11A and a rear portion 11B are coupled so as to be swingable in a horizontal direction. A front wheel 16 is attached to the front portion 11A, and a rear wheel 17 is attached to the rear portion 11B.

  A driver's cab 15 is provided in the rear portion 11B, and an engine 12 is mounted. The boom 13 is connected to the front portion 11A so as to be swingable in the vertical direction, and the bucket 14 is connected to the tip of the boom 13 so as to be swingable in the vertical direction. The front portion 11A, the boom 13 and the bucket 14 are driven by the hydraulic drive system 2 shown in FIG.

  As shown in FIG. 1, the engine 12 is connected to a front wheel 16 and a rear wheel 17 via a torque converter 18 and a transmission 19. In FIG. 1, illustration of a clutch, an axle, and the like is omitted. The engine 12 is also connected to the output distributor 20 in parallel with the torque converter 18.

  Fuel is injected into the engine 12 from a fuel injection valve (not shown), and the rotational speed of the engine 12 changes according to the fuel injection amount. The transmission 19 can change the speed ratio between the input shaft and the output shaft, and switches the rotation direction of the output shaft to the same direction as the input shaft or the reverse direction in order to switch the vehicle forward and backward. be able to.

  The fuel injection amount to the engine 12 is controlled by the control device 5 based on the required engine speed R. The control device 5 calculates the required engine speed R from the operation amount of an unillustrated accelerator pedal arranged in the cab 15. The operation amount of the accelerator pedal is detected by a pedal operation amount detector 62 shown in FIG.

  More specifically, the control device 5 is connected to a rotational speed detector 61 (see FIG. 2) that detects the rotational speed of the engine 12. Then, the control device 5 controls the fuel injection amount so that the actual engine speed N which is a detection value of the speed detector 61 becomes the required engine speed R.

  The hydraulic drive system 2 includes a main pump 21 and an accessory pump 22 connected to the output distributor 20. That is, the main pump 21 and the accessory pump 22 are driven by the engine 12. The hydraulic drive system 2 includes a pair of left and right steering cylinders 23 that swing the front portion 11A leftward and rightward with respect to the rear portion 11B, and a boom cylinder 24 that raises and lowers the boom 13. And a bucket cylinder 25 for changing the orientation of the bucket 14.

  The hydraulic oil is supplied to the steering cylinder 23 from the main pump 21 via the steering valve 31. The steering valve 31 is a flow rate control type valve, and a steering signal (pilot flow) is output from the steering signal output device 43 to the steering valve 31. The steering signal output device 43 is, for example, an orbit roll (registered trademark), and is connected by a steering wheel 41 and a steering shaft 42 disposed in the cab 15. Although illustration is omitted, a part of the hydraulic oil discharged from the main pump 21 is input to the steering signal output device 43.

  The hydraulic oil is supplied to the boom cylinder 24 and the bucket cylinder 25 from the main pump 21 via the control valve 32. The control valve 32 is a pressure control type valve. A pilot pressure is output from the boom operation valve 44 and a pilot pressure is output from the bucket operation valve 45 to the control valve 32. Each of the boom operation valve 44 and the bucket operation valve 45 includes a lever, and outputs a pilot pressure having a magnitude corresponding to the operation amount of the lever. The operation of tilting the lever of the boom operation valve 44 in the direction in which the boom 13 is raised is the boom raising operation.

  The accessory pump 22 supplies hydraulic oil to the fan motor 26 via the priority valve 33 and the fan drive system 34. The fan motor 26 is an example of the auxiliary machine of the present invention. The hydraulic oil from the accessory pump 22 is supplied to a brake valve (not shown) and is supplied as a primary pressure to the boom operation valve 44 and the bucket operation valve 45 described above.

  The fan motor 26 is for cooling a radiator (not shown) for the engine 12. The fan drive system 34 controls the amount of hydraulic oil supplied to the fan motor 26.

  The priority valve 33 is connected to the control valve 32 by a merging line 35. Note that the merging line 35 is not necessarily connected to the control valve 32, and may be connected to a supply line between the control valve 32 and the boom cylinder 24.

  The priority valve 33 is switched between a normal position for guiding hydraulic oil from the accessory pump 22 to the fan motor 26 via the fan drive system 34 and a lift speed increasing position for guiding the hydraulic oil to the boom cylinder 24 via the control valve 32. The priority valve 33 is controlled by the control device 5 described above. Specifically, the priority valve 33 is provided with a solenoid (not shown). When the energization of the solenoid is turned on or off by the control device 5, the priority valve 33 is moved from the normal position to the lift acceleration position. Can be switched to. At the time of lift acceleration, the priority valve 33 does not completely switch the circuit but guides only a part of the hydraulic oil from the accessory pump 22 to the cargo handling side. Thus, the priority valve 33 may guide the hydraulic oil from the accessory pump 22 to the boom cylinder 24 and the fan motor 26 at the lift acceleration position.

  As shown in FIG. 2, in addition to the rotation speed detector 61 and the pedal operation amount detector 62 described above, the control device 5 includes a boom raising pilot pressure sensor 71, a T / C hydraulic oil temperature sensor 73, a hydraulic oil temperature. A sensor 74 and a coolant temperature sensor 75 are electrically connected.

  The boom raising pilot pressure sensor 71 detects the pilot pressure output from the boom operation valve 44 to the control valve 32 during the boom raising operation, and also functions as a boom raising operation detector. The T / C hydraulic oil temperature sensor 73 detects the temperature of the hydraulic oil of the torque converter 18, and the hydraulic oil temperature sensor 74 detects the temperature of the hydraulic oil circulating in the hydraulic circuit of the hydraulic drive system 2. It is. The cooling water temperature sensor 75 detects the temperature of the cooling water radiated by the above-described unillustrated radiator.

  When the boom raising operation is performed, the control device 5 shifts to the lift speed increasing operation. FIG. 4 is a flowchart of the lift speed increasing operation. Here, “when the boom raising operation is performed” means that only an operation on the cargo handling side including the boom raising operation (for example, simultaneous operation of the boom raising and the bucket) is performed (that is, the requested engine speed is Or when the boom raising operation is performed simultaneously with the depression of the accelerator pedal (that is, when the required engine speed increases).

First, the control device 5 determines whether or not the lift acceleration permissible condition is satisfied (step S11). Here, “to satisfy the lift acceleration permissible condition” means to satisfy all of the plurality of individual conditions. In this embodiment, the following four are adopted as individual conditions.
First individual condition: The boom raising pilot pressure (detected value of the boom raising pilot pressure 71) output from the boom operation valve 44 to the control valve 32 is larger than a predetermined pressure (for example, 1.2 MPa).
Second individual condition: The temperature of the hydraulic oil of the torque converter 18 (the detected value of the T / C hydraulic oil temperature sensor 73) is lower than a predetermined temperature (for example, 105 ° C.).
Third individual condition: The temperature of the hydraulic oil circulating through the hydraulic circuit (the detection value of the hydraulic oil temperature sensor 74) is lower than a predetermined temperature (for example, 95 ° C.).
-4th individual condition: The temperature of the cooling water of the engine 12 (detection value of the cooling water temperature sensor 75) is smaller than predetermined temperature (for example, 95 degreeC).

  When the lift acceleration condition is not satisfied, in other words, when any of the above individual conditions is not satisfied (NO in step S11), the control device 5 proceeds to step S12, while keeping the priority valve 33 at the normal position. The determination in step S11 is repeated. As a result, lift acceleration may not be performed even when shifting to lift acceleration operation. Conversely, when the lift acceleration permissible condition is satisfied (YES in step S11), the control device 5 proceeds to step S13.

  By the way, during the lift acceleration operation, the control device 5 returns to step S11 after step S16 described later. Therefore, the lift acceleration permissible condition may vary depending on the state of the priority valve 33 at the time of proceeding to step S11, that is, whether the priority valve 33 is in the normal position or the lift acceleration position. This is to prevent the priority valve 33 once switched to the lift acceleration position from immediately returning to the normal position. For example, a first condition value that is a severe condition and a second condition value that is more relaxed than this may be set as the predetermined pressure and the predetermined temperature in the individual conditions.

  In step S <b> 13, the control device 5 determines a threshold value α that is smaller than the required engine speed R from the required engine speed R. There are various methods for determining the threshold value α. In the present embodiment, the threshold value α is determined as follows.

  As shown in FIG. 5, in the present embodiment, three rotation speed determination regions R1 to R3 are defined for the required engine rotation speed. For example, the lowest rotation speed determination region R1 is less than 1200 rpm, the intermediate rotation speed determination region R2 is 1200 rpm or more and less than 1600 rpm, and the highest rotation speed determination region R3 is 1600 rpm or more. The number of rotation speed determination areas may be two, or four or more.

  The control device 5 stores a reference rotation speed (V1 to V3) for each of the rotation speed determination regions R1 to R3 as a threshold value α. The reference rotation speed is a value smaller than the minimum rotation speed of the corresponding rotation speed determination area. For example, the reference rotational speed V1 corresponding to the lowest rotational speed determination region R1 is 900 rpm (usually, the requested engine rotational speed R is not 900 rpm or less), and the reference rotational speed V2 corresponding to the intermediate rotational speed determination region R2 is The reference rotation speed V3 corresponding to the highest rotation speed determination region R3 is 1500 rpm.

  In step S13, the control device 5 determines the reference rotational speed corresponding to the rotational speed determination area including the requested engine rotational speed R as the threshold value α.

  After determining the threshold value α, the control device 5 detects the actual engine speed N by the rotation speed detector 61 (step S14) and compares it with the threshold value α (step S15). If actual engine speed N is below threshold value α (NO in step S15), control device 5 proceeds to step S17. On the other hand, if the actual rotational speed N exceeds the threshold value α (YES in step S15), the control device 5 proceeds to step S16. In FIG. 4, when N = α, the process proceeds to step S17. However, when N = α, the process may proceed to step S16.

  In step S17, the priority valve 33 is maintained at the normal position. In step S16, the priority valve 33 is switched to the lift acceleration position. Thereafter, the control device 5 returns to step S11. Thereby, the process from step S11 to step S17 is repeated.

  Thereafter, when the operator interrupts the boom raising operation, the control device 5 ends the lift acceleration operation, and returns to the normal position if the priority valve 33 is in the lift acceleration position.

  In the control described above, even after the priority valve 33 is switched to the lift acceleration position, it is determined whether or not the lift acceleration permissible condition is satisfied in step S11. When the lift acceleration permissible condition is not satisfied, the priority valve 33 is returned to the normal position in step S12. With this configuration, safety can be ensured and the fan motor 26 can be used effectively.

  As described above, in the industrial vehicle 1 of the present embodiment, the lift acceleration is performed after the actual engine speed N becomes sufficiently high. That is, the increase in the actual engine speed N is prioritized over the lift acceleration. For this reason, the actual engine speed N can be rapidly increased. For example, when only the boom raising operation is performed, only the required power of the main pump 21 is initially increased. For this reason, a decrease in the actual engine speed N at the same time as the boom raising operation is suppressed, and the actual engine speed N can be quickly recovered to be close to the required engine speed R. Alternatively, when the boom raising operation is performed when the traveling speed is accelerated, the actual engine speed N can be smoothly raised.

  For example, when the boom raising operation is performed simultaneously with the depression of the accelerator pedal, the hydraulic oil from the accessory pump 22 is initially supplied to the fan motor 26. Thereby, the output of the engine 12 is preferentially used for acceleration of the traveling speed, and good acceleration can be obtained. After the actual engine speed N reaches the threshold value α, the hydraulic oil from the accessory pump 22 is supplied to the boom cylinder 24, so that the lift speed can be increased. Moreover, since the engine speed is sufficiently high at the time when the lift acceleration is started, even if the time when the lift acceleration is started is delayed from the time when the boom raising operation is started, a large flow rate is supplied from the accessory pump 22. This hydraulic oil is discharged, so that the delay can be recovered.

  Here, the above effect will be described in more detail with reference to FIG. The solid line in FIG. 6 indicates the load torque of the lift acceleration operation of the present embodiment, the broken line indicates the load torque when the priority valve 33 is switched from the beginning to the lift acceleration position, and the alternate long and short dash line indicates the engine 12 Indicates the output torque. The larger the difference between the output torque of the engine 12 and the load torque, the better the acceleration of the traveling speed.

  As shown in FIG. 6, the load torque of the lift acceleration operation of the present embodiment is the load torque when the priority valve 33 is switched from the beginning to the lift acceleration position before the priority valve 33 is switched to the lift acceleration position. It becomes much smaller than. Therefore, it can be seen that good acceleration can be obtained before the priority valve 33 is switched to the lift acceleration position. After the priority valve 33 is switched to the lift acceleration position, the load torque in the lift acceleration operation of the present embodiment is the same as the load torque when the priority valve 33 is switched from the beginning to the lift acceleration position. .

  Further, at high altitude, the output torque of the engine 12 decreases (the dashed line in FIG. 6 shifts downward), and the difference from the load torque decreases. Therefore, the control according to the present embodiment is particularly useful for the industrial vehicle 1 working at a high altitude.

  Further, FIG. 7 shows a change with time of the actual engine speed N, and FIG. 8 shows a change with time of the boom angle. 7 and 8, the solid line indicates the case of the lift acceleration operation of the present embodiment, and the broken line indicates the case where the priority valve 33 is switched from the beginning to the lift acceleration position (hereinafter referred to as a comparative example). From FIG. 7, it can be seen that according to the present embodiment, the engine speed can be increased more rapidly than in the comparative embodiment.

  By the way, as shown in FIG. 7, the actual engine speed N may slightly decrease immediately after the priority valve 33 is switched to the lift acceleration position. Therefore, in addition to the threshold value α, a second threshold value α ′ smaller than this is used, and after the priority valve 33 is once switched to the lift acceleration position, the actual engine speed N is set to the first engine speed instead of step S16. The priority valve 33 may be returned to the normal position when N ≦ α ′ as compared with the threshold value α ′ of 2. This configuration can also be adopted when only the boom raising operation is performed.

  Also, from FIG. 8, the temporal change in the boom angle is gentler in the present embodiment than in the comparative embodiment because lift acceleration is not initially performed. However, after the lift acceleration is started, the change with time of the boom angle of this embodiment immediately catches up with that of the comparative example. As described above, this is because a large amount of hydraulic fluid is discharged from the accessory pump 22 when the lift acceleration is started.

(Modification)
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, as a method for determining the threshold value α, the following method may be employed.

  The control device 5 may calculate the threshold value α by adding a coefficient smaller than 1 to the required engine speed R. Alternatively, the control device 5 may calculate the threshold value α by subtracting a certain value from the required engine speed R. However, if a plurality of reference rotation speeds are stored in advance in the control device 5 as in the above embodiment, the threshold value can be determined by simple selection.

  Moreover, the accessory pump 22 and the fan drive system 34 may be directly connected by a supply line, and the merge line 35 may branch from the supply line. In this case, the priority valve 33 may be an on-off valve provided in the merge line 35.

  The present invention can be applied to various industrial vehicles used in a hydraulic drive system that uses the output of an engine for traveling and raises a boom.

1 Work vehicle (wheel loader)
12 Engine 13 Boom 16, 17 Wheel 21 Main pump 22 Accessory pump 24 Boom cylinder 26 Fan motor (auxiliary machine)
33 Priority valve 5 Control device 61 Speed detector

Claims (4)

An engine connected to a wheel, the number of revolutions of which varies according to the fuel injection amount;
A main pump and an accessory pump driven by the engine;
A boom cylinder that is supplied with hydraulic oil from the main pump to raise and lower the boom;
An auxiliary machine to which hydraulic oil is supplied from the accessory pump;
A priority valve that is switched between a normal position for guiding hydraulic oil from the accessory pump to the auxiliary machine and a lift acceleration position for guiding the hydraulic oil to the boom cylinder;
A rotational speed detector for detecting the rotational speed of the engine;
A control device for controlling a fuel injection amount to the engine based on a required engine speed, and a control device for controlling the priority valve,
The control device determines a threshold value smaller than the required engine speed when a boom raising operation is performed, and sets the priority valve when the actual engine speed detected by the speed detector falls below the threshold value. An industrial vehicle that maintains the normal position and switches the priority valve to the lift acceleration position when the actual engine speed exceeds the threshold.   2. The industry according to claim 1, wherein after the priority valve is switched to the lift acceleration position, the control device returns the priority valve to the normal position when a predetermined lift acceleration permission condition is not satisfied. For vehicles.   The control device stores, as the threshold value, a reference rotation speed for each of a plurality of rotation speed determination areas, and the control apparatus performs a reference rotation corresponding to the rotation speed determination area including the requested engine rotation speed. The industrial vehicle according to claim 1, wherein a number is determined as the threshold value.   The industrial vehicle according to any one of claims 1 to 3, wherein the auxiliary machine is a fan motor that cools the radiator for the engine.

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